Co-reporter:Yu Song, Tianyu Liu, Bin Yao, Mingyang Li, Tianyi Kou, Zi-Hang Huang, Dong-Yang Feng, Fuxin Wang, Yexiang Tong, Xiao-Xia Liu, and Yat Li
ACS Energy Letters August 11, 2017 Volume 2(Issue 8) pp:1752-1752
Publication Date(Web):July 12, 2017
DOI:10.1021/acsenergylett.7b00405
Realizing fast charging–discharging for high mass loading pseudocapacitive materials has been a great challenge in the field of supercapacitors because of the sluggish electron and ion migration kinetics through the thick electrode materials. Here we demonstrate for the first time a facile hydrothermal treatment that can substantially enhance the rate capability of a highly loaded manganese oxide electrode via the Ostwald ripening process. Hydrothermal treatment improves not only the electrical conductivity of manganese oxide but also the ion diffusion rate in the thick oxide film. At slow scan rates below 40 mV s–1, the capacitance of the hydrothermally treated manganese oxide electrode increases linearly with mass loading (up to 23.5 mg cm–2) as expected for a capacitor under the non-diffusion-limited conditions. At high scan rates beyond 100 mV s–1, capacitive saturation is observed only at a high mass loading of ∼9 mg cm–2, which is significantly greater than the values reported for other manganese oxide electrodes. The electrode achieves an areal capacitance of 618 mF cm–2 at a high scan rate of 200 mV s–1, which is 3 times greater than that of the untreated sample. An asymmetric supercapacitor assembled with a hydrothermally treated manganese oxide cathode and a vanadium oxide/exfoliated carbon cloth anode can deliver a good volumetric energy density of 5 mWh cm–3. This value is 2–10 times greater than the values obtained from supercapacitors with comparable dimensions.
Co-reporter:Yin-Jian Ye;Ning Zhang
Journal of Materials Chemistry A 2017 vol. 5(Issue 46) pp:24208-24216
Publication Date(Web):2017/11/28
DOI:10.1039/C7TA06906E
The requirements for large-scale industrial electrolytic water splitting have motivated investigations of inexpensive and stable oxygen evolution catalysts which would provide high current densities (>500 mA cm−2) at low overpotentials. Herein we develop a scalable electrodeposition route to fabricate amorphous nickel–iron(oxy)hydroxide nanosheets directly onto a 3D partially exfoliated graphite foil electrode. The integrated electrode combines the high OER catalytic activity of NiFe-based materials and the excellent electric conductivity of the carbon substrate, while facile ion transport and gaseous product (O2) diffusion are guaranteed by its hierarchical structure. The electronic structure of the Ni catalytic center, which shows critical effects in determining the catalytic activity, can be controlled through Fe incorporation and/or tuning the electrodeposition potential window. The optimal electrode catalyzes the OER process with a low overpotential of 214 mV to reach 10 mA cm−2 current density in 1 M KOH. The Tafel slope is as small as 21 mV dec−1 so it is capable of delivering high current densities of 500 mA cm−2 at an overpotential of only 251 mV. The OER can be prolonged to 100 h at 10 mA cm−2 and 48 h at 500 mA cm−2. The composite shows great potential towards large-scale and long-term practical applications.
Co-reporter:Di Guo, Mingyue Zhang, Zhi Chen, Xiaoxia Liu
Materials Research Bulletin 2017 Volume 96, Part 4(Volume 96, Part 4) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.materresbull.2017.05.048
•PPy were decorated on Co3O4 nanowire surface via in-situ chemical polymerization.•Specific capacitance of 2122 F g−1at 5 mA cm−2 was obtained.•The synergistic effect effectively enhanced electrochemical performance.Hierarchical Co3O4@ polypyrrole (PPy) core-shell composite nanowires (NWs) were successfully fabricated by a template-free hydrothermal route combined with in-situ chemical polymerization. Based on the composition and morphology characterization, it is found that the well-aligned Co3O4 nanowires were uniformly coated with a thin layer of amorphous PPy. When directly used as an electrode material for supercapacitors, the Co3O4@PPy nanowire arrays exhibited high specific capacitance of 2122 F g−1 (3.18 Fcm−2) at 5 mA cm−2, which is much higher than that of the pristine Co3O4 nanowire arrays and improved cycling stability with 77.8% capacitance retention over 5000 cycles at 25 mA cm−2. The highly electronic conductive and electroactive PPy layer could significantly reduce charge transfer resistance and increase active sites. This synergistic strategy of the arrays structure and the PPy buffer layer can provide simple, efficient and versatile blue-prints for fabrication of Co3O4-based nanocomposites for extending its application for electrochemical energy storage.Download high-res image (190KB)Download full-size image
Co-reporter:Zhen Sun, Xiang Cai, Yu Song, Xiao-Xia Liu
Journal of Power Sources 2017 Volume 359(Volume 359) pp:
Publication Date(Web):15 August 2017
DOI:10.1016/j.jpowsour.2017.05.055
•Hierarchical honeycomb Fe3O4 was integrated on FEG via electrodeposition.•FEG/Fe3O4 shows high specific capacitances of 327 F g−1.•FEG/Fe3O4 exhibits excellent rate capability and durable cycling stability.•The assembled device showed a high energy density of 54 Wh kg−1.Research on anode materials with high capacitive performance is lagging behind that of cathode materials, which has severely hindered the development of high-efficient energy storage devices. Compared with other anode materials, Fe3O4 exhibits highly desirable advantages due to its low cost, high theoretical capacity and preferable electronic conductivity of ∼102 S cm−1. Herein, hierarchical honeycomb Fe3O4 is integrated on functionalized exfoliated graphite through electrochemical deposition and the following chemical conversion. The hierarchical honeycomb Fe3O4 is constructed by the oxide nanorods, which are assembled by a number of nanoparticles. This unique porous structure not only ensures fast ion diffusion in the electrode, but also provides large amount of active sites for electrochemical reactions. The exfoliated graphene atop the graphite base can act as 3D conductive scaffold to facilitate the electron transport of the electrode. Therefore, FEG/Fe3O4 exhibits large specific capacitances of 327 F g−1@1 A g−1 and 275 F g−1@10 A g−1. Good cycling stability is also achieved due to the flexibility of the graphene substrate. The assembled asymmetric device using FEG/Fe3O4 as anode can deliver a high energy density of 54 Wh kg−1.Download high-res image (359KB)Download full-size image
Co-reporter:Yin-Jian Ye, Zi-Hang Huang, Yu Song, Jin-Wang Geng, Xin-Xin Xu, Xiao-Xia Liu
Electrochimica Acta 2017 Volume 240(Volume 240) pp:
Publication Date(Web):20 June 2017
DOI:10.1016/j.electacta.2017.04.025
•PANI NWAs was electrochemically grown on surfaces of graphene sheets in Ex-GF.•PANI NWAs can be grown in solutions of aniline in a wide range of concentration.•The hierarchical nanostructured electrodes showed high rate capability.•High areal capacitance of 3.57 F cm−2 was achieved by the PANI NWAs.Direct electrochemical growth of polyaniline nanowire arrays (PANI NWAs) on surfaces of graphene sheets in partially exfoliated graphite foil (Ex-GF) was achieved through electropolymerization of aniline to fabricate hierarchical nanostructured pseudocapacitive electrodes. The PANI NWAs were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Due to the combined merits of PANI NWA and graphene sheets, the hierarchical nanostructured electrodes demonstrated high pseudocapacitive performances. More importantly, fast capacitance fading of pseudocapacitive materials upon mass loading increase can be suppressed by the novel structure, making it a good candidate for supercapacitor electrode with high areal capacitance. The PANI NWA with a high mass loading of 5.89 mg cm−2 showed an exceptionally high areal capacitance of 3.57 F cm−2 and a quite high specific capacitance 607 F g−1. 72.4% of the capacitance can be retained when the discharge current increase 10 times, demonstrating its high rate capability.Download high-res image (120KB)Download full-size image
Co-reporter:Zi-Hang Huang;Tian-Yu Liu;Yu Song;Yat Li
Nanoscale (2009-Present) 2017 vol. 9(Issue 35) pp:13119-13127
Publication Date(Web):2017/09/14
DOI:10.1039/C7NR04234E
Heteroatom-doped carbonaceous materials derived from polymers are emerging as a new class of promising supercapacitor electrodes. These electrodes have both electrical double layer capacitance (from carbon matrices) and pseudo-capacitance (from hetero-atoms). Balancing the electrical double layer capacitance and pseudo-capacitance is a key to achieve large capacitance at ultrafast current densities. Here we investigate the influence of pyrolysis temperature on capacitive performance of hetero-atom (oxygen and nitrogen) doped carbons derived from polypyrrole nanowire arrays. Structural and electrochemical characterization reveal that the concentration of hetero-atoms as well as the ratio of electrical double layer capacitance and pseudo-capacitance can be tuned by varying the pyrolysis temperature. In fact the hetero-atom doped carbon sample obtained at a relatively lower pyrolysis temperature (500 °C) exhibits the optimal capacitive performance. It yields an outstanding areal capacitance of 324 mF cm−2 at 1 mA cm−2 (141 F g−1@0.43 A g−1), and more importantly, retains an areal capacitance of 184.7 mF cm−2 (80.3 F g−1@43.5 A g−1) at an ultrahigh current density of 100 mA cm−2. An asymmetric supercapacitor consisting of hetero-atom doped carbon as an anode delivers a maximum volumetric energy density of 1.7 mW h cm−3 at a volumetric power density of 0.014 W cm−3, which is among the best values reported for asymmetric supercapacitors.
Co-reporter:Yuan Jia;Xinxin Xu;Jinzhao Ou;Xiaoxia Liu;Fa-nian Shi
Inorganic Chemistry Frontiers 2017 vol. 4(Issue 8) pp:1344-1351
Publication Date(Web):2017/08/08
DOI:10.1039/C7QI00251C
Since the controlled release of drug molecules under external stimuli is an essential strategy for effective tumor therapy, herein a redox-responsive drug delivery system (Ag-SS-MC) has been fabricated successfully through the modification of disulfide bonds on coordination polymer derived mesoporous carbon nanoparticles (MC) with nanoscale Ag as the “cap”. In this drug delivery system, the Ag “caps” are fastened on a disulfide linker tightly, which blocks the pores of MC and impedes unexpected leakage of loaded doxorubicin (DOX). This drug delivery system exhibits a striking DOX loading property, with loading ratio as high as 20.6%. Ag-SS-MC remains stable under normal physiological conditions, but the loaded DOX begins to be released in the presence of a reducing agent, glutathione (GSH), which is caused by reductive breaking of disulfide bonds. MTT assays show that, after incubation with the human cervical cancer cell line (HeLa) for 24 h, the cytotoxicity of blank Ag-SS-MC carriers can almost be ignored. In contrast, under the same conditions, the DOX loaded drug carrier system possesses high antitumor activity. Ag-SS-MC exhibits superior drug loading, high extracellular stability, redox-responsive intracellular drug release and excellent biocompatibility; all these characteristics make it a promising drug delivery system for tumor therapy.
Co-reporter:Xiang Cai, Yu Song, Zhen Sun, Di Guo, Xiao-Xia Liu
Journal of Power Sources 2017 Volume 365(Volume 365) pp:
Publication Date(Web):15 October 2017
DOI:10.1016/j.jpowsour.2017.08.039
•Fabrication of graphite substrate with anchored graphene-like nanopetals.•Electrochemical growth of Co−Ni double hydroxide nanopetals.•79% capacitance retention upon 100 times current increase.•The assembled device can work with a high power density of 21.5 kW kg−1.In-situ growing of energy storage materials on graphene-based substrates/current collectors with low defect is a good way to boost electron transport and so enhance rate capability for the obtained electrode. Herein, high-quality graphene-like nanopetals are partially exfoliated from graphite foil (GF) through a facile and fast cathodic process. Three-dimensional porous structure is established for the afforded cathodically-exfoliated graphite foil (CEG), with many graphene-like nanopetals vertically anchoring on the graphite substrate. A hierarchical structure is constructed by the following electrochemical growth of Co−Ni double hydroxide nanopetals on the graphene atop CEG. The double hydroxide in the obtained electrode with the optimized Co2+/Ni2+ molar ratio, Co0.75Ni0.25(OH)2-CEG, displays much improved rate capability and so can deliver a high specific capacitance of 1460 F g−1 at an ultra-high current density of 100 A g−1. An asymmetric device is assembled by using Co0.75Ni0.25(OH)2-CEG as cathode, which demonstrates a high energy density of 31.6 Wh kg−1 at an ultra-high power density of 21.5 kW kg−1, showing the potential of the hierarchical composite electrode for high power application. The device also displays good stability, it can retain more than 90% of its capacitance after 10000 galvanostatic charge-discharge cycles.Download high-res image (248KB)Download full-size image
Co-reporter:Dong-Yang Feng, Yu Song, Zi-Hang Huang, Xin-Xin Xu, Xiao-Xia Liu
Journal of Power Sources 2016 Volume 324() pp:788-797
Publication Date(Web):30 August 2016
DOI:10.1016/j.jpowsour.2016.05.112
•Prepare functionalized carbon cloth (FCC) via one-step electrochemical method.•Improve PPy’s rate capability via establishing its interaction with FCC substrate.•Assemble ASC by using PPy on FCC and MnO2 nanosheets on CC as anode and cathode.•The ASC showed a high volumetric energy density of 0.80 mWh cm−3 at 12.85 mW cm−3.Rate capability of polypyrrole (PPy) was improved through additional doping by oxygen containing functional groups introduced in the substrate of functionalized carbon cloth (FCC). The PPy deposited on surfaces of carbon fibers in FCC displayed good rate capability, 70% of its capacitance (341.2 mF cm−2 at 1 mA cm−2) can be retained when the charge/discharge current density increased 20 times to 20 mA cm−2, while the PPy deposited on untreated carbon cloth (CC) could only retain 52% of its capacitance (308.7 mF cm−2 at 1 mA cm−2). PPy/FCC also displayed excellent cycling stability, 96% of its initial capacitance can be retained after 10,000 charge/discharge cycles. The asymmetric supercapacitor (ASC) assembled by using PPy/FCC as anode and crumpled MnO2 nanosheets electrochemically deposited on carbon cloth (MnO2/CC) as cathode also displayed good rate capability. When the charge/discharge current density increased 10 times from 1 to 10 mA cm−2, the ASC can retain 79% of its volumetric capacitance (from 1.78 to 1.41 F cm−3). The ASC demonstrated a high volumetric energy density of 0.80 mWh cm−3 at 12.85 mW cm−3. After 10,000 galvanostatic charge/discharge cycles, the ASC can retain 90.7% of its capacitance, demonstrating its good cycling stability.
Co-reporter:Yu Song;Tian-Yu Liu;Xin-Xin Xu;Dong-Yang Feng;Yat Li
Advanced Functional Materials 2015 Volume 25( Issue 29) pp:4626-4632
Publication Date(Web):
DOI:10.1002/adfm.201501709
Polypyrrole (PPy) is a promising pseudocapacitive material for supercapacitor electrodes. However, its poor cycling stability is the major hurdle for its practical applications. Here a two-prong strategy is demonstrated to stabilize PPy film by growing it on a functionalized partial-exfoliated graphite (FEG) substrate and doping it with β-naphthalene sulfonate anions (NS−). The PPy electrode achieves a remarkable capacitance retention rate of 97.5% after cycling between −0.8 and 0 V versus saturated calomel electrode for 10 000 cycles. Moreover, an asymmetric pseudocapacitor using the stabilized PPy film as anode also retains 97% of capacitance after 10 000 cycles, which is the best value reported for PPy-based supercapacitors. The exceptional stability of PPy electrode can be attributed to two factors: 1) the flexible nature of FEG substrate accommodates large volumetric deformation and 2) the presence of immobile NS− dopants suppresses the counterion drain effect during charge–discharge cycling.
Co-reporter:Yu Song, Dong-Yang Feng, Tian-Yu Liu, Yat Li and Xiao-Xia Liu
Nanoscale 2015 vol. 7(Issue 8) pp:3581-3587
Publication Date(Web):19 Jan 2015
DOI:10.1039/C4NR06559J
Here we demonstrate a controlled two-step partial exfoliation method to synthesize functionalized exfoliated graphite substrates. Ultrathin and functionalized graphene sheets anchoring on the graphite provide a large conductive surface area for loading pseudo-capacitive MnO2 nanosheets. The functionalized exfoliated graphite/MnO2 electrode achieved an excellent areal capacitance of 244 mF cm−2, corresponding to an estimated MnO2 based gravimetric capacitance of 1061 F g−1, which is just slightly lower than its theoretical value of 1110 F g−1. More importantly, the seamless integration of graphene sheets and the graphite substrate minimizes the contact resistance, and substantially improves the rate capability of pseudo-capacitive materials. The electrode retained 44.8% of its capacitance when the charging current density increased 50 times from 0.23 to 11.5 mA cm−2. This novel functionalized exfoliated graphite substrate serves as a promising supporting material that could address the relatively low electrical conductivity of various pseudo-capacitive materials, and increase the mass loading and rate capability of pseudo-capacitors.
Co-reporter:Yu Song, Xiang Cai, Xinxin Xu and Xiao-Xia Liu
Journal of Materials Chemistry A 2015 vol. 3(Issue 28) pp:14712-14720
Publication Date(Web):08 Jun 2015
DOI:10.1039/C5TA02810H
High-rate asymmetric supercapacitors (ASCs) made of abundant and low-cost electrode materials and operating in safe aqueous electrolytes can be attractive for electrochemical energy storage. Here, we design a new type of ASC by using pseudo-capacitive nanomaterials, Ni–Co double hydroxide (Ni–Co DH) nanosheets and polypyrrole (PPy) films, for the cathode and anode, respectively, which were integrated with a functionalized partially exfoliated graphite (FEG) current collector. Benefiting from the “super highway” for fast electron/ion transportation in hybrid systems, the as-prepared electrodes exhibit superior rate capability (2442 and 2039 F g−1 at 1 and 50 A g−1, with 83.5% retention for Ni–Co DH; 560 and 441 F g−1 at 1 and 50 A g−1, with 79% retention for PPy). The assembled ASC displays a high specific capacitance (261 F g−1 at 1 A g−1) and excellent rate capability; 77% of its initial capacitance can be retained when the current density increases 30 times from 1 to 30 A g−1. An energy density of 61.3 W h kg−1 can be achieved by the ASC at 0.65 kW kg−1. Even at an ultra-high power density of 19.5 kW kg−1, the ASC can still deliver a high energy density of 47.2 W h kg−1. Through careful control of charges which can be stored in the anode and cathode, the cycling stability of the ASC is much improved, and 91% capacitance retention can be achieved after 5000 charge/discharge cycles. These features demonstrate a new avenue for developing high-performance pseudo-capacitive electrodes and rational assembly strategies for high power/energy density charge storage devices with good cycling stability.
Co-reporter:Xinxin Xu, Xin Gao, Tingting Lu, Xiaoxia Liu and Xiuli Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 1) pp:198-206
Publication Date(Web):12 Nov 2014
DOI:10.1039/C4TA05071A
To improve the photocatalytic activity of a coordination-complex-modified polyoxometalate (CC/POM), a new type of hybrid material (abbreviated as PPy/CC/POMNR) was fabricated by the combination of its nanorod (CC/POMNR) and polypyrrole (PPy) via a facile in situ chemical oxidation polymerization process under the initiation of ammonium persulfate (APS). Under the irradiation of visible light, PPy/CC/POMNR exhibited higher photocatalytic activity compared to CC/POMNR, PPy, and their mechanically blended products formed on the degradation of Rhodamine B (RhB). Optical and electrochemical tests showed that the enhancement of photocatalytic performance can be attributed to the high separation efficiency of the photogenerated electrons and holes on the interface of CC/POMNBs and PPy, which results from the synergistic effect between them. Furthermore, the influence of the concentration ratio between pyrrole (Py) and APS on the morphology, conductivity, and photocatalytic properties of the PPy/CC/POMNR is discussed and the optimal condition to fabricate a hybrid material with high efficiency was determined. These results suggest that the hybrid of CC/POMNR and PPy would be a feasible strategy to enhance the photocatalytic activity of CC/POMNR.
Co-reporter:Zi-Hang Huang, Yu Song, Xin-Xin Xu, and Xiao-Xia Liu
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 45) pp:25506
Publication Date(Web):October 28, 2015
DOI:10.1021/acsami.5b08830
Highly aligned nanoarchitecture arrays directly grown on conducting substrates open up a new direction to accelerate Faradaic reactions for charge storage as well as address “dead volume” limitations for high-performance pseudocapacitor electrodes. Here we reported the electrochemical fabrication of well-ordered polypyrrole (PPy) nanowire arrays (NWAs) on surfaces of carbon fibers in an untreated carbon cloth to construct hierarchical structures constituted by the three-dimensional conductive carbon fiber skeleton and the atop well-ordered electroactive polymer nanowires. The morphologies, wetting behaviors, and charge-storage performances of the polymer were investigated by scanning electron microscopy, transmission electron microscopy, contact-angle measurement, cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The well-ordered PPy NWA electrode exhibited a high specific capacitance of 699 F/g at 1 A/g with excellent rate capability, and 92.4% and 81.5% of its capacitance could be retained at 10 and 20 A/g, respectively. An extremely high energy density of 164.07 Wh/kg could be achieved by the PPy NWAs at a power density of 0.65 kW/kg. It also displayed a quite high energy density of 133.79 Wh/kg at a high power density of 13 kW/kg. The assembled symmetric supercapacitor of PPy NWAs//PPy NWAs also exhibited excellent rate capability, and only 19% of its energy density decreased when the power density increased 20 times from 0.65 to 13 kW/kg.Keywords: electrochemical growth; nanowire arrays; polypyrrole; rate capability; supercapacitor
Co-reporter:Li-Jun Bian, Hai-Long He and Xiao-Xia Liu
RSC Advances 2015 vol. 5(Issue 92) pp:75374-75379
Publication Date(Web):18 Aug 2015
DOI:10.1039/C5RA12075F
A composite film of self-doped polyaniline and molybdenum oxide (SPAN/MoOx) was prepared through multi-potential steps, in which the working electrode was held alternately at −0.7 and 1.2 V. The as-prepared composite was characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrophotometry (FTIR). Its surface morphologies were investigated by scanning electron microscopy (SEM). The supercapacitive performance of the composite film was investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). The SPAN/MoOx displayed electroactivities in a large potential window from −0.8 to 1.0 V, showing the combined electroactivities of SPAN and MoOx in the composite. The SPAN/MoOx displayed a specific capacitance of 570 F g−1 at a current density of 1.7 A g−1, which is higher than those of similarly prepared SPAN (408 F g−1) and MoOx (100 F g−1). The symmetric supercapacitor assembled using SPAN/MoOx as both electrodes showed good rate behavior with an energy density of 35 W h kg−1 at a high power density of 4.7 kW kg−1.
Co-reporter:Dr. Xin-Xin Xu;Dr. Hong-Yu Yang;Dr. Zhen-Yu Li;Dr. Xiao-Xia Liu;Dr. Xiu-Li Wang
Chemistry - A European Journal 2015 Volume 21( Issue 9) pp:3821-3830
Publication Date(Web):
DOI:10.1002/chem.201405563
Abstract
To improve the photocatalytic properties of coordination polymers under irradiation in the visible-light region, coordination polymer nanobelts (CPNB) were loaded on functional carbon fiber (FCF) through the use of a simple colloidal blending process. The resulting coordination polymer nanobelt loaded functional carbon fiber composite material (CPNB/FCF) exhibited dramatically improved photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation. Optical and electrochemical methods illustrated the enhanced photocatalytic activity of CPNB/FCF originated from high separation efficiency of photogenerated electrons and holes on the interface of CPNB and FCF, which was produced by the synergy effect between them. In the composite material, the role of FCF could be described as photosensitizer and good electron transporter. For FCF, the number of functional groups on its surface has a significant influence on the photocatalytic performance of the resulting CPNB/FCF composite material, and an ideal FCF carrier was obtained as a highly efficient CPNB/FCF photocatalyst. CPNB/FCF showed outstanding stability during the degradation of rhodamine B (RhB); thus, the material is suitable for use as a photocatalyst in the treatment of organic dyes in water.
Co-reporter:Dr. Xinxin Xu;Dr. Tingting Lu;Dr. Xiaoxia Liu;Dr. Xiuli Wang
Chemistry - A European Journal 2015 Volume 21( Issue 41) pp:14638-14647
Publication Date(Web):
DOI:10.1002/chem.201501903
Abstract
A new p–n heterojunction photocatalyst has been synthesized successfully through chemical-bond-mediated combination of coordination polymer nanoplates (CPNPs) and partially reduced graphene oxide (PRGO) with a simple colloidal blending process. Photocatalytic H2 production by the p–n heterojunction photocatalyst PRGO/CPNP was investigated under visible-light irradiation, which illustrates that PRGO/CPNP exhibits a much higher photocatalytic H2 production rate than neat the CPNPs. The improvement of this photocatalytic property can be attributed to the inner electrical field formed in the p–n heterojunction, which impedes recombination of photogenerated electrons and holes. In PRGO/CPNP, the existence of the p–n heterojunction has been confirmed by electrochemical methods clearly. For PRGO/CPNP, the reductive degree of the PRGO has a great influence on the H2 production rate and an ideal condition to get a PRGO/CPNP photocatalyst with higher performance has been obtained.
Co-reporter:Dr. Xinxin Xu;Dr. Tingting Lu;Dr. Xiaoxia Liu;Dr. Xiuli Wang
Chemistry - A European Journal 2015 Volume 21( Issue 48) pp:17430-17436
Publication Date(Web):
DOI:10.1002/chem.201502703
Abstract
A visible-light-active p–n heterojunction photocatalyst has been synthesized by the enwrapping of poly[aniline-co-N-(4-sulfophenyl)aniline] (PAPSA) on a coordination polymer nanoparticle (NCP). Compared with the visible-light-inactive NCP, the new p–n heterojunction photocatalyst, PAPSA/NCP, exhibits a much higher efficiency in the reduction of CrVI under visible light. PAPSA performs two functions in this p–n heterojunction photocatalyst. First, as a visible-light-active material, it extends the photoresponse region of the photocatalyst from the ultraviolet to the visible-light region. Secondly, as a p-type semiconductor possessing suitable energy levels with respect to NCP, PAPSA forms a p–n heterojunction with the n-type NCP; the inner electric field of the p–n heterojunction accelerates the separation of electrons and holes, which enhances the photocatalytic efficiency. Furthermore, the p–n heterojunction photocatalyst exhibits outstanding stability during the photocatalytic reduction of CrVI.
Co-reporter:Ming-Hua Bai, Tian-Yu Liu, Feng Luan, Yat Li and Xiao-Xia Liu
Journal of Materials Chemistry A 2014 vol. 2(Issue 28) pp:10882-10888
Publication Date(Web):29 Jan 2014
DOI:10.1039/C3TA15391F
To meet the increasing demand for high energy density supercapacitors, it is crucial to develop positive and negative electrodes with comparable energy density. Previous studies have primarily focused on the development of positive electrodes, while negative electrodes are relatively less explored. Here we report an electro-codeposition method to synthesize a high performance negative electrode composed of a vanadium oxide (V2O5) and polyaniline (PANI) composite. Scanning electron microscopy revealed that the composite film is composed of one-dimensional polymer chains. Energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) confirmed successful incorporation of V2O5 into PANI chains. Significantly, the V2O5–PANI composite nanowires exhibited a wide potential window of 1.6 V (between −0.9 and 0.7 V vs. SCE) and a maximum specific capacitance of 443 F g−1 (664.5 mF cm−2). The flexible symmetric supercapacitor assembled with this composite film yielded a maximum energy density of 69.2 W h kg−1 at a power density of 720 W kg−1, and a maximum power density of 7200 W kg−1 at an energy density of 33.0 W h kg−1. These values are substantially higher than those of other pure V2O5 or PANI based supercapacitors. Moreover, the assembled symmetric supercapacitor device showed an excellent stability with 92% capacitance retention after 5000 cycles. The capability of synthesizing high performance composite electrodes using the electro-codeposition method could open up new opportunities for high energy density supercapacitors.
Co-reporter:Ming-Hua Bai, Li-Jun Bian, Yu Song, and Xiao-Xia Liu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 15) pp:12656
Publication Date(Web):July 10, 2014
DOI:10.1021/am502630g
Electrochemical codeposition of vanadium oxide (V2O5) and polypyrrole (PPy) is conducted from vanadyl sulfate (VOSO4) and pyrrole in their aqueous solution to get V2O5–PPy composite, during which one-dimensional growth of polypyrrole (PPy) is directed. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) are used to characterize the composite, while scanning electron microscopy (SEM) is used to investigate their morphologies. Cyclic voltammetry (CV), chronopotentiometry (CP) for galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS) are used to study electrochemical activities and pseudocapacitive properties of the composite. The influences of VOSO4 to pyrrole ratio in the electro-codeposition solution on morphologies and pseudocapacitive properties of the composite are discussed. Due to the organic–inorganic synergistic effect, V2O5–PPy composite exhibits good charge-storage properties in a large potential window from −1.4 to 0.6 V vs SCE, with a specific capacitance of 412 F/g at 4.5 mA/cm2. A model supercapacitor assembled by using the V2O5–PPy composite as the electrode materials displays a high operating voltage of 2 V and so a high energy density of 82 Wh/kg (at the power density of 800 W/kg).Keywords: electro-codeposition; polypyrrole; supercapacitor; vanadium oxide
Co-reporter:Yu Song, Jun-Li Xu, Xiao-Xia Liu
Journal of Power Sources 2014 Volume 249() pp:48-58
Publication Date(Web):1 March 2014
DOI:10.1016/j.jpowsour.2013.10.102
•Partial exfoliation of graphene is achieved by one-step electrochemical exfoliation.•Subsequent polypyrrole anchoring was conducted, offering new direction for developing graphene-based materials.•The obtained Ex-GF/PPy-NDS displays excellent pseudocapacitive properties in the potential window of −0.8 to 0.5 V vs. SCE.Partial exfoliation of graphene from graphite foil (GF) is achieved by a convenient one-step electrochemical exfoliation method to afford partially exfoliated graphene electrode (Ex-GF) with graphene sheets standing on GF matrix stably. Electropolymerization of pyrrole is carried out on Ex-GF with 1,5-naphthalene disulfonate (NDS) and 2-naphthalene sulfonate (NMS) as the ‘permanent’ doping anions to prepare Ex-GF/PPy-NDS and Ex-GF/PPy-NMS, respectively, in which the polymer is anchoring on the surfaces of graphene sheets. The PPy displays an opened structure due to the facilitated homogeneous nucleation on Ex-GF and so exhibits enhanced specific capacitance compared to the polymers deposited on pristine GF (to afford GF/PPy-NDS and GF/PPy-NMS). Specifically, Ex-GF/PPy-NDS film maintains 79% of its specific capacitance when the discharge current density increases from 1 to 20 A g−1. Moreover, discharge potential window of the polymer is enlarged to 1.3 V (from −0.8 to 0.5 V vs. SCE) due to the dual doping mode. Ex-GF/PPy-NDS film displays a high energy density of 82.4 Wh kg−1 at the power density of 650 W kg−1 and 65.1 Wh kg−1 at the power density of 13 kW kg−1. The cyclic charge/discharge stability of the polymer is also improved due to synergistic effect with partially exfoliated graphene.Partial exfoliation of graphene from graphite foil (GF) was achieved by a convenient one-step electrochemical exfoliation method to afford Ex-GF with graphene sheets standing on GF matrix stably. Dual doping polypyrrole was electrochemically anchored on the graphene sheets to afford Ex-GF/PPy-NDS, in which the polymer displayed superior energy storage properties in a wide potential window of −0.8 to 0.5 V vs. SCE.
Co-reporter:Xinxin Xu, Xin Gao, Zhongping Cui, Xiaoxia Liu and Xia Zhang
Dalton Transactions 2014 vol. 43(Issue 35) pp:13424-13433
Publication Date(Web):31 Jul 2014
DOI:10.1039/C4DT01279H
To improve the photocatalytic activity of a transition metal coordination polymer modified polyoxometalate (TMCP/POM), polypyrrole (PPy) was loaded on its surface through a facile in situ chemical oxidation polymerization process. Under the irradiation of visible light, the PPy loaded TMCP/POM composite material exhibited better photocatalytic activity than TMCP/POM, PPy and their mechanically blended products with respect to the degradation of Rhodamine B (RhB). Optical and electrochemical tests illustrated that the enhancement of photocatalytic activity can be attributed to the high separation efficiency of the photogenerated electron–hole pair on the interface of PPy and TMCP/POM, which originates from a synergy effect between them. Furthermore, the influence of reaction temperature on the morphology, wettability, conductivity and photocatalytic performance of the resulting composite material was discussed and an optical temperature to fabricate the photocatalyst with high efficiency has been obtained. These results suggest that the loading of PPy on the surface of TMCP/POM would be a feasible strategy to enhance its photocatalytic activity.
Co-reporter:Xin-Xin Xu, Zhong-Ping Cui, Xin Gao and Xiao-Xia Liu
Dalton Transactions 2014 vol. 43(Issue 23) pp:8805-8813
Publication Date(Web):11 Apr 2014
DOI:10.1039/C4DT00435C
To improve photocatalytic activity of a coordination polymer (CP) in the visible light region, five different transition metal ions (Fe3+, Cr3+, Ru3+, Co2+ and Ni2+) were introduced into its framework through an ion-exchange process. Among all the resulting transition metal ion doped coordination polymers (TMI/CPs), the one doped with Fe3+ took on the most excellent photocatalytic activity and the highest quantum yields in the visible light region, decomposing 94% Rhodamine B (RhB) in 8 hours. It can be attributed to the doping of Fe3+, which reduced the band gap (Eg) of the original CP, facilitating photocatalysis of the obtained polymer. Compared with the coordination polymer with Fe3+ as a dopant, products doped with other metal ions presented weaker photocatalytic activities in the visible light region, while under the irradiation of ultraviolet light, they showed favorable photocatalytic properties. The results suggest that to dope transition metal ions into the framework of CPs would be an ideal option for enhancing the photocatalytic activity of coordination polymers.
Co-reporter:Qing-Shan Liu, Zhi-Cheng Tan, Urs Welz-Biermann, Xiao-Xia Liu
The Journal of Chemical Thermodynamics 2014 Volume 68() pp:82-89
Publication Date(Web):January 2014
DOI:10.1016/j.jct.2013.08.024
Highlights•Targets of this research are hydrophobic series ionic liquids.•Molar heat capacities (Cp,m) were determined.•Influences of methylene on molar heat capacity were discussed.•Thermodynamic functions (HT − H298.15) and (ST − S298.15) were determined.Molar heat capacities (Cp,m) of the ionic liquids (ILs) N-alkylpyridinium hexafluorophosphate [Cnpy][PF6] (n = 2, 3, 5) were measured with a high-precision automated adiabatic calorimeter (AC). The melting temperatures were determined. The molar enthalpy and entropy of phase transition were calculated according to the data obtained of the molar heat capacities by the empirical equation. The polynomial equations of molar heat capacity as a function of the temperature were fitted before and after the phase transition for each IL compounds. The thermodynamic functions (HT − H298.15) and (ST − S298.15) were derived from the molar heat capacity values over the temperature range from (80 to 400) K with an interval of 5 K.
Co-reporter:Xinxin Xu, Zhongping Cui, Ji Qi and Xiaoxia Liu
Dalton Transactions 2013 vol. 42(Issue 37) pp:13546-13553
Publication Date(Web):30 Jul 2013
DOI:10.1039/C3DT51178B
To enhance the photocatalytic property of coordination polymers (CPs) in the visible light region, Ag loaded coordination polymer composite materials (Ag/CPs) were synthesized successfully through a photoreduction reaction of Ag+ on the surface of CPs. Photoluminescence (PL) was used to investigate the separation of photogenerated electron–hole pairs and the results illustrated Ag/CPs display higher quantum yields than CPs. This can be attributed to the strong interactions between Ag nanorods and coordination polymers, which lead to electron–hole pair separation between Ag nanorods and CPs. The degradation of Rhodamine B (RhB) was investigated to study the photocatalytic activities. Ag/CPs exhibited excellent photocatalytic activity in the UV and visible light region, while CPs can only decompose RhB under the irradiation of UV light. Furthermore, Ag/CPs showed outstanding stability during degradation of RhB.
Co-reporter:Xin-Xin Xu, Zhong-Ping Cui, Ji Qi and Xiao-Xia Liu
Dalton Transactions 2013 vol. 42(Issue 11) pp:4031-4039
Publication Date(Web):22 Jan 2013
DOI:10.1039/C2DT32636A
To improve the photocatalytic activity of a coordination polymer in the visible light region, polyaniline (PANI) was loaded onto its surface through a facile in situ chemical oxidation polymerization process. The resulting PANI loaded coordination polymer composite materials with excellent stability exhibit significantly higher photocatalytic activities than the pure coordination polymer photocatalyst on the degradation of methyl orange (MO) under visible light irradiation. This enhancement can be ascribed to the introduction of PANI on the surface of the coordination polymer, which leads to efficient separation of photogenerated electron–hole pairs as well as a significant expansion of the photoresponse region. Finally, we discussed the influence of acidity on the morphology and photocatalytic activity of the composite material. An optimal condition to obtain the PANI loaded coordination polymer composite material with excellent photocatalytic activity has been obtained.
Co-reporter:Qing-Shan Liu, Pei-Pei Li, Urs Welz-Biermann, Jian Chen, Xiao-Xia Liu
The Journal of Chemical Thermodynamics 2013 Volume 66() pp:88-94
Publication Date(Web):November 2013
DOI:10.1016/j.jct.2013.06.008
•Targets of this research are hydrophobic series ionic liquids.•Density, dynamic viscosity and electrical conductivity were determined.•Influences of methylene to properties were discussed.•Influences of methyl group on pyridinium ring position to properties were discussed.•Relationship of ρ, η and σ were described systematically.Air and water stable hydrophobic ionic liquids (ILs) were synthesized: N-propyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide [C33mpy][NTf2], N-hexyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide [C63mpy][NTf2], and N-hexyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide [C64mpy][NTf2]. Density, dynamic viscosity, and electrical conductivity of ILs were determined at atmospheric pressure in the temperature range of (278 to 353) K. The effects of methylene and methyl groups to density, dynamic viscosity, and electrical conductivity, respectively, were discussed. The thermal expansion coefficient, molecular volume, standard molar entropy, and lattice energy of the samples were estimated in terms of empirical and semi-empirical equations based on the density values. The temperature dependence on dynamic viscosity and electrical conductivity values of the ILs were discussed by Vogel–Fulcher–Tamman (VFT) and Arrhenius equations. The molar conductivities were calculated by density and electrical conductivity values.
Co-reporter:Qing-Shan Liu, Zhuo Li, Urs Welz-Biermann, Chang-Ping Li, and Xiao-Xia Liu
Journal of Chemical & Engineering Data 2013 Volume 58(Issue 1) pp:93-98
Publication Date(Web):December 20, 2012
DOI:10.1021/je301001g
Density, surface tension, dynamic viscosity, and electrical conductivity of a new air and water stable hydrophobic amide-based task-specific ionic liquid (IL) 1-butylamide-3-ethylimimdazolium bis(trifluoromethylsulfonyl)imide ([EimCH2CONHBu][NTf2]) were determined in the temperature range of T = (283 to 363) K. The volumetric and surface properties were discussed using the density and surface tension values. The thermal expansion coefficient was predicted by the interstice model theory. The decomposition temperature was determined with the thermogravimatric analysis (TG). The molar conductivity data were calculated by density and electrical conductivity values. Temperature dependence on dynamic viscosity and electrical conductivity values of the [EimCH2CONHBu][NTf2] were fitted by the VFT equation. The Arrhenius equation was also used to fit the dynamic viscosity and electrical conductivity values.
Co-reporter:Sha-Sha Liu, Li-Jun Bian, Feng Luan, Meng-Tao Sun, Xiao-Xia Liu
Synthetic Metals 2012 Volume 162(9–10) pp:862-867
Publication Date(Web):June 2012
DOI:10.1016/j.synthmet.2012.03.015
Geometry optimization was conducted on a series of emeraldine salt (ES) oligoanilines (2x + 2)-ES+ (x = 0, 1, 2, 3), alcohols and complexes composed of oligoanilines and alcohols by density functional theory (DFT) method at UB3LYP/6-31g (d) level. Electronic properties of complexes composed by (2x + 2)-ES+ oligoanilines with methanol, ethanol, propanol and isopropanol were investigated at higher level UB3LYP/6-311++g (d, p) to model the response of polyaniline (PANI) to alcohols. Influences of oligoaniline chain length and alcohols on the binding properties of the complexes were discussed based on the calculated results.Highlights► Geometry optimization was conducted on emeraldine salt oligoanilines, alcohols and complexes. ► Electronic properties of complexes were investigated to model response of polyaniline to alcohols. ► Influences of oligoaniline chain length and alcohols on properties of the complexes were discussed.
Co-reporter:Qing-Shan Liu, Pei-Pei Li, Urs Welz-Biermann, Xiao-Xia Liu, and Jian Chen
Journal of Chemical & Engineering Data 2012 Volume 57(Issue 11) pp:2999-3004
Publication Date(Web):October 31, 2012
DOI:10.1021/je3004645
Two air and water stable hydrophobic ionic liquids N-alkyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([Cn4mpy][NTf2], n = 2, 4) were synthesized and characterized. The density, electrical conductivity, and dynamic viscosity were measured and estimated in the range of T = (278.15 to 363.15) K. The melting temperature, glass transition temperature, and decomposition temperature of the two ILs were determined according to the differential scanning calorimetry (DSC) and thermogravimetric analyzer (TG). The molecular volume, standard molar entropy, and lattice energy were estimated in terms of empirical equations on the basis of the density values. The electrical conductivity and dynamic viscosity values dependence on temperature were fitted by the Vogel–Fulcher–Tamman equation. The molar conductivity was calculated by the density and electrical conductivity.
Co-reporter:Ben-Xue Zou, Ying Liang, Xiao-Xia Liu, Dermot Diamond, King-Tong Lau
Journal of Power Sources 2011 Volume 196(Issue 10) pp:4842-4848
Publication Date(Web):15 May 2011
DOI:10.1016/j.jpowsour.2011.01.073
Composite films of tungsten oxide (WO3) and polyaniline (PANI) have been electrodeposited by cyclic voltammetry in a mixed solution of aniline and precursor of tungsten oxide. Surface morphology and chemical composition of WO3/PANI composite are characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The influence of H2O2 on the electrodeposition of WO3/PANI composite film is also investigated. Cyclic voltammetry (CV), chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS) results show that WO3/PANI composite film exhibit good pseudocapacitive performance over a wide potential range of −0.5 to 0.7 V vs. SCE with the specific capacitance of 168 F g−1 at current density of 1.28 mA cm−2 and energy density of 33.6 Wh kg−1, which is 91% higher than that of similarly prepared PANI (17.6 Wh kg−1). An asymmetric model capacitor using WO3/PANI as negative and PANI as positive electrodes over voltage range of 1.2 V displays a specific capacitance of 48.6 F g−1 and energy density of 9.72 Wh kg−1 at the power density of 53 W kg−1, which is two times higher than that of a symmetric capacitor modeled by using two PANI films as both positive and negative electrodes.Research highlights► WO3 existed in small oxide particles through distribution in PANI to form WO3/PANI composite, resulting in the enhanced energy storage capabilities. ► The composite displayed pseudocapacitive properties over a broadened potential range of − 0.5 to 0.7 V vs. SCE. ► An asymmetric model capacitor using WO3/PANI and PANI as negative and positive electrodes, respectively displayed good pseudocapacitive behaviors over operating voltage of 1.2 V.
Co-reporter:Dr. Fanwu Zeng ; Zhenhua Sun;Xiaoguang Sang; Dermot Diamond; King Tong Lau; Xiaoxia Liu; Dang Sheng Su
ChemSusChem 2011 Volume 4( Issue 11) pp:1587-1591
Publication Date(Web):
DOI:10.1002/cssc.201100319
Co-reporter:Xin-Xin Xu;Xiao-Guang Sang;Xia Zhang
Journal of Chemical Crystallography 2011 Volume 41( Issue 4) pp:453-457
Publication Date(Web):2011 April
DOI:10.1007/s10870-010-9900-x
Two new coordination polymers [Cd(1,2′-cy)(btx)0.5H2O]n1 and {[Ni(1,2-cy)(2,2′-bipy)(H2O)2]·3H2O}n2 (1,2′-cy=4-cyclohexene-1,2-dicarboxylate, btx=1,4-bis(triazol-1-ylmethyl)benzene, 2,2′-bipy=2,2′-bipyridine) had been synthesized. Their structures were characterized by elemental analysis, IR, TG and X-ray single-crystal diffraction analysis. Crystal data for complex 1: Triclinic, space group P-1, a = 6.4303(13) Å, b = 10.399(2) Å, c = 11.713(2), α = 83.04(3)°, β = 81.87(3)°, γ = 83.84(3)°, and Z = 2. For complex 2: Orthorhombic, space group Pbcn, a = 15.613(3) Å, b = 13.970(3) Å, c = 21.290(4) Å, and Z = 4. Complex 1 exhibits an interesting two-dimensional wavelike covalent layer structure. When Ni salt was replaced by Cd salt, and reacts with 1,2′-cy and 2,2′-bipy, one-dimensional chain-like complex 2 was obtained. Furthermore, the fluorescent property of complex 1 was reported.
Co-reporter:Liang Chen, Li-Jie Sun, Feng Luan, Ying Liang, Yat Li, Xiao-Xia Liu
Journal of Power Sources 2010 Volume 195(Issue 11) pp:3742-3747
Publication Date(Web):1 June 2010
DOI:10.1016/j.jpowsour.2009.12.036
We report the synthesis and pseudocapacitive studies of a composite film (PANI-ND-MnO2) of polyaniline (PANI) and manganese oxide (MnO2) nanoparticles. To enhance the interaction of MnO2 and PANI, the surfaces of MnO2 nanoparticles were modified by a silane coupling reagent, triethoxysilylmethyl N-substituted aniline (ND42). The composite film was obtained via controlled electro-co-polymerization of aniline and N-substituted aniline grafted on surfaces of MnO2 nanoparticles (ND-MnO2) on a carbon cloth in a electrolyte of 0.5 M H2SO4 and 0.6 M (NaPO3)6. In comparison to similarly prepared PANI film, the incorporation of MnO2 nanoparticles substantially increases the effective surface area of the film by reducing the size of rod-like PANI aggregates and avoiding the entanglement of these PANI nanorods. Significantly, we observed significant enhancement of specific capacitance in PANI-ND-MnO2 film compared to PANI–MnO2 film prepared in a similar condition, indicating that the presence of the coupling reagent can improve the electrochemical performance of PANI composite film. A symmetric model capacitor has been fabricated by using two PANI-ND-MnO2 nanocomposite films as electrodes. The PANI-ND-MnO2 capacitor showed an average specific capacitance of ∼80 F g−1 and a stable coulombic efficiency of ∼98% over 1000 cycles. The results demonstrated that PANI-ND-MnO2 nanocomposites are promising materials for supercapacitor electrode and the importance of designing and manipulating the interaction between PANI and MnO2 for fundamentally improving capacitive properties.
Co-reporter:Ben-Xue Zou, Xiao-Xia Liu, Dermot Diamond, King-Tong Lau
Electrochimica Acta 2010 Volume 55(Issue 12) pp:3915-3920
Publication Date(Web):30 April 2010
DOI:10.1016/j.electacta.2010.02.034
Composite film of polyaniline (PANI) and tungsten oxide (WO3) was electrodeposited by cyclic voltammetric technique from a solution of aniline and tungstic acid. The obtained WO3/PANI film displayed a significant enhancement of electrocatalytic activity for iodate reduction and a better stability than that of pure WO3 and PANI films. Result of amperometric experiment revealed a good linear relationship with concentration of IO3− from 20 to 500 μM, with a high sensitivity of 0.54 μA/μM and a detection limit of 2.7 μM for the determination of iodate. This composite film was also successfully applied in determination of iodate in commercial table salt.
Co-reporter:Hai-Fei Jiang, Xiao-Xia Liu
Electrochimica Acta 2010 Volume 55(Issue 24) pp:7175-7181
Publication Date(Web):1 October 2010
DOI:10.1016/j.electacta.2010.07.056
One-dimensional growth of polyaniline (PANI) was conducted on carbon cloth through a pulse potentiostatic method. Hydrolysis of PANI was depressed, and the generated PANI film (PPM) displayed improved electroactivities. The specific capacitance of PPM was increased by 39% when compared to that of PANI film made by the conventional potentiostatic method (PM). The influences of the upper limit potential of the pulse potentiometry and the acidity of the polymerization solution on surface morphologies, electroactivities and conformation of the PANI films were studied by SEM, cyclic voltammetry, chronopotentiometry and UV–Vis spectrometry.
Co-reporter:Xinxin Xu, Xia Zhang, Xiaoxia Liu, Ting Sun and Enbo Wang
Crystal Growth & Design 2010 Volume 10(Issue 5) pp:2272
Publication Date(Web):April 9, 2010
DOI:10.1021/cg901605j
A unique three-dimensional metal−organic framework (MOF) [Cd4(1,10′-phen)(fum)(S-mal)(R-mal)(H2O)] (1) (1,10′-phen =1,10-phenanthroline, fum = fumarate dianion, mal = malate dianion) has been synthesized and characterized by single-crystal X-ray analysis. Under hydrothermal conditions, after a “three birds with one stone” in situ reaction process, maleic acid turns into fumarate dianion, isomeric R-malate dianion and S-malate dianion, which further connect with Cd atoms and form an octanuclear Cd cluster. The octanuclear Cd cluster links with neighboring clusters and constructs a rod-shaped secondary building unit (SBU). Neighboring rod-shaped SBUs are further connected by fumarate dianions and thus forms a three-dimensional network. To our interests, complex 1 exhibits interesting semiconductivity and fluorescence properties. When citraconic acid was used instead of maleic acid, a new complex [Cd2(mesac)2(1,10′-phen)2] (2) (mesac = mesaconate dianion) was synthesized under about the same reaction conditions. Complex 2 also exhibits fluorescence properties.
Co-reporter:Yu-Qian Dou, Yunpu Zhai, Fanwu Zeng, Xiao-Xia Liu, Bo Tu, Dongyuan Zhao
Journal of Colloid and Interface Science 2010 Volume 341(Issue 2) pp:353-358
Publication Date(Web):15 January 2010
DOI:10.1016/j.jcis.2009.09.015
Composite material PANI/KIT-6, with polyaniline (PANI) chains encapsulated in the 3-D interconnected pore channels of mesoporous silica, KIT-6, has been synthesized via a gas-phase method. The composite formation and the presence of PANI inside the pore channels of KIT-6 were evidenced by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), small-angle X-ray scatter (SAXS), transmission electron microscopy (TEM), and N2 adsorption–desorption isotherms. The PANI/KIT-6 composite showed good electrical conductivity (2.4 × 10−3 S/cm) due to the formation of 3-D networks of PANI inside the 3-D interconnected channels of KIT-6. The resistance of PANI/KIT-6 composite at different relative humidities (RH) was investigated. An essentially linear relationship between the relative resistance of the composite and the relative humidity of the environment was found from 11.3% to 97.3% RH.Polyaniline (PANI) was encapsulated into the 3-D interconnected pore channels of mesoporous silica, KIT-6. The composite showed enhanced electrical conductivity and potential applications in humidity sensors.
Co-reporter:Xinxin Xu, Xiaoxia Liu, Xia Zhang, Ting Sun
Solid State Sciences 2010 Volume 12(Issue 3) pp:355-360
Publication Date(Web):March 2010
DOI:10.1016/j.solidstatesciences.2009.11.013
Five new coordination polymers, [Cd(1,2′-cy)0.5(bix)H2O]n (1), [Cd2(1,2′-cy)2(1,10′-phen)2(H2O)2] (2), {[Co(1,2-cy)(2,2′-bipy)(H2O)2]·2H2O}n (3) {[Cd(succ)(1,10′-phen)H2O]·H2O}n (4), and {[Cd(succ)(2,2′-bipy)H2O]·2H2O}n (5) (1,2-cy = 4-cyclohexene-1,2-dicarboxylate, succ = succinic acid, bix = 1,4-bis(imidazol-1-ylmethyl)benzene, 1,10′-phen = 1,10-phenanthroline, 2,2′-bipy = 2,2′-bipyridine), have been synthesized and characterized by single-crystallographic X-ray diffraction. Complex 1 shows a two-dimensional covalent layer structure. Complex 2 exhibits a two-dimensional supramolecular layer network composed from discrete fundamental units. Complex 3 exhibits a one-dimensional covalent chain-like structure, which further extends to a two-dimensional supramolecular structure with hydrogen bonding and π-π interactions respectively. Complexes 4 and 5 show three-dimensional supramolecular networks composed from one-dimensional chain-like covalent structures. Furthermore, the magnetic property of complex 3 and fluorescent properties of complexes 1, 2, 4 and 5 have also been studied.
Co-reporter:Yi-Nan Liu, Wan-Zhen Liang, Xiao-Guang Sang, Yu-Qiu Huo, Lap Sze-to, Ka-Fu Yung, Xiao-Xia Liu
Inorganica Chimica Acta 2010 Volume 363(Issue 5) pp:949-956
Publication Date(Web):22 March 2010
DOI:10.1016/j.ica.2009.12.033
Co-reporter:Li-Jun Bian, Jiang-Hua Zhang, Ji Qi, Xiao-Xia Liu, Diamond Dermot, King-Tong Lau
Sensors and Actuators B: Chemical 2010 Volume 147(Issue 1) pp:73-77
Publication Date(Web):18 May 2010
DOI:10.1016/j.snb.2010.03.043
Polyaniline and molybdenum oxide composite modified electrode (PANI–MoO3) was prepared through immobilization of the oxide in the polymer matrix. The obtained composite was characterized by XPS and FTIR. Stability and electrocatalytic properties of the composite for the reduction of chlorate were investigated by using cyclic voltammetry and chronoamerometry. It was found that the electrocatalytic activity of MoO3 towards the reduction of chlorate is improved by immobilization in PANI. The composite modified electrode showed a quick response time of 10 s to chlorate. Results of amperometric measurements at a working potential of 0.0 V vs. SCE showed that the composite modified electrode displayed linear amperometric responds to chlorate in a concentration range of 5 μM–10.0 mM with a lower detection limit (LOD) of 1.3 μM. The stability of MoO3 was also improved through immobilization in PANI.
Co-reporter:Xinxin Xu;Xiaoguang Sang;Xiaoxia Liu;Xia Zhang;Ting Sun
Transition Metal Chemistry 2010 Volume 35( Issue 4) pp:501-506
Publication Date(Web):2010 May
DOI:10.1007/s11243-010-9355-0
Two new supramolecular metal–organic complexes have been synthesized under hydrothermal conditions. Complex 1 exhibits a three-dimensional supramolecular network, constructed from [Co2(H3BPTC)2(phen)2] (H4BPTC = 3,3′4,4′-benzophenone tetracarboxylate acid, phen = 1,10-phenanthroline) discrete units. Complex 2 similarly exhibits discrete [Cu2(DPA)2(bipy)2(H2O)2] (DPA = 1,1′-biphenyl-2,2′-dicarboxylate acid, bipy = 2,2′-bipyridine) units, which are linked to form a three-dimensional supramolecular network through π–π interactions. It is interesting that during the synthesis of complex 1, the H4BPTC ligands undergo partial decomposition to give 1,2,4-benzenetricarboxylate (H3BTC) ligands, which react with Co to form [Co3(BTC)2]n (3). Complex 3 shows a three-dimensional covalent network. The magnetic properties of complexes 1 and 2 have been studied.
Co-reporter:Xu-Yuan Peng;Pei-Jie Hua
Journal of Solid State Electrochemistry 2010 Volume 14( Issue 1) pp:
Publication Date(Web):2010 January
DOI:10.1007/s10008-008-0778-x
Nickel oxide (NiOx) and polyaniline (PAni) were electrocodeposited from NiSO4 and aniline through cyclic voltammetric scans to afford PAni–NiOx composite film at controlled pH environment. The electrochemical activities of the film were investigated by cyclic voltammetry in 0.1 M NaOH and 0.1 M H2SO4, respectively. Typical redox couples of PAni in 0.1 M H2SO4 appeared at approximately 0.2 and 0.4 V vs. saturated calomel electrode (SCE); Ni(II)/Ni(III) redox couple was observed at approximately 0.4 V vs. SCE in 0.1 M NaOH. The morphologies and elemental components of the films were inspected by scanning electron microscopy and energy dispersive X-ray diffraction. The stability of nickel oxide in the films was found to be enhanced against acidic environments. Electrochemical catalytic behavior of NiOx within the composite film was conserved and demonstrated by catalytic oxidation of methanol and ethanol.
Co-reporter:Fan-Wu Zeng, Xiao-Xia Liu, Dermot Diamond, King Tong Lau
Sensors and Actuators B: Chemical 2010 Volume 143(Issue 2) pp:530-534
Publication Date(Web):7 January 2010
DOI:10.1016/j.snb.2009.09.050
Humidity sensor based on polyaniline nanofibres was fabricated and its response to humidity was investigated. It was found that the sensor behaved differently compared to commonly known conducting polymer based sensors. The sensor responded to low relative humidity (<50% RH) normally by decreasing electrical resistance with increasing humidity. However, at higher RH the sensor reversed its responses by increasing the electrical resistance with humidity. It is believed that the unique structure of nanofibres, which is more susceptible to distortion during polymer swelling, is responsible for the ‘reversed behaviour’. IR data confirmed that excess water absorption occurred and that a change in polymer oxidation state might also have taken place.
Co-reporter:Xu-Yuan Peng, Feng Luan, Xiao-Xia Liu, Dermot Diamond, King-Tong Lau
Electrochimica Acta 2009 Volume 54(Issue 26) pp:6172-6177
Publication Date(Web):1 November 2009
DOI:10.1016/j.electacta.2009.05.075
Electrodeposition of polyaniline (PAni) was performed across a broad pH range from pH 0.0 to 14.0. PAni films were found to grow from strong acidic environments at much faster rate and appeared to adopt different growth patterns from those grown from higher pH media, thus producing PAni films with very different morphologies ranging from nanofibres to microsized tubules to flakes like structures. The various morphologies of the PAni films were results of homogeneous and heterogeneous nucleation during electrochemical polymerization. These phenomena occurred under specific conditions which could be induced by varying the pH of the reaction media. Characteristic IR absorptions of the films deposited from increasing pH environment indicated little differences in chemical structure of the polymers except for the film grown from pH 14.0. Cyclic voltammetry data also indicated different electron transfer efficiency as a result of different morphology adopted. All except for PAni films obtained from pH 2.0 to 4.0 gave high specific capacitance at around 450 F g−1 in 0.5 M H2SO4 and in 1.0 M NaNO3 (pH 1.0) solution using 1.0 mA cm−2 charging and discharging current density.
Co-reporter:Xinxin Xu, Xiaoxia Liu, Xia Zhang, Ting Sun
Inorganica Chimica Acta 2009 Volume 362(Issue 15) pp:5203-5210
Publication Date(Web):1 December 2009
DOI:10.1016/j.ica.2009.09.025
A series of coordination polymers have been prepared by the combination of flexible ligand 1,1′-biphenyl-2,2′-dicarboxylic acid (H2dpa) and different types of nitrogen-containing ligands, with various metal ions such as Co(II), Zn(II) and Cd(II). The single-crystal structure analyses reveal that the above complexes possess different structure features with the introduction of different nitrogen-containing ligands. When auxiliary linear ligand 4,4′-bipyridine (4,4′-bpy) is introduced, two-dimensional layered complex, [Co2(dpa)2(4,4′-bpy)2(H2O)]n (1) is formed. Whereas if chelating ligand, 1,10-phenanthroline (1,10′-phen) and 2,2′-bipyridine (2,2′-bpy) are introduced, one-dimensional complex [Zn(dpa)(1,10′-phen)]n (2) and discrete complexes [Co2(dpa)2(2,2′-bpy)2(H2O)2] (3), [Co3(dpa)3(1,10′-phen)6(H2O)2] (4), [Cd(dpa)(1,10′-phen)2][(H2dpa)2(H2O)2] (5) are synthesized. To our interest, 1 and 2 crystallize in homochiral spacegroup. Furthermore, the magnetic property of complex 1 and the fluorescent properties of complexes 2 and 5 are studied.In this article, we synthesized five new coordination polymers based on dpa, different nitrogen-containing mixed ligands and 3d metal ions. To our interests, complex 2 exhibits interesting homochiral supramolecular layer structure composed of one-dimensional right-handed helix chains.
Co-reporter:Xin-Xin Xu;Xia Zhang;Ting Sun;Yu-Hong Wang
Transition Metal Chemistry 2009 Volume 34( Issue 5) pp:571-577
Publication Date(Web):2009 August
DOI:10.1007/s11243-009-9231-y
Reduced molybdophosphate-based supramolecular compounds, such as (4,4′-H2bipy)[Co(H2O)2]2[Co(H2PO4)2(HPO4)4(PO4)2(MoO2)12(OH)6] · 17H2O (1), [Co(2,2′-bipy)2(H2O)]4[Co(H2O)2][Co(HPO4)6(PO4)2(MoO2)12(OH)6] · 2H2O (2), and [Co(2,2′-bipy)2(H2O)]4[Co(H2PO4)(H2O)2]2[Co(HPO4)6(PO4)2(MoO2)12(OH)6] · 8H2O (3) (4,4′-bipy=4,4′-bipyridine, 2,2′-bipy=2,2′-bipyridine), have been synthesized under hydrothermal conditions and characterized. Compound 1 exhibits a three-dimensional supramolecular twofold interpenetrating architecture built up of one-dimensional [P4Mo6]-based infinite covalent chains and free 4,4′-bipy molecules. Compound 2 also shows a three-dimensional supramolecular network constructed from one-dimensional covalent [P4Mo6]-based chains. Unlike compounds 1 and 2, compound 3 exhibits an interesting three-dimensional ‘honeycomb-like’ supramolecular network constructed by the stacking of [Co(2,2′-bipy)2(H2O)] units with one-dimensional channels, in which the [P4Mo6]-based polyoxometalate chains are located. The magnetic properties of compounds 2 and 3 are reported.
Co-reporter:Xin-Xin Xu;Xia Zhang;Ting Sun
Transition Metal Chemistry 2009 Volume 34( Issue 8) pp:
Publication Date(Web):2009/11/01
DOI:10.1007/s11243-009-9270-4
Three new coordination polymers have been synthesized from 1,1′-biphenyl-2,2′-dicarboxylic acid (2,2-dpa), nitrogen-containing coligands and Mn salts under hydrothermal conditions. The X-ray crystal structures of all three complexes are presented. With the change of nitrogen-containing ligand, the structural features of the complexes also change. The complex prepared without a nitrogen coligand exhibits a one-dimensional covalent chain-like structure, composed of the rare pentanuclear Mn building unit. The complex with 4,4′-bipyridine as a secondary ligand shows a two-dimensional layer structure. With the chelating ligand 1,10-phenanthroline, a discrete molecular complex is synthesized. The magnetic properties of the complex with 4,4′-bipyridine in the temperature range 1.99–300 K are reported.
Co-reporter:Xin-Xin Xu, Xiao-Xia Liu, Xia Zhang, Ting Sun
Polyhedron 2009 28(14) pp: 2997-3004
Publication Date(Web):
DOI:10.1016/j.poly.2009.07.043
Co-reporter:Li-Jie Sun, Xiao-Xia Liu, Kim King-Tong Lau, Liang Chen, Wei-Min Gu
Electrochimica Acta 2008 Volume 53(Issue 7) pp:3036-3042
Publication Date(Web):25 February 2008
DOI:10.1016/j.electacta.2007.11.034
Hybrid films of polyaniline (PANI) and manganese oxide (MnOx) were obtained through potentiodynamic deposition from solutions of aniline and MnSO4 at pH 5.6. The hybrid films demonstrated characteristic redox behaviors of PANI in acidic aqueous solution. Characterization of the hybrid films by XRD indicated the amorphous nature of MnOx in the films in which manganese existed in oxidation states of +2, +3 and +4, based on XPS measurement. Hybrid film of PANI and MnOx, PM120 obtained from the solution of 0.1 M aniline and 120 mM Mn2+ displayed a well opened nanofibrous structure which showed an 44% increase in specific capacitance from that of PANI (408 F g−1) to 588 F g−1, measured at 1.0 mA cm−2 in 1 M NaNO3 (pH 1). The hybrid film kept more than 90% of its capacitance after 1000 charging-discharging cycles, with a coulombic efficiency of 98%. The specific capacitance of a symmetric capacitor using PM120 as the electrodes is 112 F g−1.
Co-reporter:Xiao-Xia Liu;Ya-Bing Li;Li-Jun Bian
Journal of Solid State Electrochemistry 2008 Volume 12( Issue 7-8) pp:909-912
Publication Date(Web):2008 August
DOI:10.1007/s10008-007-0450-x
Electrodeposition of hybrid film of polyaniline (PANI) and nanoparticles of silica (SiO2) was conducted through electrochemical surface polymerization of aniline, which hydrogen-bonded onto surfaces of SiO2 particles. The hybrid film showed a 3D structure that facilitated the contact of electroactive material with electrolyte. PANI/SiO2 displayed a capacitance of 558 mF•cm−2 in 0.5 M H2SO4 when charged–discharged at 1.5 mA•cm−2, which is 2.5 times of that of similarly prepared PANI film. The capacitance of the hybrid film kept essentially constant when charging–discharging under current densities up to 24 mA•cm–2.
Co-reporter:Xu-Yuan Peng;Wei Li;Pei-Jie Hua
Journal of Applied Polymer Science 2007 Volume 105(Issue 4) pp:2260-2264
Publication Date(Web):26 APR 2007
DOI:10.1002/app.26227
Electrocodeposition of nickel oxide (NiOx) and polyaniline (PANI) was conducted through cyclic voltammetric scans in an aqueous solution of NiSO4 and aniline. Characterizations of the obtained NiOx/PANI composite film by XRD and FTIR indicated that the film composed of NiOx and PANI, in which nickel oxide was in the form of Ni2O2(OH). Ni(II)/Ni(III) redox couple appeared at 0.30 V versus SCE on the cyclic voltammogram (CV) of the composite film. Electrooxidations of glucose and fructose occurred at the potential where nickel oxide existed in higher oxidation state. The anodic current densities at 0.46 V for the electrooxidations were linearly dependent on the concentration of polyhydroxyl compounds from 1 to 100 mM for glucose and 10 to 100 mM for fructose, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Co-reporter:Xiao-Xia Liu;Li-Jun Bian;Lu Zhang
Journal of Solid State Electrochemistry 2007 Volume 11( Issue 9) pp:1279-1286
Publication Date(Web):2007 September
DOI:10.1007/s10008-007-0287-3
Composite films of polyaniline (PANI) and molybdenum oxide (MoOx) were afforded through a convenient route of electrocodeposition from aniline and (NH4)6Mo7O24. The composite films showed characteristic redox behaviors of PANI and MoOx, respectively, on the cyclic voltammograms. Chlorate and bromate were catalytically electroreduced with an enlarged current on the composite film at a potential ca. 0.2 V more positive than that on MoOx. The potential window for the composite film to display pseudocapacitive properties in 1.0 mol·dm−3 NaNO3 was −0.6 ∼ 0.6 V vs SCE. The cathodic potential limit shifted at least 0.4 V negatively from that of polyaniline (PANI)-based materials reported so far. The specific capacitance was 363.6 F·g−1 when the composite film was charged–discharged at 1.5 mA·cm−2, about two times of that of the similarly prepared PANI. The composite film was characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Molybdenum existed in a mixed state of +5 and +6 in the composite film based on XRD and XPS investigations.
Co-reporter:Ke Sun;Wing-Tak Wong;Bao-Yan Zhang
Chinese Journal of Chemistry 2003 Volume 21(Issue 10) pp:
Publication Date(Web):26 AUG 2010
DOI:10.1002/cjoc.20030211016
Substituted decarbonylation reaction of ruthenium 1,2-naphthoquinone-1-oxime (1-nqo) complex, cis-, cis-[Ru| ζ2-N(O)C10-H6O|2(CO)2] (1), with acetonitrile gave cis-, cis-[Ru | ζ2- N(O)C10H6O|2(CO)(NCMe)] (2). Complex 2 was fully characterized by 1H NMR, FAB MS, IR spectra and single crystal X-ray analysis. Complex 2 maintains the coordination structure of 1 with the two naphthoquinonic oxygen atoms, as well as the two oximato nitrogen atoms located cis to each other, showing that there is no ligand rearrangement of the 1-nqo ligands during the substitution reaction. The carbonyl group originally trans to the naphthoquinonic oxygen in one 1-nqo ligand is left in its original position [O(5)-Ru-C(1), 174.0(6)°], while the other one originally trans to the oximato group of the other 1-nqo ligand is substituted by NCMe [N(1)-Ru-N(3), 170.6(6)°]. This shows that the carbonyl trans to oximato group is more labile than the one trans to naphthoquinonic O atom towards substitution. This is probably due to the comparatively stronger ± back bonding from ruthenium metal to the carbonyl group trans to naphthoquinonic O atom, than the one trans to oximato group, resulting in the comparatively weaker Ru–-CO bond for the latter and consequently easier replacement of this carbonyl. Selected coupling of phenylacetylene mediated by 2 gave a single trans-dimerization product 3, while 2 mediated coupling reaction of methyl propiolate produced three products: one trans-dimerization product 4 and two cyclotrimeric products 5 and 6.
Co-reporter:Xin-Xin Xu, Zhong-Ping Cui, Xin Gao and Xiao-Xia Liu
Dalton Transactions 2014 - vol. 43(Issue 23) pp:NaN8813-8813
Publication Date(Web):2014/04/11
DOI:10.1039/C4DT00435C
To improve photocatalytic activity of a coordination polymer (CP) in the visible light region, five different transition metal ions (Fe3+, Cr3+, Ru3+, Co2+ and Ni2+) were introduced into its framework through an ion-exchange process. Among all the resulting transition metal ion doped coordination polymers (TMI/CPs), the one doped with Fe3+ took on the most excellent photocatalytic activity and the highest quantum yields in the visible light region, decomposing 94% Rhodamine B (RhB) in 8 hours. It can be attributed to the doping of Fe3+, which reduced the band gap (Eg) of the original CP, facilitating photocatalysis of the obtained polymer. Compared with the coordination polymer with Fe3+ as a dopant, products doped with other metal ions presented weaker photocatalytic activities in the visible light region, while under the irradiation of ultraviolet light, they showed favorable photocatalytic properties. The results suggest that to dope transition metal ions into the framework of CPs would be an ideal option for enhancing the photocatalytic activity of coordination polymers.
Co-reporter:Ming-Hua Bai, Tian-Yu Liu, Feng Luan, Yat Li and Xiao-Xia Liu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 28) pp:NaN10888-10888
Publication Date(Web):2014/01/29
DOI:10.1039/C3TA15391F
To meet the increasing demand for high energy density supercapacitors, it is crucial to develop positive and negative electrodes with comparable energy density. Previous studies have primarily focused on the development of positive electrodes, while negative electrodes are relatively less explored. Here we report an electro-codeposition method to synthesize a high performance negative electrode composed of a vanadium oxide (V2O5) and polyaniline (PANI) composite. Scanning electron microscopy revealed that the composite film is composed of one-dimensional polymer chains. Energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) confirmed successful incorporation of V2O5 into PANI chains. Significantly, the V2O5–PANI composite nanowires exhibited a wide potential window of 1.6 V (between −0.9 and 0.7 V vs. SCE) and a maximum specific capacitance of 443 F g−1 (664.5 mF cm−2). The flexible symmetric supercapacitor assembled with this composite film yielded a maximum energy density of 69.2 W h kg−1 at a power density of 720 W kg−1, and a maximum power density of 7200 W kg−1 at an energy density of 33.0 W h kg−1. These values are substantially higher than those of other pure V2O5 or PANI based supercapacitors. Moreover, the assembled symmetric supercapacitor device showed an excellent stability with 92% capacitance retention after 5000 cycles. The capability of synthesizing high performance composite electrodes using the electro-codeposition method could open up new opportunities for high energy density supercapacitors.
Co-reporter:Yu Song, Xiang Cai, Xinxin Xu and Xiao-Xia Liu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 28) pp:NaN14720-14720
Publication Date(Web):2015/06/08
DOI:10.1039/C5TA02810H
High-rate asymmetric supercapacitors (ASCs) made of abundant and low-cost electrode materials and operating in safe aqueous electrolytes can be attractive for electrochemical energy storage. Here, we design a new type of ASC by using pseudo-capacitive nanomaterials, Ni–Co double hydroxide (Ni–Co DH) nanosheets and polypyrrole (PPy) films, for the cathode and anode, respectively, which were integrated with a functionalized partially exfoliated graphite (FEG) current collector. Benefiting from the “super highway” for fast electron/ion transportation in hybrid systems, the as-prepared electrodes exhibit superior rate capability (2442 and 2039 F g−1 at 1 and 50 A g−1, with 83.5% retention for Ni–Co DH; 560 and 441 F g−1 at 1 and 50 A g−1, with 79% retention for PPy). The assembled ASC displays a high specific capacitance (261 F g−1 at 1 A g−1) and excellent rate capability; 77% of its initial capacitance can be retained when the current density increases 30 times from 1 to 30 A g−1. An energy density of 61.3 W h kg−1 can be achieved by the ASC at 0.65 kW kg−1. Even at an ultra-high power density of 19.5 kW kg−1, the ASC can still deliver a high energy density of 47.2 W h kg−1. Through careful control of charges which can be stored in the anode and cathode, the cycling stability of the ASC is much improved, and 91% capacitance retention can be achieved after 5000 charge/discharge cycles. These features demonstrate a new avenue for developing high-performance pseudo-capacitive electrodes and rational assembly strategies for high power/energy density charge storage devices with good cycling stability.
Co-reporter:Xinxin Xu, Xin Gao, Tingting Lu, Xiaoxia Liu and Xiuli Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 1) pp:NaN206-206
Publication Date(Web):2014/11/12
DOI:10.1039/C4TA05071A
To improve the photocatalytic activity of a coordination-complex-modified polyoxometalate (CC/POM), a new type of hybrid material (abbreviated as PPy/CC/POMNR) was fabricated by the combination of its nanorod (CC/POMNR) and polypyrrole (PPy) via a facile in situ chemical oxidation polymerization process under the initiation of ammonium persulfate (APS). Under the irradiation of visible light, PPy/CC/POMNR exhibited higher photocatalytic activity compared to CC/POMNR, PPy, and their mechanically blended products formed on the degradation of Rhodamine B (RhB). Optical and electrochemical tests showed that the enhancement of photocatalytic performance can be attributed to the high separation efficiency of the photogenerated electrons and holes on the interface of CC/POMNBs and PPy, which results from the synergistic effect between them. Furthermore, the influence of the concentration ratio between pyrrole (Py) and APS on the morphology, conductivity, and photocatalytic properties of the PPy/CC/POMNR is discussed and the optimal condition to fabricate a hybrid material with high efficiency was determined. These results suggest that the hybrid of CC/POMNR and PPy would be a feasible strategy to enhance the photocatalytic activity of CC/POMNR.
Co-reporter:Xinxin Xu, Zhongping Cui, Ji Qi and Xiaoxia Liu
Dalton Transactions 2013 - vol. 42(Issue 37) pp:NaN13553-13553
Publication Date(Web):2013/07/30
DOI:10.1039/C3DT51178B
To enhance the photocatalytic property of coordination polymers (CPs) in the visible light region, Ag loaded coordination polymer composite materials (Ag/CPs) were synthesized successfully through a photoreduction reaction of Ag+ on the surface of CPs. Photoluminescence (PL) was used to investigate the separation of photogenerated electron–hole pairs and the results illustrated Ag/CPs display higher quantum yields than CPs. This can be attributed to the strong interactions between Ag nanorods and coordination polymers, which lead to electron–hole pair separation between Ag nanorods and CPs. The degradation of Rhodamine B (RhB) was investigated to study the photocatalytic activities. Ag/CPs exhibited excellent photocatalytic activity in the UV and visible light region, while CPs can only decompose RhB under the irradiation of UV light. Furthermore, Ag/CPs showed outstanding stability during degradation of RhB.
Co-reporter:Xin-Xin Xu, Zhong-Ping Cui, Ji Qi and Xiao-Xia Liu
Dalton Transactions 2013 - vol. 42(Issue 11) pp:NaN4039-4039
Publication Date(Web):2013/01/22
DOI:10.1039/C2DT32636A
To improve the photocatalytic activity of a coordination polymer in the visible light region, polyaniline (PANI) was loaded onto its surface through a facile in situ chemical oxidation polymerization process. The resulting PANI loaded coordination polymer composite materials with excellent stability exhibit significantly higher photocatalytic activities than the pure coordination polymer photocatalyst on the degradation of methyl orange (MO) under visible light irradiation. This enhancement can be ascribed to the introduction of PANI on the surface of the coordination polymer, which leads to efficient separation of photogenerated electron–hole pairs as well as a significant expansion of the photoresponse region. Finally, we discussed the influence of acidity on the morphology and photocatalytic activity of the composite material. An optimal condition to obtain the PANI loaded coordination polymer composite material with excellent photocatalytic activity has been obtained.
Co-reporter:Xinxin Xu, Xin Gao, Zhongping Cui, Xiaoxia Liu and Xia Zhang
Dalton Transactions 2014 - vol. 43(Issue 35) pp:NaN13433-13433
Publication Date(Web):2014/07/31
DOI:10.1039/C4DT01279H
To improve the photocatalytic activity of a transition metal coordination polymer modified polyoxometalate (TMCP/POM), polypyrrole (PPy) was loaded on its surface through a facile in situ chemical oxidation polymerization process. Under the irradiation of visible light, the PPy loaded TMCP/POM composite material exhibited better photocatalytic activity than TMCP/POM, PPy and their mechanically blended products with respect to the degradation of Rhodamine B (RhB). Optical and electrochemical tests illustrated that the enhancement of photocatalytic activity can be attributed to the high separation efficiency of the photogenerated electron–hole pair on the interface of PPy and TMCP/POM, which originates from a synergy effect between them. Furthermore, the influence of reaction temperature on the morphology, wettability, conductivity and photocatalytic performance of the resulting composite material was discussed and an optical temperature to fabricate the photocatalyst with high efficiency has been obtained. These results suggest that the loading of PPy on the surface of TMCP/POM would be a feasible strategy to enhance its photocatalytic activity.
