The rational construction of low cost, efficient, and stable oxygen reduction reaction (ORR) electrocatalysts is important for the commercialization of fuel cells and metal–air batteries. In this article, we report an easy and effective soft-template method to in situ assemble Fe2N nanoparticles on the surface of N-doped graphene-like carbon (NC). The prepared Fe2N nanoparticles were covered by a few carbon layers, which promoted the connection of Fe–NX clusters with graphene to facilitate the formation of Fe–N–C active sites. Fe–NX and NC units were found to respectively fulfill different functionalities, and commonly afford the sample with excellent performance. The electrochemical data show that the Fe2N@NC composite with high-purity and good crystalline displays a synergistic enhanced catalytic activity for ORR, including a positive onset potential (0.084 V), a half-wave potential (−0.036 V) and a high electron transfer number (∼4e−), as compared to 20% Pt/C. Additionally, the existence of carbon shells wrapped around Fe2N nanoparticles can restrain their expansion and dissolution. In addition, the as-prepared catalyst was implemented as an air catalyst for zinc–air batteries and was found to display a comparable open circuit voltage of ca. 1.48 V and a maximum power density of 82.3 mW cm−2. These results demonstrate that the Fe2N@NC catalyst may serve as a good alternative to precious Pt for ORR in practical applications.

The authors have synthesized nanostructured manganese(II) phosphate hollow spheres [Mn3(PO4)2 HS] with tunable pore structure by using a micro-emulsion method. These, if deposited on a glassy carbon electrode (GCE), are shown to be a viable material for electrochemical sensing of superoxide (radical) anion (O2˙−) at a typical working voltage of 0.7 V (vs. SCE). Hence, they act as biomimetic enzymes that allow for the determination of O2˙− with a very low detection limit (1.35 nM), wide linear range (5 nM to 0.4 mM), and good long-term stability. The modified GCE was applied in-situ to the electrochemical determination of O2− that is released from human malignant melanoma cells and normal keratinocyte, and it showed excellent real time analytical capability. In our perception, the use of this material offers exciting opportunities in terms of implementing nanoscale transition metal phosphates as biomimetic enzymes in enzyme-free diagnostic sensors. Conceivably, these will offer higher sensitivity and longer durability than assays based on the use of natural enzymes.

•One-dimensional MoS2@TiO2 CNBs was fabricated.•The composite displayed excellent catalytic activity with 91% efficiency in 7 min.•A monitoring apparatus was proposed to estimate the photodegradation of toxic gas.Ammonia pollution poses serious threats to public health, especially in livestock. Developing an efficient method to eliminate ammonia is critical for environmental control in agricultural livestock. Herein we fabricate a one-dimensional coaxial nanobelts of molybdenum disulfide growth on titanium dioxide encapsulated carbon nanobelts (MoS2@TiO2 CNBs) by electrospinning followed hydrothermal reaction method. The as-prepared catalysts were used to photocatalytic degradation of ammonia gas, and the experiment results show that MoS2@TiO2 CNBs displayed excellent photocatalytic activity and degraded ammonia gas with 91% efficiency after only 7 min, which mainly attributed to the synergistic effect from chemical compositions and the robust banding structure. Additionally, we propose an economical, convenient, and effective in situ analysis and monitoring method for photodegradation of ammonia, which presents promising application for further development of other high efficient photocatalysts for toxic pollutant degradation.

Activated carbons with large surface area, abundant microporosity and low cost are the most commonly used electrode materials for energy storage devices. However, activated carbons are conventionally made from fossil precursors, such as coal and petroleum, which are limited resources and easily aggregate large block in high temperature carbonization processes. In this novel work, we examined the use of rice straw as a potential alternative carbon source precursor for the production of graphene-like active carbon. A very slack activated carbon with ultra-thin two-dimensional (2D) layer structure was prepared by our proposed approach in this work, which includes a pre-treatment process and potassium hydroxide activation at high temperatures. The obtained active carbon derived from rice straw exhibited a capacitance of 255 F/g at 0.5 A/g, excellent rate capability, and long cycling capability (98% after 10,000 cycles).Download high-res image (169KB)Download full-size imageActivated carbons with large surface area, abundant microporosity and low cost are the most commonly used electrode materials for energy storage devices. A very slack activated carbon with ultra-thin two-dimensional (2D) layer structure was prepared by our proposed approach in this work, which includes a pre-treatment process and potassium hydroxide activation at high temperatures.

In this work, we reported a novel and slack rose-like metal organic precursor designed by coordinating p-phenylenediamine with cobalt ion. After subsequent pyrolysis and acid etching process, the as-prepared Co–N–C catalyst delivered a superior catalytic activity and long-term durability. Further applied in the Zn–air battery, it also displayed a comparable performance with 20% Pt/C.

A low-cost, high-performance, and durable catalyst for oxygen reduction reaction (ORR) is prerequisite for the commercialization of fuel cells. Continuous efforts are made to explore nonprecious, efficient catalysts to replace the expensive and scare platinum-based catalysts. Here, we demonstrate a kind of novel nitrogen and phosphorus co-doped mesoporous carbon spheres (NPMCS) synthesized by hydrothermal assisting pyrolysis of food yeast. The as-prepared mesoporous carbon hollow spheres exhibit a high specific surface area of 1223 m2 g−1, deliver an excellent electrocatalytic performance for ORR in alkaline media, superior durability and high resistance to methanol cross-over effect.

For the future of fuel cells, investigations on high activity, stable, and low-cost oxygen-reduction reaction (ORR) catalysts are critical. Transition metals have attracted particular research interest in pursuit of such efficient and sustainable ORR electrocatalysts. In this work, very tiny Co nanoparticles were assembled on 3D graphene (3DG) aerogels uniformly with the help of ascorbic acid (AA) under a facile hydrothermal process. After further thermal annealing in argon, a few carbon layers are formed and wrapped on the Co nanoparticles. The synthesized materials were primarily investigated for ORR, and the experimental results indicate that the as-prepared Co/3DG shows an obviously positive onset potential (−0.01 V) and a much higher limiting current density (5.75 mA/cm2) than Co/3DG prepared without using AA (−0.1 V, 4.6 mA/cm2). Compared with commercial 20%Pt/C, Co/3DG prepared by using AA also displayed excellent durability and superb methanol tolerance performance, which suggests that the special structure of cobalt nanoparticles wrapped with a few carbon layers and its porous 3DG aerogel support can prevent its expansion and dissolution, improve its stability largely, and provide a new way for searching excellent ORR electrocatalysts.

•1D NiMoO4 nanofibres were fabricated by electrospinning technique in the first time.•1D NiMoO4 nanofibres were applied in nonenzymatic glucose sensors firstly.•A possible electrocatalytic mechanism of the nanoparticles for the glucose oxidation was proposed.•This work holds great promise for development advanced glucose catalysts for nonenzymatic sensor.Electrochemical oxidation of glucose is the guarantee to realize nonenzymatic sensing of glucose, but greatly hindered by the slow kinetics of its oxidation process. Herein, various nanomaterials were designed as catalysts to accelerate glucose oxidation reaction. However, how to effectively build an excellent platform for promoting the glucose oxidation is still a great challenge. In our work, 1D CaMoO4 and NiMoO4 nanofibres with same morphologies and sub-microstructures were fabricated by electrospinning technique in the first time, and explored to modify the detection electrodes of nonenzymatic glucose sensors. The electrochemical results indicated that the NiMoO4 based sensor exhibited a good catalytic activity toward glucose including the low response potential (0.5 V), high sensitivity(193.8 μA mM−1 cm−2) with a linear response region of 0.01–8 mM, low detection limit (4.6 μM) and fast response time (2 s), all of which are superior to the corresponding values of CaMoO4 nanofibres and even higher than those of most reported NiO and Co3O4 catalysts, which is due to the NiMoO4 nanofibres are not only advantageous to electron transfer, but can mediated the electrocatalytic reaction of glucose. This work should provide a new pathway for the design of advanced glucose catalysts for nonenzymatic sensor.Electrocatalytic reaction of NiMoO4 based non-enzymatic glucose sensor.

In the present study, a simple strategy was developed to fabricate a new Bi2O3 nanostring-cluster hierarchical structure. Precursor microrods composed of Bi(C2O4)OH were initially grown under hydrothermal conditions. After calcination in air, Bi(C2O4)OH microrods were carved into unique string-cluster structures by the gas produced during the decomposition process. To explain the formation mechanism, the effects of pyrolysis temperature and time on the morphology of the as-prepared samples were investigated and are discussed in detail. It was discovered that the nanostring-cluster-structured Bi2O3 consists of thin nanoplatelet arrays, which is advantageous for glucose enzyme immobilization and for designing biosensors. The resulting Bi2O3 structure showed an excellent capability in the modification of electrode surfaces in biosensors by enhancing the sensitivity, with good specificity and response time. Such qualities of a biosensor are ideal characteristics for glucose sensing performance and allow for further explorations of its application in other fields.

The nanorods of cobalt phosphide have been prepared and evaluated as an electrocatalyst for non-enzyme glucose detection. The nanorods were used to modify the surface of an electrode and detect glucose without the help of an enzyme for the first time. The crystal structure and composition of cobalt phosphide were identified by XRD and XPS, respectively, and the morphology of the as-prepared samples was observed by FESEM and TEM. The electrochemical measurement results indicate that the CoP-based sensor exhibits excellent catalytic activity and a far lower detection potential compared to bare GCE. Specifically, the electrocatalytic mechanism of CoP in the detection of glucose was proposed based on a series of physical characterization methods, electrochemical measurements, and theoretical calculations.

MoS2 nanotubes (denoted as MoS2 NTs) assembled from well-aligned amorphous carbon-modified ultrathin MoS2 nanosheets (denoted as MoS2 NT@C) were successfully fabricated via a facile solvothermal method combined with subsequent annealing treatment. With the assistance of octylamine as a solvent and carbon source, interconnected MoS2 nanosheets (denoted as MoS2 NSs) can assemble into hierarchical MoS2 NTs. Such a hybrid nanostructure can effectively facilitate charge transport and accommodate volume variation upon prolonged charge/discharge cycling for reversible lithium storage. As a result, the MoS2 NT@C composite manifests a very stable high reversible capacity of around 1351 mA h g−1 at a current density of 100 mA g−1; even after 150 cycles, the electrode reaches a capacity of 1106 mA h g−1 and it retains a reversible capacity of 650 mA h g−1 after the 10th cycle at a current density of 3 A g−1, all of which indicate that the MoS2 NT@C nanocomposite is a promising negative electrode material for high-energy lithium ion batteries.

Metal–organic frameworks (MOFs) have recently attracted much interest in electrochemical fields due to their controlled porosity, large internal surface area, and countless structural topologies. However, the direct application of single component MOFs is limited since they also exhibit poor electronic conductivity, low mechanical stability, and inferior electrocatalytic ability. To overcome these problems, we implanted multi-walled carbon nanotubes (MWCNTs) into manganese-based metal–organic frameworks (Mn-BDC) using a one-step solvothermal method and found that the introduction of MWCNTs can initiate the splitting of bulky Mn-BDC into thin layers. This splitting is highly significant in that it enhances the electronic conductivity and electrocatalytic ability of Mn-BDC. The constructed Mn-BDC@MWCNT composites were utilized as an electrode modifying material in the fabrication of an electrochemical sensor and then were used successfully for the determination of biomolecules in human body fluid. The sensor displayed successful detection performance with wide linear detection ranges (0.1–1150, 0.01–500, and 0.02–1100 μM for AA, DA and UA, respectively) and low limits of detection (0.01, 0.002, and 0.005 μM for AA, DA and UA, respectively); thus, this preliminary study presents an electrochemical biosensor constructed with a novel electrode modifying material that exhibits superior potential for the practical detection of AA, DA and UA in urine samples.

This work presents a new idea to fabricate an enzyme glucose sensor. A bio-composite was assembled by in situ reducing Ag+ to Ag in glucose oxidase (GOD) solution. In this way, metallic silver can directly deposit onto the GOD surface and induce tight contact between Ag and GOD. The obtained composites were characterized by FESEM, EDS mapping, FTIR, CD, and electrochemical measurements. The Ag–GOD composite formed by an in situ reducing process exhibits facile, direct electrochemistry and good electrocatalytic performance without any electron mediator. The designed glucose biosensor shows high sensitivity, high selectivity, long life and accurate measurement in real serum samples, which is contributed to by a fast, direct electron transfer due to close proximity between Ag and GOD.

In this feature work, unique Bi/bismuth tungstate nanocomposites were fabricated using an in situ one step hydrothermal reaction by using ethylene glycol as the solvent. It is interesting to discover that not only the morphologies but also the composition of the products could be tailored by only adjusting the reaction temperature. When the reaction temperature was below 220 °C, an obvious shape evolution from irregular nanoparticle aggregations to hollow spheres to small nanorods was observed with increasing temperature; while when the temperature was higher than 220 °C, not only a new morphology but also a new phase of metal Bi appeared. In the as-prepared Bi/bismuth tungstate nanocomposites, the very tiny metal Bi particles formed during the in situ reaction dispersed very well on the surface of the bismuth tungstate nanorods, which made them exhibit excellent photocatalytic efficiency for the degradation of Rhodamine 6G (R6G). These results motivated us to perform a series of experiments to understand their formation mechanism and explore their physico-chemical insights while providing guidance to prepare novel metal/Aurivillius oxide nanocomposites for photocatalytic performance.

We report a novel interpenetrating three-dimentional (3D) macroporous graphene aerogels (GAs) composite consisting of MnO2 wrapping for potential supercapacitor applications. In this article, the macroporous GAs holds abundant of interconnected macroporous and has excellent intrinsic high electrical conductivity resulting from the graphene. Therefore, employing the GAs as the substrates to combine with MnO2 will exhibit excellent electronic conductivity and effective ion-transport capability. The 3D macroporous MnO2/GAs composite has a specific capacitance of 200 F g-1. Thus, the corresponding 3D porous hierarchical GAs/MnO2 materials have a great potential to be used in the field of supercapacitors. This strategy could also be used for other materials to improve the performance of supercapacitors.

In this work, Bi2WO6 nanoporous wall was synthesized by using Bi2O3 as template and Bi source. Pt nanoparticles whose average size is about 8 nm were further immobilized on the Bi2WO6 nanoporous wall via a simple chemical reduction process. Their photocatalytic activity and the effect of Pt modification were studied by analyzing the degradation of an organic dye, rhodamine 6G (Rh6G), under simulated sunlight. It was found that the photocatalytic ability of Bi2WO6 nanoporous wall was enhanced by introducing Pt nanoparticles. Bare Bi2WO6 shows a degradation efficiency of 78 % after 1 h, while the degradation efficiency of 5 wt% Pt-modified Bi2WO6 was 99 %, and on further increasing the Pt content in the as-prepared Pt-modified Bi2WO6 catalysts, their photocatalytic ability will decrease. The optimal catalyst could be reused without any decrease for five cycles, which may due to Pt be able to help trap the conduction band electrons in the absence of Rh6G. A possible photocatalytic mechanism was proposed and further proved by transient photocurrent response experiment.

In this work, polyaniline nanowires (PANI-NWs) act as spacers, incorporated with graphene oxide and self-assembled into graphene/PANI hybrid aerogels through a facile hydrothermal route. The as-synthesized samples have been characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS), contact angle measurement, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) for their microstructure, morphology and relative affinities toward water. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements have been used to study the effects of composition, microstructure and morphology of the samples on their capacitive performance. The experimental results indicate that the PANI can effectively tailor the microstructures and electrochemical performances of the products. The as-prepared materials with an appropriate proportion of PANI nanowires can efficiently prevent the adjacent graphene sheets from aggregation and provide fast ionic channels for electrochemical energy storage. A specific capacitance of 520.3 F g−1 has been achieved from graphene/PANI hybrid aerogel, which also exhibits excellent cycling stability.

Manganese dioxide (MnO2) has been used as a sacrificial template to fabricate a polyaniline/multi-walled carbon nanotube (PANI/MWCNT) composite with core–shell structure through a facile route. The as-synthesized samples have been characterized by Raman spectra, Fourier transform infrared spectra, field emission scanning electron microscopy and transmission electron microscopy for their microstructure and morphology. A series of electrochemical measurements have been performed to study the effects of microstructure and morphology of the samples on their capacitive performance. The results indicate that the as-prepared PANI/MWCNT composite with a core–shell structure provides fast ionic channels for electrochemical energy storage. A maximum specific capacitance of 764 F g−1 can be achieved from the hybrid at a current density of 0.25 A g−1, and a fairly good value of 509 F g−1 can be obtained even at a higher current density of 3 A g−1.

•We employ a self-assembly technique to fabricate macroporous graphene-based aerogels (GAs).•GAs have been fabricated by using carbohydrate as morphology oriented agents.•The carbohydrates can tailor the microstructures and physical properties of GAs.•The effect of different carbohydrates to form GAs was also discussed systemically.•All the aerogel samples showed good supercapacitor performance.Homogeneously distributed self-assembling hybrid graphene-based aerogels with 3D interconnected pores, employing three types of carbohydrates (glucose, β-cyclodextrin, and chitosan), have been fabricated by a simple hydrothermal route. Using three types of carbohydrates as morphology oriented agents and reductants can effectively tailor the microstructures, physical properties, and electrochemical performances of the products. The effects of different carbohydrates on graphene oxide reduction to form graphene-based aerogels with different microcosmic morphologies and physical properties were also systemically discussed. The electrochemical behaviors of all graphene-based aerogel samples showed remarkably strong and stable performances, which indicated that all the 3D interpenetrating microstructure graphene-based aerogel samples with well-developed porous nanostructures and interconnected conductive networks could provide fast ionic channels for electrochemical energy storage. These results demonstrate that this strategy would offer an easy and effective way to fabricate graphene-based materials.Graphical abstract

In this work, a hybrid materials of MnO2-wrapped graphene aerogels (GAs) were prepared using a simple in situ reduction method. The porous GAs obtained in our work not only boost ion and electron movement in electrochemical processes but can also serve as a 3D skeleton for combining with MnO2, which allows the poor electronic conductivity of MnO2 nanoparticles to be wired up to a current collector through the underlying GA conducting layers. As a supercapacitor electrode material, the structure exhibits a high reversible capacity of 210 F g−1 at a current density of 0.5 A g−1 with an excellent cycling retention of 99% after the 800th cycle at a current density of 2 A g−1. These results highlight the importance of anchoring MnO2 on GAs for maximum utilization of the electrochemical activity and retaining the good electrochemical stability of the electrode materials.

Morphology-controlled synthesis and large-scale self-assembly of nanoscale building blocks into complex nanoarchitectures is still a great challenge in nanoscience. In this work, various porous NiO nanostructures are obtained by a simple ammonia precipitation method and we find that the reaction temperature has a significant impact on their microstructures. Nanoflowers and nanoflakes have been obtained at 0°C and 50°C, while, weakly self-assembly nanoflowers with nanoflakes are formed at 20°C. In order to understand the process-structure-property relationship in nanomaterial synthesis and application, the as-prepared NiO is used as supercapacitor electrode materials, and evaluated by electrochemical measurement. The experimental results indicate that the material obtained at lower temperature has higher pseudocapacitance, the specific capacitance of 944, 889 and 410 F/g are reached for the materials prepared at 0°C, 20°C and 50°C and further calcined at 300°C, respectively. While the material obtained at higher temperature has excellent rate capacity. This offers us an opportunity searching for exciting new properties of NiO, and be useful for fabricating functional nanodevices.

The electronic and chemical properties of reduced graphene oxide (RGO) can be modulated by chemical doping foreign atoms and functional moieties. Nitrogen-doped reduced graphene oxide (N-RGO) is a promising candidate for oxygen reduction reaction (ORR) in fuel cells. However, there are still some challenges in further preparation and modification of N-RGO. In this work, a low-cost industrial material, urea, was chosen to modify RGO by a facile, catalyst-free thermal annealing approach in large scale. The obtained N-RGO, as a metal-free catalyst for oxygen reduction was characterized by XRD, XPS, Raman, SEM, TEM, and electrochemical measurements. It was found that the optimum synthesis conditions were a mass ratio of graphene oxide and urea equal to 1:10 and an annealing temperature of 800 °C. Detailed X-ray photoelectron spectrum analysis of the optimum product shows that the atomic percentage of N-RGO samples can be adjusted up to 2.6 %, and the resultant product can act as an efficient metal-free catalyst, exhibiting enhanced electrocatalytic properties for ORR in alkaline electrolytes. This simple, cost-effective, and scalable approach opens up the possibility for the synthesis of other nitrogen doping materials in gram-scale. It can be applied to various carbon materials for the development of other metal-free efficient ORR catalysts for fuel cell applications, and even new catalytic materials for applications beyond fuel cells.

We report a general approach for the synthesis of yolk–shell-structured porous dicobalt phosphide/zinc oxide@porous carbon polyhedral/carbon nanotube hybrids (Co2P/ZnO@PC/CNTs) derived from bimetal–organic frameworks, and explore their potential utilization in the electrochemical sensing of superoxide anions. Beyond our expectation, the trace level of O2˙− released from living cells has also been successfully captured by our designed sensor. The presented strategy for the controlled design and synthesis of bimetal–organic frameworks-derived functional nanomaterials offers prospects of developing highly active electrocatalysts in non-enzyme sensors.

MoS2 nanotubes (denoted as MoS2 NTs) assembled from well-aligned amorphous carbon-modified ultrathin MoS2 nanosheets (denoted as MoS2 NT@C) were successfully fabricated via a facile solvothermal method combined with subsequent annealing treatment. With the assistance of octylamine as a solvent and carbon source, interconnected MoS2 nanosheets (denoted as MoS2 NSs) can assemble into hierarchical MoS2 NTs. Such a hybrid nanostructure can effectively facilitate charge transport and accommodate volume variation upon prolonged charge/discharge cycling for reversible lithium storage. As a result, the MoS2 NT@C composite manifests a very stable high reversible capacity of around 1351 mA h g−1 at a current density of 100 mA g−1; even after 150 cycles, the electrode reaches a capacity of 1106 mA h g−1 and it retains a reversible capacity of 650 mA h g−1 after the 10th cycle at a current density of 3 A g−1, all of which indicate that the MoS2 NT@C nanocomposite is a promising negative electrode material for high-energy lithium ion batteries.

In the present study, a simple strategy was developed to fabricate a new Bi2O3 nanostring-cluster hierarchical structure. Precursor microrods composed of Bi(C2O4)OH were initially grown under hydrothermal conditions. After calcination in air, Bi(C2O4)OH microrods were carved into unique string-cluster structures by the gas produced during the decomposition process. To explain the formation mechanism, the effects of pyrolysis temperature and time on the morphology of the as-prepared samples were investigated and are discussed in detail. It was discovered that the nanostring-cluster-structured Bi2O3 consists of thin nanoplatelet arrays, which is advantageous for glucose enzyme immobilization and for designing biosensors. The resulting Bi2O3 structure showed an excellent capability in the modification of electrode surfaces in biosensors by enhancing the sensitivity, with good specificity and response time. Such qualities of a biosensor are ideal characteristics for glucose sensing performance and allow for further explorations of its application in other fields.