•The hydroxyl content in acidic Al2O3 was 2.5 times that in neutral Al2O3.•More hydroxyl group in Al2O3 led to higher NiPt-Al2O3 interaction.•Ni-Pt/acidic Al2O3 had more Pt2 + and Pt4 + species than Ni-Pt/neutral Al2O3.•Ni-Pt/acidic Al2O3 showed 56% selectivity of decarboxylation reaction (DCO2).•Ni-Pt/neutral Al2O3 showed 58% selectivity of decarbonylation reaction (DCO).The catalytic hydroconversion of C18 fatty acids over PtNi/Al2O3 catalysts was investigated to explore the role of hydroxyls in Al2O3 on the catalytic activity. The amount of hydroxyls in acidic Al2O3 was 2.5 times that in neutral Al2O3 but with the same acidity. High content of hydroxyl in Al2O3 increased the NiPt-Al2O3 interaction and differed the Pt valence distribution. The NiPt/acidic Al2O3 catalyst showed 56% DCO2 while the Ni-Pt/neutral Al2O3 catalyst showed 58% DCO products due to the different NiPt-Al2O3 interaction. The high amount of Pt4 + species in NiPt alloy contributed to the high selectivity of DCO2 reaction.Download high-res image (60KB)Download full-size image

Identification of active sites for oxygen evolution reaction (OER) plays a key role in the design and fabrication of high-performance cobalt-based electrocatalysts. Herein, we report the synthesis of two types of two-dimensional monometallic cobalt hydroxide nanoplates in aqueous solution for OER: α-Co(OH)2 with both Co2+Td and Co2+Oh sites and β-Co(OH)2 with Co2+Oh sites. Electrochemical characterization reveals that α-Co(OH)2 is more active than β-Co(OH)2 towards OER. The better activity can be attributed to the presence of Co2+Td sites in α-Co(OH)2, which are more active than Co2+Oh sites. Our finding clarifies the contribution of the two catalytic sites and helps future rational design of high-performance OER electrocatalysts.

Hydroconversion of soybean oils to aviation fuel-like hydrocarbons was investigated over aggregated hierarchical ZSM-5 microspheres composed of small ZSM-5 nanoparticles, which were synthesized via a hydrothermal method by controlling the Si/Al ratio with carbon nanotubes (CNTs) as the template. The prepared ZSM-5 microspheres were investigated by X-ray diffraction (XRD), N2 adsorption and desorption (N2-BET) and scanning electron microscopy (SEM). A low Si/Al ratio resulted in small-sized seed crystals, which then grew into ZSM-5 microspheres through 3D island growth. A high Si/Al ratio resulted in the opposite growth behavior and was prone to forming well-formed individual “classic-boat” ZSM-5 by 2D layer growth. The CNTs acted not only as a mesopore template, but also as a cage to offer suitable space making the ZSM-5 grow into the nanoparticles and form microspheres. The obtained ZSM-5 microspheres had a uniform size (2–3 μm) with a hierarchical structure containing intracrystalline and intercrystalline mesopores. The spherical ZSM-5 zeolites supporting a NiMo catalyst showed high activity and selectivity toward hydroconversion of soybean oil to aviation-like biofuel (C9–C15 hydrocarbons).

Oxygen evolution reaction (OER) plays a key role in energy conversion and storage processes such as water splitting and carbon dioxide reduction. However, the sluggish kinetics caused by insufficient active surface and limited charge transfer hinder OER's wide applications. In this work, a novel self-templating strategy for the fabrication of composite CoO–MoO2 nanocages with enhanced OER performance is proposed. By designing a nanocage structure and incorporating conductive MoO2 to promote both mass and charge transfer, high OER activity (η = 312 mV at 10 mA cm−2) as well as good stability in the resulting CoO–MoO2 composite nanostructure can be achieved. This versatile synthetic strategy can also be extended to other metals (such as W) to provide greater opportunities for the controlled fabrication of mixed metal oxide nanostructures for electrochemical applications.

Hydrogen evolution reaction (HER) plays a key role in generating clean and renewable energy. As the most effective HER electrocatalysts, Pt group catalysts suffer from severe problems such as high price and scarcity. It is highly desirable to design and synthesize sustainable HER electrocatalysts to replace the Pt group catalysts. Due to their low cost, high abundance and high activities, cobalt-incorporated N-doped nanocarbon hybrids are promising candidate electrocatalysts for HER. In this report, we demonstrated a robust and eco-friendly host-guest approach to fabricate metallic cobalt nanoparticles embedded in N-doped carbon fibers derived from natural silk fibers. Benefiting from the one-dimensional nanostructure, the well-dispersed metallic cobalt nanoparticles and the N-doped thin graphitized carbon layer coating, the best Co-based electrocatalyst manifests low overpotential (61 mV@10 mA/cm2) HER activity that is comparable with commercial 20% Pt/C, and good stability in acid. Our findings provide a novel and unique route to explore high-performance noble-metal-free HER electrocatalysts.A robust and high efficient HER electrocatalyst have been prepared by integrating the metallic cobalt nanoparticles with natural silk fibers derived N-doped carbon fibers.Download high-res image (231KB)Download full-size image

•Hierarchical ZSM-5 zeolite was synthesized using TPABr-grafted MWCNT as template.•The graft modification enhanced the utilization of the hard template MWCNT.•The acid distribution was tailored by controlling the grafted TPABr content on WMCNT.•This strategy improved pore connectivity of hierarchical ZSM-5 zeolite.Tailoring the pore size and network connectivity of the hierarchical zeolite is still a great challenging task. Herein, a method was developed to synthesize high pore connectivity hierarchical ZSM-5 by using a novel bifunctional template, TPABr-grafted MWCNT. By this method we obtained the hierarchical ZSM-5 zeolite with more mesoporous structure and high ratio of Brønsted to Lewis acid sites (B/L) due to the high utilization of CNT. The structure and properties of the bifunctional template and the hierarchical ZSM-5 zeolites were confirmed by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), N2 adsorption and desorption (N2-BET) and ammonia temperature programmed desorption (NH3-TPD).Download high-res image (58KB)Download full-size image

•MoS2 and WS2 interleaved nanowalls with active edges on SNCF was demonstrated.•These electrocatalysts exhibit prominent HER activities.•Electrons can be delivered directly from SNCF to vertically aligned nanowalls.Finding cost-effective, active and durable catalyst materials for energy applications, such as electrocatalytic hydrogen production, is an intriguing challenge. Here, a facile and effective approach to the design and construction of two-dimensional MoS2 and WS2 interleaved nanowalls with maximum exposures of active edges on silk-derived N-doped carbon fibers (SNCF) was demonstrated. The morphological evolutions of the MoS2 and WS2 nanocrystals on the SNCF from crescent-like nanosheets to an interleaved nanowall network can be obtained by adjusting the concentrations of the Mo and W precursors. These robust MoS2/SNCF and WS2/SNCF electrocatalysts exhibit prominent hydrogen evolution reaction (HER) activities with onset potentials of −40 and −96 mV and Tafel slopes of 60 and 66 mV dec−1, respectively. The overpotentials (η) at j = −10 mA cm−2 for MoS2/SNCF and WS2/SNCF are −102 and −157 mV, respectively. In addition, MoS2/SNCF and WS2/SNCF are both able to sustain continuous HER operation for 10 h under working conditions with only a slight degradation in current densities, implying excellent durability and a prospect for practical applications.Two-dimensional MoS2 and WS2 interleaved nanowall network with maximum exposed active edges on silk-derived N-doped carbon fibers (SNCF) was demonstrated.

3D dendritic WSe2 on conductive carbon nanofiber mats (d-WSe2/CFM) was designed and synthesized by a diffusion-controlled CVD method. The d-WSe2/CFM was directly used as a cathode for the HER. The substantially improved HER performance is ascribed to the novel 3D structure with effectively exposed edge sites.

•The support interacted with the metals and affected the valence.•NiMo/SAPO-11 has more NiMoO4- and MoO3 sulfides than NiMo/Al2O3.•NiMo/SAPO-11 decarboxylates more than 40% of jatropha oil.•NiMo/Al2O3 hydrodeoxygenates nearly 62% of jatropha oil.The support effect on the NiMo phase was studied by using two kinds of mesoporous materials, SAPO-11 and Al2O3, which were applied on the hydroconversion of jatropha oil. It was shown that the amounts of strong acidic sites of the NiMo/SAPO-11 catalyst (610 μmol/g) was higher than that of NiMo/Al2O3 catalyst (190 μmol/g), resulting into the different NiMo phase formed on the respective SAPO-11 and Al2O3. The NiMo/SAPO-11 catalyst with larger NiMoO4− and MoO3 sulfided phases showed higher selectivity for decarboxylation reaction (41.2%), while the NiMo/Al2O3 catalyst with more Mo4+ polymeric octahedral sulfided phases led to main hydrodeoxygenation products (62.5%).

High efficiency and sulfur-tolerant Pt–Al/MCM-41 catalysts were prepared with Al(NO3)3, AlCl3 and Al(CH3)3 as promoters. The highest tetralin conversion and the best sulfur-tolerance were achieved on the Al(CH3)3-promoted catalyst. The pseudo first-order rate constants of this catalyst for tetralin hydrogenation are about 2–5 and 8–10 times as high as that of the Al-free one under sulfur-free and sulfur-containing conditions, respectively. AlCl3 also improves the catalytic activity and sulfur-tolerance considerably while Al(NO3)3 has certain promoting effects on sulfur-tolerance. These promoting effects can be ascribed to (i) the anchor and isolation effects improving the platinum dispersion which benefits tetralin hydrogenation and sulfur-tolerance. (ii) The electron-withdrawing effect is in the order Al(NO3)3 > AlCl3 > Al(CH3)3, resulting in a similarly electron deficient Ptδ+ order of the corresponding catalysts. The sulfur-tolerance is in favour of electron deficient Ptδ+, though the opposite of this is true for the tetralin hydrogenation. (iii) The acid sites and especially the hydroxyl sites, provide additional active sites and spillover hydrogen which also contribute to the tetralin hydrogenation and sulfur-tolerance of the catalysts.

Hierarchical ZSM-5 catalysts were prepared by desilication with different NaOH concentrations. Their structure and acidity were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption and desorption, ammonia temperature-programmed desorption (NH3-TPD), pyridine Fourier transform infrared (FTIR) spectroscopy, CO chemisorptions, and hydrogen temperature-programmed desorption (H2-TPR). The catalytic conversion of jatropha oil into alternative fuel over the NiMo/hierarchical ZSM-5 catalysts was investigated. The deoxygenation pathways were tuned by controlling the alkaline treatment. The DCO2 reaction was strongly favored by strengthening the support-active phase interaction. The aromatization reaction among C2–C8 olefins led to the increase of organic liquid products, especially the C9–C15 hydrocarbons. In addition, this reaction was significantly improved by partial amorphization of the support but inhibited by the development of intracrystal mesopores. The larger mesoporous structure improved the selectivity of C9–C15 paraffins. Moreover, the intracrystal mesopores had better catalytic cracking selectivity for C9–C15 paraffins than pure microporous structure and amorphous structure.

Catalytic hydroconversion of C18 fatty acids with different hydrogen donors (H-donors) was carried out in a fixed bed reactor to intensify the selectivity for preparing renewable diesel through advanced hydrodeoxygenation technology. Two types of H-donors, condensed aromatics and hydroxyl compounds, were investigated and found that the H-donors had little influence on the yields of C15 and C16 hydrocarbons but significant for C17 and C18 hydrocarbons. Condensed aromatics have a positive effect on the yields of C17 and C18 hydrocarbons. Alcohols significantly enhance the selectivity for C18 hydrocarbon and suppress the selectivity for C17 hydrocarbon. The yield of C18 hydrocarbon is nearly doubled with 5 wt% ethanol. A multi-step mechanism is proposed to elucidate the phenomena.

3D dendritic WSe2 on conductive carbon nanofiber mats (d-WSe2/CFM) was designed and synthesized by a diffusion-controlled CVD method. The d-WSe2/CFM was directly used as a cathode for the HER. The substantially improved HER performance is ascribed to the novel 3D structure with effectively exposed edge sites.

High efficiency and sulfur-tolerant Pt–Al/MCM-41 catalysts were prepared with Al(NO3)3, AlCl3 and Al(CH3)3 as promoters. The highest tetralin conversion and the best sulfur-tolerance were achieved on the Al(CH3)3-promoted catalyst. The pseudo first-order rate constants of this catalyst for tetralin hydrogenation are about 2–5 and 8–10 times as high as that of the Al-free one under sulfur-free and sulfur-containing conditions, respectively. AlCl3 also improves the catalytic activity and sulfur-tolerance considerably while Al(NO3)3 has certain promoting effects on sulfur-tolerance. These promoting effects can be ascribed to (i) the anchor and isolation effects improving the platinum dispersion which benefits tetralin hydrogenation and sulfur-tolerance. (ii) The electron-withdrawing effect is in the order Al(NO3)3 > AlCl3 > Al(CH3)3, resulting in a similarly electron deficient Ptδ+ order of the corresponding catalysts. The sulfur-tolerance is in favour of electron deficient Ptδ+, though the opposite of this is true for the tetralin hydrogenation. (iii) The acid sites and especially the hydroxyl sites, provide additional active sites and spillover hydrogen which also contribute to the tetralin hydrogenation and sulfur-tolerance of the catalysts.