Wenhan Niu
Guangzhou Higher Education Mega Center
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Publication
Featured researches published by Wenhan Niu.
Journal of the American Chemical Society | 2015
Wenhan Niu; Ligui Li; Xiaojun Liu; Nan Wang; Ji Liu; Weijia Zhou; Zhenghua Tang; Shaowei Chen
Thermally removable nanoparticle templates were used for the fabrication of self-supported N-doped mesoporous carbons with a trace amount of Fe (Fe-N/C). Experimentally Fe-N/C was prepared by pyrolysis of poly(2-fluoroaniline) (P2FANI) containing a number of FeO(OH) nanorods that were prepared by a one-pot hydrothermal synthesis and homogeneously distributed within the polymer matrix. The FeO(OH) nanocrystals acted as rigid templates to prevent the collapse of P2FANI during the carbonization process, where a mesoporous skeleton was formed with a medium surface area of about 400 m(2)/g. Subsequent thermal treatments at elevated temperatures led to the decomposition and evaporation of the FeO(OH) nanocrystals and the formation of mesoporous carbons with the surface area markedly enhanced to 934.8 m(2)/g. Electrochemical measurements revealed that the resulting mesoporous carbons exhibited apparent electrocatalytic activity for oxygen reduction reactions (ORR), and the one prepared at 800 °C (Fe-N/C-800) was the best among the series, with a more positive onset potential (+0.98 V vs RHE), higher diffusion-limited current, higher selectivity (number of electron transfer n > 3.95 at +0.75 V vs RHE), much higher stability, and stronger tolerance against methanol crossover than commercial Pt/C catalysts in a 0.1 M KOH solution. The remarkable ORR performance was attributed to the high surface area and sufficient exposure of electrocatalytically active sites that arose primarily from N-doped carbons with minor contributions from Fe-containing species.
Small | 2016
Wenhan Niu; Ligui Li; Ji Liu; Nan Wang; Wei Li; Zhenghua Tang; Weijia Zhou; Shaowei Chen
Graphene-supported mesoporous carbons with rich nitrogen self-doped active sites (N-MC/rGO) are prepared by direct pyrolysis of a graphene-oxide-supported polymer composite embedded with massive, evenly distributed amorphous FeOOH that serve as efficient thermally removable templates. The resulting N-MC/rGO catalysts exhibit high surface areas and apparent electrocatalytic activity for oxygen reduction reaction in alkaline media. Among the series, the sample prepared at 800 °C displays the best performance with a more positive onset potential, higher limiting currents, much higher stability, and stronger poison resistance than commercial Pt/C. This is ascribed to the synergetic functions of the highly conductive graphene support and the mesoporous N-doped carbons that effectively impede the restacking of the graphene sheets and enhance the exposure of the rich nitrogen self-doped active sites.
Journal of Materials Chemistry | 2016
Wenhan Niu; Ligui Li; Nan Wang; Shuaibo Zeng; Ji Liu; Dengke Zhao; Shaowei Chen
The electrocatalytic activity of nitrogen-doped carbons towards the oxygen reduction reaction is largely determined by the concentration of active nitrogen dopants and the electrochemically accessible surface area. Herein we report a novel, facile route for the preparation of N-doped carbons based on direct pyrolysis of polypyrrole nanosheet precursors synthesized by confining the polymerization on the surface of NaCl crystals using FeCl3 as both the initiator and dopant. In the heating-up process of pyrolysis, a large amount of homogeneously distributed FeCl3 dopant and its derivatives gradually evolved into volatile nanoparticles which helped to generate abundant hierarchical macro- and meso-pores, resulting in honeycomb-like porous carbons with a high content of nitrogen dopants ranging from 7 to 18 at%, a large surface area, and an ORR activity superior to that of commercial Pt/C in alkaline electrolytes. Significantly, by using the best sample that was prepared at 800 °C (HPC-800) as the air electrode, a Zn–air battery was found to display a specific capacity of 647 mA h g−1 at 10 mA cm−2 and a negligible loss of voltage even after continuous operation for 110 h, a performance markedly better than that with Pt/C as the air cathode. The results not only highlight the significance of precursor engineering in the synthesis of highly efficient nitrogen-doped carbon catalysts for oxygen electroreduction, but also suggest the high potential of the interfacially confined polymerization method in the scalable preparation of cost-effective, highly porous carbons for electrochemical energy storage and conversion devices.
RSC Advances | 2015
Likai Wang; Zhenghua Tang; Xiaojun Liu; Wenhan Niu; Kai Zhou; Hongyu Yang; Weijia Zhou; Ligui Li; Shaowei Chen
Unlike bulk gold, gold nanoparticles (AuNPs) have been found to exhibit apparent electrocatalytic activity for oxygen reduction reaction (ORR). In this work, glutathione-capped AuNPs of ca. 4 nm in diameter were prepared by a wet chemical method and embedded into a mesoporous carbon matrix synthesized by using an SBA-15 amorphous silica template. Pyrolysis at elevated temperatures led to removal of the organic capping ligands and the formation of ordered mesoporous carbons loaded with a selected amount of AuNPs which exhibited no apparent agglomeration. The obtained nanocomposites exhibited apparent ORR activity in alkaline media, and the sample with 20 wt% AuNPs stood out as the best among the series, within the context of onset potential, kinetic current density and stability, in comparison with AuNPs alone, ordered mesoporous carbons, and commercial Pt/C catalysts. The remarkable performance was ascribed to the intimate interactions between the AuNPs and mesoporous carbons that facilitated fast electron transfer and rapid mass transport. This is the first time that ordered mesoporous carbons were employed to support AuNPs as ORR catalysts. The strategy may be exploited to prepare a wide range of electrocatalysts based on mesoporous carbons-supported metal nanoparticles with extraordinary reactivity and enhanced stability for ORR.
Nano Energy | 2015
Kai Zhou; Weijia Zhou; Xiaojun Liu; Yuanhua Sang; Shaozheng Ji; Wei Li; Jia Lu; Ligui Li; Wenhan Niu; Hong Liu; Shaowei Chen
ChemElectroChem | 2015
Xiaojun Liu; Ligui Li; Weijia Zhou; Yucheng Zhou; Wenhan Niu; Shaowei Chen
Journal of Physical Chemistry C | 2017
Shuaibo Zeng; Ligui Li; Dengke Zhao; Ji Liu; Wenhan Niu; Nan Wang; Shaowei Chen
International Journal of Hydrogen Energy | 2015
Wenhan Niu; Ligui Li; Xiaojun Liu; Weijia Zhou; Wei Li; Jia Lu; Shaowei Chen
Chemical Communications | 2015
Nan Wang; Wenhan Niu; Ligui Li; Ji Liu; Zhenghua Tang; Weijia Zhou; Shaowei Chen
ChemElectroChem | 2016
Ji Liu; Ligui Li; Wenhan Niu; Nan Wang; Dengke Zhao; Shuaibo Zeng; Shaowei Chen