超声辅助法制备双孔空心球状碳化钨及其电催化性能

采用超声空化辅助法制得空心球状结构偏钨酸铵(AMT),通过固定床气-固反应,以CO/H2为还原碳化气氛在700-900℃下制备得到了介孔结构空心球状碳化钨.并再次超声处理后分解球型结构得到条状介孔碳化钨.用扫描电镜(SEM)、X射线衍射(XRD)、热重-差热分析(TG-DTA)、比表面测试(BET)和孔径分布测试(BJH)对样品进行了表征.结果表明,样品组成为单相碳化钨,且在空气中低于410℃时具有高稳定性并且具有4和22nm的双孔隙分布结构.将碳化钨粉末制成粉末微电极(PME),采用循环伏安(CV)技术研究了碳化钨在质子惰性介质中对硝基苯的电催化还原性能.结果表明,相比铂微盘电极,双孔结构碳化钨对硝基苯还原有着更好的电催化活性,在峰电位上比铂微盘正移了30mV,Ip-v1/2关系曲线显示硝基苯在粉末微电极中的还原行为受扩散控制.

Ultrasonic-Assisted Preparation of Bimodal Mesoporous Hollow Global Tungsten Carbide and Its Electrocatalytic Performance

Hollowspherical ammoniummetatungstate (AMT), as a precursor, was prepared by an ultrasonic method. Tungsten carbide (WC) was prepared by a gas-solid reaction in an atmosphere of CO/H₂ at 700-900^oC. Microspheres were fractured by ultrasonic dispersion for 1 h. X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry-differential thermal analysis (TG-DTA), Brunauer-Emmett-Teller (BET) surface area, and Barrett- Joyner-Halenda (BJH) pore-size distribution were used to characterize the morphology, mesoporous structure, and thermal stability of the sample. The results indicate that the sample is pure WC. The WC sample is stable in air at 410 ^oC and the mesopores of WC were centered at 4 nm and 22 nm. A WC powder microelectrode (WC-PME) was prepared using the prepared WC powders. The activity of WC for the electroreduction of nitrobenzene was studied by cyclic voltammetry (CV). The results indicate that the bimodal porosity of WC-PME led to higher catalytic activity than that of a Pt micro disc electrode (Pt-MDE). The reduction potential was 30 mV more positive than that of the Pt-MDE. The relation I_p-v^1/2 showed that the electrode reaction was controlled by liquid diffusion.