The Research On The New Pattern Of Cathode Composite Catalysts Of Direct Methanol Fuel Cells

Fuel cells are generating electricity devices, directly transforming chemical energy into electricity by means of electrochemical reactions at the same temperature。It is a kind of clean energy with high efficiency, low pollution and promising development. Direct methanol fuel cells(DMFCs) become a focus of researchers because of its good theoretical energy density and energy efficiency. DMFCs are of extensive applying prospect in the future. But now DMFCs are far away from producing cosmically in commerce, which is caused by expensive price and low catalytic activity for ORR. Therefore, the new kind of cathode catalysts which have low price, high catalytic activity of ORR and good selectivity towards the ORR must be studied for a broad commercial application.This paper focuses on the study of cathode catalysts for direct alcohol fuel cells. Based on the above shortcomings of Pt-based catalysts, nano-tungsten carbide improved AuPdPt-WC/C noble metallic composite catalysts was studied.Nano-tungsten carbide was prepared by intermittent microwave heating method (IMH) in this study. IMH has many advantages such as high temperature, fast reaction rate and small particles of the prepared catalysts. The results of XRD for the catalysts showed the forming of crystal tungsten carbide. The results of SEM showed that tungsten carbide powder prepared by IMH was uniformly dispersed and the particle size was small. WC prepared by IMH has obvious high surface area compared to the tungsten carbide prepared by ordinary heating drying. Electrochemical tests showed prepared tungsten carbide had catalytic activity towards ORR in alkaline solution.Nano-tungsten carbide promoted composite catalyst AuPdPt-WC/C was prepared by IMH and on-site reducion method. In alkaline solution, the composite catalyst showed higher activity than that of commercial Pt/C catalyst with more positive onset potential. The onset potential of ORR on the composite catalyst shifted positively more than 90 mV than that of Pt/C catalyst. Current density of ORR on the composite catalyst was larger. Discussed the factors of electrolyte concentration, temperature and alcohol on AuPdPt-WC/C composite catalysts for ORR in alkaline solution, and the results showed that AuPdPt-WC/C electrocatalyst with a ratio of Au:Pd:Pt:WC/C= 1:1:1:1 shows the best performance of ORR at the same conditions. Composite catalysts for ORR in low concentration of the alkaline solution shows better performance and more stable than that in high concentration. And in certain temperature range, high temperature is beneficial to improve the electrochemical activity of composite catalysts for ORR, and accelerate the speed of oxygen reduction reactions, consequently improving the working efficiency of the fuel cells. In addition, The AuPdPt-WC/C composite catalysts for ORR is hardly affected by methanol in the methanol-containing solutions and showed a strong ability of resistance to methanol oxidative. Therefore, AuPdPt-WC/C electricatalyst has a very good application prospect in direct methanol fuel cells.In this research nano-tungsten carbide and novel composite catalysts based on nano-tungsten carbide were prepared and the performances of it was studied. The results showed that the nano-tungsten carbide enhanced AuPdPt-WC/C composite catalysts had good catalytic activity towards ORR. This composite electrocatalysts have great potential to be used as the cathodic catalyst in direct methanol fuel cells.