Study On The Oxygen Assisted Reduction Performance Of Transition Metal Selenide/carbon-based Supports

With the globalization of energy crisis and the severity of environmental pollution,the development of clean energy is of great importance and high priority,especially for China.Direct methanol fuel cells?DMFC?as the promising and environmental-friendly energy generation systems,which have many advantages such as fuel renewable,low cost,high energy density and portable,have been attracted more and more attention.Although the great achievements have been made in recent years,the catalysts of DMFC cathode are still show some issues for high cost,poor stability and easy methanol penetration.To solve the problem,it is urgent to find a catalyst with low cost,high activity and strong methanol tolerance.Due to the irreplaceability of Pt,two different Pt-based cathode catalyst supports with strong methanol tolerance and ORR co-catalytic activity are prepared in this study.X-ray diffraction?XRD?and tansmission electron microscopy?TEM?are used to analyze the physical and chemical characterization of as-synthesized supports and catalysts.The electrochemical properties are evaluated by using CV,RDE tests and other means.Trough simultaneous synthesis method,tungsten diselenide/porous carbon?WSe₂/C?composites with porous structure as Pt-supports and co-catalysts are prepared by using selenium powder?selenium source?,ammonium tungstate?tungsten source?and citric acid?carbon source?.The correlation of active components,structure and the ORR activity of WSe₂/C are detected by tuning the heating temperature?800–1000 ^oC?.It can be found that Pt-WSe₂/C-800 has far higher electro-catalytic activity(specific activity 4.57 mA·cm^-2),methanol tolerance and durability for ORR than those of commercial Pt/C(specific activity 2.69 mA·cm^-2).The close connection between the Pt,WSe₂ particles and the carbon skeleton can effectively improve the exposure of Pt active sites and promote the rapid adsorption,activation and reduction of oxygen molecules.Besides,molybdenum selenide/biomass-derived carbon?MoSe₂/BC?composites and nitrogen-doped composites?N-MoSe2/BC?as Pt-supports and co-catalysts are prepared by using selenium powder?selenium source?,ammonium molybdate?molybdenum source?,pomelo skin?carbon source?and melamine?nitrogen and+carbon sources?.The results show that Pt-N-MoSe₂/BC exhibits high activity(14.83 mA·cm^-2)and selectivity?4e^-?,promising durability and excellent tolerance against methanol-crossover,which are superior to those of Pt-MoSe2/BC,Pt-WSe2/C and commercial Pt/C.The synergy between Pt,N-species and MoSe₂/porous carbon can significantly improve the exposure of the active site on Pt?111?facets,thereby enhancing charge transfer efficiency and ORR activity.Meantime,N-species embedded in the carbon skeleton and the exposed?N?-MoSe₂ edge sites can effectively resist the methanol infiltration.