Preparation Of Mo,W Chalcogenides/Carbon Black Composites And Their Electrocatalytic Oxygen Reduction Properties

Fuel cells(FC)is an energy conversion device that converts chemical energy into electrical energy directly.It has been a research focus in the field of energy materials in recent years because it meets the development direction of clean,safe,and renewable green energy.The cathode oxygen reduction reaction(ORR)plays a crucial role in the fuel cell.At present,platinum and platinum-based catalysts are still mainstream FC cathode catalysts with excellent ORR catalytic activity.However,platinum and platinum-based precious metal catalysts have many shortcomings,such as expensive,lack of resources,poor methanol tolerance and CO poisoning,which seriously hinders the practical application of FC.Therefore,it is necessary to find an ORR catalyst with rich earth abundance,high catalytic activity and good stability.Non-precious metal chalcogenide catalyst is an important alternative to commercial Pt/C catalyst due to rich reserves,low cost,good stability and high catalytic activity.In addition,carbon black(Vulcan XC-72)is commonly used as a catalyst carrier due to its high specific surface area,good conductivity.The main research contents are as follows:(1)The MoO2/C composite catalyst was synthesized by a simple one-step solvothermal method using Vulcan XC-72 as a carrier.The effect of different carrier content on the catalytic performance of ORR was investigated by electrochemical experiments.Compared with simple MoO2 and Vulcan XC-72,the ORR catalytic performance of MoO2/C composites has been significantly improved.In addition,the ORR process catalyzed by MoO2/C composites is also closer to the four-electron pathway and exhibits good stability and methanol tolerance.(2)Using molybdate dihydrate and thiourea as precursors and Vulcan XC-72 as a carrier,the MoS2/C composite with special morphologies was synthesized by hydrothermal method without using any reductant and morphology control agent.The as-prepared MoS2/C nanocomposite presents a flower-like structure by SEM and TEM characterization.The addition of Vulcan XC-72 enhanced the electrical conductivity and specific surface area of MoS2.Electrochemical measurements showed that the MoS2/C nanocomposite catalysts exhibited significantly improved ORR catalytic activity in both acidic and basic media compared to MoS2 and Vulcan XC-72.And the MoS2/C nanocomposite catalyst exhibiting more excellent stability and methanol tolerance than commercial Pt/C.(3)Using tungsten trioxide as a raw material and Vulcan XC-72 as a carrier,the Vulcan XC-72R modified WS2 nanocomposite(WS2/C)was prepared by solid reaction process combined with sonication.The as-prepared WS2/C nanocomposite presents an irregular porous structure with layered WS2 stacking confirmed by SEM and TEM characterization.The ORR catalytic properties of WS2/C composites with different loading of Vulcan XC-72R were investigated by electrochemical experiments.The experimental results show that the WS2/C composites shows excellent catalytic performance as an ORR catalyst and has better electrochemical stability and more excellent methanol tolerance than commercial Pt/C.