Study On Electrocatalytic Performance Of Cobalt Supported On Nitrogen And Sulfur Co-Doped Hollow Carbon Spheres In Direct Ethanol Fuel Cell Cathode

With the increasingly problem of prominent global energy and environment,direct ethanol fuel cells have been vigorously developed due to their advantages of cleanness,efficiency,and fuel availability.At present,the fuel cell uses a large amount of Pt as a catalyst at the cathode,which makes the cost high,and the Pt-based catalyst is easily poisoned by CO and methanol.Therefore,it is extremely urgent to develop a non-precious metal-based catalyst with excellent catalytic activity and outstanding stability.This article uses polydopamine as carbon precursor,transition metal salt as metal precursor,SiO₂ pellet as hard template,and one-step preparation of nitrogen-doped hollow carbon spheres supporting transition metals for oxygen reduction catalysis of direct ethanol fuel cell cathodes.The selection of metal salts,the number of metal salts,the carbonization temperature and other conditions during the preparation process were optimized.The best oxygen reduction reaction performance of the Co@NC catalyst prepared using a 10 times cobalt salt and prepared at 900?.In order to improve the catalytic performance of Co@NC,the secondary doping of Co@NC was carried out using NH₃ and thiourea,in which NH₃ was used for N doping,and a load of Co_5.47N was prepared when the secondary pyrolysis temperature was 420?.The nitrogen-doped hollow carbon spheres have significantly improved oxygen reduction performance compared to Co@NC.The half-wave potential is 0.87 V and the limiting current is 5.68 mA cm^-2.N,S co-doping is performed using thiourea.The pyrolysis temperature was 750?.N-doped hollow carbon spheres loaded with Co and Co₉S₈ were prepared,and the samples were co-doped with N and S.The SEM mapping showed that each doped element was evenly distributed.On carbon spheres,so Co@NC-thiourea has very good catalytic performance,half-wave potential is at 0.879 V,limiting current can reach 6.1 mA cm^-2,both better than 20%commercial Pt/C,and Pt/C together with the stability and resistance to methanol poisoning experiments,found that Co@NC-thiourea has better stability and resistance to methanol poisoning performance,is a very promising catalyst for fuel cell cathode oxygen reduction.Into the test analysis,this article believes that the above materials can have high performance due to:?1?Polydopamine as a precursor prepared hollow carbon structure is complete,carbon wall is thin,large surface area,is conducive to the transmission of electrons;?2?Both Co_5.47N and Co₉S₈ formed by secondary doping are very active sites for oxygen adsorption;?3?N atoms can generate catalytic sites for oxygen reduction reactions,and N and S have a synergistic effect and doping together which can produce better catalytic activity;?4?The metal particles in the catalyst prepared in this article are contained in the carbon shell,so the stability and resistance to methanol poisoning are very good.In conclusion,the Co@NC-thiourea catalysts prepared in this paper have broad application of cathode catalysts for direct ethanol fuel cells.Moreover,the secondary doping method used herein to increase the activity of the catalyst can also be applied to other non-precious metal materials or non-metal materials to improve their catalytic activity.