Preparation And Oxygen Reduction Performance Of Porous And High-efficiency Cobalt-based Bimetallic Catalyst

As a green conversion device,fuel cells have been widely investigated by scientists.Oxygen reduction reaction（ORR）is a key factor in determining the performance of fuel cells.At present,the precious metal Pt-based catalyst is the high specific energy of electrode materials,However Pt/C catalyst still have high price.To overcome this constraint,carbon-based transition metal catalysts have attracted great attention due to low price and high catalytic performances comparable to Pt-based catalysts,and are considered to be the most promising electrode material to replace Pt-based catalysts.In this paper,two bimetal-doped catalysts were prepared by pyrolysis method:Fe_0.5Co_0.2/NC catalyst with unique tubular morphology and Mg_0.2Co_0.6/NC catalyst with high specific surface area.The physical morphology and structure of the catalyst were characterized by SEM,BET,Raman and other methods,and uses electrochemical workstation for electrochemically performance research,the main research content is as follows::（1）Preparation of Fe_0.5Co_0.2/NC catalyst.The Fe_0.5Co_0.2/NC catalyst was prepared by pyrolysis at a temperature of 750℃,using glycine as the carbon source and nitrogen source,Fe（NO₃）₃·9H₂O and Co（NO₃）·6H₂O as the metal source.It has a unique tubular morphology,and the hollow tubular structure effectively improves the utilization of active sites.Compared with Fe_0.5Co_0.2/NC-N catalyst which without adding Na Cl,the catalytic performance of Fe_0.5Co_0.2/NC with tubular structure has been greatly improved.By adjusting the amount of metal elements added through experiments,an oxygen reduction catalyst with the best element ratio was finally obtained,which showed higher activity than the commercial Pt/C catalyst.In the 0.1 M KOH alkaline electrolyte,it has an excellent half-wave potential(E_1/2)of 0.872 V,and the onset potential(E_onset)even reaches1.03 V.（2）Preparation of Mg_0.2Co_0.6/NC catalyst.The research idea was based on the characteristics of Mg CO₃can releases CO₂to produce pore structure during high-temperature pyrolysis process to control the pore structure and morphology of the catalyst.Therefore,the Mg_0.2Co_0.6/NC catalyst with a high specific surface area（539.17m²/g）was innovatively synthesized in this work.The results of scanning electron microscopy characterization reveal that a large number of pore structures inside the catalyst,which is much convenient to the mass transfer process of the oxygen reduction reaction.Compared with the single metal catalyst,the Mg-Co bimetallic co-doped catalyst has better catalytic performance,and its half-wave potential(E_1/2)reaches 0.869 V,which was 39 m V higher than the commercial Pt/C catalyst.In terms of stability,after 8000 s of catalytic reaction,the current retention rate can still maintain 94.5%,which is much higher than the commercial Pt/C catalyst,and this advantage creates conditions for the practical application of the catalyst in the future.