Theoretical Study On The Carbon Based Atomic Level Metal Sites As ORR/OER Catalysts

The energy crisis has aroused the interest of scholars in the research of efficient and low-cost sustainable energy conversion systems,in which electrochemical Oxygen Reduction Reaction（ORR）,Oxygen Evolution Reaction（OER）and Hydrogen Evolution Reaction（HER）play a core role in renewable energy related technologies.In the near future,M-N-C catalysts have shown great application potential in fuel cell,water electrolysis and other fields.In this dissertation,the electrocatalytic performance of Mg/Co-N-C and the influence of surface modification on the catalytic activity of Mn-N-C are systematically studied using density functional theory.The main research contents of this dissertation are as follows:（1）The theoretical study of MgCo-N-C[labeled as:MgCo N_x-gra（x=1-6）,gra represent grahene]as OER and HER electrocatalyst shows that MgCo N₃-gra（VIII-X）and MgCo N_x-gra（x=4-6）embedded graphene have OER catalytic activity and the OER overpotential of MgCo N₅-gra（I）,MgCo N₅-gra（III）and MgCo N₆-gra（I）are 0.38 V,0.42 V and 0.33 V,respectively.MgCo N₄-gra（VII）,MgCo N₃-gra（X）MgCo N₄-gra（VIII）,MgCo N₅-gra（III）,MgCo N₆-gra（I）perform better catalytic activity than Pt with HER overpotential of 0.012 V,0.018 V,0.09 V,0.12 V and 0.13 V,respectively.Among them,MgCo N₅-gra（III）exhibit excellent bifunctional catalytic performance of OER and HER,which can be applied to electrolytic water catalytic reaction.（2）The theoretical study of Mn-N-C[labeled as:MnN_x-gra]as an electrocatalyst for ORR reaction find that configuration of N coordination affects the ORR catalytic activity.Among the MnN_x-gra（x=1-4）configurations considered,MnN₄-gra has the best catalytic performance,exhibits an overpotential of 0.81 V.It is found that the strong adsorption ability of the reaction intermediates is the origin for the unfavorable catalytic activity.In order to further improve the electrocatalytic performance of MnN₄-gra,the catalytic active site was modified with electron-withdrawing functional groups（OH,O,CN,p N,F and Cl）.The results indicate that the CN and Cl functional groups can greatly reduce the adsorption energy of intermediates,and give rise to modified lower ORR overpotential of 0.45 V and0.50 V,respectively.