Theoretical Design Of Supported Atomic Electrocatalysts Towards Oxygen Reactions

At present,the study of highly active transition metal-based catalysts for oxygen reduction reaction（ORR）and oxygen evolution reaction（OER）is one of the important ways to solve the slow cathode reaction kinetics of fuel cells.The single atom catalyst can achieve100%atomic efficiency,greatly improve the contact area,and the active site structure also has uniform characteristics.The catalytic performance of monatomic catalyst is closely related to the support.Phthalocyanine-based catalysts are derived from the natural composition structure of organisms,and MoS₂ is also one of the few materials with natural layered structure,which indicates that phthalocyanine-based and MoS₂-based materials can be obtained by simple operation without complex chemical synthesis.In this paper,density functional theory was used to investigate the change of catalytic activity of phthalocyanine-based monatomic catalysts and MoS₂-based monatomic catalysts.The main research contents and conclusions are as follows:（1）The catalytic activity of ORR and OER of phthalocyanine-based monatomic catalyst（TMPc,in which TM is a transition metal containing 3d,4d and 5d valence electrons）has been systematically studied.In all the designed structures,Co Pc,Rh Pc and Ir Pc were found to have excellent ORR/OER double-acting catalytic activities,with ORR overpotentials of 0.22,0.44 and 0.41 V,and OER overpotentials of 0.44,0.55 and 0.26 V,respectively,which were lower than/close to commercial catalysts.Through the step-by-step protonation process simulation of the above system,it was found that the activity of ORR decreased significantly after protonation,but the catalytic activity of OER changed slightly.The OER of Co Pc（*H）,Rh Pc（*H）,Ir Pc（*H）,Co Pc（*2H）,Rh Pc（*2H）and Ir Pc（*2H）was 0.39,0.50,0.49,0.23,0.45 and 0.44 V,respectively.In addition,the effect of hydroxyl modification on catalytic activity was simulated.It was found that the over-potential of Co Pc and Rh Pc ORR after hydroxyl modification was 0.37 V,while the ORR catalytic performance of Ir Pc after hydroxyl modification was significantly decreased.（2）The catalytic activity of MN₆（TM including Ti,V,Cr,Mn,Fe,Co,Cu,Ni,Zn,Zr,Nb,Tc,Ru,Rh,Pd,Ag and Cd）was investigated with MoS₂ as the support.It was found that V-N₆-MoS₂ and Cr-N₆-MoS₂ have ORR/OER bi-functional catalytic activities by calculating the adsorption energy and free energy curves of intermediates,with ORR overpotential being 0.34 V and 0.57 V,and OER overpotential being 0.56 V and 0.48 V,respectively.Meanwhile,the thermal stability（300K）of the catalyst was determined by first principles molecular dynamics simulation.Through the calculation of transition states,it is proved from the kinetic point of view that V-N₆-MoS₂,Cr-N₆-MoS₂and Mn-N₆-MoS₂ are more prone to association reactions.