Theoretical Study On The Nitrogen Coordinated Bi-metal Doped Graphene As Bifunctional Electrocatalyst For ORR And OER

At present,in order to improve the reaction efficiency of oxygen reduction?ORR?and oxygen evolution?OER?,Precious noble metals Pt,Ru and Ir are generally used as catalysts in fuel cells,but the high price and limited stability prevent the widespread use of Pt,Ru and Ir-based catalysts.Recently,spin-related atomic magnetization has shown great potential in the field of catalysis.Half metals have 100%spin-polarized conductive electrons,but the corresponding research is insufficient.In this dissertation,combined with density functional theory and electrochemical thermodynamic model analysis,we systematically study the ORR and OER performance of Fe-Co and Zn-Co bimetal doped graphene,in order to understand the close relationship between the activity of the catalyst and the microelectronic structure.The main research results of this dissertation are as follows:?1?Theoretical study of Fe-Co doped N coordination defect graphene as an electrocatalyst for both ORR and OER.In this chapter,the results of a spin polarization calculation of FeCoNx?x=1-6?embedded graphene?labeled as:FeCoN_x-gra?show that the itinerant ferromagnetic half-metal is a promising candidate for oxygen reduction reaction?ORR?and oxygen precipitation reaction?OER?.It is found that ferromagnetically coupled spin-polarized electrons in semi-metals can generate finite stray fields,which is beneficial to the initial step of ORR,i.e.,the adsorption of O₂.Meanwhile,the existence of stray magnetic fields can ensure the spin conservation of O atoms and promote the formation of O-O bonds in OER.More importantly,the delocalized spin characteristics?semi-metallic metal spins?ensure a moderate bonding strength of the main reaction intermediates?*O₂,*O,*OH and*OOH?with the catalyst.Finally,the relationship between the atomic spin magnetic moment of the active center and the catalytic activity was established to provide guidance for the rational design of highly stable and highly active electrocatalysts.?2?Theoretical study of Zn-Co doped N coordination defect graphene as an electrocatalyst for ORR and OER reactions.The calculation of the formation energy indicates that it is negative only when x is greater than 3 for FeCoNx?x=1-6?embedded graphene?labeled as:FeCoN_x-gra?configuration,which shows thermodynamic stability.Among ZnCoN_x-gra?x=1-6?,ZnCoN₅-gra???exhibits best ORR catalytic performance with the overpotential of 0.42V.The ZnCoN₆-gra???exhibits potential bifunctional electrocatalyst for ORR and OER,the overpotentials of ORR and OER are 0.29V and 0.61V,respectively.In order to further improve its electrocatalytic performance,OH was used to modify the catalytic active center.The modified ZnCoN₆-gra???can show lower ORR and OER overpotentials of 0.25V and 0.52V,respectively,holding great promis as bifuncational catalyst.