Optimizing the adsorption of intermediates through modulating Mn d-band centers by the Mn-Ce heterojunction for high-performance lithium-oxygen batteries

Abstract

Admitting that rare-earth (RE)-based transition metal oxides (TMO) are emerging as a promising catalyst for lithium-oxygen (Li-O2) batteries, the understanding of their electrocatalytic mechanism and active sites remains ambiguous. In this study, CeO2 nanoparticles modified MnOOH nanowires (CeO2@MnOOH NWs) is prepared by a simple solvothermal method as highly effective cathode catalysts for Li-O2 batteries. The incorporation of CeO2 nanoparticles into MnOOH facilitates a robust interaction between the 3d electronic state of MnOOH and the 4f electronic state of CeO2 at the Fermi level (Ef). The strong electron interaction at the heterogeneous interface between MnOOH and CeO2 promotes internal electron transfer. Compared to pristine MnOOH, the prepared CeO2@MnOOH NWs exhibits enhanced electrocatalytic activity and improved electrocatalytic stability. According to experimental analysis and density functional theory (DFT) results, it is demonstrated that there is a slight negative shift in the d-band center of the Mn site, resulting in faster electron transfer rates and higher conductivity. This acceleration of charge transfer optimizes the adsorption strength of the oxygen-containing intermediate (LiO2), thereby promoting the kinetics of the oxygen reduction/evolution reactions (ORR/OER) and reducting the reaction over-potential. As a result, the electrochemical performances of Li-O2 batteries are greatly enhanced.