Spin-Modulated Oxygen Electrocatalysis

The electrocatalysis reactions involving oxygen,such as oxygen evolution reaction(OER)and oxygen reduction reaction(ORR),play a critical role in energy storage/conversion applications,e.g.,fuel cells,metal-air batteries,and electrochemical water splitting.The high kinetic energy barrier of the OER/ORR is highly associated with the spin state interconversion between singlet OH^(−)/H_(2)O and triplet O_(2),which is influenced by the spin state and magnetism of catalysts.This Review summarizes recent progress and advances in understanding spin/magnetism-related effects in oxygen electrocatalysis to develop spin theory.It is demonstrated that the spin states(low,intermediate,and high spin)of magnetic transition metal catalysts(TMCs)can directly affect the reaction barriers of OER/ORR by tailoring the bonding of oxygen intermediates with TMCs.Besides,the spin states of TMCs can build a spin-selective channel to filter the electron spins required for the single/triplet interconversion of O species during OER/ORR.In this Review,we introduced many approaches to modulating spin state,for instance,altering the crystal field,oxidation state of active-site ions,and the morphology of TMCs.What’s more,a magnetic field can drive the spin flip of magnetic ions to achieve the spin alignment(↑↑)(i.e.,facilitating spin polarization),which will strengthen the spin selectivity for accelerating the filtration and transfer of the spins with the same direction for the generation and conversion of triplet ↑O=O↑.Importantly,the origin of magnetic field enhancement on OER/ORR are deeply discussed,which provides a great vision for the magnetism-assisted catalysis.Finally,the challenges and perspectives for future development of spin/magnetism catalysis are presented.This Review is expected to highlight the significance of spin/magnetism theory in breaking the bottleneck of electrocatalysis field and promote the development of high-efficientcy electrocatalysts for practical applications.