Rare earths evoked gradient orbital coupling in electrocatalysis: Recent advances and future perspectives

Rare earths (RE) have garnered significant attention in electrocatalysis due to their unique ability to modulate electronic structure of host materials. The gradient orbital coupling (GOC) based on f-p-d orbital interaction has recently been proposed to explain the key reason for RE-enhanced electrocatalysis. However, a systematic review elaborating the critical role of GOC in electrocatalysis remains lacking. Herein, this review presents a timely and comprehensive summary of GOC breakthroughs in RE-based electrocatalysts and highlights their key role in electrocatalysis. It begins by introducing the fundamentals of GOC. We further discuss the most recent progress in tuning the electronic state of metal active centers by GOC for various electrocatalytic reactions including oxygen electrocatalysis, hydrogen evolution, carbon dioxide reduction, nitrogen oxidation and urea oxidation. From GOC insight, this discussion of electrochemical performances and intrinsic catalytic mechanisms favors the construction of RE-evoked structure-performance relationship. At the end, we discuss the challenges and potential future directions for research related to the GOC. We hope this review will inspire novel designs and a deeper understanding of RE-based electrocatalysts.