Tuning the charge distribution of Co–N–C active sites for enhanced trifunctional electrocatalysis

Abstract

Previous studies have often focused on optimizing electrocatalytic performance by altering the type of metal centers or the morphological structure of catalysts to modulate their electronic structures and active sites. However, the precise regulation of metal valence states to enhance catalytic performance—particularly for trifunctional electrocatalysis in the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER)—remains in the exploratory stage. In this study, crystalline Co–N₆ materials with controllable valence states were carefully selected as precursors. Through carbonization, Co–N–C materials with similar carbon frameworks but distinct metal valence states (Co²⁺ and Co³⁺) were successfully prepared. Both experimental tests and theoretical calculations demonstrate the superior trifunctional electrocatalytic performance of Co²⁺–N–C. Density functional theory (DFT) calculations provide evidence for the more favorable intermediate adsorption energies and lower reaction energy barriers exhibited by Co²⁺–N–C. This performance advantage stems from the 3d⁷ electronic configuration of Co²⁺, which optimizes electron cloud density and strengthens Co–N bonding interactions. This work presents a new strategy for designing highly efficient electrocatalysts by elucidating the regulatory role of metal valence states.