Synergistic thermodynamic-kinetic tuning of spinel oxides achieve robust seawater hydrogen evolution reaction

Metal oxides exhibit low electrocatalytic hydrogen evolution activity, limiting their practicality as precious-metal replacements. While conventional methods focus on modulating thermodynamic adsorption/desorption barriers, reactive kinetics and intermediates concentration at the electrical double layer are equally critical. Here, an electrochemical in-situ leaching strategy is developed to precisely optimize the thermodynamic-kinetic interplay in spinel oxides, achieving Pt-like activity. Using ZnFe₂O₄ as a model, leaching of A-site Zn²⁺ triggers reconstruction from tetrahedral FeO₄ to octahedral FeO₆, forming adjacent Fe³⁺-Fe³⁺ dual centers. Thermodynamically, this structure optimizes the *H adsorption energy and lowers the energy barrier for splitting *H₂O to *H. Kinetically, it weakens the interfacial hydrogen-bond network at the outer Helmholtz plane, thereby boosting H₂O adsorption/dissociation and enriching *H at the inner Helmholtz plane. This thermodynamic-kinetic interplay shifts the reaction pathway from Volmer-Heyrovsky to the faster Volmer-Tafel process, delivering Pt-like activity and stability even in seawater. Furthermore, A-O bond strength and the electron occupancy of the A-site metal's outer d-orbitals are related to spinel activation. This work offers a novel strategy for designing efficient non-precious-metal electrocatalysts and deepens insight into spinel oxide structure-property relationships.