Surmounting the electronic paradox: A "push-pull" mediated Ru-Co₃O₄/FeOOH architecture for overall water splitting

A fundamental paradox in overall water splitting (OWS) lies in the conflicting electronic structure requirements for optimize hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Conventional design strategies often struggle to reconcile these competing demands within a single system, leading to compromised kinetic efficiency. Herein, we surmount this limitation by constructing an electronically coupled ruthenium-doped cobalt oxide/iron oxyhydroxide (Ru-Co₃O₄/FeOOH) architecture driven by a synergistic "push-pull" mechanism. In this configuration, cobalt oxide (Co₃O₄) acts as an electronic mediator, receiving electron injection from the iron oxyhydroxide (FeOOH) donor while simultaneously transferring electron density to the electron-withdrawing ruthenium (Ru) single atoms. This design transcends the mere aggregation of distinct HER- and OER-active sites; instead, through precise electronic redistribution, it creates dedicated, optimized electronic environments for each half-reaction. Under cathodic polarization, Ru acts as the primary HER center, where electron injection from FeOOH amplifies electron accumulation, thereby facilitating water dissociation and optimizing RuH binding strength to accelerate kinetics. Conversely, under anodic polarization, interfacial cobalt (Co) sites serve as the dominant OER centers, with Ru and FeOOH optimizing the local charge distribution to facilitate the transformation of oxygen-containing species. As a result, the Ru-Co₃O₄/FeOOH||Ru-Co₃O₄/FeOOH cell requires only 1.56 V to achieve 20 mA·cm^-2 while maintaining excellent long-term durability, highlighting mediated electronic coupling as a broadly applicable strategy for engineering bifunctional electrocatalysts with programmable electronic structures.