Electron Shuttling of Ni–Phosphate–Co Bridging Enables the Bidirectional Valence Modulation for Superior and Ultralong Water Splitting for Sustainable Green Hydrogen Production

The high-energy barrier and sluggish kinetics hinder the conversion efficiency of electrocatalytic water splitting. These limitations can be mitigated by modulating the valence states of active sites in nonprecious metal catalysts. However, achieving the synchronous but opposite valence regulation of different metals in multicomponent electrocatalysts remains a formidable challenge, especially when using one-pot synthesis methods. Here, we propose a phosphate anion modification strategy to endow the self-supporting NiCo materials (NiCoP@NF) with efficient water-splitting performance. The phosphate species, amply incorporated via one-step electrodeposition, form Ni–phosphate–Co-bridging motifs in which phosphate anions serve as efficient electron conducting pathways, rapidly shutting electrons from Ni to Co. Experimental analysis and theoretical calculations reveal that this electron shuttling effect induces the electron delocalization and redistribution around Ni and Co centers, simultaneously triggering the low valence state of Co and the high oxidation state of Ni in the integrated NiCoP@NF catalyst. The valence-modulated metal sites own the rapid hydrogen diffusion speed and deprotonation rate, obviously diminishing the energy cost for the phase transformation of Ni2+/3+ into high valent Ni3+σ/3+ as active oxygen evolution reaction (OER) phases, inducing the high-level nonconcerted proton electron transfer process during OER. Finally, NiCoP@NF exhibits excellent bifunctional electrocatalytic performance, with a low overpotential of 50.2 mV for hydrogen evolution reaction (HER) and an overpotential of 240 mV for OER at 10 mA cm–2. It also demonstrates great durability, maintaining an industrial current density of 1 A cm–2 for ultralong 10,127 h stability, showing competitive performance compared to most reported catalysts. Our study not only validates an effective valence regulation strategy in the mixed metal materials for achieving superb bifunctionality but also provides new insights into designing robust multinary transition metal electrocatalysts via oxyanion-induced electron bridging, offering promising prospects for industrial applications.