High-valent nickel oxyhydroxides self-derived through a low-temperature thermochemical strategy for an efficient...

High-valent Ni(Fe) metals are considered practical electroactive phases that can accelerate reaction kinetics and exhibit high inherent reactivity during the alkaline oxygen evolution reaction (OER). However, their formation and stabilisation are thermodynamically unfavourable. Oxyanions possess a unique polyanionic motif and suitable electronegativity, enabling them to share more dispersed electrons with adjacent metal cations and thereby balance the strong positive electronic fields of the metal cations. This characteristic offers a more favourable approach to modulate surface self-reconfiguration compared with conventional metal cation or non-metal anion modifications. Based on this, herein, an oxysulfide anion regulation method is proposed to obtain stable high-valent Ni(Fe) phases. The oxysulfide anion can be directly pre-anchored onto a Ni(Fe) oxyhydroxide sea-urchin array catalyst by simply treating the commercial NiFe foam in a low-temperature reaction medium of ammonium persulfate and water. The pre-bonded oxysulfide can effectively tailor the electronic energy level of electroactive sites (e.g. oxidation-state engineering, band gap narrowing, metal-O covalency and metal d-band centre), thereby altering the surface charge transfer rate to further enhance the adsorption, conversion and desorption of OER intermediates. Ultimately, the OER kinetics is accelerated, and the persistent *OH-*OOH scaling relationship can be overcome to reduce the overpotentials. The final catalyst achieves superior OER performance with a low overpotential of 219 mV at 10 mA cm^-2, rapid kinetics (54.1 mV/dec) and prominent durability of >693 h to maintain the initial current density of 100 mA cm^-2. Informative insights into both simple low-temperature thermochemical oxysulfide modulation protocol and sulfate-tuned roles in improving OER activity could broaden the understanding of the oxyanion effect in electrocatalysis and provide a rational approach for designing cutting-edge electrocatalysts for practical applications.