Atomically Dispersed Co–P Moieties via Direct Thermal Exfoliation for Alkaline Hydrogen Electrosynthesis

The development of highly active and stable cathodes in alkaline solutions is crucial for promoting the commercialization of anion exchange membrane (AEM) electrolyzers, yet it remains a significant challenge. Herein, we synthesized atomically dispersed CoP4 moieties (CoP4–SSC) immobilized on ultrathin carbon nanosheets via a phosphidation exfoliation strategy at medium temperature. The thermodynamic formation process of the Co–P moieties was elucidated using X-ray absorption spectroscopy (XAS) and theoretical calculations. Remarkably, the resulting CoP4–SSC electrocatalyst exhibited outstanding activity for alkaline hydrogen evolution, with a low overpotential of 52 mV at 10 mA cm–2 and a turnover frequency of up to 23.83 s–1. Moreover, the AEM electrolyzer fabricated with CoP4–SSC achieved a current density of 1 A cm–2 under an applied voltage of only 1.94 V, showing negligible degradation after 500 h of continuous electrocatalysis. A series of operando characterizations and density functional theory calculations revealed that the atomically dispersed Co–P moieties formed a nanointerface of [P-*H···H2O*-Co], which facilitates water dissociation during the Volmer–Heyrovsky pathway.