Regulated-valence Pt^δ+ sites on self-reconstructed CoO shell-enriched Co₂P/Co₉S₈ heterostructure nanoarray for robust anion exchange membrane water electrolyzer

Anion exchange membrane (AEM) water electrolyzer offers a promising route to low-cost and sustainable green hydrogen production. However, their sluggish alkaline hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics remain key challenges due to the lack of efficient electrocatalysts. We report a highly efficient and robust electrocatalyst by confining single-site Pt with positively charged pieces on a hybrid nanoarray of Co₂P/Co₉S₈ heterostructure shelled by CoO nanosheets (Co₂P/Co₉S₈@CoO-Pt_SA). This catalyst demonstrates low overpotentials of 29.6 and 268.8 mV to achieve 10 mA cm⁻² for HER and OER in 1.0 M KOH, respectively. Additionally, a single cell AEMWE assembled with this catalyst achieves 0.5/1.0 A cm⁻² at 1.84/2.01 V in 1.0 M KOH at 60 °C and displays excellent durability for 2000 h at 0.5 A cm⁻². Pt cation-exchange coordination induces self-reconstruction of Co₂P/Co₉S₈ nanoarray, forming a stable CoO nanosheets that increase surface area and exposes more active sites. Experimental and theoretical findings confirm that the Pt_SAs donate electrons to Co sites through interfacial bridging, leading to positive valent Pt^δ+ sites that optimize the adsorption-desorption balance of reaction intermediates. The study provides a novel strategy to boost electrochemical performance synergistically through rational design and electronic modulation of advanced single-site catalysts.