Dynamic modulation of Pt 5d valence electrons by single-atom Cu for boosted alkaline hydrogen evolution catalysis

Developing efficient and durable alkaline hydrogen evolution reaction (HER) catalysts is crucial for realizing high-performance, practical anion exchange membrane water electrolyzer (AEMWE) operating at ampere-level current densities. Although atomically dispersed Platinum (Pt) catalysts offer significant potential for enhancing atom utilization, their HER performance and durability are limited by the inflexibility in valence electron transfer between Pt and the support. In this study, we utilize asymmetrically single-atom copper (Cu) with tunable valence states as a valence electron reservoir (VER) to dynamically regulate the Pt 5d valence states, achieving efficient alkaline HER. In situ synchrotron radiation and theoretical calculations demonstrate that the dynamic evolution of the Pt 5d valence electron configuration optimizes the adsorption strengths of reaction intermediates. Meanwhile, single-atom Cu accelerates the rate-limiting water dissociation, and Pt facilitates subsequent *H coupling. The catalyst requires only 23.5 and 177.2 mV overpotentials to achieve current densities of 10 and 500 mA cm⁻² in 1 M KOH. Notably, the PtCu/NC exhibits a ∼57 % lower hydrogen evolution barrier than Pt/NC. Moreover, the PtCu/NC-based AEMWE operates for over 600 h at an industrially relevant current density of 500 mA cm⁻².