A Near‐Perfect Pt Cocatalyst with a Spatially Oriented Distribution of Pt ²⁺ /Pt ⁰ for Photocatalytic Water Splitting

Loading the cocatalyst, e.g., Pt, is a promising strategy for photocatalytic overall water splitting, in which metallic state Pt° facilitates proton reduction and positive valence state Pt²⁺ inhibits H₂/O₂ recombination. However, simultaneously leveraging the advantages of Pt⁰ and Pt²⁺ in Pt-photocatalyst hybrids for photocatalytic water splitting is challenging. Herein, a universal strategy is demonstrated for modulating Pt valence state, obtaining a spatially oriented distribution of Pt²⁺/Pt³ and a close to zero proton reduction barrier, along with isolated O₂ adsorption. As a proof of concept, Pt undergoes electron transfer to ZnIn₂S₄, accompanied by partial oxidation from Pt⁰ to Pt²⁺ through the introduction of electron-deficient centers in ZnIn₂S₄ via vanadium doping and sulfur vacancy (V-Sv-ZIS). Reverse electron transfer induces Pt²⁺ dominating 83% of the region near the Pt/V-Sv-ZIS interface and Pt⁰ dominating in the remaining 17% near the Pt cluster center, which can be extended to other Pt-based catalyst systems. The dominant Pt²⁺ inhibits O₂ adsorption and induces the lowest H₂/O₂ recombination rate of 4%, and the minimal Pt⁰ obtains a 152.2-fold increase in photogenerated electron density, ultimately realizing a 45.4-fold increase in photocatalytic activity. A 10 m² large-area photocatalytic system is fabricated, producing 6.4 L of H₂ per day under natural sunlight.