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

Abstract 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 Pt 2+ inhibits H 2 /O 2 recombination. However, simultaneously leveraging the advantages of Pt 0 and Pt 2+ 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 Pt 2+ /Pt 3 and a close to zero proton reduction barrier, along with isolated O 2 adsorption. As a proof of concept, Pt undergoes electron transfer to ZnIn 2 S 4 , accompanied by partial oxidation from Pt 0 to Pt 2+ through the introduction of electron‐deficient centers in ZnIn 2 S 4 via vanadium doping and sulfur vacancy (V‐Sv‐ZIS). Reverse electron transfer induces Pt 2+ dominating 83% of the region near the Pt/V‐Sv‐ZIS interface and Pt 0 dominating in the remaining 17% near the Pt cluster center, which can be extended to other Pt‐based catalyst systems. The dominant Pt 2+ inhibits O 2 adsorption and induces the lowest H 2 /O 2 recombination rate of 4%, and the minimal Pt 0 obtains a 152.2‐fold increase in photogenerated electron density, ultimately realizing a 45.4‐fold increase in photocatalytic activity. A 10 m 2 large‐area photocatalytic system is fabricated, producing 6.4 L of H 2 per day under natural sunlight.