Cu@Cr 2 O 3 Noble‐Metal‐Free Hydrogen‐Evolving Cocatalyst on Al‐Doped SrTiO 3 for Photocatalytic Overall Water Splitting

ABSTRACT The development of noble‐metal‐free cocatalysts is crucial for low‐cost photocatalytic overall water splitting (POWS) systems. However, dynamic structural evolution of non‐noble‐metal materials under operando conditions results in a restricted activity of cocatalysts in POWS. Herein, we construct a core–shell structured Cu@Cr 2 O 3 cocatalyst on Al‐doped SrTiO 3 (SrTiO 3 :Al) via a photodeposition method (denoted as Cu‐PD/STO) for efficient H 2 evolution in POWS. The Cu‐PD/STO achieves the H 2 evolution rate of 788.7 µmol/h, surpassing all the recently reported noble‐metal‐free H 2 evolution cocatalysts on SrTiO 3 for POWS. Quasi in situ/ operando characterizations elucidate the stable operation of Cu 0 active sites in POWS, guaranteed by the photoinduced reduction of Cu sites and core–shell structure. Further characterizations and theoretical calculations reveal that Cu 0 active sites provide accelerated electron extraction from SrTiO 3 :Al, optimized water dissociation, and hydrogen adsorption. Moreover, Cu 0 active sites can promote the formation of Cr 2 O 3 shells, which encapsulate the Cu 0 active sites, protecting them against surface oxidation and suppressing the reverse reaction in POWS.