Palladium Hydride Anchored on SrTiO₃ with Efficient Charge Separation and Surface Reaction Kinetics for Enhanced Photocatalytic Overall Water Splitting

Cocatalyst engineering is critical for advancing photocatalysis, as it suppresses charge carrier recombination, promotes interfacial electron/hole extraction, and serves as active sites for redox reactions. However, the incompatibility existing between the cocatalyst and host photocatalyst, along with its intrinsic properties of active sites, limits further improvements in the charge separation, surface reaction kinetics, and overall performance. Herein, we introduce palladium hydrides (PdH_<i>x</i>) as an efficient cocatalyst on SrTiO₃ (STO) for photocatalytic overall water splitting, owing to their similar lattice parameters. The constructed PdH_<i>x</i>/STO demonstrates a remarkable 6.4-fold enhancement in hydrogen evolution compared to the Pd/STO control, reaching a rate of 5 mmol·g^-1·h^-1 at a stoichiometric H₂/O₂ ratio of 2:1. Structural characterizations and theoretical analyses prove that the <i>in situ</i> formed PdH_<i>x</i> sites feature the advantages of accelerated electron extraction and modulated hydrogen adsorption energies for hydrogen evolution; femtosecond transient absorption spectroscopy further reveals prolonged charge carrier lifetime and improved charge transfer efficiency.