Pt Single-Atom Doping in Ag29 Nanoclusters for Enhanced Band Bending and Z-Scheme Charge Separation in TiO2 Heterojunction Photocatalysts

In recent years, metal nanoclusters (NCs) with atomic-scale precision have emerged as novel photosensitizers for light energy conversion in metal cluster-sensitized semiconductor (MCSS) systems. However, conventional NCs often suffer from photodegradation after binding with semiconductors, limiting their long-term catalytic stability. Modifying NCs via single-atom doping provides an effective strategy to tailor their interfacial charge transfer behavior. In this study, PtAg28 NCs were synthesized by doping Pt single atoms into Ag29 NCs and subsequently loaded onto TiO2 via electrostatic adsorption to construct composite photocatalysts. Systematic investigations revealed that Pt doping significantly enhances light absorption and promotes the formation of a direct Z-scheme heterojunction. The optimized PtAg28/TiO2 composite exhibits effective suppression of charge recombination. This enhanced charge separation efficiency, driven by pronounced band bending at the interface, leads to a remarkable hydrogen evolution rate of 14,564 μmol g−1 h−1. This work demonstrates the critical role of single-atom doping in regulating the photophysical properties of metal NCs and offers a feasible approach for designing highly efficient and stable metal-cluster-based photocatalytic systems.