Ru/In Dual-Single Atoms Modulated Charge Separation for Significantly Accelerated Photocatalytic H₂ Evolution in Pure Water

Photocatalytic hydrogen production is a prospective technology to solve the energy crisis and environmental problems. However, it is still challenging to produce hydrogen from photocatalytic water splitting on a large scale without a sacrificial agent and cocatalyst. Here, it is demonstrated that the dual doping of Ru/In single atoms on TiO₂ (Ru-In SA/TiO₂) can modulate the separation of photogenerated carriers during the photocatalytic splitting of pure water. Impressively, the H₂ evolution rate of Ru-In SA/TiO₂ reaches 174.1 µmol h⁻¹, which is 6, 18, and 53 times higher than those of the Ru single-atom decorated TiO₂, In single-atom decorated TiO₂, and pristine TiO₂, respectively. More importantly, Ru-In SA/TiO₂ outperforms most of the reported photocatalysts for photocatalytic water splitting in the absence of a sacrificial agent. Detailed investigations reveal that the decoration of Ru/In dual-single atoms leads to the remarkable increase of Ti³⁺ and enrichment of oxygen vacancies, which accelerate the charge separation. In particular, the femtosecond transient absorption spectroscopy suggests that the doping of Ru single atom promotes the transfer of photogenerated electrons from TiO₂ into Ru, while the doping of In single atom enhances the transfer of photogenerated holes from the TiO₂ valence band to In single atoms, as a result of an efficient electron-hole separation. This work not only provides an efficient photocatalyst for H₂ production through pure water splitting in the absence of a sacrificial agent, but also promotes fundamental research on catalyst design and modification.