C,N Doped TiO₂ Nanoparticles with Abundant Surface Ti³⁺ and Oxygen Vacancies for Visible-Light Photocatalytic Hydrogen Production

Broadening the light absorption range and enhancing the surface activity of photocatalysts represent a pressing necessity for realizing visible-light photocatalytic hydrogen production. Here, the sol–gel method and microwave hydrothermal method were used to obtain C and N codoped (C,N codoped) TiO2 nanoparticles, which significantly improved their photocatalytic hydrogen production performance under visible light. The C,N codoping introduces impurity energy levels, which narrows the band gap and promotes visible-light absorption. More importantly, the C,N codoping also induces abundant surface OV and Ti3+. These defects can capture the photogenerated electrons, which promotes the separation of photogenerated carriers and enables electron transfer to the surface for the reduction of H*. Density functional theory (DFT) calculations confirm that the OV and Ti3+ can significantly reduce the Gibbs free energy of H* adsorption and desorption on the C,N/TiO2 nanoparticles surface, promoting the kinetics of hydrogen evolution. Impressively, the optimal C,N/TiO2 can achieve an average hydrogen evolution rate of 610 μmol g–1 h–1 under visible light (λ = 400 nm) and an apparent quantum yield of 1.05%, while pure TiO2 has no performance under visible light irradiation. This work will inspire the development and study of visible-light photocatalysts for photocatalytic hydrogen production.