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) TiO 2 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 O V and Ti 3+ . 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 O V and Ti 3+ can significantly reduce the Gibbs free energy of H* adsorption and desorption on the C,N/TiO 2 nanoparticles surface, promoting the kinetics of hydrogen evolution. Impressively, the optimal C,N/TiO 2 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 TiO 2 has no performance under visible light irradiation. This work will inspire the development and study of visible-light photocatalysts for photocatalytic hydrogen production.