N-doping of TiO₂ for enhanced CO₂ photocatalytic reduction and research on reaction mechanisms

Photocatalytic reduction of CO₂ into fuels offers a promising avenue to tackle present energy challenges and mitigate global warming. At present, TiO₂ has been widely used in photocatalytic CO₂ reduction reactions, and element doping can optimize the band structure of TiO₂ to improve the efficiency of photocatalytic CO₂ reduction. In this work, TiO₂ doped with different content of N was prepared using TiN as the precursor through a simple one-step calcination method. Under optimized conditions, the optimal CO yield of the modified photocatalyst is 41.1 μmol g⁻¹ h⁻¹, which is 8 times higher than that of p25 type TiO₂. Density functional theory (DFT) calculations confirmed that N-doping can reduce the band gap of TiO₂ and decrease the Gibbs free energy of CO₂ reduction reaction. In-situ-XPS indicated that N-doping can enhance the activation of CO₂ by enriching photo generated electrons. Additionally, In-situ-FTIR spectra were employed to detect intermediates and track variations in the consumption of H₂O and CO₂, providing deeper insights into the mechanism responsible for enhancing efficiency. Our work addresses the deficiencies of the past and provides more detailed theoretical insights for the accelerated photocatalytic reduction of CO₂ by N-doping TiO₂.