Interstitial N-Doped TiO₂ for Photocatalytic Methylene Blue Degradation under Visible Light Irradiation

Photocatalysis is a promising method for methylene blue (MB) degradation due to its effectiveness and environmental compatibility. Among the photocatalysts, titanium dioxide (TiO₂) has been widely used for MB degradation due to its exceptional photocatalytic activity. However, the wide bandgap limits the degradation efficiency of TiO₂ under visible light. Here, an interstitial nitrogen-doped TiO₂ (5%N_T/TiO₂) used thiourea as the N source was fabricated for visible light-derived MB degradation. The 5%N_T/TiO₂ exhibited an extended absorption range of visible light. Moreover, photoelectrochemical measurements showed an improvement in the photocurrent response and charge transfer behavior on N/TiO₂. Thus, 5%N_T/TiO₂ had enhanced photocatalytic activity compared with pristine TiO₂ and substitutive N-doped TiO₂ (5%N_AB/TiO₂). The accelerated photocatalytic MB degradation process on N/TiO₂ could be mainly attributed to the interstitial N doping, which caused the appearance of new energy states and extended optical properties. Through comparing the impact of interstitial and substitutive in TiO₂ activity, our work proposes a suitable form of element doping to enhance the optical properties and photocatalytic activity of TiO₂ and even other semiconductors, providing guidance for future work.