Ternary g-C3N4/TiO2/Ti3C2 MXene S-scheme heterojunction photocatalysts for NOx removal under visible light

Highly efficient composite photocatalysts were prepared through annealing partially oxidized Ti3C2 MXene with melamine under N2 flow. The two-dimensional Ti3C2 MXene was aforehand partially oxidized to form TiO2-Ti3C2 nanosheet by precisely controlling the oxidation conditions. Ternary g-C3N4/TiO2/Ti3C2 MXene photocatalyst was constructed by coating melamine derived g-C3N4 on TiO2-Ti3C2 nanosheet. The photogenerated electron-hole separation was significantly enhanced by the S-scheme heterojunction. Ti3C2 tightly bonded with TiO2 benefits transfer and aggregation of photo-induced holes. The composite material has an interconnected nanosheet structure, which increases the absorption of light and the reaction interface between gaseous reactant and photocatalysts. When evaluated as NOx purification photocatalysts, the fabricated composites get the high NO removal efficiency and low NO2 generation. Under visible light, NO removal efficiency of the composite photocatalyst can reach up to 66.3%, which is significantly better than the g-C3N4 or TiO2-Ti3C2. This work demonstrates that moderately oxidized Ti3C2 MXene is a good candidate for the construction of high-performance air purification photocatalysts.