Preparation of titanium dioxide/graphitic carbon nitride heterostructure anchored on hierarchical ZSM-5 for synergistic adsorptive and photocatalytic dye degradation

The formation of a heterojunction between two semiconductors is a promising strategy to enhance the photocatalytic activity of photocatalyst materials. In this work, TiO₂ and porous g-C₃N₄ anchored on the surface of hierarchical ZSM-5, namely TiO₂/g-C₃N₄@ZSM-5 composite material, shows enhanced photocatalytic activity toward degradation of methylene blue due to the synergistic effects between the heterojunction created by TiO₂ and g-C₃N₄ and the enlarged surface area provided by ZSM-5. Incorporating TiO₂ and porous g-C₃N₄ forms a Z-scheme heterojunction, which facilitates the charge carriers' transfer and suppresses charge recombination. Additionally, ZSM-5 contributes significantly by increasing surface area, which boosts the contact between the adsorbed dye molecules and the photocatalyst surface, and by promoting charge transfer. The specific surface area of TiO₂/g-C₃N₄@ZSM-5 is 98.6 m² g^-1, which is seven-fold higher than the bare porous g-C₃N₄ (14.0 m² g^-1). Photocatalytic activity test revealed that the TiO₂/g-C₃N₄@ZSM-5 composite reaches the highest degradation efficiency up to 98.3 % with the highest degradation rate of 0.0164 min^-1, which is much superior compared to bare porous g-C₃N₄ (50.3 % and 0.0030 min^-1), TiO₂/g-C₃N₄ (61.6 % and 0.0040 min^-1), and g-C₃N₄@ZSM-5 (90.2 % and 0.0095 min^-1). These results confirm that the synergistic effect between Z-scheme heterojunction formation and the high surface area are crucial factors in enhancing methylene blue degradation.