Preparation of Al-O-Linked Porous-g-C₃N₄/TiO₂-Nanotube Z-Scheme Composites for Efficient Photocatalytic CO₂ Conversion and 2,4-Dichlorophenol Decomposition and Mechanism

The photocatalytic activity of TiO₂ nanotubes can be improved through the construction of a Z-scheme composite, where photogenerated electrons from TiO₂ recombine with the photogenerated holes in a coupled semiconductor. This arrangement allows for improved oxidation due to the residual holes of TiO₂ and better chemical reduction due to the greater availability of the photogenerated electrons of the coupled semiconductor. Efficient Z-scheme porous-g-C₃N₄/TiO₂-nanotube (PCN/TNTs) composites were developed here using a solid sublimation and transition approach, with Al-O links added by an impregnation method to increase interfacial linkages between the PCN and TNTs. The best results for photocatalytic CO₂ conversion were obtained using 0.7PCN/0.4Al/TNTs, as shown by production of 54.9 ± 0.70 mg L^-1 h^-1 of acetic acid, 42.7 ± 0.54 mg L^-1 h^-1 of formic acid, and 45.4 ± 0.55 mg L^-1 h^-1 of methanol, which were about 3.8, 4.3, and 4.2 times that produced with bare TNTs. Photocatalytic 2,4-dichlorophenol decomposition with 0.7PCN/0.4Al/TNTs showed a 40% enhancement compared to bare TNTs in 1.5 h. This Z-scheme composite photocatalyst therefore provides an improved method for more efficient CO₂ conversion or pollutant degradation based on the improved charge separation and linkage of the PCN/TNTs using Al-O.