Preparation of Al–O-Linked Porous-g‑C 3 N 4 /TiO 2 ‑Nanotube Z‑SchemeComposites for Efficient Photocatalytic CO 2 Conversionand 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.