Abstract:
Photocatalytic CO
2 reduction to CH
4 over titanium dioxide (TiO
2) is thermodynamically feasible, but it is restricted by core shortcomings such as low light utilization, rapid recombination of photo-generated charge carriers, and poor product selectivity. Therefore, developing high-performance TiO
2-based photocatalysis remains a critical challenge. In this work, using Ti
3C
2 MXene as raw materials and template, the in situ growth of TiO
2 nanoparticles on Ti
3C
2 MXene was synchronously coupled with methylene blue (MB) to successfully fabricate the TiO
2/Ti
3C
2/MB (TTM) composites via one-step ultrasonic method for photocatalytic CH
4 generation. The resulting TTM composites display the accordion-like layered structure, and the introduction of MB narrows band gap, boosts CO
2 adsorption capacity, and induces the formation of small-sized TiO
2 nanoparticles. The optimized TTM sample (TTM-0.20) displays the CH
4 yield rate of 54.34 μmol·g
−1·h
−1, surpassing accordion-like TiO
2 and TiO
2/Ti
3C
2 composite by 12.9 and 3.1 folds, and achieves a 96.1% CH
4 selectivity. The enhanced photocatalytic performance may be attributed to the improved visible light utilization by the MB photosensitizer, the accelerated separation and transfer of photo-generated charge carriers through the tight Schottky junction and multiple tight interfaces, and effective capture of CO
2 molecules along with the stabilization of reaction intermediates at Ti
3C
2 MXene reactive sites. By employing dye-sensitization and heterojunction strategies, the TiO
2/Ti
3C
2/MB ternary composite was successfully constructed. The synergistic effect of multiple components achieves highly selective photoconversion of CO
2 to CH
4, providing a new approach for CO
2 resource utilization.