Epitaxial growth of TiO2 nanoparticles on Ti3C2 MXene for dye-sensitized photoconversion of CO2 into CH4

Photocatalytic CO2 conversion has been deemed as a green and sustainable strategy to alleviate energy crisis and mitigate greenhouse effect. Efficient and high selective CO2 photoconversion into CH4 still remains a challenge. In this work, the epitaxial growth of TiO2 nanoparticles on Ti3C2 MXene was synchronously coupled with the modification of methylene blue (MB) to successfully fabricate the TiO2/Ti3C2/MB (TTM) composites via one-step ultrasonic method. The resulting TTM composites display the accordion-like layered structure embellished with nanoparticles with a large surface area and narrow band gap. Excitingly, the optimized TTM achieves a prominent near 100% CO2-to-CH4 photoconversion with a yield rate of 54.34 μmol·g-1·h-1, surpassing accordion-like TiO2 (AT) by 12.9 folds. As revealed by characterizations, MB behaves as photosensitizer to transfer more excited electrons to TiO2 and Ti3C2 through the tightly packed multi-component interfaces. Ti3C2 MXene serves as active sites to strongly capture CO2 molecules and stabilize reaction intermediates for the highly selective CH4 generation. And the multiple charge transfer pathways are established to greatly separate and transfer photo-induced charge carriers. This work highlights the feasible design of TiO2-based photocatalysts, which not only achieves the effective removal of MB pollutant but also effectuates highly selective CO2-to-CH4 conversion.