Synergistic Effect of the V₂CT_x MXene@V₂O₅/TiO₂ NP Composite for Stimulating Photocatalytic CO₂ Reduction through Bireforming of Methanol to Produce CO and CH₄

Vanadium carbide (V₂C) MXene, a transition metal, exhibits significant potential as an innovative cocatalyst to enhance photocatalytic efficiency. In this study, we explored the construction of a self-assembled V₂C@V₂O₅/TiO₂ composite through the sol-gel method, incorporating in situ grown vanadium oxide (V₂O₅) with TiO₂. Efficient charge carrier separation was achieved owing to the higher conductivity, abundant active sites, and higher light absorbance. When V₂C@V₂O₅/TiO₂ was employed with a methanol-water mixture, the resulting CO and CH₄ production reached remarkable amounts of 20 075 and 17 567 μmol g^-1 h^-1, respectively. This represented a substantial enhancement in photocatalytic efficiency compared to using water/H₂ sacrificial reagents and pure TiO₂ nanoparticles. This enhanced photoactivity in the presence of methanol was attributed to efficient photoinduced carrier separation, facilitated by the synergistic effect of V₂C/V₂O₅ and increased proton production. Moreover, the performance of the V₂C MXene-based composite for CO, CH₄, and H₂ formation was 1.45, 52.75, and 1.35 times higher, respectively, than that achieved with the V₂AlC MAX-based TiO₂ composite. The advantages of V₂C conductivity and its two-dimensional layered structure contributed to achieving higher photocatalytic efficiency compared to using the MAX structure. The maximum quantum yield of 9.7, 8.488, and 0.352% for CO, CH₄, and H₂, respectively, was achieved over the V₂C@V₂O₅/TiO₂ composite with continuous photoactivity with consecutive cycles. This study not only demonstrates the promising prospects of V₂C MXenes but also introduces an innovative approach for designing and fabricating highly efficient and stable photocatalytic systems for CO₂ recycling, with potential applications in various energy-related fields.