Well-designed V2AlC MAX supported g-C3N4/TiO2 Z-scheme heterojunction for photocatalytic CO2 reduction through bi-reforming to produce CO and CH4

Well-designed V2AlC MAX supported g-C3N4/TiO2 Z-scheme heterojunction was synthesized and tested for photocatalytic CO2 reduction through bi-reforming under UV and visible light in batch and continuous photoreactors. Compared to V2AlC/g-C3N4, V2AlC/TiO2 produced 2.17 times more CO and 6.40 times more CH4, along with H2. The highest CO production of 14644 μmol g−1 h−1 was obtained over V2AlC-g-C3N4/TiO2 composite at a selectivity of 20.21 %. Similarly, CH4 and H2 production of 56567 and 1253 μmol g−1 h−1 was obtained, which were 11.11 and 169.9 folds higher for CH4 and 2.77 and 2.32 folds higher for H2 production compared to using g-C3N4/TiO2 and V2AlC/TiO2, respectively. The efficient generation and separation of charge carriers were achieved by the Z-scheme heterojunction of g-C3N4/TiO2 with V2AlC MAX cocatalysts, which led to a greatly increased photocatalytic activity. Using a continuous process, the production of CO was decreased by 1.12 folds, whereas the production of methane disappeared and the reaction pathway was the conversion of CO2 to CO. Using methanol with UV light resulted in higher production of protons and hydrogen, achieving the highest quantum efficiency. The stability study further confirmed the continuous evolution of CO, CH4, and H2 over four cycles.