Constructing a Stable 2D Layered Ti₃C₂MXene Cocatalyst-Assisted TiO₂/g-C₃N₄/Ti₃C₂Heterojunction for Tailoring Photocatalytic Bireforming of Methane under Visible Light

Fabrication of two-dimensional (2D) titanium carbide (Ti3C2) MXene nanosheets with a unique morphology coupled with a 2D g-C3N4/TiO2 heterojunction for hydrogen-rich syngas production during photocatalytic bireforming of methane (PBRM) under visible light has been investigated. The delaminated Ti3C2 layered nanosheets in the TiO2/g-C3N4/Ti3C2 heterojunction promoted charge-carrier separation efficiency by decreasing the traveling distance to reach the surface and increased the visible light absorption. The highest CO and H2 production of 48.38 and 83.2 μmol g-1 was achieved over g-C3N4/TiO2/Ti3C2, which is 5.17- and 9.85-fold higher compared to TiO2, respectively. The enhanced photoactivity can be attributed to the extension of visible light absorption, accelerated migration rates of the charge carrier, intimate contact, decreased traveling distance of excited electrons, and strong adsorption of reactants. In view of adsorption competition among the reactants, an optimized CO2/CH4 molar feed ratio of 1.0 promoted H2-rich syngas production. The apparent quantum yield (AQY) reached as high as 0.408 and 0.698% for CO and H2 production during the BRM process under visible light. The stability analysis further confirms high stability and durability of the composite catalyst in multiple cycles because of the presence of MXene sheets. This work provides new pathways to construct a low-cost and noble metal-free structured composite for stimulating photocatalytic BRM under visible light, which can be employed in solar energy applications.