An in situ spectroscopic study of 2D CuS/Ti3C2 photocatalytic CO2 reduction to C1 and C2†

The construction of heterojunctions is an effective strategy to improve the photogenerated carrier mobility rate and enhance the photocatalytic performance. The main bottlenecks in developing semiconductor photocatalysts lie in the poor light absorption and the fast recombination of photogenerated electron–hole pairs. In order to enhance the photocatalytic conversion of CO₂, in this work, a kind of 2D/2D CuS/Ti₃C₂ heterostructure nanocomposites were designed. The formation of the heterojunction structure resulted in a significant enhancement of the light absorption range in the visible region of pristine Ti₃C₂ and a slight increase in the semiconductor bandgap width (2.58 eV), which in turn increased the generation of photogenerated electron–hole pairs and facilitated the acceleration of the carrier mobility efficiency, leading to a substantial improvement of the photocatalytic activity. After controlling the molar ratio of CuS/Ti₃C₂ at the optimum value of 1 : 8, the photocatalytic CO₂ reduction conversion rate was the highest in the absence of co-catalysts. The yields of CO and CH₄ were 10.68 and 25.21 μmol g⁻¹ h⁻¹, respectively, and were 5.51 and 3.15 times higher than that of pristine Ti₃C₂. Moreover, it resolved the bottleneck of the single CuS reduction product being only CO. In addition, the CuS/Ti₃C₂ (1 : 8) photocatalyst exhibited 35.07% selectivity and a C₂H₄ yield of 10.05 μmol g⁻¹ h⁻¹. The presence of large amounts of C1 and C2 intermediates on the catalyst surface was observed by in situ FTIR. Notably, after a cycling stability test lasting 40 h, the best samples retained 88.8% of the initial efficiency with good stability. This study further elucidates the mechanism of action and synergistic effects of CuS and Ti₃C₂ semiconductors in enhancing photoactivity.