In-situ annealed “M-scheme” MXene-based photocatalyst for enhanced photoelectric performance and highly selective CO2 photoreduction

Methane (CH4) has superior economic value and application prospect compared with CO, and is an ideal product for photoreduction of CO2. However, low CO2 conversion efficiency and poor selectivity on production are both obstacles to its practical application. Herein, we develop a “M-scheme” photocatalyst CeO2/Ti3C2/TiO2 (CTT) for superior CO2 reduction and selective CH4 generation. This dual heterojunction is constructed by annealing precursor CeO2/Ti3C2 to form anatase TiO2 in situ. CTT composed by CeO2/Ti3C2 and TiO2/Ti3C2 significantly promotes the charge carrier transfer, improving its photoelectric performance. Ti3C2 exhibits a metallicity in the composite, which not only plays the role of a platform to receive transferred electrons, but also resembles the behavior of precious metals to assist in the decomposition of H2 molecules to H+. The reaction between H+ and CO on Ti3C2 contributes to the decreased by-products and decent CH4 selectivity. This work provides a facile and up-and-coming model to construct “M-scheme” heterojunction, realizing the megamerger between optimized photoelectric performance and selective CO2 photoreduction.