Engineering space dimension and surface chemistry of MXene-based nanocomposite photocatalysts for sustainable environmental applications.

It is very urgent to solve the environmental pollution problem. MXene-based composite photocatalysts show great promise, and utilize solar energy for purification. MXenes have excellent electrical conductivity, a large surface area due to their 2D structure, and surface functional groups beneficial for photocatalysis. In this review, various synthesis methods to prepare MXenes with different properties for specific applications have been reviewed, such as hydrofluoric acid etching, substitute etching and molten fluoride etching. The influence of different groups on the performance of MXenes has been investigated. Modification strategies including heterojunction construction, doping, precious metal deposition and single atom anchoring have been explored to enhance the photocatalytic performance of MXene-based composites in photocatalytic reactions. It is found that MXenes can act as supports that limit photocatalyst size, enhance reactant adsorption, and function as cocatalysts loaded onto semiconductors to improve charge separation. Our perspectives on the key challenges and future directions of developing high-performance MXene-based composite photocatalysts for environmental applications are elaborated.