Revisiting MXenes-based Photocatalysis Landscape: Progress, Challenges, and Future Perspectives

With the advancement of science and technology, traditional energy sources such as oil and coal have been extensively depleted, leading to the emission of greenhouse gases like CO 2 . Consequently, issues such as energy scarcity and drastic environmental changes have emerged as pressing concerns that threaten human survival and development. Photocatalysis offers a promising solution by harnessing solar energy for chemical energy conversion, yielding clean and sustainable products. It is widely regarded as an emerging approach to address the energy crisis and environmental challenges. To achieve high -efficiency photocatalytic reactions, the selection of appropriate catalysts and co -catalysts plays a pivotal role. However, conventional photocatalysts such as TiO 2 , CdS, and g-C 3 N 4 suffer from inherent limitations, including high charge recombination rates, low light utilization efficiency, poor stability, and sluggish charge transfer kinetics, which hinder the enhancement of photocatalytic efficiency. In this context, two-dimensional (2D) materials known as MXenes have gained prominence. These materials exhibit unique structural flexibility, diverse elemental compositions, superior conductivity, excellent carrier mobility, and abundant active sites, making them valuable co -catalysts in photocatalysis. MXenes accelerate interfacial charge transfer kinetics and mitigate charge recombination, enhancing the overall photocatalytic performance. This review provides a comprehensive overview of various methods employed to prepare high -quality MXenes under different conditions, such as water solution etching, water -free etching, and other physical methods. It also explores diverse strategies for constructing MXene-based composite photocatalytic systems, including in situ growth synthesis, in situ oxidation synthesis, and electrostatic selfassembly. Additionally, the review discusses various MXenes-based photosystems, such as MXene/TiO 2 , MXene/CdS, MXene/g-C 3 N 4 , MXene/WO 3 , and BiOBr/MXene/MMTex, and their applications in photocatalytic processes, including hydrogen production, CO 2 reduction, environmental remediation, nitrogen fixation, and sterilization. The critical role of MXenes as reduction co -catalysts in these photoredox catalysis reactions is thoroughly examined, along with an elucidation of the relationship between MXene electronic structure and charge transfer characteristics. Furthermore, the review addresses the challenges related to the stability of MXenes in photocatalytic reactions and offers insights into potential strategies to mitigate this issue. Finally, the development prospects and future challenges of MXene-based composites in the field of photocatalysis are presented, taking into consideration the inherent limitations of MXenes and the requirements for industrialization. It is expected that this review will provide valuable insights into the physicochemical properties of MXenes and inspire innovative approaches to the rational design of diverse MXene-based photosystems for heterogeneous photocatalysis across various applications.