Role of surface morphology and terminating groups in titanium carbide MXenes (Ti3C2Tx) cocatalysts with engineering aspects for modulating solar hydrogen production: A critical review

Hydrogen production through photoinduced water splitting is regarded as one of the best alternatives in providing clean and renewable energy sources. Recently, MXene as co-catalysts are considered promising green structured materials to replace expensive noble metals to promote both efficiency and photostability. The utilization of titanium carbide (Ti3C2Tx) MXene as a co-catalyst has shown great promise for assisting solar to hydrogen conversion owing to their structural flexibility, surface morphological, and tailorable termination groups. The surface functional groups, morphological developments and engineering aspects are important factors to optimize Ti3C2Tx as the best co-catalyst in solar energy applications. This review provides recent advances in morphological design of Ti3C2Tx MXene with critical analysis on the role of termination groups for promoting photoactivity and products selectivity. A deep focus is given to the engineering design of Ti3C2Tx MXene with special regard to quantum dots, monolayer, and hierarchical structures. Firstly, the general overview of Ti3C2Tx MXene is introduced with insights into their catalytic properties and formation of surface termination groups to gain profound understanding of their basic catalytic structure. Next, the effects of tailoring the morphology of Ti3C2Tx MXene into 2D accordion-like structure, monolayer, hierarchical, quantum dots, and nanotubes structure to expedite their role to promote solar-based photoactivity are critically discussed. In addition, specific considerations are given on the effects of reaction parameters, challenges, and synthesis strategies for tailoring the morphology of Ti3C2Tx MXene with controlled functional groups. Finally, future perspectives are provided for the potential use of Ti3C2Tx MXene as green materials in reaction engineering and environment applications.