The separation of photogenerated carriers and photocatalytic hydrogen production efficiency was greatly enhanced by the 2D/2D heterojunction of Ti₃C₂/g-C₃N₄.

Constructing an efficient photoelectron transfer channel to promote the charge carrier separation is a great challenge for enhancing photocatalytic hydrogen evolution from water. In this work, an ultrathin 2D/2D Ti₃C₂T_x/ZnIn₂S₄ heterostructure is rationally designed by coupling the ultrathin ZnIn₂S₄ with few‐layered Ti₃C₂T_x via the electrostatic self‐assembly strategy. The 2D/2D Ti₃C₂T_x/ZnIn₂S₄ heterostructure possesses larger contact area and strong electronic interaction to promote the charge carrier transfer at the interface, and the sulfur vacancy on the ZnIn₂S₄ acting as the electron trap further enhances the separation of the photoinduced electrons and holes. As a consequence, the optimal 2D/2D Ti₃C₂T_x/ZnIn₂S₄ composite exhibits a high photocatalytic hydrogen evolution rate of 148.4 µmol h⁻¹, which is 3.6 times and 9.2 times higher than that of ZnIn₂S₄ nanosheet and flower‐like ZnIn₂S₄, respectively. Moreover, the stability of the ZnIn₂S₄ is significantly improved after coupling with the few‐layered Ti₃C₂T_x. The characterizations and density functional theory calculation demonstrate that the synergistic effect of the sulfur vacancy and Ti₃C₂T_x cocatalyst can greatly promote the electrons transfer from ZnIn₂S₄ to Ti₃C₂T_x and the separation of photogenerated charge carriers, thus enhancing the photocatalytic hydrogen evolution from water.

This paper reviews the surface engineering, including surface termination groups, surface functionalization, surface defects and surface oxidation, of MXenes, and their impact on energy and environmental applications of MXenes.

Photocatalytic CO₂ reduction is enhanced by the promoted charge transfer at the interface between TiO₂ and Ti₃C₂ after the in situ growth of TiO₂ on Ti₃C₂.