The rational design of a heterostructural photocatalysts with efficient charge separation and accelerated interfacial charge transfer holds great promise for boosting photocatalytic activity. Herein, we have developed a unique hierarchical In_4/3P₂S₆/TiO₂ heterojunction with P–O interfacial bonding for photocatalytic water reduction. By integrating emerging In_4/3P₂S₆ nanosheets through intense interfacial coupling effect, the optimized In_4/3P₂S₆/TiO₂ heterostructure exhibits a remarkably enhanced photocatalytic H₂ evolution activity compared to that of pristine TiO₂. Combined experimental and theoretical results confirm that multiple interfacial bonded step-scheme (S-scheme) charge transfer pathways are established in the In_4/3P₂S₆/TiO₂ photocatalyst, which synergistically promote charge separation and transfer through the robust interfacial electric field and rapid charge migration pathways formed by interfacial bonds. This study emphasizes the significance of developing novel interfacial bonded In_4/3P₂S₆-based S-scheme heterostructures, paving a new strategy towards enhancing photocatalytic activity for H₂ evolution.

Incorporating metal nanodots (NDs) into heterostructures for high charge separation and transfer capacities is one of the most effective strategies for improving their photocatalytic activities. However, controlling the space distribution of metal NDs for optimizing charge transport pathways remains a significant challenge, particularly in two-dimensional (2D) face-to-face heterostructures. Herein, we develop a simple targeted self-reduction strategy for selectively loading Ru NDs onto the Ti_3−xC₂T_y (TC) surface of 2D TC/g-C₃N₄ (CN) heterojunction based on the reductive Ti vacancy defects creatively increased during the preparation of TC/CN by reducing calcination. Notably, the optimized Ru/TC/CN photocatalyst exhibits an outstanding H₂ evolution rate of 3.21 mmol·g⁻¹·h⁻¹ and a high apparent quantum efficiency of 30.9% at 380 nm, which is contributed by the unidirectional transfer of the photogenerated electrons from CN to Ru active sites (CN → TC → Ru) and the suppressed backflow of electrons from Ru sites to CN, as revealed by comprehensive characterizations and density functional theory (DFT) calculations. This work provides a novel strategy for synthesizing the highly efficient photocatalysts with a controllable charge transfer paths, which will boost the development of photocatalysis.

Recently, defect architectured photocatalysis is proved to be the most versatile choice for high solar to chemical energy conversion processes. Defect engineering strategies are of great demand to effectively tune the electronic microstructure and surface morphologies of semiconductors to boost charge carrier concentration and extend light harvesting capability. This review provides a comprehensive insight to various kinds of defects along with their synthesis procedures and controlling mechanism to uplift photocatalytic activity. In addition, the contribution made by defects and material optimization techniques toward electronic band structure of the photocatalyst, the optimal concentration of defects, the key adsorption processes, charge distribution, and transfer dynamics have been explained in detail. Further, to clarify the relationship between photocatalytic activity and defect states in real, a comprehensive outlook to the versatile photocatalytic applications has been presented to highlight current challenges and future applications. Defect engineering therefore stands as the next step toward advancement in the design and configuration of modern photocatalysts for high efficiency photocatalysis.