Coupled Defect, Interface, and Morphology Engineering in 2D TMC Heterostructures for Efficient and Stable Photoelectrochemical Hydrogen Production

ABSTRACT PEC water splitting using solar energy for hydrogen generation has been considered a sustainable process; nevertheless, its utilization is hindered by inadequate charge‐carrier separation, high carrier recombination rate, and lack of long‐term stability. In recent years, 2D transition metal chalcogenide semiconductors have been found to be suitable candidates for photoelectrodes due to the tunability of their electronic properties, high surface‐to‐volume ratio, and strong visible light absorption capabilities. Several breakthroughs in the development of TMC materials have been achieved, resulting in an improvement in PEC efficiency with a photocurrent density above 10 mA cm − 2 , IPCE greater than 50%, and stable operation time of more than several hours. In this review, an overall view of the role of combined defect engineering, interface modulation, and morphology tuning in the design of TMC heterostructures for hydrogen generation is provided. A comparison is made between different heterostructures such as type‐II, Z‐scheme, p‐n junction, and Schottky devices in terms of charge transfer and their performance in PEC systems. Issues associated with photocorrosion, synthesis, reproducibility, and device fabrication are addressed, along with novel approaches which include operando characterization techniques, DFT‐based design, and machine learning in materials discovery.