A review on electron-transport highways via defect engineering in TMDs for hydrogen evolution reaction

Intrinsic and extrinsic defect engineering strategies are the most ubiquitous zero-dimensional topological defects and prevalent in the transition metal dichalcogenides (TMDs) for hydrogen evolution. Such approaches tailor the crystal structure, phase, electronic states, electron transfer, and hydrogen adsorption energies (ΔG H⁎ ) of the TMDs. Defect-induced electronic redistribution and local lattice distortion create additional active sites and facilitate faster charge transfer, resulting in a reduction of overpotential, improved Tafel slope and optimum ΔG H⁎ . Here, we systematically summarize the intrinsic and extrinsic defect engineering strategies on TMDs that have been utilized to obtain an efficient hydrogen evolution reaction electrocatalyst. Contribution, such as vacancy, substitution, metal, nonmetal, and hybrid doping effects of TMDs towards hydrogen production, was concisely reviewed. In addition, the comparison of different TMDs along with their essential properties was displayed. Furthermore, representative case studies are presented to correlate defect structures with catalytic performance across different TMD systems. A comparative analysis of various TMDs and their essential properties is also provided. Finally, this review concludes with insights into future research directions for the development of advanced 2D TMD-based hydrogen production catalysts. This will bridge the existing knowledge gap by enhancing awareness of defect engineering among researchers currently working in this field.