This article reviews recent advances in transition metal dichalcogenide (TMD)-based electrocatalysts for the hydrogen evolution reaction, with a primary focus on metal combination strategies. The methods for incorporating external metals into TMDs, including doping, intercalation, high-entropy TMDs, and loading of metals or metal chalcogenides, are discussed, along with their associated mechanisms, as well as future research directions.

Among the various approaches for hydrogen production, electrocatalytic water splitting for hydrogen evolution reaction (HER) is considered as the most promising technology for industrial application. However, the large-scale implementation of this technology is still hindered by its dependence on expensive noble metal-based catalysts. Transition metal dichalcogenides (TMDs), owing to their layered structures and tunable electronic properties, have emerged as promising alternatives to noble metals for HER. Nevertheless, the intrinsic catalytic performance of TMDs remains inferior to that of noble metals, making the development of efficient and stable TMD-based electrocatalysts essential for practical applications. One effective strategy to enhance the HER activity of TMDs is metal combination, whereby various metals are incorporated into TMD system. The key advantage of this approach lies in the diverse roles that different metals can play, including stabilizing crystal structure, modulating electronic structure, constructing nanostructures, and inducing synergistic effects. To inspire both theoretical and experimental researchers for further advancements, this review presents a comprehensive overview of recent progress in metal combination strategies for TMD-based HER electrocatalysts. Particular emphasis is placed on the role of metal components in both single-phase systems and heterostructures, aiming to uncover general design principles for the rational development of high-performance multimetallic electrocatalysts.