Catalyst activation: Surface doping effects of group VI transition metal dichalcogenides towards hydrogen evolution reaction in acidic media

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising alternatives to the platinum-based catalysts for hydrogen evolution reaction (HER). The edge site of these 2D materials exhibits HER-active properties, whereas the large-area basal plane is inactive. Therefore, recent studies and methodologies have been investigated to improve the performance of TMD-based materials by activating inactive sites through elemental doping strategies. In this review, we focus on the metal and non-metal dopant effects on group VI TMDs such as MoS2, MoSe2, WS2, and WSe2 for promoting HER performances in acidic electrolytes. A general introduction to the HER is initially provided to explain the parameters in accessing the catalytic performance of doped-TMDs. Then, synthetic methods for doped-TMDs and their HER performances are introduced in order to understand the effect of various dopants including metallic and non-metallic elements. Finally, the current challenges and future opportunities are summarized to provide insights into developing highly active and stable doped-TMD materials and valuable guidelines for engineering TMD-based nanocatalysts for practical water splitting technologies.