“…Numerous parameters are important, such as atomic level thickness plane, high surface area, edge effects, topological effects, short ion diffusion distance, alleviated restacking, efficient charge transfer, and abundant active sites, which could be a diverse advantage in favor of HER. [40,42,[154][155][156][157]43,44,46,47,89,90,152,153] Bulk 2D based materials can be straightforwardly exfoliated into atomically thin layer sheet, including single and/or double layer, owing to the presence of weak van der Waals force between the layers, which can be easily separated with minimum efforts depending on their different physicochemical properties such as density, conductivity, corrosion resistance, melting point, and chemical stability. [12,40,154,155,157,[42][43][44]47,87,89,90,152] In case of transition metal based chalcogen materials, the transition metal atoms and chalcogen atoms would be exposed in their top position of the materials where electrolyte can access the active surface easily.…”