Edge stimulated hydrogen evolution reaction on monodispersed MXene quantum dots

Nanostructuring of 2D MXene has promised as a non-noble electrocatalyst for hydrogen evolution reaction. Nevertheless, the insufficient density and activity of active sites on its basal plane are largely limiting the catalytic performance. Here, we show that by tailoring the 2D MXene nanosheets into their 0D quantum dots (QDs), active sites from edges are enriched for hydrogen evolution reaction (HER). We also demonstrate the generality of such an active trend by expanding the synthetic methodology to other MXene-based QDs, i.e., M−Ti3C2 QDs, M−V2C QDs, S−Nb2C QDs, M−Nb2C QDs, from their corresponded multi-layer (M) or single-layer (S) MXene nanosheets. Taking Ti-based MXene as a typical example, its monodispersed QDs exhibit 13.7 times higher activity than that of their pristine nanosheets, while remaining a good stability. We find that the metal atoms at the edge of QDs bind the intermediate H* species more moderately and therefore deliver a much lower energy barrier, especially for those terminated with hydroxyl groups, and rationalize this finding by theoretical calculations, demonstrating a more active role on the edge sites than those on the basal planes.