A group of first-row transition metal dichalcogenides (ME₂, M = Fe, Co, Ni; E = S, Se) are introduced as non-precious HER catalysts in an acidic electrolyte. They exhibit excellent catalytic activity especially in their nanoparticle form. These compounds expand and enrich the family of high performance HER catalysts.

Significance: The electronic structures of two-dimensional materials can be tuned for a variety of applications by guest species intercalation into the van der Waals gaps. Using Li electrochemical intercalated MoS ₂ as an example here, we correlate the continuously tuned electronic structure of lithiated MoS ₂ with the corresponding enhanced hydrogen evolution reaction activity, and thus construct the electronic structure–catalytic activity relationship. This work offers a unique thinking of tuning the electronic structures of layered materials by guest species intercalation for optimizing different kinds of catalysis on the basis of the strong correlation between the electronic structures and catalytic activities of the catalysts.