Cu intercalation and defect engineering realize an atomic-scale hydrogen spillover effect in NbS₂ to boost acidic hydrogen evolution

Promoting the intrinsic catalytic activity of transition metal dichalcogenides (TMDs) for the hydrogen evolution reaction (HER) is very beneficial for developing Pt-free single-component electrocatalysts. Here we report a single-component TMD-based electrocatalyst, Cu0.4NbS2-delta, with chemical intercalation and sulfur vacancies. Cu0.4NbS2-delta was synthesized conveniently using a solid-phase reaction and it exhibits a hexagonal lattice with intercalated Cu atoms in a four-coordinated tetrahedral configuration. Comprehensive experiments and theoretical calculations indicate that the intercalation and S vacancies redistributed the electronic structure of pristine NbS2, leading to multi-functional catalytic sites including defect hollow sites in the basal plane and different Cu sites in between the layers. Therefore, hydrogen spillover can proceed along pathways at the atomic level in Cu0.4NbS2-delta from proton adsorption at defect hollow sites, through interlayer sites for readily occurring hydrogen migration, and finally to Cu sites for fast H-2 desorption. Based on this atomic-scale hydrogen spillover effect, the polycrystalline Cu0.4NbS2-delta exhibits a low overpotential of 153 mV at 10 mA cm(-2) and great durability after 3000 cycles. Our work provides an effective strategy to build hydrogen spillover pathways in TMDs, which is instructive for exploring economical single-component electrocatalysts with high intrinsic activity.