Interface charge density modulation of a lamellar-like spatially separated Ni₉S₈ nanosheet/Nb₂O₅ nanobelt heterostructure catalyst coupled with nitrogen and metal (M = Co, Fe, or Cu) atoms to accelerate acidic and alkaline hydrogen evolution reactions

The creation of heterostructures based on non-precious metals with platinum-like hydrogen evolution reaction (HER) performance remains a challenge for hydrogen fuel technologies. Motivated by the fascinating properties of heterostructures, we establish here an effective approach to fabricate the heterostructured M−N−Ni₉S₈/Nb₂O₅ (M = Co, Fe, or Cu) catalysts using spatially separated Ni₉S₈ nanosheet/Nb₂O₅ nanobelts that are coupled with nitrogen (N) and metal atoms. Due to its improved intrinsic activity, interface-rich structure, abundant active sites, and large surface area the Co−N−Ni₉S₈/Nb₂O₅ heterostructure achieved a low acidic HER overpotential of −171 mV at −10 mA cm⁻², thereby performing better than existing heterostructures. Moreover, for the alkaline HER, the Cu−N−Ni₉S₈/Nb₂O₅ heterostructure required a low overpotential of −109 mV at −10 mA cm⁻², which is close to the performance of Pt/C catalyst. Density functional theory (DFT) predictions indicate that the local charge distribution and electronic properties at the heterointerface of Ni₉S₈/Nb₂O₅ can be significantly modulated by co-doping of metals with N atoms, resulting in optimal adsorption energy and reduced water dissociation barrier; thereby accelerating the acidic and alkaline HER activity. This work, therefore, provides a new design principle to create advanced heterostructured catalysts.