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

Abstract

A first report of the rational design of novel heterostructure of M−N−Ni 9 S 8 /Nb 2 O 5 catalysts ( M = Co, Fe, or Cu) via facile two-step hydrothermal approach. The synergy of spatially separated nanosheets of Ni 9 S 8 /Nb 2 O 5 nanobelts with N and M (Co, Fe, or Cu) atoms were examined in depth. This work highlights a rational heterostructure design strategy and demonstrates the importance of optimizing the HER kinetics. • Novel M−N−Ni 9 S 8 /Nb 2 O 5 ( M = Co, Fe, or Cu) heterostructure was made by a facile method. • Synergy of spatially separated nanosheet of Ni 9 S 8 /Nb 2 O 5 nanobelt with N and metal atoms was examined in depth. • Interface engineering of M−N−Ni 9 S 8 /Nb 2 O 5 ( M = Co, Fe, or Cu) heterostructures facilitates the acidic/alkaline HER activity. • Enhancement in HER kinetics of heterostructures was examined in detail by DFT predictions. 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−Ni 9 S 8 /Nb 2 O 5 ( M = Co, Fe, or Cu) catalysts using spatially separated Ni 9 S 8 nanosheet/Nb 2 O 5 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−Ni 9 S 8 /Nb 2 O 5 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−Ni 9 S 8 /Nb 2 O 5 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 Ni 9 S 8 /Nb 2 O 5 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.