Processable Surface Modification of Nickel-Heteroatom (N, S) Bridge Sites for Promoted Alkaline Hydrogen Evolution.

Abstract

Nickel-heteroatoms bridge sites are important reaction descriptors for many catalytic and electrochemical processes. Herein we report the controllable surface modification of nickel-nitrogen (Ni-N) bridge sites on metallic Ni particles via a simplified vapor-assisted treatment approach. X-ray absorption spectroscopy (XAS) and Operando Raman spectroscopy verifies the interaction between Ni and surface-anchored N, which leads to distorted Ni lattice structure with improved wettability. The Ni-N bridge sites with appropriate N coverage level plays a critical role in the enhanced hydrogen evolution reaction (HER) and the optimized electrode (Ni-N0.19 ) has demonstrated superior HER performances with low overpotential merely of 42 mV for achieving a current density of 10 mA cm-2 , as well as favorable reaction kinetics and excellent durability in alkaline electrolyte. DFT calculations revealed that the appropriate N-coverage level can lead to the most favorable ΔGH* kinetics for both adsorption of H* and release of H2 , while high N coverage (Ni-N0.59 ) results in weaker H* adsorption, thus a decreased HER activity, corresponding well to our experimental observations. Furthermore, this generic synthetic approach can also be applied to prepare S-modified Ni HER catalyst by generating hydrogen sulfide vapor.