Exceptional alkaline hydrogen evolution by molybdenum-oxide-nitride-based electrocatalysts with fast water-dissociation and hydrogen-adsorption kinetics

Abstract

Molybdenum (Mo)-based electrocatalysts have substantially shown impressive electrocatalytic properties towards alkaline hydrogen evolution (HER) catalysis. Herein, a Mo-based nitride/oxide engineered-type electrocatalyst, denoted as Ni_0.2Mo_0.8N/MoO₂, is grown on nickel foam and shows an extraordinary HER performance in 1.0 M KOH. The in situ Ni_0.2Mo_0.8N/MoO₂ interfacial nanorods are formed through a nitridation process of the precursor. The optimized electrocatalyst exhibits an ultralow overpotential of 13 mV at a current density of 10 mA cm⁻², which is superior to those of the corresponding oxide counterpart (NiMoO₄/MoO₂, 162 mV) and the benchmark Pt/C catalyst (27 mV). Density functional theory (DFT) calculations show that MoO₂ remarkably enhances the H₂O dissociation kinetics with a lower energy barrier of 0.09 eV compared to Ni_0.2Mo_0.8N at 0.39 eV, while Ni_0.2Mo_0.8N significantly reveals a very favorable H adsorption energy of −0.08 eV compared to MoO₂ at −0.23 eV, leading to accelerated H₂O dissociation and hydrogen adsorption/desorption kinetics of the Ni_0.2Mo_0.8N/MoO₂ catalyst. The present work offers an effective pathway for the rational design of highly efficient HER electrocatalysts.