V-doped Ni_(3)N/Ni heterostructure with engineered interfaces as a bifunctional hydrogen electrocatalyst in alkaline solution:Simultaneously improving water dissociation and hydrogen adsorption

摘要

Alkali-water electrolyzers and hydroxide exchange membrane fuel cells are emerging as promising technologies to realize hydrogen economy.Developing cost-effective electrode materials with high activities towards corresponding hydrogen evolution(HER)and oxidation(HOR)reactions plays a crucial role in commercial hydrogen production and utilization.Herein,we fabricated a V-doped Ni_(3)N/Ni heterostructure(V-Ni_(3)N/Ni)through a controlled nitridation treatment on a V-incorporated nickel hydroxide precursor.The resultant catalyst exhibits comparable catalytic activity and durability to commercial Pt/C in terms of both HER(a low overpotential of 44 mV at the current density of 10 mA·cm^(-2))and HOR(a high current density of 1.54 mA·cm^(-2)at 0.1 V versus reversible hydrogen electrode)under alkaline conditions.The superior activity of V-Ni_(3)N/Ni grown on different substrates further implies its intrinsic performance.Density functional theory(DFT)calculations reveal that the coupled metallic Ni and doped V can promote the water adsorption,accelerate the Volmer step of alkaline HER,as well as optimize the adsorption and desorption of hydrogen intermediate(H^(*))to reach a balancedΔGH*value.