P-doped bimetallic sulfide to boost water dissociation and moderate H* adsorption for efficient alkaline hydrogen evolution

Abstract

The development of electrocatalysts for hydrogen evolution reaction (HER) with high catalytic activity and stability in alkaline medium remains a significant challenge. Herein, a catalyst (namely Zn_0.05Ni₃S₂-P) was designed to achieve the excellent alkaline HER performance owing to the boosted water dissociation and moderate H* adsorption energy. At the current density of 10 mA cm⁻², the overpotential of Zn_0.05Ni₃S₂-P is 143 mV. In addition, the Tafel slope and the charge transfer resistance of Zn_0.05Ni₃S₂-P are reduced, and the electrochemical active surface area (ECSA) is expanded. Density functional theory (DFT) calculations show that the appropriate proportion of Ni to Zn optimizes the H* adsorption energy of the catalyst. The introduction of P cooperates with S to activate the water dissociation, reduce the H₂O dissociation energy barrier, and accelerate the reaction kinetics. Moreover, in the process of electrolytic water splitting at 100 mA cm⁻² current density, the voltage is stable at 2.4 V, the hydrogen production rate is maintained at 1.84 mmol h^-1, and the Faraday efficiency of hydrogen production is nearly 100 %. This work simultaneously considers the importance of water dissociation and H* adsorption energy in alkaline HER, and provides a strategy for the design of highly active alkaline HER catalysts.