Bimetallic atom-improved Ni3S2 bifunctional electrocatalysts for efficient hydrogen evolution reaction and overall water splitting performance

Abstract

The hydrogen evolution reaction (HER), as a pivotal half-reaction, significantly hinders the advancement of energy conversion efficiency. Metal electrodeposition on catalysts has been demonstrated to effectively enhance the HER reactivity. Here, Ni₃S₂–Fe–Ni with a multilayer structure was obtained by the electrodeposition of Ni₃S₂ with dopants Fe/Ni, in which a number of active sites were achieved and the intrinsic conductivity of the catalyst was well improved. Elemental analyses revealed the multilayer structure consisting of Ni₃S₂, NiS, and Fe. The Ni₃S₂–Fe–Ni catalyst exhibited impressive electrochemical performance due to optimization of its structure with the overpotentials of the HER and OER of only 83 and 190 mV. Notably, at a higher current density of 100 mA cm⁻², the overpotentials for the HER and OER are only 339 and 365 mV. As a bifunctional electrocatalyst, its total splitting voltage was only 1.55 V. The catalysis performance remained nearly unchanged even after 48 h of stability testing. Finally, density functional theory (DFT) calculations revealed that the potential barriers in each reaction step of the OER are evenly distributed, and optimizing the Ni₃S₂ structure with iron and nickel atoms reduced the reaction energy barriers during the electrochemical process, improving the OER/HER performance.