Regulating Complex Transition Metal Oxyhydroxides Using Ni₃S₂: 3D NiCoFe(oxy)hydroxide/Ni₃S₂/Ni Foam for an Efficient...

In electrochemical decomposition of water, the slow kinetics of the anodic oxygen evolution reaction (OER) is a challenge for efficient hydrogen production. Heterointerface engineering is a desirable way to rationally design electrocatalysts for the OER. Herein, we designed and fabricated a nanoparticle flower-like NiCoFe(oxy)hydroxide catalyst in situ grown on the surface of Ni₃S₂/NF to construct a heterojunction via combining hydrothermal and electrodeposition methods. The heterostructure exhibits a smaller overpotential of 254 mV at a large current density of 100 mA cm^-2 in 1 M KOH than that of pristine NiCoFeOH/NF (356 mV) and Ni₃S₂/NF (471 mV). Tafel and electrochemical impedance spectroscopy further showed a favorable kinetics during electrolysis. The role of the substrate Ni₃S₂ was explored via density functional theory calculations. Our calculations found that SO on the Ni₃S₂ surface is a strong nucleophilic group and the synergy effect between Fe and SO could break *OOH to reduce the Gibbs energy. We also found that the contribution of SO in sulfates to the OER activity could be negligible. Furthermore, a series of comparative samples were prepared to test this synergy effect. Our experiments indicated that the introduction of Ni₃S₂ is beneficial. The present contribution provides an important helpful insight into the design and fabrication of novel and highly efficient heterostructure electrocatalysts by introducing nucleophilic groups at the interface.