Sodium Sulfite Intercalationin Ni–Fe LayeredDouble Hydroxide Nanosheets to Form Oxygen Vacancies for ElectrocatalyticOxidation of Water

Introducing oxygen vacancies (V_O) can significantly improve the performance of electrocatalytic oxygen evolution (OER) for layered double hydroxides. However, introducing V_O requires harsh conditions, such as high temperature and high pressure, so the controllable introduction of V_O is still challenging. In this study, Ni–Fe layered double hydroxide with a higher concentration of V_O (Ni₃Fe–S₁₀) was prepared under mild conditions using a chemical reduction method in which sodium sulfite was used as an intercalation agent. The results of high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance show that Ni₃Fe–S₁₀ has abundant V_O. At 10 mA cm^–2, the overpotential of the Ni₃Fe–S₁₀ catalyst electrode reaches 235 mV, and the electrode can work stably for 45 h. In situ electrochemical Raman results show that NiOOH generated by Ni₃Fe–S₁₀ electrochemical reconstruction is the actual active site. The theoretical results show that introducing a reasonable V_O concentration can improve the inherent conductivity of the Ni₃Fe–S₁₀ catalyst, optimize the adsorption/desorption barrier of oxygen-containing intermediates, and accelerate the chemical reaction kinetics of the OER. This study provides a reference for designing high-performance NiFe-LDHs OER catalysts.