Effects of Cationic and Anionic Defects on NiFe LDH in Electrocatalytic Oxygen Evolution

Electrocatalytic water splitting is a promising method to generate high-purity hydrogen, yet its efficiency is limited by the large energy barrier of the counter oxygen evolution reaction (OER). NiFe-layered double hydroxides (NiFe LDHs) are considered as promising electrocatalysts, and some studies have indicated that the involved cationic and anionic defects can further promote their electrocatalytic activities. Nevertheless, the inherent relationships between the defective structures and catalytic activities are still unclear. In this work, by alkaline corrosion of NiFeZn LDH and NaBH₄ activation, we involved cationic and anionic defects, respectively. In addition, they both promote the electrocatalytic activity of NiFe LDH in OER, and the co-defected NiFe LDH (cd-NiFe LDH-NaBH₄) only needs a low overpotential of 205 mV to obtain a current density of 10 mA cm^-2. We invested the exact effects of cationic and anionic defects by electrochemical characterizations and X-ray adsorption structure. The results indicate that the effects of cationic and anionic defects are different, and the cationic defects could promote the oxidation process of Ni species in OER, thus facilitating the favored lattice oxygen mechanism routine, while the anionic defects could enhance the reactivity of Fe sites by creating partially filled antibonding states of Fe-O. Our research reveals the origin of the accelerating effects brought by defective sites in NiFe LDH for OER and provides a facile approach to enhance the catalytic properties of noble metal-free electrocatalysts toward OER.