Synergistic effect of multiple vacancies to induce lattice oxygen redox in NiFe-layered double hydroxide OER catalysts

The role of multiple vacancies containing cation and anion defects in NiFe layered double hydroxide (LDH) is still worth pursuing in electrocatalytic oxygen evolution reaction (OER). Herein, a strategy integrating the oxygen and iron vacancies is proposed to fabricate NiFe LDH with highly efficient OER performance. More Fe vacancies have been introduced with increasing Fe content in NiFe-LDH structure; operando electrochemical characterizations and density functional theory (DFT) calculations reveal that the synergic effect between the iron and the oxygen vacancies promotes the generation of reconstructed active layers, optimizing the adsorption free energy of oxygen-containing intermediates. More importantly, active NiOOH intermediate species induced by oxygen vacancies are associated with OH- intercalation pseudocapacitance, activating lattice oxygen during water oxidation. The as-prepared Ni0.3Fe0.7-LDH@NF showed ultralow overpotentials of 184 and 287 mV to achieve 10 and 400 mA·cm-2, respectively. Our work provides a new paradigm for designing high-efficiency OER electrocatalysts.