Edge-Induced Synergy of Ni-Ni Defects in NiFe Layered-Double-Hydroxide for Electrocatalytic Water Oxidation Reaction.

Defect engineering is widely regarded as a promising strategy to enhance the performance of electrocatalysts for water splitting. In this work, defective NiFe layered double hydroxide (NiFe LDH) with a high density of edge sites (edge-rich NiFe LDH) is synthesized via a simple reduction process during the early stages of nucleation. The introduction of edges into oxygen evolution reaction (OER) catalysts modulates the electronic structure of the active sites. X-ray absorption spectroscopy (XAS) analyses revealed that the edges facilitated the formation of unsaturated Ni-Ni coordination, which is crucial for promoting the deprotonation of the OH intermediate. Consequently, the edge-rich NiFe LDH exhibited a significantly lower overpotential of 228 mV to achieve a current density of 10 mA cm⁻, compared to 275 mV for pristine NiFe LDH. The assembled membrane electrode can reach a current density of 1000 mA cm⁻ at a cell voltage of 2.5 V. This study highlights the role of edge effects in defect engineering to enhance OER activity and provides valuable theoretical insights for the design of efficient electrocatalysts.