Engineering controllable Fe defects in NiFeCo layered double hydroxide for enhanced electrocatalytic oxygen evolution performance and stability

To overcome the inherent activity, stability, and conductivity limitations of layered double hydroxides (LDHs) for the oxygen evolution reaction (OER), we developed an electrochemical-assisted strategy for time and potential controlled defect engineering in NiFeCo-LDH. Selective and controllable Fe extraction was achieved via a coordination reaction between Fe 3 + and SCN - under an applied potential, generating targeted oxygen and metal vacancies. The resulting catalyst exhibits an elevated Ni oxidation state and superior OER performance. The optimal sample (60 s Fe extraction) delivers a low overpotential of 254 mV at 100 mA/cm 2 and a Tafel slope of 48 mV/dec, while retaining over 90% activity after 400 h. In-situ Raman spectroscopy reveals that Fe extraction promotes the structural evolution from Ni(II)-O/OH to Ni(III)-OOH and activates the lattice oxygen mechanism (LOM), enhancing reaction kinetics. The catalyst also demonstrates promising performance under simulated industrial conditions and in seawater electrolytes, highlighting its potential for practical large-scale water electrolysis.