Unfolding the Electrocatalytic Efficiency of Ultrastable CoFeLDH Nanorods by Creating Oxygen Vacancies for OER

Harnessing the potential of oxygen vacancies (Ov) in metal oxides presents a promising avenue for expediting reaction kinetics in water oxidation. In this context, layered double hydroxides (LDH) offer a versatile platform for developing cost-effective electrocatalysts with exceptional performance, thanks to their distinctive lamellar morphology. In this study, we unveil the augmented electrochemical efficiency of CoFeLDH by deliberately inducing an optimal oxygen vacancy (Ov) under ambient conditions for the oxygen evolution reaction (OER). The transformation of CoFeLDH nanorods (CoFeLDH) into Ov-rich CoFeLDH (CoFeLDH-Ov) takes place through a chemical reduction process at room temperature. The effect of Ov within the catalyst is substantiated through qualitative analyses, such as X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and electron paramagnetic resonance (EPR). The resulting catalyst, CoFeLDH-Ov, exhibits an overpotential of 220 mV at a current density of 30 mA/cm2 in a 1 M KOH electrolyte, indicating an enhanced electroactivity when compared to CoFeLDH (without Ov defects). The catalyst also reveals excellent stability for more than 500 h at a higher current density of 50 mA/cm2. To validate the catalyst's conducive nature, density functional theory (DFT) calculations are performed, revealing iron (Fe) as the prominent active site within the catalyst. By means of comprehensive experimental and theoretical analyses, the substantial influence of Ov on the electronic structure of the LDH system is demonstrated, which, in turn, facilitates facile charge transfer and strengthens the efficiency of the oxygen evolution reaction (OER).