MIL-88A derived CoFe-layered double hydroxides with optimized composition for the enhanced electrocatalytic oxygen evolution reaction

The oxygen evolution reaction (OER) as the anodic half-reaction of water electrolysis has received growing attention due to its paramount role in the green and sustainable production of hydrogen fuel and metal-air batteries. Herein, we report the synthesis of five CoFe-layered double hydroxides (CoFe-LDHs) and their application toward the electrocatalytic OER in an alkaline medium. CoFe-LDHs were prepared via a novel hydrothermal route from the MIL-88A metal-organic framework (MOF). The Co-to-Fe ratios in the LDHs were systematically modified to tune the electrocatalytic activity in the OER. It was observed that the as-prepared Co 0.39 Fe 0.61 -LDH demonstrated a superior electrocatalytic performance compared to the rest of the materials. More precisely, Co 0.39 Fe 0.61 -LDH required an overpotential of 227 mV to derive 20 mA cm −2 current density with a Tafel slope of 36.8 mV dec −1 and exhibited remarkable electrochemical stability. Besides, this LDH delivered an industrial-scale current density of 600 mA cm −2 at an overpotential of 284 mV. Our results imply that modulating the metal content of LDHs is a simple yet effective strategy to promote their electrocatalytic activity toward the OER. This work demonstrates the fabrication of MIL-88A-derived CoFe-LDHs with variable Co/Fe molar ratio as efficient electrocatalysts toward the alkaline OER.