Fe/FeCo-based metal-organic framework nanosheet/ nanoparticle directly grown on nickel foam as a stable electrode for electrochemical oxygen evolution reaction

Abstract

Metal-organic frameworks (MOFs) are selective electrocatalysts for oxygen evolution reactions (OER) owing to their high specific surface area, rich pore structure, and so on. Herein, a series of Fe/FeCo-based MOFs were developed over nickel foam (NH2-MIL-101-Fe@NF/NH2-MIL-101-(CoFe)@NF-X) employing a facile process. An overpotential of 376 mV was observed at 100 mA cm−2 for Fe-MOF. The structural modification with the addition of Co for FeCo-MOFs can improve the morphology as well as the electrochemical performance. Among of them, NH2-MIL-101-(CoFe)@NF-2 illuminates an excellent overpotential 329 mV with a small Tafel slope of 50 mV dec−1 at 100 mA cm−2. Its surface roughness facilitates the deep penetration of electrolyte to the internal structure of the electrode. Theoretical calculations confirmed the introduction of Co can reduce the overpotential from 0.68 V to 0.34 V at the rate-determining step (from O∗ to OOH∗). This is a key feature that promotes the electrochemical performance of OER catalysts.