Architecting Layered CoFeOOH for the Oxygen Evolution Reaction: Engineering Structure for an Anion Exchange Membrane Water Electrolyzer

Abstract

Among the various metal oxide structures, the metal oxyhydroxide structure has garnered significant attention due to its superior electrochemical properties in the context of the oxygen evolution reaction. However, there are a limited number of studies focusing on the long-term performance analysis of this structure for adaptation in anion exchange membrane water electrolyzers (AEMWE). This study presents an approach to synthesizing a stable layered structure by reducing the d-spacing of the layers through ion exchange from nitrate (NO3 -) to potassium (K+). A custom Fe precursor facilitated the exchange of Co with Fe, driven by a potential difference, while NaOCl enabled the oxidation of electrocatalyst hydroxides to oxyhydroxides. The chemical transformation was characterized using in situ Raman spectroscopy, demonstrating the role of Fe in enhancing the kinetics of CoFeOOH. The resulting CoFeOOH exhibited a performance of 2.0 A cm-2 at 1.8 V in the AEMWE system, with a long-term durability of 2100 h showing a degradation rate of only 49 mV kh-1. The postanalysis verified the preservation of morphology and the ratio of iron to cobalt concentration.