Understanding highly active and durable Fe-decorated Co(OH)2 catalysts in alkaline oxygen evolution reaction by in situ XANES studies

The activation and degradation mechanisms of CoFe layered double hydroxide (CoFe-LDH) and Fe-decorated Co(OH)2 (Fe-Co(OH)2) have been investigated using in situ X-ray absorption spectroscopy coupled with cyclic voltammetry (CV) in 0–0.9 V (vs Hg/HgO). A series of CoFe-LDH samples have been prepared by co-electrodeposition with varying Co/Fe ratios. Fe-decorating on Co(OH)2 has been applied using 10 ppm of Fe in 1.0 M KOH. Electrochemical impedance spectroscopy (EIS) and CV cycles confirm the degradation of Co(OH)2 and CoFe-LDH due to the irreversible redox of Co(OH)2/CoOOH, and Fe extraction. In contrast, Fe-decorated Co(OH)2 shows high activity and stability in the OER. In situ XANES analysis suggests that the Fe-decorating allows the Co(OH)2 to remain as γ-CoOOH even under potential fluctuations.