Heat Treated Cobalt Oxyhydroxides as Oxygen Evolution Electrocatalysts

Abstract

The oxygen evolution reaction plays a crucial role in energy storage applications such as rechargeable metal-air batteries and solar water splitting. In this study, the use of heat treated cobalt oxyhydroxide (CoOOH) as a catalyst for the oxygen evolution reaction is explored. Heat treatment of CoOOH samples is conducted in a range of 100-300° C. These are characterized using a number of techniques, including X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), in order to understand their properties. Catalyst activity and stability measurements were taken to explore differences in performance caused by heat treatment. The OER activity of CoOOH electrocatalysts was shown to decrease with heat treatment from the untreated sample up to 100° C, and then increase between 100-300° C. XPS analysis found that the ratio of OH:O decreases with increasing heat treatment temperature. Furthermore, SEM analysis suggested that the surface area of the samples was increasing with temperature of heat treatment. The CoOOH electrodes showed very little change in activity after 8 hours at significant overpotential, demonstrating good stability. Measurement of double-layer capacitance was used to obtain relative electrochemically active surface area. This data confirmed the SEM analysis, showing that active surface area increases from 100-300° C. While dehydration due to heat treatment may cause decreased activity, this is compensated for by the effect of increased area available for catalysis.