Cobalt oxide (CoO_x) coated Ni foam anodes for high temperature (150 °C) and pressure (45 bar) alkaline electrolysis

CoO_x-coated Ni foam (CoO_x/NF) electrodes are evaluated as anodes for high temperature and pressure (HTP) alkaline electrolysis. The electrodes are tested for the oxygen evolution reaction (OER) from room temperature to 150 °C at 45 bar pressure in 45 wt% KOH and compared with commercially available pristine NF and Inconel-coated NF (Inconel/NF) electrodes. Although the Inconel/NF electrode shows the best performance at 25 °C and 45 bar pressure, the performance of CoO_x/NF and Inconel/NF become comparable upon raising the operating temperature to 150 °C. During a long-term (108 h) stability test at 150 °C and 45 bar pressure, the CoO_x/NF electrode maintained stable performance, requiring an overpotential of 185 mV at 500 mA cm⁻². In contrast, the Inconel/NF electrode experienced an increase in overpotential from 182 mV to 208 mV after 84 h of operation under identical conditions. The structural and chemical changes in these electrodes were investigated using post-mortem scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), comparing their evolution to that of the fresh electrodes.