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.