Design and Analysis of Carbon‐Supported NiMo HER Catalysts and Electrodes for High Performance All PGM‐Free AEM Electrolysers

ABSTRACT The influence of the nature of carbon‐support materials on the structure and the electrochemical performance of NiMo cathode catalysts is investigated. Carbon materials addressed in this study include Ketjen Black, Vulcan and MWCNT‐COOH. A one pot, easily scalable, hydrothermal microwave synthesis with a subsequent hydrogen reduction step was applied for the preparation of the catalyst materials. The structures and compositions of the catalysts were characterized by TEM/SEM, XRD, ICP‐OES, BET and STEM‐EDX. The performance of the catalysts was tested using rotating disc electrode (RDE) and anion exchange membrane (AEM) single‐cell electrolyser to downselect the most active material. The influence of pH, catalyst loading and type of carbon support was investigated to optimize the operating conditions. By increasing the KOH concentration from 0.1 to 1 M in an AEM electrolysis cell, the current density could be more than doubled, whereas the introduction of a carbon support raised the current density by a factor of seven. Finally, it is demonstrated how applying a novel bar‐coating preparation of the electrodes in a PGM‐free AEM electrolyser enabled a favourable current density of 1 A cm −2 at 2.04 V. This performance is comparable to earlier systems but requires only a fraction of the catalyst loading.