Ultrasonic Powder Atomization of Raney Nickel-type Precursors for Hydrogen Cathodes in Water Electrolysis

Hydrogen, as an emission-neutral energy carrier, plays a key role in establishing a circular energy system and holds the potential to decarbonize numerous technical sectors. However, most hydrogen production to date has been derived from fossil fuels such as gray hydrogen. In contrast, sustainable green hydrogen can be generated by water electrolysis using renewable electrical energy. Yet, this remains economically unviable due to the comparatively low efficiency and high costs of precious cathode materials such as platinum. Hence, Raney nickel-type cathodes present a cost-efficient alternative due to their catalytic material properties. In perspective, thermally sprayed precursors are promising thanks to their characteristic open-porous structure, which is beneficial in applications such as atmospheric plasma spraying. Subsequent leaching of aluminum-rich phases chemically activates the surface and a nickel structure with a high specific surface area remains, which will enhance cathode reactivity. Prior to spraying, however, an appropriate powder feedstock must be identified. Also, the production by powder atomization is to be evaluated in order to meet the requirements for the indented application, including chemical homogeneity and composition, powder morphology and microstructure, phase formation, as well as particle size distribution. Therefore, in this study, preselected metal wires were arc-melted to rods with various compositions and subsequently ultrasonically atomized. Furthermore, bulk specimens were produced by spark-plasma sintering with low oxidation and low porosity. The material properties were examined along this process chain and related to the required functional properties, providing a comprehensive assessment of this approach.