Scalable Synthesis of Multi‐Metal Electrocatalyst Powders and Electrodes and their Application for Oxygen Evolution and Water Splitting

Multi-metal electrocatalysts provide nearly unlimited cata­lytic possibilities arising from synergistic element interactions. We pro­pose a polymer/metal precursor spraying technique which can easily be adapted to produce a large variety of compositional different multi-metal catalyst materials. To demonstrate this, 11 catalysts were syn­thesized, characterized, and investigated for the oxygen evolution reaction (OER). Further investigation of the most active OER catalyst, namely CoNiFeMoCr, revealed a polycrystalline structure, and oper­ando Raman measurements indicate that multiple active sites are par­ticipating in the reaction. Moreover, Ni foam-supported CoNiFeMoCr electrodes were developed and applied for water splitting in flow-through electrolysis cells with electrolyte gaps and in zero-gap membrane electrode assembly (MEA) configurations. The proposed alkaline MEA-type electrolyzers reached up to 3 A cm-2, and 24 h measurements demonstrated no loss of current density of 1 A·cm-2.