Deep Reconstruction of Mo-based OER Pre-Catalysts in Water Electrolysis at High Current Densities

Evaluating the dynamic structural reconstruction processes of transition metal-based oxygen evolution reaction (OER) catalysts at industrial current densities in a membrane electrode assembly (MEA) configuration of an anion exchange membrane (AEM) electrolyzer is required for the practical application of OER electrodes in AEM-type next-generation electrolyzers. This study unveils the deep reconstruction phenomenon of a Mo-containing OER catalyst anode during electrolysis at high current densities. A complete reconstruction of the catalyst due to selective Mo-leaching is inevitable during high current operation and thereby new catalytic surfaces of the Mo-containing Ni-based electrodes for sustainable water electrolysis are exposed. The reconstruction was confirmed by ex situ and in situ surface characterization techniques. A scalable route for electrode fabrication demonstrated and it is shown that the reconstruction mechanism of the catalyst leads to a more sustainable operation of the electrolyzer at high current densities. Deep reconstruction of NiMo electrode at high current operation: Hydrothermally fabricated Ni-Mo_Ni foam electrodes show a deep reconstruction during high current electrolysis. The resulting Mo-deficient NiOOH showed improved catalytic current and a stable operation for 24 h at 0.75 A cm-2.image