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.