Hierarchical Chestnut-Burr Like Structure of Copper Cobalt Oxide Electrocatalyst Directly Grown on Ni Foam for Anion Exchange Membrane Water Electrolysis

Uniquely nanostructured CuCo2O4 is presented as an electrocatalyst for oxygen evolution reactions (OER). CuCo2O4 particles in a chestnut-burr-like shape (CCO*, where ∗ = chestnut burr) were hydrothermally synthesized around fibers of Ni foam substrates as current collectors. Chestnut burrs 4 μm on average had thorns consisting of less than five threads. Each thread was made of a consecutive array of nanobeads less than 10 nm. Nanovoids or nanopores were found between nanobeads. The chestnut-burr structure of CCO* allowed IrO2-overwhelming OER activity. By using the hierarchically nanostructured electrocatalyst directly grown on current collectors without binders and conducting agents, high performances of anion exchange membrane (AEM) electrolysis was demonstrated. Three merits of the electrode architecture were emphasized. First, mass transfer pathways for reactants and products were secured in a microscale between thorns and in a nanoscale between nanobeads. Second, more active sites were exposed to electrolytes in the hierarchical structure. Third, direct growth of active materials on conductive substrates improved adhesion and electrical conduction.