Cu0.5Co2.5O4 nanoparticles are obtained by changes in the pH and applied as the anode in anion exchange membrane water electrolysis.

No abstract

A Cu–Co–P electrocatalyst for hydrogen evolution reaction (HER) was designed with a dendritic and porous foam structure. Fabricated by one-step electrodeposition with binary alloy on a hydrogen bubble template, the porous foam exhibited remarkable HER activity in alkaline conditions. Cu was the dominant element in the core and shell region and acted for 3D structure formation. Cu–Co formed in the shell part and acted as an active region for hydrogen evolution reaction. Also, as the amount of P increased in the Cu–Co–P foams, the pore numbers, the electrochemical surface area (ECSA), and the HER activity were enhanced. The improved activity is believed to originate from the charge separation between the negatively charged P (δ–) and positively charged Cu and Co (δ+), the larger ECSA, and increased porosity.

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.