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

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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.

The electric conductivity-dependence of the number of electrons transferred during the oxygen reduction reaction is presented. Intensive properties, such as the number of electrons transferred, are difficult to be considered conductivity-dependent. Four different perovskite oxide catalysts of different conductivities were investigated with varying carbon contents. More conductive environments surrounding active sites, achieved by more conductive catalysts (providing internal electric pathways) or higher carbon content (providing external electric pathways), resulted in higher number of electrons transferred toward more complete 4e reduction of oxygen, and also changed the rate-determining steps from two-step 2e process to a single-step 1e process. Experimental evidence of the conductivity dependency was described by a microscopic ohmic polarization model based on effective potential localized nearby the active sites.