Reduced NiO nanostructures grown on nickel foam by anodization and heat treatment for oxygen evolution reaction

A straightforward, cost-effective, and direct approach is developed to fabricate NiO nanostructures directly supported on nickel foams using only an annealing treatment in combination with a short-term anodization process and a reduction process before and after the heat treatment. The vapor-solid growth process is proposed as a possible mechanism for the growth of the NiO nanostructures. The oxygen evolution reaction (OER) activities of the fabricated electrodes were examined employing electrochemical measurements in 1.0 ​M NaOH. Among the fabricated electrodes, the nanoleaf-like NiO electrocatalysts composed of ultra-small NiO nanoparticles were shortly exposed to an alkaline solution at a voltage of 50 ​V (anodization) prior to the thermal annealing and followed by the reduction in NaBH4 exhibited the best electrocatalytic performance towards OER compared to the electrodes synthesized in the absence of reduction and solely by thermal annealing. The NiO nanoleaves delivered a current density of 135 ​mA/cm2 at 1.6 ​V potential versus the reversible hydrogen electrode (RHE) under alkaline conditions.