Morphology-Controlled Nickel Oxide and Iron–Nickel Oxide for Electrochemical Oxygen Evolution Reaction

Morphology engineering is an attractive method for controlling the activity of metal and metal oxide catalysts. However, there have been only a few studies on nickel oxide regarding the shape control and observation of its catalytic properties. Here, we synthesized various morphologies of nickel oxide nanoparticles, namely octahedral ((111) facet exposed), hexagonal ((110) facet exposed), and donut-shaped (via Kirkendall effect). Additionally, a small amount of iron was added to the nanoparticles by two methods: doping and post-deposition. The hexagonal and donut-shaped nickel oxides exhibited higher oxygen evolution reaction (OER) activity than the octahedral nickel oxide. In addition, the hexagonal and donut-shaped Fe-post-deposited samples showed superior OER activity compared to the other iron–nickel oxide samples.