Improving the efficiency of the oxygen evolution reaction (OER) could be highly beneficial to a variety of clean energy applications. Technologies that include fuel cells, electrolyzers, and metal-air batteries are often limited by the cost and scarcity of precious metal catalysts. There is, therefore, a desire to identify earth-abundant electrocatalysts that exhibit reduced overpotentials and to prepare nanocatalyst structures that both efficiently utilize and increase the active surface area of these materials. Recently, the intentional inclusion of Fe into Ni oxide thin films to prepare electrodes of a homogenous composition have exhibited a reduction in their overpotentials and improved overall catalytic activity. The incorporation of discreet FeNi nanoparticles (NPs) into the surfaces of Ni electrodes has not, as of yet, been fully explored and is of interest to assess how these surface inclusions and morphologies may change with prolonged electrochemical aging.

In this work, dimpled Ni electrodes supporting FeNi NPs were prepared by electroplating around spherical poly(styrene) (PS) templates (500-nm in diameter). The PS spheres were coated with FeNi NPs using solution-phase assembly techniques. The NP coated PS spheres served two functions: (i) creating regular dimpled features for tracking the electrode morphology; and (ii) positioning the FeNi NPs at the electrode surfaces within these dimpled features. Alkaline electrochemical aging by cyclic voltammetry (CV) was conducted to achieve an adequately stable Ni oxy-hydroxide phase prior to the OER measurements. Changes to the composition and morphology of these electrodes, both before and after electrochemical measurements, were monitored by scanning and transmission electron microscopy techniques including correlative energy dispersive X-ray spectroscopy. The FeNi NPs coated on Ni electrodes demonstrated a higher electrochemical activity for the OER than dimpled Ni electrodes without the FeNi NPs.