Unraveling the role of iron on Ni-Fe alloy nanoparticles during the electrocatalytic ethanol-to-acetate process

The anodic electrooxidation of ethanol to value-added acetate is an excellent example of replacing the oxygen evolution reaction to promote the cathodic hydrogen evolution reaction and save energy. Herein, we present a colloidal strategy to produce Ni-Fe bimetallic alloy nanoparticles (NPs) as efficient electrocatalysts for the electrooxidation of ethanol in alkaline media. Ni-Fe alloy NPs deliver a current density of 100 mA·cm⁻² in a 1.0 M KOH solution containing 1.0 M ethanol merely at 1.5 V vs. reversible hydrogen electrode (RHE), well above the performance of other electrocatalysts in a similar system. Within continuous 10 h testing at this external potential, this electrode is able to produce an average of 0.49 mmol·cm⁻²·h⁻¹ of acetate with an ethanol-to-acetate Faradaic efficiency of 80%. A series of spectroscopy techniques are used to probe the electrocatalytic process and analyze the electrolyte. Additionally, density functional theory (DFT) calculations demonstrate that the iron in the alloy NPs significantly enhances the electroconductivity and electron transfer, shifts the rate-limiting step, and lowers the energy barrier during the ethanol-to-acetate reaction pathway.