Electrochemical dealloying in ChCl-Urea Deep eutectic solvent: A strategy to fabricate porous FeCoNiAlMo high-entropy alloy with enhanced oxygen evolution reaction activity

Abstract

High-entropy alloys (HEAs), as a new type of multi-element alloy, have become widely studied electrocatalytic materials in recent years due to their excellent catalytic performance. The experimental material used FeCoNiAlMo HEA with equal atomic ratio as the precursor, and three-dimensional nanostructures were formed by dealloying in choline chloride-urea (ChCl-Urea). The results indicate that Fe₂₀Co₂₀Ni₂₀Al₂₀Mo₂₀ HEA is mainly composed of body-centered cubic (BCC) phase and face-centered cubic (FCC) phase, with BCC phase accounting for a larger proportion. Due to the different corrosion resistance of elements and the difference in element content distribution between the two phases, the FCC phase is preferentially corroded, resulting in a three-dimensional porous morphology. This unique structure synergistically reduces the energy barrier during the hydrolysis dissociation process, giving the material a significant advantage in the oxygen evolution reaction (OER) process. At a current density of 10 mA cm⁻², the overpotential of the treated alloy is as low as 312 mV, which is lower than the commercial RuO₂-IrO₂, and it has lower resistance and higher charge transfer efficiency.