Electrochemical preparation and homogenization of face-centered FeCoNiCu medium entropy alloy electrodes enabling oxygen evolution reactions

ABSTRACT:
The exploitation of facile preparation methods and novel applications of entropy alloys has gained ever-increasing attention in recent years. In this paper, homogeneous FeCoNiCu medium entropy alloys (MEAs) with a face-centered cubic (FCC) structure are prepared by the electrochemical reduction of oxides in molten Na₂CO₃-K₂CO₃ using a low-cost Ni10Cu11Fe oxygen-evolution inert anode. The current efficiency reaches 85.3% with a low energy consumption of 2.9 kWh/kg-MEA. At the cathode, Ni acts as a solvent to dissolve other elements and facilitate the formation of the FCC phase, and the co-reduction process enhances the element diffusion rate thereby ensuring the homogeneity of the electrolytic MEAs. In addition, the electrolytic MEAs are pressed into pellet electrodes with an in situformed oxides layer to catalyze oxygen evolution reactions (OER) in 1.0 M KOH solution. The electrocatalytic activity of the electrolytic MEAs outperforms the commercial IrO₂/Ta₂O₅-Ti electrode, i.e., the overpotential of the electrode is 439 mV at 50 mA/cm² and the electrode lasts for 10 h without any degradation. Therefore, this paper provides a facile approach to preparing homogeneous MEAs at below 1173 K using oxides feedstock, to accurately controlling compositions and structures of MEAs, and thereby to tailoring functionalities of MEAs.