Noble metal-free XFeCoNiCu (X = Cr, Mg, and Mn) high entropy alloys for efficient ORR/OER bifunctional catalysis

The development of low-cost and efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of importance for the commercialization of green and sustainable energy conversion devices. In this work, noble metal-free XFeCoNiCu (X = Cr, Mg, and Mn) high entropy alloys were prepared with a facile pyrolytic reduction approach while the structure and composition were characterized by XRD, ICP-OES, TEM, HRTEM, and XPS. The prepared quinary alloys demonstrated excellent activity and stability for both ORR and OER, which was even superior to that of commercial Pt/C and RuO₂. Moreover, all three catalysts exhibited considerable potential for bifunctional catalysis, with a ΔE gap of 0.659 V for CrFeCoNiCu, a ΔE gap of 0.692 V for MnFeCoNiCu, and a ΔE gap of 0.727 V for MgFeCoNiCu, which was much better than that of the Pt/C+RuO 2 combination (0.723 V). The superior performance was further revealed by Density Functional Theory (DFT) calculations with projection density of states (PDOS) and free energy change. The strategy proposed in this study provides an economical approach to design and develop bifunctional electrocatalysts with exceptional performance.