High-entropy alloy self-supporting bifunctional electrocatalysts with exceptional performance for flexible zinc–air batteries

Abstract

The development of efficient oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) bifunctional catalysts with high activity and stability is highly desirable for flexible rechargeable zinc-air batteries (ZABs). Herein, we proposed high-entropy alloy (HEA) FeCoNiCrCu nanoparticles assembled on carbon nanofibers (FeCoNiCrCu/CNFs) as a bifunctional catalyst for ZABs by an electrospinning in situ growth method, which exhibited an overpotential of 240 mV and a 50.3 mV dec⁻¹ Tafel slope at a current density of 10 mA cm⁻², much higher than that of RuO₂ based standard commercial catalysts. Also, superior ORR performance was observed for FeCoNiCrCu/CNFs with a half-wave potential of 0.78 V. The potential difference between the OER overpotential and the ORR half-wave potential is only 0.69 V for FeCoNiCrCu/CNFs, exceeding that of most of the catalysts reported so far. Using FeCoNiCrCu/CNFs as an air cathode, the assembled flexible ZABs exhibited an open circuit potential of 1.371 V, a peak power density of 87 mW cm⁻², a specific capacity of 820 mA h g_Zn⁻¹, and excellent stability over 75 hours of continuous charge and discharge cycles at different bending angles. The rational design of FeCoNiCrCu/CNFs opens a new avenue to the commercialization of bifunctional oxygen catalysts for ZABs.