Mechanical alloyed FeCoNiMoM (M=Cr, cu) high-entropy alloy powders as electrocatalysts for oxygen evolution reaction

Abstract

Here, micron-sized high-entropy alloy (HEA) electrocatalysts (FeCoNiMoCr, Cr-HEA; FeCoNiMoCu, Cu-HEA) with dual-phase heterostructures were fabricated by mechanical alloying and subsequently loaded onto nickel foam (NF) to form the working electrode, exhibiting excellent oxygen evolution reaction (OER) performance. Specifically, the Cr-HEA/NF exhibits an overpotential of 271 mV at current density of 10 mA/cm² and a small Tafel slope of 69.1 mV/dec in 1 mol/L KOH solution, outperforming the performance of Cu-HEA/NF, commercial RuO₂/NF and bare NF. HEA catalysts achieve outstanding long-term stability, as evidenced by chronopotentiometry (1 mol/L KOH for 48 h @10 mA/cm² and 6 mol/L KOH at 85 °C for 100 h @500 mA/cm²) and chronoamperometry (1 mol/L KOH for 100 h @100 mA/cm²). The impressive OER activity and stability of Cr-HEA can be attributed to the highly heterogeneous nested interfaces between amorphous and metastable nanocrystals, as well as the in-situ formation of multiphase structures. Notably, both density functional theory calculations and experimental results demonstrate that the synergistic interactions among the metal active sites in HEA collectively regulate the adsorption and desorption of oxygen-containing intermediates, thereby enhancing the OER catalytic activity. Specifically, the Cr-HEA presents a lower Gibbs free energy change during the transformation from O∗ to OOH∗, resulting in a reduced overpotential.