Heterogeneous electrocatalyst of nanoscale Fe-based medium-entropy alloy and sulfide for oxygen evolution reaction.

The construction of heterojunctions between non-noble-metal based compounds affords a scheme for accelerating the reaction kinetics of oxygen evolution reaction (OER) without using precious mental materials, which is extremely important but remains challenging. Herein, the heterogeneous structure between Fe60Co10Ni10Cr10Mn10 medium-entropy alloy (MEA) and FeS2 is developed by a mechanical alloying approach. The resulting MEA-30 wt%FeS2 delivers a high OER activity with a low overpotential of 261.6 mV at 10 mA/cm2, along with Tafel slope of 52.7 mV/dec in 1.0 mol/L KOH solution, superior to the commercial RuO2. The combination of detailed characterization techniques and density functional theory (DFT) calculation reveals that the heterojunctions between Fe-based MEA and FeS2 generates the synergistic effect on the activation and formation steps of OOH*, thus promoting the OER reaction kinetics. Furthermore, the abundant active sites provided by the reconstructions of MEA-30 wt%FeS2 during OER process also contributes to the catalytic performance. This work greatly expands the application scope of medium-entropy materials and provides a new method for the fabrication of novel heterogeneous electrocatalyst of Fe-based MEA and FeS2.