Flower-Sphere CoNiCuMnFe/C High-Entropy Alloy Catalysts for Enhanced Oxygen Evolution Reaction Kinetics

Abstract

The sluggish kinetics of the oxygen evolution reaction (OER) remain a significant bottleneck in the development of anodic water electrolysis technologies. High-entropy alloys (HEAs) have emerged as promising candidate catalysts for OER due to their versatile composition, which allows for the fine-tuning of electronic structures and catalytic active sites. In this study, we synthesize a flower-sphere-like HEA/C electrocatalyst via a molten salt method, with compositional control of CoNiCuMnM [M = IIA, I-IXB, and VIII (s, d²-d¹⁰)]. Among the compositions evaluated, CoNiCuMnFe/C exhibits superior catalytic performance, achieving an overpotential of 350 mV at 10 mA cm⁻² and a Tafel slope as low as 79 mV dec⁻¹. Density functional theory (DFT) calculations indicate that the strong intermetallic interactions within specific regions of the HEA enhance electron transfer across different metal sites. The d-band center of Fe is located at a deeper energy relative to the Fermi level (E_F), which indirectly boosts the OER catalytic activity. Ni and Mn, positioned closer to E_F, facilitate electron transfer, while their broader electronic energy levels enhance conductivity. This synergistic effect, particularly pronounced at Cu sites, improves OH* adsorption on the CoNiCuMnFe/C surface, significantly enhancing OER catalysis.