Electrocatalytic Oxygen Evolution Performance of Mo-Doped Flexible High-Entropy Alloys

Abstract:

The intrinsically sluggish kinetics of the oxygen evolution reaction (OER) severely restricts the practical efficiencies of water splitting and metal-air batteries. In this research, a series of flexible CrFeCoNiMo_x (x=0, 0.2, 0.5, 1) high-entropy alloy (HEA) monolithic electrodes were directly fabricated on carbon cloth by magnetron sputtering, and the influence of Mo doping content on their OER electrocatalytic performance was investigated. The results show that the appropriate Mo doping can significantly enhance the OER activity of the electrode. Among the prepared electrodes, CrFeCoNiMo_0.5 exhibits the highest catalytic activity, delivering a current density of 10 mA/cm² at an overpotential of only 212 mV with a Tafel slope of 37.4 mV/dec. Moreover, the electrode operates stably at 100 mA/cm² for 140 h without noticeable degradation. XPS, TEM and in-situ Raman analyses reveal that Mo doping tailors the electronic structure of 3d metals (Fe, Ni), elevates their oxidation states and promotes surface amorphization/reconstruction, thereby strengthening the adsorption of reaction intermediates. Density functional theory (DFT) calculations further demonstrate that Mo doping optimizes the reaction pathway and lowers the energy barrier for oxygen-vacancy formation. These findings provide both experimental evidence and theoretical support for the application of flexible HEA electrodes in advanced energy-conversion devices.