Self-Supported High-Entropy Alloy Selenide Electrodes for Efficient Acid/Alkaline Amphoteric Water Electrolysis

In this work, Fe, Co, Ni, Cu, and Mo powders were used as starting materials to prepare high-entropy alloy (HEA) thin films by a coating and vacuum sintering process. Using the HEA thin film as the substrate, selenium was subsequently deposited by chemical vapor deposition (CVD) to obtain high-entropy alloy selenide thin films (HEASe). The phase structure, surface chemical states, morphology, and elemental distribution of the porous films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The electrocatalytic hydrogen evolution performance of the electrodes was evaluated using a three-electrode configuration in 0.5 M H2SO4, 1 M KOH, 1 M KOH + 0.5 M NaCl, and 1 M KOH + 0.5 M Na2S solutions. The results indicate that the HEA selenide thin-film electrodes exhibit favorable electrocatalytic behavior in all four electrolytes. Among them, HEASe-450 shows the best overall performance. In 0.5 M H2SO4, it requires an overpotential of only 57.6 mV to reach a current density of 10 mA cm−2, with a Tafel slope of 146.96 mV dec−1. In 1 M KOH, the overpotential at 10 mA cm−2 is 50.1 mV, and the corresponding Tafel slope is 142 mV dec−1. In 1 M KOH + 0.5 M NaCl, the overpotential is 52.7 mV with a Tafel slope of 122.72 mV dec−1. In 1 M KOH + 0.5 M Na2S, an overpotential of 85 mV is required, and the Tafel slope increases to 236 mV dec−1.