A Molten Salt Synthesis Method of the High-Entropy Alloy CrMnFeCoNi for High Catalytic Performance and Low Life Cycle GHG Emissions

The high-entropy alloy (HEA) CrMnFeCoNi is a prominent catalyst material. High-specific-surface-area HEA powder can be chemically prepared via a conventional direct etching method or a molten salt synthesis method developed in our group. In this study, we compared the catalytic performance in the hydrogenation of p-nitrophenol using the HEA CrMnFeCoNi powders obtained from the etching method and the molten salt method. The results demonstrated a superior catalytic performance for the HEA prepared by the molten salt method at 800 °C. A structural analysis comprising X-ray diffraction, scanning electron microscopy/transmission electron microscopy with energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy revealed that the HEA CrMnFeCoNi prepared by the molten salt method is composed of a homogeneous HEA core covered by an active nickel-rich surface shell, which contributes to the superior catalytic performance. Furthermore, a life cycle GHG emissions assessment was conducted to compare the environmental performances of the two methods. The result showed that the molten salt method accounted for 121 kg CO2e/kg HEA production, which is 20% lower than that for the common etching method. Thus, the molten salt synthesis method is a promising option to industrialize HEA production.