Preparation of high-entropy alloy bifunctional catalysts with rare earth Ce coordination and Efficient water splitting research

In the electrolytic water hydrogen production, the slow electrocatalytic kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) limit the energy conversion efficiency. Multi-metal high-entropy alloys (HEAs) are considered potential catalysts to replace traditional metal oxides and precious metals in energy conversion and water electrolysis. In this study, a solution of Fe, Co, Ni, Mo, and Ce halide salts was formed through hydrogen bonding with a chelating agent, citric acid (CA). After thermolysis, a highly efficient and stable rare earth (RE) Ce-coordinated single-phase non-precious metal high-entropy alloy (HEA) was obtained. Under alkaline conditions for the oxygen evolution reaction (OER), the overpotential of FeCoNiMoCe HEA/C was only 260 mV at a current density of 10 mA cm⁻², which is 40 mV lower than that of commercial RuO₂. Under alkaline conditions for the hydrogen evolution reaction (HER), FeCoNiMoCe HEA/C had an overpotential of only 130 mV at a current density of 10 mA cm⁻², which is only 60 mV higher than that of commercial Pt/C catalyst. The FeCoNiMoCe HEA/C displayed excellent catalytic activity in the overall water splitting system. This is due to the atomic disorder of high-entropy alloy catalysts, which provides more reaction sites, thereby increasing reaction activity and selectivity. Our work presents a straightforward and feasible synthetic strategy for preparing high-entropy compounds, which holds great potential in energy and electrocatalysis applications through entropy engineering.