Self-Supported High-Entropy Alloy Electrocatalyst for Highly Efficient H₂ Evolution in Acid Condition

Developing non-precious catalysts as Pt substitutes for electrochemical hydrogen evolution reaction (HER) with superior stability in acidic electrolyte is of critical importance for large-scale, low-cost hydrogen production from water. Herein, we report a CoCrFeNiAl high-entropy alloy (HEA) electrocatalyst with self-supported structure synthesized by mechanical alloying and spark plasma sintering (SPS) consolidation. The HEA after HF treatment and in situ electrochemical activation for 4000 cycles of cyclic voltammetry (HF-HEAa2) presents favourable activity with overpotential of 73 mV to reach a current density of 10 mA cm⁻² and a Tafel slope of 39.7 mV dec⁻¹. The alloy effect of Al/Cr with Co/Fe/Ni at atomic level, high-temperature crystallization, as well as consolidation by SPS endow CoCrFeNiAl HEA with high stability in 0.5 M H₂SO₄ solution. The superior performance of HF-HEAa2 is related with the presence of metal hydroxides/oxides groups on HEA.