Universal pH electrocatalytic hydrogen evolution with Au-based high entropy alloys.

The creation of electrocatalysts with reduced concentrations of platinum-group metals remains a critical challenge for electrochemical hydrogen production. High-entropy alloys (HEAs) offer a distinct type of catalyst with tunable compositions and engineered surface activity, significantly enhancing the hydrogen evolution reaction (HER). We present the synthesis of AuPdFeNiCo HEA nanoparticles (NPs) using a wet impregnation method. The composition and structure of the AuPdFeNiCo HEA NPs are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM). These nanoparticles exhibit robust HER performance quantified over a broad pH range, with higher activity than any of the unary metal counterparts in all pHs. In comparison to a commercial 10%Pt/C electrocatalyst, AuPdFeNiCo HEA NPs exhibit enhanced electrochemical activity in both acidic and alkaline electrolytes at a current density of 10 mA cm-2. Additionally, these nanoparticles achieve a current density of 100 mA cm-2 at a voltage of 540 mV in neutral electrolytes, outperforming Pt/C which requires 570 mV. These findings help enable broad use of reduced precious metal electrocatalysts for water electrolysis in a variety of water and pH conditions.