High entropy alloy electrocatalyst synthesized using plasma ionic liquid reduction

Abstract

We report a novel cost-effective scaling process for the synthesis of the quinary IrPdPtRhRu high-entropy alloy nanoparticles (HEA-NPs). The process is based on the plasma ionic liquid reduction strategy. A combination of PXRD, HRTEM, XPS, and EDX analyses confirms that the application of the developed wet plasma reduction method yields the IrPdPtRhRu HEA-NPs. HEA-NPs ≈5 ​nm in size are synthesized under a mild temperature condition at atmospheric pressure and without support assistance. All elements constituting the as-prepared IrPdPtRhRu HEA-NPs are uniformly distributed in the FCC single-phase nanostructure. The valence band emission suggests the hybridization of the metal orbitals in the IrPdPtRhRu HEA-NPs. The work function (WF) of 4.63 ​eV for the HEA is determined by ultraviolet photoelectron spectroscopy. The WF value is lower than those of the metals constituting the HEA, suggesting higher catalytic activity. The IrPdPtRhRu/C electrocatalyst shows excellent catalytic performance toward hydrogen evolution reaction (HER) with an overpotential of 60 ​mV at a current density of 10 ​mA ​cm−2. A Tafel slope of 42 ​mV dec−1 is recorded in the alkaline electrolyte. The HEA electrocatalyst exhibits good long-term stability for 6 ​h without significant decay under a high constant current density of 100 ​mA ​cm−2. The findings in this study contribute to our basic scientific understanding of catalysts and provide a platform for the further development of HEA-NPs electrocatalysts for large-scale applications.