High-Temperature Synthesis of High-Entropy Alloy PtPd_CoNiCu Nanoparticles as a Catalyst for the Oxygen Reduction Reaction

The aim of this work was high-temperature synthesis of PtPdCoNiCu/C nanoparticles with high-entropy alloy (HEA) structure as catalysts for oxygen reduction reaction. The materials were synthesized using a highly dispersed PtPd/C support, which was impregnated with Cu, Ni, and Co precursors followed by their precipitation with an alkali. Subsequently, the material was subjected to thermal treatment in a tube furnace at 600 °C for 1 h in a stream of argon containing 5% hydrogen. In combination with HRTEM, element mapping and line scan, XRD, and XPS data, these results confirm the successful synthesis of five-component PtPdCoNiCu high-entropy alloy nanoparticles on the surface of the carbon support. The obtained materials are characterized by a high electrochemical surface area of up to 63 m²/g(PGM), as determined by hydrogen adsorption/desorption and CO-stripping, and a high specific oxygen reduction reaction (ORR) activity of approximately 269 A/g(PGM) at 0.9 V vs. RHE. The synthesized material demonstrated outstanding stability, as confirmed by an accelerated stress test of 10,000 cycles. After the test, the electrochemical surface area decreased by only 12%, while the catalytic activity for ORR even increased. The proposed synthetic strategy opens a new pathway for obtaining promising highly stable five-component HEA nanoparticles of various compositions for application in catalysts.