Liquid-phase microwave synthesis of platinum-based high-entropy alloy catalysts on carbon supports for electrochemical hydrogen adsorption/desorption and oxygen evolution/reduction reactions

Abstract

This study utilizes a pulse microwave-assisted technique to develop Pt and Pt-based high-entropy alloy (HEA) catalysts. The resulting catalysts exhibited remarkable catalytic activities and exceptional durability in hydrogen adsorption/desorption, oxygen reduction reaction (ORR), and oxygen evolution reaction (OER). During the synthesized process, the growth temperature emerges as a critical factor influencing the average particle size, crystallinity, and deposition rate of nanoparticles on the oxidized carbon support. The results indicate that Pt nanoparticles synthesized at a temperature of 100 °C display an elevated number of active sites for hydrogen adsorption and desorption. The Arrhenius plot reveals an apparent activation energy of 10.2 kJ mol⁻¹ (2.4 kcal mol⁻¹), which is substantially lower than the previously reported values for Pt deposits synthesized using the chemical reduction approach. Furthermore, the pulse microwave heating method was employed to synthesize HEA catalysts on carbon supports. These HEA catalysts were identified as Pt_42·9Al_6·1Ni_5·6Cu_22·3Sn_23.1 alloys. On the surface of the HEA, the presence of multiple metal dopants within the Pt-rich crystals enhances the number of oxygenated sites, improving catalytic stability. This enhancement is attributed to the lower electronegativity of Al, Ni, Cu, and Sn compared to Pt. The HEA catalyst not only demonstrates superior catalytic activity but also exhibits greater durability in both ORR and OER, as compared to pure Pt catalysts. Based on the analysis of linear sweep voltammetry and Tafel plots, the design of the HEA@C catalyst enables enhanced catalytic activity and a faster chemical redox kinetics in the ORR. Pulse microwave synthesis shows promise as a means for synthesizing HEA catalysts with sustained catalytic activity and long-term durability for fuel cell applications, without further treatments.