Confinement-enabled infusion-alloying of iron into platinum nanoparticle for core-shell PtFe@Pt intermetallic electrocatalyst

Abstract

Platinum-based intermetallics are efficient electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs) because of their high catalytic activity and durability. However, conventional manufacturing methods are complex and require high-temperature heat treatment, resulting in reduced uniformity in particle size and composition. Therefore, a facile and efficient synthesis method was developed for intermetallic PtFe@Pt core–shell nanoparticles using ultrasound-assisted coating of FeOx and subsequent post-treatment. Fe atoms in the oxide coatings of Pt@FeOx/C samples were incorporated into the Pt lattices as the heat-treatment temperature increased, resulting in the formation of random PtFe alloy cores at 400 °C and intermetallic PtFe alloy cores at temperatures above 600 °C. Interestingly, PtFe@Pt/C samples annealed at different temperatures had similar particle sizes (5–6 nm) and their PtFe cores were enclosed in 1–2 layers of Pt shells. Electrochemical analysis indicated that compared to the random PtFe core, the intermetallic PtFe core exhibited superior ORR performance owing to the modification of the Pt electronic structure. Additionally, increasing the chemical ordering parameters of the intermetallic PtFe core improved durability. Therefore, ultrasound-assisted metal oxide coating is a promising approach for synthesizing advanced electrocatalysts and, consequently, enhancing the commercial viability of PEFCs as clean energy converting systems.