Synthesis of Chemically Ordered Pt₃Fe/C Intermetallic Electrocatalysts for Oxygen Reduction Reaction with Enhanced Activity and Durability via a Removable Carbon Coating

Recently, Pt 3 M (M = Fe, Ni, Co, Cu, etc.) intermetallic compounds have been highlighted as promising candidates for oxygen reduction reaction (ORR) catalysts. In general, to form those intermetallic compounds, alloy phase nanoparticles are synthesized and then heat-treated at a high temperature. However, nanoparticles easily agglomerate during the heat treatment, resulting in a decrease in electrochemical surface area (ECSA). In this study, we synthesized Pt–Fe alloy nanoparticles and employed carbon coating to protect the nanoparticles from agglomeration during heat treatment. As a result, Pt 3 Fe L1 2 structure was obtained without agglomeration of the nanoparticles; the ECSA of Pt–Fe alloy and intermetallic Pt 3 Fe/C was 37.6 and 33.3 m 2 g Pt –1, respectively. Pt 3 Fe/C exhibited excellent mass activity (0.454 A mg Pt –1 ) and stability with superior resistances to nanoparticle agglomeration and iron leaching. Density functional theory (DFT) calculation revealed that, owing to the higher dissolution potential of Fe atoms on the Pt 3 Fe surface than those on the Pt–Fe alloy, Pt 3 Fe/C had better stability than Pt–Fe/C. A single cell fabricated with Pt 3 Fe/C showed higher initial performance and superior durability, compared to that with commercial Pt/C. We suggest that Pt 3 M chemically ordered electrocatalysts are excellent candidates that may become the most active and durable ORR catalysts available.