Pd core-shell alloy catalysts for high-temperature polymer electrolyte membrane fuel cells: Effect of the core composition on the activity towards oxygen reduction reactions

• Published in: Applied catalysis. A, General General, 2018-07, Vol.562, p.250-257
• Main Authors: You, Dae Jong, Kim, Do Hyung, De Lile, Jeffrey Roshan, Li, Chengbin, Lee, Seung Geol, Kim, Ji Man, Pak, Chanho
• Format: Article
• Language: English
• Subjects: Carbon; Catalysis; Catalysts; Catalytic activity; Composition effects; Compressive properties; Copper; Core-shell catalyst; Core-shell particles; Core-shell structure; Electric potential; Electrolytes; Electrolytic cells; Electron energy loss spectroscopy; Energy dissipation; Fuel cells; Heat resistant alloys; High-temperature polymer electrolyte membrane fuel cell; Iridium; Lattice strain; Membrane electrode assembly; Nanoalloys; Nanoparticles; Nickel; Oxygen reduction reaction; Oxygen reduction reactions; Palladium alloy; Palladium base alloys; Polymers; Proton exchange membrane fuel cells; X-ray diffraction
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2018.06.018

[Display omitted] •Three catalysts with PdNi, PdNiCu and PdCu cores and a PdIr shell were prepared by polyol method and galvanic replacement.•A membrane electrode assembly with PdNiCu@PdIr/C catalyst showed the significantly improved performance and durability.•The core component of core-shell catalysts has important role to improve the activity toward the oxygen reduction reaction. Pd-based core-shell alloy-supported catalysts were prepared sequentially via a microwave-assisted polyol method and galvanic replacement. To investigate the effect of the core composition on the catalytic activity of such catalysts, three different Pd alloy cores (PdNi, PdCu, and PdNiCu) were prepared on carbon supports using a polyol method. Then, Pd and Ir were introduced simultaneously to form shells on the Pd alloy cores by galvanic replacement in aqueous solution, thereby producing catalysts designated as PdNi@PdIr/C, PdCu@PdIr/C, and PdNiCu@PdIr/C. X-ray diffraction revealed that all three catalysts exhibited the face-centered cubic structure of Pd without the presence of individual phases for Ni, Cu, and Ir. The core-shell structure of the Pd-based alloy nanoparticles on the carbon support was verified by the electron energy loss spectroscopy line profile of a 25 nm nanoparticle of PdNiCu@PdIr/C. Among the three Pd-based core-shell catalysts, the highest electrochemical surface area and oxygen reduction reaction (ORR) activity was observed for PdNiCu@PdIr/C. In addition, the membrane electrode assembly employing the PdNiCu@PdIr/C catalyst displayed a significantly improved voltage compared to the other two catalysts under high-temperature polymer electrolyte membrane fuel cell conditions at 150 °C. Single-cell durability tests conducted to measure the voltage change at a constant current density of 0.2 A cm−2 showed a decay ratio of 12.3 μV h−1. These results suggest that the composition of the core in core-shell nanoparticles has an important influence on both the electronic properties in the Pd alloy core and compressive lattice strain on the PdIr shell. Control of these synergistic effects provides a new approach for developing catalysts with high ORR activity.