Synthesis and characterization of Pt3Co alloy magnetic nanoparticles in multidomain region for oxygen reduction reaction catalysts in PEMFCs

Abstract

The structural and electrochemical characteristics of Pt3Co alloy nanoparticles as novel magnetic catalysts are investigated experimentally to improve the performance of the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). Pt3Co alloy nanoparticles are synthesized using a wet chemical reduction and seed-mediated method. The synthesized Pt3Co alloy nanoparticles are annealed at 400 °C (Pt3Co-400) and 700 °C (Pt3Co-700) to increase the remanent magnetizations. The synthesized Pt3Co alloy nanoparticles for magnetic catalysts are characterized using physicochemical and electrochemical methods. Physicochemical tests confirm that the Pt3Co alloy nanoparticles are properly synthesized with the desired atomic ratio for magnetization in the multidomain region. The remanent magnetizations of the Pt3Co alloy nanoparticles substantially increase after annealing at 400 °C. For the rotating ring-disk electrode tests, the electrocatalytic performance improvement of Pt3Co alloy nanoparticles by magnetization is very small under the liquid electrolyte condition. However, the performances of PEMFCs using Pt3Co-400 alloy nanoparticles are substantially improved after magnetization owing to the enhanced ORR activities and oxygen diffusivity. In addition, the optimal operating conditions for PEMFCs using Pt3Co-400 magnetic catalysts are determined to be a higher reactant flow rate and lower operating temperature with a Pt-to-Pt3Co-400 mass ratio of 8:2.