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

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.