Gas-Phase Synthesis of PtMo Alloy Electrocatalysts with Enhanced Activity and Durability for Oxygen Reduction Reaction

The proton-exchange membrane fuel cell is a promising technology to effectively utilize hydrogen energy, which is the ideal alternative to fossil fuels. However, the high dependency on scarce Pt as an oxygen reduction reaction (ORR) electrocatalyst is still a severe barrier that hinders widespread commercialization. Herein, we propose a facile synthetic strategy facilitating mass production of Pt-Mo solid-solution alloy nanoparticles on a carbon support (PtMo/C) as a highly active ORR electrocatalyst. Without using organic surfactants or reducing agents, our synthesis process based on the gas-phase method in an inert atmosphere is cost-effective and does not require any post-treatment, unlike most reported solution-based reduction processes. Both molybdenum metal and carbon monoxide decomposed from molybdenum hexacarbonyl contribute to the reduction of the PtMo alloy during the annealing process. By elucidating the growth and synthesis mechanisms, we optimized the particle size of PtMo/C to approximately 3.1 nm, annealed at 800 °C (PtMo/C-800). Consequently, PtMo/C-800 shows high mass activity (146 mA mg_Pt^-1), which is superior to that of commercial Pt/C, and excellent durability after accelerated degradation tests.