Understanding the Metal Carbonyl-Assisted Synthesis of PtMoCu/C Nanocatalysts for Proton-Exchange Membrane Fuel Cells

Pt-based alloy nanoparticles (NPs) are being developed as oxygen reduction reaction (ORR) electrocatalysts in proton-exchange membrane fuel cells (PEMFCs) by improving the electrocatalytic activity and stability of Pt and reducing its utilization. Metal carbonyls are an effective source for synthesizing Pt alloy NPs. However, the role of metal carbonyls and their effect on the synthesis of Pt alloy NPs are unclear. Herein, we report the formation mechanism of PtMoCu NPs by controlling the Mo­(CO)6 source and analyzing the reaction intermediates. We determined that sufficient Pt–organic complexes should be created in order that the rapidly released Mo and carbonyl from Mo­(CO)6 enable the formation of ultrafine monodispersed PtMoCu NPs. Specifically, PtMoCu/C with a low Pt content exhibits mass (241.0 A gPt –1) and specific activities (0.74 mA cmPt –2) for ORRs that are 1.5 and 1.6 times, respectively, higher than those of PtMoCu-SCR/C (synthesized through a slow carbonyl release process). More significantly, 81% of the mass activity of PtMoCu/C was retained after 10,000 cycles of accelerated durability test, which is much higher than that of PtMoCu-SCR/C (38%) and benchmark Pt/C (44%). Additionally, a practical PEMFC, fabricated with a membrane electrode assembly with PtMoCu/C, shows a high power density (1.3 W cm–2).