Stability of PtZn Nanoparticles Supported on Carbon in Acidic Electrochemical Environments

The stability of Pt and PtZn alloy nanoparticles supported on glassy carbon toward metal dissolution during oxygen reduction reaction (ORR) is detailed. The Pt/Zn nanoparticles were created using sequential electrodeposition steps. The electrochemically created particles are approximately 1:1 Pt:Zn, the as-created particles having a Pt rich surface as determined by Auger electron spectroscopy. The Pt particles were found to be spherical, while the Pt/Zn particles were oddly shaped. These Pt and PtZn particles were subjected to durability tests at various potentials in oxygen saturated H2SO4. The surface composition of the PtZn particles was analyzed after fixed times at 0.75, 1.0, and 1.25 V/RHE. The Zn surface content was unchanged over 14 h at 0.75 V, substantially increased when conditioned at 1.0 V, and the Zn was absent from the surface after 2.5 h at 1.25 V. The Pt and PtZn nanoparticles were further analyzed using tapping mode AFM which found that the PtZn particles were more strongly adhered to the GC substrate as compared to similarly prepared Pt nanoparticles. Heating at 120 degrees C for 2 h caused the Pt nanoparticles to grow by aggregation, while the PtZn particles became more spherical. These measurements suggest that the PtZn alloy is stable at potentials less than 1.0 V/RHE during ORR, and that the PtZn alloy is more strongly adhered to the carbon surface than Pt.