Electrocatalytic Oxygen Reduction on Dealloyed Pt1-xNix Alloy Nanoparticle Electrocatalysts

The synthesis, structural, and compositional characterization as well as the electrocatalytic oxygen reduction (ORR) activity of a number of carbon-supported Pt (x) Ni1-x (x = 1.00-0.14) nanoparticles in acidic electrolyte are reported. A number of different low-temperature colloidal synthesis routes were employed to prepare monodisperse, single-phase Pt-Ni alloy nanoparticles. The catalysts were characterized using XRD, TEM, and ICP-OES techniques, subsequently electrochemically dealloyed and, in their dealloyed state, tested for their Pt mass-based ORR activity, specific Pt surface area-based ORR activity. Additional 4,000 voltage cycles were applied to investigate the durability of the electrocatalysts in terms of their electrochemically active surface area and their final ORR activity. It is found that Pt-Ni alloys exhibit a distinctly different dealloying and ORR stability behavior compared to Pt-Co or Pt-Cu alloy nanoparticles. In particular, Pt-Ni alloys require longer cycling times to unfold their full ORR activity. A distinct ORR activity maximum was uncovered for Pt-Ni nanoparticle alloys with initial Ni contents in the neighborhood of 70-75 at.% consistent with results from dealloyed macroscopic Pt-Ni thin films.