Activation/inhibition effects during the coelectrodeposition of PtAg nanoparticles: application for ORR in alkaline media.

PtAg bimetallic nanoparticles for oxygen reduction reaction (ORR) in alkaline media were prepared by pulse electrodeposition (PED). During PED the reduction of Ag(+) ions predominates, thus an increased Ag content in the co-deposit is accomplished. The mechanism for this anomalous co-deposition was elucidated by potential pulse experiments, which revealed that nuclei formation mainly occurs via the reduction of Pt(2+) ions. The growth of the particles is diffusion controlled leading to the formation of a Ag shell covering a PtAg alloyed region. However, the shell is not growing homogeneously on the PtAg alloy. Hence, regions of the PtAg alloy are exposed, which exhibit an enhanced ORR activity compared to a pure Ag surface.