In an effort to simultaneously reduce the amount of noble precious metals used in electrochemical catalysts and increase the catalytic activity for oxygen reduction, a novel method of synthesis that involves electroless deposition (ED) of a Pt salt on a carbon support that has been previously seeded with a group VIIIB metal as been developed. To increase the activity of Pt based electrocatalysts for oxygen reduction, others [1] have shown that it is desirable to combine Pt with a base metal; unfortunately, the acidic environment within a fuel cell cathode quickly leaches out any base metals found on the surface of the nanoparticles. ED provides the opportunity to both protect the base metal and reduce the quantity of Pt in the electrocatalysts by producing core/shell structures. In this configuration, the Pt should protect the base metal from corrosion while being limited to only a few monolayers around the base metal core.

This presentation illustrates aspects of ED to give this preferred core-shell type structure as well as how the controlled deposition of Pt gives an overall reduction in metal particle size and a more efficient utilization of the expensive Pt component. X-ray photoelectron spectroscopy (XPS) is used to provide strong evidence of a core/shell and solid solution for Pt electrolessly deposited on Co and Pd respectively while HRTEM confirms both the synthesis of smaller Pt-containing particles and core/shell structured particles using ED methods. The oxygen reduction activity of the synthesized ED catalysts is determined using a rotating disc electrode (RDE) to correlate the promoter effect of possible electronic interactions between the precursor base metal and the electrolessly-deposited Pt on overall fuel cell performance.

References:

[1] T. Toda, H. Igarashi, H. Uchida, M. Watanabe, Journal of the Electrochemical Society, 146 (1999) 3750 - 3756.