Investigation of Carbon Supported Pd, Ag, and Au Catalysts in Alkaline Solutions

The need to use Pt or Pt alloy catalysts in proton exchange membrane (PEM) fuel cells is one of key barriers to commercialize the technology. Our research goals include developing anion exchange membrane and developing non-Pt catalysts for oxygen reduction reaction in alkaline environments. In this work we compared oxygen reduction reaction (ORR) activities of carbon supported Pd, Ag, and Au in alkaline solutions using carbon supported Pt as a reference. We studied the particle size and particle shape effect of the carbon supported Ag and Au on the ORR activity in alkaline solutions.

Carbon supported Ag nanoparticles (NPs), Ag nanowires (NWs), an Au NPs, with an average particle size of 10 and 100 nm were employed as oxygen reduction catalysts in 0.1 M NaOH solutions. 2 e^- pathway is predominant whether on carbon-supported Ag NPs, or on carbon-supported Ag NWs. On carbon supported gold, the 2 e^- pathway is predominant on 100 nm Au NPs/C, and the 4 e^- pathway is predominant on 10 nm Au NPs/C. The improved ORR selectivity on small Au particles might be due to the re-adsorption/re-reduction of peroxides on the Au particles. The onset potential of the ORR on the most active non-Pt catalyst (Au, 10nm) is 200 mV more negative than on the Pt/C catalysts. One of the merits of the non-Pt catalysts studied here that they are insensitive to ethanol as opposed to the Pt catalysts, which are sensitive to ethanol.