Effect of Valency of Sn in Sn-Modified Pt-Ru Catalyst on CO Tolerance and HOR Activity for PEFC

Bimetallic Pt-Ru catalysts and addition of SnO2 to the carbon support have been shown to enhance CO tolerance for polymer electrolyte fuel cells (PEFCs). We have investigated the effect of valency of Sn in Sn-modified Pt-Ru catalyst on CO tolerance and hydrogen oxidation reaction (HOR) activity. During a rapid quenching method for catalyst preparation, Pt-Ru-Sn/C and Pt-Ru/SnO2/C were treated in H2 and He at 880 oC, respectively. Without CO contamination, the terminal voltage of the cell using Pt-Ru-Sn/C is lower than those using Pt-Ru/SnO2/C or commercial Pt-Ru/C (TKK, TEC61E54). In the presence of 1000-ppm CO contamination, the terminal voltage of the cell using Pt-Ru/SnO2/C is the highest, followed by Pt-Ru-Sn/C and Pt-Ru/C (TKK, TEC61E54). It is concluded that Sn in the Pt-Ru-Sn alloy reduces the HOR activity, while SnO2 does not. Both of metallic Sn in the Pt-Ru-Sn alloy and SnO2 encourage the CO tolerance.