CO tolerance and catalytic activity of Pt/Sn/SnO2 nanowires loaded on a carbon paper

Electrochemical activities and structural features of Pt/Sn catalysts supported by hydrogen-reduced SnO2 nanowires (SnO2NW) are studied, using cyclic voltammetry, CO stripping voltammetry, scanning electron microscopy, and X-ray diffraction analysis. The SnO2NW supports have been grown on a carbon paper which is commercially available for gas diffusion purposes. Partial reduction of SnO2NW raises the CO tolerance of the Pt/Sn catalyst considerably. The zero-valence tin plays a significant role in lowering the oxidation potential of COads. For a carbon paper electrode loaded with 0.1 mg cm−2 Pt and 0.4 mg cm−2 SnO2NW, a conversion of 54% SnO2NW into Sn metal (0.17 mg cm−2) initiates the COads oxidation reaction at 0.08 V (vs. Ag/AgCl), shifts the peak position by 0.21 V, and maximizes the CO tolerance. Further reduction damages the support structure, reduces the surface area, and deteriorates the catalytic activity. The presence of Sn metal enhances the activities of both methanol and ethanol oxidation, with a more pronounced effect on the oxidation current of ethanol whose optimal value is analogous to those of PtSn/C catalysts reported in literature. In comparison with a commercial PtRu/C catalyst, the optimal Pt/Sn/SnO2NW/CP exhibits a somewhat inferior activity toward methanol, and a superior activity toward ethanol oxidation.