Abstract
In order to develop a novel anode catalyst for a PEFC, the Pt thin film and the Pt oxide thin film were produced by reactive sputtering, and the catalytic activity of the H2 oxidation in the presence of CO or the tolerance to the CO poisoning was evaluated by the anodic polarization in an H2-saturated H2SO4 solution or a (H2 + CO)-saturated one. The H2 oxidation activity of the Pt thin film remarkably deteriorated due to the CO poisoning. On the other hand, the electrochemical reduction produced a tolerance to the CO poisoning during the H2 oxidation of the Pt oxide thin film. For the Pt oxide thin film electrochemically reduced at −0.3 C, the H2 oxidation current in a (H2 + 100 ppm CO)-saturated solution remained at the same level as in the H2-saturated one. The CO stripping voltammetry also revealed that the CO coverage was only 0.15 for the electrochemically reduced Pt oxide thin film although the CO coverage on the Pt thin film was calculated to be 0.95. Therefore, the electrochemically reduced Pt oxide may be a promising anode catalyst of the PEFC having a tolerance to CO poisoning. Moreover, the XPS analysis showed that there was a distinct difference in the chemical bonding state between the Pt thin film and the electrochemically reduced Pt oxide thin film. That is, a large spectrum due to the Pt-O bond was detected for the electrochemically reduced Pt oxide thin film, while the spectrum scarcely appeared for the Pt thin film. These results suggested that the residual oxygen might improve the tolerance to the CO poisoning during the H2 oxidation of the electrochemically reduced Pt oxide thin film.
