Electrocatalytic properties of polypyrrole films prepared with platinate(II) counter-ions

Polypyrrole/PtCl42- composites were studied with respect to their possible use as a hydrogen electrode, e.g. for fuel cell applications. The impact of composite conditioning on its electrochemical activity for the hydrogen oxidation reaction (HOR) was studied. The cathodic polarization of samples containing a high amount of PtCl42- ions after synthesis leads to the formation of polypyrrole/Pt composites active for HOR. Their behavior is, however, different from that of bulk Pt and strongly depends on the potential at which the reduction proceeds. Both electrochemical and IR measurements displayed the self-degradation of composites exposed to cathodic potentials exceeding a certain level. The presence of metallic Pt is proved by means of X-ray photoelectron spectroscopy (XPS) and the extent of platinate ions reduction/motion is discussed. Subsequently the possibility of tuning composite activity by changing the thickness or using a competing counter-ion during synthesis was tested. (C) 2005 Elsevier B.V. All rights reserved.