PREPARATION AND ELECTROCATALYTIC PROPERTIES OF PLATINUM MICROPARTICLES INCORPORATED INTO POLYVINYLPYRIDINE AND NAFION FILMS

The deposition of platinum in Nafion (NF) and polyvinylpyridine (PVP) films (d = 1 mu m) was carried out from 5 mM Na2PtCl4 + 0.5 M H2SO4 an d 5 mM Na2PtCl4 + 0.05 M H2SO4 + 0.5 M Na2SO4 solutions potentiostatic ally (at 0.1 V vs RHE). The possibility is shown of preparing ultradis persed deposits with a particle diameter of similar to 3 nm. The rate of hydrogen evolution on Pt deposits in NF and PVP films in the range of small overvoltage (eta < 30 mV) is limited by the removal of hydrog en from the external surface of the electrode. For Pt/NF/GC electrodes this process occurs at smaller overvoltage values than that on a smoo th Pt surface. The higher hydrophobicity of the Pt/NF surface probably facilitates the formation of bubbles and reduces hydrogen supersatura tion in the near-electrode layer. The electrocatalytic behavior of pla tinum deposits in NF and PVP was studied in the reaction of methanol a nd formic acid oxidation. The role of the dimensional effect and metal particles interaction with the polymeric matrix in electrocatalytic p rocesses was demonstrated. In the Pt/PVP/GC system, the first effect i s more pronounced, and in the Pt/NF/GC system the second effect is pre dominant. (C) 1998 Elsevier Science Ltd. All rights reserved.