Oxygen reduction on supported platinum/polythiophene electrocatalysts

This work reports the use of polythiophene films as supporting matrix for P t particles. The polymer film hosts were prepared using a strong acid aqueo us solution, impregnated with Pt particles, and then tested for electrocata lytic properties for the oxygen reduction reaction (ORR). Cyclic voltammetr y shows that the redox behavior of polythiophene in 12.5 M H2SO4 presents a general feature equivalent to that of several other conducting polymers, e specially polypyrrole. Features of the W-visible spectra obtained during th e redox process are consistent with the polaron/bipolaron model. Scanning e lectron microscopy measurements show that a very homogeneous film layer is obtained with the Pt deposited as very fine particles. Polarization measure ments have shown that the ORR occurs through a mechanism involving four ele ctrons with Tafel slopes of ca. 0.12 V dec(-1) for potentials below 0.85 V vs. RHE (reference hydrogen electrode), in agreement with previous results for other types of dispersed Pt electrocatalysts. (C) 2001 The Electrochemi cal Society. All rights reserved.