Oxygen reduction on supported platinum/polythiophene electrocatalysts

This work reports the use of polythiophene films as supporting matrix for Pt particles. The polymer film hosts were prepared using a strong acid aqueous solution, impregnated with Pt particles, and then tested for electrocatalytic properties for the oxygen reduction reaction (ORR). Cyclic voltammetry shows that the redox behavior of polythiophene in 12.5 M H2SO4 presents a general feature equivalent to that of several other conducting polymers, especially polypyrrole. Features of the W-visible spectra obtained during the redox process are consistent with the polaron/bipolaron model. Scanning electron microscopy measurements show that a very homogeneous film layer is obtained with the Pt deposited as very fine particles. Polarization measurements have shown that the ORR occurs through a mechanism involving four electrons 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 Electrochemical Society. All rights reserved.