Francesco P. Orfino

Electrochemical oxygen reduction at composite films of Nafion®, polyaniline and Pt

Abstract Conducting polymer composite films comprised of polyaniline (PANI) and Nafion are prepared and investigated as a matrix for platinum (Pt) particles deposited both chemically and electrochemically. The resulting electrocatalytic films are assessed with respect to their potential use for the electrochemical reduction of oxygen. The permeability of a PANI—Nafion film to dissolved oxygen is determined to be ∼50% larger when compared to PANI—camphorsulfonic acid (CSA). A chemical method for dispersing Pt in the composite films is developed which makes use of the reducing power of alcohols present in commercial Nafion solution. Films cast from a solution of PANI and Nafion containing chemically reduced platinum demonstrate a marked improvement in electrocatalytic activity compared to films prepared in the absence of PANI. These composite films are compared with films cast from a suspension of Nafion, PANI and Pt black, with similar results.

The role of impurities on the electron paramagnetic resonance response of polarons in conjugated polymers.

Abstract Poly(3-hexylthiophene) prepared by oxidative coupling vising ferric chloride and with varying residual impurity levels of Fe, was used to study the temperature dependence of charge carriers in conjugated polymers. The temperature was ramped from room temperature to 110 K and Electron Paramagnetic Resonance (EPR) data for the iron impurity as well as the polymer were obtained. The doubly integrated area of the dispersion curves due to the polymer and the Fe impurity were calculated and show that the former exhibits a Curie Law behavior while the latter exhibits an exponential behavior on a background of immobile charge carriers. The exponential behavior is characteristic of a charge transfer complex (CTC) with a thermally activated excited state whose activation energy was calculated to be: E CTC = (3.3 ± 0.5) × 10 −2 eV and the background component which is independent of temperature was: S o = (7.5 ± 0.5) × 10 16 spins/g.

Quantification of Material Property Changes During Electrode Degradation in Polymer Electrolyte Fuel Cells Using X-ray Computed Tomography

Recent developments in lab-based X-ray Computed Tomography (XCT) systems has provided the ability to obtain non-destructive 3-dimensional imaging in numerous research fields, such as geology, materials science, and biomedical imaging [ 1]. A unique and prevalent application of this technique is to acquire a set of topographies at different experimental stages to assess any dynamic changes and obtain 4-dimensional imaging of a system under study [ 2]. This methodology is well suited for the study of polymer electrolyte fuel cell systems where detailed imaging of the membrane electrode assembly (MEA) can be obtained while it is still assembled in its operational housing [ 3].