XPS ANALYSIS OF PTFE DECOMPOSITION DUE TO IONIZING-RADIATION

X-ray induced photoelectron spectroscopy (XPS) in combination with depth profiling has been used to investigate the structure and the degradation mechanism of PTFE bonded gas diffusion electrodes (GDE). The XP-spectra of these electrodes show distinctly separated binding states of the Cls electrons at E(b) = 292 eV and E(b) = 286 eV. These binding states are related to the carbon in the (CF2)(n) configuration (C1s(CF2)) and the graphite (C1s(graphite)), respectively. The C1s(CF2), signal decreases are induced by both X-ray exposure and ion etching. Simultaneously a decrease of the F1s signal has been approved. The intensity ratio of F1s to C1sCF(2) has increased during the experiment. These results indicate a decomposition of PTFE which creates CF fractions, leading to an excess intensity in the energetic range between the C1s binding states of the PTFE and the graphite. Although both the Fls and the C1s spectra are strongly modified by ionizing radiation, samples are comparable, when exposition doses are equal.