In-situ x-ray absorption experiments with a PEM fuel cell in hydrogen and methanol operation mode

In-situ XAS studies have been carried out on PEM fuel cells in methanol and hydrogen operation. This has become possible due to a recently developed PEM fuel cell (single cell) equipped with inherent carbon fibre windows to allow x-ray studies in transmission geometry. The set-up chosen allows the in-situ monitoring of the structural changes of the Pt-Ru catalyst, utilised as electrode active material, during cell operation. The analysis of the white line intensities, edge shifts of the Pt-Lш edge and the XAFS signal, which was modelled for the first co-ordination shell around Platinum, exhibited no significant changes during operation in terms of the first neighbouring shell. Nevertheless, the white line intensity decreased comparing the ex-situ to in-situ measurements. From the latter, can be concluded that the catalyst is reduced during operation and further, the redox behaviour of the catalyst does not change the local environment of the Pt-centres in the first co-ordination shell to a measurable extend.