Fuel cell technology

Nafion contamination by ferrous-alloy corrosion products, resulting in dramatic drops of the Ohmic potential, is a suspected major failure of polymer electrolyte membrane fuel cells that make use of metallic bipolar plates. The study demonstrates the potential of scanning transmission X-ray microscopy combined with X-ray absorption and fluorescence microspectroscopy for exploring corrosion processes of Ni and Fe electrodes in contact with a hydrated Nafion film in a thin-layer cell.
B. Bozzini et al., ChemSusChem 3, 846 (2010).

The imaged morphology changes of the Ni and Fe electrodes and surrounding Nafion film resulting from relevant electrochemical processes is correlated to the space distribution, local concentration and chemical state of Fe and Ni species. The XRF maps and the XAS spectra, taken in different locations, show diffusion of corrosion products within the Nafion film only in the case of the Fe electrodes, whereas the Ni electrodes appear corrosion resistant. The obtained information is relevant to the fabrication and application of metallic BiPs for PEMFCs, in particular how Fe and Ni films of nanometric thickness were corroded by galvanic coupling to Au in a thin-layer configuration. The obtained morphological and chemical details of the corrosion process and of the fixation of the corrosion products in the Nafion film reveal that corrosion of Fe is characterised by the diffusion of Fe species into the Nafion film, accompanied by changes of the Fe chemical state. As expected, Ni corrosion products are essentially localised at the surface of the Ni electrode without release of Ni species.

This pioneering investigation of an electrochemical system employing simultaneously soft x-ray imaging and two space resolved x-ray spectroscopies demonstrates the power of such approach not only to the system investigated - with potential impact in the acquisition of fundamental information relevant to fuel-cell technology - but potentially to all fields of electrochemical materials science and bioelectrochemistry Retrieve article Metallic Plate Corrosion and Uptake of Corrosion Products by Nafion in Polymer Electrolyte Membrane Fuel Cells; B. Bozzini, A. Gianoncelli, B. Kaulich, M. Kiskinova, M. Prasciolu and I. Sgura; ChemSusChem 3 (7), (2011) 846-850. doi:10.1002/cssc.201000048