Polymer electrolyte membrane fuel cells are promising systems in a future sustainable energy scenario. In the so-called power-to-gas strategy, the supply of hydrogen produced by intermittently available wind and solar energy will be converted into electricity on demand using a combination of water electrolysis and fuel cells. However, in order to make this dream a viable reality, material costs need to be dramatically reduced and material stability significantly enhanced.

State-of-the-art catalysts for fuel cell applications are Pt nanoparticles supported on various carbon substrates, predominantly carbon black, but also carbon nanotubes or graphene. However, in the harsh conditions at the fuel cell cathode, carbon is not stable and catalyst degradation due to carbon support corrosion becomes a key issue. One concept towards enhanced durability is to replace carbon by more stable support materials, such as electron-conducting (doped) oxides. Substituting carbon by e.g. tin oxide can alter the catalytic activity significantly, as in contrast to carbon supports the oxide phase may take part in the electrocatalytic reaction (so-called metal-support interaction).

We use CO as a probe molecule to study the interaction between Pt nanoparticles and the support, as the CO-Pt adsorption is affected by the support underneath the Pt nanoparticles. A novel in-situ cell was developed to allow for a combination of X-ray absorption spectroscopy (XAS) and diffuse infrared Fourier transform reflectance spectroscopy (DRIFTS) at the same time and with high quality [1, 2]. We thus benefit from the DRIFTS being able to distinguish between different CO binding sites (atop, bridge, analyzed also by DFT calculations [3]) and XAS being able to probe adsorption and nanoparticle structure. Differences in gas phase IR spectra during static and continuous CO adsorption on platinum nanoparticles reveal information on the influence of the support as well as on the binding sites. In this study, XAS and DRIFTS were recorded simultaneously for Pt/C, Pt/SnO₂, Pt/ATO and Pt/ITO and analyzed with respect to kind of surface adsorbates, binding sites, coverage as well as nanoparticle structure.

[1] A. Drochner, M. Fehlings, K. Krauss, H. Vogel, Chem. Eng. Technol. 23 (2000) 319-322.

[2] C. Brieger, J. Melke, N. van der Bosch, A. Schökel, M. Krishna, I. Derr, M. Labza, C. Roth, J. Catal. 339 (2016) 57-67.

[3] C. Lentz, S. P. Jand, J. Melke, C. Roth, P. Kaghazchi, J. Molecular Catal. A: Chemical (2016), article in press.