The work presented in this thesis is focused on the application of an innovative spectroscopic technique, operando Near Edge X-ray Fine Structure (NEXAFS), to investigate the surface reactivity of Solid Oxide Fuel Cells (SOFCs) electrodes and electrolytes. As this technique requires the use of synchrotron radiation, all the measurements reported in this thesis have been performed by using reaction cells available at the beamlines APE-HE (Elettra Synchrotron Facility, Italy) and BO7-B (Diamond Light Source, UK). In detail, this work was focused on studying the surface interaction with H2 of A-site doped SrTiO3 and BaZr0.6Ce0.2Y0.2O3-, this latter being a proton conductor for intermediate temperature fuel cells. In this regard, operando NEXAFS can give fundamental information on the oxidation state of Ti and Ce in these compounds, therefore helping to correlate their working performance with their chemical structure and reactivity. In this thesis, operando NEXAFS was coupled with other characterization techniques such as XPS, XRD, SEM and DFT simulations to gain a complete overview of the chemical and morphological features of the samples.
