This project aims to improve our understanding of degradation phenomena related to the oxidation of small Pt nanoparticles (NP) electrocatalysts for polymer electrolyte fuel cell (PEMFC) operation. We will combine operando scattering techniques (SAXS and PDF) with high-energy X-ray spectroscopy to study Pt oxidation to follow catalyst restructuring under operating conditions, by comparing the degradation in a gas diffusion electrode (GDE) setup and a full PEMFC. We will apply the new concept of operando SAXS/PDF measurements to probe the atomic structure of small Pt catalysts, lacking long-range order. Combining operando PDF/SAXS with X-ray fluorescence spectroscopy measurements enables a unique structural understanding of the oxidation process of Pt NPs of different sizes. This is crucial to understand the degradation and dissolution behavior of small NPs in GDEs and will allow us to develop a full degradation model.