High temperature polymer electrolyte fuel cells (HT-PEFC) are a promising power source for many applications. Recent works on the development of HT-PEFC are focused mostly on the performance and technical optimization. However, the fundamental investigation of the proton conductivity will help to optimize performance and increase sufficiency of the fuel cells. For example, the understanding of proton diffusion mechanism in membrane electrode assembly (MEA) plays a key role in proton conductivity of fuel cells. Polybenzimidazole-type membranes doped with phosphoric acid (PA) are used in HT-PEFC. A membrane is located between two catalytic layers of electrodes. The performance of the fuel cell depends on the distribution and amount of PA in the catalytic layer as well as on the interaction of PA with catalyst material. We aim to characterize the proton diffusion of PA in the catalytic layer depending on its Pt content using inelastic fixed window scans. For this purpose we ask for 5 days on IN16B.