The Eu 3+ ‐Based Luminescent Marker—A Powerful Tool for Fast Monitoring of Ce 4+ /Ce 3+ Transitions in Ru/Ceria‐Based Catalysts

The main aim of the study was to develop a new, relatively cheap and fast technique to monitor the chemical state of ceria in a Ru/CeO 2 catalyst under operating conditions. Our idea is based on the high sensitivity of the luminescence spectra of Eu 3+ ions, doped into CeO 2 , to the local environment of cationic centers. High sensitivity, together with the relatively low cost of this method, could be demanded in industrial conditions for fast monitoring of the Ce 4+ /Ce 3+ ratio in ceria support. NAP‐XPS and H 2 ‐TPR were used as reference techniques to determine the actual chemical state of the Ru/ceria catalyst under working conditions, necessary to calibrate luminescent data.