Long-term stability is a major issue in the development of new catalysts and in the improvement of existing catalysts. In general, high-surface-area materials in catalysis are not well suited as model materials for testing catalyst stability, because changes in the morphology are difficult to recognize with electron microscopy. Therefore, we developed a new type of model catalyst in the form of nanofibers for assessing structural changes of CeO2-based catalysts under highly corrosive Deacon reaction conditions. In the Deacon process, chlorine is recycled by heterogeneously catalyzed gas-phase oxidation of HCl, using metal oxide catalysts. The Deacon process generally suffers from degradation of the catalyst due to in-depth chlorination. One-dimensional CeO2-based nanofibers with a well-defined morphology and surface enable direct visualization of structural changes before and after the Deacon reaction, simply employing scanning electron microscopy supported by X-ray diffraction and physisorption measurements. Preparing solid solutions of CeO2 and ZrO2 has shown to improve both the chemical stability and the activity of the catalyst. (C) 2015 Elsevier B.V. All rights reserved.