Long‐term stability is a major issue in heterogeneous catalysis and is often related to structural instabilities, which are difficult to assess in the early stage of catalyst screening. However, studies of morphological transformations in catalytic systems can greatly benefit from a well‐defined starting morphology and microstructure of the catalyst to be analysed. The present study suggests the use of catalysts in the form of 1 D nanofibres (NFs) as a conceptual methodology to assess catalyst stability, which is exemplified for the HCl oxidation reaction. These nanostructured model catalysts are synthesised by electrospinning, a versatile method to produce metal oxide NFs. We have studied the stability of RuO2‐ and CeO2‐based materials in the harsh HCl oxidation reaction (Deacon process). At 573 K pure RuO2 NFs have shown to be morphologically unstable, whereas mixed RuO2‐TiO2 NFs are stable. The stability of CeO2‐based NFs in the HCl oxidation was studied at 703 K. Under HCl lean conditions CeO2 NFs are stable, whereas under HCl rich conditions pure CeO2 NFs disintegrate by recrystallisation, forming (hydrated) Ce‐chloride. If CeO2 is doped with 20 % of Zr, the resulting mixed oxide Zr0.20Ce0.80O2 NFs have shown to be stable even under HCl rich reaction conditions and are similarly active as pure CeO2. These are the first activity experiments of mixed oxide ZrxCe1−xO2 in the Deacon process. The versatility of electrospun NFs as model catalysts has been demonstrated for testing catalyst stability in terms of morphology changes, thus serving as a proof‐of‐principle study.

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