Cerium–zirconium mixed oxide synthesized by sol-gel method and its effect on the oxygen vacancy and specific surface area

Highlights: • Synthesis of cerium-zirconium mixed oxide with cetyltrimethylammonium bromide (CTAB). • CTAB acts as a capping agent controlling particle size and specific surface. • CZ synthesized with CTAB has higher oxygen vacancy than the one without surfactant. • Oxygen vacancy is a more important property than specific surface for the activity. • CZ with the lowest surface had the highest O₂ consumption during soot oxidation. In this study, cerium-zirconium mixed oxides were prepared using the sol-gel methodology with cetyltrimethylammonium bromide (CTAB) for tuning the specific surface area and pore volume. The composition of Ce_0.8Zr_0.2O₂ (CZ) was selected as being one of the most active for soot oxidation, which is a concern as an environmental pollutant. The structural and morphological properties were investigated using EDXRF, XRD, SEM/EDS, Raman and N₂ physisorption at low temperature. The catalytic test was evaluated by temperature-programmed oxidation coupled with mass spectrometry (TPO/MS). Any variation in the CTAB concentration during synthesis changed the particle size and surface area, indicating that the particle formation follows a mechanism in which the CTAB acts as capping agent. Additionally, the material synthesized with CTAB was found to have higher oxygen vacancy compared to the materials from the conventional sol-gel process. The catalytic test suggested that the material with the smallest surface area had the lowest temperature of oxidation (T_50%=400°C), which demonstrates that the oxygen vacancy parameter is essentially more important than the specific surface area itself.