Ceria-Based Catalysts for Soot Oxidation

Ceria (CeO₂)-based materials have emerged as leading candidates for catalytic soot oxidation owing to their remarkable oxygen storage capacity, facile redox cycling between Ce³⁺ and Ce⁴⁺ and tunable surface defect structure. By engineering particle morphology, surface area and doping with aliovalent cations such as Mn, Cu, Zr or Pr, researchers have tailored the concentration and mobility of oxygen vacancies to enhance the activation of lattice and adsorbed oxygen species. Nanostructuring into rods, cubes, fibres or stars increases soot-catalyst contact points, mitigating the solid–solid interface challenge inherent to particulate oxidation. The interplay between oxygen vacancy density, redox capacity and soot adhesion underpins catalytic performance, allowing ignition temperatures to fall by over 250 °C compared with uncatalysed combustion. Practical implementation in diesel and gasoline particulate filters leverages these advances to meet stringent emission regulations and reduce particulate matter in urban environments, while offering a lower-cost alternative to noble-metal systems.

Research from Nature Portfolio

Recent studies have exploited in situ Raman spectroscopy to follow defect evolution during soot oxidation over hydrothermally synthesised CeO₂ doped with Cu and Mn. Findings reveal that an intermediate density of oxygen vacancies—achieved with 5 % Mn doping—optimises soot conversion by balancing oxygen activation and catalyst reversibility. Excessive vacancy concentrations lead to peroxide or superoxide deactivation at high temperature, underscoring the critical role of defect dynamics. Earlier work on nanostructured morphologies demonstrated that ceria nanorods outperform nanoparticles and flakes under both loose and tight contact conditions. The high concentration of surface-adsorbed oxygen species and elevated BET surface area of the rod-shaped catalyst drive soot combustion peaks below 400 °C, rivalling noble-metal performance and highlighting the importance of shape-controlled synthesis.

Ceria-Based Catalysts for Soot Oxidation publication trend

The graph below shows the total number of articles in ceria-based catalysts for soot oxidation across all publications each year (not limited to Nature Index journals).

Technical terms

Oxygen vacancy: A lattice defect where an oxygen ion is missing, facilitating migration of oxygen species and redox reactions.

Redox cycling: Reversible transition between reduced (Ce³⁺) and oxidised (Ce⁴⁺) states in ceria, enabling oxygen storage and release.

Soot-catalyst contact: Physical interface between carbonaceous particles and catalyst surface; tight contact enhances oxidation rates compared with loose contact.

BET surface area: A measure of total surface area per unit mass, determined by nitrogen physisorption; higher values increase active site availability.

In situ Raman spectroscopy: Analytical technique to monitor catalyst structural and defect changes under real-time reaction conditions.

References

1. In situ Raman analyses of the soot oxidation reaction over nanostructured ceria-based catalysts. Scientific Reports (2019).
2. Soot Combustion over Nanostructured Ceria with Different Morphologies. Scientific Reports (2016).
3. Catalytic Soot Oxidation Activity of NiO–CeO2 Catalysts Prepared by a Coprecipitation Method: Influence of the Preparation pH on the Catalytic Performance. Materials (2019).
4. Experimental Evaluation on the Catalytic Activity of a Novel CeZrK/rGO Nanocomposite for Soot Oxidation in Catalyzed Diesel Particulate Filter. Processes (2021).
5. Nanostructured Equimolar Ceria-Praseodymia for Total Oxidations in Low-O2 Conditions. Catalysts (2020).