Raman scattering of MnOxCeOx composite catalysts: structural aspects and laser-heating effects

Composite MnOxCeOx catalysts (Mnat: Ceat = 1) synthesized via the redox and coprecipitation routes were comparatively characterized by micro‐Raman spectroscopy using a laser irradiation power ranging between 0.6 and 4.2 mW. A quasi‐molecular dispersion of the oxide species determines a major and irreversible structural rearrangement of the redox MnOxCeOx system because of severe heating effects for laser power in excess of 0.6 mW. The X‐ray diffraction data of samples calcined in the range of 6731273 K confirm that the micro‐Raman characterization of the composite MnOxCeOx systems requires an adequate minimization of the irradiation power to prevent the strong sintering and restructuring phenomena due to laser‐heating effects. Copyright © 2011 John Wiley & Sons, Ltd. A nanostructured composite MnOxCeOx catalyst was synthesized via the redoxprecipitation route in comparison to the classical co‐precipitation method and characterized by XRD and micro‐Raman spectroscopy measurements under different cycles of laser irradiation power (0.6 → 4.2 → 0.6 → 4.2 mW). The new material appears mostly as an amorphous system where MnOx and CeO2 phases are mixed at the near‐molecular level. Laser heating effects on Raman spectra highlight structural modifications linked to the architecture and the oxide dispersion of the MnOxCeOx system.