Manganese Defective Clustering: Influence on the Spectroscopic Features of Ceria-Based Nanomaterials

Theinfluence of manganese modification on the spectroscopic featuresof manganese-doped CeO2 systems synthesized by the microwave-assistedhydrothermal route and their correlation with the presence of O defectivestructures were verified, focusing on their interaction with poisonousatmospheres. Raman and electron paramagnetic resonance studies confirmedthe presence of defective clusters formed by dipoles and/or quadrupoles.The number of paramagnetic species was found to be inversely proportionalto the doping concentration, resulting in an increase in the Mn2+ signal, likely due to the reduction of Mn3+ speciesafter the interaction with CO. X-ray photoelectron spectroscopy datashowed the pure system with 33% of its cerium species in the Ce3+ configuration, with an abrupt decrease to 19%, after thefirst modification with Mn, suggesting that 14% of the Ce3+ species are donating one electron to the Mn2+ ions, thusbecoming nonparamagnetic Ce4+ species. On the contrary,58% of the manganese species remain in the Mn2+ configurationwith five unpaired electrons, corroborating the paramagnetic featureof the samples seen in the electron paramagnetic resonance study. The impact of manganese modificationon the spectroscopicfeatures of microwave-assisted hydrothermally synthesized manganese-dopedCeO(2) systems was studied. Raman and electron paramagneticresonance confirmed defective cluster formation with dipoles and/orquadrupoles. A higher level of doping led to fewer paramagnetic speciesand an increased Mn2+ signal due to Mn3+ reductionupon CO interaction. X-ray photoelectron spectroscopy revealed a Ce3+ level of 33% in the pure system, which decreased to 19%after the first Mn modification, suggesting the donation of an electronto Mn2+ ions forming nonparamagnetic Ce4+ species;58% of Mn species remained as Mn2+, confirming the paramagneticnature seen in electron paramagnetic resonance studies.