Manganese Defective Clustering: Influence on the Spectroscopic Features of Ceria-Based Nanomaterials
Derance Amaral, L.S.R. Rocha, Luis I. Granone, M. M. Lage, María Sandra Churio, Miguel Sánchez, E. Longo, Hugo Marlon da Silva Nascimento, Marcelo Assis, F. Moura, M.A. Ponce
Abstract
The influence of manganese modification on the spectroscopic features of manganese-doped CeO 2 systems synthesized by the microwave-assisted hydrothermal route and their correlation with the presence of O defective structures were verified, focusing on their interaction with poisonous atmospheres. Raman and electron paramagnetic resonance studies confirmed the presence of defective clusters formed by dipoles and/or quadrupoles. The number of paramagnetic species was found to be inversely proportional to the doping concentration, resulting in an increase in the Mn 2+ signal, likely due to the reduction of Mn 3+ species after the interaction with CO. X-ray photoelectron spectroscopy data showed the pure system with 33% of its cerium species in the Ce 3+ configuration, with an abrupt decrease to 19%, after the first modification with Mn, suggesting that 14% of the Ce 3+ species are donating one electron to the Mn 2+ ions, thus becoming nonparamagnetic Ce 4+ species. On the contrary, 58% of the manganese species remain in the Mn 2+ configuration with five unpaired electrons, corroborating the paramagnetic feature of the samples seen in the electron paramagnetic resonance study.