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Effect of MnO x Loading on Structural, Surface, and Catalytic Properties of CeO 2 ‐MnO x Mixed Oxides Prepared by Sol‐Gel Method
Author(s) -
Jampaiah Deshetti,
Venkataswamy Perala,
Tur Katie M.,
Ippolito Samuel J.,
Bhargava Suresh K.,
Reddy Benjaram M.
Publication year - 2015
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201400615
Subject(s) - raman spectroscopy , x ray photoelectron spectroscopy , catalysis , materials science , redox , doping , bet theory , specific surface area , sol gel , citric acid , analytical chemistry (journal) , inorganic chemistry , chemistry , chemical engineering , nanotechnology , metallurgy , biochemistry , physics , optoelectronics , organic chemistry , chromatography , optics , engineering
Nanosized CeO 2 ‐MnO x mixed oxides with different Ce/Mn ratios were prepared by a citric acid‐assisted sol‐gel method. The effect of the MnO x content on structural, redox, and surface properties of the CeO 2 ‐MnO x was investigated by various techniques, namely, BET surface area, SEM, XRD, ICP‐OES, Raman and FT‐IR spectroscopy, H 2 ‐TPR, and XPS. Catalytic activity was evaluated with soot‐catalyst mixture under tight contact conditions. BET surface area analysis indicated that Mn doping favors an enhancement in the surface area of pure CeO 2 . Raman active peaks for both pure CeO 2 and CeO 2 ‐MnO x mixed oxides were determined at ca. 460 cm –1 . The observed Raman shift can also be assigned to Raman active modes of CeO 2 that are shifted from the original position due to different Mn doping. Formation of Ce 1– x Mn x O 2– δ solid solutions was further confirmed by XRD and FT‐IR analysis. H 2 ‐TPR results demonstrate that Ce 1– x Mn x O 2– δ solid solutions significantly improved the redox property over the pure CeO 2 or MnO x . XPS analysis reveal that Ce is in the form of Ce 4+ and Ce 3+ , and Mn existed in the form of Mn 4+ , Mn 3+ , and Mn 2+ on the surface of the samples. Catalytic activity results indicate that the oxidation temperature of soot can be significantly reduced by CeO 2 ‐MnO x mixed oxides, which render higher Ce 3+ concentration and more surface oxygen vacancies compared with pure CeO 2 . Particularly, the Ce 0.7 Mn 0.3 O 2– δ sample exhibited highest activity (a shift of T 50 by ca. 122 K) compared to pure ceria.