Faculty Publications
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Item Soot Oxidation Activity of Redox and Non-Redox Metal Oxides Synthesised by EDTA–Citrate Method(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Anjana, A.P.; Prasad Dasari, H.P.; Lee, J.-H.; Harshini, H.; Babu, G.U.B.Abstract: In the present study, redox (CeO2, SnO2, Pr6O11 and Mn3O4) and non-redox (Gd2O3, La2O3 ZrO2 and HfO2) metal oxides were successfully synthesised using the EDTA–citrate complexing method and tested for soot oxidation activity. The characterization of the metal oxides is carried out using FTIR, XRD, BET surface area, pore volume analyser, SEM and TEM. The redox nature and metal–oxygen bond information of the metal oxides are obtained from XPS analysis. In redox metal oxides, three critical parameters [lattice oxygen binding energy, reduction temperature and ?r (ionic size difference of the corresponding metal oxide oxidation states)] govern the soot oxidation activity. Among the redox metal oxide samples, Mn3O4 and Pr6O11 samples showed lower binding energy for oxygen (O?—529.4, 528.9 eV respectively), lower reduction temperature (T?—317 and 512 °C respectively) and have smaller ?r value (9 pm and 17 pm respectively). Thus, displayed a better soot oxidation activity (T50 = 484 and 482 °C respectively) than compared to other redox metal oxides. Among the non-redox metal oxides, HfO2 sample displayed higher BET surface area (21.06 m2/g), lattice strain (0.0157), smaller ionic radius (58.2 pm) and higher relative surface oxygen ratio (58%) and thus resulted in a significantly better soot oxidation activity (T50 = 483 °C) than compared to other non-redox metal oxides. Graphical Abstract: [Figure not available: see fulltext.]. © 2017, Springer Science+Business Media, LLC.Item Surface morphology and phase stability effect of Ceria-Hafnia (CHx) binary metal oxides on soot oxidation activity(Elsevier B.V., 2018) Anjana, A.P.; Prasad Dasari, H.P.; Harshini, H.; Babu, G.U.B.CeO2-HfO2 (CHx) binary metal oxides over whole composition range (0–100%) are synthesised using the EDTA-Citrate method and calcined at 600 °C/5 h. From XRD analysis, the sample series are classified as fluorite (F) phase for CH10-CH30, hybrid (F + M) phase for CH40-CH90 and monoclinic (M) phase for CH100 sample, respectively and the results were further confirmed using Raman spectroscopy. From SEM analysis, a clear surface morphology change is noticed for fluorite, hybrid and monoclinic phases of the CHx binary metal oxides. Further, Selected Area Electron Diffraction (SAED) analysis also confirmed the single and hybrid phases of CHx binary metal oxides. The soot oxidation for the CHx binary metal oxides displayed high catalytic activity for Fluorite phase (CH10 ? CH30) samples and a decrease in catalytic activity is noticed for the Hybrid phase (CH40 ? CH90) samples. The change in catalytic activity coincides with the change in the surface morphology and phase change for the CHx binary metal oxides. Among the Fluorite phase samples, CH10 sample displayed the highest catalytic activity (T50 = 430 °C) with higher surface area (29 m2/g), lower particle size (26 nm), lower degree of agglomeration (? = 2.8) higher surface oxygen concentration (44%). Isothermal-Time-on-stream (ITOS) analysis also showed that the CH10 sample can achieve T50 in a shorter time than compared to other CHx binary metal oxides. Surface morphology and phase stability can also play as key descriptors in screening CHx binary metal oxides for soot oxidation activity. © 2018 Elsevier B.V.