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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 Ceria-samarium binary metal oxides: A comparative approach towards structural properties and soot oxidation activity(Elsevier B.V., 2018) Anjana, A.P.; Geethu, J.; P, M.R.; Prasad Dasari, H.P.; Lee, J.-H.; Harshini, H.; Bhaskar Babu, G.U.Binary metal oxides of CeO2-Sm2O3 (CSx, x varies from 10 to 90 mol%) along with pure CeO2 and Sm2O3 were synthesised successfully by the EDTA-Citrate method. From XRD, Raman spectroscopy and UV–vis DRS results, the whole composition of metal oxides exist in three phases: (fluorite phase (F) (CS10-CS30), bi-phase (fluorite (F) + cubic (C)) (CS30-CS90) and cubic phase (C) (Sm2O3)). For CSx samples, the calculated band gap energy values obtained from the UV–vis DRS results were in between 3.0–5.1 eV and fluorite phase samples (CS10–CS30) displayed lower band gap energy values (3.04–3.07 eV) than compared to the samples in other phases. Similarly, from XPS analysis, fluorite phase samples (CS10–CS30) showed higher surface oxygen vacancy concentration than compared to samples in other phases. Catalytic activity for soot oxidation is carried out on CSx samples, and the T50 temperature is in between 480–540 °C. Fluorite phase samples (CS10 CS30) showed higher surface area, lower degree of agglomeration, lower band gap energy, higher oxygen vacancy concentration and better catalytic activity for soot oxidation. Among all the CSx samples, CS10 sample displayed highest surface area (38 m2/g), lowest degree of agglomeration (0.36), lowest band gap energy (3.04 eV), highest oxygen vacancy concentration (64%) and highest soot oxidation activity (T50 = 480 °C). The order of the soot oxidation activity of CSx samples followed the same trend of band gap energy values. © 2018 Elsevier B.V.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.Item Effect of Nd-doping on soot oxidation activity of Ceria-based nanoparticles synthesized by Glycine Nitrate Process(Elsevier B.V., 2019) Patil, S.S.; Prasad Dasari, H.P.; Harshini, H.Neodymium-doped Ceria (NDC, Nd = 0, 1, 3, 5, 10, 20 and 30 mol %) catalysts were successfully synthesized by Glycine-Nitrate-Process (GNP) and tested for soot oxidation activity. For all NDC catalysts, XRD and Raman spectroscopy analyses showed a fluorite structure of ceria having an F2gRaman active symmetric breathing mode (O-Ce-O). 1NDC catalyst displayed better T50 temperature (427?C) followed by 0NDC (435?C), and 30NDC showed the highest T50 temperature (460?C). From XPS analysis, 1NDC and 0NDC catalysts showed a high amount of Ce3+ concentration and the surface-active oxygen species than compared to other NDC catalysts and thus, resulted in better soot oxidation activity indicating that the surface Ce3+ concentration and surface-active oxygen species play a key descriptor role in tuning the soot oxidation activity of NDC catalysts. © 2019 Elsevier B.V.Item Studies on the Solid Oxide Cell Perovskite Electrode Materials for Soot Oxidation Activity(Springer, 2019) Shenoy, C.S.; Patil, S.S.; Govardhan, P.; Shourya, A.; Prasad Dasari, H.P.; Saidutta, M.B.; Harshini, H.Solid oxide cell (SOC) perovskite electrode materials (BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-?), LSCF (La0.6Sr0.4Co0.2Fe0.8O3-?) and LSCM (La0.75Sr0.25Cr0.5Mn0.5O3-?)) were synthesised using microwave-assisted reverse-strike co-precipitation method and tested for soot oxidation activity. The calcined perovskite materials were characterized using FT-IR, XRD, SEM and BSE, BET and BJH and XPS analysis. The mean activation energy for soot oxidation was calculated from Ozawa plots at various heating rates (5, 10, 15 and 20 K/min) at different levels of soot conversions (T10 to T90) for BSCF, LSCM and LSCF perovskite materials and was around 133 ± 11.5, 138 ± 9.9 and 152 ± 7.2 kJ/mol, respectively. Irrespective of the heating rates, BSCF material showed the lowest T50 temperature than compared to other samples, and it is correlated to the presence of Fe3O4 as a secondary phase. © 2019, Springer Nature Switzerland AG.Item Effect of fuel and solvent on soot oxidation activity of ceria nanoparticles synthesized by solution combustion method(KeAi Communications Co., 2019) Patil, S.S.; Prasad Dasari, H.P.Effect of fuel (glycine and urea) and solvent (water, acetone and ethanol) on the soot oxidation activity of ceria nanoparticles synthesized by solution combustion method is carried out in the present study. X-ray diffraction (XRD) patterns displayed a fluorite structure and the Tauc's plot obtained from UV-Diffusive Reflectance spectroscopy (UV-DRS) showed that the band gap value was around 2.9–3.1 eV for the synthesized ceria nanoparticles irrespective of the fuel and solvent used. Ceria nanoparticles synthesized using glycine and acetone resulted in lower crystallite size, higher facet ratios ([1 0 0]/[1 1 1] and [1 1 0]/[1 1 1]) and higher lattice strain than compared to other solvents and fuels and thus resulted in better soot oxidation activity (T50 = 416 °C). The present synthesis method has played a significant role in improving the reactive facet ratios, providing lower crystallite size and high lattice strain. © 2019Item Printex-U soot oxidation kinetic behaviour over Alumina and Quartz(Elsevier Ltd, 2022) Ganiger, S.; Patil, S.S.; Prasad Dasari, H.P.; Priyanka, R.; Kollimarla, S.Printex-U carbon (Pure Soot, S0) on alumina (SA) and quartz (SQ) powder were considered to understand the behaviour of oxidation reaction and kinetic analysis. A similar model of the single-step reaction was followed by the Soot (S0) and SA sample, while SQ followed a complex mechanism of multiple-step reactions. From the experimental and theoretical calculations, it was observed that there was a slight decrease in the T50 temperature for SA, which also had the lowest Ea, but there was an increase in T50 and Ea for SQ compared to the S0 sample. From the present study, it can be understood that the alumina enhanced the catalytic activity when compared to pure soot alone, whereas quartz inhibited the activity. The T50 temperature, Ea, and A calculated were obtained in SA < S0 < SQ. The soot properties and their kinetics will further help to design catalyzed diesel particulate filters. © 2021 Elsevier LtdItem A Negative Effect of Niobium-Doped Ceria on Soot Oxidation Activity‡(John Wiley and Sons Inc, 2022) Patil, S.S.; Naik, S.; Ramesh, M.D.; Harshini, H.; Prasad Dasari, H.P.Niobium-doped ceria catalysts were synthesized to study soot oxidation activity. X-Ray diffraction (XRD) and Raman analysis of the samples revealed the presence of a fluorite structure of CeO2 for all the doped samples. The T50 temperature of the pure CeO2 sample was more significant than that of bare soot. The high catalytic activity of the CeO2 catalyst can be attributed to the low crystallite size, high facet ratio, and the large Brunauer-Emmett-Teller (BET) surface area as compared to Nb-doped samples. The activation energy calculated by both Ozawa and KAS methods were found to be low for CeO2 when compared to Nb-doped samples. CeO2 resulted in better soot oxidation activity with low activation energy. © 2022 Wiley-VCH GmbHItem Manganese doped Ceria (Ce1−xMnxO2−δ (x = 0–0.3)) catalysts synthesized by EDTA–Citrate method for soot oxidation activity(Springer Science and Business Media Deutschland GmbH, 2022) Shourya, A.; Prasad Dasari, H.P.Ceria–Manganese oxide catalysts (Ce1−xMnxO2−δ where x = 0, 0.05, 0.1, 0.2, and 0.3, termed CM0, CM5, CM10, CM20, and CM30, respectively) were synthesized by EDTA–Citrate method, calcined at 600 °C/5 h, and checked for soot oxidation activity. The XRD spectra exhibited the cubic fluorite phase formation and complete solubility of Mn in Ceria lattice up to CM30. BET and BJH analysis showed that the surface area and pore volume had an appreciable influence on the soot oxidation activity, as seen in the case of CM5, which had superior BET surface area (50 m2/g) as well as pore volume (0.128 cc/g). The Raman spectra revealed secondary phase formation of Mn3O4 peak in CM20 and CM30. FESEM analysis was carried out for all the CMX samples. TEM images displayed the decrease in the particle size of CM5 with the inclusion of Manganese ions into the Ceria lattice. SAED analysis provided evidence for the polycrystalline nature of CM5 compared to CM0. Soot oxidation activity was carried out in tight contact conditions and an air atmosphere. CM5 with a T50 of 360 °C had the least among the CMX catalysts. Ozawa and KAS methods were used to determine the soot oxidation activation energy. CM5 had the least activation energy with 118 kJ/mol (Ozawa) and 114 kJ/mol (KAS). High specific surface area, pore-volume, relatively higher exposed (220) and (200) planes, the lower activation energy for soot oxidation activity, high synergy, and robust interactions between Ceria and Manganese oxides were pivotal in the decrease in soot combustion temperature of the CM5 catalyst. Graphical abstract: [Figure not available: see fulltext.] © 2022, Institute of Chemistry, Slovak Academy of Sciences.Item Formation of nano-rod structures in manganese-rich ceria–manganese mixed oxides and their soot oxidation activity(Elsevier B.V., 2023) Shourya, A.; Prasad Dasari, H.P.EDTA-citrate synthesized manganese-rich ceria–manganese oxide catalysts (Ce1−xMnxO2−δ; where x = 1 to 0.6, termed CM100, CM90, CM80, CM70, CM60, CM50 and CM40 respectively) were obtained after calcination at 600 °C/5 h, characterized and tested for soot oxidation activity. Mn3O4 and Mn2O3 phases were observed in the XRD spectra; with the increase in the ceria concentration, cubic fluorite phase formation was observed from CM80 to CM40. BET and BJH analyses revealed that the pore diameter and volume had a meaningful impact on the soot oxidation activity, as seen for CM80 which had a BET surface area of 31 m2/g, pore diameter of 21.119 nm, and a pore volume of 0.1637 cc/g. The formation of the Mn3O4 peak in all the synthesized catalysts and ceria's cubic fluorite F2g peak (452 cm −1) were observed from CM80 to CM40 from Raman spectral analysis. FESEM analysis of all the CMX samples revealed an intriguing aspect, the appearance of nano-rods. These nano-rods were observed in the HRTEM imaging as well. The high-resolution imaging and SAED analysis proved that the nano-rod structures were primarily due to the α-MnO 2 phase. The mixture of agglomerates and nano-rods profoundly affected the soot oxidation activity of the synthesized samples. CM70 had a minimum T50 of 389 °C among the CMX catalysts. The activation energy was reckoned with the Ozawa and KAS methods. CM50, with 131 kJ/mol for Ozawa and 127 kJ/mol for the KAS method, had the lowest values among the chosen catalysts. Synergistic interactions between ceria and the manganese oxides, considerable specific surface area, pore diameter, pore volume, substantially higher exposed (220) and (200) planes and the formation of the nano-rods helped to lower the activation energy for soot oxidation activity and consequently a reduction in the soot oxidation temperature of CM50 to CM70. The concentration of the nano-rods rendered a considerable role in reducing the T50 temperatures of the CMX catalysts. © 2023 Elsevier B.V.