Faculty Publications
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Item 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 The catalytic effect of chromium-doped ceria-praseodymium on soot oxidation activity and its kinetics(Springer, 2024) Patil, S.S.; Prasad Dasari, H.P.Soot generated from the partial combustion of diesel significantly contributes to air pollution, and catalytic oxidation is currently an effective method for removing diesel soot particles. The chromium-doped ceria-praseodymium (Cr-CP) catalyst system is synthesized via solution combustion synthesis and evaluated for soot oxidation activity, with a subsequent kinetics study conducted. The XRD analysis of the catalysts indicated a decrease in crystallite size and increased lattice strain and reactive facet ratios for all Cr-doped CP samples. Raman analysis verified the existence of oxygen vacancy peaks in all chromium-doped CP catalysts. X-ray photoelectron spectroscopy (XPS) revealed the presence of adsorbed H2O or molecular water peaks in the O1s spectra for the 5 Cr-CP catalyst, which also exhibited a high concentration of surface Cr3+ ions. Thermogravimetric analysis (TGA) of soot oxidation indicated that 5 Cr-CP exhibited a superior T50 of 393 ± 2 °C, mostly attributed to the presence of reducible surface Cr3+ ion species. Kinetic analysis was performed on all Cr-doped CP catalysts to assess the kinetic triplets: activation energy, pre-exponential factor, and reaction model. The activation energy was low (87 kJ mol−1, Ozawa method) for 15 Cr-CP, while the pre-exponential factor was higher for 5 Cr-CP (7.39 × 1010 min−1). The Cr-CP catalyst system adhered to a power law, indicating a phase boundary-controlled reaction characterized by nucleation and growth mechanisms. The consistency between experimental and calculated curves confirmed that the developed catalysts adhered to the Avrami-Erofeev equation (Am) or the nucleation and growth model. Graphical Abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.Item Electrochemical characterization of electrolyte supported solid oxide electrolysis cell during CO2/H2O co-electrolysis(Springer Science and Business Media Deutschland GmbH, 2024) Shirasangi, R.; Prasad Dasari, H.P.; Saidutta, M.B.High-temperature co-electrolysis is studied on electrolyte-supported NiO-YSZ/NiO-SDC/ScSZ/LSCF-GDC/LSCF (NiO: Nickel Oxide, YSZ: Yttria-stabilized zirconia, SDC: Samarium-doped ceria, ScSZ: Scandia-stabilized zirconia, LSCF: Lanthanum Strontium Cobalt Ferrite, GDC: Gadolinium-doped ceria) button cell. Electrochemical impedance spectroscopy (EIS) was recorded under open-circuit voltage (OCV) and co-electrolysis mode over various operating conditions, including temperature, water vapor content, and applied voltage. Interfacial polarization resistance (Rp) is obtained from peak arcs located in the three regions: gas conversion resistance (Region I (0.01 to 0.1 Hz)), gas diffusion resistance (Region II (0.1 to 100 Hz)) and air electrode charge transfer resistance (Region III (100 to 10,000 Hz)). As the temperature increased from 700 to 850 oC, Rp decreased from 18.15 to 3.32 Ω.cm2 at 1.3 V for 10%CO2/3%H2O. From the Distribution of relaxation times (DRT) studies, one additional peak, P5 (fuel gas conversion or gas-phase diffusion in the pores of the air electrode), is observed, and Region III (100 to 10,000 Hz) consists of two additional peaks: P1 (ionic transport coupled with gas diffusion close to triple phase boundaries (TPBs)) and P2 (fuel electrode charge transfer reaction), which were not clearly distinguished from EIS. Region II dominates in the overall polarization resistance. At 800 oC, for 10%CO2/3%H2O, the Rp decreased from 6.78 to 4.82 Ω.cm2, with an increase in the applied voltage from 1.3 to 1.5 V. At 800oC/1.5 V, the Rp values are 4.41, 8.09, and 6.77 Ω.cm2 for H2O, CO2, and co-electrolysis. At 800 ºC/1.5 V, with an increase in the water vapor content from 3%H2O to 15%H2O, there is not much change in the Rp value; therefore, 10%H2O is sufficient. H2 consumption is between 23 and 36%, depending on the temperature at OCV. At 800 °C for (10%H2/10%CO2/10%H2O), co-electrolysis occurs at applied voltage, along with Reverse water gas shift (RWGS) reaction. Graphical Abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.Item Diesel soot oxidation over Mn–Pr–Ce oxide catalysts: structural changes and the impact of Mn doping(Royal Society of Chemistry, 2025) Patil, S.S.; Prasad Dasari, H.P.; Shirasangi, R.; Harshini, H.The soot oxidation activity of manganese-doped ceria-praseodymium catalysts, synthesized via solution combustion synthesis, was evaluated. The analyses performed with XRD and Raman spectroscopy indicated that the Mn-doped CP catalysts displayed the typical fluorite structure of CeO2. The addition of Mn to CP led to a reduction in crystallite size from 14 nm to below 10 nm. The F2g Raman active mode of fluorite-structured Ce and the oxygen vacancies resulting from the addition of Mn and Pr (bands B 560 cm–1 to 580 cm–1) were consistently observed across all Mn-doped CP catalysts. 15 and 20 Mn-CP exhibited an additional secondary phase identified as Mn2O3. The analysis of BET surface area and BJH pore size revealed that the Mn-doped CP catalysts exhibited both micro and mesoporous characteristics. The H2-TPR and O2-TPD profiles indicated enhanced reducibility resulting from the incorporation of Mn and Pr into CeO2-doped catalysts. The improved T50 (365 ± 1 1C) for the 5 Mn-CP catalytic system is primarily due to its increased specific surface area of 45 m2 g–1 and the presence of active surface adsorbed oxygen species identified in the XPS and O2-TPD studies. 5 Mn-CP exhibited the lowest activation energy value compared to all other Mn-doped catalysts. © 2025 The Author(s)