Faculty Publications
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Item Fabrication of praseodymium-doped ceria (PDC) films by slurry spin-coating technique and its structural, morphological and optical properties(Elsevier B.V., 2023) Ravindra, M.M.; Shirasangi, R.; Prasad Dasari, H.P.; Saidutta, M.B.The current study is on the fabrication of PDC films prepared by slurry spin-coating technique for photoluminescence activity. At lower spin rates (1000 rpm), thicker and uniform PDC films were obtained. The structural evolution of the sintered PDC films on a dense alumina substrate was studied using Grazing Incidence X-ray diffraction (GIXRD) and Raman Spectroscopy. Crystallite size, microstrain, and dislocation density values remain almost the same with the increase in the coating cycles. The A568/A463 ratio for 3, 5, and 10 coating cycles are 0.52, 0.49, and 0.61, respectively. Surface roughness studies of PDC films using a 3D Noncontact Profilometer. The mean surface roughness values are 12.55, 13.74, and 22.25 μm for the 3rd,5th, and 10th coating cycles, respectively. Microstructure observation by Field Emission Scanning Electron Microscope (FE-SEM). The average thickness of the films for the 3rd, 5th, and 10th coating cycles are 50.93, 41.64, and 109.95 μm, respectively. The PDC films obtained on a dense alumina substrate were porous. FE-SEM micrographs showed a particle aggregation of several irregular and smaller grains, indicating the sintering activity of PDC films. Optical properties were studied using ultraviolet-visible (UV–Vis) absorption spectra and photoluminescence spectra (PLS). The band gap values slightly increased with the increase in the coating cycles. A decrease in PL intensity with an increase in the coating cycle is related to higher oxygen vacancy concentration. PDC films fabricated by the slurry spin-coating technique can be successfully used for optoelectronic applications. © 2023Item 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 Current-Voltage (i-V) characteristics of electrolyte-supported (NiO-YSZ/NiO-SDC/ScSZ/LSCF-GDC/LSCF) solid oxide electrolysis cell during CO2/H2O co-electrolysis(Elsevier B.V., 2024) Shirasangi, R.; Lakhanlal, u.; Prasad Dasari, H.P.; Saidutta, M.B.Solid oxide electrolysis cells (SOECs) stabilize CO2 emissions by converting CO2/H2O into synfuel. Current-Voltage (i-V) characteristics of an electrolyte-supported button cell (NiO-YSZ/NiO-SDC/ScSZ/LSCF-GDC/LSCF) were measured as a function of temperature, water vapor concentration, and CO2 gas concentrations. The cell microstructure was characterized by the Field Emission Scanning Electron Microscope (FE-SEM). FE-SEM micrographs depict that the electrolyte layer is relatively dense, and porous fuel and air electrode layers are well adhered to the electrolyte. The i-V curves were obtained at a scan rate of 0.02 Vs?1 from 0.3 to 1.5 V. Electrolysis current density increases as the temperature increases. SOEC performance increases, but SOFC performance decreases with increased water vapor concentration. Electrolysis current densities decrease as the CO2 concentration increases. The i-V characteristics show only ohmic polarization under fuel-lean and fuel-rich conditions. At optimal conditions, current density values at 800 °C/1.5 V are -174, -187, and -195 mA cm?2 for 5 %H2O, 30 %CO2, and 30 %CO2/5 %H2O co-electrolysis. At 800 °C, open-circuit voltage (OCV) values for H2O, CO2, and co-electrolysis are 0.906, 0.891, and 0.885 V, respectively. The electrolysis area-specific resistances (ASRs) give information on the reduction of CO2 or H2O, forming CO or H2, respectively. At optimal conditions, ASR values are 3.43, 3.29, and 3.18 ? cm2 for H2O, CO2, and co-electrolysis, respectively. Co-electrolysis has a lower ASR value than pure H2O and CO2 electrolysis, indicating that H2O and CO2 are involved in the electrochemical processes. © 2024 The Author(s)Item Study of CO oxidation activity of NiO-PDC and NiO-YSZ catalysts coated on alumina wash-coated honeycomb cordierite monolith(Springer Science and Business Media Deutschland GmbH, 2025) Wagay, A.A.; Shourya, A.; Patil, S.S.; Shirasangi, R.; Prasad Dasari, H.P.In this study, the EDTA-Citrate method was employed to synthesize NiO-PDC (NPC) and NiO-YSZ (NYZ) powder catalysts in nanostructured form. Subsequently, the catalysts were slurry dip-coated onto monolith cordierite substrates with alumina, using a one-step coating approach, and their CO oxidation activity was tested. The coating was achieved by first mixing the catalyst with the alumina suspension to prepare a homogeneous slurry, which was then used for dip coating onto the monolith. The adherence test was performed on the coated monolith to evaluate the mechanical stability of the catalyst-alumina composite layer. The coating was visually confirmed through optical imaging. The remaining powders (after coating) were then subjected to BET surface area, XRD, Raman spectroscopy, H2 TPR and O2 TPD analysis for characterization. Raman spectra showed that NPC exhibited higher oxygen vacancies than NYZ. H2 TPR and O2 TPD provided better evidence of the reduction potential and O2 desorption of NPC respectively. NPC/cord demonstrated the highest catalytic activity (T50 = 165 °C) compared to NYZ/cord (T50 = 215 °C) and bare cordierite (T50 = 777 °C), which is attributed to its better redox properties and higher oxygen vacancies. The effect of flow rate and heating rate on CO oxidation was studied on NPC/cord and NYZ/cord. The long-term stability of the NPC/cord and NYZ/cord were tested through 5-h and 50-h isothermal studies. © The Author(s) under exclusive licence to Associação Brasileira de Engenharia Química 2025.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)Item CO2 concentration effects on CO2/H2O co-electrolysis in a solid oxide electrolysis button cell(Springer Science and Business Media Deutschland GmbH, 2025) Shirasangi, R.; Prasad Dasari, H.P.; Saidutta, M.B.Abstract: The influence of CO2 gas concentration on the co-electrolysis performance of an electrolyte-supported button cell (NiO-YSZ/NiO-SDC/ScSZ/LSCF-GDC/LSCF) was investigated. At 800 oC/1.5V, the interfacial polarization resistance (Rp) values for 10%CO2/15%H2O and 30%CO2/15%H2O are 7.19 and 26.91 ?.cm2, respectively. CO2 gas concentration significantly affects the Rp value. Gas diffusion resistance is dominant in the overall polarization resistance. As the CO2 concentration increases (10%?30%), H2 consumption increases, indicating RWGS dominance. For 30% CO2/15% H2O, CO2 out is slightly more than the input value due to the WGS and Boudouard reactions. As the applied voltage value increases from OCV, the H2 residue increases. H2O and CO2 co-electrolysis occurs at 1.5 V. The post-test XRD and Raman spectra results show NiO reduction and metallic Ni appearance. The post-test FE-SEM micrographs show no delamination at the air electrode/electrolyte interface, and carbon deposition is observed in the composite fuel electrode layer. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.Item Degradation studies over nickel foam current collector for supercapacitor application(Springer Science and Business Media B.V., 2025) Chakarayan, T.; Pallipad, A.; Shirasangi, R.; Purushothaman, P.; Prasad Dasari, H.P.The 3D porous structure of nickel foam makes it appealing as a current collector in supercapacitors. Cyclic voltammetry (CV) studies were conducted in a three-electrode cell with a 1.2 cm diameter Ni foam (working electrode), an Ag/AgCl (reference electrode), and a Pt (counter electrode) in KOH electrolyte solution. The effects of various scan rates, different concentrations of KOH, and degradation tests were evaluated. Characterization of Ni foam after cyclic study was carried out using X-Ray Diffraction (XRD), Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), and Field emission scanning electron microscopy (FESEM). The areal capacitance decreased from 341.71 to 196.83 mF cm? 2 with an increase in scan rate from 5 to 30 mV s? 1 for 1 M KOH. The increase in the redox peak currents is of order: 5 M > 3 M > 1 M > 7 M. From the XRD results, the Ni peak intensity decreased as the KOH concentration increased due to the formation of the oxide layer (NiOOH) following CV analysis. Bare Ni foam exhibited no peaks in the Raman spectra. However, the Ni foam after CV in 1, 3, 5, and 7 M KOH showed peaks around ~ 500–600 cm? 1 and ~ 1000 cm? 1, indicating the stretching vibrations of Ni-O and Ni-OH bonds, respectively. The peaks ~ 2800 cm? 1 indicate O-H stretching. From the FTIR spectra, the broad and weak peaks around ~ 3000–3750 cm? 1 for Ni foam after CV indicated O-H stretching, while peaks around ~ 1500–1650 cm? 1 and ~ 1100 cm? 1 represented hydroxyl and Ni-OH bending, respectively. Significant degradation was observed within the first 100 cycles. On the surface of the Ni foam, nanoflake structures were observed following the electrochemical measurements, indicating the presence of an oxide layer. This was confirmed by Energy Dispersive X-ray Spectroscopy (EDX) analysis, which revealed that the oxygen element’s weight%, along with potassium and carbon on the surface of Ni foam, increased with increasing KOH concentration. The maximum areal capacitance of 1628.44 mF cm? 2 at 5 mV s? 1 was obtained with 5 M KOH among the different electrolyte concentrations. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.