Department of Physics

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Author: search.filters.author.Dr. Muhammad Ashfaq AhmadSubject: search.filters.subject.FA20

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    Study of Structural, Thermoelectric and Electrochemical Analysis of LaSrCoFeO Cathode Materials Prepared by Different Methods
    (Library Information Services, COMSATS University Islamabad, Lahore Campus, 2022) Khadija Imdad; CIIT/FA20-RPH-044/LHR; Dr. Muhammad Ashfaq Ahmad; LHR TP 8000
    World is moving towards renewable energy sources to avoid carbon dioxide emission causing global warming and climate change. Solid oxide fuel cells SOFCs are one of the best alternatives for energy production due to its maximum energy conversion and zero/low emission. To use biogas as a clean and high energy conversion, SOFC is the good option. However, there are still some complications that need to be addressed; one of the significant challenges, activity of SOFC at low temperature is decreased because of interfacial polarization obstructions and also oxygen reduction reaction (ORR). Thus, to improve the activity and ORR, Lanthanum based perovskite structured cathode materials were synthesized. The proposed materials were Lanthanum Strontium Cobalt Ferric oxide (La1−xSrxCo1−yFeyO3–δ (LSCF)), where x=0.3 and y=0.7. Samples were prepared by different methods such as: sol-gel method, co-precipitation method, solid state reaction method and ball milling method. The structural properties were analyzed through Raman, FTIR and XRD.UV visible analysis were also implemented to check the direct and indirect band gap of La0.7Sr0.3Co0.3Fe0.7O3-δ prepared by different methods. Electrical Impendence Spectroscopy was uses to check the conductivities of the prepared samples at different temperatures. Results revealed the Rhombohedral Structure of LSCF belongs to the R3c space group. FTIR Spectra shows the absorption peaks at 650cm-1, 656cm-1, 657cm-1, is due to the stretching vibration of Co-O/Fe-O in LSCF perovskite structure. The maximum conductivity was obtained 0.08 S/cm at intermediate temperature of LSCF which was prepared by Co Precipitation Method. This suggests that resistance lowers as temperature rises, leading to an increase in conductivity and ORR as well. La0.7Sr0.3Co0.3Fe0.7O3- δ, which was made using the co-precipitation method, has a direct band gap of 2.51 eV. This sample has the lowest band gap of all the samples made using various methods. AC conductivity is measured by four-point probe spectroscopy for the LSCF cathodes. The data obtained from four-point probe spectroscopy electrical conductivity for all prepared cathode sample is calculated At Intermediate temperature (500°C) material with different methods such as sol-gel, co- precipitation, solid state reaction and ball milling give maximum conductivity such as 0.049,0.0889,0.0250 and 0.0159 respectively. The La0.7Sr0.3Co0.7Fe0.7O3–δ has maximum conductivity of 0.0889 Scm -1 at 500 °C prepared by co-precipitation method. The maximum value of OCV and current for the prepared pallets are 0.53V and 0.011A respectively. Whereas the maximum value of current density and power density is 17.18mA/cm2 and 2.88mW/cm2 respectively at 600℃.
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    Study of Quantum Effects and Porosity of the Perovskite Materials for Energy and Photocatalysis Applications
    (Library Information Services, COMSATS University Islamabad, Lahore Campus, 2022) Asifa Kusar; CIIT/FA20-RPH-007/LHR; Dr. Muhammad Ashfaq Ahmad; LHR TP 7972
    Energy conversion devices are widely being used to convert chemical into electrical. Fuel cell is the most prominent candidate among all the energy conversion devices. The operating temperature of conventional fuel cell is very high because of high electrolyte resistance. Develop better energy storage and conversion devices is the main goal of the scientists and engineers because of increasing global temperature due to consumption of fossil fuels. Fuel cell has potential and capability to give maximum energy without deteriorating environment. Electrode is the most important component of fuel cell because reaction takes place on it. Lanthanum and ferrite-based perovskite material are investigated quantum mechanically to find out the impact factor on working of SOFCs. Among the prepared samples the material with high concentration shows batter crystal structure, photocatalytic activity and improved conductivity. Samples have been investigated by various techniques showing considerable porosity, stability and Prescence of reactive metal cations like La+2, Sr+1, Cu+1 , Fe+2 and Fe+3 reveal the improved functionality of perovskites as they assist in conductivity, oxidation, reduction and catalytic process. Crystalline structure of the material is determined by XRD, energy band gap can be found by UV-Vis, vibrational characteristics and phase shift of the synthesized material can be found by Raman spectroscopy, materials used in synthesis can be confirmed by FTIR. Among various types of perovskites, the LSF perovskites are best performing material for photocatalytic applications while study of quantum effects reveals that LSCF second to them LCF are best optimized material for energy applications.