Browsing by Author "Singh, Kalpana"

Now showing 1 - 7 of 7
  • Thumbnail Image
    ItemOpen Access
    Chemically Stable Proton Conducting Doped BaCeO3 -No More Fear to SOFC Wastes
    (Springer Science and Business Media LLC, 2013-07-04) Kannan, Ramaiyan; Singh, Kalpana; Gill, Sukhdeep; Fürstenhaupt, Tobias; Thangadurai, Venkataraman
    Development of chemically stable proton conductors for solid oxide fuel cells (SOFCs) will solve several issues, including cost associated with expensive inter-connectors and long-term durability. Best known Y-doped BaCeO3 (YBC) proton conductors-based SOFCs suffer from chemical stability under SOFC by-products including CO2 and H2O. Here, for the first time, we report novel perovskite-type Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3?? by substituting Sr for Ba and co-substituting Gd + Zr for Ce in YBC that showed excellent chemical stability under SOFC by-products (e.g., CO2 and H2O) and retained a high proton conductivity, key properties which were lacking since the discovery of YBCs. In situ and ex- situ powder X-ray diffraction and thermo-gravimetric analysis demonstrate superior structural stability of investigated perovskite under SOFC by-products. The electrical measurements reveal pure proton conductivity, as confirmed by an open circuit potential of 1.15?V for H2-air cell at 700°C and merits as electrolyte for H-SOFCs.
  • Thumbnail Image
    ItemOpen Access
    Electrochemical Studies of Gd0.5Pr0.5BaCo2O5+δ (GPBC) Cathode for Oxide Ion and Proton Conducting Solid Oxide Fuel Cells
    (Elsevier, 2016) Singh, Kalpana; Baral, Ashok K.; Thangadurai, Venkataraman
  • Thumbnail Image
    ItemOpen Access
  • Thumbnail Image
    ItemOpen Access
    High Performance Tubular Solid Oxide Fuel Cell Based on Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-? Proton Conducting Electrolyte
    (The Electrochemical Society, 2018-07-07) Amiri, Taghi; Singh, Kalpana; Sandhu, Navjot Kaur; Hanifi, Amir Reza; Etsell, Thomas H.; Luo, Jing-Li; Thangadurai, Venkataraman; Sarkar, Partha
    In this work, synthesis and characterization of an anode supported tubular solid oxide fuel cell based on Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-? (BSCZGY) electrolyte has been investigated. Anode-supported Ni - yttria-stabilized zirconia (YSZ) anode was fabricated via slip casting; BSCZGY electrolyte and BSCZGY - La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) composite cathode were coated on support using dip coating, respectively. The chemical compatibility of fuel cell components at sintering temperatures has been investigated by powder X-ray diffraction, and no severe reactions were detected. Electrochemical examination under air/H2 + 3 vol. % H2O showed superior performance achieving a maximum power density of 1 W/cm2 at 850°C, among the best compared to tubular – geometry oxygen conductor solid oxide fuel cells reported earlier and one of the highest reported for a proton conductor electrolyte in literature. Electrochemical impedance spectroscopy was used to examine the electrochemical performance of the full cell at different temperatures, and a detailed analysis was done to distinguish the contribution of ohmic and polarization resistances of the cell. ASR values were 3.47 ?.cm2, 1.81 ?.cm2, 1.23 ?.cm2, and 1.05 ?.cm2 at 600, 700, 800, and 850°C, respectively. Analysis of activation energy associated with charge and mass transfer based on fitting of impedances revealed that concentration polarization is the major contributor to the total resistance. The long-term stability for more than 96 hours of operation under load showed no significant degradation, which demonstrated the steady behavior of the cell.
  • Thumbnail Image
    ItemOpen Access
    Ni-Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-Delta Anode Composites for Proton Conducting Solid Oxide Fuel Cells (H-SOFCs)
    (Canadian Center of Science and Education, 2016-09-01) Singh, Kalpana; Baral, Ashok Kumar; Thangadurai, Venkataraman
    In this paper, we report the electrochemical properties of Ni-Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-Delta (BSCZGY) anode composites in 3% H2O-H2 for proton conducting solid oxide fuel cells (H-SOFCs). Ni-BSCZGY composites with volume ratio of 30:70, 40:60, and 50:50 were synthesised through mechanical mixing and combustion methods. In combustion method, auto-ignition step led to brown coloured ash, which was calcined at 1000 oC for 5 h to form NiO-BSCZGY powder. Screen-printing, co-firing and reduction process were used to prepare the symmetrical cell: Ni-BSCZGY/BSCZGY/Ni-BSCZGY. Ni50-BSCZGY anode exhibited the lowest polarisation resistance (Rp) of 0.8 Omega.cm2 and 1.9 Omega.cm2 at 710 oC under 3% H2O-H2, for both mechanically mixed and combustion methods, respectively.
  • Thumbnail Image
    ItemOpen Access
  • Thumbnail Image
    ItemOpen Access
    Tailoring Perovskite- and Fluorite-Type Oxides for Solid Oxide Fuel Cells (SOFCs)
    (2016) Singh, Kalpana; Thangadurai, Venkataraman; Birss, Viola; Shimizu, George; Cheng, Frank; Kesler, Olivera
    A solid oxide fuel cell (SOFC) is a high temperature solid state energy conversion device that directly converts the chemical energy of fuels into electrical energy at high efficiency. The objective of thesis is to develop and tune fluorite- and perovskite-type metal oxides that serve as alternate anodes, electrolytes, and cathodes for intermediate temperature SOFCs. Here, the chemical reactivity between a fluorite-based Ce0.7RE0.2Mo0.1O2 (RE = Y, Sm) anode and 8 mol% yttria-stabilized zirconia electrolyte was evaluated at 1000 ºC. The electrical conductivity of the reaction product Ce1-x-y-zRExZrYMozO2 in air and wet H2 was found to be lower than that of Ce0.7RE0.2Mo0.1O2, due to the formation of defect associates and a decrease in concentration of charge carriers. The effect of A-and B-site co-doping on the chemical and electrical properties of potential perovskite-type Ba0.5Sr0.5Ce1-x-y-zZrxGdyYzO3-δ (0 < x < 0.5; y = 0, 0.1, 0.15; z = 0.1, 0.2) proton conducting electrolyte was evaluated. Excellent chemical stability under water vapor for 24 h at 90 ºC was observed for all compositions. The electrical conductivity measurements under dry and humid atmospheres revealed the proton conductivity in these oxides. Among the samples investigated, Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ showed the highest proton conductivity of 10-3 S/cm at 600 ºC in humid air and H2. The effect of sintering temperature on the proton dynamics of Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ was evaluated by establishing a correlation between the grain boundary space charge effect, electrical conductivity, and dielectric loss of the samples sintered at 1300, 1400, and 1550 ºC. The proton dynamics in local motion and long-range motion appears to be different due to the difference seen in the relaxation time and activation energy of protons in local motion and bulk conduction properties. Furthermore, the electrochemical performance of the layered perovskite-type Gd0.5Pr0.5BaCo2O5+δ and Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ composite cathode, and Ni and Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ composite anode for proton conducting SOFCs was evaluated through symmetrical cell studies. The symmetrical cell of Gd0.5Pr0.5BaCo2O5+δ-Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3-δ composite cathode showed an area specific polarization resistance of 2.4 and 1.9 Ω.cm2 at 700 ºC for oxygen reduction reaction in the air and wet air, respectively, and exhibited an activation energy of 1.2 eV in both atmospheres.