Energy Materials 2017: Materials for Energy Conversion with Emphasis on SOFC: Session II
Sponsored by: Chinese Society for Metals
Program Organizers: Amit Pandey, LG Fuel Cell Systems Inc.; Kyle Brinkman, Clemson University; Teruhisa Horita, AIST; Minfang Han, China University of Mining and Technology, Beijing
Monday 2:00 PM
February 27, 2017
Location: San Diego Convention Ctr
Session Chair: Jung Choi, PNNL; Kyle Brinkman, Clemson University
2:00 PM Invited
Plasma Sprayed Protective Coatings on Metallic SOFC Interconnects: Interplay between Processing and Performance: Sanjay Sampath1; Su Jung Han1; Hwasoo Lee1; 1Stony Brook University
Conductive oxides coatings are applied onto metallic interconnects via plasma spray to prevent chrome poisoning and cell degradation. Most common materials include Strontium doped Lanthanum Manganite (La(Sr)MnO3) or Manganese cobalt spinel (Mn1.5Co1.5O4). The characteristics and performance of these sprayed coatings are strongly dependent on their processing since these coatings have significant process induced defects. For instance the strong thermal gradients within the plasma can cause preferential evaporation of certain cations which can affect the stoichiometry and phases as well as oxidation state of the deposited materials. These chemical changes combined with physical defects such as pores, cracks and interfaces can lead to ineffective protective and functional performance. However, through judicious selection of process paramters constructed through the framework of process maps and advanced property measurements enabled synthesis of high quality deposits. This presentation will provide illustrative examples of the process mapping concepts in context both protective and functional performance.
Chromium Impurity Effects on SOFC Cathodes Using Half-cell Measurements: Yiwen Gong1; Yuexing Zhu1; Soumendra Basu1; Uday Pal1; Srikanth Gopalan1; 1Boston University
High efficiency, negligible pollution and clean energy make solid oxide fuel cells(SOFCs) attractive for distributed generation. The lower operating temperature enables the deployment of metallic interconnects based on ferritic stainless steel, like Crofer 22 APU. However, the chromia oxide scale that forms on the surface of the Crofer 22 APU alloy will react with the oxygen and water vapor to form volatile chromium species which will degrade the cathodes. In order to understanding the mechanism of the chromium poisoning in SOFC, electrolyte-supported half-cells have been fabricated. These half-cells have been tested at different temperatures with different humidity levels in the air, with and without mechanically contacting the Crofer 22 APU alloy. Galvanostatic current interruption (GCI) has been employed during the electrochemical test and after the test, scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX) have been used to measure the composition near the TBPs.
2:50 PM Invited
Development of Solid Oxide Fuel Cell Residential CHP System: Yuya Takuwa1; Shuichi Inoue1; Minoru Suzuki1; 1Osaka Gas Co.,Ltd
Osaka Gas began selling the new version residential SOFC CHP system “ENE-FARM type S” in April 2016, which is developed in collaboration with Osaka Gas, Aisin Seiki, Kyocera and Noritz. Kyocera manufactures cell stacks, Aisin Seiki manufactures power generation units, and Noritz manufactures hot water supply units and remote control units. Power efficiency was improved to 52%(net AC,LHV), previous one 46.5%. It achieves a minimum size as a residential CHP system. Kyocera reduced the internal resistance of cell stack. And new coating technology that was developed Osaka Gas and Kyocera were used for the inter-cell connection parts. As a result, both reducing number of cells and improvement of power efficiency have been achieved. Moreover, Aisin Seiki has developed the power generation unit and the hot module for high power efficiency. We also started to trade surplus electricity from new SOFC CHP system.
Effect of Strontium Content and Strain on Surface Segregation in LSCF: Yang Yu1; Karl Ludwig1; Srikanth Gopalan1; Uday Pal1; Soumendra Basu1; 1Boston University
Strontium doped lanthanum cobalt ferrite (LSCF) is a widely used cathode material in solid oxide fuel cells (SOFC). However, LSCF can have long-term stability issues that can adversely affect electrochemical performance. In this study, heteroepitaxial thin films of La1-x SrxCo0.2Fe0.8O3-δ with varying Sr content (x = 0.4, 0.3, 0.2) were deposited on single crystal NdGaO3, SrTiO3 and GdScO3 substrates by pulsed laser deposition, leading to different strains in the films. The extent of Sr-rich precipitate formation at the film surface was quantified using the synchrotron-based total reflection X-ray fluorescence (TXRF), and atomic force microscopy (AFM). The microstructure and the bonding of the surface Sr-rich phases were investigated by scanning/transmission electron microscopy (S/TEM) and hard x-ray photoelectron spectroscopy (HAXPES), respectively. The strain in the thin films was measured by high-resolution x-ray diffraction (HRXRD). The effect of the strontium content and strain on the extent of surface phase formation will be discussed.
3:35 PM Break
Fabrication and Operation of a 600W Anode-supported Tubular SOFC Stack: Zhengguang Yu1; Shaorong Wang2; 1Dongfang Turbine Co.,Ltd ; 2Shanghai Institute of Ceramics, Chinese Academy of Sciences
A NiO-YSZ anode-supported tubular SOFC stack for high temperature operation was fabricated and operated in this work. For this purpose, we fabricated anode-supported tubular cells with one end closed by casting, dip coating and co-sintering process. After that, the 600W stack was assembled with these prepared tubular cells by connecting in series to 16 bundles, in which one unit bundle consists of three tubular cells connected in parallel. Experimental results show that single cell with an effective electrode area of 70 cm2 was found to give a maximum peak power density of 310mW/cm2 at 850°C , Moreover, these cells also exhibit less than 2% degradation after 10 times thermal cycles. However, using a kind of Nickel alloy materials (Hasteloy C-276) as current connector, the performance of the stack in 3% humidified H2 and air at 850 °C outputted a maximum electrical power of 588 W (fuel utilization ratio =34%).
4:15 PM Cancelled
Phase Stability and Electrical Properties of La2NiO4: Rare-Earth Doped Ceria Composite Cathode Materials for Solid Oxide Fuel Cells: Deniz Cetin1; Sophie Poizeau2; Srikanth Gopalan1; 1Boston University; 2Saint Gobain Northborough R&D Center
Lanthanum nickelate exhibits competitive surface oxygen transport properties and comparable electrical conduction compared to perovskite-type oxides. Even though it exhibits great potential for replacing the perovskite-type alternatives in SOFC cathodes, lanthanum nickelate suffers from phase stability issues when in contact with doped-cerias. In this study, we introduce a rational thermodynamics-based methodology to stabilize the chemical composition of the composite La2NiO4: rare-earth doped ceria compositions. Phase stability studies based on X-ray diffractometry, dilatometry analysis and electrical conductivity measurements as functions of temperature, oxygen partial pressure and nature of the rare-earth cation will be presented. Further, electrochemical characterization of button cells featuring the stabilized cathode compositions will be presented. All components of the button cells with composite MIEC cathode active layers were prepared via tape casting. The effect of cathode microstructure and thickness on the cell performance is also discussed.