Fabrication and Evaluation of a Micro-Tubular Solid Oxide Fuel Cell with an Inert Support Using Scandia-Stabilized Zirconia Electrolyte

Abstract

We have proposed a novel micro-tubular solid oxide fuel cell (SOFC) design with an inert support and an integrated current collector for the inner electrode to improve current collection efficiency as well as reduction-oxidation stability of the cell. In this work, a micro-tubular SOFC based on the proposed design was fabricated using scandia-stabilized zirconia (ScSZ) as electrolyte owing to its high ionic conductivity over a wide range of temperatures. Yttria-stabilized zirconia (YSZ), Ni, Ni-ScSZ, strontium-doped lanthanum manganite (LSM)-ScSZ, and LSM were used as the inert support, anode current collector, anode, cathode, and cathode current collector, respectively. The electrochemical performance of the fabricated cell was evaluated at temperatures between 600 and 850 • C. Because of the lower ohmic resistance across its components, the cell exhibited good power generation performance at high and intermediate temperatures. Solid oxide fuel cells (SOFCs) are high-temperature electrochemical energy conversion devices that have attracted increased attention in recent decades owing to their high power generation efficiency and environmentally benign operation.1,2 In contrast with low-temperature fuel cells such as polymer electrolyte membrane fuel cells (PEMFCs) and alkaline fuel cells (AFCs), SOFCs can be operated with both hydrogen and hydrocarbon fuels, and they are also tolerant toward several fuel contaminants.3-5 Additionally, the high-quality exhaust heat obtained from SOFCs can be used for combined cycle and cogeneration applications, which increases the system efficiency significantly. [6][7][8] Among different SOFC designs, the micro-tubular design possesses some unique characteristics. By combining the merits of a tubular geometry and smaller size, micro-tubular SOFCs offer easy sealing, high volumetric power density, good thermo-cycling behavior, and high thermal shock resistance. 1,9 Owing to their ability for rapid startup and shutdown, micro-tubular SOFCs have gained considerable interest for their use in mobile applications in addition to the traditionally considered stationary applications. 10,11 However, one of the major problems with conventional micro-tubular SOFCs is their poor current collection efficiency. 12,13 This problem arises from the small cell diameter that prevents the use of current-collecting elements such as wires and meshes to collect current from the entire inner electrode surface. As a result, current-collecting elements have to be applied to the exposed end(s) of the inner electrode, which increases the current conduction path and thus the ohmic resistance. This limits active cell length to few centimeters or less so as to keep the ohmic resistance in the cell within an acceptable range.12 In addition, stability of the cell performance under reduction-oxidation (redox) cycling conditions is a crucial issue for conventional micro-tubular SOFCs that contain state-of-the-art Ni-yttria-stabilized zirconia (YSZ) anode supports.14-16 Ni particles in the anode support may oxidiz...

Fabrication and Characterization of High Performance Intermediate Temperature Alumina Substrate Supported Micro-Tubular SOFCs

“…9,20 Recently, yttria-stabilized zirconia (YSZ) was used as anode substrate to improve structural reliability of SOFCs. [21][22][23][24] It is noteworthy that anode electrode accounts for more than 90% materials used by the cell in anode-supported SOFCs. Therefore, the total material cost of anodesupported SOFC unit cell is largely dominated by the cost of anode electrode.…”

Achieving Robust Redox Stability of SOFC through Ni-YSZ Anode Layer Thinning and Inert Support Mechanical Compensation

“…In the recent decade, the inert substrate-supported SOFC has been considered as one of the most promising solutions to redox enhancement. The frequently used materials for inert substrate are zirconia-based ceramics due to the chemical compatibility and thermal expansion matching with other cell components. − In the study of Panthi et al, the fabricated YSZ-supported microtubular SOFC exhibits promising tolerance toward the redox cycling with no apparent degradation after 10 redox cycles . Zhao et al also confirmed the satisfactory redox stability of YSZ-supported SOFC through 7–11 cycles without cell degradation or failure induced by electrolyte fracture. − Compared to YSZ, the 3 mol % yttria stabilized zirconia (3Y-TZP) exhibits a much higher bending strength (1200 vs 279 MPa), which might be a more suitable material of choice for an inert substrate.…”

Morphology and Structure of Ni/Zr0.84Sc0.16O1.92 Electrode Material Synthesized via Glycine-Nitrate Combustion Method for Solid Oxide Electrochemical Cell

“…YSZ is a typical solid electrolyte that is widely studied due to its high phase stability and high ionic conductivity [2]. However, at intermediate temperatures (around 500 • C to 800 • C), it exhibits low ionic conductivity [4]. One promising solid electrolyte is the Sc-doped ZrO 2 (ScSZ) material system that shows higher ionic conductivity than YSZ at lower temperatures [5][6][7].…”

“…Only limited reports have been published on the combination of ScSZ with Ni as an electrode material. In SOFC mode, electrode materials using Ni and 10Sc1CeSZ:ZrO 2 [4], Ni/10 mol%Sc 2 O 3 -1 mol%Y 2 O 3 -stabilized ZrO 2 [8], Ni/10Sc 2 O 3 -1CeO 2 -89ZrO 2 [9,10], Ni/10 mol%Sc 2 O 3 -90 mol % ZrO 2 [10,11], and Ni/Zr 0.81 Sc 0.19 O 1.905 [12] have been reported. For the preparation of these electrode materials, the typical synthesis method involves using a solid state reaction.…”