Anode-Supported SC-SOFCs

In SOFCs, one of the major sources of poIari2ation losses is the ohmic resistance [16]. A possibility for reducing the ohmic resistance is to decrease the electrolyte thickness to a few tens of micrometers [56], which in turn also permits a decrease in the operating temperature. In order to maintain mechanical stabihty, a thick anode is used as support for the thin electrolyte. Anode-supported SC-SOFCs use the same electrode and electrolyte materials as the electrolyte-supported SC-SOFCs. 

The first investigation on anode-supported cells operated under single-chamber conditions was reported by Jasinski etal. [39]. With 760mWcm measured for a Ni-SDC SDC BSCF-SDC cell at 750°C in a methane-air mixture, anode-supported SC-SOFCs delivered the highest power output for SC-SOFCs measured thus far [57]. They could also be successfully operated with liquid fuels [45] and at very low temperatures (200-250 °C) [30]. 

Compared with electrolyte-supported cells, anode-supported cells can deliver higher power outputs and be operated at lower temperatures [30, 39, 57]- Due to 

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Basu RN, Blafi G, Buchkremer HP, Stover D, Tietz F, Wessel E, et al. Fabrication of simplified anode supported planar SOFCs—a recent attempt. In Yokokawa H, Singhal SC, editors. Proceedings of the Seventh International Symposium on Solid Oxide Fuel Cells (SOFC-VII), Pennington, NJ The Electrochemical Society, 2001 2001(16) 995-1001. 

A further study [81] examined the development of internal stress as a function of temperature for an anode-supported cell based on a Sc stabilized zirconia (ScSZ) electrolyte with a NiO-3 mol%-YSZ anode, finding that there were significant changes in the internal stress in both NiO and ScSZ that were not fully reversible, Fig. 19.10. Residual stress in the electrolyte was measured as a function of the reduction cycle and found to be 400 MPa in air, but decreased to 200 MPa on reduction of the NiO, and concluded that this redox cycle would be detrimental to SOFC performance. 

Nappom et al. (2004) investigated the operating conditions of two versions of a SC-SOFC with an YSZ electrolyte one version electrolyte supported, the other version anode supported. The anode-supported cells operate in a narrower range of methane/air ratios but offer remarkable maximum values of specific power 360 and 285 mW/cm at 800 and 700°C, respectively. 

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