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First China-Japan Workshop on Solid Oxide Fuel Cells

# Investigation on the Power Generation and Electrolysis Behavior of Ni-YSZ∕YSZ∕LSM Cell in Reformate Fuel

[+] Author and Article Information
Chuan-gang Fan1

Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering,  Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan; School of Materials Science and Engineering,  Anhui University of Technology, Maanshan City, Anhui 243002, P.R.C.chgfan@ustc.edu

Tatsuya Iida, Kota Murakami, Toshiaki Matsui, Ryuji Kikuchi, Koichi Eguchi

Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering,  Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan

1

Corresponding author.

J. Fuel Cell Sci. Technol 5(3), 031202 (May 23, 2008) (5 pages) doi:10.1115/1.2927745 History: Received July 13, 2007; Revised December 01, 2007; Published May 23, 2008

## Abstract

The bigger drop of open circuit voltage (OCV) for a degraded or damaged cell unit will make it consume the electricity generated by other cells of the solid oxide fuel cell stack to electrolyze the exhaust gas. In this article, the degradation behaviors of Ni-YSZ∕YSZ $(0.5mmthick)∕La0.6Sr0.4MnO3−δ$ cell sample caused by exhaust of hydrocarbon fuel were studied by solid oxide electrolysis cell method. $I‐V$ curve and impedance spectra measurements were carried out to investigate the polarization feature of the electrodes during power generation and electrolysis at $1000°C$ with gas mixtures of $H2–CO2$, $CO–CO2$, and $H2–H2O$ at the Ni-YSZ working electrode (WE) as well as oxygen at $La0.6Sr0.4MnO3−δ$ counterelectrode. In case of $H2–CO2$ couple, It was found that the increase of $CO2$ only depressed the OCV due to the increase of oxygen partial pressure $(PO2)$ at the WE side, and the characteristics of the cell were more influenced by the $H2O$ produced during power generation. In the case of $CO–CO2$, more CO produced during electrolysis would lead to the carbon deposition, which can result in the increase of polarization resistance by the reduction of the active site (triple phase boundary). In the case of $H2–H2O$ couple, the polarization contribution was different for both power generation and the electrolysis. The former likely contributed from concentration polarization since its nature of producing $H2O$, and the latter mainly contributed to the active site polarization as compared with that from concentration polarization due to its nature of consuming $H2O$.

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## Figures

Figure 1

The schematic of the electrochemical measurement setup for SOFC and SOEC. In this figure, 1 is alumina tube for upstream, 2 alumina tube for downstream, 3 Pt web, 4 LSM electrode, 5 Pyrex glass ring, 6 lead connection to electrochemical apparatus, 7 reference electrode (Pt), 8 YSZ disk, 9 lead wire (Pt), and 10 Ni-YSZ electrode

Figure 2

I‐V characteristics in power generation and electrolysis with various CO2 concentrations from 0% to 10%, H2 concentration of 10% and N2 balance at the WE side, as well as 100% O2 at the CE side, while the total flow rate of 100SCCM for each side. Measurements were carried out at 1000°C.

Figure 3

I‐V characteristics in power generation and electrolysis with various CO2 concentrations from 0% to 10%, CO concentration of 10% and N2 balance at the WE side, as well as 100% O2 at the CE side, while the total flow rate of 100SCCM for each side. Measurements were carried out at 1000°C.

Figure 4

The impedance spectra of cell sample during power generation and electrolysis at 1000°C with the same total flow rate of 100SCCM for both WE and CE sides. The measurements were carried out under varied current density as well as the varied CO2, 10% CO, and N2 balance at the WE side, while 100% O2 at the CE side. Among them: the impedance spectra of the WE for (a) 1% CO2 and (b) 10% CO2; while that of the CE for (c) 1% CO2 and (d) 10% CO2.

Figure 5

I‐V characteristics in power generation and electrolysis with various H2O concentrations from 0% to 30%, H2 concentration of 10% and N2 balance at the WE side, as well as 100% O2 at the CE side, while the total flow rate of 100SCCM for each side. Measurements were carried out at 1000°C.

Figure 6

The impedance spectra of cell sample during power generation and electrolysis at 1000°C with the same total flow rate of 100SCCM for both WE and CE sides. The measurements were carried out under varied current density as well as the varied H2O, 10% H2, and N2 balance at the WE side, while 100% O2 at the CE side. Among them: the impedance spectra of the WE for (a) 30% H2O and (b) 1% H2O; while that of the CE for (c) 30% H2O and (d) 1% H2O.

Figure 7

I‐V characteristics in generation and electrolysis process with various H2 concentrations from 10% to 50%, H2O concentration of 30% and N2 balance at the WE side, as well as 100% O2 at the CE side, while the total flow rate of 100SCCM for each side. Measurements were carried out at 1000°C.

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