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Cobalt-free cathode material SrFe0.9Nb0.1O3−δ for intermediate-temperature solid oxide fuel cells
Electrochemistry Communications 12 (2010) 285–287
Contents lists available at ScienceDirect
Electrochemistry Communications journal homepage: www.elsevier.com/locate/elecom
Cobalt-free cathode material SrFe0.9Nb0.1O3 solid oxide fuel cells
d
for intermediate-temperature
Qingjun Zhou a,b, Leilei Zhang a, Tianmin He a,* a b
State Key Laboratory of Superhard Materials and College of Physics, Jilin University, Changchun 130012, PR China College of Science, Civil Aviation University of China, Tianjin 300300, PR China
a r t i c l e
i n f o
Article history: Received 9 November 2009 Received in revised form 9 December 2009 Accepted 11 December 2009 Available online 21 December 2009 Keywords: Solid oxide fuel cell Cobalt-free cathode Electrical conductivity SrFe0.9Nb0.1O3 d Electrochemical performance
a b s t r a c t A cobalt-free cubic perovskite oxide, SrFe0.9Nb0.1O3 d (SFN) was investigated as a cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). XRD results showed that SFN cathode was chemically compatible with the electrolyte Sm0.2Ce0.8O1.9 (SDC) for temperatures up to 1050 °C. The electrical conductivity of SFN sample reached 34–70 S cm 1 in the commonly operated temperatures of IT-SOFCs (600–800 °C). The area specific resistance was 0.138 X cm2 for SFN cathode on SDC electrolyte at 750 °C. A maximum power density of 407 mW cm 2 was obtained at 800 °C for single-cell with 300 lm thick SDC electrolyte and SFN cathode. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction In recent years, solid oxide fuel cells (SOFCs) have attracted much interest as one of the promising power generation technologies because of their advantages of high power generation efficiency, low pollution and good fuel flexibility. Typical SOFCs with yttria stabilized zirconia electrolytes and the conventional La1 xSrxMnO3 (LSM) cathodes need to operate at about 1000 °C, thus leading to some troublesome problems such as high temperature seal and reactions between cell components. One effective way to overcome this problem is to reduce the operating temperature of the SOFCs to intermediate temperature (600–800 °C). However, the interfacial polarization resistance between the cathode and electrolyte increases rapidly with lowering operating temperature [1]. Thus it is critical to develop cathode materials with low polarization losses and high stability for IT-SOFCs. Many perovskite-type mixed ionic–electronic conductors (MIECs) such as Ln1 xSrxCo1 yFeyO3 d (Ln = rare-earth) [2–4], Ba1 xSrxCo1 yFeyO3 d [5–7], LnBaCo2O5+d [8–10] and LaBaCuMO5+x (M = Fe and Co) [11] have been investigated as possible cathodes for IT-SOFCs. These cobalt-based cathodes have exhibited higher electrocatalytic performance than that of the conventional LSM cathodes. However, these cobalt-based cathodes often encountered some problems like high thermal expansion coefficient, poor stability and high cost of cobalt element. Therefore, it is desirable to * Corresponding author. Fax: +86 431 88498000. E-mail addresses: [email protected], [email protected] (T. He). 1388-2481/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2009.12.016
develop the cobalt-free cathodes with good electrocatalytic activity for IT-SOFCs. Strontium ferrite SrFeO3 d is a typical MIEC [12]. But the drawback of such material is their low chemical and structural stability. Recently, Anikina et al. [13,14] demonstrated that partial substitution of niobium for iron was an efficient way to improve transport characteristics and enhance thermodynamic stability of SrFeO3 d. The 10 mol% Nb doped-SrFeO3 d was found to be a singular composition where oxygen ion conductivity attained a maximum while activation energy for ion transport was minimal. At 950 °C, SrFe0.9Nb0.1O3 d membrane exhibited highest oxygen permeation flux [14]. However, to the best of our knowledge, the performance of SrFe0.9Nb0.1O3 d as potential cathode has not been reported to date. In this study, as a first study, we investigated the performance of SrFe0.9Nb0.1O3 d as a cobalt-free cathode material for IT-SOFCs.
2. Experimental The sample of SrFe0.9Nb0.1O3 d (SFN) was prepared with a solidstate reaction. The stoichiometric amounts of Fe2O3 (99.5%), Nb2O5 (99%) and SrCO3 (99%) were carefully ground, then pressed into pellets and calcined repeatedly at 1000 °C and 1200 °C for 12 h with intermediate grindings, respectively, The calcined powders were ground again and finally sintered at 1350 °C for 5 h in air. Sm0.2Ce0.8O1.9 (SDC) electrolyte material and NiO powders were synthesized using the glycine-nitrate process [15].
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Q. Zhou et al. / Electrochemistry Communications 12 (2010) 285–287
A symmetrical cell SFN/SDC/SFN was used for electrochemical impedance spectroscopy (EIS) measurements. The cathode was screen-printed onto the dense SDC electrolyte pellets. After drying, the SFN cathode was sintered at 1050 °C for 2 h in air. Electrolyte supported single-cell was fabricated using 300 lm thick SDC electrolyte pellets, SFN as cathode, and NiO-SDC (in a weight ratio of 65:35) as anode. The anode was screen-painted onto the SDC electrolyte and then sintered at 1250 °C for 4 h in air. Similarly, the SFN cathode was screen-painted onto the opposite side of the SDC pellet and sintered at 1050 °C for 2 h. The phase identification of the prepared SFN powders and the phase reactivity between cathode and electrolyte were studied with the powder X-ray diffractometer (XRD) (Rigaku-D-Max cA). Electrical conductivity of the sample was measured using Van der Pauw method in a temperature range from room temperature to 900 °C in air. The microstructure of the cell after testing was inspected with a scanning electron microscope (SEM, JEOL JSM6480LV). EIS measurement was carried out with an electrochemical workstation (CHI604C) in the temperature range of 650– 800 °C in air. The frequency range from 0.01 Hz to 100 kHz was applied and the signal amplitude was 10 mV under open cell voltage condition. Single-cell was tested with dry hydrogen as fuel and ambient air as oxidant at various temperatures.
Fig. 2. Temperature dependence of the electrical conductivity for SFN sample.
Fig. 1(a) shows the XRD pattern of SFN powders sintered at 1350 °C for 5 h in air. It is found that the SFN oxide crystallizes in a cubic perovskite structure (space group Pm-3m), which is in good agreement with that reported in the literature [13]. To assess the phase reaction between SFN cathode and SDC electrolyte, the chemical compatibility of the SFN cathode with the SDC electrolyte was investigated by sintering the mixed powders of SFN and SDC in a weight ratio of 1:1 at 1050 °C for 5 h. Fig. 1(b) and (c) shows the XRD patterns of the SDC powders and the SFN–SDC mixture, respectively. No additional diffraction peaks and any peak shifts are observed, indicating that the SFN cathode is chemically compatible with the SDC electrolyte at 1050 °C for 5 h. Fig. 2 shows the temperature dependence of the electrical conductivity of SFN sample in air. It can be seen there is an abrupt change of slope at around 425 °C, which undergoes a semiconducting-like conduction behavior to metal-like conduction behavior.
The conductivity of sample achieves a maximum of 105 S cm 1 at this temperature. The conductivity of sample subsequently decreases with increasing temperature beyond 425 °C. The decrease of the conductivity is mainly associated with the loss of the lattice oxygen at elevated temperature [11,14]. The conductivity values of the SFN sample in the temperature range of IT-SOFCs (600–800 °C) are 34–70 S cm 1, which are higher than the maximum conductivity of BaxSr1 xCo0.8Fe0.2O3 d at 600 °C [16]. Fig. 3(a) shows the typical impedance spectra of the SFN cathode obtained at different temperatures in air. The impedance response for oxygen reduction on the SFN cathode is characterized by both a high-frequency arc and a low-frequency arc, indicating that there are at least two limiting reaction steps for the oxygen reduction reaction. The difference between the low-frequency and the high-frequency intercepts on the real axis corresponds to the area specific resistance (ASR) of the two interfaces [17]. The ASR value is 0.725, 0.290, 0.138 and 0.083 X cm2 at 650, 700, 750 and 800 °C, respectively. The corresponding activation energy value calculated from the slope of Fig. 3(b) is 1.24 eV. These ASR values are significantly lower than those of other cobalt-free
Fig. 1. XRD patterns of (a) SFN powders, (b) SDC powders and (c) SFN-SDC mixture sintered at 1050 °C for 5 h.
Fig. 3. (a) Typical impedance spectra of SFN cathode on SDC electrolyte measured at 650–800 °C in air, and (b) Arrhenius plot of ASR for SFN cathode.
3. Results and discussion
Q. Zhou et al. / Electrochemistry Communications 12 (2010) 285–287
287
the cathode is lower and the particle-size distribution is not uniform as compared to the anode (Fig. 4(b)). Therefore, the cathode performance would be further enhanced through optimizing the SFN cathode microstructures. Fig. 5 shows the single-cell performance of Ni-SDC/SDC/SFN operating at different temperatures with dry hydrogen as fuel and ambient air as oxidant. The maximum power densities of the single-cell reach 407, 287, 161 and 82 mW cm 2 at 800, 750, 700 and 650 °C, respectively. This shows that a good cell performance can be obtained using the SFN cathode and SDC electrolyte. Moreover, the cell performance would be further enhanced through optimizing the SFN cathode microstructures and using an SDC film as the electrolyte. 4. Conclusions
Fig. 4. SEM micrographs of (a) SFN/SDC and (b) Ni-SDC/SDC interfaces after cell testing.
The cubic perovskite oxide SrFe0.9Nb0.1O3 d as synthesized by a solid-state reaction and assessed as a cathode for IT-SOFCs. The SFN cathode was chemically compatible with SDC electrolyte when the sintering temperature was below 1050 °C. The ASRs of the SFN cathode on SDC electrolyte were 0.725, 0.290, 0.138 and 0.083 X cm2 at 650, 700, 750 and 800 °C in air, respectively. A peak power density of single-cell reached 407 mW cm 2 at 800 °C with 300 lm thick SDC electrolyte by adopting SFN cathode. Preliminary results demonstrated that the SFN oxide was a very promising candidate as a cathode for IT-SOFCs. Acknowledgement This work was supported by the Natural Science Foundation of China under contract No. 10974065. References
Fig. 5. Cell performance of Ni-SDC/SDC/SFN at different temperatures using dry H2 as fuel and ambient air as oxidant.
cathodes reported by various groups, such as [18], Pr0.7Sr0.3Fe1 xNixO3 d [19], La0.4Sr0.6Ni0.2Fe0.8O3 d La0.7Sr0.3Cu1 xFexO3 d [20] and Sm2 xSrxNiO4 [21], and are also lower than those of the cobalt-containing cathodes like SmSrCoO4 d [22] and Ba1.2Sr0.8CoO4 d [23]. This indicates that the SFN oxide has a high electrocatalytic activity for oxygen reduction. It is a promising candidate as a cathode material for IT-SOFCs. The thermal compatibility between the cathode and electrolyte was examined after cell testing. Fig. 4(a) shows the SEM micrograph of the SFN cathode and SDC electrolyte interface after cell testing. The SEM micrograph clearly shows that the SFN cathode and SDC electrolyte has a good bonding and continuous contact at the interface. There is no delamination and crack in the cathode, suggesting a good thermal compatibility between the two materials. However, the SEM micrograph also shows that the porosity in
[1] V. Dusastre, J.A. Kilner, Solid State Ionics 126 (1999) 163. [2] H.Y. Tu, Y. Takeda, N. Imanishi, O. Yamamoto, Solid State Ionics 117 (1999) 277. [3] H.J. Hwang, M.B. Ji-Woong, L.A. Seunghun, E.A. Lee, J. Power Sources 145 (2005) 243. [4] L. Qiu, T. Ichikawa, A. Hirano, N. Zmanishi, Y. Takeda, Solid State Ionics 158 (2003) 55. [5] Z.P. Shao, S.M. Haile, Nature 431 (2004) 170. [6] Z.S. Duan, M. Yang, A.Y. Yan, Z.F. Hou, Y.L. Dong, Y. Chong, M.J. Cheng, W.S. Yang, J. Power Sources 160 (2006) 57. [7] S. Lee, Y. Lim, E.A. Lee, H.J. Hwang, J.W. Moon, J. Power Sources 157 (2006) 848. [8] A.M. Chang, S.J. Skinner, A. Kilner, Solid State Ionics 177 (2006) 2009. [9] J.-H. Kim, A. Manthiram, J. Electrochem. Soc. 155 (4) (2008) B385. [10] Q.J. Zhou, T.M. He, Y. Ji, J. Power Sources 185 (2008) 754. [11] Q.J. Zhou, T.M. He, Q. He, Y. Ji, Electrochem. Commun. 11 (2009) 80. [12] Y. Teraoka, S. Furukawa, H.M. Zhang, N. Yamazoe, Nippon Kagaku Kaishi 1988 (1988) 1084. [13] P.V. Anikina, A.A. Markov, M.V. Patrakeev, I.A. Leonidov, V.L. Kozhevnikov, Russ. J. Phys. Chem. 83 (2009) 699. [14] P.V. Anikina, A.A. Markov, M.V. Patrakeev, I.A. Leonidov, V.L. Kozhevnikov, Solid State Sci. 11 (2009) 1156. [15] L. Cong, T. He, Y. Ji, P. Guan, Y. Huang, W. Su, J. Alloy. Compd. 348 (2003) 325. [16] B. Wei, Z. Lü, X.Q. Huang, J.P. Miao, X.Q. Sha, X.S. Xin, W.H. Su, J. Eur. Ceram. Soc. 26 (2006) 2827. [17] E.P. Murray, S.A. Barnett, Solid State Ionics 143 (2001) 265. [18] G.Y. Zhu, X.H. Fang, C.R. Xia, X.Q. Liu, Ceram. Int. 31 (2005) 115. [19] S.-I. Hashimoto, K. Kammer, P.H. Larsen, F.W. Poulsen, M. Mogensen, Solid State Ionics 176 (2005) 1013. [20] X.F. Ding, C. Cui, X.J. Du, L.C. Guo, J. Alloy. Compd. 475 (2009) 418. [21] Q. Li, Y. Fan, H. Zhao, L.P. Sun, L.H. Huo, J. Power Sources 167 (2007) 64. [22] Y.S. Wang, H.W. Nie, S.R. Wang, T.L. Wen, U. Guth, V. Valshook, Mater. Lett. 60 (2006) 1174. [23] C. Jin, J. Liu, J. Alloy. Compd. 474 (2009) 573.
Contents lists available at ScienceDirect
Electrochemistry Communications journal homepage: www.elsevier.com/locate/elecom
Cobalt-free cathode material SrFe0.9Nb0.1O3 solid oxide fuel cells
d
for intermediate-temperature
Qingjun Zhou a,b, Leilei Zhang a, Tianmin He a,* a b
State Key Laboratory of Superhard Materials and College of Physics, Jilin University, Changchun 130012, PR China College of Science, Civil Aviation University of China, Tianjin 300300, PR China
a r t i c l e
i n f o
Article history: Received 9 November 2009 Received in revised form 9 December 2009 Accepted 11 December 2009 Available online 21 December 2009 Keywords: Solid oxide fuel cell Cobalt-free cathode Electrical conductivity SrFe0.9Nb0.1O3 d Electrochemical performance
a b s t r a c t A cobalt-free cubic perovskite oxide, SrFe0.9Nb0.1O3 d (SFN) was investigated as a cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). XRD results showed that SFN cathode was chemically compatible with the electrolyte Sm0.2Ce0.8O1.9 (SDC) for temperatures up to 1050 °C. The electrical conductivity of SFN sample reached 34–70 S cm 1 in the commonly operated temperatures of IT-SOFCs (600–800 °C). The area specific resistance was 0.138 X cm2 for SFN cathode on SDC electrolyte at 750 °C. A maximum power density of 407 mW cm 2 was obtained at 800 °C for single-cell with 300 lm thick SDC electrolyte and SFN cathode. Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction In recent years, solid oxide fuel cells (SOFCs) have attracted much interest as one of the promising power generation technologies because of their advantages of high power generation efficiency, low pollution and good fuel flexibility. Typical SOFCs with yttria stabilized zirconia electrolytes and the conventional La1 xSrxMnO3 (LSM) cathodes need to operate at about 1000 °C, thus leading to some troublesome problems such as high temperature seal and reactions between cell components. One effective way to overcome this problem is to reduce the operating temperature of the SOFCs to intermediate temperature (600–800 °C). However, the interfacial polarization resistance between the cathode and electrolyte increases rapidly with lowering operating temperature [1]. Thus it is critical to develop cathode materials with low polarization losses and high stability for IT-SOFCs. Many perovskite-type mixed ionic–electronic conductors (MIECs) such as Ln1 xSrxCo1 yFeyO3 d (Ln = rare-earth) [2–4], Ba1 xSrxCo1 yFeyO3 d [5–7], LnBaCo2O5+d [8–10] and LaBaCuMO5+x (M = Fe and Co) [11] have been investigated as possible cathodes for IT-SOFCs. These cobalt-based cathodes have exhibited higher electrocatalytic performance than that of the conventional LSM cathodes. However, these cobalt-based cathodes often encountered some problems like high thermal expansion coefficient, poor stability and high cost of cobalt element. Therefore, it is desirable to * Corresponding author. Fax: +86 431 88498000. E-mail addresses: [email protected], [email protected] (T. He). 1388-2481/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2009.12.016
develop the cobalt-free cathodes with good electrocatalytic activity for IT-SOFCs. Strontium ferrite SrFeO3 d is a typical MIEC [12]. But the drawback of such material is their low chemical and structural stability. Recently, Anikina et al. [13,14] demonstrated that partial substitution of niobium for iron was an efficient way to improve transport characteristics and enhance thermodynamic stability of SrFeO3 d. The 10 mol% Nb doped-SrFeO3 d was found to be a singular composition where oxygen ion conductivity attained a maximum while activation energy for ion transport was minimal. At 950 °C, SrFe0.9Nb0.1O3 d membrane exhibited highest oxygen permeation flux [14]. However, to the best of our knowledge, the performance of SrFe0.9Nb0.1O3 d as potential cathode has not been reported to date. In this study, as a first study, we investigated the performance of SrFe0.9Nb0.1O3 d as a cobalt-free cathode material for IT-SOFCs.
2. Experimental The sample of SrFe0.9Nb0.1O3 d (SFN) was prepared with a solidstate reaction. The stoichiometric amounts of Fe2O3 (99.5%), Nb2O5 (99%) and SrCO3 (99%) were carefully ground, then pressed into pellets and calcined repeatedly at 1000 °C and 1200 °C for 12 h with intermediate grindings, respectively, The calcined powders were ground again and finally sintered at 1350 °C for 5 h in air. Sm0.2Ce0.8O1.9 (SDC) electrolyte material and NiO powders were synthesized using the glycine-nitrate process [15].
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Q. Zhou et al. / Electrochemistry Communications 12 (2010) 285–287
A symmetrical cell SFN/SDC/SFN was used for electrochemical impedance spectroscopy (EIS) measurements. The cathode was screen-printed onto the dense SDC electrolyte pellets. After drying, the SFN cathode was sintered at 1050 °C for 2 h in air. Electrolyte supported single-cell was fabricated using 300 lm thick SDC electrolyte pellets, SFN as cathode, and NiO-SDC (in a weight ratio of 65:35) as anode. The anode was screen-painted onto the SDC electrolyte and then sintered at 1250 °C for 4 h in air. Similarly, the SFN cathode was screen-painted onto the opposite side of the SDC pellet and sintered at 1050 °C for 2 h. The phase identification of the prepared SFN powders and the phase reactivity between cathode and electrolyte were studied with the powder X-ray diffractometer (XRD) (Rigaku-D-Max cA). Electrical conductivity of the sample was measured using Van der Pauw method in a temperature range from room temperature to 900 °C in air. The microstructure of the cell after testing was inspected with a scanning electron microscope (SEM, JEOL JSM6480LV). EIS measurement was carried out with an electrochemical workstation (CHI604C) in the temperature range of 650– 800 °C in air. The frequency range from 0.01 Hz to 100 kHz was applied and the signal amplitude was 10 mV under open cell voltage condition. Single-cell was tested with dry hydrogen as fuel and ambient air as oxidant at various temperatures.
Fig. 2. Temperature dependence of the electrical conductivity for SFN sample.
Fig. 1(a) shows the XRD pattern of SFN powders sintered at 1350 °C for 5 h in air. It is found that the SFN oxide crystallizes in a cubic perovskite structure (space group Pm-3m), which is in good agreement with that reported in the literature [13]. To assess the phase reaction between SFN cathode and SDC electrolyte, the chemical compatibility of the SFN cathode with the SDC electrolyte was investigated by sintering the mixed powders of SFN and SDC in a weight ratio of 1:1 at 1050 °C for 5 h. Fig. 1(b) and (c) shows the XRD patterns of the SDC powders and the SFN–SDC mixture, respectively. No additional diffraction peaks and any peak shifts are observed, indicating that the SFN cathode is chemically compatible with the SDC electrolyte at 1050 °C for 5 h. Fig. 2 shows the temperature dependence of the electrical conductivity of SFN sample in air. It can be seen there is an abrupt change of slope at around 425 °C, which undergoes a semiconducting-like conduction behavior to metal-like conduction behavior.
The conductivity of sample achieves a maximum of 105 S cm 1 at this temperature. The conductivity of sample subsequently decreases with increasing temperature beyond 425 °C. The decrease of the conductivity is mainly associated with the loss of the lattice oxygen at elevated temperature [11,14]. The conductivity values of the SFN sample in the temperature range of IT-SOFCs (600–800 °C) are 34–70 S cm 1, which are higher than the maximum conductivity of BaxSr1 xCo0.8Fe0.2O3 d at 600 °C [16]. Fig. 3(a) shows the typical impedance spectra of the SFN cathode obtained at different temperatures in air. The impedance response for oxygen reduction on the SFN cathode is characterized by both a high-frequency arc and a low-frequency arc, indicating that there are at least two limiting reaction steps for the oxygen reduction reaction. The difference between the low-frequency and the high-frequency intercepts on the real axis corresponds to the area specific resistance (ASR) of the two interfaces [17]. The ASR value is 0.725, 0.290, 0.138 and 0.083 X cm2 at 650, 700, 750 and 800 °C, respectively. The corresponding activation energy value calculated from the slope of Fig. 3(b) is 1.24 eV. These ASR values are significantly lower than those of other cobalt-free
Fig. 1. XRD patterns of (a) SFN powders, (b) SDC powders and (c) SFN-SDC mixture sintered at 1050 °C for 5 h.
Fig. 3. (a) Typical impedance spectra of SFN cathode on SDC electrolyte measured at 650–800 °C in air, and (b) Arrhenius plot of ASR for SFN cathode.
3. Results and discussion
Q. Zhou et al. / Electrochemistry Communications 12 (2010) 285–287
287
the cathode is lower and the particle-size distribution is not uniform as compared to the anode (Fig. 4(b)). Therefore, the cathode performance would be further enhanced through optimizing the SFN cathode microstructures. Fig. 5 shows the single-cell performance of Ni-SDC/SDC/SFN operating at different temperatures with dry hydrogen as fuel and ambient air as oxidant. The maximum power densities of the single-cell reach 407, 287, 161 and 82 mW cm 2 at 800, 750, 700 and 650 °C, respectively. This shows that a good cell performance can be obtained using the SFN cathode and SDC electrolyte. Moreover, the cell performance would be further enhanced through optimizing the SFN cathode microstructures and using an SDC film as the electrolyte. 4. Conclusions
Fig. 4. SEM micrographs of (a) SFN/SDC and (b) Ni-SDC/SDC interfaces after cell testing.
The cubic perovskite oxide SrFe0.9Nb0.1O3 d as synthesized by a solid-state reaction and assessed as a cathode for IT-SOFCs. The SFN cathode was chemically compatible with SDC electrolyte when the sintering temperature was below 1050 °C. The ASRs of the SFN cathode on SDC electrolyte were 0.725, 0.290, 0.138 and 0.083 X cm2 at 650, 700, 750 and 800 °C in air, respectively. A peak power density of single-cell reached 407 mW cm 2 at 800 °C with 300 lm thick SDC electrolyte by adopting SFN cathode. Preliminary results demonstrated that the SFN oxide was a very promising candidate as a cathode for IT-SOFCs. Acknowledgement This work was supported by the Natural Science Foundation of China under contract No. 10974065. References
Fig. 5. Cell performance of Ni-SDC/SDC/SFN at different temperatures using dry H2 as fuel and ambient air as oxidant.
cathodes reported by various groups, such as [18], Pr0.7Sr0.3Fe1 xNixO3 d [19], La0.4Sr0.6Ni0.2Fe0.8O3 d La0.7Sr0.3Cu1 xFexO3 d [20] and Sm2 xSrxNiO4 [21], and are also lower than those of the cobalt-containing cathodes like SmSrCoO4 d [22] and Ba1.2Sr0.8CoO4 d [23]. This indicates that the SFN oxide has a high electrocatalytic activity for oxygen reduction. It is a promising candidate as a cathode material for IT-SOFCs. The thermal compatibility between the cathode and electrolyte was examined after cell testing. Fig. 4(a) shows the SEM micrograph of the SFN cathode and SDC electrolyte interface after cell testing. The SEM micrograph clearly shows that the SFN cathode and SDC electrolyte has a good bonding and continuous contact at the interface. There is no delamination and crack in the cathode, suggesting a good thermal compatibility between the two materials. However, the SEM micrograph also shows that the porosity in
[1] V. Dusastre, J.A. Kilner, Solid State Ionics 126 (1999) 163. [2] H.Y. Tu, Y. Takeda, N. Imanishi, O. Yamamoto, Solid State Ionics 117 (1999) 277. [3] H.J. Hwang, M.B. Ji-Woong, L.A. Seunghun, E.A. Lee, J. Power Sources 145 (2005) 243. [4] L. Qiu, T. Ichikawa, A. Hirano, N. Zmanishi, Y. Takeda, Solid State Ionics 158 (2003) 55. [5] Z.P. Shao, S.M. Haile, Nature 431 (2004) 170. [6] Z.S. Duan, M. Yang, A.Y. Yan, Z.F. Hou, Y.L. Dong, Y. Chong, M.J. Cheng, W.S. Yang, J. Power Sources 160 (2006) 57. [7] S. Lee, Y. Lim, E.A. Lee, H.J. Hwang, J.W. Moon, J. Power Sources 157 (2006) 848. [8] A.M. Chang, S.J. Skinner, A. Kilner, Solid State Ionics 177 (2006) 2009. [9] J.-H. Kim, A. Manthiram, J. Electrochem. Soc. 155 (4) (2008) B385. [10] Q.J. Zhou, T.M. He, Y. Ji, J. Power Sources 185 (2008) 754. [11] Q.J. Zhou, T.M. He, Q. He, Y. Ji, Electrochem. Commun. 11 (2009) 80. [12] Y. Teraoka, S. Furukawa, H.M. Zhang, N. Yamazoe, Nippon Kagaku Kaishi 1988 (1988) 1084. [13] P.V. Anikina, A.A. Markov, M.V. Patrakeev, I.A. Leonidov, V.L. Kozhevnikov, Russ. J. Phys. Chem. 83 (2009) 699. [14] P.V. Anikina, A.A. Markov, M.V. Patrakeev, I.A. Leonidov, V.L. Kozhevnikov, Solid State Sci. 11 (2009) 1156. [15] L. Cong, T. He, Y. Ji, P. Guan, Y. Huang, W. Su, J. Alloy. Compd. 348 (2003) 325. [16] B. Wei, Z. Lü, X.Q. Huang, J.P. Miao, X.Q. Sha, X.S. Xin, W.H. Su, J. Eur. Ceram. Soc. 26 (2006) 2827. [17] E.P. Murray, S.A. Barnett, Solid State Ionics 143 (2001) 265. [18] G.Y. Zhu, X.H. Fang, C.R. Xia, X.Q. Liu, Ceram. Int. 31 (2005) 115. [19] S.-I. Hashimoto, K. Kammer, P.H. Larsen, F.W. Poulsen, M. Mogensen, Solid State Ionics 176 (2005) 1013. [20] X.F. Ding, C. Cui, X.J. Du, L.C. Guo, J. Alloy. Compd. 475 (2009) 418. [21] Q. Li, Y. Fan, H. Zhao, L.P. Sun, L.H. Huo, J. Power Sources 167 (2007) 64. [22] Y.S. Wang, H.W. Nie, S.R. Wang, T.L. Wen, U. Guth, V. Valshook, Mater. Lett. 60 (2006) 1174. [23] C. Jin, J. Liu, J. Alloy. Compd. 474 (2009) 573.