Degradation of solid oxide electrolysis cells: Phenomena, mechanisms, and emerging mitigation strategies—A review

doi:10.1016/j.jmst.2019.07.026

Abstract

Abstract:

Solid oxide electrolysis cell (SOEC) is a promising electrochemical device with high efficiency for energy storage and conversion. However, the degradation of SOEC is a significant barrier to commercial viability. In this review paper, the typical degradation phenomena of SOEC are summarized, with great attention into the anodes/oxygen electrodes, including the commonly used and newly developed anode materials. Meanwhile, mechanistic investigations on the electrode/electrolyte interfaces are provided to unveil how the intrinsic factor, oxygen partial pressure $p_{O_2}$, and the electrochemical operation conditions, affect the interfacial stability of SOEC. At last, this paper also presents some emerging mitigation strategies to circumvent long-term degradation, which include novel infiltration method, development of new anode materials and engineering of the microstructure.

Key words: Solid oxide electrolysis cell, Degradation, Electrode/electrolyte interface, Mitigation, Strategy

Yi Wang, Wenyuan Li, Liang Ma, Wei Li, Xingbo Liu. Degradation of solid oxide electrolysis cells: Phenomena, mechanisms, and emerging mitigation strategies—A review[J]. J. Mater. Sci. Technol., 2020, 55: 35-55.

Figures/Tables 27

Fig. 1. [5] A typical schematic of SOEC and the reaction paths for CO2 and H2O electrolysis based on oxygen ion conducting electrolyte. Reproduced with permission from ref 5. Copyright 2017 Elsevier, Inc.

Fig. 2. [13] Thermodynamics of steam and carbon dioxide electrolysis. Both steam and CO2 electrolysis become increasingly endothermic with temperature increasing. Reproduced with permission from ref 13. Copyright 2007 Elsevier, Inc.

Fig. 3. [29,31] Photographs of two identical LSM/YSZ/LSM symmetric cells under operation or non-operation: (a) LSM anode delaminates from YSZ electrolyte after anodic operation for 100 h at 0.8 V, (b) the anode remains intact of the untested symmetric cell [31]. Reproduced with permission from ref [31]. Copyright 2012 Elsevier, Inc. SEM images of the cross-section of the LSM oxygen electrode /YSZ electrolyte interface (a) before and (b) after anodic polarization at 0.5 A/cm2 and 800 °C for 48 h [29]. Reproduced with permission from ref [29]. Copyright 2011 Elsevier, Inc.

Fig. 4. [29] (a) The YSZ electrolyte surface in contact with the LSM electrode before the polarization. LSM coating was removed by HCL treatment. (b) and (c) show the YSZ surface after the anodic current passage at 0.5 A/cm2 and 800 °C for 48 h before and after acid treatment, respectively. (d)-(i) show schematic illustrations of the microstructural change of the LSM oxygen electrode/YSZ electrolyte interface under SOEC operation conditions. Reproduced with permission from ref [29]. Copyright 2011 Elsevier, Inc.

Fig. 5. [31] SEM images of YSZ electrolyte surfaces of LSM-YSZ-LSM symmetry cells after HCl acid treatment to remove the LSM electrodes, each of which was tested at different voltages at 840 °C for 100 h: (a) OCV, (b) 0.3 V, (c) 0.5 V, (d) 0.8 V. Proposed mechanism (e)-(h): (e) YSZ ridge forms at triple-phase boundary due to surface cation migration [132,133] when LSM electrode is as-sintered on YSZ surface, (f) oxygen ions diffuses through YSZ bulk and grain boundaries in the initial stage of voltage application, (g) $La_2 Zr_2 O_7$ forms at the anode-electrolyte interface and porosity forms in the electrolyte grain boundaries when the voltage continues, (h) porosity enhances in the electrolyte grain boundaries and $La_2 Zr_2 O_7$ particles form fully coverage on the YSZ electrolyte that intensively weakens the interface and causes delamination at the end of electrical testing. Reproduced with permission from ref 31. Copyright 2012 Elsevier, Inc.

Fig. 6. [30] SEM images of LSM-YSZ interface after 1.5 A/cm2 current passage for 120 h at 750 °C in air (a) the cathode (b) the anode. (c) The delamination of anode electrode from the electrolyte. (d) Interface area between LSM/YSZ electrode and YSZ electrolyte. Reproduced with permission from ref [30]. Copyright 2013 Elsevier, Inc.

Fig. 7. [44]X-ray fluorescence maps of (a) Mn, (b) Co and (c) Cr abundance in the oxygen electrode of a 1000-h cell. Lighter shading corresponds to a greater concentration of the element. The sealed edges were along the top and bottom edges of the cell. (d) Cr in the 1000-h oxygen electrode. Darker shading corresponds to more of the element near the surface and lighter shading corresponds to greater buried element abundance. Oxygen flowed over the electrode from right to left. Reproduced with permission from ref [46]. Copyright 2009 Elsevier, Inc.

Fig. 8. [55] (a) SEM micrograph top view of the air electrode. (b) Cross-sectional SEM micrograph of air electrode near “air out”. Large particles of SrCrO4 were formed on top of the air electrode and needles of SrCrO4 in the air electrode. Reproduced with permission from ref [58] under the license of Creative Commons. Copyright 2018.

Fig. 9. [24] SEM-EDX images taken at YSZ-GDC interface (a) for the pristine cell, (b) for Cell operated in SOFC mode and (c, d) for Cell operated in SOEC mode. In (a), the Co-rich particles embedded in the bulk of the GDC network are highlighted by light blue arrows. In (c, d), the Sr-rich and Co-rich phases are highlighted on the SEM image with red and blue arrows respectively. Reproduced with permission from ref [24]. Copyright 2017 Elsevier, Inc.

Fig. 10. [59] SEM-EDS cross-sectional mapping of LSCF/GDC/YSZ (a) under OCV, (b) STEM-EDS mapping of the LSCF/GDC interface after OCV showing the formation of SrZrO3 at the O2/LSCF/GDC triple-phase boundary and extensively along the LSCF/GDC interface. Reprinted with permission from J. Electrochem. Soc., 164, F259 (2017). Copyright 2017, The Electrochemical Society.

Fig. 11. [58] Schematic representation of the Sr and Zr diffusion in LSCF/GDC/YSZ triplets with GDC polycrystalline barrier layer, (100) and (111)-oriented epitaxial GDC barrier layers. Sr moves faster in polycrystalline GDC than that in single crystal GDC, because Sr can transport fast by grain boundary diffusion. Zr moves faster in (100) than (111)-oriented GDC, due to the weak atomic bonds of GDC(100) attributed to less packing density than (111). Reproduced with permission from ref [59]. Copyright 2018 Elsevier, Inc.

Fig. 12. [53] Schematic of the mechanism for the activation and delamination of LSCF air electrode (a) Freshly prepared sample; (b) Sample after 0.5 h high-current electrolysis; (c) Sample during the high-current electrolysis test; (d) Sample after 12 h electrolysis test; (e) Sample after 24 h electrolysis test. Reproduced with permission from ref [56]. Copyright 2018 Elsevier, Inc.

Fig. 13. [76] SEM images of (a) fresh GBCO, (b) after polarization at 300 mA/cm2, and (c) 600 mA/cm2. (d)-(f) The corresponding particle size distribution of surface precipitates for SEM images of (a)-(c). Reproduced with permission from ref [77]. Copyright 2018 Elsevier, Inc.

Fig. 14. [51] Images of fracture surfaces of the electrolyte layer. (a) Area of inter- and intragranular fracture, (b) same region in back-scattering mode showing more clearly horizontally structured pores (arrows) over the entire electrolyte layer and (c) at the GDC/YSZ interface, (d) highly enlarged YSZ grain surface with fractured grain boundary. Reproduced with permission from ref [54]. Copyright 2013 Elsevier, Inc.

Fig. 15. [28] (a) TEM micrograph of YSZ grain boundary near the oxygen electrode. Inset: Higher magnification image of the grain boundary. (b) EDXS across the grain boundary as marked in (a). Reprinted with permission from J. Electrochem. Soc., 157, B1209 (2010). Copyright 2010, The Electrochemical Society.

Fig. 16. [49] Electron probe micro analysis (EPMA) results of O, Ni, Y and Zr in the dense electrolyte YSZ (lower part) and the porous cathode (upper part) of (a) a non-operated cell and (b) an operated electrolysis cell under 1 A/cm2 and 775-782 ℃ for 9000 h. Reproduced with permission from ref [52]. Copyright 2015 Elsevier, Inc.

Fig. 17. [98] Morphology of (a and b) Ni cathode (c) NiFe91 (weight ratio 9:1) cathode for the cells after CO2 electrolysis operation at 800 °C. (d) Raman spectra of the surface of Ni and NiFe91 cathodes. Reproduced with permission from ref [99]. Copyright 2013 Royal Society of Chemistry.

Fig. 18. [102] A schematic illustration of the definition of local $p_{O_2}$ within a membrane of a MIEC. The thickness of the membrane is l. $μ_{O_2}$I is the $μ_{O_2}$ in the gas phase of electrode I; $μ_{O_2}$II is the $μ_{O_2}$ in the gas phase of electrode II. φI and φII are the reduced (negative) electrochemical potential of I and II, respectively. Local equilibrium in the system implied that 12$μ_{O_2}$+2μ?e=μ?O2- is valid everywhere. This means if a pore of volume Vpore exists at some position in the conductor, the $p_{O_2}$ in the pore would correspond to the local $μ_{O_2}$. If the pore volume approaches to zero, the number of moles of oxygen in the pore, nO2, approaches zero as well, assuming ideal gas law. Therefore, though no actual pore exists, the concept of $p_{O_2}$ and $μ_{O_2}$ however continue to exist. Yet the local $p_{O_2}$ is well defined. Reproduced with permission from ref [103]. Copyright 2005 Elsevier, Inc.

Fig. 19. [102] Schematic variations of $μ_{O_2}$, μ?O2- and φ across the electrolyte and interfaces for (a) SOFC and (b) SOEC in certain conditions. Reproduced with permission from ref [103]. Copyright 2005 Elsevier, Inc.

Table 1 [107] Estimation of $p_{O_2}$ within the electrolyte just near the oxygen electrode/electrolyte interface, $p_{O_2}$a, for various values of cell area specific electronic resistance, Re. The applied voltage is Ea = 1.5 V. reel is the electronic resistance of electrolyte. Itotal is the total external current density. Reproduced with permission from ref [108]. Copyright 2010 Elsevier, Inc.

reel (Ω cm²)	Re (Ω cm²)	Ri (Ω cm²)	Ii (A/cm²)	Ie (A/cm²)	Itotal (A/cm²)	$p_{O_2}$a (atm)	Likelihood of delamination
0	1.5	0.39	1.117	1.0	2.117	10^-17	No delamination
1	2.5	0.39	1.117	0.6	1.717	10^-4	No delamination
5	6.5	0.39	1.117	0.23	1.347	1.44	No delamination
8	9.5	0.39	1.117	0.158	1.317	104.6	Delamination highly likely
20	21.5	0.39	1.117	0.07	1.187	10⁴	Delamination imminent

Fig. 20. [110] π-? (this is the electrode potential based on authors’ definition) and equilibrium oxygen pressure in a cell operating in SOEC mode compared to OCV condition at 1000 °C. Reprinted with permission from ECS Transactions., 13, 259 (2008). Copyright 2008, The Electrochemical Society.

Fig. 21. [112] (a) Schematics of the formation of peroxy O-O bonds (precursors of O2 molecules) at the (001) surface of cubic ZrO2 related to substitutional Mn impurities in the subsurface region. Oxygen atoms are shown in red, Zr - as small light blue balls, Mn - in purple; (b) Equilibrium pressure of the O2 gas above a free ZrO2 surface at T =800 °C as a function of O2 formation energy corresponding to different subsurface substitutional defects. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) Reproduced with permission from ref [113]. Copyright 2012 Elsevier, Inc.

Fig. 23. [72] (a) The I-V curves of the SOEC anode and SOFC cathode layers of the La2NiO4+δ || GDC || La2NiO4+δ symmetric cell at 800 °C in air. (b) Degradation-induced changes in area specific resistance (ASR) of the SOEC anode and SOFC cathode sides, as determined by three-electrode impedance measurements at 800 °C. Rs denotes the series resistance (mainly IR-drop across the electrolyte) while Rp refers to the polarization resistance of the electrodes. Reproduced with permission from ref [73]. Copyright 2017 Elsevier, Inc.

Fig. 24. [128] Schematic illustration of electrodes (a) traditional sponge-like LSC electrode (b) Honeycomb LSC/YSZ electrode. Reproduced with permission from ref [108]. Copyright 2018 John Wiley and Sons.

Fig. 25. [128] HE-LSC was measured in three-electrode mode at 1.5 A/cm2 for 4 h and then at 2.0 A A/cm2 for 6 h at 800 °C, while TE-LSC measured in three-electrode mode at 0.6 A/cm2 for 1 h and then at 1.2 A/cm2 for 0.67 h at 800 °C. Reproduced with permission from ref [108]. Copyright 2018 John Wiley and Sons.

Fig. 26. [129] (a) The stability tests of LSM electrode with or without incorporation of porous YSZ layer: LSM-0 G represents the traditional LSM electrode without porous YSZ; LSM-10 G and LSM-20 G are the cells with porous YSZ, but using different amounts of graphite to produce the porosity for the porous YSZ layer. (b) A possible illustration of the delamination of traditional LSM. (c) A possible mechanism of the ability of LSM-10 G and LSM-20 G to prevent delamination. Reproduced with permission from ref [130]. Copyright 2017 Elsevier, Inc.

References 122

[1]	Y. Wang, T. Liu, L. Lei, F. Chen, Fuel. Process. Technol. 161 (2017) 248-258.
[2]	M. Ni, M. Leung, D. Leung, Int. J. Hydrogen Energy 33 (2008) 2337-2354.
[3]	W. Li, N. Jiang, B. Hu, X. Liu, F. Song, G. Han, T.J. Jordan, T.B. Hanson, T.L. Liu, Y. Sun, Chem. 4 (2018) 637-649.
[4]	F. Song, W. Li, J. Yang, G. Han, P. Liao, Y. Sun, Nat. Commun. 9 (2018) 4531. DOI URL PMID
[5]	X. Zhang, Y. Song, G. Wang, X. Bao, J. Energy Chem. 26 (2017) 839-853.
[6]	Y. Zheng, J. Wang, B. Yu, W. Zhang, J. Chen, J. Qiao, J. Zhang, Chem. Soc. Rev. 46 (2017) 1427-1463. DOI URL PMID
[7]	W. Li, X. Gao, D. Xiong, F. Xia, J. Liu, W.-G. Song, J. Xu, S.M. Thalluri, M.F. Cerqueira, X. Fu, L. Liu, Chem. Sci. 8 (2017) 2952-2958. DOI URL
[8]	W. Li, X. Gao, X. Wang, D. Xiong, P.-P. Huang, W.-G. Song, X. Bao, L. Liu, J. Power Sources 330 (2016) 156-166.
[9]	S.J. Kim, G.M. Choi, Solid State Ion. 262 (2014) 303-306. DOI URL
[10]	T. Ogier, J.M. Bassat, F. Mauvy, S. Fourcade, J.C. Grenier, K. Couturier, M. Petitjean, J. Mougin, Fuel Cells Weinh. (Weinh) 13 (2013) 536-541.
[11]	J. Schefold, A. Brisse, H. Poepke, Int. J. Hydrogen Energy 42 (2017) 13415-13426.
[12]	Y. Yan, Q. Fang, L. Blum, W. Lehnert, Electrochim. Acta 258 (2017) 1254-1261.
[13]	S.H. Jensen, P.H. Larsen, M. Mogensen, Int. J. Hydrogen Energy 32 (2007) 3253-3257.
[14]	G. Tao, K.R. Sridhar, C.L. Chan, Solid State Ion. 175 (2004) 621-624.
[15]	G. Tao, K.R. Sridhar, C.L. Chan, Solid State Ion. 175 (2004) 615-619.
[16]	K. Sridhar, B.T. Vaniman, Solid State Ion. 93 (1997) 321-328.
[17]	T. Yang, J. Liu, Y. Yu, Y.-L. Lee, H. Finklea, X. Liu, H.W. Abernathy, G.A. Hackett, PCCP 19 (2017) 30464-30472. DOI URL PMID
[18]	T. Yang, H. Sezer, I. Celik, H. Finklea, K. Gerdes, Int. J. Electrochem. Sci. 12 (2017) 6801-6828.
[19]	D.T. Whipple, P.J.A. Kenis, J. Phys.Chem. Lett. 1 (2010) 3451-3458.
[20]	C. Lamy, Int. J. Hydrogen Energy 41 (2016) 15415-15425.
[21]	X. Zhang, J.E. O’Brien, R.C. O’Brien, G.K. Housley, J. Power Sources 242 (2013) 566-574.
[22]	X. Zhang, J.E. O’Brien, R.C. O’Brien, J.J. Hartvigsen, G. Tao, G.K. Housley, Int. J.Hydrogen Energy 38 (2013) 20-28.
[23]	J. Schefold, A. Brisse, F. Tietz, J. Electrochem. Soc. 159 (2011) A137-A144.
[24]	J. Laurencin, M. Hubert, D.F. Sanchez, S. Pylypko, M. Morales, A. Morata, B. Morel, D. Montinaro, F. Lefebvre-Joud, E. Siebert, Electrochim. Acta 241 (2017) 459-476.
[25]	S.P. Jiang, Asia-Pac. J.Chem. Eng. 11 (2016) 386-391.
[26]	K. Chen, S.P. Jiang, J. Electrochem. Soc. 163 (2016) F3070-F3083.
[27]	P. Mocc oteguy, A. Brisse, Int. J. Hydrogen Energy 38 (2013) 15887-15902.
[28]	R. Knibbe, M.L. Traulsen, A. Hauch, S.D. Ebbesen, M. Mogensen, J. Electrochem. Soc. 157 (2010) B1209.
[29]	K. Chen, S.P. Jiang, Int. J. Hydrogen Energy 36 (2011) 10541-10549.
[30]	J. Kim, H.-I. Ji, H.P. Dasari, D. Shin, H. Song, J.-H. Lee, B.-K. Kim, H.-J. Je, H.-W. Lee, K.J. Yoon, Int. J. Hydrogen Energy 38 (2013) 1225-1235.
[31]	M. Keane, M.K. Mahapatra, A. Verma, P. Singh, Int. J. Hydrogen Energy 37 (2012) 16776-16785.
[32]	J. Hwang, R.R. Rao, L. Giordano, Y. Katayama, Y. Yu, Y. Shao-Horn, Science 358 (2017) 751-756. DOI URL PMID
[33]	J. Stevenson, T. Armstrong, R. Carneim, L.R. Pederson, W. Weber, J. Electrochem. Soc. 143 (1996) 2722-2729. DOI URL
[34]	C. Graves, S.D. Ebbesen, M. Mogensen, Solid State Ion. 192 (2011) 398-403. DOI URL
[35]	R. Petri, E. Tang, T. Wood, C. Brown, M. Casteel, M. Pastula, M. Richards, 2016 Annual Progress Report II B 5, 2017, pp. 1-3.
[36]	A. Momma, T. Kato, Y. Kaga, S. Nagata, J. Ceram. Soc. Jpn. 105 (1997) 369-373. DOI URL
[37]	M. Chen, Understanding the Thermodynamics at the LaMnO3-YSZ Interface in SOFC, 2005.
[38]	S.P. Jiang, J. Solid State Electrochem. 11 (2007) 93-102.
[39]	S. Jiang, W. Wang, Electrochem. Solid-State Lett. 8 (2005) A115-A118.
[40]	J. Mizusaki, Y. Yonemura, H. Kamata, K. Ohyama, N. Mori, H. Takai, H. Tagawa, M. Dokiya, K. Naraya, T. Sasamoto, H. Inaba, T. Hashimoto, Solid State Ion. 132 (2000) 167-180.
[41]	D. Monceau, M. Filal, M. Tebtoub, C. Petot, G. Petot-Ervas, Solid State Ion. 73 (1994) 221-225.
[42]	M. Martin, Solid State Ion. 136-137 (2000) 331-337.
[43]	K. Chen, J. Hyodo, A. Dodd, N. Ai, T. Ishihara, L. Jian, S.P. Jiang, Faraday Discuss. 182 (2015) 457-476.
[44]	J.R. Mawdsley, J. David Carter, A. Jeremy Kropf, B. Yildiz, V.A. Maroni, Int. J. Hydrogen Energy 34 (2009) 4198-4207.
[45]	J. Bi, S. Yang, S. Zhong, J.-Q. Wang, C. Fan, X. Chen, Y. Liu, J. Power Sources 363 (2017) 470-479.
[46]	K. Chen, J. Hyodo, N. Ai, T. Ishihara, S.P. Jiang, Int. J. Hydrogen Energy 41 (2016) 1419-1431.
[47]	C.C. Wang, K. Chen, T. Jiang, Y. Yang, Y. Song, H. Meng, S.P. Jiang, B. Lin, Electrochim. Acta 269 (2018) 188-195.
[48]	J. Schefold, A. Brisse, H. Poepke, Electrochim. Acta 179 (2015) 161-168.
[49]	D. The, S. Grieshammer, M. Schroeder, M. Martin, M. Al Daroukh, F. Tietz, J. Schefold, A. Brisse, J. Power Sources 275 (2015) 901-911.
[50]	M. Al Daroukh, F. Tietz, D. Sebold, H.P. Buchkremer, Ionics 21 (2014) 1039-1043.
[51]	F. Tietz, D. Sebold, A. Brisse, J. Schefold, J. Power Sources 223 (2013) 129-135.
[52]	J.C. De Vero, K. Develos-Bagarinao, H. Kishimoto, T. Ishiyama, K. Yamaji, T. Horita, H. Yokokawa, J. Electrochem. Soc. 163 (2016) F1463-F1470.
[53]	Z. Pan, Q. Liu, M. Ni, R. Lyu, P. Li, S.H. Chan, Int. J. Hydrogen Energy 43 (2018) 5437-5450.
[54]	A. Mahmoud, M. Al Daroukh, M. Lipinska-Chwalek, M. Luysberg, F. Tietz, R.P. Hermann, Solid State Ion. 312 (2017) 38-43.
[55]	C.E. Frey, Q. Fang, D. Sebold, L. Blum, N.H. Menzler, J. Electrochem. Soc. 165 (2018) F357-F364. DOI URL
[56]	N. Ai, S. He, N. Li, Q. Zhang, W.D.A. Rickard, K. Chen, T. Zhang, S.P. Jiang, J. Power Sources 384 (2018) 125-135. DOI URL
[57]	Z. He, L. Zhang, S. He, N. Ai, K. Chen, Y. Shao, S.P. Jiang, J. Power Sources 404 (2018) 73-80.
[58]	J.C. De Vero, K. Develos-Bagarinao, H. Matsuda, H. Kishimoto, T. Ishiyama, K. Yamaji, T. Horita, H. Yokokawa, Solid State Ion. 314 (2018) 165-171.
[59]	J.C. De Vero, K. Develos-Bagarinao, H. Kishimoto, T. Ishiyama, K. Yamaji, T. Horita, H. Yokokawa, J. Electrochem. Soc. 164 (2017) F259-F269.
[60]	B. Wei, K. Chen, L. Zhao, Z. Lü, S. Ping Jiang, Phys. Chem. Chem. Phys. 17 (2015) 1601-1609. DOI URL PMID
[61]	T. Kushi, Int. J. Hydrogen Energy 42 (2017) 9396-9405.
[62]	P. Kim-Lohsoontorn, D.J.L. Brett, N. Laosiripojana, Y.M. Kim, J.M. Bae, Int. J.Hydrogen Energy 35 (2010) 3958-3966.
[63]	C. Ferchaud, J.C. Grenier, Y. Zhang-Steenwinkel, M.M.A. van Tuel, F.P.F. vanBerkel, J.M. Bassat, J. Power Sources 196 (2011) 1872-1879.
[64]	J.S.A. Carneiro, R.A. Brocca, M.L.R.S. Lucena, E. Nikolla, Appl. Catal. B 200 (2017) 106-113.
[65]	R.J. Woolley, S.J. Skinner, Solid State Ion. 255 (2014) 1-5.
[66]	A. Montenegro-Hernández, J. Vega-Castillo, L. Mogni, A. Caneiro, Int. J.Hydrogen Energy 36 (2011) 15704-15714.
[67]	J.D. Jorgensen, B. Dabrowski, S. Pei, D.R. Richards, D.G. Hinks, Phys. Rev. B 40 (1989) 2187-2199.
[68]	A. Flura, S. Dru, C. Nicollet, V. Vibhu, S. Fourcade, E. Lebraud, A. Rougier, J.M. Bassat, J.C. Grenier, J. Solid State Chem. 228 (2015) 189-198.
[69]	S.J. Kim, K.J. Kim, A.M. Dayaghi, G.M. Choi, Int. J. Hydrogen Energy 41 (2016) 14498-14506.
[70]	X. Tong, F. Zhou, S. Yang, S. Zhong, M. Wei, Y. Liu, Ceram. Int. 43 (2017) 10927-10933.
[71]	F. Chauveau, J. Mougin, F. Mauvy, J.-M. Bassat, J.-C. Grenier, Int. J. Hydrogen Energy 36 (2011) 7785-7790.
[72]	A. Egger, N. Schrödl, C. Gspan, W. Sitte, Solid State Ion. 299 (2017) 18-25.
[73]	G. Yang, C. Su, R. Ran, M.O. Tade, Z. Shao, Energy Fuels 28 (2013) 356-362.
[74]	T. Ogier, F. Mauvy, J.-M. Bassat, J. Laurencin, J. Mougin, J.-C. Grenier, Int. J.Hydrogen Energy 40 (2015) 15885-15892.
[75]	Y. Wang, T. Liu, S. Fang, F. Chen, J. Power Sources 305 (2016) 240-248.
[76]	B. Wei, J. Feng, L. Zhu, Z. Wang, X. Zhu, X. Huang, Y. Zhang, L. Xu, H. Gao, Z. Lü, J. Eur. Ceram. Soc. 38 (2018) 2396-2403.
[77]	M.A. Laguna-Bercero, J. Power Sources 203 (2012) 4-16.
[78]	K. Eguchi, T. Hatagishi, H. Arai, Solid State Ion. 86 (1996) 1245-1249.
[79]	S. Elangovan, J.J. Hartvigsen, L.J. Frost, Int. J. Appl. Ceram. Technol. 4 (2007) 109-118.
[80]	K. Huang, M. Feng, J.B. Goodenough, C. Milliken, J. Electrochem. Soc. 144 (1997) 3620-3624.
[81]	N. Maffei, G. de Silveira, Solid State Ion. 159 (2003) 209-216.
[82]	X. Zhang, S. Ohara, R. Maric, H. Okawa, T. Fukui, H. Yoshida, T. Inagaki, K. Miura, Solid State Ion. 133 (2000) 153-160.
[83]	S.D. Ebbesen, S.H. Jensen, A. Hauch, M.B. Mogensen, Chem. Rev. 114 (2014) 10697-10734. DOI URL PMID
[84]	M.A. Laguna-Bercero, R. Campana, A. Larrea, J.A. Kilner, V.M. Orera, J. PowerSources 196 (2011) 8942-8947.
[85]	A. Hauch, S.D. Ebbesen, S.H. Jensen, M. Mogensen, J. Electrochem. Soc. 155 (2008) B1184.
[86]	D.A. Osinkin, B.L. Kuzin, N.M. Bogdanovich, Russ. J. Electrochem. 46 (2010) 41-48.
[87]	Z. Jiao, N. Takagi, N. Shikazono, N. Kasagi, J. Power Sources 196 (2011) 1019-1029.
[88]	L. Holzer, B. Iwanschitz, T. Hocker, B. Münch, M. Prestat, D. Wiedenmann, U. Vogt, P. Holtappels, J. Sfeir, A. Mai, T. Graule, J. Power Sources 196 (2011) 1279-1294.
[89]	S.-D. Kim, D.-W. Seo, A.K. Dorai, S.-K. Woo, Int. J. Hydrogen Energy 38 (2013) 6569-6576.
[90]	T. Matsui, R. Kishida, J.-Y. Kim, H. Muroyama, K. Eguchi, J. Electrochem. Soc. 157 (2010) B776-B781. DOI URL
[91]	A. Hauch, Sr.Hj. Jensen, Jr.B. Bilde-SoD/rensen, M. Mogensen, J. Electrochem.Soc. 154 (2007) A619.
[92]	C. Chatzichristodoulou, M. Chen, P.V. Hendriksen, T. Jacobsen, M.B. Mogensen, Electrochim. Acta 189 (2016) 265-282. DOI URL
[93]	M. Gong, X. Liu, J. Trembly, C. Johnson, J. Power Sources 168 (2007) 289-298.
[94]	S.D. Ebbesen, M. Mogensen, Electrochem. Solid-State Lett. 13 (2010) B106-B108. DOI URL
[95]	S.D. Ebbesen, M. Mogensen, J. Power Sources 193 (2009) 349-358.
[96]	S.D. Ebbesen, C. Graves, A. Hauch, Sr.H. Jensen, M. Mogensen, J. Electrochem.Soc. 157 (2010) B1419.
[97]	S. Wang, H. Tsuruta, M. Asanuma, T. Ishihara, Adv. Energy Mater. 5 (2015), 1401003.
[98]	S. Wang, A. Inoishi, J.-e. Hong, Y.-w. Ju, H. Hagiwara, S. Ida, T. Ishihara, J. Mater. Chem. A Mater. Energy Sustain. 1 (2013) 12455.
[99]	S. Liu, Q. Liu, J.-L. Luo, ACS Catal. 6 (2016) 6219-6228.
[100]	Y. Zhou, Z. Zhou, Y. Song, X. Zhang, F. Guan, H. Lv, Q. Liu, S. Miao, G. Wang, X. Bao, Nano Energy 50 (2018) 43-51.
[101]	D. Kondepudi, I. Prigogine, John Wiley & Sons, 2014.
[102]	A.V. Virkar, J. Power Sources 147 (2005) 8-31.
[103]	A.V. Virkar, J. Electrochem. Soc. 138 (1991) 1481.
[104]	H.-T. Lim, A.V. Virkar, J. Power Sources 192 (2009) 267-278.
[105]	H.-T. Lim, A.V. Virkar, J. Power Sources 180 (2008) 92-102.
[106]	A.V. Virkar, J. Power Sources 172 (2007) 713-724.
[107]	A.V. Virkar, Int. J. Hydrogen Energy 35 (2010) 9527-9543.
[108]	A.V. Virkar, J. Nachlas, A.V. Joshi, J. Diamond, J. Am. Ceram. Soc. 73 (1990) 3382-3390.
[109]	H.-T. Lim, A.V. Virkar, J. Power Sources 185 (2008) 790-800.
[110]	T. Jacobsen, M. Mogensen, ECS Trans. 13 (2008) 259-273.
[111]	A. Mineshige, T. Taji, Y. Muroi, M. Kobune, S. Fujii, N. Nishi, M. Inaba, Z. Ogumi, Solid State Ion. 135 (2000) 481-485.
[112]	S.N. Rashkeev, M.V. Glazoff, Int. J. Hydrogen Energy 37 (2012) 1280-1291.
[113]	T. Yang, J. Liu, H. Finklea, S. Lee, W.K. Epting, R. Mahbub, T. Hsu, P.A. Salvador, H.W. Abernathy, G.A. Hackett, Int. J. Hydrogen Energy 43 (2018) 15445-15456.
[114]	H. Sezer, I.B. Celik, T. Yang, ECS Trans. 68 (2015) 2515-2525.
[115]	J. Liu, Y. Yu, T. Yang, O. Ozmen, H. Finklea, E.M. Sabolsky, H. Abernathy, P.R. Ohodnicki, G.A. Hackett, ECS Trans. 78 (2017) 689-699.
[116]	T. Yang, I.B. Celik, H. Sezer, S. Lee, K. Gerdes, ECS Trans. 66 (2015) 137-142.
[117]	T. Yang, J. Liu, H.O. Finklea, H. Abernathy, G.A. Hackett, ECS Trans. 78 (2017) 2699-2709.
[118]	T. Yang, H. Sezer, I.B. Celik, H.O. Finklea, K. Gerdes, ECS Trans. 68 (2015) 2397-2411.
[119]	K. Chen, N. Ai, S.P. Jiang, Electrochem. Commun. 19 (2012) 119-122.
[120]	K. Chen, N. Ai, S.P. Jiang, Int. J. Hydrogen Energy 39 (2014) 10349-10358.
[121]	Y. Song, X. Zhang, Y. Zhou, Q. Jiang, F. Guan, H. Lv, G. Wang, X. Bao, Energy Storage Mater. 13 (2018) 207-214.
[122]	H. Zheng, Y. Tian, L. Zhang, B. Chi, J. Pu, L. Jian, J. Power Sources 383 (2018) 93-101.