Materials development for intermediate temperature solid oxide electrochemical devices Ainara Aguadero a,b , Lydia Fawcett a , , Samuel Taub a , Russell Woolley a , Kuan- Ting Wu a , Ning Xu a , John A. Kilner a , Stephen J. Skinner a* a Department of Materials, Imperial College London, Exhibition Road, London, United Kingdom SW7 2AZ b Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco Madrid, Spain 28049 Abstract One of the major challenges in developing electrochemical devices for energy generation has been the identification and development of materials with outstanding performance at reduced (intermediate) temperatures (500- 700 C), increasing the durability and lowering the cost of the device. A solid state electrochemical cell is in outline a simple device consisting of three components: anode, electrolyte and cathode. The function of each component is critical to cell performance, and as interest in fuel cells and electrolysers has gathered pace many materials have been evaluated as functional components of these cells. Typically the requirement for new materials development has been the drive to lower operation temperature, overcoming sluggish reaction kinetics in existing materials. Novel materials for the functional components of both electrolysers and fuel cells are introduced, with emphasis placed on the air electrode and electrolyte, with the potential of new classes of materials discussed, including layered materials, defect fluorites and tetrahedrally coordinated phases. Further, the opportunity presented by thin film deposition to characterize anisotropic transport in materials and develop devices based on thin films is discussed.
68
Embed
spiral.imperial.ac.ukspiral.imperial.ac.uk/bitstream/10044/1/12707/2/J Mater... · Web viewMaterials development for intermediate temperature solid oxide electrochemical devices
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Materials development for intermediate temperature solid oxide electrochemical devices
Ainara Aguaderoa,b, Lydia Fawcetta, , Samuel Tauba, Russell Woolleya, Kuan-Ting Wua, Ning Xua, John A.
Kilnera, Stephen J. Skinnera*
aDepartment of Materials, Imperial College London, Exhibition Road, London, United Kingdom SW7 2AZ
b Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco Madrid, Spain 28049
Abstract
One of the major challenges in developing electrochemical devices for energy generation has been the
identification and development of materials with outstanding performance at reduced (intermediate)
temperatures (500-700 C), increasing the durability and lowering the cost of the device. A solid state
electrochemical cell is in outline a simple device consisting of three components: anode, electrolyte and cathode.
The function of each component is critical to cell performance, and as interest in fuel cells and electrolysers has
gathered pace many materials have been evaluated as functional components of these cells. Typically the
requirement for new materials development has been the drive to lower operation temperature, overcoming
sluggish reaction kinetics in existing materials. Novel materials for the functional components of both
electrolysers and fuel cells are introduced, with emphasis placed on the air electrode and electrolyte, with the
potential of new classes of materials discussed, including layered materials, defect fluorites and tetrahedrally
coordinated phases. Further, the opportunity presented by thin film deposition to characterize anisotropic
transport in materials and develop devices based on thin films is discussed.
The inspiration for SOEC (Figure 1) anode and cathode materials often comes from successful solid oxide fuel
cell (SOFC) cathode and anode materials, respectively. However the inlet atmosphere of a SOEC cathode
contains much more steam than the outlet of a SOFC anode and H2 is required in the feed gas in order to prevent
the oxidation of the common SOEC cathode material Ni-YSZ to NiO. An SOEC anode produces oxygen which
can be directly collected or swept with air in order to minimise polarization. The atmospheres may have
consequences on the stability and durability of the electrode materials chosen [198] and so a fuel cell cannot
simply be reversed if efficient electrolysis cell is required. The studies performed in evaluating the potential for
SOFC components to be used in SOECs are analyzed in the next section.
4.1. SOEC hydrogen cathodes
For a SOEC system water is supplied to the porous negative cathode where it migrates to the electrolyte surface
and is dissociated into hydrogen and oxygen by an external supply of electrons. The hydrogen then travels back
to the cathode surface whilst the oxygen ions are transported through the solid electrolyte membrane to the
anode. Oxygen partial pressures at this electrode can be of the order of 10-12 – 10-16 bar [199]. The material must
therefore be porous to allow transport of the reactant gas to the reactant sites and allow hydrogen to migrate to
the electrode surface. As with fuel cell anodes, electrolysis cathodes tend to be a Ni-YSZ cermet, the metal
conducts electrons, and mixing it with an ionic conductor such as YSZ increases the triple phase boundary
points. However the gas inlet to a Ni-YSZ cathode must include ~5-10% mole fraction hydrogen in order to
prevent the oxidation of the material to NiO [200, 201] which is less conductive and could lead to mechanical
instability. Ideally a material that is not easily oxidised is desired. Eguchi et al [202] tested materials in both
fuel cell and electrolysis modes. The materials studied were hydrogen cathodes Ni-YSZ and Pt; electrolytes
(ZrO2)0.85(YO1.5)0.15 and (CeO2)0.8(SmO1.5)0.2 (YSZ and SDC respectively); and oxygen electrodes La0.6Sr0.4MnO3
and La0.6Sr0.4CoO3 (LSM and LSC respectively). It was found that the combination Ni-YSZ/YSZ/LSM was the
best combination for fuel cell use and Pt/YSZ/LSC was the worst. In electrolysis mode however, the reverse
was true. The low activity of Ni-YSZ in electrolysis mode is ascribed to Ni particles oxidised in the steam
concentration, forming a less active layer. It is also found that the nickel particles in a Ni/YSZ composite
coarsen in high steam atmospheres or partially evaporate [203]. Osada et al [204] tested the ionic conductor
(CeO2)0.8(SmO1.5)0.2 (CSO) with Ni as a cermet as an electrolysis cathode material in conjunction with an 0.5mm
thick ScSZ electrolyte and LSC anode. On both sides a thin (~ 1μm) CSO interlayer was deposited between the
electrolyte and electrode in order to reduce contact resistance and reduce reactions between LSC and electrolyte.
It was found that a loading of 17% vol. Ni-CSO was optimal for electrolysis use. Anymore and agglomeration
of Ni particles is more likely. It was noted that the use of a highly ionically conductive electrolyte improved the
performance of the cathode, but not the anode. The authors state that they achieved good performance of IR-free
cell voltage = 1.13 V at 0.50 A/cm2 at 900°C under the atmosphere of H2O + H2 (p[H2O] = 0.6 atm) and O2 (1
atm). However, it was conceded that at lower temperatures their cell performed worse than optimised Ni-YSZ
based cells from literature and so further research was required.
Marina et al [203] compared Ni-YSZ with a titanate/ceria negative electrode La0.35Sr0.65TiO3 - Ce0.5La0.5O2−δ in
both electrolysis and fuel cell modes. When operated in fuel cell mode with a feed gas of 50:50 H 2O:H2, the
materials displayed the same order of resistance, i.e. at 800oC at a constant polarization loss of 50 mV Ni-YSZ
had an area specific resistance of 0.26 Ω.cm2 whereas the composite was 0.29 Ω.cm2. However, under these
conditions, but in electrolysis mode the composite performed better, with the composite displaying area specific
resistance of 0.21 Ω.cm2 and Ni-YSZ 0.29 Ω.cm2. Varying pH2O had more of an effect on the materials in
electrolysis mode than in fuel cell mode. At a constant electrolysis polarization loss of 0.1 V at 800oC and
partial pressure of H2O varied from 0.5 – 0.9 atm, Ni-YSZ decreased from 0.56 – 0.4 Ω.cm 2 and the composite
decreased from 0.28 – 0.2 Ω.cm2.
Yang et al [201] tested the perovskite (La0.75Sr0.25)0.95Mn0.5Cr0.5O3 (LSCM) with YSZ and CGO as composite
electrolysis cathode materials. The electrolyte used was YSZ and the anode was an LSM/YSZ composite. It was
found that LSCM-CGO and LSCM-YSZ composites perform better than Ni-YSZ as electrolysis cathodes with
or without the presence of H2 in the feed gas and at all potentials. When the cathode feed gas is 3% steam/4%
H2/Ar the LSCM composites display polarisation resistances of the order of 1Ω.cm2 compared to around
10Ω.cm2 for the Ni-YSZ cathode although it is conceded that this is not representative of best literature Ni-YSZ
values. When the potential is more negative, at about -0.2 V for LSCM/YSZ and -0.4 V for LSCM/CGO in an
H2 free atmosphere, polarisation resistance drastically increases. At further polarization at around -1.7V
resistance decreases once again. A number of possible reasons for the diversion from ohmic behaviour are
suggested. A reduction of LSCM at around -0.3V is postulated, which can change the volume by 1%, decreasing
conductivity. When at further negative potentials it is hypothesised that the material may decompose into MnO
and a Ruddlesden-Popper phase thereby reducing resistivity, however this is not verified in the study.
There are contradictory studies which show that there is only small resistance difference between using the Ni-
YSZ in fuel cell or electrolysis mode [205, 206]. For example Laguna-Bercero et al [206] found comparable Ni-
YSZ polarization potentials of 0.40 Ω.cm2 and 0.29 Ω.cm2 when run in electrolysis (+0.61 V) and fuel cell (-
0.39 V) modes respectively. The reason for the disagreement in the literature is not explained. However it is
noted that the role of microstructure on electrochemical performance is not fully understood for the electrolysis
cathode.
4.2. Oxygen Anode
At an SOEC anode surface the electrochemically delivered oxygen ions are oxidised to become oxygen
molecules. As with the cathode a mixed ionic and electronic conducting material is required with a similar
thermal expansion coefficient as the electrolyte. Most commonly perovskites are used for SOEC anodes. A lot
of the work in finding suitable SOEC anodes has centred on testing known successful SOFC cathodes, for
example the perovskite Sr doped lanthanum manganite LaMnO3 is a popular SOFC cathode due to its high
electrical conductivity, stability and compatibility with common electrolytes [207]. Doping Sr2+ on the La3+ site
can improve conductivity as Mn4+ is increased, but has the disadvantage of increasing the thermal expansion
coefficient [208] and not being ionically conductive as well as electronically conductive [209]. There is also risk
of MnOx migrating from the LSM phase into the YSZ, allowing the La2O3 or SrO to react with YSZ to form less
conductive La2Zr2O7 or SrZrO3 [199, 210, 211, 212]. Over doping the LSM with MnOx by just a small %
ensures there is no free La2O3 or SrO to react with the YSZ [199]. Laguna-Bercero et al [213] detected evidence
of La2Zr2O7 when La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) or La0.8Sr0.2MnO3-δ - YSZ (LSM-YSZ) composites were used as
an electrode in contact with 1% Ce substituted Scandia Stabilised Zirconia (10Sc1CeSZ) but found it to have no
adverse effect on performance giving ASR values 0.93 Ω.cm2 for the LSM cell and 0.79 Ω.cm2 for the LSCF
cell at 800oC under electrolysis mode with 70%H2O supplied to the Ni-YSZ electrode. It should be noted that
these materials performed better in fuel cell mode under the same conditions. It was also found that the LSM-
YSZ composite on ScCeSZ showed degradation after use, this is attributed to a distortion to rhombohedral β-
Sc2Zr7O17 phase.
Wang et al [211] eliminated the formation of the insulating layers of these materials by synthesising composites
of YSZ with La0.8Sr0.2CoO3 (LSCo), La0.8Sr0.2FeO3 (LSF) and La0.8Sr0.2MnO3 (LSM) respectively. It was found
that LSM-YSZ is a less than ideal electrode material, despite an initial improvement of impedance when run in
fuel cell mode as performance decreased during electrolysis mode. The LSC-YSZ and LSF-YSZ composites
showed good initial performance with no need for a preliminary cathode polarization step. The LSC-YSZ anode
showed the best initial performance of the three, but was noted to deactivate after time in electrolysis mode. The
LSF-YSZ anode on the other hand was proven to be stable during electrolysis over a period of 100 hours. [211]
Directly after fuel cell polarization (570 mAcm-2) the LSM-YSZ anode displayed, at OCV, a total cell
impedance of 1.8 Ω.cm2 but after 180 minutes in electrolysis mode (285 mAcm -2) the electrode impedance had
increased to about 4 Ω.cm2. It is explained that under oxidising conditions LSM distributes forming an LSM
film preventing the diffusion of oxygen ions. This is temporarily reversed if run in fuel cell mode.
Conversely Marina et al [203] found LSM to be a reversible oxygen material when they studied La0.8Sr0.2FeO3-δ
(LSF), La0.7Sr0.3Cu0.1Fe0.9O3-δ (LSCuF), La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF), and La0.8Sr0.2MnO3−δ (LSM) as oxygen
electrodes in reversible cells. In all cases the materials performed better in fuel cell mode than in electrolysis
mode. Of these four materials LSF and LSM showed the most reversibility, having similar overpotentials in fuel
cell and electrolysis modes. LSCuF and LSCF were notably better in fuel cell mode than electrolysis.
Kuharuangrong [208] tested the effect of doping LSM with Ni on the Mn site. It is explained that increasing the
Sr2+ content in LSM increases electrical conductivity by increasing the concentration of Mn4+, however the
compromise is an increase in TEC which results in a mismatch with other common materials. It was found that
doping and increasing the amount of Ni2+ on the Mn side decreased the Mn3+ concentration, decreasing electrical
conductivity at 900oC from 107 Scm-1 for undoped LSM to 48 Scm-1 for LSM doped with 30- mole% Ni.
Yu et al [214] investigated a Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) oxygen anode with a YSZ electrolyte and Ni-YSZ
hydrogen cathode, finding that electrode ASR values of 0.66 Ω.cm2 at 750 oC, 0.27 Ω.cm2 at 800oC, and 0.077
Ω.cm2 at 850 oC were produced. Yu et al. claim this material performs better than common SOEC anode
materials, e.g. LSC, LSF and LSM, but the ASRs reported are similar to those of other authors discussed above.
However when operated in electrolysis mode the BSCF/YSZ/Ni-YSZ cell H2 output, 147.2 mL cm−2 h−1 of
hydrogen, was, almost three times the amount produced by a more conventional LSM/YSZ/Ni-YSZ cell which
produced just 49.8 mL cm−2 h−1.
Since Laguna-Bercero et al [206] suggest that La2NiO4+δ (LNO) type materials should be studied for use as
oxygen electrodes the lanthanide nickelates, the family of composition Ln2NiO4 (Ln = La, Nd, Pr) are
increasingly studied as oxygen electrode materials. This is mostly due to the high oxygen transport values and
wide range of oxygen stoichiometries that are possible as a function of the oxygen partial pressure [215]. LNO
is able to accommodate excess oxygen under high pO2 via interstitials and can also cope with low pO2
atmospheres via oxygen loss [207]. For instance, higher electrical conductivities and oxygen interstitial
concentrations have been reported for La2Ni0.6Cu0.4O4+ after heat treatments under high oxygen pressure [216].
Along with high oxygen ion transportation, another advantage of LNO is its low lattice expansion in changing
temperatures and oxygen partial pressures[217]. However, it is not recommended that this material be used in
conjunction with the electrolyte YSZ as interfacial reactions between the electrode and electrolyte have been
inferred, forming the insulating La2Zr2O7 phase [218] [207]. Rieu et al [218] tested graded LNO electrode layers
on YSZ which included a CGO diffusion barrier, a dense thin LNO layer and a thick porous LNO layer. It was
found that the porous LNO layer readily delaminated from the CGO interlayer but the addition of the dense thin
LNO layer improved adhesion and provided more contact points for oxygen diffusion to the electrolyte. Using
this set-up an ASR of 0.11 Ω.cm2 was achieved for a symmetrical cell with Pt current collectors at 800°C. It
should be noted that a Pt current collector can only be used up to temperatures of around 700-800oC as above
this temperature Pt is thought to catalyze the irreversible formation of higher order Ruddlesden-Popper phases,
La3Ni2O7-δ and La4Ni3O10-δ caused by the oxidation of LNO [219].
Some lanthanum nickelate based materials also perform more effectively in electrolysis, rather than fuel cell
mode. Perez-Coll et al [220] tested La2NiO4, La3Ni2O7 and a La2NiO4-Ce0.8Sm0.2O2-δ composites as electrodes in
symmetrical cells on Ce0.8Sm0.2O2−δ + 2%Co electrolyte. Applying a cathodic, fuel cell polarization of 530 mA
cm-2 improved the electrode polarization resistance from 3.30 Ω.cm2 at OCV to 0.32 Ω.cm2 at 700oC. The effect
of applying an anodic current was even more pronounced. This trend was observed for all the lanthanum
nickelate materials tested, though less significant for the composite. The addition of the ionically conductive
CSO material significantly improved electrode performance. Applying a cathodic polarization of 530 mA cm -2
improved the composite electrode polarization resistance from 0.64 Ω.cm2 at OCV to 0.34 Ω.cm2 at 700oC.
An example of doping on the A (La) site of LNO is the addition of up to 0.3 Sr 2+ in place of La3+ which
reportedly reduces electrical resistance and improves stability [221]. However, it is noted elsewhere, [210] that
the addition of Sr increases oxygen vacancies when doped into perovskite materials, and so reduces ionic
conductivity in K2NiF4 structures since these materials conduct oxygen predominantly via interstitials.
Aguadero et al [221] agree that Sr2+ doping in place of La3+ decreases ionic conductivity due to the hole doping
effect resulting in the oxidation of Ni2+ to Ni3+ to preserve charge neutrality without the need of excess oxygen.
It is argued that the reduction of ionic conduction is acceptable for the increase of electronic conductivity which
is noted to be poor in LNO. It was also found that ionic and electronic conductivity of La1.9Sr0.1NiO4+δ could be
increased by applying heat treatment of 650oC and high oxygen pressure of 200 bar to the powders; this
treatment increases electrical conductivity and oxygen interstitial concentration [221]. It is noted that the
temperatures used should not be so high as to form unwanted higher order Ruddlesden Popper phases
(Lan+1NinO3n+1) [222].
5. Epitaxial thin film electrodes
Several studies have been performed using nearly fully dense polycrystalline, even ideally single crystals or
epitaxial films to avoid the effects of microstructure and composition in the comprehension of the intrinsic
properties of the materials as previously commented by Adler [223] and reported in several comprehensive
review articles about thin-film technologies for SOFCs [224-227].
Ruddlesden-Popper (RP)-type oxides have attracted great interest as epitaxial thin films due to their intrinsic
anisotropic transport properties. Before a fuel cell application can be considered for these thin film RP oxides,
many of the fundamental parameters governing fuel cell performance have to be determined. Evidently these
may differ significantly from the bulk materials. Kim et al [228] first successfully deposited the (100)-oriented
epitaxial films of La2NiO4+δ on LaAlO3 (001) substrates by pulsed laser deposition (PLD). The authors
determined the oxygen transport behaviour on a 300 nm thick film using Electrical Conductivity Relaxation
(ECR) measurements and suggest that the performance is controlled by the surface exchange reaction. In a
subsequent article [229], using AC impedance spectroscopy, the authors investigated the kinetic behavior of
dense polycrystalline La2NiO4 thin-films with a thickness of 300 nm, grown on yttrium stabilized zirconia
(YSZ) single crystal substrates by PLD. Furthermore, very high quality epitaxial La2NiO4 films grown along c-
axis direction on single crystal SrTiO3 (STO) (100) and NdGaO3 (NGO) (110) substrates were attained by
Garcia et al [230] via the use of pulsed injection metal organic chemical vapor deposition (PI-MOCVD). The
authors observed that the values of the electrical conductivity improved significantly with decreasing film
thickness such that the values are prominently superior to the highest from bulk materials (~100 Scm -1) [161,
231], and even the values from layers of 50 nm and thinner films are strikingly higher than those from single
crystals along the ab-axis (~200 Scm-1) [157, 232]. Subsequently, a maximum value for the electrical
conductivity of this material (475 Scm-1) in 33 nm thick films was reported by Burriel et al [233]. They also
comment that the absolute strain plays a key role in the transport properties of this material. Further works
regarding determining the anisotropic tracer diffusion and surface exchange coefficients of the epitaxial La2NiO4
films by oxygen isotopic exchange and distribution via the isotope exchange depth profile (IEDP) method were
performed. The authors developed a new and effective method for the measurements of transport properties in
two directions, traverse and longitudinal, as shown in Figure 9 [164]. Both tracer diffusion coefficients along the
c-direction and ab-direction tend to increase with increasing thickness. It, however, seems that both surface
exchange coefficients along the two different directions have no direct correlation with film thickness. This
study corroborated that the oxygen diffusion and surface exchange exhibits highly anisotropic behavior and both
give data 2 to 3 orders of magnitude higher along the ab-plane than those along the c-direction. Figure 10 and
Figure 11 show a comparison of oxygen diffusion and surface exchange coefficients (D* and k*, respectively)
from dense polycrystalline, single crystal and epitaxial La2NiO4+ thin film samples [164].
Higher order RP phase lanthanum nickel oxide films (n = 2 and 3) have been only demonstrated by Raju et al
[234]. In their studies, oriented perovskite-type LaNiO3, K2NiF4-type La2NiO4 and higher order RP-phase
La3Ni2O7 and La4Ni3O10 films have been synthesised via the method of Nebulized Spray Pyrolysis with a low
processing temperature and the use of precursors of lanthanum and nickel acetylacetonate mixture. Even though
the cation stoichiometry of La3Ni2O7 and La4Ni3O10 are slightly off and there is some doubt whether the higher
order RP films are oriented, the research is the only report of depositing the n = 2 and 3 members of the
monophasic RP-type films. More recently, Burriel et al. [235] attempted to deposit the pure La3Ni2O7 and
La4Ni3O10 thin-films by PI-MOCVD. However, despite mixed-phase films being obtained, particular films
composed of pure La2NiO4 and LaNiO3 forming a microstructure with disordered intermixed nanodomains were
observed. These nanodomains progressively increased with the n value, and the electronic conductivity also
shows a progressive change from the semiconducting to metallic behaviour, meaning the transport properties in
nanostructured epitaxial films of the Lan+1NinO3n+1 series could be enhanced by the nanodomains, as commented
by the authors. This suggests a new research direction in the preparation of nanocomposite films with tailored
properties.
Of further interest are heterostructured thin-film oxides for SOFCs building on the earlier interest in strain at
interfaces and the natural layered nature of the RP-phase oxide films. RP-phases possess natural heterostructures
with alternating blocks of perovskite and rock-salt. Thus, it is of interest to investigate whether growing
heteroepitaxial films of these oxides will enhance electrical and electrochemical properties in SOFC cathodes in
comparison with the individual bulk materials. For example, an enhancement of oxygen surface exchange on the
hetero-interface of (La, Sr)CoO3/(La, Sr)2CoO4 polycrystalline layered-films has been reported by Sase et al.
[236]. Further evidence is presented by oxygen reduction kinetics enhancement on heterostructured interfaces of
La0.8Sr0.2CoO3−δ (LSC113)/(La0.5Sr0.5)2CoO4±δ (LSC214) epitaxial films demonstrated by Crumlin et al [237]. For the
first example of half cells with epitaxial films on epitaxial electrolyte substrates, Yamada et al [238] deposited
heteroepitaxial SOFC systems. The system is composed of 14 nm-thick (110) RP-type Nd 2NiO4+δ epitaxial films
on (100) YSZ single crystal electrolytes. The authors claim that the type of K2NiF4 structure may possess a
certain extent of inherent flexibility enabling epitaxial growth. They discovered Nd2NiO4+δ epitaxy can grow
along the orientation of (110) plane on (100) YSZ substrates although its lattice mismatch is as large as that of
9.9% with the YSZ substrates. With the rather similar value of lattice mismatch along growing directions of
(100) or (001), however, it is surprising that they found no other orientations (for instance, (100) or (001)) of
Nd2NiO4+δ epitaxial films have been grown on the (100) YSZ substrates. This might be caused by the different
surface energy of crystal planes. Moreover, the authors also found the activation energy for oxide ion
conductivity in the series of epitaxial films is significantly influenced by orientation, presumably as a result of
the strong compressive strain. This is the first example of the heteroepitaxial SOFC system to date. From this
work it is clear that the advantage of intrinsic oxygen anisotropic transport properties in RP-phase materials can
be exploited, and offers the possibility of optimising their oxide ionic transport by preparing highly oriented
samples to align channels of oxide ion diffusion.
6. Conclusions
The need to find novel materials with good performance in solid state electrochemical devices such as SOFCs
and SOECs at intermediate temperatures (500-700 C) has promoted the study of a significant number of
different materials. The study of the defect chemistry and physical properties relationships has increased the
knowledge of the different factors governing the transport and mechanical properties of these cells and the effect
of the performance of the different materials on the other cell components.
Gd doped cerium oxide is considered one of the most effective materials for use as an IT-SOFC electrolyte due
to its high ionic conductivity in the intermediate temperature range and the possession of a thermal expansion
coefficient comparable to that of stainless steel. It is however necessary to sinter CGO at a temperature that will
not prove detrimental to any steel interconnect used in the cell. Considerable reduction in the sintering
temperature of CGO through doping with small concentrations of transition metal oxides has been achieved.
The effect of these additives on the grain and bulk ionic conductivity, and the possible mechanisms for the
improvement on the densification, have also been reported. Regarding the development of mixed ionic
electronic conductors, several materials with perovskite-like structures have been studied. Among them Co-
containing phases appear to present the higher values of oxygen conductivity and lower polarization resistances
at intermediate temperatures. Promising alternative materials have been found particularly within the pyrochlore
and YBaCo3ZnO7 derivatives and so it is expected that further investigations would lead to the development of
materials with improved properties for intermediate temperature applications.
Whilst fuel cell electrode electrochemistry is relatively well understood, it seems that further research should be
directed towards understanding the electrochemical reactions on the micro-scale and the importance of
impurities on performance of the hydrogen cathode in SOECs. For SOEC anodes the conventional lanthanum
transition metal perovskites as La0.8Sr0.2FeO3-δ (LSF), La0.7Sr0.3Cu0.1Fe0.9O3-δ (LSCuF), La0.6Sr0.4Co0.2Fe0.8O3−δ
(LSCoF), and La0.8Sr0.2MnO3−δ (LSM) were identified as functioning better in a fuel cell mode rather than
electrolysis mode. However, Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and some lanthanum nickelate based materials from
the Ruddlesden-Popper family perform more effectively in electrolysis, rather than fuel cell mode. Also, the
study of these materials as epitaxial thin films highlight that the application of thin film technology in SOFC and
SOEC technologies could significantly improve the performance of anisotropic oxides and favor their
implementation in intermediate temperature devices.
References
[1] BCH Steele, A Heinzel (2001) Nature 414: 345. [2] Y Matsuzaki, I Yasuda (2002) Solid State Ionics 152: 463. [3] C Athanassiou, G Pekridis, N Kaklidis, K Kalimeri, S Vartzoka, G Marnellos (2007) Int. J. Hydrog.
Energy 32: 38. [3a] DM Bastidas, SW Tao, JTS Irvine, (2006) J.Mater. Chem., 16: 1603 [4] M Liu, B Yu, J Xu, J Chen (2008) J. Power Sources 177: 493. [5] B Yu, W Zhang, J Chen, J Xu, S Wang (2008) Science in China Series B-Chemistry 51: 289. [6] K Huang, J Wan, JB Goodenough (2001) J. Mater. Sci. 36: 1093. [7] BCH Steele, A Heinzel (2001) Nature 414: 345. [8] JM Ralph, AC Schoeler, M Krumpelt (2001) J. Mater. Sci. 36: 1161. [9] BCH Steele (2001) J. Mater. Sci. 36: 1053. [10] NQ Minh (1993) J. Am. Ceram. Soc. 76: 563.[11] SPS Badwal (1992) Solid State Ionics. 52: 23.[12] TH Etsell, SN Flengas (1970) Chem. Rev. 70: 339. [13] BCH Steele (2000) Solid State Ionics. 129: 95. [14] NM Sammes, GA Tompsett, H Nafe, F Aldinger (1999) J. Eur. Ceram. Soc. 19: 1801. [15] T Takahashi, H Iwahara, T Arao (1975) J. Appl. Electrochem. 5: 187. [16] MJ Verkerk, K Keizer, AJ Burggraaf (1980) J. Appl. Electrochem. 10: 81.[17] AJ Jacobson (2010) Chem. Mater. 22: 660. [18] T Ishihara, H Matsuda, Y Takita (1994) J. Am. Chem. Soc. 116: 3801. [19] PN Huang, A Petric (1996) J. Electrochem. Soc. 143: 1644. [20] E Djurado, M Labeau (1998) J. Eur. Ceram. Soc. 18: 1397.[21] JW Stevenson, TR Armstrong, LR Pederson, J Li, CA Lewinsohn, S Baskaran (1998) Solid State
Ionics 113: 571. [22] K Yamaji, T Horita, M Ishikawa, N Sakai, H Yokokawa (1999) Solid State Ionics 121: 217. [23] PN Huang, A Horky, A Petric (1999) J. Am. Ceram. Soc. 82: 2402. [24] KN Kim, BK Kim, JW Son, et al. (2006) Solid State Ionics 177: 2155. [25] YB Lin, SA Barnett (2006) Electrochem. Solid State Lett. 9: A285.[26] Z Bi, Y Dong, M Cheng, B Yi (2006) J. Power Sources 161: 34. [27] H Inaba, H Tagawa (1996) Solid State Ionics. 83: 1. [28] H Inaba, T Nakajima, H Tagawa (1998) Solid State Ionics. 106: 263.[28a] B Rambabu, S Ghosh, H Jena (2006) J. Mater. Sci. 41: 7530.[28b] V Esposito, M Zunic, E Traversa, (2009) Solid State Ionics 180: 1069 [29] C Kleinlogel, LJ Gauckler (2000) Solid State Ionics. 135: 567. [30] E Jud, LJ Gauckler (2005) J. Electroceram. 14: 247. [31] C Kleinlogel, LJ Gauckler (2001) Adv. Mater. 13: 1081. [32] GS Lewis (2002) PhD Thesis, University of London, [33] E Jud, Z Zhang, W Sigle, LJ Gauckler (2006) J. Electroceram. 16: 191. [34] GS Lewis, A Atkinson, BCH Steele, J Drennan (2002) Solid State Ionics. 152: 567. [35] DP Fagg, JCC Abrantes, D Perez-Coll, P Nunez, VV Kharton, JR Frade (2003) Electrochim. Acta 48:
1023. [36] ZL Zhang, SA Wilfried, M Ruhle, E Jud, LJ Gauckler (2007) Acta Mater. 55: 2907. [37] E Jud, CB Huwiler, LJ Gauckler (2005) J. Am. Ceram. Soc. 88: 3013. [38] CM Kleinlogel, LJ Gauckler (2000) J. Electroceram. 5: 231. [39] JD Nicholas, LC De Jonghe (2007) Solid State Ionics. 178: 1187. [40] DJ Kim (1989) J. American Ceram. Soc. 72: 1415. [41] C Kleinlogel, LJ Gauckler (1999) Electrochem. Soc. Proc. 99-19: 225. [42] HJ Avila-Paredes, S Kim (2006) Solid State Ionics. 177: 3075.[43] W Zajac, L Suescun, K Swierczek, J Molenda (2009) J. Power Sources 194: 2. [44] DP Fagg, VV Kharton, JR Frade (2002) J. Electroceram. 9: 199. [45] DR Ou, T Mori, F Ye, et al. (2009) J. Electrochem. Soc. 156: B825. [46] TS Zhang, LB Kong, ZQ Zeng, et al. (2003) J. Solid State Electrochem. 7: 348. [47] EY Pikalova, AN Demina, AK Demin, AA Murashkina, VE Sopernikov, NO Esina (2007) Inorg.
Mater. 43: 735. [48] Q Dong, ZH Du, TS Zhang, J Lu, XC Song, J Ma (2009) Int. J. Hydrog. Energy 34: 7903. [49] TS Zhang, J Ma, LB Kong, SH Chan, P Hing, JA Kilner (2004) Solid State Ionics. 167: 203. [50] RR Kondakindi, K Karan (2009) Mater. Chem. Phys. 115: 728. [51] TS Zhang, J Ma, YJ Leng, SH Chan, P Hing, JA Kilner (2004) Solid State Ionics. 168: 187.
[52] FM Figueiredo, FMB Marques, JR Frade (1998) Solid State Ionics 111: 273. [53] AN Petrov, VA Cherepanov, AY Zuev (2006) J Solid State Electrochem 10: 517. [54] AY Zuev, AN Petrov, AI Vylkov, DS Tsvetkov (2007) J. Mater. Sci. 42: 1901. [55] KM Seppaenen M, Taskinen P (1980) Scand. J. Metallurgy 9: 3. [56] J Mizusaki, Y Mima, S Yamauchi, K Fueki, H Tagawa (1989) J. Solid State Chem. 80: 102. [57] AN Petrov, VA Cherepanov, AY Zuev (1987) Russ. J. Phys. Chem. A 61: 630. [58] AN Petrov, AY Zuev, AI Vylkov, DS Tsvetkov (2007) J. Mater. Sci. 42: 1909. [59] AY Zuev, AI Vylkov, AN Petrov, DS Tsvetkov (2008) Solid State Ionics 179: 1876. [60] MA Senarfs-Rodriguez, JB Goodenough (1995) J.Solid State Chem. 116: 224. [61] G Thorntonf, IW Owen, GP Diakun (1991) J.Phys.: Conden. Matter 3: 417. [62] T Nakamura, M Misono, Y Yoneda (1981) Chem. Lett. 10. [63] LY Gavrilova, VA Cherepanov (1999) In: Singhal SC, Dokiya M (eds) Solid oxide fuel cells VI, PV
99-17: 404. [64] VA Cherepanov, LY Gavrilova, AN Petrov, AY Zuev (2002) Z. Anorg. Allge. Chem. 628: 2140. [65] Y Teraoka, M Yoshimatsu, N Yamazoe, T Seiyama (1984) Chem. Lett. 13: 893. [66] M Søgaard, P Vang, M Mogensen, F Willy, E Skou (2006) Structure 177: 3285 [67] EA Rudberg, K Wiik, AM Svensson, K Nisancioglu (2005) Solid State Electrochem.: 311. [68] HJM Bouwmeester (2003) Catalysis Today 82: 141. [69] T Matsuura, J Tabuchi, J Mizusaki, S Yamauchi, K Fueki (1988) J Phys Chem Solids 49: 1403. [70] MHR Lankhorst, HJM Bouwmeester, H Verweij (1996) Phys. Rev. Lett. 77: 2989. [71] MHR Lankhorst, HJM Bouwmeester, H Verweij (1997) Solid State Ionics 96: 21. [72] MHR Lankhorst, HJM Bouwmeester, H Verweij (1997) J. Solid State Chem. 133: 555. [73] AN Petrov, OF Kononchuk, AV Andreev, VA Cherepanov, P Kofstad (1995) Solid State Ionics 80:
189. [74] MV Patrakeev, IA Leonidov, EB Mitberg, et al. (1999) Ionics 5: 444. [75] VL Kozhevnikov, IA Leonidov, EB Mitberg, MV Patrakeev, AN Petrov, KR Poeppelmeier (2003) J.
Solid State Chem. 172: 296. [76] SR Sehlin, HU Anderson, DM Sparlin (1995) Phys. Rev.B 52: 11681. [77] RE van Doorn, IC Fullarton, RA de Souza, JA Kilner, HJM Bouwmeester, AJ Burggraaf (1997) Solid
State Ionics 96: 1. [78] AV Berenov, A Atkinson, JA Kilner, E Bucher, W Sitte (2010) Solid State Ionics 181: 819. [79] E Bucher, W Sitte, I Rom, I Papst, W Grogger, F Hofer (2002) Solid State Ionics 152-153: 417. [80] O Yamamoto, Y Takeda, R Kanno, M Noda (1987) Solid State Ionics 22: 241.[81] LW Tai, MM Nasrallah, HU Anderson, DM Sparlin, SR Sehlin (1995) Solid State Ionics 76: 259. [82] E Maguirea, B Gharbage, FMB Marques, JA Labrincha (2000) Solid State Ionics 127. [83] S Guntuka, S Banerjee, S Farooq, MP Srinivasan (2008) Ind. Eng. Chem. Res. 47: 154. [84] VV Kharton, AV Kovalevsky, VN Tikhonovich, EN Naumovich, AP Viskup (1998) Solid State Ionics
110: 53. [85] AA Yaremchenko, VV Kharton, AP Viskup, EN Naumovich, VN Tikhonovich, NM Lapchuk (1999)
Solid State Ionics 120: 65.[85a] N Sukpirom, S Iamsaard, S Charojrochkul, J Yeyongchaiwat, (2011) J. Mater. Sci. 46: 6500. [86] M Hrovat, N Katsarakis, K Reichmann, S Bernik, D Kus c er, J Holc (1996) Solid State Ionics 83: 99. [87] CH Chen, H Kruidhof, HJM Bouwmeester, AJ Burggraaf (1997) J.Appl. Electrochem. 27: 71. [88] VV Kharton, AP Viskup, DM Bochkov, EN Naumovich, OP Reut (1998) Solid State Ionics 110: 61. [89] M Junichiro (1992) Solid State Ionics 52: 79. [90] T Inoue, J-i Kamimae, M Ueda, K Eguchi, H Arai (1993) J. Mater. Chem. 3: 751. [91] P Hjalmarsson, M Søgaard, A Hagen, M Mogensen (2008) Solid State Ionics 179: 636. [92] K Huang, HY Lee, JB Goodenough (1998) J. Electrochem. Soc. 145: 3220. Doi:10.1149/1.1838789[93] LW Tai, MM Nasrallah, HU Anderson, DM Sparlin, SR Sehlin (1995) Solid State Ionics 76: 273. [94] LW Tai, MM Nasrallah, HU Anderson (1995) J. Solid State Chem. 118: 117. [95] SJ Skinner, JA Kilner (2003) Materials Today 6: 30. [96] JW Stevenson, TR Armstrong, RD Carneim, LR Pederson, WJ Weber (1996) J. Electrochem. Soc. 143:
2722. [97] A Petric, P Huang, F Tietz (2000) Solid State Ionics 135: 719. [98] Y Teraoka, HM Zhang, K Okamoto, N Yamazoe (1988) Mater. Res. Bull. 23: 51. [99] A Esquirol, J Kilner, N Brandon (2004) Solid State Ionics 175: 63. [100] S Wang, T Kato, S Nagata, et al. (2002) Solid State Ionics 146: 203. [101] S Wang, M Katsuki, M Dokiya, T Hashimoto (2003) Solid State Ionics 159: 71.[102] ZQ Deng, WS Yang, W Liu, CS Chen (2006) J. Solid State Chem. 179: 362.
[103] Y Takeda, R Kanno, T Takada, O Yamamoto, M Takano, Y Bando (1986) Z. Anorg. Allge. Chem. 541: 259.
[104] C de la Calle, A Aguadero, JA Alonso, MT Fernandez-Diaz (2008) Solid State Sci. 10: 1924. [105] T Takeda, Y Yamaguchi, H Watanabe, S Tomiyoshi, H Yamamoto (1969) J. Phys. Soc. Jpn, 26: 1320[106] JC Grenier, S Ghodbane, G Demazeau, M Pouchard, P Hagenmuller (1979) Mater. Res. Bull. 14: 831. [107] PD Battle, TC Gibb, AT Steel (1987) J. Chem. Soc.-Dalton Trans.: 2359. [108] PD Battle, TC Gibb (1987) J. Chem. Soc.-Dalton Trans.: 667. [109] PD Battle, TC Gibb, AT Steel (1988) J. Chem. Soc.-Dalton Trans.: 83.[110] WTA Harrison, SL Hegwood, AJ Jacobson (1995) J. Chem. Soc.-Chem. Commun.: 1953. [111] T Nagai, W Ito, T Sakon (2007) Solid State Ionics 177: 3433. [112] P Zeng, Z Shao, S Liu, ZP Xu (2009) Separ. Purif. Techn. 67: 304. [113] W Zhou, W Jin, Z Zhu, Z Shao (2010) Int. J. Hydrog. Energy 35: 1356. [114] A Aguadero, C de la Calle, JA Alonso, MJ Escudero, MT Fernandez-Diaz, L Daza (2007) Chem.
Mater. 19: 6437. [115] A Aguadero, D Perez-Coll, C de la Calle, JA Alonso, MJ Escudero, L Daza (2009) J. Power Sources
192: 132. [116] A Aguadero, J Antonio Alonso, D Perez-Coll, C de la Calle, MT Fernandez-Diaz, JB Goodenough
(2010) Chem. Mater. 22: 789. [117] Y Shen, F Wang, X Ma, T He (2011) J. Power Sources 196: 7420. [118] PY Zeng, R Ran, ZP Shao, H Yu, SM Liu, (2009) Braz. J. Chem. Eng. 26: 563 [119] P Zeng, R Ran, Z Chen, et al. (2008) J. Alloys Cmpnds 455: 465. [120] X Chen, L Huang, Y Wei, H Wang (2011) J. Membr. Sci. 368: 159. [121] Y Teraoka, HM Zhang, S Furukawa, N Yamazoe (1985) Chem. Lett.: 1743. [122] H Fukunaga, M Koyama, N Takahashi, C Wen, K Yamada (2000) Solid State Ionics 132: 279. [123] T Ishihara, M Honda, T Shibayama, H Minami, H Nishiguchi, Y Takita (1998) J. Electrochem. Soc.
145: 3177. [124] ZP Shao, WS Yang, Y Cong, H Dong, JH Tong, GX Xiong (2000) J. Membr. Sci. 172: 177. [125] ZP Shao, SM Haile (2004) Nature 431: 170. [126] J Pena-Martinez, D Marrero-Lopez, D Perez-Coll, JC Ruiz-Morales, P Nunez (2007) Electrochim. Acta
52: 2950. [127] B Wei, Z Lu, X Huang, et al. (2006) J. Eur. Ceram. Soc. 26: 2827. [128] S Svarcova, K Wiik, J Tolchard, HJM Bouwmeester, T Grande (2008) Solid State Ionics 178: 1787. [129] M Arnold, TM Gesing, J Martynczuk, A Feldhoff (2008) Chem. Mater. 20: 5851. [130] Z Yang, J Martynczuk, K Efimov, et al. (2011) Chem. Mater. 23: 3169. [131] A Yan, M Cheng, YL Dong, et al. (2006) Appl. Catal. B 66: 64. [132] J Mizusaki, T Sasamoto, WR Cannon, HK Bowen (1982) J. Am. Ceram. Soc. 65: 363. [133] J Mizusaki, T Sasamoto, WR Cannon, HK Bowen (1983) J.Am. Ceram. Soc. 66: 247. [134] JM Ralph, C Rossignol, R Kumar (2003) J.Electrochem. Soc. 150: A1518.[135] VV Kharton, AV Kovalevsk, MV Patrakeev, et al. (2008) Chem. Mater. 20: 6457. [136] K Vidal, LM Rodriguez-Martinez, L Ortega-San-Martin, et al. (2009) J.Power Sources 192: 175. [137] D Kuscer, D Hanzel, J Holc, M Hrovat, D Kolar (2001) J. Am. Ceram. Soc. 84: 1148. [138] VV Kharton, AA Yaremchenko, MV Patrakeev, EN Naumovich, FMB Marques (2003) J. Eur. Ceram.
Soc. 23: 1417.[139] E Juste, A Julian, G Etchegoyen, et al. (2008) J. Membr. Sci. 319: 185. [140] R Chiba, F Yoshimura, Y Sakurai (1999) Solid State Ionics 124: 281.[141] VV Kharton, AP Viskup, EN Naumovich, VN Tikhonovich (1999) Mater. Res. Bull. 34: 1311. [142] K Kammer, L Mikkelsen, JB Bilde-Sorensen (2006) J.Solid State Electrochem. 10: 934. [143] EV Tsipis, EA Kiselev, VA Kolotygin, JC Waerenborgh, VA Cherepanov, VV Kharton (2008) Solid
State Ionics 179: 2170. [144] S Takahashi, S Nishimoto, M Matsuda, M Miyake (2010) J Am Ceram Soc 93: 2329. [145] G Amow, SJ Skinner (2006) J. Solid State Electrochem. 10: 538.[146] G Amow, IJ Davidson, SJ Skinner (2006) Solid State Ionics 177: 1205. [147] M Greenblatt, Z Zhang, MH Whangbo (1997) Synthetic Met 85: 1451. [148] M Greenblatt (1997) Solid State & Materials Science: 174 [149] Y Kobayashi, S Taniguchi, M Kasai, M Sato, T Nishioka, M Kontani (1996) J Phys Soc Jpn 65: 3978. [150] Z Zhang, M Greenblatt (1995) J Solid State Chem 117: 236. [151] Z Zhang, M Greenblatt, JB Goodenough (1994) J Solid State Chem 108: 402. [152] M Greenblatt, Z Zhang (1994) Abstr Pap Am Chem S 208: 585. [153] D Perez-Coll, A Aguadero, MJ Escudero, L Daza (2009) J.Power Sources 192: 2. [154] SA Nedilko, VA Kulichenko, AG Dziazko, EG Zenkovich (2004) J Alloy Compd 367: 251.
[155] MD Carvalho, A Wattiaux, JM Bassat, et al. (2003) J. Solid State Electrochem. 7: 700. [156] MD Carvalho, MM Cruz, A Wattiaux, JM Bassat, FMA Costa, M Godinho (2000) J Appl Phys 88:
544. [157] JM Bassat, P Odier, A Villesuzanne, C Marin, M Pouchard (2004) Solid State Ionics 167: 341. [158] JD Jorgensen, B Dabrowski, S Pei, DR Richards, DG Hinks (1989) Phys Rev B 40: 2187. [159] JM Bassat, F Gervais, P Odier, JP Loup (1989) Mater. Sci. Eng. B 3: 507. [160] MJ Sayagués, M Vallet-Regí, JL Hutchison, JM González-Calbet (1996) J Solid State Chem 125: 133. [161] E Boehm, JM Bassat, P Dordor, F Mauvy, JC Grenier, P Stevens (2005) Solid State Ionics 176: 2717. [162] CN Munnings, SJ Skinner, G Amow, PS Whitfield, IJ Davidson (2005) Solid State Ionics 176: 1895. [163] EJ Opila, HL Tuller, BJ Wuensch, J Maier (1993) J Am Ceram Soc 76: 2363. [164] M Burriel, G Garcia, J Santiso, JA Kilner, JCC Richard, SJ Skinner (2008) J. Mater. Chem. 18: 416. [165] L Minervini, RW Grimes, JA Kilner, KE Sickafus (2000) J. Mater. Chem. 10: 2349. [166] C Frayret, A Villesuzanne, M Pouchard (2005) Chem. Mater. 17: 6538. [167] A Chroneos, D Parfitt, JA Kilner, RW Grimes (2010) J. Mater. Chem. 20: 266. [168] EV Tsipis, VV Kharton (2007) J.Solid State Electrochem. 12: 1039. [169] C Sun, R Hui, J Roller (2010) J. Solid State Electrochem. 14:1125. [170] S Skinner, CN Munnings, G Amow, P Whitfield, I Davison (2003): in SOFC VIII, Electrochem Soc.
Series, Pennington, NJ, USA, SC Singhal and M Dokiya (Eds) pp552. [171] VV Kharton, AA Yaremchenko, EV Tsipis, JR Frade (2003): in SOFC VIII, Electrochem Soc. Series,
Pennington, NJ, USA, SC Singhal and M Dokiya (Eds) pp561. [172] R Sayers, J Liu, B Rustumji, SJ Skinner (2008) Fuel Cells 8: 338. [173] JM Bae, BCH Steele (1999) J. Electroceram. 3: 37. [174] A Jaiswal, ED Wachsman (2005) J. Electrochem. Soc. 152: A787.[175] Z Zhong (2006) Electrochem. Solid-State Lett. 9: A215. [176] T Takeda, R Kanno, Y Kawamoto, Y Takeda, O Yamamoto (2000) J. Electrochem. Soc. 147: 1730. [177] R Doshi, VL Richards, JD Carter, X Wang, M Krumpelt (1999) J. Electrochem. Soc. 146: 1273. [178] JA Díaz-Guillén, MR Díaz-Guillén, KP Padmasree, AF Fuentes, J Santamaría, C León (2008) Solid
State Ionics 179: 2160. [179] R Martínez-Coronado, A Aguadero, C de la Calle, MT Fernández, JA Alonso (2011) J. Power Sources
196: 4181.[180] MA Señarıs-Rodrıguez, JB Goodenough (1995) J. Solid State Chem. 118: 323. [181] JH Kim A Manthiram (2010) Chem Mater 22: 822. [182] JH Kim, YN Kim, SM Cho, H Wang, A Manthiram (2010) Electrochim. Acta 55: 5312. [183] J-H Kim, YN Kim, Z Bi, A Manthiram, MP Paranthaman, A Huq (2011) Electrochimica Acta 56:
5740, [184] YN Kim, J-H Kim, A Manthiram (2011) Int. J. Hydrog. Energy. [185] VB Vert, JM Serra, JL Jordá (2010) Electrochem Commun 12: 278[186] RN Vannier, SJ Skinner, RJ Chater, JA Kilner, G Mairesse (2003) Solid State Ionics 160: 85. [187] C Xia, M Liu (2002) Adv. Mater. 14: 521. [188] T Yang, F Li, D Xia (2010) J. Power Sources 195: 2514.[189] C Xia (2003) Appl. Phys. Lett. 82: 901. [190] M Camaratta, E Wachsman (2007) Solid State Ionics 178: 1242. [191] M Camaratta, E Wachsman (2007) Solid State Ionics 178: 1411. [192] J Li, S Wang, R Liu, Z Wang, JQ Qian (2008) Solid State Ionics 179: 1597.[193] G Ehora, S Daviero-Minaud, M Colmont, G Andre, O Mentre (2007) Chem Mater 19: 2180. [194] A Rolle, N Preux, G Ehora, O Mentré, S Daviero-Minaud (2011) Solid State Ionics 184: 31. [195] WG Wang, M Mogensen (2005) Solid State Ionics 176: 457. [196] B Liu, Y Gu, L Kong, Y Zhang (2008) J. Power Sources 185: 946. [197] H Liu, X Zhu, M Cheng, Y Cong, W Yang (2011) Chem. Commun. 47: 2378. [198] PA Lessing (2007) J. Mater. Sci. 42: 3465. [199] M Ni, MKH Leung, DYC Leung (2008) Int. J. Hydrog. Energy 33: 2337. [200] JS Herring, JE O'Brien, CM Stoots, GL Hawkes, JJ Hartvigsen, M Shahnam (2007) Int. J.Hydrog.
Energy 32: 440. [201] X Yang, JTS Irvine (2008) J. Mater. Chem. 18: 2349. [202] K Eguchi, T Hatagishi, H Arai (1996) Solid State Ionics 86-8: 1245. [203] OA Marina, LR Pederson, MC Williams, et al. (2007) J. Electrochem. Soci. 154: B452. [204] N Osada, H Uchida, M Watanabe (2006) J. Electrochem. Soc. 153: A816. [205] A Brisse, J Schefold, M Zahid (2008) Int. J. Hydrog. Energy 33: 5375. [206] MA Laguna-Bercero, SJ Skinner, JA Kilner (2009) J. Power Sources 192: 126. [207] AJ Jacobson (2010) Chem. Mater 22:660.
[208] S Kuharuangrong (2004) Ceram. Intern 30: 273. [209] E Boehm, JM Bassat, MC Steil, P Dordor, F Mauvy, JC Grenier (2003) Solid State Sciences 5: 973. [210] R Sayers (2010) PhD Thesis, Imperial College London, London[211] WS Wang, YY Huang, SW Jung, JM Vohs, RJ Gorte (2006) J. Electrochem. Soc. 153: A2066. [212] A Tsoga, A Gupta, A Naoumidis, P Nikolopoulos (2000) Acta Materialia 48: 4709. [213] MA Laguna-Bercero, JA Kilner, SJ Skinner (2010) Chem. Mater 22: 1134. [214] B Yu, W Zhang, J Xu, J Chen (2010) Int J Hydrog Energy 35: 2829. [215] CN Munnings, SJ Skinner, G Amow, PS Whitfield, IJ Davidson (2005) Solid State Ionics 176: 1895. [216] A Aguadero, JA Alonso, MT Fernandez-Diaz, MJ Escudero, L Daza (2007) J. Power Sources 169: 17. [217] CF Kao, CL Jeng (2000) Ceram. Intern. 26: 237. [218] M Rieu, R Sayers, MA Laguna-Bercero, SJ Skinner, P Lenormand, F Ansart (2010) J. Electrochem. Soc.157: B477. [219] R Sayers, M Rieu, F Lenormand, J Kilner, S Skinner (2011), Solid State Ionics 192:531[220] D Perez-Coll, A Aguadero, MJ Escudero, L Daza (2009) J. Power Sources 192: 2. [221] A Aguadero, MJ Escudero, M Perez, JA Alonso, L Daza (2007) J.Fuel Cell Sci. Techn. 4: 294. [222] A Aguadero, M Perez, JA Alonso, L Daza (2005) J. Power Sources 151: 52. [223] SB Adler (2004) Chem Rev 104: 4791. [224] SJ Litzelman, JL Hertz, W Jung, HL Tuller (2008) Fuel Cells 8: 294. [225] LR Pederson, P Singh, XD Zhou (2006) Vacuum 80: 1066.[226] J Santiso, M Burriel (2010) J.Solid State Electrochem.: 15: 985. [227] FS Baumann, J Fleig, G Cristiani, B Stuhlhofer, HU Habermeier, J Maier (2007) J Electrochem Soc 154: B931. [228] G Kim, S Wang, AJ Jacobson, CL Chen (2006) Solid State Ionics 177: 1461. [229] GT Kim, SY Wang, AJ Jacobson, Z Yuan, CL Chen (2007) J. Mater. Chem. 17: 1316. [230] G Garcia, M Burriel, N Bonanos, J Santiso (2008) J Electrochem Soc 155: P28. [231] E Boehm, JM Bassat, MC Steil, P Dordor, F Mauvy, JC Grenier (2003) Solid State Sci. 5: 973. [232] K Dembinski, JM Bassat, JP Coutures, P Odier (1987) J.Mater. Sci. Lett. 6: 1365. [233] M Burriel, J Santiso, MD Rossell, G Van Tendeloo, A Figueras, G Garcia (2008) J Phys Chem C 112: 10982. [234] AR Raju, HN Aiyer, CNR Rao (1995) Chem Mater 7: 225. [235] M Burriel, G Garcia, MD Rossell, A Figueras, G Van Tendeloo, J Santiso (2007) Chem Mater 19: 4056. [236] M Sase, F Hermes, K Yashiro, et al. (2008) J Electrochem Soc 155: B793. [237] EJ Crumlin, E Mutoro, S-J Ahn, et al. (2010) J. Phys. Chem. Lett.: 3149. [238] A Yamada, Y Suzuki, K Saka, et al. (2008) Adv Mater 20: 4124. [239] MA Dragan (2006) PhD Thesis, RWTH Aachen
List of Figures
Figure 1 - Schematic diagram illustrating the basic electrochemical processes occurring at the electrodes in both a SOFC and a SOEC
Figure 2 – Variation in linear shrinkage as a function of temperature and Co3O4 concentration for the CGO20 system. Image adapted from [29].
Figure 3 – Variation in linear shrinkage as a function of temperature at constant heating rate for CGO with differing TMO dopants (2 mol% each). Image adapted from [41].
Figure 4 - Active areas for oxygen reduction electrochemical reaction in a a) pure electronic conductor and b) mixed ionic-electronic conductor (MIEC)
Figure 5 - Arrhenius plots of the area-specific resistance of cobalt containing perovskites with ceria-based and lanthanum gallate based electrolytes
Figure 6 - Schematic diagram of the La2NiO4 structure showing the vacancy and interstitialcy ionic transport directions and LaNiO3 perovskite and LaO rock-salt layers are indicated. (adapted from [239])
Figure 7 - Coordination environments of the two cation sites in the pyrochlore R2RuMnO7 structure with the possible Mn disproportionation in both crystallographic sites illustrated
Figure 8 - Arrhenius plot of the polarization resistance on the interface electrolyte/electrode measured in air for different cathode systems
Figure 9 - Schematic diagrams of sample configuration for (a) traverse and (b) longitudinal oxygen tracer
transport measurements (adapted from ref. [164]).
Figure 10 Anisotropy of diffusion for La2NiO4 films deposited on STO and on NGO in comparison with the literature data for La2NiO4 single crystal and dense ceramics [164].
Figure 11 Anisotropy of surface exchange property for La2NiO4 films deposited on STO and on NGO in comparison with the literature data for La2NiO4 single crystal and dense ceramics [164].
a) b)
22 4 2O e O
22 4 4H H e
222 4O O e
22 22 4 2 2H O e H O
Figure 1 - Schematic diagram illustrating the basic electrochemical processes occurring at the electrodes in both (a) an SOFC and (b) an SOEC
Figure 2 – Variation in linear shrinkage as a function of temperature and Co3O4 concentration for the CGO20
system. Image adapted from [29].
Figure 3 – Variation in linear shrinkage as a function of temperature at constant heating rate for CGO with
differing TMO dopants (2 mol% each). Image adapted from [41].
a)
e- e-O2 O2
O2-
Electrochemically active in the TPB, requires very high temperatures (LSM) b)
O2--
O2-
O2
O2-e-
e-
O2-
Great enhancement of the active area. Reduction of the working temperature.
Figure 4 - Active areas for oxygen reduction electrochemical reaction in a a) pure electronic conductor and b)
mixed ionic-electronic conductor (MIEC)
Figure 5 - Arrhenius plots of the area-specific resistance of cobalt containing perovskites with ceria-based and
lanthanum gallate based electrolytes
Figure 6 - Schematic diagram of the La2NiO4 structure showing the vacancy and interstitialcy ionic transport
directions and LaNiO3 perovskite and LaO rock-salt layers are indicated. (adapted from [239])
Figure 7 - Coordination environments of the two cation sites in the pyrochlore R2RuMnO7 structure with the
possible Mn disproponation in both crystallographic sites illustrated
Figure 8 - Arrhenius plot of the polarization resistance on the interface electrolyte/electrode measured in air for
different cathode systems
Figure 9 - Schematic diagrams of sample configuration for (a) traverse and (b) longitudinal oxygen tracer
transport measurements (adapted from ref. [164]).
Figure 10 Anisotropy of diffusion for La2NiO4 films deposited on STO and on NGO in comparison with the
literature data for La2NiO4 single crystal and dense ceramics [164].
Figure 11 Anisotropy of surface exchange property for La2NiO4 films deposited on STO and on NGO in
comparison with the literature data for La2NiO4 single crystal and dense ceramics [164].