Electrode materials and reaction mechanisms in solid oxide fuel cells: a brief review

Tsipis, E.V.; Хартон, В.В.

doi:10.1007/s10008-007-0468-0

Cited by 203 publications

(99 citation statements)

References 225 publications

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“…For many materials the charge carrier identity is implicit; e.g. for metals and semimetals such as carbon, charge is understood to be carried by mobile electrons, whereas for electrolyte materials such as salts dissolved in solvents and most polymer electrolytes, charge is understood to be carried by mobile ions.1,2 Some materials have the very interesting property that they may transport charge via both ions and electrons; such materials are referred to as mixed ionic electronic conductors (MIECs).3-5 MIEC materials are critically important in many electrochemical technologies, for example in battery electrodes, 6-13 fuel-cell electrodes, [14][15][16] and in certain types of membrane reactor. …”

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confidence: 99%

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Quantifying Electronic and Ionic Conductivity Contributions in Carbon/Polyelectrolyte Composite Thin Films

Shetzline

Creager

2014

J. Electrochem. Soc.

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A method for independently obtaining electronic and ionic contributions to electrical conductivity in thin-film samples comprised of carbon black (CB) mixed with polymer electrolyte is reported. The method relies upon careful control of the nature of the contact between the sample and the current-carrying electrodes. Electronic conductivities are derived from currents obtained using electronically-conductive glassy carbon electrodes to contact the sample, whereas ionic conductivities are derived from currents obtained using ionically-conductive Nafion electrodes to contact the sample. Conditions under which the measured currents are free from interference from redox reactions at the electrodes and capacitive charging at electrode-electrolyte interfaces are discussed. Electrical conduction was studied in a series of composite carbon black/polymer samples under conditions of fixed temperature and variable relative humidity (RH). For samples containing 10-20 weight percent carbon black dispersed in Nafion, electronic conductivity was higher than ionic conductivity at all RH values tested (25-100% RH). Ionic conductivity increased with increasing RH in a manner consistent with expectation from prior studies on Nafion membranes, whereas electronic conductivity decreased with increasing RH due to water swelling and weakened electrical contacts among carbon particles in the network. Electrical conduction in materials may arise from motion in an electric field of electrons, ions, or both. For many materials the charge carrier identity is implicit; e.g. for metals and semimetals such as carbon, charge is understood to be carried by mobile electrons, whereas for electrolyte materials such as salts dissolved in solvents and most polymer electrolytes, charge is understood to be carried by mobile ions.1,2 Some materials have the very interesting property that they may transport charge via both ions and electrons; such materials are referred to as mixed ionic electronic conductors (MIECs).3-5 MIEC materials are critically important in many electrochemical technologies, for example in battery electrodes, 6-13 fuel-cell electrodes, [14][15][16] and in certain types of membrane reactor. 17-20A simple measurement of electrical resistance/conductance on a bulk sample, for example from the current obtained upon application of a potential difference between two points on the sample using current-carrying electrodes, can provide values for resistivity/conductivity but it does not provide information on the nature of the charge carrier(s). Four-point-probe (e.g. van der Pauw) measurements are useful for eliminating the influence of contact resistance at the current-carrying electrodes on the measured resistance but such measurements still do not distinguish whether charge is carried by electrons, ions, or both. For some special situations, e.g. doped semiconductors, information about charge-carrier identity may be obtained from the behavior of the sample in response to an external perturbation. For example, in the case of Hall-effect ...

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confidence: 99%

“…3-5 MIEC materials are critically important in many electrochemical technologies, for example in battery electrodes, 6-13 fuel-cell electrodes, [14][15][16] and in certain types of membrane reactor.…”

mentioning

confidence: 99%

Quantifying Electronic and Ionic Conductivity Contributions in Carbon/Polyelectrolyte Composite Thin Films

Shetzline

Creager

2014

J. Electrochem. Soc.

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“…This enables usage of less expensive materials, lowers thermal stress, shortens start-up and shut-down time, and reduces number of possible unwanted chemical reactions between fuel cell components [2]. On the other hand, lower temperature decreases both conductivity and catalytic activity of fuel cells, especially cathodes [3,4]. Therefore, there is ongoing search for novel cathode materials exhibiting an improved performance at temperatures below 800°C [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, lower temperature decreases both conductivity and catalytic activity of fuel cells, especially cathodes [3,4]. Therefore, there is ongoing search for novel cathode materials exhibiting an improved performance at temperatures below 800°C [4][5][6]. Apart from an appropriate chemical composition of the cathode, it is also important to properly adjust the microstructure, especially of the cathode/electrolyte interface [7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…LNF is a mixed ionic-electronic conductor with relatively low ionic conductivity and a promising cathode or current collector material due to a moderate stability in the presence of chromia [18,19]. LSCF is a state-of-the-art mixed ionic-electronic conductor [4,5]. STF is a much weaker electronic conductor but exhibits higher ionic conductivity and the order of magnitude higher surface exchange coefficient [20].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of thin perovskite layers between cathode and doped ceria used as buffer layer in solid oxide fuel cells

Karczewski

Gazda

Szymczewska

et al. 2015

J Solid State Electrochem

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Porous and about 40-μm-thick LNF cathodes were deposited on both sides of the substrate and sintered at 1100°C. Different thicknesses of the thin perovskite layer were investigated in order to find the most effective one and to better understand its influence on the cathode/electrolyte interface. It was found that approximately 150 nm LNF or LSCF layer is sufficient to minimize interface resistance and improve cathode reproducibility. It was concluded that the thin perovskite layer increases contact area and improves the oxygen ion transport between the cathode and electrolyte without influencing the oxygen reduction reaction mechanism.

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Advanced Inorganic Materials for Solid Oxide Fuel Cells

Skinner¹,

Laguna‐Bercero²

2011

Energy Materials

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PC-SOFC -Proton conducting solid oxide fuel cell IT-SOFC -Intermediate temperature solid oxide fuel cell IntroductionFuel cells are widely regarded as a next generation technology that will contribute to reductions in emissions of gases responsible for climate change such as CO 2 . There are several modifications to the basic concept of a fuel cell that allow operation over a wide variety of temperatures and with differing fuels. One of the most promising types of fuel cell for large scale power generation and combined heat and power applications is the solid oxide fuel cell (SOFC). The solid oxide fuel cell offers many advantages over conventional combustion-based power generation technologies and has been the subject of intensive investigation for many years. As with all other fuel cells the SOFC is an electrochemical energy conversion device that converts the chemical energy contained within a fuel (for example, H 2 ) to useful electrical energy through an electrochemical oxidation process. Using the simplest fuel as an example the overall chemical reaction occurring is: To achieve this overall reaction it is essential that we consider the basic components of the fuel cell. A SOFC consists of three ceramic functional components (anode "fuel side", cathode "air side" and electrolyte) plus an electrical interconnect that is either ceramic or metallic depending upon the operating environment. These 4 components are referred to as the fuel cell and to achieve suitable power outputs these individual cells are connected to form a fuel cell stack. Schematics of two alternative designs of a single fuel cell are shown in Figure 1.At the anode the fuel is oxidised with the oxidant (oxygen) reduced at the cathode.These two components are separated by a gas tight electrolyte membrane that is a pure ionic conductor, transporting the oxide ion species from the cathode to the fuel side. This process releases electrons to an external circuit, providing the useful electrical power. These reactions are summarised as:cathode reaction Evidently these electrode reactions are significantly more complex than shown in equations 1.1. and 1.2 and fuller discussions of the proposed fuel oxidation and oxygen reduction electrode reactions are given in [1][2][3][4].It is therefore clear that in a solid oxide fuel cell there are many processes that require optimised materials, and consequently the SOFC is a complex solid state device. As a summary, it is essential that the electrolyte is a gas tight, pure ionic conductor stable over a wide pO 2 range (>10 -24 atm). Anodes have to possess stability in reducing conditions with both high ionic and electronic conductivity, and chemical compatibility with the electrolyte material. Similar properties are required for the cathode with the exception that stability is now in oxidising environments.Additionally the cathode has to be catalytically active towards oxygen reduction, which is often a rate limiting process, particularly at lower temperatures of operation (<650 o C). These are demanding pr...

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Electrode materials and reaction mechanisms in solid oxide fuel cells: a brief review

Cited by 203 publications

References 225 publications

Quantifying Electronic and Ionic Conductivity Contributions in Carbon/Polyelectrolyte Composite Thin Films

Quantifying Electronic and Ionic Conductivity Contributions in Carbon/Polyelectrolyte Composite Thin Films

Investigation of thin perovskite layers between cathode and doped ceria used as buffer layer in solid oxide fuel cells

Advanced Inorganic Materials for Solid Oxide Fuel Cells

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