Single-Chamber Solid Oxide Fuel Cells at Intermediate Temperatures with Various Hydrocarbon-Air Mixtures

Abstract

There is worldwide interest in the development and commercialization of fuel cells for vehicles and portable electric devices. It is a presently accepted notion that polymer electrolyte fuel cells (PEFCs) are the only devices capable of operating at low temperatures. We believe, however, that PEFCs are not perfect from a practical point of view because they require hydrogen as the fuel, which is impractical in terms of storage and handling. An external reformer, therefore, must be used to convert more viable alcohols and hydrocarbons into hydrogen, thereby defeating their portability. There have been recent successes with solid oxide fuel cells (SOFCs) which perform well between 500 and 700ЊC directly using alcohols and hydrocarbons as the fuels. 1-3 A further reduction in the operating temperature of internal-reforming SOFCs and an enhancement of their thermal-and mechanical-shock resistance would make this technology a promising alternative to PEFCs.A novel type of fuel cell, which is distinguished from conventional fuel cells in design and principle, has been proposed by many researchers. 4-8 This fuel cell consists of only one gas chamber, where both the anode and the cathode are exposed to the same mixture of fuel and air. We will use a single-chamber fuel cell (SCFC) as a notation for this type of fuel cell. Because there is no need to separate the supply of fuel and air, it is more thermally and mechanically shock resistant than conventional fuel cells. We have recently succeeded in applying this cell design to an SOFC constructed from an yttria-stabilized zirconia (YSZ) electrolyte with a Ni-based anode and a strontium-doped lanthanum manganite (LSM) cathode. 9 This SCFC exhibits high power density in a flowing mixture of methane and air, but it must operate at the high temperature of 950ЊC in order to achieve sufficient ionic conduction in the solid electrolyte.The operation of SOFCs at reduced temperatures causes excessive ohmic and polarization losses in the cell. Thus, it is necessary to use a highly conductive electrolyte together with a highly active anode and cathode. Lanthanum gallate-10-14 or ceria-based 15-18 oxides would be promising electrolytes because of their much higher ionic conductivities than that of YSZ. In addition, Ni-ceria cermets 19 and Co-based perovskite oxides, 20,21 which exhibit mixed ionic and electronic conduction under each of their respective operating conditions, have been generally regarded as suitable anodes and cathodes, respectively, at reduced temperatures.In this study, we demonstrate that it is possible to operate a thermally and mechanically shock-resistant SOFC at reduced temperatures by combining the advantages of using a highly conductive electrolyte with the single-chamber cell design. We also show that ethane, propane, and liquefied petroleum gas (LPG) can be successfully used as the fuels in the present SCFC, especially at operating temperatures below 550ЊC. Figure 1a shows an SCFC constructed for fuel-cell tests at reduced temperatures. ExperimentalThe perf...

Numerical Modeling of Single-Chamber SOFCs with Hydrocarbon Fuels

“…The computed polarization curves for this cell at 650 and 750°C are shown in Fig. 4 for a CH 4 /O 2 ratio of 1.0. The power density increases with temperature, as expected.…”

“…8 In such a system the anode is usually on the order of 1 mm thick, while the thicknesses of the cathode and the electrolyte are only a few tens of m. 8 Although YSZ is the most frequently used electrolyte material for an SOFC, it is unlikely to be used at temperatures below 700°C due to significant ohmic loss, and alternative materials such as ceriabased or lanthanum gallate oxides should be used because of their much higher ionic conductivities. 4 Operation at reduced temperature also causes significant polarization losses at the electrodes. Ni-ceria cermets and Co-based perovskite oxides have been generally regarded as suitable anodes and cathodes, respectively.…”

Tests for the Use of La2Mo2O9‐based Oxides as Multipurpose SOFC Core Materials

“…Fuel:air mixtures are typical gas environment for single-chamber SOFC devices, which rely on the difference in catalytic activities between the anode and cathode materials (for hydrocarbon oxidation and oxygen reduction, respectively) [11,12]. Due to the relatively large explosivity domain of these fuel mixtures, special care relative to gas balance should be taken for measurements in such atmospheres.…”

Retraction: High‐Performance Molybdenum Dioxide‐Based Anode for Dodecane‐Fueled Solid‐Oxide Fuel Cells (SOFCs)

“…[1][2][3] Among the various types of fuel cell, solid-oxide fuel cells (SOFCs) have been considered the most promising energy converter to meet the increasing demand for electrical power as many aspects of our society move towards a "more electric platform". [4][5] As one illustration of this trend, the Boeing Company has been pursuing the more electric airplane (MEA) concept, which aims at substituting hydraulically and pneumatically driven systems with electrical ones.…”

“…[1][2][3] However, current Ni-YSZ cermet anodes operating with complex liquid hydrocarbon fuels display severe carbon formation on the Ni surface and sulfur poisoning (when fossil-derived fuels are used). [7][8][9][10][11][12][13] The formation of carbon deposits in the presence of hydrocarbons at operating temperatures !…”