System And Method For Increasing The Efficiency For A Solid Oxide Fuel Cell System (Cummins Power Generation)

System And Method For Increasing The Efficiency For A Solid Oxide Fuel Cell System (Cummins Power Generation)
United States Patent Application 20160028096
Vesely; Charles J. ;   et al.   January 28, 2016
Applicant: Cummins Power Generation IP, Inc.
Abstract
System and method for increasing efficiency of a solid oxide fuel cell (SOFC) system by recapturing water via a condensate extraction system that extracts water from a hot cathode exhaust flow of the SOFC stack. Further, the SOFC system can include a radiant heater which has a fuel inlet, an air intake, and an exhaust outlet independent and separate from the power generating components in the SOFC system. The radiant heater can bring the SOFC stack up to operating temperature quickly and/or maintain near operational mode temperatures of the SOFC stack during a hibernation mode.
FIELD
[0001] This disclosure relates to increasing the efficiency of solid oxide fuel cell (SOFC) system.
BACKGROUND OF THE INVENTION
[0002] Under normal operation, a typical SOFC system maintains a system operating temperature of approximately 700.degree. C. For the high temperature fuel cell system to become operational, the system typically requires significant startup time ranging anywhere between 1 to 4 hours to reach the operating temperature from near ambient environmental conditions.
[0003] Generally, in a portable SOFC system, a stack (or hot box) is heated up from the environment using the following two methods. One method burns fuel in a combustor and uses the exhaust from the combustor as a heat source for heating an incoming cold cathode air. Then, the heated cathode air is used to heat up the stack. Another method requires a separate combustor or an electric heater in the stack. The method uses the hot exhaust from the combustor to heat up the stack by convection with the external stack surface.
[0004] Further, conventional SOFC system generally uses a reformer to generate usable fuel from a hydrocarbon based (HC) feed stock fuel. The reformer can be operated as an Auto Thermal Reactor (ATR) or a steam reformer, both of which require a source of water for proper operation. A water source independent system is generally required for a portable or remote power system, especially for RV or remote site telecom gensets. In the water source independent system, water can be acquired by condensing water vapors from the exhaust anode fuel of the SOFC stack. At the SOFC stack, an electrochemical conversion process occurs which produces electricity directly from oxidizing the fuel. SOFC stack has a solid oxide or ceramic, electrolyte which requires high operating temperature which results in longer start-up times and mechanical and chemical compatibility issues.
[0005] A conventional method for condensing water vapor is to use ambient air with a heat exchanger to cool down the anode exhaust gas and then extract liquid water from that anode exhaust. This method is limited to moderate ambient temperatures, which tend to limit its usefulness in high environmental temperature conditions (e.g., summer).
[0006] Conventional methods for heating up a fuel cell stack in a SOFC system from the environment typically have low efficiencies. For example, using the exhaust from the combustor as the heat source for heating up the incoming cold cathode air, a substantial portion of the heat from the exhaust is directly released to environment and not utilized for heating the fuel cell stack. Conventional methods can also suffer from high parasitic loss of power, which can increase the fuel burn rate of the combustor.
[0007] In portable SOFC systems, conventional methods for heating up the stack can present a challenge for a battery bank capacity because portable SOFC systems are generally operated without an external power source. Additionally, high condensation rates are required to supply the system needs and achieve a water balance for increasing the efficiency of the SOFC system. The increased level of condensate production cannot be achieved by conventional methods described above at high ambient air temperatures. Thus, there can be a risk of running out of water in conventional SOFC systems absent an external water supply.
SUMMARY OF THE INVENTION
[0008] Embodiments disclosed herein increase the efficiency of SOFC system by recapturing water via a condensate extraction system that extracts water from a hot cathode exhaust flow of the SOFC stack. Further, the SOFC system can include a radiant heater which has a fuel inlet, an air intake, and an exhaust outlet independent and separate from the power generating components in the SOFC system. The radiant heater can bring the SOFC stack up to operating temperature quickly and/or maintain near operational mode temperatures of the SOFC stack during a hibernation mode.
[0009] Embodiments disclosed herein are directed to achieving the water balance for increasing efficiency of SOFC systems. Embodiments can include a condensate extraction system that cools the hot cathode exhaust flow (about 400.degree. C. typically) using an intake of ambient air through a heat exchanger to extract water as a condensate. The remaining exhaust is then rejoined to the cathode exhaust flow entering the makeup burner. The heat from the heat exchanger is also used to flash the water condensate back to vapor in the incoming air stream, which is then routed into the ATR reformer for use. The cooler of an embodiment is placed in the cathode exhaust stream exiting the heat exchanger to further cool the exhaust and condense water out of the exhaust stream.
[0010] In other embodiments, to limit the power draw of the cooler, the temperature of the exhaust stream exiting the heat exchanger is monitored and the cooling is controlled and/or regulated to cool sufficiently enough for condensing the water vapor out. In another embodiment where an absorption chiller is included and used, heat from the main exhaust is used to drive the chilling cycle and cools the exhaust exiting the heat exchanger.
[0011] An embodiment of a SOFC system for heating a solid oxide fuel cell comprises a hot box containing a fuel cell; a reformer which provides a reformed fuel to the fuel cell; and a condensate chiller mechanism, wherein the condensate chiller mechanism receives anode exhaust from the fuel cell and condenses liquid water from the anode exhaust, vaporizes the liquid water to water vapor, and directs the water vapor to the reformer to increase the amount of water vapor received by the reformer for producing the reformed fuel. In another embodiment the condensate chiller mechanism comprises a Peltier cooler for separating the liquid water from the anode exhaust. In another embodiment, the condensate chiller mechanism comprises a phase change cooler for separating the liquid water from the anode exhaust.
[0012] An embodiment of the system further comprises a fuel-based radiant heater, wherein the fuel-based radiant heater for heating the fuel cell, wherein the fuel-based radiant heater directs radiation to the fuel cell to bring the fuel cell to operating temperature at startup and/or maintain a temperature of the fuel cell to near operating temperature during hibernation mode. In an embodiment of the system, the fuel-based radiant heater is a diesel fuel-based radiant heater. In another embodiment of the system, the fuel-based radiant heater is a directed fuel-based radiant heater.
[0013] An embodiment of the system further comprises a fuel inlet for generating electricity from the fuel cell, wherein the fuel-based radiant heater has a radiant heater fuel inlet that is independent and separate from the fuel inlet. Another embodiment of the system further comprises an exhaust outlet for generating electricity from the fuel cell, wherein the fuel-based radiant heater has a radiant heater exhaust outlet that is independent and separate from the exhaust outlet. In another embodiment of the system, the radiant heater exhaust outlet is directed to provide heat to the fuel cell.
[0014] An embodiment of the system for heating a solid oxide fuel cell comprises a hot box containing a fuel cell, and a fuel-based radiant heater, wherein the fuel-based radiant heater for heating the fuel cell, wherein the fuel-based radiant heater directs radiation to the fuel cell to bring the fuel cell to operating temperature at startup and/or maintain a temperature of the fuel cell to near operating temperature during hibernation mode.
[0015] An embodiment of a method for increasing an efficiency of a SOFC system comprises the steps of directing an anode exhaust from a fuel cell to a condensate chiller; extracting water vapor from the anode exhaust and directing the water vapor to an air intake of a reformer for producing a reformed fuel with an increased water balance; producing the reformed fuel with the increased water balance; and supplying the reformed fuel with the increased water balance to the SOFC fuel cell.
[0016] Another embodiment of the method further comprises the step of generating radiation by supplying a fuel to a fuel-based radiant heater, wherein the fuel-based radiant heater directs the radiation to the fuel cell to bring the fuel cell to operating temperature at startup and/or maintain a temperature of the fuel cell to near operating temperature during hibernation mode.
[0017] Another embodiment of the method further comprises the step of bringing the fuel cell to operating temperature at startup by generating radiation from a fuel-based radiant heater, wherein the fuel-based radiant heater directs the radiation to the fuel cell.
[0018] Another embodiment of the method further comprises the step of maintaining a temperature of the fuel cell at near operating temperature of the fuel cell in hibernation mode by generating radiation from a fuel-based radiant heater, wherein the fuel-based radiant heater generates the radiation and directs the radiation to the fuel cell.
[0019] Another embodiment of the method further comprises the step of maintaining a temperature of the fuel cell at near operating temperature of the fuel cell in hibernation mode by generating radiation from a fuel-based radiant heater, wherein the fuel-based radiant heater directs the radiation to the fuel cell.
[0020] Another embodiment of the method further comprises the step of bringing the fuel cell to operating temperature at startup by generating radiation from a fuel-based radiant heater, and directing the radiation to the fuel cell.
[0021] Another embodiment of the method further comprises the step of maintaining a temperature of the fuel cell at near operating temperature of the fuel cell in hibernation mode by directing heat from radiant heater exhaust from a fuel-based radiant heater to the fuel cell.
[0022] Another embodiment of the method further comprises the step of bringing the fuel cell to operating temperature at startup by directing heat from radiant heater exhaust from a fuel-based radiant heater to the fuel cell.
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Porous Ceramic Molten Metal Composite Solid Oxide Fuel Cell Anode (University of Florida Research Foundation)

Porous Ceramic Molten Metal Composite Solid Oxide Fuel Cell Anode (University of Florida Research Foundation)
United States Patent Application 20160133979
Wachsman; Eric D. ;   et al.   May 12, 2016
Applicant: University of Florida Research Foundation Inc.
Abstract
A fuel cell anode comprises a porous ceramic molten metal composite of a metal or metal alloy, for example, tin or a tin alloy, infused in a ceramic where the metal is liquid at the temperatures of an operational solid oxide fuel cell, exhibiting high oxygen ion mobility. The anode can be employed in a SOFC with a thin electrolyte that can be a ceramic of the same or similar composition to that infused with the liquid metal of the porous ceramic molten metal composite anode. The thicknesses of the electrolyte can be reduced to a minimum that allows greater efficiencies of the SOFC thereby constructed.
BACKGROUND OF THE INVENTION
[0003] Fuel cells combine oxygen and fuel to chemically generate electricity without combustion. Solid Oxide Fuel Cells (SOFC's) use ceramic materials as an electrolyte, typically a solid yttria-stabilized zirconium oxide (YSZ), which is an excellent conductor of oxygen ions at high temperatures. SOFC technology has the distinct advantage over competing fuel cell technologies (e.g. molten carbonate, polymer electrolyte, phosphoric acid and alkali) because of its ability to use fuels other than hydrogen and their relative insensitivity to CO, which act as poisons to other fuel cell types, but is a fuel for these cells. The general design of a SOFC is two porous electrodes separated by a ceramic electrolyte. The oxygen source, typically air, contacts the cathode, for example strontium doped lanthanum manganese oxide (LSM), strontium doped lanthanum cobalt iron oxide (LSCF), or other conventional cathode material, to form oxygen ions upon reduction by electrons at the cathode/electrolyte/oxygen triple phase boundary. The oxygen ions diffuse through the electrolyte material to the anode where the oxygen ions encounter the fuel at the anode forming, water, carbon dioxide (with hydrocarbon fuels), heat, and electrons. The electrons transport from the anode through an external circuit to the cathode. A particularly useful anode for many cells is a liquid tin anode.
[0004] A Liquid Tin Anode Solid Oxide Fuel Cell (LTA-SOFC) is a fuel cell that combines the efficiency and reliability of conventional SOFCs while expanding the range of fuels that can be used, including gaseous, liquid, and solid fuels, and is particularly tolerant to impurities, such as sulfur. Another advantage is that coking is not a problem due to the low catalytic activity of tin toward carbon depositions and because the tin is a low vapor pressure liquid at use temperatures, for example, above 232.degree. C., such that a stable surface to promote excessive coke formation is not available. Typically the tin is supported on the YSZ electrolyte, which is relatively thick.
[0005] Because of the thickness of the electrolyte, available LTA-SOFCs, which are used at temperatures in excess of 1000.degree. C., have power densities that are significantly lower than other state of the art SOFCs, including those designed to function at lower temperatures, see for example International Application Publication No. WO/2010/045329. Hence, a SOFC that combines a molten metal anode with a thin electrolyte to significantly lower the cells resistance is desirable.
BRIEF SUMMARY OF THE INVENTION
[0006] Embodiments of the invention are directed to a fuel cell anode comprising a porous ceramic molten metal composite. Other embodiments of the invention are directed to a solid oxide fuel cell (SOFC) that comprises the anode comprising a porous ceramic molten metal composite. The porous ceramic molten metal composite comprises a metal or metal alloy that is infused into a porous ceramic and is liquid at a temperature below the working temperature of the SOFC. The metal or metal alloy comprises tin, bismuth, indium, lead, antimony, copper, molybdenum, mercury, iridium, palladium, rhenium, platinum, silver, arsenic, rhodium, tellurium, selenium, osmium, gold, germanium, thallium, cadmium, gadolinium, chromium, nickel, iron, tungsten, cobalt, zinc, or vanadium and the porous ceramic comprises a doped CeO.sub.2 or stabilized ZrO.sub.2, such as Gd-doped CeO.sub.2 (GDC), Y-doped CeO.sub.2 (YDC), Sm-doped cerium oxide (SDC), Sm-Nd-doped cerium oxide, yttria-stabilized zirconia (YSZ), Ca-stabilized zirconia, or Sc-stabilized zirconia.
[0007] The solid oxide fuel cell (SOFC) comprises a layer of the anode comprising the porous ceramic molten metal composite, a cathode layer comprising a metal oxide or mixed metal oxide, and an electrolyte layer comprising an oxygen ion conductive ceramic. The cathode can comprise a perovskite-type oxide, such as LaMnO.sub.3, La.sub.0.84Sr0..sub.16MnO.sub.3, La.sub.0.84Ca.sub.0.16MnO.sub.3, La.sub.0.84Ba.sub.0.16MnO.sub.3, La.sub.0.65Sr.sub.0.35Mn.sub.0.8Co.sub.0.2O.sub.3, La.sub.0.79Sr.sub.0.16Mn.sub.0.85CO.sub.0.15O.sub.3, La.sub.0.84Sr.sub.0.16Mn.sub.0.8Ni.sub.0.2O.sub.3, La.sub.0.84Sr.sub.0.16Mn.sub.0.8Fe.sub.0.2O.sub.3, La.sub.0.84Sr.sub.0.6Mn.sub.0.8Ce.sub.0.2O.sub.3, La.sub.0.84Sr.sub.0.16Mn.sub.0.8Mg.sub.0.2O.sub.3, La.sub.0.84Sr.sub.0.16Mn.sub.0.8Cr.sub.0.2O.sub.3, La.sub.0.6Sr.sub.0.35Mn.sub.0.8Al.sub.0.2O.sub.3, La.sub.0.84Scsub..sub.0.16MnO.sub.3, La.sub.0.84Y.sub.0.16MnO.sub.3, La.sub.0.7Sr.sub.0.3CoO.sub.3, LaCoO.sub.3, La.sub.0.7Sr.sub.0.3FeO.sub.3, La.sub.0.5Sr.sub.0.5CoO.sub.0.8Fe.sub.0.2O.sub.3, or a composite of a perovskite-type oxide and a solid electrolyte, for example, LSCF-GDC or LSM-YSZ. The cathode layer can comprise a metal oxide or mixed metal oxide, for example, Bi.sub.2Ru.sub.2O.sub.7 (BRO7), BRO7-(Er.sub.2O.sub.3).sub.0.2(Bi.sub.2O.sub.3).sub.0.8 (ESB) composite, BRO-(Dw.sub.2O.sub.3).sub.0.2(Bi.sub.2O.sub.3).sub.0.8) (DSB) composite, BRO-(Y.sub.2O.sub.3).sub.0.2(Bi.sub.2O.sub.3).sub.0.8) (YSB) composite, or BRO-Bi.sub.2-(x+y)Dy.sub.xW.sub.yO.sub.3 (DWSB) composite. The electrolyte layer can be GDC (Ce.sub.xGd.sub.1-xO.sub.2-.delta.), Y-doped CeO.sub.2 (YDC) (Ce.sub.xY.sub.1-xO.sub.2-.delta.), Sm-doped cerium oxide (SDC) (Ce.sub.xSm.sub.1-xO.sub.2-.delta.), Sm-Nd-doped cerium oxide (Sm.sub.xNd.sub.yCe.sub.1-x-yO.sub.2-.delta.); yttria-stabilized zirconia (YSZ); Ca-stabilized zirconia; or Sc-stabilized zirconia. The electrolyte layer can be the same oxygen ion conductive ceramic included in the porous ceramic molten metal composite of the anode layer. The electrolyte layer can be a bilayer electrolyte comprising a layer of the same oxygen ion conductive ceramic included in the anode layer and a layer of the metal oxide or mixed metal oxide of the cathode layer.
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Interconnect And Solid Oxide Fuel Cell Device (General Electric)

Interconnect And Solid Oxide Fuel Cell Device (General Electric)
United States Patent Application 20160190614
STRIKER; Todd Michael ;   et al.   June 30, 2016
Assignee: General Electric Company
Abstract
A solid oxide fuel cell (SOFC) manifold and interconnect structure includes a manifold that has a dense and hermetic planar surface that is impervious to fuel gas used with the corresponding SOFC. A porous material includes a permeable planar surface that is in lateral contact with the planar surface of the manifold to form an electrode interconnect. The exposed surface of the junction between the dense and hermetic planar surface and the permeable planar surface is substantially flat and devoid of discontinuities, corners and seams. The dense and hermetic planar surface, the permeable planar surface and the exposed surface of the junction lay in a single common plane suitable for thermal deposition of electrode and electrolyte layers.
BACKGROUND
[0002] The subject matter of this disclosure relates generally to electrochemical devices such as solid oxide fuel cells, and more particularly, to a solid oxide fuel cell (SOFC) metallic manifold and interconnect structure that provides a dense surface adjacent to a permeable surface with a flat transition perpendicular to the interfacial junction of the surfaces so that both surfaces are in the same plane. Subsequent electrode and electrolyte layers are deposited onto the surface, so that they are parallel to the planar interconnect surface.
[0003] A Solid oxide fuel cell (SOFC) converts chemical energy to electrical energy with high efficiency and low emissions. A cathode reduces oxygen on one side and supplies oxygen ions to a hermetic electrolyte. The hermetic electrolyte conducts the oxygen ions at high temperature to an anode, where the oxygen ions oxidize hydrogen to form water. A resistive load connecting the anode and cathode conducts electrons to perform work.
[0004] Anode-supported SOFCs based on traditional ceramic sintering technology are limited by the maximum manufacturable cell size at high yields; and sinter-based manufacturing facilities require large capital investment. However, metal interconnect-supported SOFCs utilizing thermal spray deposition offer a variety of manufacturing benefits as well as a more rugged design. As a result, cell sizes can be increased with more success than observed when using sintering manufacturing. The success of thermal spray deposited electrolytes is not only dependent on the intrinsic coating hermeticity, but also the design of the interconnect substrate.
[0005] The interconnect surface needs to be relatively smooth to prevent gross defects from forming as electrode, typically, although not exclusively, anode, and the subsequent electrolyte are deposited, which can result in low open circuit voltage (OCV) and poor performance at high fuel utilization (U.sub.f). In addition, the interconnect needs to have a fuel flow field designed to allow sufficient fuel gas to reach the anode and electrolyte interface to minimize mass transport polarization. Typically this is achieved by using large perforations or interconnected porosity. Powder feedstock that is fed into the thermal spray process can range from 100 nm to around 50 um for thermal spray deposition, restricting the interconnect fuel flow field to less than about 100 um porous feature sizes. Porous feature sizes less than about twice the powder size is typically adequate to deposit a complete and uniform coating, where anode and electrolyte powder can adequately bridge the features without the formation of permeable defects. The use of a porous metal foam has shown promise for providing adequate fuel to reach the anode and electrolyte interface, while still maintaining a hermetic electrolyte coating without crack causing defects. However, known designs that require the porous metal to be sealed to a dense metal manifold result in sharp transitional corners and seams that prevent full electrolyte coverage and cause localized areas of high stress concentrations after electrolyte deposition. The stress substantially increases the probability of cracking during operation, leading to the loss of OCV and U.sub.f and can ultimately cause SOFC failure.
[0006] Since a SOFC flow field carries fuel gas or air to the electrodes for electrochemical reactions, the gas and air flow fields, in conjunction with their respective manifolds must be separated and sealed to prevent fuel and air mixing. Further, the gas and air flow fields must also be electrically insulated while providing electrical interconnections, conducting electrons from their respective anode or cathode electrodes.
[0007] The manifold and flow field must provide pathways for the reactant gas to reach the electrodes. This is typically achieved using perforated, channeled, or corrugated designs. These designs do not offer a substantially smooth and flat substrate for planar coating deposition. Thermal spray deposition techniques, for example, require smooth surfaces for uniform coatings, without sharp features that can cause large local stresses leading to cracks. These qualities are desired to ensure electrolyte coating hermeticity. The electrolyte not only needs to be intrinsically hermetic, but must also form a seal to the dense portion of the manifold.
[0008] One known method deposits an electrolyte over an anode with direct bonding to the anode interconnect. This results in a seal between the electrolyte and the anode interconnect only when the electrolyte is sufficiently hermetic, eliminating fluid communication between the fuel and the oxidant (typically air). A monolithic manifold has been proposed with large perforated holes for fluid communication with the electrode and electrolyte. Since the part is monolithic, the bonding of a permeable interconnect to the manifold is not needed. However, to address the challenge of depositing thin anode and electrolyte layers over large fuel openings, the concept suggests using an expendable fugitive material in the interconnect fuel openings. This step requires a high temperature burnout and can interfere or have limited success with high temperature electrolyte deposition processes such as thermal spray deposition.
[0009] Similarly, some techniques have co-sintered metal interconnect structures with electrolyte, where the electrolyte is in contact with and forms a seal over the junction of porous and dense regions. The sealed interface requires electrolyte only to be in contact with the porous and dense interface, leaving a discontinuous and incomplete anode electrode coverage. The incomplete anode coverage and co-sintering of metal, cermet and ceramic can disadvantageously create substantial residual stresses in coating and is not desirable.
[0010] Another technique that has been used to provide manifold fluid contact to the electrodes uses a microporous porous metal. Porous metal with pore sizes less than about 100 microns have been adequate for providing complete anode coverage with low roughness values. Subsequent electrolyte deposition has been shown to be without discontinuities and stress related cracking. However, the perimeter of the porous metal, where in contact with the dense portion of the manifold, is a critical location that can cause defective coatings. Laser welding has been used to attach planar metallic porous metal to the dense manifold for thermal spray applications. Anode deposition was followed by the deposition of electrolyte, which formed a hermetic seal to the dense metal. The laser welding technique resulted in sharp corners that were undesirable, leading to high local stresses and often resulted in catastrophic electrolyte cracks adjacent to the permeable interconnect. FIG. 1 is a schematic of a porous metal laser welded to the dense manifold metal. Electrolyte cracks result in fuel and air interdiffusion, leading to lower OCV and U.sub.f.
[0011] In view of the foregoing, a need exists for a metal interconnect-supported electrochemical device that further minimizes any chance for the formation of defects that may adversely affect the open circuit voltage and/or fuel utilization.
BRIEF DESCRIPTION
[0012] According to one embodiment, an electrochemical device, such as a solid oxide fuel cell (SOFC) manifold and interconnect structure, comprises a manifold that comprises a dense and hermetic planar surface; and a porous material that comprises a permeable planar surface that is in lateral contact with the dense and hermetic planar surface to form an electrode interconnect, wherein the interfacial junction between the dense and hermetic planar surface and the permeable planar surface comprises an exposed planar surface that is substantially flat and devoid of discontinuities, corners and seams, and further wherein the dense and hermetic planar surface, the permeable planar surface and the exposed planar surface of the junction lay in a single plane common to the dense and hermetic planar surface, the permeable planar surface and the exposed planar surface of the junction. The electrochemical device manifold and interconnect structure may further comprise an anode material that is thermally sprayed onto and fully covers both the exposed planar surface of the interconnect junction and the permeable planar surface; and an electrolyte thermally deposited onto and fully covering the anode material, wherein the electrolyte is thermally bonded to the anode to hermetically seal the anode material and provide a fluid bather between an oxidant and predetermined fuel gases associated with the electrochemical device. The electrochemical device may further comprise a cathode electrode material thermally deposited onto the electrolyte, and a second electrode interconnect in fluid contact with the cathode electrode material.
[0013] Large metal supported and thermally sprayed electrode and electrolyte require coatings without regions with residual stress that can cause crack propagation. Therefore, it is beneficial to entirely coat a metal interconnected substrate face with a uniformly thick electrode. Full electrode coverage provides a low modulus interface between the metal and electrolyte, allowing for some compliance and a lower stress state in the electrolyte coating.
[0014] The success of the seal created by the interconnect junction between dense/hermetic manifold and the permeable material relies on the dense portion that is impermeable to the fuel gas that is adjacent to a porous region created by the permeable material. The porous region allows for the reducing gas to reach the anode and electrolyte interface. In addition, the surface of the interconnect junction is smooth and seamless, providing an ideal substrate for deposition of thin electrode and electrolyte layers and minimizing the chance for defects to form.
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