A solid oxide fuel cell with discrete coated anode and operating method

Abstract

The present invention discloses a solid oxide fuel cell with a discretely coated anode and a working method. The solid oxide fuel cell includes an anode layer, an electrolyte, and a cathode layer. Among them, the anode layer is divided into an anode support layer and an anode functional layer. The anode support layer is divided into an anode support layer catalytic region and a non-catalytic region. The anode support layer catalytic region and the non-catalytic region are discretely coated on the anode functional layer. The present invention utilizes the characteristics of heat absorption during steam reforming of hydrocarbon fuels and heat release during electrochemical reactions, and designs the battery anode support layer into a discrete structure with catalytic regions and non-catalytic regions interlaced, controls the reforming reaction to occur in the catalytic region of the anode support layer, and then controls the temperature field distribution, making the temperature field distribution more uniform. This electrode structure can also be applied to anode-supported, electrolyte-supported, and cathode-supported solid oxide fuel cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cell temperature control, and relates to a solid oxide fuel cell with discretely coated anodes and a working method. Background Art

[0002] Solid oxide fuel cells (SOFCs) are highly efficient, all-solid-state, fuel-flexible, high-temperature fuel cells that can directly utilize hydrocarbon fuels and hold significant application prospects in the fields of distributed energy and combined heat and power. Hydrocarbon fuels undergo endothermic reforming reactions and exothermic electrochemical reactions at the anode. The reforming reaction primarily occurs in an area approximately 150 μm thick, while exothermic electrochemical reactions also occur at the cathode. This heat is carried away by the flow of fuel and air, forming a temperature gradient along the cell flow path. Currently, large temperature gradients exist in all co-current, counter-current, and cross-current solid oxide fuel cells, with maximum temperature differences reaching 100-300°C. Inhomogeneities in the temperature field can cause excessive thermal stress in SOFCs, leading to electrode cracking and performance degradation.

[0003] Currently, reducing the temperature gradient and improving the uniformity of the temperature field in solid oxide fuel cells can be achieved by increasing the air flow rate, optimizing the cell geometry, and optimizing operating conditions. However, significant temperature field nonuniformity still exists. When the anode uses a hydrocarbon mixture as fuel, the continuous reforming reaction of the fuel in the anode support layer causes the temperature near the inlet to continue to decrease. In the downstream of the anode channel, the hydrocarbon fuel is consumed due to reforming, and the electrochemical reaction releases heat, causing the temperature to continue to rise. In summary, the uneven temperature field distribution of existing solid oxide fuel cells leads to serious thermal stress damage to the cell. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a solid oxide fuel cell with a discretely coated anode, thereby improving the uniformity of the temperature field of the solid oxide fuel cell and reducing thermal stress damage to the battery.

[0005] The present invention is achieved through the following technical solutions:

[0006] A solid oxide fuel cell with a discrete coated anode, comprising an anode flow channel, an anode support layer, an anode functional layer, an electrolyte layer, a cathode layer and a cathode flow channel; the anode support layer comprises an anode support layer catalytic region and an anode support layer non-catalytic region;

[0007] The anode flow channel is connected to the catalytic region and non-catalytic region of the anode support layer, the catalytic region and non-catalytic region of the anode support layer are coated on the anode functional layer, and the anode functional layer and the cathode layer are coated on both sides of the electrolyte layer respectively; the cathode flow channel is connected to the cathode layer; the catalytic region and non-catalytic region of the anode support layer are discretely coated on the anode functional layer; an anode inlet is provided on one side of the anode flow channel, and an anode outlet is provided on the other side of the anode flow channel; a cathode inlet is provided on one side of the cathode flow channel, and a cathode outlet is provided on the other side of the cathode flow channel.

[0008] Preferably, the anode fuel of the solid oxide fuel cell is a hydrocarbon fuel.

[0009] Preferably, the catalytic region of the anode support layer and the non-catalytic region of the anode support layer are porous media.

[0010] Preferably, the solid material of the porous medium is a mixture of an ion conductor and an electron conductor, and the mixture includes Ni-YSZ or Ru-YSZ; the electron conductor is a catalyst for catalyzing the reforming of hydrocarbon fuels.

[0011] Preferably, the catalytic region of the anode support layer and the non-catalytic region of the anode support layer are arranged alternately, wherein the area of the catalytic region of the anode support layer gradually widens along the flow direction of the fuel.

[0012] Preferably, the non-catalytic area of the anode support layer is coated with porous foam metal; wherein the porous foam metal is made of Al or Cu material.

[0013] Preferably, the flow directions of the anode flow channel and the cathode flow channel are parallel flow configuration.

[0014] Preferably, the solid oxide fuel cell is an anode-supported type, an electrolyte-supported type, and a cathode-supported type.

[0015] Preferably, the thickness of the anode functional layer is 3 to 20 μm; the thickness of the anode support layer is 150 to 400 μm.

[0016] A method of operating a discrete anode-coated solid oxide fuel cell comprises:

[0017] Air enters the cathode layer through the cathode inlet of the cathode flow channel, undergoes a reduction reaction and releases heat, and the reaction product then flows out through the cathode outlet of the cathode flow channel; hydrocarbon fuel enters through the anode inlet of the anode flow channel, undergoes a reforming reaction in the catalytic zone of the first anode support layer to produce hydrogen and absorb heat, and the hydrogen undergoes an electrochemical reaction and releases heat in the anode functional layer; then the hydrocarbon fuel flows through the non-catalytic zone of the first anode support layer, undergoes an electrochemical reaction and releases heat, and the temperature rises; then the hydrocarbon fuel flows through the catalytic zone of the second anode support layer, undergoes a reforming reaction and an electrochemical reaction, and the temperature drops; then it flows through the non-catalytic zone of the second anode support layer to undergo an electrochemical reaction and release heat, and the temperature rises, and the cycle repeats until it reaches the anode outlet of the anode flow channel and flows out.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] The present invention provides a solid oxide fuel cell with a discretely coated anode and an operating method, comprising an anode layer, an electrolyte, and a cathode layer, wherein the anode layer is divided into an anode support layer and an anode functional layer. The anode support layer is divided into an anode support layer catalytic region and an anode support layer non-catalytic region. The anode support layer catalytic region and non-catalytic region are discretely coated on the anode functional layer. The present invention utilizes the characteristics of hydrocarbon fuel steam reforming endothermicity and electrochemical reaction exothermicity to design the battery anode support layer into a discrete structure with catalytic regions and non-catalytic regions interlaced, thereby controlling the reforming reaction to occur in the catalytic region of the anode support layer, thereby controlling the temperature field distribution to make the temperature field distribution more uniform, thereby improving the uniformity of the temperature field of the solid oxide fuel cell and reducing thermal stress damage to the battery. Traditional anode hydrocarbon fuel is quickly consumed upstream of the anode, and the downstream catalyst does not fully participate in the catalytic reaction. Therefore, the anode catalyst is excessive for the reforming reaction. The present invention reduces the amount of anode catalyst used by discretely coating the catalytic region of the anode support layer, while still achieving the required fuel utilization rate. Secondly, traditional solid oxide fuel cells primarily rely on increasing cathode flow to improve temperature uniformity. However, this increases cathode flow resistance, requires a higher-power air compressor, and still results in significant temperature gradients within the cell. This invention, however, improves temperature uniformity by modifying the electrode structure without changing the existing equipment configuration, making it more convenient.

[0020] Furthermore, the non-catalytic region of the electrode support layer of the present invention is made of an electronically conductive metal foam, which barely increases the internal resistance of the battery. Ionic conduction and electrochemical reactions in solid oxide fuel cells primarily occur in the anode functional layer. This invention only addresses the anode support layer and does not alter it, thus preventing increases in the battery's ionic conduction resistance or changes in electrochemical reaction performance.

[0021] Furthermore, the present invention adjusts the location where the reforming reaction occurs so that the heat released by the electrochemical reaction and the heat absorbed by the reforming reaction offset each other, and finely controls the temperature field, which will be more uniform than the temperature field distribution of traditional batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention.

[0023] In the figure: 1 is the anode flow channel, 2 is the catalytic area of the anode support layer, 3 is the non-catalytic area of the anode support layer, 4 is the anode inlet, 5 is the anode functional layer, 6 is the electrolyte layer, 7 is the cathode layer, 8 is the cathode inlet, 9 is the cathode flow channel, 10 is the cathode outlet, and 11 is the anode outlet. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0025] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] The preferred implementation is as follows:

[0028] The discrete coated anode solid oxide fuel cell of the present invention comprises an anode flow channel, an anode support layer catalytic region, an anode support layer non-catalytic region, an anode functional layer, an electrolyte layer, a cathode layer, a cathode flow channel, an anode inlet, an anode outlet, a cathode inlet and a cathode outlet;

[0029] The catalytic region of the anode support layer and the non-catalytic region of the anode support layer are discretely coated on the anode functional layer, and the anode functional layer is connected to the electrolyte layer and the cathode layer in sequence.

[0030] The catalytic area of the anode support layer and the non-catalytic area of the anode support layer are porous media. The porous media is composed of a skeleton composed of solid matter and a large number of densely packed tiny gaps separated by the skeleton. The solid matter of the porous medium is a mixture of ion conductors and electronic conductors, such as Ni-YSZ and Ru-YSZ. The electronic conductor is a catalyst and has the function of catalyzing the reforming of hydrocarbon fuels.

[0031] To ensure that the reforming reaction occurs as much as possible in the anode support layer, the thickness of the anode functional layer should be as thin as possible, ranging from 3 to 20 μm, to reduce the occurrence of the reforming reaction in the anode functional layer. The maximum thickness for the reforming reaction to occur is 150 μm, and the thickness of the anode support layer should be greater than the thickness for the reforming reaction to occur, ranging from 150 to 400 μm.

[0032] The anode fuel is a hydrocarbon fuel, and the hydrocarbon fuel undergoes an endothermic reforming reaction in the anode support layer, such as methane steam reforming, propane steam reforming reaction, etc.

[0033] The flow direction of the flow channels of the anode and cathode is a parallel flow configuration;

[0034] The anode support layer catalytic region and the anode support layer non-catalytic region are discretely coated on the anode functional layer.

[0035] The catalytic area of the anode support layer and the non-catalytic area of the anode support layer are porous media. The porous medium is composed of a skeleton composed of solid matter and a large number of densely packed tiny gaps separated by the skeleton. The solid matter of the porous medium is a mixture of ion conductors and electronic conductors, such as Ni-YSZ and Ru-YSZ. The electronic conductor is a catalyst and has the function of catalyzing the reforming of hydrocarbon fuels.

[0036] Solid oxide fuel cells can be of anode-supported, electrolyte-supported, and cathode-supported types.

[0037] The non-catalytic region of the anode support layer may be uncoated or coated with a porous foam metal, wherein the porous foam metal only has electronic conductivity but no catalytic function, such as Al or Cu materials.

[0038] A method for operating a discretely coated anode solid oxide fuel cell comprises the following steps:

[0039] Air enters the cell through the cathode inlet 8, where an electrochemical reduction reaction occurs in the cathode layer 7, releasing heat. The reaction products and heat flow out of the cathode outlet 10. Hydrocarbon fuel enters the anode inlet 4, where a strong steam reforming reaction occurs in the coated first anode support layer catalytic zone 2, producing hydrogen and absorbing heat. The hydrogen then undergoes an electrochemical reaction in the anode functional layer 5, releasing heat. The amount of heat absorbed by the reforming reaction depends on the fuel composition and the length of the anode support layer catalytic zone 2. Because the degree of reforming of the inlet hydrocarbon fuel is low, the reforming reaction is most intense at the inlet. As a result, the first anode support layer catalytic zone 2 is narrow, and the heat absorbed by the reforming reaction is sufficient to offset the heat released by the electrochemical reaction. The cell temperature in this region remains unchanged or decreases slightly. The fuel then flows through the first anode support layer non-catalytic zone 3. Because only the electrochemical reaction releases heat there, the temperature there rises back to or slightly above the inlet temperature. The fuel then flows through the second anode support layer catalytic zone 2. At this point, the fuel has been reformed once, and the degree of reforming has increased. Therefore, the anode support layer catalytic zone 2 at this location is wider, and the fuel undergoes steam reforming and electrochemical reactions there, causing a slight drop in temperature. The temperature then rises again as it flows through the second anode support layer non-catalytic zone 3, and this cycle repeats until it flows out of the anode outlet 11. As the hydrocarbon fuel is gradually consumed during reforming, the anode support layer catalytic zone gradually widens along the flow direction. The temperature fluctuates near the inlet temperature along the flow direction, avoiding the situation in conventional solid oxide fuel cells that use hydrocarbon mixtures as fuel and are configured in parallel flow, where the temperature near the inlet is very low and the outlet temperature is very high.

[0040] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

Claims

1. A solid oxide fuel cell with a discrete coated anode, characterized in that The invention comprises an anode flow channel (1), an anode support layer, an anode functional layer (5), an electrolyte layer (6), a cathode layer (7) and a cathode flow channel (9); the anode support layer comprises an anode support layer catalytic region (2) and an anode support layer non-catalytic region (3); The anode flow channel (1) is connected to the anode support layer catalytic region (2) and the anode support layer non-catalytic region (3); the anode support layer catalytic region (2) and the anode support layer non-catalytic region (3) are coated on the anode functional layer (5); the anode functional layer (5) and the cathode layer (7) are coated on both sides of the electrolyte layer (6); the cathode flow channel (9) is connected to the cathode layer (7); the anode support layer catalytic region (2) and the anode support layer non-catalytic region (3) are discretely coated on the anode functional layer (5); an anode inlet (4) is provided on one side of the anode flow channel (1), and an anode outlet (11) is provided on the other side of the anode flow channel (1); a cathode inlet (8) is provided on one side of the cathode flow channel (9), and a cathode outlet (10) is provided on the other side of the cathode flow channel (9); The anode support layer catalytic region (2) and the anode support layer non-catalytic region (3) are arranged in a staggered manner, wherein the area of the anode support layer catalytic region (2) gradually widens along the flow direction of the fuel; The anode support layer catalytic zone (2) is a porous medium; the solid material of the porous medium is a mixture of an ion conductor and an electron conductor; the electron conductor is a catalyst for catalyzing the reforming of hydrocarbon fuels; The non-catalytic region (3) of the anode support layer is coated with porous foam metal.

2. A discrete anode-coated solid oxide fuel cell according to claim 1, characterized in that: The anode fuel of the solid oxide fuel cell is hydrocarbon fuel.

3. A discrete anode-coated solid oxide fuel cell according to claim 1, characterized in that: The mixture includes Ni-YSZ or Ru-YSZ.

4. A discrete anode-coated solid oxide fuel cell according to claim 1, characterized in that: The porous foam metal is made of Al or Cu.

5. A discrete anode-coated solid oxide fuel cell according to claim 1, characterized in that: The flow directions of the anode flow channel (1) and the cathode flow channel (9) are parallel flow configurations.

6. A discrete anode-coated solid oxide fuel cell according to claim 1, characterized in that: The solid oxide fuel cell is of anode-supported, electrolyte-supported and cathode-supported types.

7. A discrete anode-coated solid oxide fuel cell according to claim 1, characterized in that: The thickness of the anode functional layer (5) is 3 to 20 μm; the thickness of the anode support layer is 150 to 400 μm.

8. A method for operating a discrete anode coated solid oxide fuel cell, based on the discrete anode coated solid oxide fuel cell according to any one of claims 1 to 7, characterized in that: include, Air enters the cathode layer (7) through the cathode inlet (8) of the cathode flow channel (9), undergoes a reduction reaction and releases heat, and the reaction product then flows out through the cathode outlet (10) of the cathode flow channel (9); hydrocarbon fuel enters through the anode inlet (4) of the anode flow channel (1), undergoes a reforming reaction in the first anode support layer catalytic zone (2) to produce hydrogen and absorb heat, and the hydrogen undergoes an electrochemical reaction in the anode functional layer (5) and releases heat; then the hydrocarbon fuel flows through the first anode support layer non-catalytic zone (3), undergoes an electrochemical reaction and releases heat, and the temperature rises; then the hydrocarbon fuel flows through the second anode support layer catalytic zone (2), undergoes a reforming reaction and an electrochemical reaction, and the temperature drops; then it flows through the second anode support layer non-catalytic zone (3) to undergo an electrochemical reaction and release heat, and the temperature rises, and the cycle continues until it reaches the anode outlet (11) of the anode flow channel (1) and flows out.

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