Electrochemical Reactors

Abstract

To improve total reduction efficiency to a reduction object component in a treatment object gas.SOLUTION: A lamination structure of an electrochemical reactor is provided with: a same kind of electrode opposite structure in which anode layers of membrane-electrode assemblies adjacent to each other in a lamination direction are opposed to each other and cathode layers of the membrane-electrode assemblies adjacent to each other in the lamination direction are opposed to each other; an anode flow channel as a flow channel formed between the opposed anode layers to circulate a treatment object gas; a cathode flow channel as a flow channel formed between the opposed cathode layers to circulate the treatment object gas; and a flow channel flow adjustment structure in which a flow channel cross-sectional area of the anode flow channel is smaller than a flow channel cross-sectional area of the cathode flow channel.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an electrochemical reactor. [Background technology]

[0002] Patent Document 1 proposes a gas decomposition device that decomposes a gas (gas to be treated) containing components to be reduced such as NOx and components to be oxidized such as CO by utilizing an electrochemical reaction (oxidation-reduction reaction). This gas decomposition device has a laminated structure in which a plurality of MEAs (Membrane and Electrode Assembly) each of which is made by stacking a cathode and an anode with an electrolyte layer interposed therebetween, are stacked with a metal porous body interposed therebetween.

[0003] The gas to be treated supplied to the laminated structure flows mainly through the metal porous body sandwiched between the cathode and the anode. Therefore, when the gas to be treated is supplied to the laminated structure while a voltage is applied to the laminated structure, the components to be reduced in the gas to be treated are reduced at the cathode, while the components to be oxidized in the gas to be treated are oxidized at the anode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-270720 A Summary of the Invention [Problem to be solved by the invention]

[0005] This type of gas decomposition device is expected to be used in applications (such as decomposition of NOx components in vehicle exhaust systems) where increasing the reduction efficiency (such as the conversion rate of NOx components) of the components to be reduced is a high priority. However, in the case of the configuration of the gas decomposition device described above, while the reduction of the components to be reduced progresses on the cathode electrode as the gas to be treated flows through the flow path, oxygen generated by oxidation occurring on the anode electrode flows into the flow path.

[0006] That is, in the flow path, the oxygen content decreases due to reduction while the gas to be treated flows, while the oxygen content increases due to the inflow of oxygen from the anode electrode. Therefore, the oxygen concentration does not decrease from the inlet to the outlet of the flow path, and there is a problem that the total reduction efficiency of the components to be reduced does not improve.

[0007] The present invention has been made in view of the above problems, and has an object to provide an electrochemical reactor capable of improving the total reduction efficiency of the components to be reduced in the gas to be treated. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided an electrochemical reactor having a laminated structure in which a plurality of membrane electrode assemblies each having an anode layer and a cathode layer and an ion conductive layer interposed therebetween are laminated. In particular, the laminated structure has a homogeneous electrode facing structure in which the anode layers of adjacent membrane electrode assemblies in the stacking direction face each other and the cathode layers of adjacent membrane electrode assemblies in the stacking direction face each other, an anode flow path formed between the facing anode layers as a flow path for flowing a gas to be treated, a cathode flow path formed between the facing cathode layers as a flow path for flowing the gas to be treated, and a flow path flow adjustment structure in which the flow path cross-sectional area of ​​the anode flow path is smaller than the flow path cross-sectional area of ​​the cathode flow path. Effect of the Invention

[0009] This makes it possible to improve the total reduction efficiency of the components to be reduced in the gas to be treated. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of an exhaust system of an internal combustion engine in which an electrochemical reactor according to each embodiment of the present invention is disposed. [Diagram 2] FIG. 2 is a diagram illustrating the configuration of the electrochemical reactor according to the first embodiment. [Diagram 3] FIG. 3 is a diagram illustrating the configuration of an electrochemical reactor according to the second embodiment. [Figure 4] FIG. 4 is a diagram illustrating the configuration of an electrochemical reactor according to the third embodiment. [Diagram 5] FIG. 5 is a diagram illustrating the configuration of an electrochemical reactor according to the fourth embodiment. [Figure 6] FIG. 6 is a diagram illustrating the configuration of an electrochemical reactor according to the fifth embodiment. [Figure 7] FIG. 7 is a diagram illustrating a connection configuration between the electrochemical reactor and an external power supply according to the sixth embodiment. [Figure 8] FIG. 8 is a diagram illustrating the configuration of an electrochemical reactor according to the seventh embodiment. [Figure 9] FIG. 9 is a diagram illustrating the configuration of an electrochemical reactor according to a modified example. [Figure 10] FIG. 10 is a diagram illustrating a laminated structure constituting the electrochemical reactor according to the first reference example. [Figure 11] FIG. 11 is a diagram illustrating a laminated structure constituting an electrochemical reactor according to a second reference example. [Figure 12] FIG. 12 is a diagram illustrating the oxygen concentration distribution in the flow paths in the laminated structure of the first reference example. [Figure 13] FIG. 13 is a diagram illustrating the oxygen concentration distribution in the flow paths in the laminated structure of the second reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0012] [Application Examples of Electrochemical Reactors of Each Embodiment and Modification] FIG. 1 is a diagram illustrating a schematic configuration of an exhaust system E of an internal combustion engine 110 in which an electrochemical reactor 1 according to each embodiment described later is arranged.

[0013] As shown in the figure, the exhaust system E includes a three-way catalyst 130 and an electrochemical reactor 1 of each embodiment described later, which are arranged in order along the flow direction of the exhaust gas, as elements for treating exhaust gas (gas to be treated) discharged from an internal combustion engine 110 via an exhaust flow path 120. The exhaust gas treated by the three-way catalyst 130 and the electrochemical reactor 1 is released into the outside air via a muffler 140.

[0014] The internal combustion engine 110 is operated by, for example, a hydrocarbon fuel (such as gasoline or diesel). When mounted on a vehicle, the internal combustion engine 110 may directly drive the wheels, or may be a source of power generation for a motor that drives the vehicle. Exhaust gas discharged from the internal combustion engine 110 includes unburned fuel (HC), carbon oxides (CO), nitrogen oxides (NOx), and the like. In particular, specific examples of the internal combustion engine 110 include so-called diesel engines and lean-burn engines.

[0015] The three-way catalyst 130 is made of, for example, a platinum material, and reduces unburned fuel and carbon oxides contained in the exhaust gas from the internal combustion engine 110 .

[0016] The electrochemical reactor 1 mainly reduces nitrogen oxides contained in the exhaust gas that has passed through the three-way catalyst 130. That is, in a situation where the reduction action of the three-way catalyst 130 alone is insufficient due to factors such as a large amount of nitrogen oxides (NOx), which are the components to be reduced, in the exhaust gas that has passed through the three-way catalyst 130, the electrochemical reactor 1 decomposes NOx by further reducing the exhaust gas that has passed through the three-way catalyst 130.

[0017] [Prerequisite configuration common to the electrochemical reactors of the embodiments and modified examples] The electrochemical reactor 1 is composed of a laminated structure 100 (see FIG. 2, etc.) in which a single fuel cell is formed by stacking multiple MEAs (Membrane and Electrode Assemblies), each of which is composed of an electrolyte (particularly a solid electrolyte) sandwiched between a cathode and an anode.

[0018] When a direct current voltage is applied to the laminated structure 100 configured in this manner while a gas to be treated (particularly a gas containing NOx components) is being passed through the laminated structure 100, the following reactions take place at the anode and cathode.

[0019] Cathode (reduction reaction): 2NO+4e - →N2+2O 2- (1) Anode (oxidation reaction): 2O 2- →O2+4e - (2)

[0020] In the following, the specific configuration of the electrochemical reactor 1 of each embodiment having the above-mentioned basic configuration in common will be described in detail.

[0021] [First embodiment] 2 is a diagram illustrating the configuration of the laminated structure 100 according to the first embodiment. In the following, for ease of explanation, the direction along which the target gas to be reduced (particularly, gas containing NOx components) flows is defined as the "gas flow direction X," and the direction in which the MEAs 10 constituting the laminated structure 100 are stacked is defined as the "stacking direction Y" and is also shown in the figure.

[0022] As shown in the figure, the stacked structure 100 is formed by stacking multiple (three in FIG. 2) units (hereinafter also referred to as "MEA units 20") each consisting of two MEAs 10 combined directly or via a predetermined intervening layer (current collecting layer or metal support) while maintaining a predetermined space (cathode flow path 42 described below) between them in the stacking direction Y.

[0023] In particular, the MEA unit 20 of this embodiment is configured by combining two MEAs 10 in the stacking direction Y via a current collecting layer (hereinafter also referred to as "anode current collecting layer 80").

[0024] The MEA 10 is mainly composed of an anode layer 50 that functions as an anode (oxidation electrode), a cathode layer 60 that functions as a cathode (reduction electrode), and a solid electrolyte layer 70 that functions as an ion-conducting layer interposed between them.

[0025] The anode layer 50 is a plate-like member formed of, for example, lanthanum strontium cobalt composite oxide (LSC), lanthanum strontium cobalt iron oxide (LSCF), etc. In particular, the anode layer 50 is formed to be porous so as to ensure the function of allowing oxygen generated in the above oxidation reaction (formula (2)) to flow through the inside and flow out downstream of the electrochemical reactor 1.

[0026] The cathode layer 60 is a plate-like member formed of a metal such as nickel (Ni) and an oxide such as yttria-stabilized zirconia (YSZ). In particular, the cathode layer 60 is formed to be porous so that the gas to be treated, which contains the NOx components that are the subject of the reduction reaction (formula (1)), can flow through it.

[0027] The solid electrolyte layer 70 is a thin film formed of an oxide having oxygen ion conductivity. The oxide constituting the solid electrolyte layer 70 may be, for example, yttria-stabilized zirconia (YSZ), scandium-stabilized zirconia (SSZ), samarium-doped ceria (SDC), gadolinium-doped ceria (GDC), or lanthanum strontium magnesium gallate (LSGM).

[0028] The anode current collecting layer 80 is a plate-like member that functions as a conductive path (particularly, a conductive path with a positive terminal of an external electrode) with an external power source V (not shown in FIG. 2) in order to apply a DC voltage to the laminated structure 100 (particularly, each MEA unit 20). The anode current collecting layer 80 is made of a material (particularly, a metal material) having a certain degree of conductivity. For example, the anode current collecting layer 80 may be made of an alloy containing iron (Fe) and / or chromium (Cr), particularly ferritic heat-resistant stainless steel. Furthermore, the anode current collecting layer 80 of this embodiment is configured to have a dense structure that can inhibit the flow of the gas to be treated to a certain degree while functioning as the conductive path.

[0029] Furthermore, in the stacked structure 100 of this embodiment, the portion between the two MEAs 10 constituting the MEA unit 20 (i.e., the anode current collecting layer 80) functions as a first flow path (hereinafter also referred to as "anode flow path 41") through which the gas to be treated flows. Also, the space between the MEA units 20 adjacent to each other in the stacking direction Y functions as a second flow path (hereinafter also referred to as "cathode flow path 42") through which the gas to be treated flows.

[0030] That is, in the stacked structure 100 of this embodiment, the anode layers 50 of the two MEAs 10 (MEAs adjacent to each other in the stacking direction Y) that constitute the MEA unit 20 face each other, and the space between the facing anode layers 50 (i.e., the portion of the anode collecting layer 80) forms the anode flow path 41.

[0031] Meanwhile, the cathode layers 60 of the MEA units 20 adjacent to each other in the stacking direction Y face each other, and the space between the facing cathode layers 60 becomes the cathode flow path 42. Note that, for ease of explanation, hereinafter, a structure in which the anode layers 50 of the MEAs 10 adjacent to each other in the stacking direction Y face each other and the cathode layers 60 of the MEAs 10 adjacent to each other in the stacking direction Y face each other will also be referred to as a "homogeneous electrode facing structure."

[0032] In addition, the laminated structure 100 of this embodiment has a flow channel cross-sectional area Sa is the flow channel cross-sectional area S of the cathode flow channel 42 c Here, the flow passage cross-sectional area S a The cross-sectional area S a is a value determined by taking into consideration not only the size of the entire range in which the cross-sectional area of ​​the anode flow channel 41 extends (the width or narrowness of the flow channel itself) but also the cross-sectional shape (honeycomb shape, lattice shape, the presence or absence of a valve, etc.) that affects the amount of gas to be treated passing through the cross-sectional area even if the size of the entire range in which the cross-sectional area extends is the same. In other words, the flow channel cross-sectional area S a is defined as a value equivalent to the size of the cross section of the anode flow channel 41 through which the gas to be treated can substantially pass. c The same applies to the definition of the flow passage cross-sectional area S of the anode flow passage 41. a is the flow channel cross-sectional area S of the cathode flow channel 42 c The structure smaller than is also referred to as a "channel flow regulating structure."

[0033] In the laminated structure 100 of this embodiment, the flow channel adjustment structure is a structure in which the anode flow channel 41 is narrower than the cathode flow channel 42, more specifically, the flow channel diameter R a is the flow path diameter R of the cathode flow path 42 c This is achieved by a structure that is smaller than

[0034] Hereinafter, the effects of the configuration of the laminated structure 100 described above (particularly the homogeneous electrode opposing structure and the flow path flow adjustment structure) will be described with reference to the configurations of a first and second reference examples.

[0035] FIG. 10 is a diagram illustrating a laminated structure 200 constituting the electrochemical reactor 2 according to the first embodiment, and FIG. 11 is a diagram illustrating a laminated structure 300 constituting the electrochemical reactor 3 according to the second embodiment.

[0036] For ease of comparison between the configuration of this embodiment and the configurations of each of the reference examples, the same reference numerals are used for each element constituting the laminated structure 200 or the laminated structure 300 and the corresponding elements constituting the laminated structure 100 of this embodiment. However, this is not intended to require that each element of the laminated structure 100 of this embodiment and each element of the laminated structures 200, 300 of each of the reference examples have the same structure.

[0037] 10, the stacked structure 200 of the first reference example has a structure (existing stacked structure) in which the anode layers 50 and cathode layers 60 of adjacent MEAs in the stacking direction Y (MEAs 10-1 to 10-4 in FIG. 10, in order from the positive side of the stacking direction Y) face each other and a flow path 43 for passing the gas to be treated is formed between them. In particular, in FIG. 10, the anode layer 50-2 and the cathode layer 60-1, the anode layer 50-3 and the cathode layer 60-2, and the anode layer 50-4 and the cathode layer 60-3 face each other, respectively.

[0038] In the stacked structure 200 of the first reference example, the inflowing gas to be treated comes into contact with the cathode layer 60 while flowing through the flow paths 43 (flow paths 43-1 to 43-4 in order from the positive side of the stacking direction Y in FIG. 10), causing a reduction reaction (formula (1)) and reducing the NOx components. On the other hand, in the stacked structure 200 of the first reference example, the flow paths 43 also face the anode layer 50. For this reason, even if the gas to be treated comes into contact with the anode layer 50, the NOx components are not reduced, and the desired reduction efficiency may not be obtained.

[0039] In the laminated structure 200, oxygen generated by an oxidation reaction (formula (2)) occurring in the anode layer 50 flows into the flow path 43. Therefore, while the oxygen concentration decreases toward the downstream position as the reduction of the NOx component progresses while the gas to be treated flows through the flow path 43, oxygen flows from the anode layer 50 into the entire area of ​​the flow path 43 and merges with the gas to be treated. That is, the amount of oxygen flowing in from the anode layer 50 increases toward the downstream position, and the oxygen concentration increases. As a result, the oxygen concentration does not decrease even near the outlet x1 in the flow path 43, and the oxygen concentration does not decrease in the entire area of ​​the flow path 43 from the inlet x0 to the outlet x1.

[0040] A more specific description will be given using an example shown in Fig. 10. For example, when the gas to be treated flows into the flow path 43-2, the gas comes into contact with the cathode layer 60-2 of the MEA 10-2 while flowing through the flow path 43-2, and as the gas comes into contact with the cathode layer 60-2 of the MEA 10-2, the more downstream the NOx component is reduced (the more the oxygen component decreases). In other words, when focusing on the reduction in the cathode layer 60-2, the reduction progresses more toward the outlet x1 of the flow path 43-2, and the oxygen concentration decreases.

[0041] On the other hand, oxygen generated in the anode layer 50-3 of the MEA 10-3 also flows into the flow path 43-2. ​​Since oxygen is generated over almost the entire surface of the anode layer 50-3, the amount of oxygen in the flow path 43-2 increases toward the outlet x1 of the flow path 43-2. ​​In other words, when focusing on the oxidation reaction in the anode layer 50-3, the closer to the outlet x1 of the flow path 43-2, the more oxidation progresses and the oxygen concentration increases.

[0042] Therefore, the decrease in oxygen caused by the reduction in the cathode layer 60-2 is offset by the increase in oxygen caused by the oxidation of the anode layer 50-3, and the oxygen concentration hardly decreases from the inlet x0 to the outlet x1 of the flow path 43-2.

[0043] Furthermore, oxygen ions generated by reduction in the cathode layer 60-3 of the MEA 10-3 move to the anode layer 50-3 of the MEA 10-3 through the solid electrolyte layer 70-3. As a result, the oxidation reaction in the anode layer 50-3 becomes more active, and the amount of oxygen generated increases by an amount corresponding to the reduction. Therefore, in the flow path 43-2, the oxygen concentration tends to increase slightly from the inlet x0 to the outlet x1. This phenomenon also occurs in the other flow paths 43-1 and 43-3.

[0044] 12 is a diagram illustrating the oxygen concentration distribution in the flow path 43 in the laminated structure 200 of the first reference example. As shown in the figure, in the laminated structure 200, the oxygen concentration in the flow path 43 does not decrease from the inlet x0 to the outlet x1, but rather tends to increase slightly toward the outlet x1. Therefore, in the configuration of the laminated structure 200 of the first reference example, in addition to the fact that the anode layer 50 does not contribute to reduction and thus prevents an improvement in the reduction efficiency, there is a problem in that the oxygen concentration does not decrease in the entire region of the flow path 43, which further prevents an improvement in the reduction efficiency.

[0045] In response to this, the present inventors have sought a structure capable of further improving the reduction efficiency and developed a laminated structure 300 of a second reference example shown in FIG. 11, that is, a laminated structure 300 having a homogeneous electrode facing structure.

[0046] In the configuration of the stacked structure 300 of the second reference example, the gas to be treated comes into contact with both cathode layers 60 in the cathode flow passage 42 formed between the cathode layers 60 facing each other in the stacking direction Y, and is reduced. That is, the gas to be treated flows through the cathode flow passage 42 while coming into contact with the two cathode layers 60, so that the efficiency of reducing NOx components can be improved. In addition, because the cathode flow passage 42 does not face the anode layer 50, the inflow of oxygen generated in the anode layer 50 into the cathode flow passage 42 can also be suppressed.

[0047] 13 is a diagram illustrating the oxygen concentration distribution in the cathode flow path 42 in the stacked structure 300 of the second reference example. As shown in the figure, in the stacked structure 300, the inflow of oxygen from the anode electrode layer 50 to the cathode flow path 42 is suppressed, and the reduction by the two cathode electrode layers 60 progresses toward the outlet x1, so that the oxygen concentration is suitably reduced in the process from the inlet x0 to the outlet x1.

[0048] However, in the homogeneous electrode facing structure in the laminated structure 300, anode layers 50 are present that face each other with a space or a predetermined layer interposed therebetween, and the space between these anode layers 50 also functions as a flow path (anode flow path 41) through which the gas to be treated flows. Since the gas to be treated that flows through this anode flow path 41 does not come into contact with the cathode layer 60, the NOx components contained in the gas to be treated flow out of the electrochemical reactor 3 almost as they are. For this reason, there is a concern that the total reduction efficiency of the NOx components in the electrochemical reactor 3 will decrease.

[0049] In view of the above circumstances, the present inventors have intensively studied and come up with the electrochemical reactor 1 of the present embodiment. In particular, in the laminated structure 100 of the electrochemical reactor 1, in addition to the structure of the same type of electrodes facing each other, the flow channel cross-sectional area S a is the flow channel cross-sectional area S of the cathode flow channel 42 c By providing a flow path adjustment structure that is smaller than the conventional structure, the total reduction efficiency of NOx components has been improved.

[0050] More specifically, the homogeneous electrode opposing structure reduces the oxygen concentration in the cathode flow path 42, thereby suppressing a decrease in the reduction efficiency within the cathode flow path 42, while the flow path flow adjustment structure makes it easier for the gas to be treated to flow through the cathode flow path 42, thereby improving the overall reduction efficiency of the electrochemical reactor 1.

[0051] In this embodiment, by disposing the anode current collecting layer 80 (particularly the dense anode current collecting layer 80) in the anode flow passage 41, it is possible to further enhance the effect of reducing the amount of gas to be treated that flows into the anode flow passage 41. In other words, it is possible to relatively increase the amount of gas to be treated that flows into the cathode flow passage 42, so that the total reduction efficiency of NOx components in the electrochemical reactor 1 can be further improved.

[0052] The functions and effects of the electrochemical reactor 1 of this embodiment described above will be summarized.

[0053] The electrochemical reactor 1 of this embodiment has a laminated structure 100 in which a plurality of membrane electrode assemblies (MEA 10) each including an anode layer 50, a cathode layer 60 and an ion conductive layer (solid electrolyte layer 70) interposed between them are laminated.

[0054] The laminated structure 100 includes a homogeneous electrode facing structure in which the anode layers 50 of the MEAs 10 adjacent to each other in the stacking direction Y face each other, and the cathode layers 60 of the MEAs 10 adjacent to each other in the stacking direction Y face each other, an anode flow path 41 that is a flow path for circulating a gas to be treated formed between the opposing anode layers 50, a cathode flow path 42 that is a flow path for circulating a gas to be treated formed between the opposing cathode layers 60, and a flow path cross-sectional area S a is the flow channel cross-sectional area S of the cathode flow channel 42 c and a flow channel flow regulation structure smaller than

[0055] Therefore, the homogeneous electrode facing structure prevents oxygen generated in the anode layer 50 from flowing into the cathode flow passage 42 where the reduction target component (NOx component) is reduced, thereby reducing the oxygen concentration in the cathode flow passage 42. In particular, a suitable oxygen concentration distribution in which the amount of oxygen decreases toward the outlet x1 in the cathode flow passage 42 can be realized, improving the reduction efficiency of the NOx component in the cathode flow passage 42. In addition, the flow passage flow adjustment structure makes it easier for the target gas to flow into the cathode flow passage 42 where reduction is performed, and makes it more difficult for the target gas to flow into the anode flow passage 41 where reduction is not performed. As a result, the amount of NOx component flowing out untreated from the electrochemical reactor 1 can be further reduced, improving the total NOx reduction efficiency.

[0056] In particular, the flow regulation structure of the present embodiment includes a structure in which the anode flow channel 41 is narrower than the cathode flow channel 42. More specifically, the flow regulation structure is configured such that the flow channel diameter R a is the flow path diameter R of the cathode flow path 42 c It includes structures smaller than

[0057] As a result, the above-mentioned flow control structure is arranged to have a flow path diameter R a and / or the flow channel diameter R of the cathode flow channel 42 c This can be achieved by a simple method of adjusting

[0058] Furthermore, the flow control structure of the present embodiment includes a structure in which an anode current collecting layer 80 is disposed in the anode flow channel 41 as a current collecting layer.

[0059] In this way, by using a simple configuration in which the anode current collecting layer 80 used as a conductive path between the external power source V and the anode flow passage 41 is disposed, the anode current collecting layer 80 narrows the substantial flow passage of the target gas in the anode flow passage 41 (flow passage cross-sectional area S aIn other words, the above-mentioned flow channel flow regulation structure can be specifically realized without requiring additional parts or significant changes to the flow channel structure. a is the flow passage diameter R c By adopting both a structure smaller than 100 mm and an anode current collecting layer 80 disposed in the anode flow path 41, the effect of making it easier for the gas to be treated to flow into the cathode flow path 42 and less likely to flow into the anode flow path 41 can be further enhanced.

[0060] [Second embodiment] The second embodiment will be described below, in which the same elements as those in the first embodiment are given the same reference numerals and the description thereof will be omitted.

[0061] 3 is a diagram illustrating the configuration of the electrochemical reactor 1 according to this embodiment. As shown in the figure, in the electrochemical reactor 1 of this embodiment, the laminated structure 100 is provided with a cathode current collecting layer 82, which is a current collecting layer that functions as a conductive path with an external power source V (particularly, a conductive path with the negative terminal of the external power source V), in the cathode flow path 42.

[0062] The cathode current collecting layer 82 is made of the same material as the anode current collecting layer 80, but is formed to be more porous (less dense) than the anode current collecting layer 80. This makes it even more difficult for the gas to be treated to flow into the anode flow path 41 and even more easily for the gas to flow into the cathode flow path 42.

[0063] That is, in the electrochemical reactor 1 according to this embodiment, the flow path regulation structure includes an anode current collecting layer 80 and a cathode current collecting layer 82 that is disposed in the cathode flow path 42 and is a current collecting layer that is more porous than the anode current collecting layer 80 .

[0064] As a result, a more suitable flow path flow regulating structure can be realized by the anode current collecting layer 80 and the cathode current collecting layer 82 provided as conductive paths with the external electrodes, without requiring additional parts or significant changes to the flow path structure.

[0065] [Third embodiment] Hereinafter, the third embodiment will be described, in which the same elements as those in the first or second embodiment are given the same reference numerals, and the description thereof will be omitted.

[0066] 4 is a diagram illustrating the configuration of the electrochemical reactor 1 according to this embodiment. As shown in the figure, in the electrochemical reactor 1 of this embodiment, the cathode current collecting layer 82 described in the second embodiment is impregnated with an adsorbent 84 that adsorbs NOx.

[0067] Specific examples of the adsorbent 84 include materials selected from the group consisting of alkali metals such as potassium (K) or sodium (Na), alkaline earth metals such as barium (Ba), calcium (Ca), or magnesium (Mg), rare earth elements such as lanthanum (La), and combinations of one or more of these.

[0068] As described above, by impregnating the cathode current collecting layer 82 with the adsorbent 84 that adsorbs NOx, the NOx components in the gas to be treated are more likely to be retained within the cathode flow passage 42, and it is possible to prevent the NOx components from flowing out untreated to the outside of the electrochemical reactor 1. As a result, it is possible to further improve the total NOx reduction efficiency.

[0069] [Fourth embodiment] The fourth embodiment will be described below, with the same elements as those in any of the first to third embodiments being given the same reference numerals, and the description thereof will be omitted.

[0070] 5 is a diagram illustrating the configuration of the electrochemical reactor 1 according to this embodiment. As shown in the figure, the electrochemical reactor 1 of this embodiment is based on the configuration of the second embodiment (the configuration shown in FIG. 3) and further includes a dense portion 86 provided at an upstream position in the gas flow direction X of the anode layer 50.

[0071] In this embodiment, the upstream position in the gas flow direction X means a region that is approximately half or less of the total length of the gas flow region in the anode layer 50 through which the gas to be treated can flow in the anode layer 50. In other words, the upstream position in the gas flow direction X generally corresponds to a region that is approximately half the length from the gas inlet position of the total length of the MEA 10 in the gas flow direction X.

[0072] The dense portion 86 is a portion of the anode layer 50 in the gas flow direction X, and is configured to be dense enough to obstruct the flow of the gas to be treated to a certain extent. In particular, the dense portion 86 is configured to be denser (with lower porosity) than other portions of the anode layer 50. The portion of the anode layer 50 constituting the dense portion 86 may be formed of the same material as the other portions, or may be formed of a different material.

[0073] As described above, the dense portion 86 that inhibits the flow of the gas to be treated is provided at the upstream position of the anode layer 50 in the gas flow direction X, thereby making it possible to inhibit the inflow of the gas to be treated into the anode layer 50. In particular, since the dense portion 86 is located at the upstream position of the anode layer 50, the gas to be treated can be effectively inhibited by the dense portion 86, making it easier for the gas to flow into the cathode flow path 42. Furthermore, since the dense portion 86 is located at the upstream position, it is possible to inhibit the dense portion 86 from inhibiting the flow of oxygen at the downstream position where the oxygen concentration is relatively high in the anode layer 50. In other words, it is possible to obtain the effect of guiding the gas to be treated to the cathode flow path 42 while inhibiting the inflow of the gas to be treated into the anode layer 50, without significantly inhibiting the flow of oxygen in the anode layer 50.

[0074] In particular, the dense portion 86 of the present embodiment is provided near the inlet of the gas to be treated in the anode layer 50. This can further improve the effect of suppressing the inflow of the gas to be treated into the anode layer 50 and promoting the inflow of the gas to be treated into the cathode flow passage 42. Furthermore, with this configuration, an oxidation reaction that may occur when the gas to be treated comes into contact with the anode layer 50 is also suppressed, so that the amount of oxygen generated in the anode layer 50 and entering the cathode flow passage 42 can be reduced. That is, the effect of improving the total NOx reduction efficiency in the electrochemical reactor 1 can be further improved.

[0075] [Fifth embodiment] The fifth embodiment will be described below, with the same reference numerals being used to designate the same elements as those in any of the first to fourth embodiments, and the description thereof will be omitted.

[0076] 6 is a diagram illustrating the configuration of the electrochemical reactor 1 according to this embodiment. As shown in the figure, the electrochemical reactor 1 of this embodiment is based on the configuration of the second embodiment (the configuration shown in FIG. 3), and further includes an insulating blocking member 88 that blocks the inlet xa0 of the gas to be treated in the anode flow channel 41.

[0077] This makes it possible to suppress the inflow of the gas to be treated into the anode flow path 41 where reduction of NOx components does not actually occur. In particular, with a simple configuration in which the insulating blocking member 88 blocks the inlet xa0 for the gas to be treated in the anode flow path 41, it is possible to simultaneously achieve the short-circuit suppression function required for the end of the MEA 10 and the function of making it easier for the gas to be treated to flow into the cathode flow path 42 and less likely to flow into the anode flow path 41.

[0078] In particular, the blocking member 88 is preferably configured to have a dense structure capable of impeding the flow of the gas to be treated to a certain degree while exhibiting the required insulating performance. More specifically, the blocking member 88 is preferably configured to be denser than the cathode current collecting layer 82 constituting the cathode flow path 42, and more preferably configured to be denser than the anode current collecting layer 80 constituting the anode flow path 41 in particular.

[0079] This further improves the function of making it easier for the gas to flow into the cathode flow passage 42 and harder for it to flow into the anode flow passage 41.

[0080] [Sixth embodiment] Hereinafter, the sixth embodiment will be described. The same elements as those in any of the first to fifth embodiments are denoted by the same reference numerals, and the description thereof will be omitted. In this embodiment, one aspect of a connection structure between an electrochemical reactor 1 and an external power source V is provided.

[0081] Fig. 7 is a diagram illustrating a connection structure between the electrochemical reactor 1 according to this embodiment and an external power source V. In particular, Fig. 7 illustrates the structure of the electrochemical reactor 1 as viewed from the gas flow direction X. For ease of explanation, the direction perpendicular to both the gas flow direction X and the stacking direction Y will also be referred to as the "electrode width direction Z" below.

[0082] As shown in the figure, in the electrochemical reactor 1 based on the configuration of the second embodiment (the configuration shown in FIG. 3), the MEAs 10 are connected to an external power source V in parallel with each other.

[0083] More specifically, an end (positive end in electrode width direction Z) of the anode current collecting layer 80 of each MEA 10 is connected to a positive terminal of an external power source V via a bus bar 90. Also, an end (negative end in electrode width direction Z) of the cathode current collecting layer 82 of each MEA 10 is connected to a negative terminal of the external power source V via a bus bar 92.

[0084] In this way, by adopting a structure in which each MEA 10 (particularly each MEA unit 20) constituting the laminated structure 100 is connected in parallel to each other with the external power source V, it is possible to reduce the magnitude of the voltage applied to the electrochemical reactor 1 (magnitude of the composite voltage) compared to the case in which they are connected in series. In other words, it is possible to lower the voltage of the entire device including the electrochemical reactor 1 or each of the components associated therewith.

[0085] In particular, when the electrochemical reactor 1 is used in a vehicle for exhaust gas treatment, the low voltage of the electrochemical reactor 1 makes it possible to mount the electrochemical reactor 1 on the vehicle without requiring various parts (such as an insulating converter) to achieve safety standards for high-voltage components. As a result, the number of parts required to mount the electrochemical reactor 1 on the vehicle can be reduced. Furthermore, since the MEAs 10 are connected in parallel to the external power source V, even if some of the MEAs 10 are damaged, the remaining MEAs 10 can continue to operate the electrochemical reactor 1.

[0086] Furthermore, in this embodiment, an insulating member 94 is provided at an end of the MEA 10 in the electrode width direction Z (the end on the positive side in the electrode width direction Z). In particular, the insulating member 94 is provided so as to be interposed between the MEA 10 and the bus bar 90 in the electrode width direction Z, and also between the respective ends of the anode current collecting layers 80 facing each other in the stacking direction Y (the ends on the positive side in the electrode width direction Z). This makes it possible to prevent short circuits due to unintended conduction between the MEA 10, the anode current collecting layer 80, and the bus bar 90.

[0087] Furthermore, in this embodiment, an insulating member 96 is provided at an end of the MEA 10 in the electrode width direction Z (the end on the negative side in the electrode width direction Z). In particular, the insulating member 96 is provided so as to be interposed between the MEA 10 and the bus bar 92 in the electrode width direction Z, and also between the respective ends (the ends on the negative side in the electrode width direction Z) of the cathode current collecting layers 82 that face each other in the stacking direction Y. This makes it possible to prevent short circuits due to unintended conduction between the MEA 10, the cathode current collecting layer 82, and the bus bar 92.

[0088] [Seventh embodiment] The seventh embodiment will be described below, with the same reference numerals being used to designate the same elements as in any of the first to sixth embodiments, and the description thereof will be omitted.

[0089] 8 is a diagram illustrating the configuration of the electrochemical reactor 1 according to this embodiment. As shown in the figure, the electrochemical reactor 1 of this embodiment is based on the configuration of the second embodiment (the configuration shown in FIG. 3) and further includes a housing 98 that houses the laminated structure 100. The housing 98 is formed in the shape of a metal box that can house the entire laminated structure 100.

[0090] In particular, the laminated structure 100 is configured such that the cathode layer 60 (hereinafter also referred to as the "end cathode layer 60-0") of the MEA 10 (hereinafter also referred to as the "end MEA 10-0") located at the end of the laminated structure 100 in the stacking direction Y faces the inner surface 98a of the housing 98 via an insulating sealing material 99.

[0091] In addition, a porous current collecting layer (hereinafter also referred to as "end current collecting layer 82-0") having the same configuration as the cathode current collecting layer 82 is provided between the end cathode layer 60-0 and the inner surface 98a of the housing 98 (more specifically, the insulating seal material 99). Therefore, this portion of the end current collecting layer 82-0 also functions as a flow path (hereinafter also referred to as "end flow path 42-0") through which the gas to be treated flows. In particular, the end flow path 42-0 is configured to be narrower than the cathode flow path 42. More specifically, the flow path diameter R of the end flow path 42-0 is c0 is the flow path diameter R of the cathode flow path 42 c It is constructed to be smaller than

[0092] As described above, the electrochemical reactor 1 of this embodiment further includes a housing 98 that houses the laminated structure 100. Moreover, the laminated structure 100 is configured so that the cathode layer 60 (end cathode layer 60-0) in the end MEA 10-0, which is the end membrane electrode assembly, faces the inner side surface 98a of the housing 98. Furthermore, the end flow path 42-0 is configured to be narrower than the cathode flow path 42.

[0093] The end MEA 10-0 is an MEA 10 located at the end in the stacking direction Y of the stacked structure 100. The end flow path 42-0 is a flow path formed between the end cathode layer 60-0 of the end MEA 10-0 and the inner surface 98a, through which the gas to be treated flows.

[0094] This allows a larger amount of gas to be treated to flow through the cathode flow passage 42, which faces the two cathode layers 60 and has a high reduction efficiency, compared to the end flow passage 42-0, which faces the inner side surface 98a of the casing 98 and does not contribute to the reduction of NOx components, and has a low reduction efficiency. Therefore, the total NOx reduction efficiency in the electrochemical reactor 1 can be further improved.

[0095] [Variations] The following describes modifications of the first embodiment, in which the same elements as those in the first embodiment are given the same reference numerals and their description will be omitted.

[0096] 9 is a diagram illustrating the configuration of an electrochemical reactor 1 according to a modified example. The electrochemical reactor 1 according to the modified example differs from the first embodiment in that, as a flow path flow control structure, the opposing anode layers 50 of the laminated structure 100 are directly connected to each other without interposing an anode current collecting layer 80 between them.

[0097] With this structure, the flow path diameter R of the anode flow path 41 formed between the opposing anode layers 50 a Therefore, the cross-sectional area S of the anode flow channel 41 can be reduced (in particular, reduced to approximately zero). a Since the distance between the anode flow passage 41 and the cathode flow passage 42 becomes smaller, the effect of making it difficult for the gas to be treated to flow into the anode flow passage 41 and easy for the gas to flow into the cathode flow passage 42 can be further enhanced.

[0098] In addition, in the laminated structure 100 of this modified example, by directly connecting the positive terminal of the external power source V and the anode layer 50 instead of the anode current collecting layer 80, it is possible to ensure electrical connection with the external power source V for applying a desired voltage.

[0099] The above describes embodiments and modifications of the present invention. However, the above embodiments and modifications merely illustrate some of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0100] For example, the configuration of the laminated structure 100 can be changed as desired within a range that does not impede the exertion of the intended effects of each of the above-mentioned embodiments or modifications. More specifically, in addition to the layers constituting the laminated structure 100 described in each of the above-mentioned embodiments or modifications, a reinforcing layer for supporting the layer structure of the laminated structure 100 may be added.

[0101] In particular, the configurations described in the above embodiments or modifications may be applied to a cell structure (so-called metal support cell) in which a metal support (support layer) is added between the opposing anode electrode layers 50, between the opposing cathode electrode layers 60, or to both of them to increase the strength. Furthermore, the configurations described in the above embodiments or modifications may be applied to a cell structure (so-called anode support cell or cathode support cell) in which one of the anode electrode layer 50 and the cathode electrode layer 60 is made thicker (longer in the stacking direction Y) than the other to increase the strength.

[0102] In particular, since the MEA unit 20 of the laminated structure 100 of each of the above embodiments or modifications is composed of two MEAs 10, the strength of the MEA unit 20 formed by combining these can be further increased by providing the above support structure to each MEA 10. In other words, the strength of each MEA unit 20, which is essentially a unit of the laminated structure 100, can be further increased, thereby achieving a further improvement in the strength of the entire layer structure.

[0103] Moreover, the application examples of the electrochemical reactor 1 of each embodiment and modification described in Fig. 1 are merely examples, and the application examples of the electrochemical reactor 1 are not limited thereto. On the other hand, it is particularly preferable that the electrochemical reactor 1 of this embodiment is applied to a scene in which the treatment of the reduction target component is prioritized over the oxidation target component in the treatment target gas. For example, it is particularly preferable to apply the electrochemical reactor 1 to a system (such as the exhaust system E of a diesel engine or a lean-burn engine) that is provided with a configuration (such as a three-way catalyst or an oxidation catalyst) that can sufficiently oxidize the oxidation target component CO, etc., or that does not contain much of such a component in the treatment target gas, but does not sufficiently have a configuration for reducing the reduction target component NOx component.

[0104] The configurations of the above-described embodiments and modified examples can be combined with each other to the extent that no contradiction occurs. [Explanation of symbols]

[0105] 1 electrochemical reactor, 10 MEA, 20 MEA unit, 41 anode flow path, 42 cathode flow path, 42 end flow path, 50 anode electrode layer, 60 cathode electrode layer, 70 solid electrolyte layer, 80 anode current collecting layer, 82 cathode current collecting layer, 84 adsorbent, 86 dense portion, 88 blocking member, 98 housing, 98a inner surface, 100 laminated structure

Claims

1. An electrochemical reactor having a laminated structure in which a plurality of membrane electrode assemblies each having an anode layer, a cathode layer and an ion conductive layer interposed therebetween are laminated, The laminated structure is a homogeneous electrode facing structure in which the anode layers of the membrane electrode assemblies adjacent to each other in the stacking direction face each other, and the cathode layers of the membrane electrode assemblies adjacent to each other in the stacking direction face each other; an anode flow path that is formed between the opposing anode layers and that is a flow path for passing a gas to be treated; a cathode flow path that is a flow path for passing the gas to be treated, the cathode flow path being formed between the opposing cathode layers; a flow path flow adjustment structure in which a flow path cross-sectional area of ​​the anode flow path is smaller than the flow path cross-sectional area of ​​the cathode flow path; Electrochemical reactor.

2. 2. The electrochemical reactor of claim 1, The flow path flow regulating structure includes: The anode flow path is narrower than the cathode flow path, or the opposing anode layers are directly connected to each other. Electrochemical reactor.

3. 3. The electrochemical reactor according to claim 1 or 2, The flow path flow regulating structure includes: An anode current collecting layer is disposed in the anode flow channel, Electrochemical reactor.

4. 4. The electrochemical reactor of claim 3, The flow path flow regulating structure includes: a cathode current collecting layer disposed in the cathode flow path and being a current collecting layer that is more porous than the anode current collecting layer; Electrochemical reactor.

5. 5. The electrochemical reactor of claim 4, The cathode current collecting layer is impregnated with an adsorbent that adsorbs the component to be reduced contained in the gas to be treated. Electrochemical reactor.

6. The electrochemical reactor according to any one of claims 1 to 5, The laminated structure is the anode layer further includes a dense portion that is provided at an upstream position in a flow direction of the gas to be treated and that obstructs the flow of the gas to be treated, Electrochemical reactor.

7. The electrochemical reactor according to any one of claims 1 to 6, The laminated structure is The anode flow channel further includes an insulating blocking member that blocks an inlet of the gas to be treated. Electrochemical reactor.

8. The electrochemical reactor according to any one of claims 1 to 7, The membrane electrode assemblies constituting the laminated structure are connected in parallel to each other to an external power source. Electrochemical reactor.

9. The electrochemical reactor according to any one of claims 1 to 8, Further comprising a housing for housing the laminated structure, the cathode layer of the end membrane electrode assembly of the laminated structure faces an inner surface of the housing, The end flow passage is configured to be narrower than the cathode flow passage, the end membrane electrode assembly is the membrane electrode assembly located at an end in a stacking direction of the stacked structure, The end flow path is a flow path through which the gas to be treated flows, the flow path being formed between the cathode layer and the inner surface of the end membrane electrode assembly. Electrochemical reactor.

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