JP2008307492A - Electrochemical reactor having electrode for stable and high efficient operation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical reactor stably and highly efficiently eliminating nitrogen oxides with little power consumption, even when excessive amount of oxygen is present in engine exhaust gas. <P>SOLUTION: In the electrochemical reactor, an electrode part serving as an oxyphil decomposition reactor field in an electrochemical element is disposed to suppress a reaction, for enabling a highly efficient and continuous electrochemical reaction against lowering of the performance due to adsorption of excessive oxygen coexisting with a treating object, and Li is added to NiO in a nitrogen oxides eliminating part serving as a nitrophilous oxides eliminating field, to prevent lowering and deterioration of electric resistance. The electrochemical reactor can stabilize the operation of the elimination element compared to the conventional art, and can continuously treat the treating object with further less power consumption and high efficiency, even when excessive amount of oxygen inhibiting the chemical reaction of the treating object is present. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrochemical reactor that efficiently purifies nitrogen oxides from combustion exhaust gas containing oxygen, and more specifically, an electrode having mixed conductivity of ions and electrons on both sides sandwiching an ion conductive solid electrolyte. In addition, the present invention relates to an electrochemical element for purifying nitrogen oxides, to which a collecting electrode having electron conductivity and both are applied.

  The present invention prevents oxygen molecules coexisting in the exhaust gas from preferentially reacting with the electrodes of the electrochemical reactor when purifying nitrogen oxides in the exhaust gas, and is stable with less power consumption than the conventional technology. The present invention provides a new electrochemical reactor that makes it possible to purify a substance to be treated with high efficiency and continuously.

  Conventionally, nitrogen oxides generated from gasoline engines are detoxified by a three-way catalyst. However, when oxygen of more than several percent is present in exhaust gas, such as lean burn engines and diesel engines, the three-way catalyst surface. The problem is that the catalytic activity is reduced by oxygen poisoning.

  On the other hand, a solid electrolyte reactor system using a sintered body of an oxygen ion conductive oxide such as yttria stabilized zirconia has been proposed. This system is a method in which electrodes are provided on both sides of a solid electrolyte substrate having oxygen ion conductivity and an electric field is applied thereto.

  When an electric field is applied to this solid electrolyte reactor system, nitrogen oxides contained in the exhaust gas are reduced by electron donation from the cathode electrode at the cathode electrode-electrolyte-gas phase three-phase interface existing in the cathode electrode portion, Decomposed into oxygen ions and nitrogen.

  The decomposed oxygen ions diffuse through the solid electrolyte and are released as oxygen on the anode electrode. During the operation, the surface of the solid electrolyte in the cathode electrode portion is always in a state where oxygen is depleted, and the purification of nitrogen oxides in the exhaust gas is continuously performed.

  However, actual diesel exhaust gas contains oxygen at a concentration several tens to thousand times higher than that of nitrogen oxides. Therefore, for efficient purification of nitrogen oxides, it is necessary to decompose nitrogen oxides preferentially. Regarding this problem, it has been shown in an already-existing patent (Patent Document 1) that efficiency is improved by forming a mixture layer of nickel oxide and yttria-stabilized zirconia on the electrode surface of the electrochemical element.

  However, in general, the exhaust gas of diesel engines has oxygen of several percent or more, so the coexisting oxygen is preferentially ionized at the cathode electrode and flows through the solid electrolyte, so the nitrogen oxides are decomposed. In order to achieve this, it is necessary to pass a certain amount of current.

  The current efficiency of the above solid electrolyte type electrochemical device is about 10% at the maximum. Considering that the concentration ratio of nitrogen oxides and oxygen in exhaust gas is several tens to thousands times, it is very high nitrogen oxide selectivity, but about 90% of the current is used for pumping excess oxygen. The fact that it means the need for large power consumption, is a big obstacle to practical use.

  Furthermore, in the solid electrolyte type electrochemical device disclosed in the patent (Patent Document 1), the mixed layer for selective purification of nitrogen oxides deteriorates due to voltage fluctuations or instantaneous exhaustion of oxidizing gas, and the purification efficiency decreases. There is a problem of doing. For this reason, in actual operation, it is necessary to highly control voltage application in accordance with the concentration of the atmospheric gas.

JP 2003-33646 A

  In such a situation, in view of the above-described conventional technology, the present inventors can purify the object to be processed stably, highly efficiently and continuously with less power consumption than the conventional technology. As a result of intensive research with the goal of developing a new electrochemical reactor, the inventors succeeded in developing an electrochemical element that transmits stable operation against changes in atmosphere and fluctuations in operating conditions. It came to complete.

  The present invention has been made to solve the above-mentioned problems of the prior art, and is necessary for the purification of nitrogen oxides in the electrochemical device reaction electrode even when excess oxygen coexists in the exhaust gas. It is an object of the present invention to provide an electrochemical reactor that can reduce electric power and stably operate.

  In other words, the present invention achieves stable and highly efficient nitrogen oxide purification with less power consumption by improving the selectivity for nitrogen oxides in combustion exhaust gas, and against changes in atmosphere and operating conditions. It is an object of the present invention to provide an electrochemical device that can operate stably and stably.

The present invention for solving the above-described problems comprises the following technical means.
(1) An electrochemical element for performing an electrochemical reaction on an object to be processed, an electrochemical reactor having a basic cell structure composed of an ionic conductor and an electrode and having a chemical reaction part on the electrode An electrochemical reactor characterized in that a mesh electrode is formed on the upper part of the chemical reaction section.
(2) The electrochemical reactor according to (1), wherein the material of the mesh electrode is platinum, metal, or an electron conductive oxide material.
(3) The electrochemical reactor according to (1), wherein the mesh electrode has a shape having a resistance value in an in-plane direction lower than 1 Ωcm.
(4) The electrochemical reactor according to (1), wherein the object to be processed is nitrogen oxide.
(5) A composite of a solid electrolyte having oxygen ion conductivity or a mixed conductive material capable of conducting both oxygen ions and electrons and a metal oxide capable of electrochemically separating (reducing) oxygen. The electrochemical reactor according to (1) above, comprising:
(6) The electron conductivity is improved by adding Li, which is a donor element, to the reducible metal oxide contained in the electrode material, thereby promoting the electrochemical reduction reaction (5) ) Electrochemical reactor.
(7) The electrochemical reactor according to (6), wherein the amount of Li added to the metal oxide is 0.3 to 0.75 mol%.
(8) By applying an electric field to the electrochemical reactor, an increase in surface area due to metal fine particles generated by reduction of the metal oxide placed inside the electrode material forms a microstructure that improves the decomposition performance of the material to be treated. The electrochemical reactor according to (5) above.
(9) The electrochemical reactor according to (4), wherein the reducible metal oxide contained in the electrode material is NiO.
(10) A basic cell structure having a stabilized zirconia electrode having Pt + oxygen ion conductivity and a stabilized zirconia electrolyte having oxygen ion conductivity, and a stabilized zirconia catalyst layer having NiO-oxygen ion conductivity. The electrochemical reactor according to the above (1), which has a reticulated Pt electrode on the upper part of the chemical reaction part and an oxygen ion conductive stabilized zirconia coating layer on the electrode.
(11) By applying an electric field to the electrochemical reactor according to any one of (1) to (7) above, the metal oxide disposed inside the electrode material is reduced, and the surface area is increased by the production of metal fine particles. Forming a microstructure that increases the decomposition performance of the substance to be processed, and increasing the decomposition performance of the object to be processed.

Next, the present invention will be described in more detail.
The present invention is an electrochemical element for performing an electrochemical reaction on an object to be processed, and has a basic cell structure composed of an ionic conductor and an electrode, and an electrochemical device having a chemical reaction part on the electrode. The reactor is characterized in that a mesh electrode is formed above the chemical reaction part. In the present invention, a composite of a solid electrolyte having oxygen ion conductivity or a mixed conductive material capable of conducting both oxygen ions and electrons and a metal oxide capable of electrochemically separating (reducing) oxygen in the electrode. In order to improve the electron conductivity and promote the electrochemical reduction reaction by adding a donor or acceptor element to the reducible metal oxide contained in the electrode material and making it a semiconductor This is a preferred embodiment.

  Further, in the present invention, by applying an electric field to the electrochemical reactor, the increase in surface area due to the metal fine particles generated by reduction of the metal oxide disposed inside the electrode material improves the decomposition performance of the substance to be treated. Forming a microstructure, a basic cell structure having a stabilized zirconia electrode of Pt + oxygen ion conductivity and a stabilized zirconia electrolyte of oxygen ion conductivity, a stabilized zirconia catalyst layer of NiO-oxygen ion conductivity, It is a preferred embodiment that a reticulated Pt electrode is provided on the upper part of the chemical reaction portion composed of the above, and a stabilized zirconia coating layer having oxygen ion conductivity is provided thereon.

  As an embodiment of the present invention, as shown in FIG. 1, the electrochemical element is composed of a chemical reaction part for selectively reducing nitrogen oxides, an electrode layer, and a solid electrolyte layer having oxygen ion conductivity.

  The general mechanism for purifying nitrogen oxides is to first generate electrons from the electrode layer by energizing the electrochemical device, thereby ionizing the nitrogen oxides. Nitrogen atoms are released as molecules on the spot. The generated oxygen ions diffuse in the solid electrolyte layer having oxygen ion conductivity and are discharged as oxygen molecules at the opposite electrode layer. As this reaction occurs continuously, nitrogen oxides are decomposed and purified into nitrogen and oxygen.

  However, in general, exhaust gas from a diesel engine has oxygen of several percent or more, so the coexisting oxygen is preferentially ionized at the cathode electrode part and flows through the solid electrolyte. In order to decompose the oxide, it is necessary to pass a certain current or more.

  The current efficiency of the above solid electrolyte type electrochemical device is about 10% at the maximum. Considering that the concentration ratio of nitrogen oxides and oxygen in exhaust gas is several tens to thousands times, it is very high nitrogen oxide selectivity, but about 90% of the current is used for pumping excess oxygen. The fact that it means the need for large power consumption, is a big obstacle to practical use.

  Furthermore, in a solid electrolyte type electrochemical device such as the already disclosed patent (Japanese Patent Laid-Open No. 2003-33646) shown in FIG. 2, a chemical reaction that selectively purifies nitrogen oxides by voltage fluctuations or instantaneous depletion of oxidizing gas. NiO in the part undergoes excessive reduction, and large vacancies are formed. When the pores are formed, in the electrochemical element, the unpurified gas penetrates into the electrode part disposed below the chemical purification part, and oxygen is easily decomposed, and the nitrogen oxide of the electrochemical element There was a problem that the purification efficiency against the decrease. For this reason, in actual operation, it is necessary to highly control the voltage application in accordance with the concentration of the atmospheric gas.

  Therefore, the present inventors examined an electrode arrangement in which the purification efficiency does not decrease even when NiO in the chemical reaction section undergoes excessive reduction. As a result, by placing the mesh electrode on the upper part of the chemical reaction part, an electrode-solid electrolyte interface with a high oxygen decomposition activity is consciously formed in a part with higher resistance inside the electrochemical element, We succeeded in maintaining the decomposition efficiency of nitrogen oxides even if the structure of the material deteriorates.

  Further, the resistance of the cell increases due to the change in the electrode structure. As a method for reducing this, the study of semiconductor formation by adding Li to NiO in the chemical reaction part was examined. As a result, by adding about 0 to 1 mol% of Li to NiO, the increase in the electronic resistance in the chemical reaction part was reduced, and the purification efficiency of nitrogen oxides was successfully improved.

  The electrochemical device of the present invention has a basic cell structure composed of an ion conductor and an electrode, and in an electrochemical reactor in which a chemical reaction part is arranged on the electrode, a mesh electrode is formed on the upper part of the chemical reaction part. This is the basic configuration. In the electrochemical element of the present invention, a network electrode is formed on the upper part of the chemical reaction part of the electrochemical element, so that nitrogen oxide in the exhaust gas of the internal combustion engine can be efficiently converted into the reaction electrode as the nitrogen oxide purification treatment part. And stable purification.

  Conventionally, platinum has been used for electrodes because of the necessity of high-temperature firing in the chemical reaction part. However, in the case of mesh electrodes, low-temperature firing is possible depending on the arrangement of the electrodes. An oxide material or the like can be used.

  The shape of the mesh electrode is such that the resistance value in the in-plane direction is about 1 Ωcm or less, and it is desirable that the resistance value is lower. Ideally, the line width of the electrode is about 50 microns, and the distance between the net-like lines is about 1 mm to 1.5 mm. The line width of the electrode may be wide, but if the line width of the electrode is widened to reduce resistance, the amount of platinum used increases and the cost increases.

  Moreover, although it is possible to make the space | interval for every line narrower than 1 mm, since the area of an electrode-solid electrolyte interface increases, purification efficiency reduces. On the contrary, when the distance between the lines is 1.5 mm or more, the electronic resistance in the chemical reaction part to the intermediate point between the electrodes is increased, and a large distribution is generated in the reduction state in the in-plane direction of the chemical reaction part, Performance is not fully demonstrated.

  The amount of Li added to NiO in the chemical reaction part has a maximum purification efficiency between 0.3 and 0.75 mol%, as shown in an example (FIG. 5) described later. The resistance value of NiO decreases in proportion to the increase in the amount of Li added, but the purification efficiency does not increase in proportion to the resistivity alone, and the maximum efficiency is reached at an addition amount of about 0.5 mol%, and the addition amount is 0 High purification efficiency in the range of 3 to 0.75 mol%. And it became clear that the effect of addition was small when the addition amount was 0.75 mol% or more.

  In the conventional solid electrolyte type electrochemical device, NiO in the chemical reaction part that selectively purifies nitrogen oxides undergoes excessive reduction due to fluctuations in voltage and instantaneous depletion of oxidizing gas, and large vacancies are formed. However, the unpurified gas permeates into the electrode part disposed below the chemical purification part, so that oxygen is easily decomposed, and the purification efficiency of the electrochemical element with respect to nitrogen oxides is reduced.

  On the other hand, in the present invention, a reticulated electrode is arranged on the upper part of the chemical reaction part, so that an electrode having a high oxygen decomposition activity-solid electrolytic surface is formed in a portion having a higher resistance inside the electrochemical element, It is possible to maintain the nitrogen oxide decomposition efficiency even if the structure in the reaction section deteriorates, and realizes the purification process of nitrogen oxide stably, efficiently and with low power consumption. is there.

The present invention has the following effects.
(1) Even when there is an excessive amount of oxygen that interferes with the chemical reaction of the substance to be treated, the operation of the purification element can be stabilized, and the nitrogen oxide can be efficiently and continuously consumed with less power consumption than in the prior art. It is possible to provide a new electrochemical reactor capable of purifying water.
(2) It is possible to provide an electrochemical reactor having an electrode arrangement in which the purification efficiency does not decrease even when a metal oxide such as NiO in the chemical reaction section undergoes excessive reduction.
(3) By making semiconductor by adding Li or the like to NiO in the chemical reaction part, an increase in electronic resistance in the chemical reaction part can be reduced and the purification efficiency of nitrogen oxides can be improved.
(4) Critically high purification efficiency can be exhibited by setting the amount of Li added to NiO in the chemical reaction part in the range of 0.3 to 0.75 mol%.
(5) The amount of Pt used can be reduced, and the manufacturing cost of the element can be reduced.
(6) Since there is a portion that does not require high-temperature firing, energy in the (cathode electrode) firing process can be reduced.

  Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples. Examples of the present invention will be described below. FIG. 1 is a schematic view of an electrochemical device according to an embodiment of the present invention. Hereinafter, the case where nitrogen oxide is used as the material to be treated will be specifically described.

  An electrochemical device having the same structure as that shown in FIG. 1 was produced by the following method. As a solid electrolyte having oxygen ion conductivity, yttria-stabilized zirconia (8 mol% Y) was used, and a molded body having a diameter of 20 mm and a thickness of 0.5 mm was used. The nitrogen oxide selective reduction catalyst layer was printed on the above-described molded article by screen printing using a paste in which yttria-stabilized zirconia (8 mol% Y) and nickel oxide were mixed.

  The electrode is a mixture of platinum and yttria-stabilized zirconia on the nitrogen oxide purification side, a mesh electrode having a line width of 50 microns and a line interval of 1.25 mm on the nitrogen oxide selective reduction catalyst layer side, and an oxygen exhaust side. Each of the molded bodies was printed by screen printing in a solid coating shape.

  A coating layer was further formed by screen printing on the nitrogen oxide purification layer side of the formed body using the YSZ paste on the electrode. A platinum wire was connected to both electrodes of a product obtained by firing the molded body at 1400 ° C. for 2 hours and connected to a DC power source.

(Comparative Example 1)
A device having the same structure as that of FIG. 2 and having an improved device structure was manufactured by the following method. As a solid electrolyte having oxygen ion conductivity, yttria-stabilized zirconia (8 mol% Y) was used, and a molded body having a diameter of 20 mm and a thickness of 0.5 mm was used. A mixture paste of platinum and yttria-stabilized zirconia was printed on the electrodes by screen printing on both sides of the molded body.

  Thereafter, a paste obtained by mixing yttria-stabilized zirconia (8 mol% Y) and nickel oxide was used as a nitrogen oxide selective reduction catalyst layer, and was printed on the upper surface of the electrode of the above-described molded article by screen printing. Further, a coating layer was formed by screen printing on the nitrogen oxide purification layer of the compact using a YSZ paste. A platinum wire was connected to both electrodes of a product obtained by firing the molded body at 1400 ° C. for 2 hours and connected to a DC power source.

  An electrochemical device was produced in the same procedure as in Example 1 except that Li was added to NiO contained in the nitrogen oxide purification layer of the electrochemical device used in the experiment. 0.25 mol% of lithium nitrate is dissolved in ethanol with NiO powder, mixed with NiO powder, ball milled for 24 hours using ethanol as a dispersion medium, concentrated and dried with a rotary evaporator, and then fired at 900 ° C for 2 hours. This was pulverized to obtain Li-added NiO powder.

  This powder and yttria-stabilized zirconia (8 mol% Y) were mixed using polyethylene glycol to obtain a slurry. This slurry was applied as a nitrogen oxide selective reduction catalyst layer of the molded body, and an electrochemical device was obtained by the same procedure as in Example 1.

  Example 2 was the same as Example 2 except that the amount of Li added to the electrochemical device used in the experiment was changed. 0.5 mol% lithium nitrate is dissolved in ethanol with NiO powder, mixed with NiO powder, ball milled for 24 hours using ethanol as a dispersion medium, concentrated and dried with a rotary evaporator, and then fired at 900 ° C for 2 hours. This was pulverized to obtain Li-added NiO powder.

  This powder and yttria-stabilized zirconia (8 mol% Y) were mixed using polyethylene glycol to obtain a slurry. This slurry was applied as a nitrogen oxide selective reduction catalyst layer of the molded body, and an electrochemical device was obtained by the same procedure as in Example 1.

  Example 2 was the same as Example 2 except that the amount of Li added to the electrochemical device used in the experiment was changed. 0.75 mol% lithium nitrate is dissolved in ethanol with NiO powder, mixed with NiO powder, ball milled for 24 hours using ethanol as a dispersion medium, concentrated and dried with a rotary evaporator, and then fired at 900 ° C for 2 hours. This was pulverized to obtain Li-added NiO powder.

  This powder and yttria-stabilized zirconia (8 mol% Y) were mixed using polyethylene glycol to obtain a slurry. This slurry was applied as a nitrogen oxide selective reduction catalyst layer of the molded body, and an electrochemical device was obtained by the same procedure as in Example 1.

  Example 2 was the same as Example 2 except that the amount of Li added to the electrochemical device used in the experiment was changed. 1.0 mol% lithium nitrate is dissolved in ethanol with NiO powder, mixed with NiO powder, ball milled for 24 hours using ethanol as a dispersion medium, concentrated and dried with a rotary evaporator, and then fired at 900 ° C for 2 hours. This was pulverized to obtain Li-added NiO powder.

  This powder and yttria-stabilized zirconia (8 mol% Y) were mixed using polyethylene glycol to obtain a slurry. This slurry was applied as a nitrogen oxide selective reduction catalyst layer of the molded body, and an electrochemical device was obtained by the same procedure as in Example 1.

  Example 2 was the same as Example 2 except that the amount of Li added to the electrochemical device used in the experiment was changed. 1.5 mol% lithium nitrate is dissolved in ethanol with NiO powder, mixed with NiO powder, ball milled for 24 hours using ethanol as a dispersion medium, concentrated and dried with a rotary evaporator, and then fired at 900 ° C for 2 hours. This was pulverized to obtain Li-added NiO powder.

  This powder and yttria-stabilized zirconia (8 mol% Y) were mixed using polyethylene glycol to obtain a slurry. This slurry was applied as a nitrogen oxide selective reduction catalyst layer of the molded body, and an electrochemical device was obtained by the same procedure as in Example 1.

  The direct current voltage was applied between the electrodes of these electrochemical elements to evaluate the NOx purification performance. A schematic diagram of the evaluation apparatus is shown in FIG.

(Experimental result)
Using the samples of Example 1 and Comparative Example 1 under the measurement conditions shown in Table 1, a nitrogen oxide purification performance test was performed at an operating voltage of 2.5V. FIG. 4 shows the nitrogen oxide purification rate of each electrochemical element and the value of the current flowing through the electrochemical element. It can be seen that the electrochemical elements of the examples show an improvement in stability with respect to the elapsed time of nitrogen oxide purification compared to the comparative example.

  Using the samples of Examples 1-2 and Comparative Examples 2-5 under the measurement conditions shown in Table 2, a nitrogen oxide purification performance test was performed at operating voltages of 1.75 V and 2.15 V. FIG. 5 shows the nitrogen oxide purification rate of each electrochemical element and the current value flowing through the electrochemical element. It can be seen that the electrochemical element of the example improved the purification of nitrogen oxides by the addition of Li.

  FIG. 7 shows the current efficiency of nitrogen oxide purification calculated from FIG. Originally, as shown in FIG. 6, the electronic resistance decreases linearly in proportion to the amount of Li added, but the purification efficiency is not proportional to the electronic resistance, and when the amount of Li added is 0.5 mol%, the nitrogen oxides It became the maximum. Thus, it was found that the limited amount of Li added to NiO is effective in improving the purification efficiency of nitrogen oxides.

  As described in detail above, the present invention relates to an electrochemical reactor having an electrode for stable and high-efficiency operation. When purifying nitrogen oxides in exhaust gas according to the present invention, the present invention coexists in the exhaust gas. Oxygen molecules to be adsorbed on the reaction surface of the electrochemical reactor, resulting in a decrease in reactivity, while purifying nitrogen oxides stably, efficiently, and with less power consumption compared to conventional technologies It is possible to provide a new electrochemical reactor capable of. The present invention provides an electrochemical reactor capable of reducing and stably operating electric power required for purifying nitrogen oxides in an electrochemical element reaction electrode even when excess oxygen coexists in exhaust gas. Is. Furthermore, the present invention achieves high-efficiency purification of nitrogen oxides with low power consumption by improving the selectivity for nitrogen oxides in combustion exhaust gas. This is useful for providing an electrochemical device capable of stable operation.

The structure of an electrochemical element is shown. The structure of the conventional electrochemical element is shown. The schematic diagram of an evaluation apparatus is shown. The time dependence of NO purification characteristics is shown. The Li addition effect in NO purification performance is shown. The effect of the amount of Li addition on the electronic conductivity of NiO is shown. The Li addition effect in purification efficiency is shown.

Claims (11)

  An electrochemical device for performing an electrochemical reaction on an object to be processed, an electrochemical reactor having a basic cell structure composed of an ionic conductor and an electrode, and a chemical reaction section formed on the electrode. An electrochemical reactor characterized in that a mesh electrode is formed on the upper part of the chemical reaction part.   The electrochemical reactor according to claim 1, wherein the material of the mesh electrode is platinum, metal, or an electron conductive oxide material.   The electrochemical reactor according to claim 1, wherein the mesh electrode has a shape whose in-plane resistance value is lower than 1 Ωcm.   The electrochemical reactor according to claim 1, wherein the workpiece is nitrogen oxide.   The electrode includes a composite of a solid electrolyte having oxygen ion conductivity, or a mixed conductive material capable of conducting both oxygen ions and electrons, and a metal oxide capable of electrochemically separating (reducing) oxygen. The electrochemical reactor according to claim 1.   The electron conductivity is improved by adding Li, which is a donor element, to the reducible metal oxide contained in the electrode material, thereby promoting the electrochemical reduction reaction thereof. Electrochemical reactor.   The electrochemical reactor according to claim 6, wherein the amount of Li added to the metal oxide is 0.3 to 0.75 mol%.   By applying an electric field to the electrochemical reactor, an increase in the surface area due to metal fine particles generated by reduction of the metal oxide placed inside the electrode material formed a microstructure that improves the decomposition performance of the substance to be treated. Item 6. The electrochemical reactor according to Item 5.   The electrochemical reactor according to claim 4, wherein the reducible metal oxide contained in the electrode material is NiO.   A chemical reaction part comprising a basic cell structure having a stabilized zirconia electrode with Pt + oxygen ion conductivity and a stabilized zirconia electrolyte with oxygen ion conductivity, and a stabilized zirconia catalyst layer with NiO-oxygen ion conductivity The electrochemical reactor according to claim 1, further comprising a reticulated Pt electrode on the top of which has an oxygen ion conductive stabilized zirconia coating layer thereon.   By applying an electric field to the electrochemical reactor according to any one of claims 1 to 7, the metal oxide disposed inside the electrode material is reduced, and the surface area is increased by the generation of metal fine particles. A method for increasing the decomposition performance of an object to be processed, characterized by forming a microstructure that increases the decomposition performance.