ELECTRICALLY HEATED CATALYTIC CONVERTER AND METHOD FOR ITS MANUFACTURING

Abstract

Electrically heated catalytic converter comprising at least one conductive substrate (1) which includes a catalyst coating layer and an electrode element (5) fixed to the substrate (1), wherein a protective film (6) is formed on a surface of at least one part of the electrode element (5), wherein the protective film (6) is formed from i) Al2O3, ii) SiO2, iii) a composite material of Al2O3 and SiO2, or iv) a composite oxide which includes Al2O3, SiO2 or a composite material of Al2O3 and SiO2 as a main component, the protective film (6) has a design in which the entire part is formed from an amorphous structure, or in which a partially crystalline glass structure with a crystallization content of 30 vol.% or less is provided with reference to the entire part of the protective film, the thickness of the protective film (6) is in the range of 100 nm to 2 µm, the electrode element (5) is a single element made of a metal or a ceramic or a composite element made of a metal and a ceramic, the electrode element is formed with a surface electrode and a wiring fixing layer, and a porosity of the surface electrode and the wiring fixing layer is 5% or more.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to an electrically heated catalytic converter arranged in an exhaust system for exhaust gas, and a method for its production. 2. Description of the related art

[0002] Various industries have made diverse efforts globally to reduce environmental impacts. In particular, the automotive industry has advanced the development of technologies to promote not only gasoline-powered vehicles with superior fuel efficiency, but also so-called eco-cars, such as hybrid vehicles or electric vehicles, as well as to further improve vehicle performance.

[0003] Incidentally, in an exhaust system for exhaust gas by which a vehicle engine and a muffler are connected, an electrically heated catalytic converter (EHC) may be mounted which activates a catalyst for purifying exhaust gas as quickly as possible not only by purifying exhaust gas during normal operation but also by electrically heating the catalyst during a cold period.

[0004] In this electrically heated catalytic converter, for example, a pair of electrodes is attached to a honeycomb catalyst arranged in an exhaust system for exhaust gas, the pair of electrodes being connected by an external circuit including a power supply, the honeycomb catalyst being heated by causing a current to flow through the electrodes, and the activity of the honeycomb catalyst being improved so that the exhaust gas passing therethrough is detoxified.

[0005] For example, Japanese Patent Application Publication No. 2014-105694 (JP 2014-105694 A) discloses an example of an electrically heated catalytic converter including: a ceramic substrate (support) on which a catalyst is supported; a pair of surface electrode films extending in an axial direction of the substrate while facing each other on an outer peripheral surface of the substrate; comb-shaped wiring through which electric power is supplied to the surface electrode films from outside the electrically heated catalytic converter; and a plurality of wiring fixing layers that fix the wiring to the surface electrode films. In the electrically heated catalytic converter, the substrate is electrically heated by the surface electrode films.The surface electrode films, the comb-shaped wiring and the wiring fixing layers can be collectively referred to as the “electrode element”.

[0006] In order to protect the electrode element from an oxidizing atmosphere in a use environment, a protective film made of Cr2O3 or the like is formed on a surface of the electrode element, and the oxidation resistance temperature of such a protective film is lower than 1000°C.

[0007] However, the protective film of the electrode element constituting the electrically heated catalytic converter requires an oxidation resistance temperature of 1000°C or higher, and the development of a new protective film as an alternative to the protective film formed from Cr2O3 or the like is an urgent problem. JP 2014-105694 A also discloses an electrically heated catalytic converter including a protective film formed from Cr2O3.

[0008] The oxidation resistance temperature of a non-conductive material alternative to Cr2O3, such as Al2O3 or SiO2, is 1000°C or higher. However, since the atmospheric temperature at which the oxidation reaction of Al or Si as a metallic raw material occurs is extremely high at 1200°C or higher, a film formation process is required under a higher atmosphere than that of a protective film formed from Cr2O3 in a use environment.

[0009] Therefore, it is necessary to develop a technique capable of forming a protective film made of Al2O3, SiO2 or the like, which has a high oxidation resistance temperature, at as low an atmospheric temperature as possible.

[0010] Further prior art includes the publications US 9 273 582 B2, WO 2007 059 883 A1, and SCHMIDT, Helmut Karl: The Sol-Gel Process: Inorganic Synthesis Methods. In: Chemistry in Our Time, 2001, Volume 35, Issue 3, pp. 176-184. SUMMARY OF THE INVENTION

[0011] The invention provides: an electrically heated catalytic converter in which a protective film is formed that has excellent oxidation resistance at a high temperature of 1000°C or more; and a method for producing an electrically heated catalytic converter in which a protective film having a high oxidation resistance temperature of 1000°C or more can be formed at as low an atmospheric temperature as possible.

[0012] According to the invention, an electrically heated catalytic converter is provided, which includes at least one conductive substrate containing a catalyst coating layer and an electrode element fixed to the substrate, wherein a protective film is formed on a surface of at least a part of the electrode element. The protective film is formed of i) Al2O3, ii) SiO2, iii) a composite material of Al2O3 and SiO2, or iv) a composite oxide containing Al2O3, SiO2, or a composite material of Al2O3 and SiO2 as a main component. The protective film has a configuration in which the entire part is formed of an amorphous structure, or in which a partially crystalline glass structure with a crystallization ratio of 30 vol% or less based on the entire part of the protective film is provided, and a thickness of the protective film is in a range from 100 nm to 2 µm.The electrode element (5) is a single element made of a metal or a ceramic, or a composite element made of a metal and a ceramic. The electrode element is formed with a surface electrode and a wiring fixing layer, and the porosity of the surface electrode and the wiring fixing layer is 5% or more.

[0013] In the electrically heated catalytic converter according to the present invention, the protective film formed on the surface of the electrode member is made of i) Al2O3, ii) SiO2, iii) a composite material of Al2O3 and SiO2, or iv) a composite oxide including Al2O3, SiO2, or a composite material of Al2O3 and SiO2 as a main component. The protective film has a configuration in which the entire portion is formed of an amorphous structure or in which a partially crystalline glass structure with a crystallization ratio of 30 vol% or less based on the entire portion of the protective film is provided. As a result, the protective film has an oxidation resistance temperature of 1000°C or more. The protective film has an amorphous structure or a partially crystalline glass structure, and its thickness is in a range of 100 nm to 2 μm.As a result, the development of thermal stress is unlikely, and cracking of the protective film is therefore unlikely. The thickness of the protective film can range from 100 nm to 1 µm.

[0014] Here, "electrode element" includes a surface electrode film extending in an axial direction of a substrate on a surface of the substrate, a wiring through which electric power is supplied to the surface electrode film from outside the electrically heated catalytic converter, and a plurality of wiring fixing layers that fix the wiring to the surface electrode film. Typically, a pair of electrode elements are arranged and used on a surface of a substrate.

[0015] The protective film has a configuration in which the entire portion is formed of an amorphous structure, or in which a partially crystalline glass structure with a crystallization content of 30 vol% or less is provided relative to the entire portion of the protective film. That is, the protective film has no crystal structure or a small amount of crystal structure. Therefore, the Young's modulus or thermal expansion coefficient of the protective film can be kept low, and thus the protective film has crack resistance performance.

[0016] A protective film with a crystal structure may undergo a volume change at approximately a phase transition temperature (the phase transition temperature of SiO2 crystals is about 280°C, and the phase transition temperature of SiO2-Al2O3 crystals (mullite crystals) is about 970°C) and may form cracks due to this volume change.

[0017] If the thickness of the protective film exceeds 2 µm, the protective film becomes excessively hard, and the protective film may crack due to thermal expansion differences between the substrate and the comb-shaped wiring. If the thickness of the protective film is less than 100 nm, its gas barrier properties deteriorate. Therefore, the thickness of the protective film is defined to be in a range of 100 nm to 2 µm.

[0018] The conductive substrate may be electrically conductive and radiate heat, and may be, for example, a conductive ceramic such as SiC. The conductive substrate is a porous member having a plurality of pores, for example, having a triangular, quadrangular, or hexagonal shape, and is generally referred to as a honeycomb structure. The catalyst coating layer, in which a noble metal catalyst such as platinum or palladium is supported on an oxide carrier such as alumina, is formed on the surfaces of a plurality of cells of the substrate.

[0019] Examples of components of the electrically heated catalytic converter include: a substrate; for example, a pair of electrode elements; a cable by which the pair of electrode elements are connected; and an external circuit provided in the middle of the cable and including a power supply.

[0020] As a material of the substrate and a material of the surface electrode film and the wiring fixing layer constituting the electrode member, a ceramic material having a lower thermal expansion than a Ni-Cr thermal spray material described in JP 2014-105694 A is usable, and examples thereof include SiC, a composite material of SiC and Si, a composite material of SiC and MoSi2, a composite material of MoSi2 and Si, and a composite material (for example, boride or silicide) of SiC or the like and a conductive ceramic material.

[0021] The present inventors have verified that the protective film included in the electrically heated catalytic converter of the present invention has an oxidation resistance temperature of 1000°C or more, particularly 1000°C to 1100°C. The electrode element may be a single element made of a metal or a ceramic, or a composite element made of a metal and a ceramic. The electrode element is formed with a surface electrode and a wiring fixing layer. The electrode element may be a porous element in which a porosity of the surface electrode and the wiring fixing layer may be 5% or more. According to this configuration, the thermal expansion coefficients of the electrode element and the substrate are substantially equal, and thermal shock resistance can be increased when the electrically heated catalytic converter is actually used in a machine.The thermal expansion coefficients need only be substantially the same to the extent that the catalytic converter is not damaged by thermal shock caused by a different thermal expansion coefficient during actual use in a machine.

[0022] According to the present invention, a method for manufacturing an electrically heated catalytic converter is provided, wherein the electrically heated catalytic converter includes at least one conductive substrate having a catalyst coating layer and an electrode element fixed to the substrate, wherein a protective film is formed on a surface of at least a portion of the electrode element. This method includes: a first step of preparing a sol-gel solution by adding one of i) an Al2O3 nanomaterial, ii) an SiO2 nanomaterial, iii) a nanomaterial of a composite material of Al2O3 and SiO2, and iv) a nanomaterial of a composite oxide including Al2O3, SiO2, or a composite material of Al2O3 and SiO2 as a main component, to a solvent;and a second step of manufacturing the electrically heated catalytic converter by applying the sol-gel solution to a surface of at least a part of the electrode element, drying the sol-gel solution to form a coating film, and firing the coating film to form a protective film, wherein the electrode element (5) is a single element made of a metal or a ceramic or a composite element made of a metal and a ceramic, the electrode element is formed with a surface electrode and a wiring fixing layer, the electrode element (5) is a porous element in which a porosity of the surface electrode and the wiring fixing layer is 5% or more, and in the second step, a temperature during firing is in a range of 100°C to 200°C.;

[0023] By using the sol-gel solution prepared by adding one of i) an Al2O3 nanomaterial, ii) a SiO2 nanomaterial, iii) a nanomaterial of a composite material of Al2O3 and SiO2, and iv) a nanomaterial of a composite oxide containing Al2O3, SiO2, or a composite material of Al2O3 and SiO2 as a main component to a solvent, a firing temperature in a range of 100°C to 200°C is feasible during the formation of the protective film. Here, examples of "nanomaterial" include nanoparticles, nanofibers, and inorganic polymers.

[0024] The present inventors have found that in a case where the firing temperature is about 700°C, the film formation rate of the protective film is increased and residual stress is generated in the formed protective film, which is undesirable.

[0025] In the method according to the invention, the firing temperature during the formation of the protective film is defined in a range from 100°C to 200°C. In particular, by setting the temperature during firing in a relatively low temperature range of 100°C to 200°C, firing can be carried out at a slow heating rate.

[0026] By firing slowly in a temperature range of 100°C to 200°C, the protective film can be formed as uniformly as possible.

[0027] In this way, an Al2O3 nanomaterial, a SiO2 nanomaterial, or the like is used as a protective film material, and a sol-gel solution is used for a hydrolysis reaction to form the protective film. As a result, a dense protective film can be formed that has excellent gas barrier properties against O2 gas or the like.

[0028] As apparent from the above description, in the electrically heated catalytic converter and the method for manufacturing the same according to the present invention, the protective film formed on a surface of the electrode member is made of i) Al2O3, ii) SiO2, iii) a composite material of Al2O3 and SiO2, or iv) a composite oxide including Al2O3, SiO2 or a composite material of Al2O3 and SiO2 as a main component, the protective film has a configuration in which the entire part is formed of an amorphous structure or a partially crystalline glass structure having a crystallization ratio of 30 vol% or less with respect to the entire part of the protective film is provided, and a thickness of the protective film is in a range of 100 nm to 2 μm.As a result, the protective film can be formed at a firing temperature in a range of 100°C to 200°C, and the electrically heated catalytic converter including the protective film can be provided which has an oxidation resistance temperature of 1000°C or more and in which cracking and thermal stress are unlikely to occur. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Features, advantages, and technical and economic significance of exemplary embodiments of the invention are described below with reference to the accompanying drawings, wherein like reference numerals indicate like elements, and wherein: Fig. 1 is a schematic diagram showing an embodiment of an electrically heated catalytic converter (EHC) according to the present invention; Fig. Figure 2 is a schematic diagram showing a sample piece; Fig. 3A is a SEM image showing a section IIIa of Fig. 2 shows; Fig. 3B is an SEM image showing an enlarged view of a section b of Fig. 3A shows; Fig. Figure 4 is a graph showing the results of an oxidative degradation test; Fig. 5A is a graph showing an XRD profile of an Al2O3 film; and Fig. Figure 5B is a graph showing an XRD profile of a SiO2 film. DETAILED DESCRIPTION OF EMBODIMENTS

[0030] Hereinafter, an embodiment of an electrically heated catalytic converter according to the present invention and a method for manufacturing the same will be described with reference to the drawings. (Embodiment of an electrically heated catalytic converter and method for producing the same)

[0031] Fig. Figure 1 is a schematic diagram showing an embodiment of an electrically heated catalytic converter (EHC) according to the present invention. An electrically heated catalytic converter 10 shown in the drawing is incorporated in an exhaust system for exhaust gas. Specifically, in the exhaust system, an engine (not shown), the electrically heated catalytic converter (EHC) 10, a three-way catalytic converter (not shown), a sub-muffler (not shown), and a main muffler (not shown) are arranged in this order and connected to each other by a piping system.When the engine is started, a precious metal catalyst constituting the electrically heated catalytic converter 10 is heated to a predetermined temperature as quickly as possible, exhaust gas flowing out of the engine is purified by the precious metal catalyst, and a part of the exhaust gas not purified by the electrically heated catalytic converter 10 is purified by the three-way catalyst purifier positioned downstream of the electrically heated catalytic converter 10.

[0032] The electrically heated catalytic converter 10 is fixed by an external metal tube (metal casing; not shown) and a mat (holder; not shown) provided in a hollow portion of the external tube, and is configured as a whole to include: a substrate having a honeycomb structure in which a catalyst coating layer (not shown) is provided on surfaces of cell walls 1a; a cable (not shown) by which a pair of electrode elements 5 arranged on a surface of the substrate 1 are connected to each other; and an external circuit provided in the center of the cable and including a power supply (not shown). One electrode element of the pair of electrode elements 5 is connected to a positive terminal, and the other electrode element is connected to a negative terminal. The substrate 1 is electrically heated by supplying a current thereto through the electrode elements 5.

[0033] Each of the electrode elements 5 includes: a surface electrode film 2 disposed on a surface of the substrate 1; a comb-shaped wiring 3 disposed on a surface of the surface electrode film 2; and wiring fixing layers 4 to which a plurality of first wirings 3a included in the comb-shaped wiring 3 and extending in a circumferential direction of the substrate 1 are fixed.

[0034] The comb-shaped wiring 3 includes: a second wiring 3b extending in a longitudinal direction of the substrate 1; and the plurality of first wirings 3a branching from the second wiring 3b and extending in the circumferential direction of the substrate 1. The first wirings 3a and the second wiring 3b are electrically connected to the surface electrode film 2.

[0035] In a case where the power supply is turned on during engine start-up, a current is supplied to the pair of electrode elements 5 positioned at the center of the substrate 1, and a path extending along a diameter of a portion of the substrate 1 and a path extending linearly in a portion of the substrate 1 through the surface electrode film 2 are formed. In this way, due to a current diffusion function of the surface electrode film 2 constituting the electrode element 5, a current can be supplied to the entire portion of the substrate 1 as uniformly as possible, and the diffusion and rectification of an equal amount of current is realized.

[0036] In the substrate 1, an exhaust passage having a honeycomb structure including a plurality of cell walls 1a is formed, and a catalyst coating layer (not shown) is formed on the cell walls 1a. The catalyst coating layer is formed by causing a platinum group element such as palladium (Pd), rhodium (Rh), or platinum (Pt), or a compound of platinum group elements, to be supported on an oxide such as alumina (Al2O3), or causing another noble metal or a compound thereof to be supported on alumina or a ceria-zirconia (CeO2-ZrO2) composite oxide, adjusting this noble metal catalyst with alumina sol or water to prepare a slurry, and applying the slurry to the skeleton of the substrate using an impregnation method, an ion exchange method, a sol-gel method, a wash-coating method, or the like.

[0037] Exhaust gas flowing from the upstream side of the exhaust system for exhaust gas (X direction) is purified by the activity of the noble metal catalyst while flowing through the exhaust passage including the plurality of cell walls 1a, and the purified exhaust gas flows from the electrically heated catalytic converter 10 to the downstream side of the exhaust system.

[0038] First, the substrate 1 and the surface electrode film 2 and the wiring fixing layers 4 constituting the electrode element 5 are formed of a metal material or a ceramic material. For example, the substrate 1 may be formed of SiC, a composite material of SiC and Si, a composite material of SiC and Si, or a composite material of SiC and MoSi2. The surface electrode film 2 and the wiring fixing layers 4 constituting the electrode element 5 may be formed of a thermal spray material such as Ni-Cr, CrB-Si, MoSi2-Si, or TiB2-Si.

[0039] A protective film 6 is formed on a surface of the electrode member 5. The surface on which the protective film 6 is formed includes an area corresponding to a portion where the electrode member 5 is in contact with the substrate 1. The protective film 6 is formed of i) Al2O3, ii) SiO2, iii) a composite material of Al2O3 and SiO2, or iv) a composite oxide including Al2O3, SiO2, or a composite material of Al2O3 and SiO2 as a main component. The protective film 6 has a configuration in which the entire part is formed of an amorphous structure, or in which a partially crystalline glass structure with a crystallization ratio of 30 vol% or less based on the entire part of the protective film is provided. A thickness of the protective film is in a range from 100 nm to 2 µm.

[0040] The protective film 6 has a configuration in which the entire portion is formed of an amorphous structure, or in which a partially crystalline glass structure with a crystallization ratio of 30 vol% or less is provided relative to the entire portion of the protective film. That is, the protective film 6 has no crystal structure or a small amount of crystal structure. Therefore, the Young's modulus or thermal expansion coefficient of the protective film 6 can be kept low, and thus the protective film 6 has crack resistance performance.

[0041] Furthermore, by setting the thickness of the protective film 6 in a range of 100 nm to 2 μm, the generation of thermal stress is unlikely, and thus cracking of the protective film 6 is unlikely. It is preferable that the thickness of the protective film 6 be less than or equal to 1 μm to prevent cracking of the protective film 6.

[0042] Next, the method for manufacturing the electrically heated catalytic converter 10 will be described, focusing on a method for forming the protective film 6.

[0043] First, a sol-gel solution is prepared by adding one of i) an Al2O3 nanomaterial, ii) a SiO2 nanomaterial, iii) a nanomaterial of a composite material of Al2O3 and SiO2, and iv) a nanomaterial of a composite oxide containing Al2O3, SiO2 or a composite material of Al2O3 and SiO2 as a main component to a solvent containing water and alcohol (first step).

[0044] Next, the sol-gel solution is applied to a surface of the electrode element 5 and dried to form a coating film through a chemical reaction such as hydrolysis or condensation polymerization. Next, the coating film is baked at a temperature ranging from 100°C to 200°C to remove the remaining solvent and promote densification, thereby forming the protective film 6. As a result, the electrically heated catalytic converter 10 is manufactured (second step).

[0045] In this way, by using the sol-gel solution prepared by adding one of i) an Al2O3 nanomaterial, ii) a SiO2 nanomaterial, iii) a nanomaterial of a composite material of Al2O3 and SiO2, and iv) a nanomaterial of a composite oxide including Al2O3, SiO2 or a composite material of Al2O3 and SiO2 as a main component to a solvent, the firing temperature during the formation of the protective film 6 can be designed to be in a range of 100°C to 200°C.

[0046] The firing temperature is in a range of 100°C to 200°C, since firing can be carried out at a slow heating rate so that the protective film 6 can be formed as uniformly as possible.

[0047] Using this manufacturing method, the electrically heated catalytic converter 10 including the protective film 6 having an oxidation resistance temperature of 1000°C or more can be manufactured at as low an atmospheric temperature as possible, which is in a range of 100°C to 200°C. (Oxidative degradation test and its results)

[0048] The present inventors conducted an experiment to verify a relationship between oxidative degradation and the formation or non-formation of the protective film. Specifically, as shown in Fig. As shown in Figure 2, an electrode terminal D made of a Ni-Cr thermal spray material (thickness: 50 μm or less) was formed on a surface of a porous substrate K formed of SiC / Si to prepare a test piece TP. The porosity of the wiring fixing layer of the test piece TP was obtained based on image analysis of the cross-sectional image of the test piece TP. The obtained porosity was 14% or more. One of the following two protective films was formed on a surface of the electrode terminal D.

[0049] In Example 1, a protective film made of SiO2 (amorphous silicon dioxide) was formed. Regarding a method for forming the protective film, perhydropolysilazane (PHPS) as an inorganic polymer precursor was coated onto a surface of the electrode terminal using a dipping method in a reduced-pressure atmosphere, dried in air at 400°C for 1 hour, and fired in an N2 gas atmosphere at 500°C for 1 hour. The thickness of the protective film can be controlled by adjusting a diluted PHPS concentration and firing conditions.

[0050] In contrast, in Example 2, a protective film made of Al2O3 (amorphous alumina) was formed. Regarding a method for forming the protective film, an Al2O3 sol was applied to a surface of the electrode terminal using a dipping method in a reduced-pressure atmosphere and fired at 200°C in air for 2 hours. The thickness of the protective film can be controlled by adjusting a diluted concentration of the Al2O3 sol and firing conditions. As a comparative example to Examples 1 and 2, a sample was prepared that did not include a protective film.

[0051] As for a test procedure, each of the specimens was treated at 1000°C in air for 24 hours (aging treatment) to undergo oxidative degradation, and then its volume resistivity was measured.

[0052] The Fig. The sample TP shown in Figure 2 is coated with the protective film formed from Al2O3 (amorphous aluminum oxide) according to Example 2. Fig. Figure 3A is an SEM image showing a section IIIa of the specimen TP covered with the protective film formed from Al2O3, and Fig. Figure 3B is an SEM image showing an enlarged view of a section b of Fig. 3A shows. From Fig. Figure 3B shows that surfaces of primary particles were coated with the Al2O3 film.

[0053] Fig. Figure 4 shows the results of the oxidative degradation test. Fig. 4 it can be seen that in the comparative example the increase in the volume resistivity caused by the oxidative degradation is remarkably large compared to the initial state.

[0054] In contrast, it is evident that in Examples 1 and 2, the increase in the volume resistivity caused by oxidative degradation was extremely small compared to the initial state.

[0055] From the experiment, it is seen that by forming the protective film made of Al2O3 or amorphous SiO2 on the surface of the electrode terminal, a change in volume resistivity is suppressed and the oxidation resistance is improved.

[0056] Fig. Figure 5A shows an XRD profile of the Al2O3 film, and Fig. Figure 5B shows an XRD profile of the SiO2 film.

[0057] In the Fig. 5A and Fig. 5B shows no crystallinity-related peak, thus indicating that the films have an amorphous structure.

[0058] While the embodiments of the invention have been described above with reference to the drawings, specific configurations thereof are not specifically limited to the above-described embodiments. Within a range that does not deviate from the scope of the invention, design changes and the like may be made and are included within the scope of the invention.

Claims

[1] An electrically heated catalytic converter comprising at least one conductive substrate (1) having a catalyst coating layer and an electrode element (5) fixed to the substrate (1), wherein a protective film (6) is formed on a surface of at least a part of the electrode element (5), wherein the protective film (6) is formed from i) Al2O3, ii) SiO2, iii) a composite material of Al2O3 and SiO2, or iv) a composite oxide containing Al2O3, SiO2 or a composite material of Al2O3 and SiO2 as a main component, the protective film (6) has a configuration in which the entire part is formed from an amorphous structure, or in which a partially crystalline glass structure with a crystallization proportion of 30 vol% or less based on the entire part of the protective film is provided, a thickness of the protective film (6) is in a range from 100 nm to 2 µm, the electrode element (5) is a single element made of a metal or a ceramic or a composite element made of a metal and a ceramic, the electrode element is formed with a surface electrode and a wiring fixing layer, and a porosity of the surface electrode and the wiring fixing layer is 5% or more. [2] An electrically heated catalytic converter according to claim 1, wherein the conductive substrate (1) is a conductive ceramic including SiC as a main component. [3] A method for producing an electrically heated catalytic converter, wherein the electrically heated catalytic converter includes at least one conductive substrate (1) which includes a catalyst coating layer and an electrode element (5) fixed to the substrate (1), wherein a protective film (6) is formed on a surface of at least a part of the electrode element (5), and the procedure includes: a first step of preparing a sol-gel solution by adding one of i) an Al2O3 nanomaterial, ii) a SiO2 nanomaterial, iii) a nanomaterial of a composite material of Al2O3 and SiO2, and iv) a nanomaterial of a composite oxide containing Al2O3, SiO2 or a composite material of Al2O3 and SiO2 as a main component to a solvent; and a second step of producing the electrically heated catalytic converter by applying the sol-gel solution to a surface of at least a part of the electrode element (5), drying the sol-gel solution to form a coating film, and firing the coating film to form a protective film, wherein the electrode element (5) is a single element made of a metal or a ceramic or a composite element made of a metal and a ceramic, the electrode element (5) is formed with a surface electrode and a wiring fixing layer, the electrode element (5) is a porous element in which a porosity of the surface electrode and the wiring fixing layer is 5% or more, and in the second step, a temperature during firing is in a range of 100°C to 200°C. [4] The method according to claim 3, wherein the conductive substrate (1) is a conductive ceramic including SiC as a main component.

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