JP2020196944A - Reduction reaction electrode, and reaction device using the same - Google Patents
Reduction reaction electrode, and reaction device using the same Download PDFInfo
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Abstract
Description
本発明は、還元反応用電極、およびそれを用いた反応デバイスに関する。 The present invention relates to an electrode for a reduction reaction and a reaction device using the same.
太陽光エネルギーを用いて水（Ｈ２Ｏ）から水素（Ｈ２）、水（Ｈ２Ｏ）と二酸化炭素（ＣＯ２）から一酸化炭素（ＣＯ）、ギ酸（ＨＣＯＯＨ）、メタノール（ＣＨ３ＯＨ）等を合成する人工光合成に用いられる反応デバイスの技術が開示されている。これを実用化するためには、高い効率で反応を生じさせる反応用電極を実現することが望まれる。 Using solar energy, water (H 2 O) to hydrogen (H 2 ), water (H 2 O) and carbon dioxide (CO 2 ) to carbon monoxide (CO), formic acid (HCOOH), methanol (CH 3 OH) ) Etc. are disclosed. The technology of the reaction device used for artificial photosynthesis is disclosed. In order to put this into practical use, it is desired to realize a reaction electrode that causes a reaction with high efficiency.
反応デバイスでは、還元反応用電極と酸化反応用電極とが組み合わせて用いられる。例えば、特許文献１には、金属または半導体を含む基板と、当該基板の表面の少なくとも一部を覆い、構造体単体のサイズが１μｍ以下のカーボン素材からなるカーボン層と、当該カーボン層の表面を覆う錯体触媒層と、を備える還元反応用電極が開示されている。 In the reaction device, a reduction reaction electrode and an oxidation reaction electrode are used in combination. For example, Patent Document 1 describes a substrate containing a metal or a semiconductor, a carbon layer made of a carbon material that covers at least a part of the surface of the substrate and has a structure alone having a size of 1 μm or less, and the surface of the carbon layer. A reduction reaction electrode comprising a complex catalyst layer to cover is disclosed.
特許文献１に記載の技術を始めとして、多くの還元反応用電極の基材としては、ガラスに金属（Ａｇ，Ａｕ，Ｃｕ等）や半導体（ＴｉＯ２、ＺｎＯ、ＳＴｒＯ３等）等が塗布されたものが用いられている。 As the base material of many reduction reaction electrodes including the technique described in Patent Document 1, metal (Ag, Au, Cu, etc.), semiconductor (TiO 2 , ZnO, StrO 3, etc.) or the like is coated on glass. Is used.
高出力や多層化等を目的とした人工光合成デバイス等の反応デバイス用の還元反応電極では、使用する基材がガラスに金属や半導体が塗布されたものでは、特に大面積の電極では電極重量が重く、多層化した電極を一体化して構成するのが容易ではない。そのため、電極の基材の材料には、軽量であることが求められる。また、圧縮強度、導電性、耐食性、平滑性等も求められる。 In the reduction reaction electrode for reaction devices such as artificial photosynthesis devices for the purpose of high output and multi-layering, if the base material used is glass coated with metal or semiconductor, the electrode weight is particularly high for a large area electrode. It is not easy to integrate heavy and multi-layered electrodes. Therefore, the material of the base material of the electrode is required to be lightweight. Further, compressive strength, conductivity, corrosion resistance, smoothness and the like are also required.
さらに、ガラスに金属や半導体が塗布された基材は、集電線と接合する際に、直接基材に溶融金属等のはんだ接合が行われるが、基材と集電線との最適な接合強度を得るために、大面積の電極では導電性を確保するために集電のパターンを考慮したり、接合部位に必要な導電性を付加したりして複雑な工程が必要になっていた。 Furthermore, when a base material coated with metal or semiconductor is coated on glass, solder bonding of molten metal or the like is performed directly on the base material when joining with the current collector, but the optimum bonding strength between the base material and the current collector can be obtained. In order to obtain the large-area electrode, a complicated process is required, such as considering the pattern of current collection in order to secure the conductivity and adding the necessary conductivity to the joint portion.
本発明の目的は、多層化、大面積化、高出力化が可能な還元反応用電極、およびそれを用いた反応デバイスを提供することにある。 An object of the present invention is to provide a reduction reaction electrode capable of multi-layering, large area, and high output, and a reaction device using the same.
本発明は、炭素繊維と炭素との複合基材と、中間層と、触媒層と、を有する、還元反応用電極である。 The present invention is an electrode for a reduction reaction having a composite base material of carbon fibers and carbon, an intermediate layer, and a catalyst layer.
前記還元反応用電極において、前記中間層は、ポリマーとカーボン素材とを含む、または、カーボン素材から構成されることが好ましい。 In the reduction reaction electrode, the intermediate layer preferably contains a polymer and a carbon material, or is composed of a carbon material.
前記還元反応用電極において、前記触媒層は、炭素繊維と炭素との複合基材と、金属錯体とを含むことが好ましい。 In the reduction reaction electrode, the catalyst layer preferably contains a composite base material of carbon fibers and carbon and a metal complex.
前記還元反応用電極において、前記触媒層は、炭素繊維と炭素との複合基材と、カーボンナノチューブと、金属錯体とを含むことが好ましい。 In the electrode for reduction reaction, the catalyst layer preferably contains a composite base material of carbon fibers and carbon, carbon nanotubes, and a metal complex.
前記還元反応用電極において、前記金属錯体は、Ｒｕ錯体ポリマーであることが好ましい。 In the reduction reaction electrode, the metal complex is preferably a Ru complex polymer.
前記還元反応用電極において、前記複合基材は、金属錯体を含むことが好ましい。 In the reduction reaction electrode, the composite base material preferably contains a metal complex.
前記還元反応用電極において、前記炭素繊維と炭素との複合基材に、クリップで挟み込む接合により集電または給電を行うことが好ましい。 In the electrode for reduction reaction, it is preferable to collect or supply electricity to the composite base material of carbon fiber and carbon by sandwiching the composite base material with a clip.
本発明は、前記還元反応用電極と、酸化反応用電極と、を組み合わせて構成される、反応デバイスである。 The present invention is a reaction device configured by combining the reduction reaction electrode and the oxidation reaction electrode.
本発明により、多層化、大面積化、高出力化が可能な還元反応用電極、およびそれを用いた反応デバイスを提供することができる。 INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an electrode for a reduction reaction capable of having multiple layers, a large area, and a high output, and a reaction device using the same.
本発明の実施の形態について以下説明する。本実施形態は本発明を実施する一例であって、本発明は本実施形態に限定されるものではない。 Embodiments of the present invention will be described below. The present embodiment is an example of carrying out the present invention, and the present invention is not limited to the present embodiment.
［還元反応用電極］
図１は、本発明の実施形態に係る還元反応用電極の構成の一例を示す概略構成図である。図１の還元反応用電極１０は、炭素繊維と炭素との複合基材１２と、中間層１４と、触媒層１６と、を有する。還元反応用電極１０に電圧が印加されると、複合基材１２に生じた電荷が触媒層１６に渡され、触媒層１６における還元触媒反応、例えば、二酸化炭素（ＣＯ２）がギ酸（ＨＣＯＯＨ）に還元される反応に利用される。
[Electrodes for reduction reaction]
FIG. 1 is a schematic configuration diagram showing an example of the configuration of a reduction reaction electrode according to an embodiment of the present invention. The reduction reaction electrode 10 of FIG. 1 has a composite base material 12 of carbon fibers and carbon, an intermediate layer 14, and a catalyst layer 16. When a voltage is applied to the reduction reaction electrode 10, the charge generated in the composite base material 12 is transferred to the catalyst layer 16, and the reduction catalytic reaction in the catalyst layer 16, for example, carbon dioxide (CO 2 ) is formic acid (HCOOH). It is used for the reaction that is reduced to.
基板として用いる複合基材１２は、炭素繊維を含む。複合基材１２は、高温で熱処理された炭素繊維と炭素との複合体であり、例えば、カーボンペーパー、カーボンクロス等が挙げられる。カーボンペーパーは、例えば、ポリアクリロニトリル（ＰＡＮ）繊維等の有機繊維をポリビニルアルコールと水系媒体との分散液に含浸させ、約２０００℃で炭化させて結着させたものをシート状にしたものである。カーボンペーパーには、約２５質量％程度のテフロン（登録商標）系素材が含まれることもある。カーボンクロスは、有機繊維を焼成、炭化することで得られる炭素繊維を紡織したものである。カーボンペーパー、カーボンクロスは、多孔質体であり、無数の数十μｍ（１０μｍ〜１００μｍ程度）の細孔を有する。カーボンペーパー、カーボンクロスの厚さは、例えば、０．１ｍｍ〜０．４ｍｍ／１枚の範囲である。この複合基材１２としては、多層化（例えば、５〜１０層）されて厚みが約１０倍になった１ｍｍ〜４ｍｍの範囲のものを使用してもよい。多層化された複合基材は、例えば、接着剤として、導電性のカーボン素材、例えばグラファイトまたはグラフェンを含むポリマー（例えば、アクリルポリマー結合剤）を含むカーボン系接着剤を用いて複数のカーボンペーパー、カーボンクロス等を接着して積層することにより形成することができる。また、基板として、炭素繊維と炭素との複合基材に、Ｒｕ錯体ポリマー等の金属錯体を担持させたものを用いてもよい。 The composite base material 12 used as a substrate contains carbon fibers. The composite base material 12 is a composite of carbon fibers and carbon that has been heat-treated at a high temperature, and examples thereof include carbon paper and carbon cloth. The carbon paper is, for example, impregnated with an organic fiber such as polyacrylonitrile (PAN) fiber in a dispersion liquid of polyvinyl alcohol and an aqueous medium, carbonized at about 2000 ° C., and bound to form a sheet. .. The carbon paper may contain about 25% by mass of a Teflon (registered trademark) -based material. The carbon cloth is made by spinning carbon fibers obtained by firing and carbonizing organic fibers. The carbon paper and carbon cloth are porous bodies and have innumerable pores of several tens of μm (about 10 μm to 100 μm). The thickness of the carbon paper and the carbon cloth is, for example, in the range of 0.1 mm to 0.4 mm / sheet. As the composite base material 12, those in the range of 1 mm to 4 mm, which are multi-layered (for example, 5 to 10 layers) and have a thickness of about 10 times, may be used. The multi-layered composite substrate comprises a plurality of carbon papers using, for example, a carbon-based adhesive containing a conductive carbon material, for example, a polymer containing graphite or graphene (for example, an acrylic polymer binder) as an adhesive. It can be formed by adhering and laminating carbon cloth or the like. Further, as the substrate, a composite substrate of carbon fibers and carbon on which a metal complex such as a Ru complex polymer is supported may be used.
還元反応用電極に炭素繊維と炭素との複合基材１２を使用することにより、多層化、大面積化、高出力化が可能となる。基材が圧縮特性に優れ、軽量であるため、電極面方向をスタックして多層化（例えば、１０層以上）するのが容易である。そのため、反応デバイスの高出力化（高電流化）を達成することができる。炭素繊維と炭素との複合基材は軽量であるため、電極全体を軽くでき、大面積化も容易である。また、炭素繊維と炭素との複合基材は高導電性の確保ができ、多孔性であることから気孔率が高いので反応基質および反応生成物の流れが良好となり、水素発生等の副反応の抑制や炭素化合物の還元反応効率向上が達成されると考えられる。また、例えばｐＨ６．５〜７の電解液中でも耐食性に優れる。さらに、例えば複合基材の隙間にカーボン等のカーボン材料を充填することによって面方向の平滑性を容易に向上することができるため、表面平滑性にも優れる。 By using the composite base material 12 of carbon fiber and carbon for the electrode for the reduction reaction, it is possible to increase the number of layers, increase the area, and increase the output. Since the base material has excellent compression characteristics and is lightweight, it is easy to stack the electrode surface directions to form multiple layers (for example, 10 or more layers). Therefore, it is possible to achieve high output (high current) of the reaction device. Since the composite base material of carbon fiber and carbon is lightweight, the entire electrode can be made lighter and the area can be easily increased. In addition, the composite base material of carbon fiber and carbon can ensure high conductivity, and since it is porous, it has a high porosity, so that the flow of the reaction substrate and the reaction product is good, and side reactions such as hydrogen generation occur. It is considered that suppression and improvement of reduction reaction efficiency of carbon compounds are achieved. Further, for example, it has excellent corrosion resistance even in an electrolytic solution having a pH of 6.5 to 7. Further, for example, by filling the gaps between the composite base materials with a carbon material such as carbon, the smoothness in the surface direction can be easily improved, so that the surface smoothness is also excellent.
触媒層１６は、中間層１４を介して複合基材１２上に貼り合わせることができる。中間層１４は、例えば、ポリマーとカーボン素材とを含む接着層である。ポリマーとカーボン素材とを含む接着層は、接着剤として、導電性のカーボン素材、例えばグラファイトまたはグラフェンを含むポリマー（例えば、アクリルポリマー結合剤）を含むカーボン系接着剤を用いることにより形成することができる。中間層１４には、例えば、少なくとも直径が１μｍ以上１００μｍ以下のサイズのグラファイトまたはグラフェンを含むことが好適である。 The catalyst layer 16 can be attached onto the composite base material 12 via the intermediate layer 14. The intermediate layer 14 is, for example, an adhesive layer containing a polymer and a carbon material. The adhesive layer containing the polymer and the carbon material can be formed by using a carbon-based adhesive containing a conductive carbon material, for example, a polymer containing graphite or graphene (for example, an acrylic polymer binder) as the adhesive. it can. It is preferable that the intermediate layer 14 contains, for example, graphite or graphene having a diameter of at least 1 μm or more and 100 μm or less.
触媒層１６は、二酸化炭素還元反応等の還元反応の還元触媒を含む。触媒層１６は、複合基材１２と同様の炭素繊維と炭素との複合基材に還元触媒を担持させたものでもよいし、炭素繊維と炭素との複合基材の上に還元触媒を含む還元触媒層を形成したものでもよい。触媒層１６に、複合基材１２と同様の炭素繊維と炭素との複合基材を用いることによって、同種の材料を使用した電極形態であるために、電気化学特性が安定し、高電流化が可能となると考えられる。 The catalyst layer 16 contains a reduction catalyst for a reduction reaction such as a carbon dioxide reduction reaction. The catalyst layer 16 may be a composite base material of carbon fibers and carbon similar to the composite base material 12 on which a reduction catalyst is supported, or a reduction containing a reduction catalyst on the composite base material of carbon fibers and carbon. It may have a catalyst layer formed. By using the same carbon fiber and carbon composite base material as the composite base material 12 for the catalyst layer 16, the electrochemical properties are stable and the current can be increased because the electrode form uses the same type of material. It is thought that it will be possible.
還元触媒は、ルテニウム錯体等の金属錯体とすることが好適である。ルテニウム錯体としては、例えば、［Ｒｕ｛４，４’−ｄｉ（１−Ｈ−１−ｐｙｒｒｏｌｙｐｒｏｐｙｌ ｃａｒｂｏｎａｔｅ）−２，２’−ｂｉｐｙｒｉｄｉｎｅ｝（ＣＯ）（ＭｅＣＮ）Ｃｌ２］、［Ｒｕ｛４，４’−ｄｉ（１−Ｈ−１−ｐｙｒｒｏｌｙｐｒｏｐｙｌ ｃａｒｂｏｎａｔｅ）−２，２’−ｂｉｐｙｒｉｄｉｎｅ｝（ＣＯ）２Ｃｌ２］、［Ｒｕ｛４，４’−ｄｉ（１−Ｈ−１−ｐｙｒｒｏｌｙｐｒｏｐｙｌ ｃａｒｂｏｎａｔｅ）−２，２’−ｂｉｐｙｒｉｄｉｎｅ｝（ＣＯ）２］ｎ、［Ｒｕ｛４，４’−ｄｉ（１−Ｈ−１−ｐｙｒｒｏｌｙｐｒｏｐｙｌ ｃａｒｂｏｎａｔｅ）−２，２’−ｂｉｐｙｒｉｄｉｎｅ｝（ＣＯ）（ＣＨ３ＣＮ）Ｃｌ２］等が挙げられる。さらに、ルテニウム錯体は、Ｒｕ錯体モノマー（例えば［Ｒｕ｛４，４’−ｄｉ（１−Ｈ−１−ｐｙｒｒｏｌｙｐｒｏｐｙｌ ｃａｒｂｏｎａｔｅ）−２，２’−ｂｉｐｙｒｉｄｉｎｅ｝（ＣＯ）２Ｃｌ２］）と重合開始剤（例えばピロール）、重合触媒（例えば塩化鉄）を含むＲｕ錯体が高分子化（ポリマー）された状態のＲｕ錯体ポリマーであることが好ましい。 The reduction catalyst is preferably a metal complex such as a ruthenium complex. Examples of the ruthenium complex include [Ru {4,4'-di (1-H-1-pyrrolipropyl carbonate) -2,2'-bipyridine} (CO) (MeCN) Cl 2 ], [Ru {4,4 '-Di (1-H-1-pyrrolipyropyl carbonate) -2,2'-bipyridine} (CO) 2 Cl 2 ], [Ru {4,4'-di (1-H-1-pyrrolipyropyl carbonate) -2 , 2'-bipyridine} (CO) 2 ] n , [Ru {4,4'-di (1-H-1-pyrrolipropyl carbonate) -2,2'-bipyridine} (CO) (CH 3 CN) Cl 2 ] Etc. can be mentioned. Furthermore, the ruthenium complex is a polymerization initiator with a Ru complex monomer (for example, [Ru {4,4'-di (1-H-1-pyrrolipolypolymer) -2,2'-bipyridine} (CO) 2 Cl 2 ]). It is preferable that the Ru complex containing (for example, pyrrole) and a polymerization catalyst (for example, iron chloride) is a Ru complex polymer in a polymerized state.
還元触媒の担持は、例えば、Ｒｕ錯体ポリマー等の金属錯体（触媒）をアセトニトリル（ＭｅＣＮ）溶液に溶解した液（例えば、Ｒｕ錯体ポリマー溶液）を炭素繊維と炭素との複合基材の上に塗布、乾燥することで作製することができる。また、還元触媒の担持は、電解重合法により行うこともできる。例えば、作用極として複合基材の電極、対極にフッ素含有酸化スズ（ＦＴＯ）で被覆したガラス基板、参照電極にＡｇ／Ａｇ＋電極を用い、還元触媒を含む電解液中においてＡｇ／Ａｇ＋電極に対して負電圧となるようにカソード電流を流した後、Ａｇ／Ａｇ＋電極に対して正電位となるようにアノード電流を流すことにより複合基材上を還元触媒で担持することができる。電解質の溶液には、例えば、アセトニトリル（ＭｅＣＮ）、電解質には、例えば、Ｔｅｔｒａｂｕｔｙｌａｍｍｏｎｉｕｍｐｅｒｃｈｌｏｒａｔｅ（ＴＢＡＰ）を用いることができる。 To support the reduction catalyst, for example, a solution (for example, Ru complex polymer solution) in which a metal complex (catalyst) such as Ru complex polymer is dissolved in an acetonitrile (MeCN) solution is applied on a composite substrate of carbon fibers and carbon. It can be produced by drying. Further, the reduction catalyst can be supported by an electrolytic polymerization method. For example, the electrodes of a composite substrate as a working electrode, a glass substrate coated with fluorine-containing tin oxide (FTO) on the counter electrode, using Ag / Ag + electrode as a reference electrode, Ag / Ag + electrode in an electrolytic solution containing a reducing catalyst After a cathode current is passed so as to have a negative voltage with respect to the electrode, an anode current is passed so as to have a positive potential with respect to the Ag / Ag + electrode so that the composite substrate can be supported by the reduction catalyst. For the solution of the electrolyte, for example, acetonitrile (MeCN) can be used, and for the electrolyte, for example, Tetrabutylammioniumperchlate (TBAP) can be used.
触媒層１６は、マルチウォール・カーボンナノチューブ（ＭＷＣＮＴｓ）等のカーボンナノチューブ等のカーボン素材を含んでもよい。マルチウォール・カーボンナノチューブ（ＭＷＣＮＴｓ）等のカーボン素材を含ませることにより、ナノカーボンの３次元ネットワーク構造を形成することができる。マルチウォール・カーボンナノチューブとしては、少なくとも直径が１ｎｍ以上１００ｎｍ以下のものを含むことが好適である。マルチウォール・カーボンナノチューブ（ＭＷＣＮＴｓ）等のカーボン素材は、例えばエタノール等の溶媒にカーボン素材を高分散させたインクを用意して、ディップ塗布や含浸塗布等の方法によって塗布し、乾燥することにより、触媒層１６に含ませることができる。 The catalyst layer 16 may contain a carbon material such as carbon nanotubes such as multiwall carbon nanotubes (MWCNTs). By including a carbon material such as multiwall carbon nanotubes (MWCNTs), a three-dimensional network structure of nanocarbon can be formed. The multiwall carbon nanotubes preferably have a diameter of at least 1 nm or more and 100 nm or less. For carbon materials such as multiwall carbon nanotubes (MWCNTs), for example, an ink in which the carbon material is highly dispersed in a solvent such as ethanol is prepared, applied by a method such as dip coating or impregnation coating, and dried. It can be included in the catalyst layer 16.
例えば、図１１（ａ）に示すように、溶媒にＭＷＣＮＴｓ等のカーボン素材を分散させたカーボン素材分散液４２を炭素繊維と炭素との複合基材４０に含浸塗布、乾燥することにより複合基材／カーボン素材シート（例えば、ＣＰ／ＭＷＣＮＴｓシート）４４を得て、この複合基材／カーボン素材シート（例えば、ＣＰ／ＭＷＣＮＴｓシート）４４に、Ｒｕ錯体ポリマー溶液等の触媒溶液４６を含浸塗布、乾燥することにより、複合基材／カーボン素材／触媒シート（例えば、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシート）４８を得て、この複合基材／カーボン素材／触媒シート（例えば、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシート）４８を、ポリマーとグラファイト等のカーボン素材とを含む中間層（接着層）１４ａにより、炭素繊維と炭素との複合基材１２ａに接着接合して、複合基材１２ａと、ポリマーとカーボン素材とを含む接着層である中間層（接着層）１４ａと、触媒層（例えば、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰ）１６ａとを有する還元反応用電極１０を得ることができる。 For example, as shown in FIG. 11A, a carbon material dispersion liquid 42 in which a carbon material such as MWCNTs is dispersed in a solvent is impregnated into a composite base material 40 of carbon fibers and carbon, coated, and dried to form a composite base material. / Carbon material sheet (for example, CP / MWCNTs sheet) 44 is obtained, and the composite base material / carbon material sheet (for example, CP / MWCNTs sheet) 44 is impregnated with a catalyst solution 46 such as a Ru complex polymer solution, coated and dried. By doing so, a composite base material / carbon material / catalyst sheet (for example, CP / MWCNTs / RuCP sheet) 48 is obtained, and the composite base material / carbon material / catalyst sheet (for example, CP / MWCNTs / RuCP sheet) 48 is used. , An intermediate layer (adhesive layer) 14a containing a polymer and a carbon material such as graphite is used to bond and bond the composite base material 12a of carbon fibers and carbon, and the composite base material 12a and the polymer and the carbon material are bonded together. A reduction reaction electrode 10 having an intermediate layer (adhesive layer) 14a, which is a layer, and a catalyst layer (for example, CP / MWCNTs / RuCP) 16a can be obtained.
中間層１４は、カーボン素材から構成される層であってもよい。炭素繊維と炭素との複合基材１２がポーラスな構造である特長を生かして、例えば、図１１（ｂ）に示すように、溶媒にＭＷＣＮＴｓ等のカーボン素材を分散させたカーボン素材分散液４２を炭素繊維と炭素との複合基材４０に含浸塗布、乾燥することにより複合基材／カーボン素材シート（例えば、ＣＰ／ＭＷＣＮＴｓシート）４４を得て、この複合基材／カーボン素材シート（例えば、ＣＰ／ＭＷＣＮＴｓシート）４４を、ポリマーとグラファイト等のカーボン素材とを含む接着層５０により、炭素繊維と炭素との複合基材１２に接着接合して、その後、所定の温度（例えば２５０℃〜４５０℃）で所定の時間（例えば、０．５時間〜３時間）アニールを行い、最後に、Ｒｕ錯体ポリマー溶液等の触媒溶液４６を複合基材／カーボン素材シート（例えば、ＣＰ／ＭＷＣＮＴｓシート）４４上に塗布、乾燥することにより、複合基材１２ｂと、カーボン素材から構成される中間層１４ｂと、触媒層（例えば、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰ）１６ｂとを有する還元反応用電極１０ａを得ることができる。 The intermediate layer 14 may be a layer made of a carbon material. Taking advantage of the feature that the composite base material 12 of carbon fiber and carbon has a porous structure, for example, as shown in FIG. 11B, a carbon material dispersion liquid 42 in which a carbon material such as MWCNTs is dispersed in a solvent is used. The composite base material / carbon material sheet (for example, CP / MWCNTs sheet) 44 is obtained by impregnating and coating the composite base material 40 of carbon fiber and carbon and drying to obtain the composite base material / carbon material sheet (for example, CP). / MWCNTs sheet) 44 is adhesively bonded to the composite base material 12 of carbon fibers and carbon by an adhesive layer 50 containing a polymer and a carbon material such as graphite, and then at a predetermined temperature (for example, 250 ° C. to 450 ° C.). ) For a predetermined time (for example, 0.5 hour to 3 hours), and finally, a catalyst solution 46 such as a Ru complex polymer solution is applied onto the composite base material / carbon material sheet (for example, CP / MWCNTs sheet) 44. A reduction reaction electrode 10a having a composite base material 12b, an intermediate layer 14b made of a carbon material, and a catalyst layer (for example, CP / MWCNTs / RuCP) 16b can be obtained by coating and drying the material. ..
アニールを行うことにより、ポリマーとカーボン素材とを含む接着層５０においてポリマーが熱分解し、カーボン素材から構成される多孔質な中間層５２が得られる。その後、複合基材／カーボン素材シート（例えば、ＣＰ／ＭＷＣＮＴｓシート）４４上にＲｕ錯体ポリマー溶液等の触媒溶液４６を塗布、乾燥することにより、複合基材／カーボン素材シート（例えば、ＣＰ／ＭＷＣＮＴｓシート）４４だけではなく多孔質な中間層５２から複合基材１２にまでＲｕ錯体ポリマーが浸透し、炭素繊維と炭素との複合基材と、ＭＷＣＮＴｓ等のカーボン素材と、触媒（Ｒｕ錯体ポリマー等の金属錯体）とを含む触媒層１６ｂ；グラファイト等のカーボン素材から構成される中間層１４ｂ；触媒（Ｒｕ錯体ポリマー等の金属錯体）を含む複合基材１２ｂ；を有する還元反応用電極１０ｂを得ることができる。 By annealing, the polymer is thermally decomposed in the adhesive layer 50 containing the polymer and the carbon material, and a porous intermediate layer 52 composed of the carbon material is obtained. Then, a catalyst solution 46 such as a Ru complex polymer solution is applied onto the composite base material / carbon material sheet (for example, CP / MWCNTs sheet) 44 and dried to obtain the composite base material / carbon material sheet (for example, CP / MWCNTs). The Ru complex polymer permeates not only the sheet) 44 but also the porous intermediate layer 52 to the composite base material 12, and the composite base material of carbon fibers and carbon, the carbon material such as MWCNTs, and the catalyst (Ru complex polymer, etc.) A reduction reaction electrode 10b having a catalyst layer 16b containing (a metal complex of Ru complex); an intermediate layer 14b composed of a carbon material such as graphite; and a composite base material 12b containing a catalyst (a metal complex such as a Ru complex polymer); be able to.
図１１（ａ）の方法で得られる構成では、触媒層１６ａにおける中間層（接着層）１４ａとの界面付近の触媒はグラファイト等のカーボン素材に覆われてしまい、触媒の機能を発揮しにくくなり、また、触媒溶液４６としてＲｕ錯体ポリマー溶液を用いた場合、触媒層１６ａの表面に塩化鉄等の重合触媒が残存してしまうと考えられる。一方、図１１（ｂ）の方法で得られる構成では、触媒が触媒層１６ｂだけではなく中間層１４ｂ、複合基材１２ｂにまで電極のほぼ全域に含まれている。そのため、還元反応面積が増加して還元反応効率が向上し、高出力化（高電流化）が容易に達成されると考えられる。さらに、アニールを行うことにより、触媒層１６ｂと中間層１４ｂとの界面や中間層１４ｂと複合基材１２ｂとの界面の接合が安定化し、また、触媒層１６ｂの表面に残存する塩化鉄等の重合触媒の量が少なくなり、還元反応効率が向上すると考えられる。 In the configuration obtained by the method of FIG. 11A, the catalyst in the catalyst layer 16a near the interface with the intermediate layer (adhesive layer) 14a is covered with a carbon material such as graphite, which makes it difficult to exert the function of the catalyst. Further, when the Ru complex polymer solution is used as the catalyst solution 46, it is considered that a polymerization catalyst such as iron chloride remains on the surface of the catalyst layer 16a. On the other hand, in the configuration obtained by the method of FIG. 11B, the catalyst is contained not only in the catalyst layer 16b but also in the intermediate layer 14b and the composite base material 12b in almost the entire area of the electrode. Therefore, it is considered that the reduction reaction area is increased, the reduction reaction efficiency is improved, and high output (high current) is easily achieved. Further, by annealing, the bonding between the interface between the catalyst layer 16b and the intermediate layer 14b and the interface between the intermediate layer 14b and the composite base material 12b is stabilized, and iron chloride and the like remaining on the surface of the catalyst layer 16b are removed. It is considered that the amount of the polymerization catalyst is reduced and the reduction reaction efficiency is improved.
本構成の還元反応用電極１０ｂにおいて、例えば、金属錯体（Ｒｕ錯体ポリマー等）は、全体の約５〜３０質量％、例えば約２０質量％が複合基材１２ｂおよび中間層１４ｂに担持され、残りの約７０〜９５質量％、例えば約８０質量％は、触媒層１６ｂに担持されている。 In the reduction reaction electrode 10b having this configuration, for example, about 5 to 30% by mass, for example, about 20% by mass of the metal complex (Ru complex polymer or the like) is supported on the composite base material 12b and the intermediate layer 14b, and the rest. About 70 to 95% by mass, for example, about 80% by mass, is supported on the catalyst layer 16b.
接着層５０を形成する接着剤としては、導電性のカーボン素材、例えばグラファイトまたはグラフェンを含むポリマー（例えば、アクリルポリマー結合剤）を含むカーボン系接着剤を用いることができる。 As the adhesive forming the adhesive layer 50, a carbon-based adhesive containing a conductive carbon material, for example, a polymer containing graphite or graphene (for example, an acrylic polymer binder) can be used.
炭素繊維と炭素の複合基材１２に、金属板で挟み込む接合、例えばクリップ（挟み込む）接合により集電または給電を行うことができる（後述する図６参照）。これにより、機械的な加締め接合により接合強度が十分確保でき、安定した給電を行うことができる。また、複合基材１２は、全体が均一な材料で構成されていなくてもよく、リード線が接点部を介して接続される箇所が炭素繊維と炭素の複合基材１２で構成されていてもよい。 Current collection or power supply can be performed by joining the carbon fiber-carbon composite base material 12 by sandwiching it with a metal plate, for example, by clipping (sandwiching) joining (see FIG. 6 described later). As a result, sufficient joint strength can be secured by mechanical crimping joint, and stable power supply can be performed. Further, the composite base material 12 does not have to be made of a uniform material as a whole, and the portion where the lead wire is connected via the contact portion may be made of the composite base material 12 of carbon fiber and carbon. Good.
図３に、本発明の実施形態に係る還元反応用電極における複合基材と触媒層との接合形態の例を示す。なお、図３において、中間層１４は省略してある。図３（ａ）は、触媒層１６の片面に複合基材１２を接合した電極の例である。図３（ａ）に示すように、複合基材１２は、電極反応面を部分的に削除した構成としてもよい。また、図３（ｂ）に示すように、触媒層１６の両面に複合基材１２を接合した電極としてもよい。図３（ｂ）の構成においても、複合基材１２は、電極反応面を部分的に削除した構成としてもよい。図３（ｃ）に示すように、シート状の触媒層１６の側面に複合基材１２を接合した電極としてもよい。 FIG. 3 shows an example of a bonding form of the composite base material and the catalyst layer in the electrode for reduction reaction according to the embodiment of the present invention. In FIG. 3, the intermediate layer 14 is omitted. FIG. 3A is an example of an electrode in which the composite base material 12 is bonded to one side of the catalyst layer 16. As shown in FIG. 3A, the composite base material 12 may have a configuration in which the electrode reaction surface is partially removed. Further, as shown in FIG. 3B, the electrode may be an electrode in which the composite base material 12 is bonded to both surfaces of the catalyst layer 16. Also in the configuration of FIG. 3B, the composite base material 12 may have a configuration in which the electrode reaction surface is partially removed. As shown in FIG. 3C, the electrode may be an electrode in which the composite base material 12 is bonded to the side surface of the sheet-shaped catalyst layer 16.
シート状のカーボンペーパー等の複合基材１２とシート状の触媒層１６とを用いることによって、ともにシート状であるため、加工が極めて容易あり、図３（ｄ）に示すように、積層化した還元反応用電極とすることができる。このように、複合基材１２と触媒層１６とを有する還元反応用電極１０を組み合わせることによって、電極反応面積を拡大することができる立体的（３次元的）な集積電極構造が可能となる。 By using the composite base material 12 such as a sheet-shaped carbon paper and the sheet-shaped catalyst layer 16, the sheets are both in the form of a sheet, so that the processing is extremely easy. As shown in FIG. 3D, the layers are laminated. It can be used as an electrode for a reduction reaction. In this way, by combining the reduction reaction electrode 10 having the composite base material 12 and the catalyst layer 16, a three-dimensional (three-dimensional) integrated electrode structure capable of expanding the electrode reaction area becomes possible.
［反応デバイス］
本発明の実施形態に係る反応デバイスは、上記還元反応用電極と、酸化反応用電極と、を組み合わせて構成される反応デバイスである。反応デバイスは、例えば、二酸化炭素還元装置とすることができ、その二酸化炭素還元装置と、太陽電池セルと、を組み合わせた人工光合成装置とすることもできる。
[Reaction device]
The reaction device according to the embodiment of the present invention is a reaction device configured by combining the above-mentioned electrode for reduction reaction and the electrode for oxidation reaction. The reaction device can be, for example, a carbon dioxide reduction device, or an artificial photosynthesis device in which the carbon dioxide reduction device and a solar cell are combined.
二酸化炭素還元装置は、例えば、二酸化炭素の還元反応を進行させる上記還元反応用電極と、還元反応用電極と電気的に接続され、酸化反応を生起する酸化反応用電極と、が離間されて対向する位置に配置され、還元反応用電極と酸化反応用電極との間を、反応基質（二酸化炭素）を含む電解液が流れる流路を有する電気化学反応装置である。二酸化炭素還元装置は、例えば、二酸化炭素の還元反応を進行させる上記還元反応用電極と、還元反応用電極と電気的に接続され、酸化反応を生起する酸化反応用電極と、を有し、還元反応用電極および酸化反応用電極が反応基質（二酸化炭素）を含む電解液に浸漬されている装置であってもよい。 In the carbon dioxide reduction device, for example, the reduction reaction electrode for advancing the carbon dioxide reduction reaction and the oxidation reaction electrode electrically connected to the reduction reaction electrode to cause an oxidation reaction are separated from each other and face each other. It is an electrochemical reaction apparatus that is arranged at a position where the reaction substrate (carbon dioxide) is contained and has a flow path through which an electrolytic solution containing a reaction substrate (carbon dioxide) flows between the reduction reaction electrode and the oxidation reaction electrode. The carbon dioxide reduction apparatus has, for example, the above-mentioned electrode for reduction reaction for advancing the reduction reaction of carbon dioxide, and an electrode for oxidation reaction which is electrically connected to the electrode for reduction reaction and causes an oxidation reaction. The device may be a device in which the reaction electrode and the oxidation reaction electrode are immersed in an electrolytic solution containing a reaction substrate (carbon dioxide).
人工光合成装置は、上記二酸化炭素還元装置と、二酸化炭素還元装置の還元反応用電極および酸化反応用電極に供給される電力を生成する太陽電池セルと、を備える装置である。 The artificial photosynthesis device is a device including the carbon dioxide reduction device, a reduction reaction electrode of the carbon dioxide reduction device, and a solar cell that generates electric power supplied to the oxidation reaction electrode.
図２は、上記還元反応用電極を用いた反応デバイスの一例として人工光合成装置の構成の一例を示す概略構成図である。人工光合成装置１は、収容部２８内に二酸化炭素の還元反応を進行させる上記還元反応用電極１０と、酸化反応を生起する酸化反応用電極１８と、が離間されて対向する位置に配置され、還元反応用電極１０と酸化反応用電極１８との間を、反応基質を含む電解液が流れる流路２６を有する二酸化炭素還元装置３と、二酸化炭素還元装置３の還元反応用電極１０および酸化反応用電極１８に供給される電力を生成する太陽電池セル３０と、を備える装置である。 FIG. 2 is a schematic configuration diagram showing an example of the configuration of an artificial photosynthesis apparatus as an example of a reaction device using the reduction reaction electrode. The artificial photosynthesis apparatus 1 is arranged in the accommodating portion 28 at a position where the reduction reaction electrode 10 for advancing the carbon dioxide reduction reaction and the oxidation reaction electrode 18 for causing the oxidation reaction are separated from each other and face each other. A carbon dioxide reduction apparatus 3 having a flow path 26 through which an electrolytic solution containing a reaction substrate flows between the reduction reaction electrode 10 and the oxidation reaction electrode 18, the reduction reaction electrode 10 of the carbon dioxide reduction apparatus 3 and the oxidation reaction. It is a device including a solar cell 30 for generating power supplied to the electrode 18.
図２の例では、還元反応用電極１０および酸化反応用電極１８は、それぞれ複数の電極が積層化（スタック化）された構成となっている。還元反応用電極１０のみが積層化（スタック化）された構成でもよい。人工光合成装置とする場合には、還元反応用電極１０および酸化反応用電極１８がそれぞれ複数の電極が積層化（スタック化）された構成とすることが好ましい。 In the example of FIG. 2, the reduction reaction electrode 10 and the oxidation reaction electrode 18 each have a configuration in which a plurality of electrodes are stacked (stacked). A configuration in which only the reduction reaction electrodes 10 are stacked (stacked) may be used. In the case of an artificial photosynthesis apparatus, it is preferable that the reduction reaction electrode 10 and the oxidation reaction electrode 18 each have a plurality of electrodes laminated (stacked).
人工光合成装置１は、流路入口から還元反応用電極１０と酸化反応用電極１８との間の流路２６に二酸化炭素等の反応基質を含む電解液が導入されることによって機能する。電解液は流路出口から排出される。酸化反応用電極１８においては、水（Ｈ２Ｏ）が酸化されて酸素（１／２Ｏ２）が得られるとともに、電位が得られる。還元反応用電極１０においては、酸化反応を生起する電極から電位を得ることによって、例えば二酸化炭素が還元されてギ酸（ＨＣＯＯＨ）等が生成される。 The artificial photosynthesis apparatus 1 functions by introducing an electrolytic solution containing a reaction substrate such as carbon dioxide into the flow path 26 between the reduction reaction electrode 10 and the oxidation reaction electrode 18 from the flow path inlet. The electrolytic solution is discharged from the flow path outlet. In the oxidation reaction electrode 18, water (H 2 O) is oxidized to obtain oxygen (1 / 2 O 2 ) and an electric potential is obtained. In the reduction reaction electrode 10, formic acid (HCOOH) or the like is produced, for example, by reducing carbon dioxide by obtaining an electric potential from the electrode that causes an oxidation reaction.
（酸化反応用電極）
酸化反応用電極１８は、酸化反応によって物質を酸化するために利用される電極である。酸化反応用電極１８は、例えば、基板上に導電層が形成された基材２０とその上に形成された酸化触媒層２２とを含んで構成される。
(Electrode for oxidation reaction)
The oxidation reaction electrode 18 is an electrode used for oxidizing a substance by an oxidation reaction. The oxidation reaction electrode 18 is composed of, for example, a base material 20 having a conductive layer formed on a substrate and an oxidation catalyst layer 22 formed on the base material 20.
基板は、酸化反応用電極１８を構造的に支持する部材である。基板は、特に材料が限定されるものではないが、例えば、ガラス基板等が挙げられる。基板は、例えば、金属または半導体を含むものとしてもよい。基板として用いられる金属は、特に限定されるものではないが、例えば、銀（Ａｇ）、金（Ａｕ）、銅（Ｃｕ）、亜鉛（Ｚｎ）、インジウム（Ｉｎ）、カドミウム（Ｃｄ）、スズ（Ｓｎ）、パラジウム（Ｐｄ）、鉛（Ｐｂ）等が挙げられる。基板として用いられる半導体は、特に限定されるものではないが、例えば、酸化チタン（ＴｉＯ２）、酸化スズ（ＳｎＯ２）、シリコン（Ｓｉ）、チタン酸ストロンチウム（ＳｒＴｉＯ３）、酸化亜鉛（ＺｎＯ）、酸化タンタル（Ｔａ２Ｏ５）等が挙げられる。基板を金属または半導体を含むものとした場合、導電層と基板との間には絶縁層を形成することが好ましい。絶縁層は、特に限定されるものではないが、半導体の酸化物、窒化物や樹脂等が挙げられる。金属基板と導電体層とが電気的に直接接続されている構成としてもよい。酸化反応用電極１８を、透光性を有するようにするには、基板は、例えば、ガラス基板やプラスチック等とすることが好適である。基板として、還元反応用電極１０と同様の炭素繊維と炭素との複合基材を用いてもよい。これによって、軽量、高導電性の確保ができ、別途、導電層が不要になるという利点がある。 The substrate is a member that structurally supports the oxidation reaction electrode 18. The material of the substrate is not particularly limited, and examples thereof include a glass substrate. The substrate may include, for example, a metal or a semiconductor. The metal used as the substrate is not particularly limited, but for example, silver (Ag), gold (Au), copper (Cu), zinc (Zn), indium (In), cadmium (Cd), tin ( Sn), palladium (Pd), lead (Pb) and the like can be mentioned. The semiconductor used as the substrate is not particularly limited, but is, for example, titanium oxide (TiO 2 ), tin oxide (SnO 2 ), silicon (Si), strontium titanate (SrTiO 3 ), zinc oxide (ZnO). , Tantalum oxide (Ta 2 O 5 ) and the like. When the substrate contains a metal or a semiconductor, it is preferable to form an insulating layer between the conductive layer and the substrate. The insulating layer is not particularly limited, and examples thereof include semiconductor oxides, nitrides, and resins. The metal substrate and the conductor layer may be directly electrically connected to each other. In order for the oxidation reaction electrode 18 to have translucency, the substrate is preferably, for example, a glass substrate or plastic. As the substrate, a composite base material of carbon fiber and carbon similar to that of the reduction reaction electrode 10 may be used. This has the advantage that light weight and high conductivity can be ensured, and a separate conductive layer is not required.
導電層は、酸化反応用電極１８における集電を効果的にするために設けられる。導電層は、特に限定されるものではないが、例えば、酸化インジウム錫（ＩＴＯ）、フッ素ドープ酸化錫（ＦＴＯ）、酸化亜鉛（ＺｎＯ）等の透明導電層等が挙げられる。特に、熱的および化学的な安定性を考慮すると、フッ素ドープ酸化錫（ＦＴＯ）を用いることが好適である。 The conductive layer is provided in order to effectively collect current in the oxidation reaction electrode 18. The conductive layer is not particularly limited, and examples thereof include transparent conductive layers such as indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and zinc oxide (ZnO). In particular, considering thermal and chemical stability, it is preferable to use fluorine-doped tin oxide (FTO).
酸化触媒層２２は、酸化触媒機能を有する材料を含んで構成される。酸化触媒機能を有する材料としては、例えば、酸化イリジウム（ＩｒＯｘ）を含む材料等が挙げられる。酸化イリジウムは、ナノコロイド溶液として導電層の表面上に担持することができる（T.Arai et.al, Energy Environ. Sci 8, 1998 (2015)参照）。 The oxidation catalyst layer 22 is composed of a material having an oxidation catalyst function. Examples of the material having an oxidation catalyst function include a material containing iridium oxide (IrOx). Iridium oxide can be supported on the surface of the conductive layer as a nanocolloidal solution (see T. Arai et.al, Energy Environ. Sci 8, 1998 (2015)).
例えば、酸化イリジウム（ＩｒＯｘ）のナノコロイドを合成する。次に、２ｍＭの塩化イリジウム酸（ＩＶ）カリウム（Ｋ２ＩｒＣｌ６）水溶液５０ｍＬに１０ｗｔ％の水酸化ナトリウム（ＮａＯＨ）水溶液を加えてｐＨ１３に調整した黄色溶液を、ホットスターラを用いて９０℃で２０分加熱する。これによって得られた青色溶液を氷水で１時間冷却する。そして、冷やした溶液（２０ｍＬ）に３Ｍ硝酸（ＨＮＯ３）を滴下してｐＨ１に調整し、８０分撹拌し、酸化イリジウム（ＩｒＯｘ）のナノコロイド水溶液を得る。さらに、この溶液に１．５ｗｔ％ＮａＯＨ水溶液（１−２ｍＬ）を滴下してｐＨ１２に調整する。このようにして得られた酸化イリジウム（ＩｒＯｘ）のナノコロイド水溶液を、導電層上にｐＨ１２で塗布し、乾燥炉内において６０℃で４０分間保持して乾燥させる。乾燥後、析出した塩を超純水で洗浄し、酸化反応用電極１８を形成することができる。なお、酸化イリジウム（ＩｒＯｘ）のナノコロイド水溶液の塗布および乾燥を複数回繰り返してもよい。 For example, iridium oxide (IrOx) nanocolloids are synthesized. Next, a yellow solution adjusted to pH 13 by adding a 10 wt% sodium hydroxide (NaOH) aqueous solution to 50 mL of a 2 mM potassium iridium (IV) chloride (K 2 IrCl 6 ) aqueous solution was prepared at 90 ° C. using a hot stirrer. Heat for 20 minutes. The blue solution thus obtained is cooled with ice water for 1 hour. Then, 3M nitric acid (HNO 3 ) is added dropwise to the cooled solution (20 mL) to adjust the pH to 1, and the mixture is stirred for 80 minutes to obtain a nanocolloidal aqueous solution of iridium oxide (IrOx). Further, a 1.5 wt% NaOH aqueous solution (1-2 mL) is added dropwise to this solution to adjust the pH to 12. The nanocolloidal aqueous solution of iridium oxide (IrOx) thus obtained is applied onto the conductive layer at pH 12, and held in a drying oven at 60 ° C. for 40 minutes for drying. After drying, the precipitated salt can be washed with ultrapure water to form an electrode 18 for an oxidation reaction. The application and drying of the nanocolloidal aqueous solution of iridium oxide (IrOx) may be repeated a plurality of times.
なお、酸化反応用電極１８において基材として、還元反応用電極１０と同様の炭素繊維と炭素との複合基材を用いる場合には、例えば、酸化触媒として酸化イリジウム（ＩｒＯｘ）のナノコロイド水溶液を用いて、マルチウォール・カーボンナノチューブ（ＭＷＣＮＴｓ）等のカーボンナノチューブ等のカーボン素材を含んでもよいカーボンペーパー等の炭素繊維と炭素との複合基材に酸化触媒を担持して、そのシートを、カーボンペーパー等の炭素繊維と炭素との複合基材にカーボン系接着剤で接合したものを用いてもよい。 When a composite base material of carbon fiber and carbon similar to that of the reduction reaction electrode 10 is used as the base material in the oxidation reaction electrode 18, for example, a nanocolloid aqueous solution of iridium oxide (IrOx) is used as the oxidation catalyst. It may contain a carbon material such as carbon nanotubes such as multiwall carbon nanotubes (MWCNTs). An oxidation catalyst is supported on a composite base material of carbon fibers and carbon such as carbon paper, and the sheet is made of carbon paper. You may use the one bonded to the composite base material of carbon fiber and carbon with a carbon-based adhesive.
集電配線を、酸化反応用電極１８における集電の効果を高めるために設けてもよい。すなわち、酸化反応用電極１８を大面積化した場合、導電層のみでは酸化反応用電極１８の全面において十分な反応を促進させるための導電性を確保できなくなるので、酸化反応用電極１８の導電性を高めるために設けられる。集電配線は、例えば、間隔を置いて櫛形状に配置された線状のフィンガー電極と、フィンガー電極をさらに集電するためのバス電極とを組み合わせた構成とすることができる。集電配線は、導電部、第１シール部および第２シール部から構成することが好適である。導電部は、導電性の高い材料で構成され、金属を含む材料で構成することが好適である。例えば、銀（Ａｇ）、銅（Ｃｕ）等を含む材料で構成することが好適である。また、第１シール部および第２シール部は、導電部を化学的および機械的に保護するために少なくとも導電部の一部を被覆するように設けられる。第１シール部は、低融点のガラスコート材とすることができる。また、第２シール部は、シリコーンゴム（脱オキシムタイプ、低分子シロキサン低減材、耐油・耐溶剤フロロシリコーン等）、ポリイソブチレン、ポリプロピレン、メタクリル（アクリル）、ポリカーボネート、フッ素樹脂（テフロン（登録商標））、エポキシ樹脂等の樹脂とすることができる。 A current collecting wiring may be provided in order to enhance the effect of current collecting on the oxidation reaction electrode 18. That is, when the area of the oxidation reaction electrode 18 is increased, the conductivity for promoting a sufficient reaction cannot be ensured on the entire surface of the oxidation reaction electrode 18 only by the conductive layer. Therefore, the conductivity of the oxidation reaction electrode 18 is increased. It is provided to enhance. The current collecting wiring can be configured by combining, for example, linear finger electrodes arranged in a comb shape at intervals and a bus electrode for further collecting the finger electrodes. The current collecting wiring is preferably composed of a conductive portion, a first seal portion, and a second seal portion. The conductive portion is made of a highly conductive material, and is preferably made of a material containing a metal. For example, it is preferably composed of a material containing silver (Ag), copper (Cu) and the like. Further, the first seal portion and the second seal portion are provided so as to cover at least a part of the conductive portion in order to chemically and mechanically protect the conductive portion. The first sealing portion can be a glass coating material having a low melting point. The second seal is made of silicone rubber (deoxime type, low molecular weight siloxane reducing material, oil resistant / solvent resistant fluorosilicone, etc.), polyisobutylene, polypropylene, methacrylic (acrylic), polycarbonate, fluororesin (Teflon (registered trademark)). ), Resin such as epoxy resin can be used.
電解液に含まれる反応基質は、例えば、炭素化合物が挙げられ、例えば、二酸化炭素（ＣＯ２）とすることができる。また、電解液は、リン酸緩衝水溶液やホウ酸緩衝水溶液とすることが好適である。具体的な構成例では、例えば、二酸化炭素（ＣＯ２）飽和リン酸緩衝液のタンクを設け、ポンプによってこの溶液を還元反応用電極１０と酸化反応用電極１８との間に設けられた流路２６に供給し、還元反応によって生じたギ酸（ＨＣＯＯＨ）や酸素（Ｏ２）等を外部の燃料タンクに回収すればよい。 Examples of the reaction substrate contained in the electrolytic solution include carbon compounds, and for example, carbon dioxide (CO 2 ). Further, the electrolytic solution is preferably a phosphate buffered aqueous solution or a boric acid buffered aqueous solution. In a specific configuration example, for example, a tank of a carbon dioxide (CO 2 ) saturated phosphate buffer solution is provided, and this solution is supplied by a pump between the reduction reaction electrode 10 and the oxidation reaction electrode 18. Formic acid (HCOOH), oxygen (O 2 ), etc. generated by the reduction reaction may be recovered in an external fuel tank by supplying to 26.
収容部２８は、還元反応用電極１０および酸化反応用電極１８を支持するとともに、電解液が流れる流路２６を構成する部材である。収容部２８は、電気化学反応装置をセルとして構成するために必要な機械的な強度を備える材料で構成される。例えば、収容部２８は、金属、プラスチック等によって構成することができる。 The accommodating portion 28 is a member that supports the reduction reaction electrode 10 and the oxidation reaction electrode 18 and constitutes a flow path 26 through which the electrolytic solution flows. The housing 28 is made of a material having the mechanical strength required to form the electrochemical reactor as a cell. For example, the accommodating portion 28 can be made of metal, plastic, or the like.
還元反応用電極１０と酸化反応用電極１８との間に、液体と気体を分離し、プロトンを移動可能とするセパレータ２４を設けてもよい。セパレータ２４は、液体と気体を分離し、プロトンを移動可能とする材料のものであればよく、特に制限はないが、例えば、固体高分子電解膜であるナフィオン（登録商標）等を使用することができる。 A separator 24 may be provided between the reduction reaction electrode 10 and the oxidation reaction electrode 18 to separate the liquid and the gas and allow the protons to move. The separator 24 may be made of a material that separates liquid and gas and allows protons to move, and is not particularly limited. For example, Nafion (registered trademark), which is a solid polymer electrolyte membrane, may be used. Can be done.
還元反応用電極１０と酸化反応用電極１８との間を電気的に接続し、適切なバイアス電圧を印加した状態とする。バイアス電圧を印加する手段は、特に限定されるものではなく、化学的電池（一次電池、二次電池等を含む）、定電圧源、太陽電池セル等が挙げられる。このとき、酸化反応用電極１８に正極が接続され、還元反応用電極１０に負極が接続される。 The reduction reaction electrode 10 and the oxidation reaction electrode 18 are electrically connected to each other, and an appropriate bias voltage is applied. The means for applying the bias voltage is not particularly limited, and examples thereof include a chemical battery (including a primary battery, a secondary battery, etc.), a constant voltage source, a solar cell, and the like. At this time, the positive electrode is connected to the oxidation reaction electrode 18, and the negative electrode is connected to the reduction reaction electrode 10.
図２のように、バイアス電圧を印加する手段として太陽電池セル３０を用いることにより、二酸化炭素還元装置等の電気化学反応装置と、還元反応用電極および酸化反応用電極に供給される電力を生成する太陽電池セルと、を備える人工光合成装置とすることができる。バイアス電圧を印加する手段として太陽電池セルを用いる場合、太陽電池セルは、例えば、酸化反応用電極および還元反応用電極に隣接して配置することができる。例えば、還元反応用電極の背面に太陽電池セルを配置し、太陽電池セルの正極を酸化反応用電極に接続し、負極を還元反応用電極に接続すればよい。 As shown in FIG. 2, by using the solar cell 30 as a means for applying a bias voltage, electric power supplied to an electrochemical reaction device such as a carbon dioxide reduction device, a reduction reaction electrode, and an oxidation reaction electrode is generated. It can be an artificial photosynthesis device including a solar cell. When a solar cell is used as a means for applying a bias voltage, the solar cell can be arranged adjacent to, for example, an electrode for an oxidation reaction and an electrode for a reduction reaction. For example, the solar cell may be arranged on the back surface of the reduction reaction electrode, the positive electrode of the solar cell may be connected to the oxidation reaction electrode, and the negative electrode may be connected to the reduction reaction electrode.
二酸化炭素（ＣＯ２）からギ酸（ＨＣＯＯＨ）等を合成する場合、水（Ｈ２Ｏ）は酸化されて二酸化炭素（ＣＯ２）に電子とプロトンを供給する。ｐＨ７付近では水（Ｈ２Ｏ）の酸化電位は０．８２Ｖ、還元電位は−０．４１Ｖ（いずれも標準水素電極（ＮＨＥ））である。また、二酸化炭素（ＣＯ２）から一酸化炭素（ＣＯ）、ギ酸（ＨＣＯＯＨ）、メチルアルコール（ＣＨ３ＯＨ）への還元電位はそれぞれ−０．５３Ｖ，−０．６１Ｖ，−０．３８Ｖである。したがって、酸化電位と還元電位の電位差は１．２０〜１．４３Ｖである。炭素化合物である二酸化炭素（ＣＯ２）を還元する場合、太陽電池セルは、例えば４〜６枚の結晶系シリコン太陽電池を直接に接続した構成やアモルファスシリコン系３接合太陽電池とすることが好適である。 When synthesizing formic acid (HCOOH) or the like from carbon dioxide (CO 2 ), water (H 2 O) is oxidized to supply electrons and protons to carbon dioxide (CO 2 ). At around pH 7, the oxidation potential of water (H 2 O) is 0.82 V, and the reduction potential is −0.41 V (both are standard hydrogen electrodes (NHE)). The reduction potentials of carbon dioxide (CO 2 ) to carbon monoxide (CO), formic acid (HCOOH), and methyl alcohol (CH 3 OH) are -0.53V, -0.61V, and -0.38V, respectively. .. Therefore, the potential difference between the oxidation potential and the reduction potential is 1.20 to 1.43 V. When reducing carbon dioxide (CO 2 ), which is a carbon compound, it is preferable that the solar cell has, for example, a configuration in which 4 to 6 crystalline silicon solar cells are directly connected or an amorphous silicon 3-junction solar cell. Is.
太陽電池セルに対しては、受光面側に窓材設けることが好適である。窓材は、太陽電池セルを保護する部材である。窓材は、太陽電池セルにおいて発電に寄与する波長の光を透過する部材とし、例えば、ガラス、プラスチック等とすることができる。 For solar cells, it is preferable to provide a window material on the light receiving surface side. The window material is a member that protects the solar cell. The window material is a member that transmits light having a wavelength that contributes to power generation in the solar cell, and can be, for example, glass, plastic, or the like.
以下、実施例および比較例を挙げ、本発明をより具体的に詳細に説明するが、本発明は、以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.
［基材のみの電気化学評価］
ＦＴＯ（フッ素ドープ酸化スズ）ガラスと、カーボンペーパーについて、１５×１５ｍｍ角に切り出し、基材のみの電気化学評価を行った。
[Electrochemical evaluation of base material only]
FTO (fluorine-doped tin oxide) glass and carbon paper were cut into 15 × 15 mm squares, and the electrochemical evaluation of only the base material was performed.
電気化学評価は、３極式セル（対極：Ｐｔ、参照電極：飽和カロメル電極（ＳＣＥ））を用い、二酸化炭素ガス（ＣＯ２）ガスをバブリングして電解液に供給しながら、ポテンショスタット／ガルバノスタットにより行った。リニアスイープボルタンメトリー（ＬＳＶ）特性は、電極の電位を０．６Ｖから−１．５Ｖ（ｖｓ Ｈｇ／Ｈｇ２ＳＯ４）に掃引して測定し、電流−時間（ｉ−ｔ）特性は、電圧を−１．４Ｖ（ｖｓ Ｈｇ／Ｈｇ２ＳＯ４）の一定とし、３時間動作させて測定した。電解液として、０．４Ｍのリン酸バッファ水溶液（Ｋ２ＨＰＯ４＋ＫＨ２ＰＯ４）を使用した。 For electrochemical evaluation, a three-pole cell (counter electrode: Pt, reference electrode: saturated calomel electrode (SCE)) is used, and carbon dioxide gas (CO 2 ) gas is bubbled and supplied to the electrolytic solution while the potentiostat / galvanostat. It was done by stat. The linear sweep voltammetry (LSV) characteristic is measured by sweeping the electrode potential from 0.6V to -1.5V (vs Hg / Hg 2 SO 4 ), and the current-time (it) characteristic is the voltage. It was measured at a constant of −1.4 V (vs Hg / Hg 2 SO 4 ) and operated for 3 hours. As an electrolytic solution, a 0.4 M phosphate buffer aqueous solution (K 2 HPO 4 + KH 2 PO 4 ) was used.
その比較結果を図４に示す。図４（ａ）はＦＴＯガラスのＬＳＶ特性（横軸：電位（Ｖ）、縦軸：電流（ｍＡ））を示すグラフであり、（ｂ）はｉ−ｔ特性（横軸：時間（ｓｅｃ）、縦軸：電流（ｍＡ））を示すグラフである。図４（ｃ）はカーボンペーパーのＬＳＶ特性を示すグラフであり、（ｄ）はｉ−ｔ特性を示すグラフである。カーボンペーパーは、ＦＴＯガラスに比べて電流がＬＳＶ特性において約１／２（ａｔ −１．５Ｖ）であり、ｉ−ｔ特性（ａｔ −１．４Ｖ）においても約１／５も少ないことがわかる。 The comparison result is shown in FIG. FIG. 4A is a graph showing the LSV characteristics (horizontal axis: potential (V), vertical axis: current (mA)) of the FTO glass, and FIG. 4B is an it characteristic (horizontal axis: time (sec)). , Vertical axis: current (mA)). FIG. 4C is a graph showing the LSV characteristics of the carbon paper, and FIG. 4D is a graph showing the it characteristics. It can be seen that the current of carbon paper is about 1/2 (at-1.5V) in LSV characteristics and about 1/5 less in it characteristics (at-1.4V) than that of FTO glass. ..
なお、その他の金属の基材として、チタン粉末を焼結した基材、チタン繊維をメッシュにした基材と、チタンにＳｎメッキした基材（Ｓｎめっき厚：１μｍと１０μｍ）について、同様の評価を行った結果を図５に示す。図５（ａ）はチタン粉末を焼結した基材、チタン繊維をメッシュにした基材のＬＳＶ特性を、（ｂ）はｉ−ｔ特性を示すグラフであり、（ｃ）はチタンにＳｎメッキした基材のＬＳＶ特性を、（ｄ）はｉ−ｔ特性を示すグラフである。チタン系は、カーボンペーパーに比べて、一桁（約十倍）電流が高いことがわかる。チタンにＳｎメッキした基材は、カーボンペーパーより低電流であるが、−１．３Ｖ付近（図５（ｃ）のＬＳＶ参照）に急激なピークが見られ、Ｓｎと水素との水素化物ができやすいという問題点があることがわかった。 As other metal base materials, the same evaluation was performed for a base material obtained by sintering titanium powder, a base material made of titanium fibers meshed, and a base material Sn-plated on titanium (Sn plating thickness: 1 μm and 10 μm). The result of the above is shown in FIG. FIG. 5A is a graph showing the LSV characteristics of a base material obtained by sintering titanium powder and a base material made of titanium fibers as a mesh, FIG. 5B is a graph showing it characteristics, and FIG. 5C is a graph showing Sn plating on titanium. It is a graph which shows the LSV characteristic of the base material, and (d) shows the it characteristic. It can be seen that the titanium-based current has an order of magnitude (about ten times) higher current than carbon paper. The base material Sn-plated on titanium has a lower current than carbon paper, but a sharp peak is seen around -1.3 V (see LSV in FIG. 5 (c)), and a hydride of Sn and hydrogen is formed. It turns out that there is a problem that it is easy.
［基材との電気的接合方法の検討］
以下の実施例、比較例における基材との電気的接合方法は以下の通りである。板状の基材にカーボンペーパーを使用する場合の電極の給電方法の一例を図６に示す。ステンレス製のペーパークリップに集電線をはんだやカーボン系接着剤（導電性のグラファイトとポリマーを含む）で接合したものを用意した。このペーパークリップの先端を広げて、表面に触媒層を形成したカーボンペーパーを挟み込み、接触固定した。その後、接触固定した部分を、テフロン（登録商標）の刷毛を用いてシリコーンで被覆した。以下の実施例に示すように、ペーパー状の比較的薄い素材であるというカーボンペーパーの特長を生かして、炭素繊維と炭素の複合基材にクリップ（挟み込む）接合を使用して行うことにより、機械的な加締め接合により接合強度が十分確保でき、安定した給電を行うことができた。
[Examination of electrical bonding method with base material]
The method of electrical bonding with the base material in the following examples and comparative examples is as follows. FIG. 6 shows an example of an electrode power feeding method when carbon paper is used for the plate-shaped base material. We prepared a stainless steel paper clip with a collector wire bonded with solder or a carbon-based adhesive (including conductive graphite and polymer). The tip of this paper clip was spread out, and carbon paper having a catalyst layer formed on the surface was sandwiched and contact-fixed. Then, the contact-fixed portion was coated with silicone using a Teflon (registered trademark) brush. As shown in the following examples, by taking advantage of the feature of carbon paper that it is a relatively thin paper-like material, it is performed by using a clip (sandwiching) bond to a composite base material of carbon fiber and carbon. Sufficient joint strength could be secured by the appropriate crimping joint, and stable power supply could be performed.
［還元反応用電極の評価］
＜実施例１、比較例１＞
次に、溶媒（エタノール９５質量部）にマルチウォールカーボンナノチューブ（ＭＷＣＮＴｓ）５質量部を分散させたインクを用い、１５×２０ｍｍのカーボンペーパー（ＣＰ）にディップ塗布、３５０℃で乾燥することによって、ＣＰ／ＭＷＣＮＴｓシートを作製した。その後、カーボンペーパー（ＣＰ）（小型セル３ｃｍ２×６個分＝１８ｃｍ２）にＲｕ錯体ポリマー溶液（Ｒｕ錯体モノマー（［Ｒｕ｛４，４’−ｄｉ（１−Ｈ−１−ｐｙｒｒｏｌｙｐｒｏｐｙｌ ｃａｒｂｏｎａｔｅ）−２，２’−ｂｉｐｙｒｉｄｉｎｅ｝（ＣＯ）２Ｃｌ２］）０．６４１４ｇ、０．２２Ｍの塩化鉄（ＦｅＣｌ３）のエタノール溶液１．６５ｍＬ、０．７２ｍＭのピロールのアセトニトリル溶液０．３３ｍＬ、アセトニトリル６．３３ｍＬの混合溶液（総量８．３１ｍＬ））を塗布し、３０℃で３時間乾燥してＲｕ錯体を担持させ、マルチウォールカーボンナノチューブ（ＭＷＣＮＴｓ）を含有させたＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシート（触媒を担持した導電性ポリマーを含んだシート）を作製した。このＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシートを１５ｍｍ角に切り出して、１５×２０ｍｍのカーボンペーパー基材上にカーボン系接着剤（導電性のグラファイトとアクリルポリマー結合剤を含む）を用いて接着し、還元反応用電極を作製した。カーボンペーパー基材を給電部位のみに接合した場合（実施例１）と、カーボンペーパー基材を使用せず、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシートをそのまま使用した場合（比較例１）について、上述したｉ−ｔ特性評価と同様の評価を行った。ただし電極反応面積は１０ｍｍ角の１ｃｍ２とした。結果を図７（横軸：時間（ｓｅｃ）、縦軸：電流（ｍＡ））に示す。
[Evaluation of electrodes for reduction reaction]
<Example 1, Comparative Example 1>
Next, using an ink in which 5 parts by mass of multiwall carbon nanotubes (MWCNTs) are dispersed in a solvent (95 parts by mass of ethanol), a dip is applied to carbon paper (CP) of 15 × 20 mm, and the mixture is dried at 350 ° C. A CP / MWCNTs sheet was prepared. Then, in carbon paper (CP) (small cell 3 cm 2 x 6 = 18 cm 2 ), a Ru complex polymer solution (Ru complex monomer ([Ru {4,4'-di (1-H-1-pyrrolipropyl carbonate))- 2,2'-bipyridine} (CO) 2 Cl 2 ]) 0.6414 g, 0.22 M iron chloride (FeCl 3 ) ethanol solution 1.65 mL, 0.72 mM pyrrol acetonitrile solution 0.33 mL, acetonitrile 6 A .33 mL mixed solution (total volume 8.31 mL)) was applied and dried at 30 ° C. for 3 hours to support the Ru complex, and a CP / MWCNTs / RuCP sheet containing multiwall carbon nanotubes (MWCNTs) (catalyst). A sheet containing the carried conductive polymer) was prepared. This CP / MWCNTs / RuCP sheet is cut into 15 mm squares and adhered to a 15 x 20 mm carbon paper base material using a carbon-based adhesive (including conductive graphite and acrylic polymer binder) for reduction reaction. An electrode was prepared. The above-mentioned i-in the case where the carbon paper base material is bonded only to the feeding portion (Example 1) and the case where the CP / MWCNTs / RuCP sheet is used as it is without using the carbon paper base material (Comparative Example 1). The same evaluation as the t-characteristic evaluation was performed. However, the electrode reaction area was set to 1 cm 2 of 10 mm square. The results are shown in FIG. 7 (horizontal axis: time (sec), vertical axis: current (mA)).
図７は、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシートの還元反応面が片面にある電極の比較を示している。カーボンペーパーを給電部位のみに使用する（実施例１）と、カーボンペーパー基材なし（比較例１）に比べて、３倍程度に還元反応電流を増加することができた。 FIG. 7 shows a comparison of electrodes in which the reduction reaction surface of the CP / MWCNTs / RuCP sheet is on one side. When the carbon paper was used only for the feeding portion (Example 1), the reduction reaction current could be increased about three times as compared with the case without the carbon paper base material (Comparative Example 1).
＜実施例２、比較例２＞
実施例１、比較例１と同様にして、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシートの還元反応面が両面にある電極を作製して、給電部位におけるカーボンペーパーの有無の比較を行った結果を図８（横軸：時間（ｓｅｃ）、縦軸：電流（ｍＡ））に示す。カーボンペーパーを給電部位のみに接合する（実施例２）と、カーボンペーパー基材なし（比較例２）に比べて、初期の電流が２倍程度得られたが、３時間後には、１．３倍程度の電流増加となった。
<Example 2, Comparative Example 2>
In the same manner as in Example 1 and Comparative Example 1, electrodes having reduction reaction surfaces of CP / MWCNTs / RuCP sheets on both sides were prepared, and the result of comparing the presence or absence of carbon paper at the feeding site was shown in FIG. 8 (horizontal). Axis: time (sec), vertical axis: current (mA)). When the carbon paper was bonded only to the feeding portion (Example 2), the initial current was about twice as high as that without the carbon paper base material (Comparative Example 2), but after 3 hours, 1.3. The current increased by about twice.
なお、図７，８に示した給電部位のみに部分的にカーボンペーパー基材を接合して、電極の還元反応面が片面（実施例１）および両面（実施例２）にある構造形態は、図３に示す大面積化や積層化した電極作製を想定しているものである。 In addition, the structural form in which the carbon paper base material is partially bonded only to the feeding portion shown in FIGS. 7 and 8 and the reduction reaction surface of the electrode is on one side (Example 1) and both sides (Example 2) is It is assumed that the electrodes shown in FIG. 3 have a large area and are laminated.
＜実施例３，４＞
次に、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシートを用いて、カーボンペーパー基材を給電部位のみに接合する部分給電（実施例３）と、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシートのほぼ前面に接合する全面給電（実施例４）について、上述したｉ−ｔ特性評価と同様の評価を行った。比較評価した結果を図９（横軸：時間（ｓｅｃ）、縦軸：電流（ｍＡ））に示す。
<Examples 3 and 4>
Next, using the CP / MWCNTs / RuCP sheet, partial power feeding (Example 3) in which the carbon paper base material is joined only to the feeding portion, and full power feeding (Example 3) in which the carbon paper base material is joined to substantially the front surface of the CP / MWCNTs / RuCP sheet. Regarding 4), the same evaluation as the above-mentioned it characteristic evaluation was performed. The results of the comparative evaluation are shown in FIG. 9 (horizontal axis: time (sec), vertical axis: current (mA)).
ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシートへのカーボンペーパー基材の接合形態の違いにより、ｉ−ｔ特性が異なった。基材の全面接合（実施例４）は、部分接合（実施例３）に比べて高電流が得られ、安定していた。 The it characteristics differed due to the difference in the bonding form of the carbon paper base material to the CP / MWCNTs / RuCP sheet. In the full-face bonding of the base materials (Example 4), a higher current was obtained and stable as compared with the partial bonding (Example 3).
＜比較例３〜６＞
次に、カーボンペーパー基材以外の基材として、ＦＴＯガラス（比較例３）、チタン粉末を焼結した基材（比較例４）、チタン繊維をメッシュにした基材（比較例５）、チタンにＳｎメッキした基材（Ｓｎめっき厚：１０μｍ）（比較例６）をそれぞれ用いて、ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰシートを使用して実施例４と同様にして作製した電極を評価した結果を図１０（横軸：時間（ｓｅｃ）、縦軸：電流（ｍＡ））に示す（図９の実施例４の結果と比較参照）。いずれも、カーボンペーパー基材を使用した電極に比べて、ｉ−ｔ特性が悪く、時間経過に対して電流の低下がみられた。
<Comparative Examples 3 to 6>
Next, as a base material other than the carbon paper base material, FTO glass (Comparative Example 3), a base material obtained by sintering titanium powder (Comparative Example 4), a base material made of titanium fiber as a mesh (Comparative Example 5), and titanium. The results of evaluating the electrodes produced in the same manner as in Example 4 using CP / MWCNTs / RuCP sheets using each of the Sn-plated base materials (Sn plating thickness: 10 μm) (Comparative Example 6) are shown in FIG. (Horizontal axis: time (sec), vertical axis: current (mA)) (see comparison with the result of Example 4 in FIG. 9). In each case, the it characteristics were worse than those of the electrodes using the carbon paper base material, and the current decreased with the passage of time.
例えば実施例４のように、炭素繊維と炭素の複合基材と、カーボン系接着剤で接合された基材と同じ炭素繊維と炭素の複合基材と複合された触媒層とを用いることによって、同種の材料を使用した電極形態であるために、電気化学特性が安定し、高電流化が可能となると考えられる。 For example, as in Example 4, by using a composite base material of carbon fiber and carbon and a catalyst layer composited with a composite base material of carbon fiber and carbon which is the same as the base material bonded with a carbon-based adhesive. Since the electrode form uses the same type of material, it is considered that the electrochemical characteristics are stable and the current can be increased.
なお、基材の比抵抗は、チタン：０．１Ω／□、カーボンペーパー：約０．４Ω／□（厚さ方向８０ｍΩｃｍ、面方向４．７〜５．６ｍΩｃｍ）、ＦＴＯガラス：１０Ω／□である。 The resistivity of the base material is titanium: 0.1Ω / □, carbon paper: about 0.4Ω / □ (thickness direction 80mΩcm, surface direction 4.7 to 5.6mΩcm), FTO glass: 10Ω / □. is there.
＜実施例５＞
図１１（ｂ）に示すように、炭素繊維と炭素との複合基材がポーラスな構造である特長を生かして、実施例１とは異なる電極作製プロセスにより還元反応用電極を作製し、多孔質なカーボン構造体内部にＲｕ錯体ポリマーが浸透しやすくなり、電極内部にまでＲｕ錯体ポリマーが担持形成されやすくなるようにした。
<Example 5>
As shown in FIG. 11B, taking advantage of the feature that the composite base material of carbon fiber and carbon has a porous structure, an electrode for reduction reaction is prepared by an electrode manufacturing process different from that of Example 1, and the electrode is porous. The Ru complex polymer easily penetrates into the carbon structure, and the Ru complex polymer is easily supported and formed even inside the electrode.
溶媒（エタノール９５質量部）にマルチウォールカーボンナノチューブ（ＭＷＣＮＴｓ）５質量部を分散させたインクを用い、１５×２０ｍｍのカーボンペーパー（ＣＰ）にディップ塗布し、３５０℃で乾燥することによって、ＣＰ／ＭＷＣＮＴｓシートを３枚作製した。このＣＰ／ＭＷＣＮＴｓシートをそれぞれ１０ｍｍ角に切り出して、１５×２０ｍｍのカーボンペーパー基材上にカーボン系接着剤（導電性のグラファイトとアクリルポリマー結合剤を含む）を用いて接着接合して、その後、２５０℃３時間、３５０℃２時間、４５０℃０．５時間の各条件でアニールを行った。最後に、実施例１で用いたのと同様のＲｕ錯体ポリマー溶液をＣＰ／ＭＷＣＮＴｓシート上に塗布し、３０℃で３時間乾燥することにより、複合基材と、グラファイトから構成される中間層と、触媒層（ＣＰ／ＭＷＣＮＴｓ／ＲｕＣＰ）とを有する還元反応用電極を作製した。この還元反応用電極は、触媒層だけではなく基材（複合基材）および中間層にも、Ｒｕ錯体ポリマーが含まれる。 Using ink in which 5 parts by mass of multiwall carbon nanotubes (MWCNTs) are dispersed in a solvent (95 parts by mass of ethanol), dip-coat it on 15 x 20 mm carbon paper (CP), and dry it at 350 ° C. to CP / Three MWCNTs sheets were prepared. Each of the CP / MWCNTs sheets is cut into 10 mm squares and bonded to a 15 x 20 mm carbon paper substrate using a carbon-based adhesive (including conductive graphite and an acrylic polymer binder), and then adhesively bonded. Annealing was performed under the conditions of 250 ° C. for 3 hours, 350 ° C. for 2 hours, and 450 ° C. for 0.5 hours. Finally, a Ru complex polymer solution similar to that used in Example 1 was applied onto a CP / MWCNTs sheet and dried at 30 ° C. for 3 hours to form a composite substrate and an intermediate layer composed of graphite. , A reduction reaction electrode having a catalyst layer (CP / MWCNTs / RuCP) was prepared. In this reduction reaction electrode, the Ru complex polymer is contained not only in the catalyst layer but also in the base material (composite base material) and the intermediate layer.
この変更した電極作製プロセスにより、そのアニール温度条件（３条件）を変えて作製（ｎ＝２）した還元反応用電極について電気化学評価を行った結果を図１２に示す。図１２（ａ）はｉ−ｔ特性、図１２（ｂ）はＬＳＶ特性を示すグラフである。ｉ−ｔ測定では、アニール温度が２５０℃の場合に、実施例１の標準電極作製プロセスで作製した電極と同等の−５〜−７ｍＡ／ｃｍ２の電流が得られ、アニール温度を３５０℃および４５０℃にすると、−８．５〜−１１ｍＡ／ｃｍ２の高電流が得られた。 FIG. 12 shows the results of electrochemical evaluation of the electrode for reduction reaction produced (n = 2) by changing the annealing temperature condition (3 conditions) by this modified electrode fabrication process. FIG. 12A is a graph showing it characteristics, and FIG. 12B is a graph showing LSV characteristics. In the it measurement, when the annealing temperature was 250 ° C., a current of -5 to -7 mA / cm 2 equivalent to that of the electrode prepared in the standard electrode fabrication process of Example 1 was obtained, and the annealing temperature was 350 ° C. At 450 ° C., a high current of −8.5 to −11 mA / cm 2 was obtained.
＜参考例１＞
図１３には、実施例５の電極作製プロセスにおいてアニールなしの条件で作製した還元反応用電極の電気化学評価を行った結果を示す。アニールなしの条件の場合は、グラファイトとポリマーを含む接着層があるため、Ｒｕ錯体ポリマー溶液を塗布したときに電極の内部にＲｕ錯体ポリマー溶液が染み込みにくく、複合基材および中間層（接着層）にはＲｕ錯体ポリマーが含まれないと考えられ、アニールありの場合のＲｕ錯体ポリマーの担持構造と大きく異なっている。電流は、−３〜−４．５ｍＡ／ｃｍ２となり、アニールありの場合に比べて低下することが確認された。
<Reference example 1>
FIG. 13 shows the results of electrochemical evaluation of the electrode for reduction reaction prepared under the condition without annealing in the electrode fabrication process of Example 5. In the case of no annealing, since there is an adhesive layer containing graphite and polymer, it is difficult for the Ru complex polymer solution to soak into the inside of the electrode when the Ru complex polymer solution is applied, and the composite substrate and intermediate layer (adhesive layer) Is considered not to contain the Ru complex polymer, which is significantly different from the supported structure of the Ru complex polymer with annealing. The current was -3 to -4.5 mA / cm 2 , and it was confirmed that the current was lower than that with annealing.
図１４（ａ）に、実施例５および参考例１で作製した還元反応用電極の表面（触媒層側）のＳＥＭ写真（倍率：上から５００倍（スケールバー：５００μｍ）、１Ｋ倍（同５０μｍ）、５Ｋ倍（同１０μｍ）、１２Ｋ倍（同３μｍ））を示す。図１４（ｂ）に、電極内部のグラファイト部位（中間層）を想定してカーボンペーパーに接着剤を塗布、乾燥した表面のＳＥＭ写真（倍率：５００倍（スケールバー：５００μｍ））を示す。 FIG. 14A shows an SEM photograph of the surface (catalyst layer side) of the electrode for reduction reaction prepared in Example 5 and Reference Example 1 (magnification: 500 times from the top (scale bar: 500 μm), 1 K times (50 μm). ), 5K times (10 μm), 12K times (3 μm)). FIG. 14B shows an SEM photograph (magnification: 500 times (scale bar: 500 μm)) of a surface obtained by applying an adhesive to carbon paper assuming a graphite portion (intermediate layer) inside the electrode and drying the surface.
実施例５のアニールありの電極は、ポーラスであるが、アニール温度の上昇とともに、カーボンペーパー繊維部にＲｕ錯体ポリマーが十分に固着形成されている状況がみられる。電極内部のグラファイト部位を想定したＳＥＭ像から、アニール温度が４５０℃の場合には多数のクラックが見られ、実際の電極の内部のグラファイト部位も同様の状態になっていることが考えられる。このことから、適切なアニール温度を与えることにより、Ｒｕ錯体ポリマー溶液が電極の内部まで十分に担持乾燥しやすい構造ができると思われる。 The electrode with annealing in Example 5 is porous, but as the annealing temperature rises, a situation is observed in which the Ru complex polymer is sufficiently fixed and formed on the carbon paper fiber portion. From the SEM image assuming the graphite part inside the electrode, it is considered that many cracks are seen when the annealing temperature is 450 ° C., and the graphite part inside the actual electrode is in the same state. From this, it is considered that a structure in which the Ru complex polymer solution can be sufficiently supported and dried up to the inside of the electrode can be formed by giving an appropriate annealing temperature.
＜実施例６＞
４５０℃で０．５時間アニールした後のＲｕ錯体ポリマー溶液塗布の際に電極周辺のシリコーン被覆の部位が異なる電極を作製して、電気化学評価を行った。（１）実施例５で作製した還元反応用電極（Ｒｕ錯体ポリマー溶液塗布の際にシリコーン被覆なし）と、（２）Ｒｕ錯体ポリマー溶液塗布の際に１０ｍｍ角の触媒層表面と基板（複合基材）裏側以外の部分を全てシリコーン被覆して作製した電極と、（３）Ｒｕ錯体ポリマー溶液塗布の際に１０ｍｍ角の触媒層表面以外の部分を基板（複合基材）裏側まで全てシリコーン被覆して作製した電極と、について、電気化学評価を行った。図１５に結果を示す。
<Example 6>
When the Ru complex polymer solution was applied after annealing at 450 ° C. for 0.5 hours, electrodes having different silicone-coated sites around the electrodes were prepared and electrochemically evaluated. (1) Electrodes for reduction reaction prepared in Example 5 (without silicone coating when coated with Ru complex polymer solution), and (2) Surface and substrate (composite group) of 10 mm square catalyst layer when coated with Ru complex polymer solution. Material) An electrode prepared by coating all parts other than the back side with silicone, and (3) when applying a Ru complex polymer solution, all parts other than the surface of the catalyst layer of 10 mm square are coated with silicone up to the back side of the substrate (composite base material). Electrochemical evaluation was performed on the prepared electrodes. The results are shown in FIG.
次に、（４）Ｒｕ錯体ポリマー溶液を用いてカーボンペーパーに塗布、乾燥することによって１５ｍｍ角にＲｕ錯体ポリマーを担持させた複合基材を基板として用いて実施例１と同様にして作製した還元反応用電極と、（５）カーボンペーパーの裏面をシリコーンで被覆してからＲｕ錯体ポリマー溶液を用いて塗布、乾燥した複合基材を基板として用いて実施例１と同様にして作製した還元反応用電極について、電気化学評価を行った。図１６に結果を示す。 Next, (4) a reduction produced in the same manner as in Example 1 using a composite substrate having a Ru complex polymer supported in a 15 mm square by applying and drying to carbon paper using a Ru complex polymer solution as a substrate. For reduction reaction prepared in the same manner as in Example 1 using the reaction electrode and (5) the back surface of carbon paper coated with silicone, coated with a Ru complex polymer solution, and dried using a composite substrate as a substrate. Electrochemical evaluation was performed on the electrodes. The results are shown in FIG.
図１５，１６に示す結果の電流値を基に、実施例５の電極作製プロセスにより作製した電極のＲｕ錯体ポリマーの担持割合を推定した。図１７に結果を示す。図１５に示した（１）と（２）とが同等の−９ｍＡ／ｃｍ２であり、（３）が−６ｍＡ／ｃｍ２であることより、基板部のＲｕ錯体ポリマーの担持有無の違いは−３ｍＡ／ｃｍ２であった。実際に、図６に基板部のみにＲｕ錯体ポリマーを担持した評価結果（（４），（５））からも同等の−２．５ｍＡ／ｃｍ２（−２〜−２．５ｍＡ／ｃｍ２）の電流値を得た。これまでの知見からＲｕ錯体ポリマーの担持量（担持面積）と電気化学評価の電流値には相関があることから、触媒層には電極全体のＲｕ錯体ポリマーのうち約８０質量％相当が担持され、基板（複合基材）および中間層には電極全体のＲｕ錯体ポリマーのうち約２０質量％相当が担持されていると推定される。 Based on the current values of the results shown in FIGS. 15 and 16, the carrying ratio of the Ru complex polymer of the electrode prepared by the electrode fabrication process of Example 5 was estimated. The results are shown in FIG. Since (1) and (2) shown in FIG. 15 are equivalent to -9 mA / cm 2 and (3) is -6 mA / cm 2 , the difference in whether or not the Ru complex polymer is supported on the substrate is different. It was -3 mA / cm 2 . Actually, from the evaluation results ((4) and (5)) in which the Ru complex polymer was supported only on the substrate portion in FIG. 6, it was equivalent to -2.5 mA / cm 2 (-2 to -2.5 mA / cm 2 ). The current value of was obtained. Since there is a correlation between the amount of Ru complex polymer supported (supported area) and the current value of the electrochemical evaluation from the findings so far, about 80% by mass of the Ru complex polymer of the entire electrode is supported on the catalyst layer. It is estimated that about 20% by mass of the Ru complex polymer of the entire electrode is supported on the substrate (composite base material) and the intermediate layer.
＜実施例７＞
図１８に、さらなる高電流化を目指し、カーボン系接着剤（導電性のグラファイトとアクリルポリマー結合剤を含む）を用いて、基板のカーボンペーパーを２枚または３枚の接着構造として、実施例５と同様の電極作製プロセスにより作製した還元反応用電極の電気化学評価結果を示す。カーボンペーパー１枚で−９ｍＡ／ｃｍ２の電流、カーボンペーパー２枚で−１０〜−１０．５ｍＡ／ｃｍ２の電流、カーボンペーパー３枚で−１１．５〜−１２ｍＡ／ｃｍ２の電流が得られ、カーボンペーパーの枚数増加とともに電流が増加した。これは、基板であるカーボンペーパーへのＲｕ錯体ポリマーの担持面積の増加が電流増加に寄与しているためと考えられる。
<Example 7>
In FIG. 18, in order to further increase the current, a carbon-based adhesive (including conductive graphite and an acrylic polymer binder) is used to form two or three carbon papers on the substrate as an adhesive structure in Example 5. The electrochemical evaluation result of the electrode for reduction reaction prepared by the same electrode fabrication process as above is shown. The resulting current of -9mA / cm 2 with a single carbon paper, current -10 to-10.5 mA / cm 2 in two carbon paper, with three carbon paper current -11.5~-12mA / cm 2 is As a result, the current increased as the number of carbon papers increased. It is considered that this is because the increase in the supported area of the Ru complex polymer on the carbon paper which is the substrate contributes to the increase in the current.
以上のように、実施例のように炭素繊維と炭素との複合基材を用いることによって、多層化、大面積化、高出力化が可能な還元反応用電極が得られた。 As described above, by using the composite base material of carbon fiber and carbon as in the example, an electrode for reduction reaction capable of multi-layering, large area, and high output was obtained.
１ 人工光合成装置、３ 二酸化炭素還元装置、１０，１０ａ，１０ｂ 還元反応用電極、１２，１２ａ，１２ｂ，４０ 複合基材、１４，１４ｂ，５２ 中間層、１４ａ 中間層（接着層）、１６，１６ａ，１６ｂ 触媒層、１８ 酸化反応用電極、２０ 基材、２２ 酸化触媒層、２４ セパレータ、２６ 流路、２８ 収容部、３０ 太陽電池セル、４２ カーボン素材分散液、４４ 複合基材／カーボン素材シート、４６ 触媒溶液、４８ 複合基材／カーボン素材／触媒シート、５０ 接着層。 1 Artificial photosynthesis device, 3 Carbon dioxide reduction device, 10, 10a, 10b Reduction reaction electrode, 12, 12a, 12b, 40 composite substrate, 14, 14b, 52 intermediate layer, 14a intermediate layer (adhesive layer), 16, 16a, 16b catalyst layer, 18 oxidation reaction electrode, 20 base material, 22 oxidation catalyst layer, 24 separator, 26 flow path, 28 accommodating part, 30 solar cell, 42 carbon material dispersion, 44 composite base material / carbon material Sheet, 46 catalyst solution, 48 composite substrate / carbon material / catalyst sheet, 50 adhesive layer.
Claims (8)
中間層と、
触媒層と、
を有することを特徴とする還元反応用電極。 A composite base material of carbon fiber and carbon,
With the middle layer
With the catalyst layer
An electrode for a reduction reaction, which comprises.
前記中間層は、ポリマーとカーボン素材とを含む、または、カーボン素材から構成されることを特徴とする還元反応用電極。 The reduction reaction electrode according to claim 1.
An electrode for a reduction reaction, wherein the intermediate layer contains a polymer and a carbon material, or is composed of a carbon material.
前記触媒層は、炭素繊維と炭素との複合基材と、金属錯体とを含むことを特徴とする還元反応用電極。 The electrode for reduction reaction according to claim 1 or 2.
The catalyst layer is an electrode for a reduction reaction, which comprises a composite base material of carbon fibers and carbon and a metal complex.
前記触媒層は、炭素繊維と炭素との複合基材と、カーボンナノチューブと、金属錯体とを含むことを特徴とする還元反応用電極。 The electrode for reduction reaction according to claim 1 or 2.
The catalyst layer is an electrode for a reduction reaction, which comprises a composite base material of carbon fibers and carbon, carbon nanotubes, and a metal complex.
前記金属錯体は、Ｒｕ錯体ポリマーであることを特徴とする還元反応用電極。 The electrode for reduction reaction according to claim 3 or 4.
The metal complex is an electrode for a reduction reaction, which is a Ru complex polymer.
前記複合基材は、金属錯体を含むことを特徴とする還元反応用電極。 The electrode for reduction reaction according to any one of claims 1 to 5.
The composite base material is an electrode for a reduction reaction, which comprises a metal complex.
前記炭素繊維と炭素との複合基材に、クリップで挟み込む接合により集電または給電を行うことを特徴とする還元反応用電極。 The electrode for reduction reaction according to any one of claims 1 to 6.
An electrode for a reduction reaction, which collects or supplies electricity by joining a composite base material of carbon fibers and carbon with a clip.
酸化反応用電極と、
を組み合わせて構成されることを特徴とする反応デバイス。 The electrode for reduction reaction according to any one of claims 1 to 7.
Electrodes for oxidation reaction and
A reaction device characterized by being composed of a combination of.
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