JP6356301B2 - Iridium oxide nanosheet, dispersion containing the iridium oxide nanosheet, and method for producing the dispersion - Google Patents
Iridium oxide nanosheet, dispersion containing the iridium oxide nanosheet, and method for producing the dispersion Download PDFInfo
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- 239000002135 nanosheet Substances 0.000 title claims description 73
- HTXDPTMKBJXEOW-UHFFFAOYSA-N dioxoiridium Chemical compound O=[Ir]=O HTXDPTMKBJXEOW-UHFFFAOYSA-N 0.000 title claims description 72
- 229910000457 iridium oxide Inorganic materials 0.000 title claims description 71
- 239000006185 dispersion Substances 0.000 title claims description 25
- 238000004519 manufacturing process Methods 0.000 title claims description 7
- 239000002253 acid Substances 0.000 claims description 23
- 229910052741 iridium Inorganic materials 0.000 claims description 23
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 claims description 23
- 239000013078 crystal Substances 0.000 claims description 8
- 239000002904 solvent Substances 0.000 claims description 5
- 239000000243 solution Substances 0.000 description 24
- 239000010410 layer Substances 0.000 description 11
- 238000000034 method Methods 0.000 description 10
- 229910052700 potassium Inorganic materials 0.000 description 9
- 239000000758 substrate Substances 0.000 description 9
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 8
- 239000008188 pellet Substances 0.000 description 8
- 239000011591 potassium Substances 0.000 description 8
- 238000005868 electrolysis reaction Methods 0.000 description 7
- 238000002156 mixing Methods 0.000 description 7
- 150000001875 compounds Chemical class 0.000 description 6
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 6
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 6
- VDZOOKBUILJEDG-UHFFFAOYSA-M tetrabutylammonium hydroxide Chemical compound [OH-].CCCC[N+](CCCC)(CCCC)CCCC VDZOOKBUILJEDG-UHFFFAOYSA-M 0.000 description 6
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 5
- 238000003917 TEM image Methods 0.000 description 5
- 150000001339 alkali metal compounds Chemical class 0.000 description 5
- 239000003054 catalyst Substances 0.000 description 5
- 239000000460 chlorine Substances 0.000 description 5
- 229910052801 chlorine Inorganic materials 0.000 description 5
- 238000011156 evaluation Methods 0.000 description 5
- 238000010304 firing Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 238000010298 pulverizing process Methods 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 239000003929 acidic solution Substances 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 150000002736 metal compounds Chemical class 0.000 description 3
- 229910021645 metal ion Inorganic materials 0.000 description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 239000010409 thin film Substances 0.000 description 3
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 150000003973 alkyl amines Chemical class 0.000 description 2
- 125000005210 alkyl ammonium group Chemical group 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000012300 argon atmosphere Substances 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000007598 dipping method Methods 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 238000000635 electron micrograph Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 229910052707 ruthenium Inorganic materials 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 229910021642 ultra pure water Inorganic materials 0.000 description 2
- 239000012498 ultrapure water Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229920000557 Nafion® Polymers 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- GTKRFUAGOKINCA-UHFFFAOYSA-M chlorosilver;silver Chemical compound [Ag].[Ag]Cl GTKRFUAGOKINCA-UHFFFAOYSA-M 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000002484 cyclic voltammetry Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000002524 electron diffraction data Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004299 exfoliation Methods 0.000 description 1
- 229910021397 glassy carbon Inorganic materials 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 150000002503 iridium Chemical class 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 238000001451 molecular beam epitaxy Methods 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000005453 pelletization Methods 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229910000027 potassium carbonate Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000010189 synthetic method Methods 0.000 description 1
- DZLFLBLQUQXARW-UHFFFAOYSA-N tetrabutylammonium Chemical compound CCCC[N+](CCCC)(CCCC)CCCC DZLFLBLQUQXARW-UHFFFAOYSA-N 0.000 description 1
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- Inorganic Compounds Of Heavy Metals (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Description
本発明は、酸化イリジウムナノシート、その酸化イリジウムナノシートを含む分散溶液及びその分散溶液の製造方法に関する。 The present invention relates to an iridium oxide nanosheet, a dispersion solution containing the iridium oxide nanosheet, and a method for producing the dispersion solution .
ナノシートは、厚さがナノメートルオーダーであるのに対して、横サイズがその数十倍から数百倍以上という高い形状異方性を持つ２次元状の物質である。そうしたナノシートは、母相の機能性（導電性、半導体的性質、誘電性等）を受け継ぐだけでなく、触媒反応等に必要な広い比表面積を有している。また、ナノシートは、一次元の量子サイズ効果を発現する等、際立った物性を示すことがある。さらに、ナノシートは、一度分離させたナノシートを機能性ブロックとして再び３次元的に集積化し、熱力学的には達成できない人工超格子状のナノ構造材料を形成することにより、物性・特性を自在に制御できる可能性を秘めている。そにため、ナノシートについては、これまで分子線ビームエピタキシー等の気相合成技術が主流であった超格子アプローチを液相で展開できるため、製品性能だけでなく合成ルートの視点からも、エネルギー・デバイス分野を中心とした産業界から高い関心を集めている。 A nanosheet is a two-dimensional substance having a high shape anisotropy of a lateral size of several tens to several hundreds of times, while its thickness is on the order of nanometers. Such nanosheets not only inherit the functionality of the matrix (conductivity, semiconducting properties, dielectric properties, etc.) but also have a large specific surface area required for catalytic reactions and the like. In addition, the nanosheet may exhibit outstanding physical properties such as a one-dimensional quantum size effect. Furthermore, nanosheets can be reconfigured in three dimensions as functional blocks, once separated nanosheets, to form artificial superlattice-like nanostructured materials that cannot be achieved thermodynamically. It has the potential to be controlled. Therefore, for nanosheets, the superlattice approach, which has so far been the mainstream of gas-phase synthesis techniques such as molecular beam epitaxy, can be developed in the liquid phase. It has attracted a lot of interest from the industry, especially in the device field.
ナノシートの合成方法に関しては、分子、イオン等から成長させる方法、層状化合物を単層剥離する方法等が提案されている。これらの合成方法は、金属化合物のナノシートの合成に向けて検討されてきたものであるが、液相反応を利用して白金や金等といった貴金属のナノシートを製造する技術も提案されている（特許文献１，２参照）。 As a nanosheet synthesis method, a method of growing from a molecule, an ion, or the like, a method of peeling a layered compound from a single layer, and the like have been proposed. These synthetic methods have been studied for the synthesis of nanosheets of metal compounds, but techniques for producing nanosheets of noble metals such as platinum and gold using liquid phase reactions have also been proposed (patents). References 1 and 2).
本発明者は、金属ナノシートを得るための新しい方法として、金属化合物の層状化合物を前駆体として利用する技術を提案した（特許文献３参照）。この技術は、酸化ルテニウムが層状に重なる層状化合物を準備し、その酸化ルテニウムを還元して層状化合物を前駆体とする金属ルテニウムナノシートを得る方法であり、酸化ルテニウムナノシートの薄膜の状態で酸化ルテニウムを還元して金属ルテニウムナノシートを得ている。 The present inventor has proposed a technique of using a layered compound of a metal compound as a precursor as a new method for obtaining a metal nanosheet (see Patent Document 3). This technology is a method of preparing a layered compound in which ruthenium oxide is layered, and reducing the ruthenium oxide to obtain a metal ruthenium nanosheet using the layered compound as a precursor, and ruthenium oxide in the state of a thin film of ruthenium oxide nanosheet. Reduction to obtain a metal ruthenium nanosheet.
上記のように、結晶性の金属化合物ナノシートは、単位格子に由来する厚さを有し、二次元的（平面状）に広がった構造を持っている。多くのナノシートは、層状構造を持つ化合物の剥離により得ることができ、同じ原子数で構成される粒子よりも利用できる表面が大きくなるという利点がある。良導電性を有するナノシートの素材としては、カーボン（グラフェン）、酸化ルテニウム（酸化ルテニウムナノシート）等が挙げられる。 As described above, the crystalline metal compound nanosheet has a thickness derived from the unit cell, and has a two-dimensional (planar) spread structure. Many nanosheets can be obtained by exfoliation of a compound having a layered structure, and have the advantage that the available surface is larger than particles composed of the same number of atoms. Examples of the material of the nanosheet having good conductivity include carbon (graphene) and ruthenium oxide (ruthenium oxide nanosheet).
本発明の目的は、寸法安定性電極の電極触媒として電解用、塩素発生用、金属イオン分離等に用いられている酸化イリジウムナノシート、その酸化イリジウムナノシートを含む分散溶液及びその分散溶液の製造方法を提供することにある。 An object of the present invention is to provide an iridium oxide nanosheet used for electrolysis, chlorine generation, metal ion separation, etc. as an electrode catalyst of a dimensionally stable electrode, a dispersion solution containing the iridium oxide nanosheet, and a method for producing the dispersion solution It is to provide.
本発明に係る酸化イリジウムナノシートは、３ｎｍ以下の厚さの酸化イリジウム単結晶シートであることを特徴とする。The iridium oxide nanosheet according to the present invention is an iridium oxide single crystal sheet having a thickness of 3 nm or less.
本発明に係る酸化イリジウムナノシート分散溶液は、３ｎｍ以下の厚さの酸化イリジウム単結晶シートである酸化イリジウムナノシートが溶媒中に分散してなることを特徴とする。The iridium oxide nanosheet dispersion solution according to the present invention is characterized in that iridium oxide nanosheets, which are iridium oxide single crystal sheets having a thickness of 3 nm or less, are dispersed in a solvent.
本発明に係る酸化イリジウムナノシート分散溶液の製造方法は、酸化イリジウムを層状イリジウム酸塩とし、得られた層状イリジウム酸塩を層状イリジウム酸とし、次いで層状イリジウム酸を３ｎｍ以下の厚さの酸化イリジウム単結晶シートである酸化イリジウムナノシートが溶媒中に分散してなる酸化イリジウムナノシート分散溶液とすることを特徴とする。The method for producing an iridium oxide nanosheet dispersion solution according to the present invention comprises converting iridium oxide into a layered iridate, the resulting layered iridate into a layered iridium acid, and then forming the layered iridium acid into a layer having a thickness of 3 nm or less. An iridium oxide nanosheet dispersion solution in which iridium oxide nanosheets as crystal sheets are dispersed in a solvent is used.
本発明によれば酸化イリジウムナノシート、その酸化イリジウムナノシートを含む分散溶液及びその分散溶液の製造方法を提供することができた。酸化イリジウムは、寸法安定性電極の電極触媒として電解用、塩素発生用、金属イオン分離等に用いられていることから、その応用が期待でき、特に酸素還元、塩素発生、電解等の触媒として期待できる。 According to the present invention, it was possible to provide an iridium oxide nanosheet, a dispersion solution containing the iridium oxide nanosheet, and a method for producing the dispersion solution . Since iridium oxide is used as an electrode catalyst for dimensionally stable electrodes for electrolysis, chlorine generation, metal ion separation, etc., its application can be expected, especially as a catalyst for oxygen reduction, chlorine generation, electrolysis, etc. it can.
以下、本発明に係る酸化イリジウムナノシート、その酸化イリジウムナノシートを含む分散溶液及びその分散溶液の製造方法について詳しく説明するが、本発明は、その技術的範囲に含まれる範囲において下記の説明に限定されない。 Hereinafter, the iridium oxide nanosheet according to the present invention, a dispersion solution containing the iridium oxide nanosheet and a method for producing the dispersion solution will be described in detail, but the present invention is not limited to the following description within the scope of the technical scope thereof. .
［層状イリジウム酸塩、層状イリジウム酸］
層状イリジウム酸塩は、ＭｘＩｒＯｙ・ｎＨ２Ｏ（Ｍは１価の金属、ｘは０．１〜０．５、ｙは１．５〜２．５、ｎは０．５〜１．５）が層状に重なり合っている。Ｍは、アルカリ金属であることが好ましく、例えば、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、Ｃｓ等を挙げることができる。また、ｘ、ｙは、酸化イリジウムとアルカリ金属化合物の配合量で調製することができる。
[Layered iridate, layered iridium acid]
Layer-like iridium salt, M x IrO y · nH 2 O (M is a monovalent metal, x is 0.1 to 0.5, y is 1.5 to 2.5, n is 0.5 to 1 .5) are layered. M is preferably an alkali metal, and examples thereof include Li, Na, K, Rb, and Cs. Moreover, x and y can be prepared with the compounding quantity of an iridium oxide and an alkali metal compound.
層状イリジウム酸塩は、先ず、（１）酸化イリジウムを粉砕した後にアルカリ金属化合物と混合する、（２）得られた混合物をペレット成形する、（３）成形したペレットに対して第１回目の焼成を行う、（４）焼成後のペレットを粉砕し混合する、（５）粉砕したものを再度ペレット成形する、（６）成形したペレットに対して第２回目の焼成を行う、（７）焼成後のものを中性になるまで洗浄する。こうして層状イリジウム酸塩を得ることができる。 The layered iridate is firstly (1) pulverized iridium oxide and then mixed with an alkali metal compound, (2) pelletizing the resulting mixture, and (3) first firing on the molded pellets (4) pulverize and mix the pellets after firing, (5) re-mold the pellets after pulverization, (6) perform the second firing on the formed pellets, (7) after firing Wash things until neutral. Thus, a layered iridate can be obtained.
このとき、（１）の粉砕混合工程と（４）の粉砕混合工程は、窒素雰囲気下で行うことが望ましい。（１）の粉砕混合工程で用いるアルカリ金属化合物は特に限定されないが、炭酸カリウム等を挙げることができる。酸化イリジウムとアルカリ金属化合物との混合比は特に限定されないが、例えば酸化イリジウム：アルカリ金属化合物＝１：１〜１：４程度にすることができる。（３）の第１焼成工程は、不活性ガス雰囲気中で、例えば７００℃〜８００℃（例えば７５０℃）の範囲で１〜数時間（例えば１時間）の熱処理とすることができ、（６）の第２焼成工程も、不活性ガス雰囲気中で、例えば７００℃〜８００℃（例えば７８０℃）の範囲で１〜数時間（例えば１時間）の熱処理とすることができる。 At this time, it is desirable that the pulverizing and mixing step (1) and the pulverizing and mixing step (4) are performed in a nitrogen atmosphere. The alkali metal compound used in the pulverizing and mixing step (1) is not particularly limited, and examples thereof include potassium carbonate. The mixing ratio of iridium oxide and alkali metal compound is not particularly limited, but can be, for example, about iridium oxide: alkali metal compound = 1: 1 to 1: 4. The first firing step (3) can be a heat treatment in an inert gas atmosphere, for example, in the range of 700 ° C. to 800 ° C. (eg, 750 ° C.) for 1 to several hours (eg, 1 hour), (6 The second baking step can also be a heat treatment in an inert gas atmosphere, for example, in the range of 700 ° C. to 800 ° C. (eg, 780 ° C.) for 1 to several hours (eg, 1 hour).
層状イリジウム酸は、得られた層状イリジウム酸塩を酸性溶液中で処理して得ることができる。酸性溶液中の処理とは、例えば１ＭＨＣｌ等の酸性溶液に、１日〜４日程度（例えば３日）浸漬させる処理である。得られた層状イリジウム酸は、ＨｘＩｒＯｙ・ｎＨ２Ｏ（ｘは０．１〜０．５、ｙは１．５〜２．５、ｎは０〜１）が層状に重なり合っている。 Layered iridium acid can be obtained by treating the obtained layered iridate in an acidic solution. The treatment in an acidic solution is a treatment of immersing in an acidic solution such as 1M HCl for about 1 to 4 days (for example, 3 days). Obtained layered iridium acid, H x IrO y · nH 2 O (x is 0.1 to 0.5, y is 1.5 to 2.5, n is 0-1) are overlapped in layers.
［酸化イリジウムナノシート］
本発明に係る酸化イリジウムナノシートは、３ｎｍ以下の厚さの酸化イリジウム単結晶シートである。この酸化イリジウムナノシートは、先ず、上記で得られた層状イリジウム酸に、アルキルアンモニウム又はアルキルアミンを反応させて、アルキルアンモニウム−層状イリジウム酸層間化合物とし、その後、そのアルキルアンモニウム−層状イリジウム酸層間化合物を水等の溶媒と混合して、酸化イリジウムナノシート分散溶液（濃紺色の分散溶液）を得る。得られた酸化イリジウムナノシート分散溶液を用いて、相互吸着法で酸化イリジウムナノシートを得ることができる。なお、アルキルアンモニウム又はアルキルアミンとしては、各種のものを用いることができるが、例えばテトラブチルアンモニウム等を好ましく用いることができる。
[Iridium oxide nanosheet]
The iridium oxide nanosheet according to the present invention is an iridium oxide single crystal sheet having a thickness of 3 nm or less. In this iridium oxide nanosheet, first, the layered iridium acid obtained above is reacted with alkylammonium or alkylamine to form an alkylammonium-layered iridium acid intercalation compound. By mixing with a solvent such as water, an iridium oxide nanosheet dispersion solution (dark blue dispersion solution) is obtained. Using the obtained iridium oxide nanosheet dispersion solution, iridium oxide nanosheets can be obtained by a mutual adsorption method. In addition, although various things can be used as alkylammonium or alkylamine, for example, tetrabutylammonium etc. can be used preferably.
具体的には、酸化イリジウムナノシートを被覆するための基板（例えばＳｉ基板又は石英基板）を洗浄した後、その基板を酸化イリジウムナノシート分散溶液中に浸漬する。一回の浸漬工程で１層の酸化イリジウムナノシートが基板上に被覆できる。洗浄と浸漬を繰り返すことにより、繰り返しの数だけ酸化イリジウムナノシートを積層することができ、５層、１０層、２０層、…と積層することができる。 Specifically, after washing a substrate (for example, a Si substrate or a quartz substrate) for coating the iridium oxide nanosheet, the substrate is immersed in the iridium oxide nanosheet dispersion solution. One layer of iridium oxide nanosheet can be coated on the substrate in a single dipping process. By repeating the washing and dipping, the iridium oxide nanosheets can be stacked by the number of repetitions, and can be stacked as five layers, ten layers, twenty layers,.
本発明では、イリジウムに着目し、酸化イリジウムナノシートを得ることを目的とし、その酸化イリジウムナノシートを作製するために用いる層状イリジウム酸塩を新たに合成し、その層状イリジウム酸塩から層状イリジウム酸を新たに合成し、その層状イリジウム酸から酸化イリジウムナノシートを得た。酸化イリジウムは、寸法安定性電極の電極触媒として電解用、塩素発生用、金属イオン分離等に用いられており、その応用が期待でき、特に酸素還元、塩素発生、電解等の触媒として期待できる。また、酸化イリジウムは、広い電位範囲で電気化学的に安定で、耐酸・耐塩基性が高いため、優れた耐食性を有し、さらに電子伝導性を有する導電性金属酸化物である。 In the present invention, focusing on iridium, the purpose is to obtain an iridium oxide nanosheet, and a layered iridate used for producing the iridium oxide nanosheet is newly synthesized, and the layered iridium acid is newly obtained from the layered iridate. The iridium oxide nanosheet was obtained from the layered iridium acid. Iridium oxide is used as an electrode catalyst for dimensionally stable electrodes for electrolysis, chlorine generation, metal ion separation and the like, and its application can be expected, and in particular, it can be expected as a catalyst for oxygen reduction, chlorine generation, electrolysis and the like. In addition, iridium oxide is a conductive metal oxide that is electrochemically stable in a wide potential range, has high acid / base resistance, and therefore has excellent corrosion resistance and electronic conductivity.
実施例により、本発明をさらに詳しく説明する。 The examples further illustrate the present invention.
［実施例１］
層状のイリジウム酸カリウム及び層状イリジウム酸を作製した。先ず、窒素置換したグローブボックス内で、酸化イリジウム（ＩｒＯ２）を粉砕した後に炭酸カリウム（Ｋ２ＣＯ３）と混ぜ、３０分間混合した。混合比（ＩｒＯ２：Ｋ２ＣＯ３）は１：２とした。グローブボックスから出した混合物を、１．５ｔｏｎで１０分間のプレスを行ってペレットを成形した。次いで、成形したペレットをアルゴン雰囲気中にて７５０℃、１時間の焼成（第１回目の焼成）を行った。再びグローブボックス内に入れ、粉砕混合を行った後、１．５ｔｏｎで１０分間のプレスを行ってペレットを再び成形した。次いで、成形したペレットをアルゴン雰囲気中にて７８０℃、１時間の焼成（第２回目の焼成）を行った。焼成後のものは、光沢を持つ黒色を呈した。次いで、超音波を印加しながら中性になるまで水洗浄した。こうして、濃紺色がなくなった層状イリジウム酸カリウムを得た。その層状イリジウム酸カリウムを、１ＭＨＣｌ溶液に入れ、３日間放置して層状イリジウム酸を得た。上澄み液は褐色であった。
[Example 1]
Layered potassium iridate and layered iridium acid were prepared. First, iridium oxide (IrO 2 ) was pulverized in a nitrogen-substituted glove box, mixed with potassium carbonate (K 2 CO 3 ), and mixed for 30 minutes. The mixing ratio (IrO 2 : K 2 CO 3 ) was 1: 2. The mixture taken out from the glove box was pressed at 1.5 ton for 10 minutes to form pellets. Next, the molded pellets were baked at 750 ° C. for 1 hour (first baking) in an argon atmosphere. After putting in the glove box again, pulverization and mixing were performed, pressing was performed at 1.5 ton for 10 minutes, and pellets were formed again. Next, the molded pellets were baked at 780 ° C. for 1 hour (second baking) in an argon atmosphere. The thing after baking exhibited the glossy black. Subsequently, it washed with water until it became neutral while applying ultrasonic waves. In this way, layered potassium iridate having no dark blue color was obtained. The layered potassium iridate was placed in a 1M HCl solution and allowed to stand for 3 days to obtain layered iridium acid. The supernatant liquid was brown.
図１は、得られた層状イリジウム酸の電子顕微鏡写真である。併せて、層状イリジウム酸カリウムについても観察した。写真より、層状イリジウム酸と層状イリジウム酸カリウムのいずれにも、明確な層状構造が確認できた。図２は、層状イリジウム酸のＸ線回折パターン（Ｘ線源：ＣｕＫα線）である。層イリジウム酸カリウムの場合は、２θで１３．０°と２６．０°に結晶性のピークが表れ、層状イリジウム酸の場合は、２θで１２．３°と２４．６°に結晶性のピークが表れた。なお、いずれも場合も、原料である酸化イリジウムのピークは見られなかった。 FIG. 1 is an electron micrograph of the obtained layered iridium acid. In addition, the layered potassium iridate was also observed. From the photograph, a clear layered structure was confirmed in both layered iridium acid and layered potassium iridate. FIG. 2 is an X-ray diffraction pattern (X-ray source: CuKα ray) of layered iridium acid. In the case of layered potassium iridate, crystalline peaks appear at 13.0 ° and 26.0 ° at 2θ, and in the case of layered iridium acid, crystalline peaks at 12.3 ° and 24.6 ° at 2θ. Appeared. In either case, the peak of iridium oxide as a raw material was not observed.
層状イリジウム酸と層状イリジウム酸カリウムの組成を、ＥＤＸ（ＥＸ−２００、株式会社堀場製作所）を用いて１５点を測定した。層状イリジウム酸カリウムは、原子比で、Ｋが７．５、Ｉｒが２３．１、Ｏが６９．４であった。また、層状イリジウム酸は、原子比で、Ｉｒが２７．６、Ｏが７２．４であった。 The composition of layered iridium acid and layered potassium iridate was measured at 15 points using EDX (EX-200, Horiba, Ltd.). The layered potassium iridate had an atomic ratio of K of 7.5, Ir of 23.1, and O of 69.4. The layered iridium acid had an atomic ratio of Ir of 27.6 and O of 72.4.
［実施例２］
層状イリジウム酸から酸化イリジウムナノシートを作製した。実施例１で得た層状イリジウム酸を用い、１０％テトラブチルアンモニウムヒドロキシド（ＴＢＡＯＨ）溶液を、Ｉｒ：ＴＢＡＯＨ＝１：５で加えた。このとき、得られる酸化イリジウムナノシートの濃度が０．５ｇ／Ｌになるように調製した。その後、２５℃、１６０ｒｐｍ、７日間振とうした。こうして、０．５ｇ／Ｌ酸化イリジウムナノシート分散溶液を得た。この酸化イリジウムナノシート分散溶液は濃紺色であった。
[Example 2]
Iridium oxide nanosheets were prepared from layered iridium acid. Using the layered iridium acid obtained in Example 1, a 10% tetrabutylammonium hydroxide (TBAOH) solution was added at Ir: TBAOH = 1: 5. At this time, it prepared so that the density | concentration of the obtained iridium oxide nanosheet might be 0.5 g / L. Thereafter, the mixture was shaken at 25 ° C. and 160 rpm for 7 days. Thus, a 0.5 g / L iridium oxide nanosheet dispersion solution was obtained. This iridium oxide nanosheet dispersion solution was dark blue.
［実施例３］
実施例２で得た酸化イリジウムナノシート分散溶液を用いて酸化イリジウムナノシートを得た。ナノシートは、交互吸着積層法（Layer by Layer; LbL）により成膜した。先ず、酸化イリジウムナノシートを被覆するためのＳｉ基板を準備し、１０質量％ＰＶＡ水溶液に１０分間浸漬して洗浄し、超純水で洗浄した後、Ｓｉ基板を０．３ｇ／Ｌ酸化イリジウムナノシート分散溶液中に２０分間浸漬した。Ｓｉ基板を引き上げて超純水で洗浄し、再び１０質量％ＰＶＡ水溶液に戻して洗浄、浸漬を繰り返した。こうして、酸化イリジウムナノシートを被覆したＳｉ基板を得た。
[Example 3]
Using the iridium oxide nanosheet dispersion solution obtained in Example 2, iridium oxide nanosheets were obtained. The nanosheet was formed by an alternating adsorption lamination method (Layer by Layer; LbL). First, a Si substrate for coating iridium oxide nanosheets was prepared, immersed in a 10% by mass PVA aqueous solution for 10 minutes, washed with ultrapure water, and then the Si substrate was dispersed in 0.3 g / L iridium oxide nanosheets. It was immersed in the solution for 20 minutes. The Si substrate was pulled up, washed with ultrapure water, returned to the 10% by mass PVA aqueous solution, and washed and immersed repeatedly. Thus, a Si substrate coated with the iridium oxide nanosheet was obtained.
図３は、ＳＰＭ（ＳＰＡ４００、セイコーインスツルメンツ株式会社製）を用いて撮影した酸化イリジウムナノシート薄膜のＤＦＭ画像である。１回浸漬して１層被覆したもの、３回浸漬して３層被覆したもの、５回浸漬して５層被覆したものについて撮影した。図４は、酸化イリジウムナノシートのＤＦＭ画像の拡大図であり、併せて膜圧測定も行ったところ、平均厚さが１．６５ｎｍ±０．１ｎｍという結果が得られた。 FIG. 3 is a DFM image of an iridium oxide nanosheet thin film photographed using SPM (SPA 400, manufactured by Seiko Instruments Inc.). Images were taken of one soaked one layer, three soaked three layers, and five soaked five layers. FIG. 4 is an enlarged view of the DFM image of the iridium oxide nanosheet. When the film pressure was also measured, the result that the average thickness was 1.65 nm ± 0.1 nm was obtained.
図５は、酸化イリジウムナノシートの形態を示すＴＥＭ像（Ａ）、拡大ＴＥＭ像（Ｂ）及び電子線回折パターン（Ｃ）である。このＴＥＭ像は、観察用グリッド上に酸化イリジウムナノシート分散溶液を滴下し、６０℃で６時間乾燥した後のものを撮影した。なお、観察用グリッドは、日本電子株式会社、Ｎｏ．１６０５、支持膜付きグリッド（カーボン補強済みフィルム）である。図５に示すように、酸化イリジウムナノシートは、典型的な単結晶の電子線回折パターンを示した。 FIG. 5 shows a TEM image (A), an enlarged TEM image (B), and an electron beam diffraction pattern (C) showing the form of the iridium oxide nanosheet. This TEM image was taken after the iridium oxide nanosheet dispersion solution was dropped on the observation grid and dried at 60 ° C. for 6 hours. The observation grid is JEOL Ltd., No. 1605, a grid with a supporting film (carbon reinforced film). As shown in FIG. 5, the iridium oxide nanosheet exhibited a typical single crystal electron diffraction pattern.
［実施例４］
予め０．０５μｍのアルミナ粉末を用いてバフ研磨した直径５ｍｍのグラッシーカーボン（東海カーボン株式会社）上に、実施例２で得た０．３ｇ／Ｌ酸化イリジウムナノシート分散溶液２０μＬを滴下し、６０℃３０分乾燥させた。その上に、５質量％のナフィオン（Nafion、デュポン社の登録商標）溶液２０μＬを滴下し、６０℃３０分乾燥させた。こうして評価用電極を作製した。
[Example 4]
20 μL of the 0.3 g / L iridium oxide nanosheet dispersion solution obtained in Example 2 was dropped on glassy carbon (Tokai Carbon Co., Ltd.) having a diameter of 5 mm buffed with an alumina powder of 0.05 μm in advance, and 60 ° C. Dry for 30 minutes. On top of that, 20 μL of a 5% by mass Nafion (registered trademark of DuPont) solution was dropped and dried at 60 ° C. for 30 minutes. Thus, an evaluation electrode was produced.
回転ディスク電極（ＲＤＥ）測定は、標準的な３電極電気化学セルで行った。カウンター電極としてＰｔメッシュ（株式会社ニコラ）を用い、参照電極として銀塩化銀電極を用い、作用極として上記得られた評価用電極を用いた。ＲＤＥ測定は、０．５ＭのＨ２ＳＯ４電解液中で行った。 The rotating disk electrode (RDE) measurement was performed on a standard three-electrode electrochemical cell. Pt mesh (Nikola Corporation) was used as the counter electrode, a silver-silver chloride electrode was used as the reference electrode, and the evaluation electrode obtained above was used as the working electrode. RDE measurements were performed in 0.5M H 2 SO 4 electrolyte.
比静電容量評価は、電位範囲：０．２〜１．２Ｖ（ｖｓ．ＲＨＥ）でのサイクリックボルタンメトリーで評価し、２〜５００ｍＶ／ｓの範囲で電位走査速度依存性から評価した。アノーディックスキャンとカソーディックスキャンで、０．８５Ｖと０．９５Ｖ（ｖｓ．ＲＨＥ）付近に特徴的なピークが見られた。 The specific capacitance was evaluated by cyclic voltammetry in the potential range: 0.2 to 1.2 V (vs. RHE), and evaluated from the potential scanning speed dependency in the range of 2 to 500 mV / s. In anodic scan and cathodic scan, characteristic peaks were observed in the vicinity of 0.85 V and 0.95 V (vs. RHE).
安定性評価は、５０ｍＶ／ｓで、０．０５Ｖから、１．２Ｖ、１．３Ｖ、１．４Ｖ、１．５Ｖ（ｖｓ．ＲＨＥ）の範囲で電位範囲を上げていった。０．０５Ｖ〜１．５Ｖ（ｖｓ．ＲＨＥ）の電位範囲で、電気分解を伴うガス発生がなく、電極（酸化イリジウムナノシート）の溶解もなかった。 In the stability evaluation, the potential range was increased from 0.05 V to 1.2 V, 1.3 V, 1.4 V, and 1.5 V (vs. RHE) at 50 mV / s. In a potential range of 0.05 V to 1.5 V (vs. RHE), there was no gas generation accompanied by electrolysis, and there was no dissolution of the electrode (iridium oxide nanosheet).
［実施例５］
電解液を１ＭＬｉ２ＳＯ４に変えた他は、実施例４と同様にして比静電容量評価と安定性評価を行った。０．０５Ｖ〜１．５Ｖ（ｖｓ．ＲＨＥ）の電位範囲で、電気分解を伴うガス発生がなく、電極（酸化イリジウムナノシート）の溶解もなかった。
[Example 5]
The specific capacitance evaluation and the stability evaluation were performed in the same manner as in Example 4 except that the electrolytic solution was changed to 1 M Li 2 SO 4 . In a potential range of 0.05 V to 1.5 V (vs. RHE), there was no gas generation accompanied by electrolysis, and there was no dissolution of the electrode (iridium oxide nanosheet).
Claims (3)
得られた層状イリジウム酸塩を層状イリジウム酸とし、The layered iridate obtained is a layered iridium acid,
次いで層状イリジウム酸を３ｎｍ以下の厚さの酸化イリジウム単結晶シートである酸化イリジウムナノシートが溶媒中に分散してなる酸化イリジウムナノシート分散溶液とすることを特徴とする酸化イリジウムナノシート分散溶液の製造方法。Next, a method for producing an iridium oxide nanosheet dispersion solution characterized in that layered iridium acid is used as an iridium oxide nanosheet dispersion solution in which iridium oxide nanosheets, which are iridium oxide single crystal sheets having a thickness of 3 nm or less, are dispersed in a solvent.
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