JP2008064674A - MANUFACTURING METHOD FOR SnO2 GAS SENSOR - Google Patents
MANUFACTURING METHOD FOR SnO2 GAS SENSOR Download PDFInfo
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この発明はＳｎＯ２ガスセンサの製造方法に関し、特にＳｎＯ２への触媒添加に関する。 The present invention relates to a method for manufacturing a SnO 2 gas sensor, and more particularly to addition of a catalyst to SnO 2 .
ＳｎＯ２ガスセンサの製造では、ＳｎＯ２の粉体に硝酸Ｐｄ，硝酸銅等の触媒金属塩の溶液を添加し、乾燥後に焼成してＰｄ，Ｐｔ，Ｒｈ，Ｒｕ，Ｒｅ，Ｉｒ等の貴金属触媒や酸化銅、酸化亜鉛、酸化タングステン等の遷移金属触媒を担持させる。次いで触媒添加後のＳｎＯ２粉体を成形し、焼成してガスセンサとする。しかしながらこの手法では、微細な触媒粒子をＳｎＯ２中に均一に分散させることが困難である。
なお特許文献１は逆ミセル法により酸化ジルコニウムを調製することを開示しているが、逆ミセル法によりＳｎＯ２に触媒を添加することを開示していない。
Patent Document 1 discloses preparing zirconium oxide by the reverse micelle method, but does not disclose adding a catalyst to SnO 2 by the reverse micelle method.
この発明の課題は、均一な構造のＳｎＯ２粒子中に、微細で均一な粒度の触媒を均一に分散させたＳｎＯ２ガスセンサの製造方法を提供することにある。 The object of the invention, the SnO 2 particles having a uniform structure is to provide a SnO 2 gas sensor production method which is uniformly dispersed a fine and uniform particle size of the catalyst.
この発明のＳｎＯ２ガスセンサの製造方法では、Ｓｎ(ＯＨ)６ ２−イオンをアルカリ性の逆ミセル中に含有する逆ミセル溶液と、触媒金属イオンを酸性の逆ミセル中に含有する逆ミセル溶液とを混合することにより、逆ミセル中でＳｎ(ＯＨ)４上に触媒金属の水酸化物を析出させた混合逆ミセル溶液とし、次いで触媒金属の水酸化物を析出させたＳｎ(ＯＨ)４を混合逆ミセル溶液から分離、乾燥して、触媒を担持させたＳｎＯ２もしくは水酸化スズの粉体とし、該粉体を電極と接続した形状に成形・焼成してガスセンサとする。 In the manufacturing method of the SnO 2 gas sensor of the present invention, a reverse micelle solution containing Sn (OH) 6 2- ion in an alkaline reverse micelle and a reverse micelle solution containing catalytic metal ions in an acidic reverse micelle by mixing, the mixed reverse micelle solution in the reverse micelles to precipitate a hydroxide of the catalytic metal on the Sn (OH) 4, followed by mixing the Sn (OH) 4 which was precipitated hydroxide of the catalytic metal The powder is separated from the reverse micelle solution and dried to obtain a powder of SnO 2 or tin hydroxide carrying a catalyst, and the powder is molded and fired into a shape connected to an electrode to obtain a gas sensor.
この発明のＳｎＯ２ガスセンサの製造方法では、Ｓｎ(ＯＨ)６ ２−イオンをアルカリ性の逆ミセル中に含有する逆ミセル溶液と、酸性逆ミセルの逆ミセル溶液とを混合して、Ｓｎ(ＯＨ)４を逆ミセル中に析出させた混合逆ミセル溶液とし、該混合逆ミセル溶液と、触媒金属イオンを酸性の逆ミセル中に含有する逆ミセル溶液とを混合することにより、逆ミセル中でＳｎ(ＯＨ)４上に触媒金属の水酸化物を析出させた第２の混合逆ミセル溶液とし、次いで触媒金属の水酸化物を析出させたＳｎ(ＯＨ)４を第２の混合逆ミセル溶液から分離、乾燥して、触媒を担持させたＳｎＯ２もしくは水酸化スズの粉体とし、該粉体を電極と接続した形状に成形・焼成してガスセンサとする。 In the manufacturing method of the SnO2 gas sensor according to the present invention, a reverse micelle solution containing Sn (OH) 6 2- ion in an alkaline reverse micelle and a reverse micelle solution of an acidic reverse micelle are mixed, and Sn (OH) 4 The mixed reverse micelle solution precipitated in the reverse micelle, and the mixed reverse micelle solution and the reverse micelle solution containing the catalytic metal ion in the acidic reverse micelle are mixed to form Sn (OH ) 4 is used as a second mixed reverse micelle solution in which a catalyst metal hydroxide is deposited, and then Sn (OH) 4 in which a catalyst metal hydroxide is deposited is separated from the second mixed reverse micelle solution. It is dried to form a powder of SnO 2 or tin hydroxide carrying a catalyst, and the powder is molded and fired into a shape connected to an electrode to obtain a gas sensor.
好ましくは、Ｓｎ(ＯＨ)６ ２−イオンをアルカリ性の逆ミセル中に含有する逆ミセル溶液を、４価のＳｎの有機酸塩を水酸化テトラアルキルアンモニウムもしくはトリアルキルアンモニウムで水に溶解して、Ｓｎ(ＯＨ)６ ２−イオンを含む水溶液とし、該水溶液を界面活性剤と疎水性の有機溶媒との混合物中に分散させることにより調製する。
触媒中の金属成分（触媒金属）の種類は貴金属に限らず、遷移金属やランタニド、３価あるいは４価の典型金属とし、Ｓｎは含めない。
Preferably, a reverse micelle solution containing Sn (OH) 6 2- ion in an alkaline reverse micelle is prepared by dissolving a tetravalent Sn organic acid salt in water with tetraalkylammonium hydroxide or trialkylammonium hydroxide, An aqueous solution containing Sn (OH) 6 2- ion is prepared, and the aqueous solution is dispersed in a mixture of a surfactant and a hydrophobic organic solvent.
The kind of the metal component (catalyst metal) in the catalyst is not limited to a noble metal, but a transition metal, a lanthanide, a trivalent or tetravalent typical metal, and Sn is not included.
この発明では、微細な逆ミセル中でＳｎ(ＯＨ)４に触媒金属の水酸化物を担持させる。このためＳｎＯ２粉体に担持させる場合と異なり、均一な粒度の触媒を高度に分散させて担持できる。またＳｎ(ＯＨ)４を逆ミセル中で調製するので、その粒度や高次構造を均一にできる。このため高活性な触媒を担持し、所望の粒度と高次構造を持つＳｎＯ２ガスセンサを製造できる。 In the present invention, a hydroxide of a catalytic metal is supported on Sn (OH) 4 in fine reverse micelles. For this reason, unlike the case where it is supported on SnO 2 powder, a catalyst having a uniform particle size can be highly dispersed and supported. Further, since Sn (OH) 4 is prepared in reverse micelles, its particle size and higher order structure can be made uniform. Therefore, it is possible to manufacture a SnO 2 gas sensor that supports a highly active catalyst and has a desired particle size and higher order structure.
Ｓｎ(ＯＨ)６ ２−イオンは水中ではアルカリ性で安定で、弱アルカリ性〜酸性でＳｎ(ＯＨ)４として析出するので、アルカリ性の逆ミセル中にＳｎ(ＯＨ)６ ２−イオンを含有させ、酸性の逆ミセルと反応させてＰＨを中性に近づけると、Ｓｎ(ＯＨ)４が析出する。また触媒金属イオンは水中では強酸性で安定で、弱酸性〜アルカリ性で水酸化物として析出する。そこでＳｎ(ＯＨ)４を析出させた後に触媒金属の水酸化物を析出させても良く、あるいはＳｎ(ＯＨ)４の逆ミセル溶液と触媒金属イオンを含有する逆ミセル溶液とを混合して、Ｓｎ(ＯＨ)４と触媒金属の水酸化物とを同時に析出を担持させても良い。実験によると、Ｓｎ(ＯＨ)４を析出させた後に触媒金属の水酸化物を析出させた方が、微細な触媒をＳｎＯ２に高分散させることができる。 Sn (OH) 6 2- ion is alkaline and stable in water, and weakly alkaline to acidic and precipitates as Sn (OH) 4. Therefore, Sn (OH) 6 2- ion is contained in an alkaline reverse micelle, and is acidic. Sn (OH) 4 precipitates when the pH is brought close to neutrality by reacting with the reverse micelle. Further, catalytic metal ions are strongly acidic and stable in water, and weakly acidic to alkaline and precipitate as hydroxides. Therefore, after depositing Sn (OH) 4 , the catalyst metal hydroxide may be deposited, or the reverse micelle solution of Sn (OH) 4 and the reverse micelle solution containing the catalyst metal ions are mixed, Sn (OH) 4 and catalyst metal hydroxide may be supported simultaneously. According to experiments, fine catalyst can be highly dispersed in SnO 2 by depositing the hydroxide of the catalyst metal after depositing Sn (OH) 4 .
Ｓｎ(ＯＨ)６ ２−イオンを調製するため、４価のＳｎの有機酸塩と、水酸化テトラアルキルアンモニウムもしくはトリアルキルアンモニウムを用いると、Ｃｌ−イオンやＮａ＋やＫ＋イオンなどの不純物が生成しないので、好ましい。 In order to prepare Sn (OH) 6 2- ion, when tetravalent Sn organic acid salt and tetraalkylammonium hydroxide or trialkylammonium hydroxide are used, impurities such as Cl − ion, Na + , K + ion, etc. Since it does not produce | generate, it is preferable.
以下に本発明を実施するための最適実施例を示す。 In the following, an optimum embodiment for carrying out the present invention will be shown.
図１〜図６に、実施例のＳｎＯ２ガスセンサの製造方法を示す。実施例では触媒をＰｄとするが、ＰｔやＲｈ，Ｒｅ，Ｒｕ，Ｉｒなどとしても良く、Ｃｕ，Ｚｎ，Ｍｏ，Ｗ，Ｃｅ，Ｌａ，Ｇａ，Ｐｂ等でもよい。図１に基本的な実施例を示す。Ｓｎ(ＣＨ３ＣＯＯ)４ を１０wt%のテトラメチルアンモニウムハイドロキサイトに溶解させた０.１Ｍの水溶液を調製した。これをポリオキシエチレン(６)ノニルフェニルエーテル(ＮＰ−６)とシクロヘキサンの混合溶液(質量比４：６)と１０℃で混合・撹拌し、[Ｓｎ(ＯＨ)６]２−を逆ミセル中に内包した逆ミセル溶液とした。ここで水重量と界面活性剤のＮＰ−６の重量比Ｒｗを９としたが、Ｒｗは例えば２〜５０程度とする。 In FIGS. 1 to 6 show a method of manufacturing SnO 2 gas sensor of Example. In the embodiment, the catalyst is Pd, but may be Pt, Rh, Re, Ru, Ir or the like, or Cu, Zn, Mo, W, Ce, La, Ga, Pb or the like. FIG. 1 shows a basic embodiment. A 0.1 M aqueous solution in which Sn (CH 3 COO) 4 was dissolved in 10 wt% tetramethylammonium hydroxide was prepared. This was mixed and stirred at 10 ° C. with a mixed solution of polyoxyethylene (6) nonylphenyl ether (NP-6) and cyclohexane (mass ratio 4: 6), and [Sn (OH) 6 ] 2- was mixed in reverse micelles. A reverse micelle solution encapsulated in Here, the weight ratio Rw of the weight of water and the surfactant NP-6 was set to 9, but the Rw is, for example, about 2 to 50.
逆ミセル溶液は、微細な水粒子(逆ミセル)が界面活性剤で疎水性の溶媒内に分散しているコロイド溶液である。なお界面活性剤中のポリエキシエチレンは(−ＣＨ２−ＣＨ２−)nの構造をし、シクロヘキサンは疎水性有機溶媒の例で、他の疎水性有機溶媒でも良い。またＳｎ酸イオンの調製に４価のＳｎの酢酸塩やプロピオン酸塩等の有機酸塩を用いると、ＳｎＣｌ４等と異なり、アニオン不純物の除去が容易である。４価のＳｎイオンは水酸化テトラメチルアンモニウムやトリメチルアンモニウム等の強アルカリ水溶液中で、Ｓｎ(ＯＨ)６ ２−（Ｓｎ酸イオン）に変化する。強アルカリとして、水酸化テトラメチルアンモニウム等を用いると、ＮａＯＨやＫＯＨなどを用いる場合と異なり、カチオン不純物の除去が容易である。 The reverse micelle solution is a colloidal solution in which fine water particles (reverse micelles) are dispersed in a hydrophobic solvent with a surfactant. Polyethylene in the surfactant has a (—CH 2 —CH 2 —) n structure, and cyclohexane is an example of a hydrophobic organic solvent, and may be another hydrophobic organic solvent. In addition, when an organic acid salt such as tetravalent Sn acetate or propionate is used for the preparation of Sn acid ions, anion impurities can be easily removed unlike SnCl 4 or the like. The tetravalent Sn ion changes to Sn (OH) 6 2− (Sn acid ion) in a strong alkaline aqueous solution such as tetramethylammonium hydroxide or trimethylammonium. When tetramethylammonium hydroxide or the like is used as a strong alkali, cationic impurities can be easily removed, unlike the case of using NaOH or KOH.
６wt%のＨＮＯ３水溶液を、同様にＮＰ−６とシクロヘキサンで逆ミセル化し、これをＳｎ酸イオンを含む逆ミセル溶液と混合・撹拌して、逆ミセル溶液中の水溶液のＰＨを弱アルカリ性〜弱酸性(ＰＨ：１０〜５で、特にＰＨ６〜８相当)とし、Ｓｎ(ＯＨ)４を析出させた。Ｓｎ(ＯＨ)４粒子は逆ミセル中で生成するので、Ｓｎ(ＯＨ)４の一次粒子が高次構造を作らずそのまま析出し、かつ粒度分布が狭い。実施例では析出したＳｎ(ＯＨ)４を熟成せずに、Ｐｄ(ＯＨ)２を担持させるが、Ｓｎ(ＯＨ)４を熟成させた後にＰｄ(ＯＨ)２を担持させても良い。なおＰＨ９〜１０相当付近でＳｎ(ＯＨ)４を析出させ、かつＲｗが大き区逆ミセルが大きい場合、Ｓｎ(ＯＨ)４の一次粒子が凝集した２次粒子として析出することがある。 A 6 wt% HNO 3 aqueous solution is similarly reverse micelle with NP-6 and cyclohexane, and this is mixed and stirred with a reverse micelle solution containing Sn acid ions, so that the pH of the aqueous solution in the reverse micelle solution is weakly alkaline to weak. It was acidified (PH: 10 to 5, particularly equivalent to PH 6 to 8), and Sn (OH) 4 was precipitated. Since Sn (OH) 4 particles are produced in reverse micelles, the primary particles of Sn (OH) 4 precipitate as they are without forming a higher order structure, and the particle size distribution is narrow. Without aging Sn (OH) 4 precipitated in the embodiment, although supporting the Pd (OH) 2, may be supported on Pd (OH) 2 after being aged the Sn (OH) 4. When Sn (OH) 4 is precipitated in the vicinity of PH 9 to 10 and Rw is large and the reverse micelle is large, the primary particles of Sn (OH) 4 may be precipitated as aggregated secondary particles.
Ｐｄ(ＮＯ３)２を希硝酸に溶解させたＰｄ濃度１ｍＭの水溶液を、同様にＮＰ−６とシクロヘキサンとで逆ミセル溶液とした。Ｒｗは例えば３としたが、２〜５０程度としても良い。Ｓｎ(ＯＨ)４の逆ミセル溶液と、Ｐｄ２＋を内包する逆ミセル溶液とを、ＳｎＯ２対Ｐｄのモル比が１００：１となるように混合した。Ｐｄ２＋イオンは中性〜アルカリ性で析出するので、逆ミセル内にＰｄ(ＯＨ)２を担持したＳｎ(ＯＨ)４粒子が析出する。なお逆ミセルの粒径分布をレーザー粒子径分布測定装置(ＬＰＡ)により測定した。 An aqueous solution having a Pd concentration of 1 mM in which Pd (NO 3 ) 2 was dissolved in dilute nitric acid was similarly made into a reverse micelle solution with NP-6 and cyclohexane. Rw is set to 3, for example, but may be about 2 to 50. A reverse micelle solution of Sn (OH) 4 and a reverse micelle solution containing Pd 2+ were mixed so that the molar ratio of SnO 2 to Pd was 100: 1. Since Pd 2+ ions are deposited in a neutral to alkaline state, Sn (OH) 4 particles carrying Pd (OH) 2 are deposited in reverse micelles. The particle size distribution of the reverse micelle was measured with a laser particle size distribution measuring device (LPA).
逆ミセル溶液を遠心分離してＳｎ(ＯＨ)４を分離し、例えば１回水洗し、１２０℃で乾燥してＰｄ−ＳｎＯ２(Ａ)粉体とした。遠心分離に代えて、メタノールなどの共通溶媒を加えて逆ミセル構造を破壊した後にろ過しても良い。乾燥後の粉体では、ＳｎＯ２〜水酸化Ｓｎ上にＰｄ粒子が担持されている。得られた粉体をペースト化し、例えば櫛形の金電極付きのアルミナ基板上にスクリーン印刷して厚膜とし、空気中６００℃で３時間焼結してガスセンサとし、メタンやＣＯ、水素等へのガス感度を測定した。なお焼結前に４００〜６００℃程度での焼成を行っても良い。分析のため、洗浄・乾燥後の粉体を空気中６００℃で３時間焼結し、Ｘ線回折や透過電子顕微鏡による観察を行った。 The reverse micelle solution was centrifuged to separate Sn (OH) 4 , for example, washed once with water and dried at 120 ° C. to obtain Pd—SnO 2 (A) powder. Instead of centrifugation, filtration may be performed after adding a common solvent such as methanol to destroy the reverse micelle structure. In the powder after drying, Pd particles are supported on SnO 2 to Sn hydroxide. The obtained powder is pasted, for example, screen-printed on an alumina substrate with a comb-shaped gold electrode to form a thick film, sintered in air at 600 ° C. for 3 hours to form a gas sensor, and applied to methane, CO, hydrogen, etc. Gas sensitivity was measured. In addition, you may perform baking at about 400-600 degreeC before sintering. For analysis, the washed and dried powder was sintered in air at 600 ° C. for 3 hours and observed by X-ray diffraction or a transmission electron microscope.
図２に、変形例でのＰｄ担持のＳｎＯ２の製造方法を示す。図１と同様にしてＳｎ酸水溶液を調製し、逆ミセル化する。Ｐｄ(ＮＯ３)２の水溶液と６wt%のＨＮＯ３の水溶液とを混合して、Ｐｄ２＋の酸性水溶液を調製する。これを図１の実施例と同様に逆ミセル化し、２つの逆ミセル溶液を混合・撹拌する。Ｓｎ酸イオンは弱アルカリ性〜酸性で析出し、Ｐｄ２＋イオンは弱酸性〜アルカリ性で析出するので、逆ミセル溶液の混合により、Ｓｎ(ＯＨ)４とＰｄ(ＯＨ)２とが同時に析出する。そしてここで存在量が少ないＰｄ(ＯＨ)２はＳｎ(ＯＨ)４上に析出する。次いで逆ミセル溶液からＰｄ担持のＳｎ(ＯＨ)４を分離し、図１と同様にして洗浄・乾燥し、成膜・焼結してＰｄ−ＳｎＯ２(Ａ)粉体とし、ガスセンサとする。 Figure 2 shows a Pd SnO 2 of the method for manufacturing the bearing of a modification. An aqueous Sn acid solution is prepared in the same manner as in FIG. An acidic aqueous solution of Pd 2+ is prepared by mixing an aqueous solution of Pd (NO 3 ) 2 and an aqueous solution of 6 wt% HNO 3 . This is reverse micelle as in the embodiment of FIG. 1, and the two reverse micelle solutions are mixed and stirred. Since Sn acid ions are precipitated with weak alkalinity to acidity, and Pd 2+ ions are precipitated with weak acidity to alkalinity, Sn (OH) 4 and Pd (OH) 2 are simultaneously precipitated by mixing the reverse micelle solution. Here, Pd (OH) 2 having a small abundance is deposited on Sn (OH) 4 . Next, Pd-supported Sn (OH) 4 is separated from the reverse micelle solution, washed and dried in the same manner as in FIG. 1, and formed into a film and sintered to form Pd—SnO 2 (A) powder, which is used as a gas sensor.
図３にレーザー粒子径分布測定装置で測定した逆ミセルの粒子径分布を示し、試料は図１の実施例によるもので、図３(Ａ)ではＰｄ２＋イオンの逆ミセルをＲｗ＝９で調製し、(Ｂ)ではＲｗ＝３で調製した。図３(Ａ)では、混合後の逆ミセルの平均粒子径は混合前の平均粒子径と基本的に変わらず、(Ｂ)では、混合後の平均粒子径は混合前の平均粒子径の中間の値となっている。 Shows the particle size distribution of the reverse micelles measured by a laser particle size distribution measuring device in FIG. 3, the sample is due to the embodiment of FIG. 1, prepared reversed micelle shown in FIG. 3 (A) the Pd 2+ ions at Rw = 9 In (B), it was prepared with Rw = 3. In FIG. 3 (A), the average particle size of the reverse micelle after mixing is basically the same as the average particle size before mixing. In (B), the average particle size after mixing is the middle of the average particle size before mixing. It is the value of.
６００℃焼成後のＳｎＯ２中でのＰｄ含有量を蛍光Ｘ線で分析し、洗浄回数が１回程度であれば、Ｐｄの仕込量のほぼ全量がＳｎＯ２中に担持される(Ｐｄ濃度１モル％)ことが判明した。図４に、６００℃焼成後のＰｄ−ＳｎＯ２(Ａ)及びＰｄ−ＳｎＯ２(Ｂ)、並びにＳｎＣｌ４の水溶液をアンモニア水で中和し、得られたＳｎ酸ゾルを洗浄・乾燥後に６００℃で焼成した試料の、Ｘ線回折パターンを示す。図中にシェラーの式から求めた平均結晶子径を示す。いずれの試料でも、ＳｎＯ２単一相のＸ線回折像が得られている。 When the Pd content in SnO 2 after firing at 600 ° C. is analyzed by fluorescent X-rays, if the number of washings is about once, almost the entire amount of Pd charged is supported in SnO 2 (Pd concentration 1 Mol%). In FIG. 4, an aqueous solution of Pd—SnO 2 (A), Pd—SnO 2 (B), and SnCl 4 after baking at 600 ° C. is neutralized with aqueous ammonia, and the resulting Sn acid sol is cleaned and dried after being dried. The X-ray diffraction pattern of the sample baked at ° C is shown. The average crystallite diameter determined from the Scherrer equation is shown in the figure. In any sample, an X-ray diffraction image of SnO 2 single phase is obtained.
図５に、Ｐｄ−ＳｎＯ２(Ａ)及びＰｄ−ＳｎＯ２(Ｂ)の高分解能透過電子顕微鏡写真を示す。Ｐｄ−ＳｎＯ２(Ａ)では、ＳｎＯ２結晶子以外にＰｄＯと考えられる８〜１０nm程度の粒子が見られた。これに対してＰｄ−ＳｎＯ２(Ｂ)では、ＳｎＯ２粒子以外には数nm以下のＰｄＯ粒子が見られた。このことはＰｄ−ＳｎＯ２(Ｂ)でより微細なＰｄＯがＳｎＯ２上に担持されていることを示し、Ｓｎ(ＯＨ)４とＰｄ(ＯＨ)２を同時に析出させるよりも、予めＳｎ(ＯＨ)４を析出させた後に、Ｐｄ(ＯＨ)２を析出させることが好ましいことを示している。 FIG. 5 shows high-resolution transmission electron micrographs of Pd—SnO 2 (A) and Pd—SnO 2 (B). In Pd—SnO 2 (A), particles of about 8 to 10 nm, which are considered to be PdO, were seen in addition to the SnO 2 crystallites. On the other hand, in Pd—SnO 2 (B), PdO particles of several nm or less were seen in addition to SnO 2 particles. This indicates that a finer PdO in Pd-SnO 2 (B) are supported on SnO 2, than to precipitate Sn (OH) 4 and Pd (OH) 2 at the same time, pre-Sn (OH This shows that it is preferable to deposit Pd (OH) 2 after 4 is deposited.
図６に、従来法のＳｎＯ２と、Ｐｄ−ＳｎＯ２(Ａ)、並びにＰｄ−ＳｎＯ２(Ｂ)の抵抗値の温度依存性を示す。図の縦軸はログスケールで、ＳｎＯ２厚膜の抵抗値を示し、測定雰囲気は空気中である。Ｐｄ−ＳｎＯ２(Ｂ)はＰｄ−ＳｎＯ２(Ａ)よりも高抵抗で、このことはＰｄＯ粒子がナノ粒子として高分散しているため、吸着酸素イオン量が増加していることを示している。 Figure 6 illustrates a SnO 2 of the prior art, Pd-SnO 2 (A), as well as the temperature dependence of the resistance value of Pd-SnO 2 (B). The vertical axis in the figure is a log scale, showing the resistance value of the SnO 2 thick film, and the measurement atmosphere is in the air. Pd—SnO 2 (B) has a higher resistance than Pd—SnO 2 (A), which indicates that the amount of adsorbed oxygen ions is increased because the PdO particles are highly dispersed as nanoparticles. Yes.
図７に、従来法のＳｎＯ２とＰｄ−ＳｎＯ２(Ｂ)のＣＯ感度(ＣＯ １０００ｐｐｍ)を示す。いずれの試料でもＳｎＯ２に対しＰｄを１モル％添加し、従来法では、ＳｎＣｌ４の水溶液をアンモニア水で中和し、得られたＳｎ酸ゾルを洗浄・乾燥後に６００℃で焼成して、ＳｎＯ２とした。このＳｎＯ２にＰｄＮＯ３の水溶液を含浸させ、乾燥後に空気中５５０℃で焼成して、ＰｄをＳｎＯ２に担持させた。Ｐｄ−ＳｎＯ２(Ｂ)では微細なＰｄ粒子がＳｎＯ２に均一に分散しているため、高感度である。なおＰｄ−ＳｎＯ２(Ａ)では、Ｐｄ−ＳｎＯ２(Ｂ)と従来法のＳｎＯ２の中間の感度を示した。 FIG. 7 shows the CO sensitivity (CO 1000 ppm) of SnO 2 and Pd—SnO 2 (B) of the conventional method. In any sample, 1 mol% of Pd was added to SnO 2 , and in the conventional method, an aqueous solution of SnCl 4 was neutralized with ammonia water, and the obtained Sn acid sol was baked at 600 ° C. after washing and drying, SnO 2 was used. This SnO 2 was impregnated with an aqueous solution of PdNO 3 , dried and fired at 550 ° C. in the air to support Pd on SnO 2 . Pd—SnO 2 (B) has high sensitivity because fine Pd particles are uniformly dispersed in SnO 2 . In Pd—SnO 2 (A), an intermediate sensitivity between Pd—SnO 2 (B) and conventional SnO 2 was shown.
実施例ではＰｄ触媒の添加を示したが、Ｐｄに代えてＰｔ，Ｒｈ等の他の貴金属触媒の添加でも同様である。また逆ミセルと触媒金属の水酸化物を経由した担持法は、貴金属触媒に限らず、遷移金属触媒や、ランタニド触媒、Ｇａ，Ｉｎ等の３価の典型金属触媒やＧｅ，Ｐｂ等の４価の典型金属触媒にも用いることができる。これらの何れの触媒でも、金属イオンは酸性の逆ミセル内で可溶で、弱酸性ないし弱アルカリ性、特に中性付近の逆ミセル内で不溶なので、Ｓｎ(ＯＨ)４上に析出する。
In the examples, the addition of the Pd catalyst was shown, but the same applies to the addition of other noble metal catalysts such as Pt and Rh instead of Pd. The supporting method via reverse micelle and catalytic metal hydroxide is not limited to a noble metal catalyst, but a transition metal catalyst, a lanthanide catalyst, a trivalent typical metal catalyst such as Ga and In, and a tetravalent metal such as Ge and Pb. It can also be used as a typical metal catalyst. In any of these catalysts, metal ions are soluble in acidic reverse micelles and are weakly acidic or weakly alkaline, particularly insoluble in reverse micelles near neutrality, and therefore precipitate on Sn (OH) 4 .
Claims (3)
次いで触媒金属の水酸化物を析出させたＳｎ(ＯＨ)４を混合逆ミセル溶液から分離、乾燥して、触媒を担持させたＳｎＯ２もしくは水酸化スズの粉体とし、
該粉体を電極と接続した形状に成形・焼成してガスセンサとする、ＳｎＯ２ガスセンサの製造方法。 By mixing a reverse micelle solution containing Sn (OH) 6 2- ion in an alkaline reverse micelle and a reverse micelle solution containing a catalytic metal ion in an acidic reverse micelle, Sn (OH) 6 OH) 4 to form a mixed reverse micelle solution in which a catalyst metal hydroxide is precipitated,
Next, Sn (OH) 4 on which the catalyst metal hydroxide is precipitated is separated from the mixed reverse micelle solution and dried to obtain SnO 2 or tin hydroxide powder supporting the catalyst,
A method for producing a SnO 2 gas sensor, wherein the powder is molded and fired into a shape connected to an electrode to form a gas sensor.
該混合逆ミセル溶液と、触媒金属イオンを酸性の逆ミセル中に含有する逆ミセル溶液とを混合することにより、逆ミセル中でＳｎ(ＯＨ)４上に触媒金属の水酸化物を析出させた第２の混合逆ミセル溶液とし、
次いで触媒金属の水酸化物を析出させたＳｎ(ＯＨ)４を第２の混合逆ミセル溶液から分離、乾燥して、触媒を担持させたＳｎＯ２もしくは水酸化スズの粉体とし、
該粉体を電極と接続した形状に成形・焼成してガスセンサとする、ＳｎＯ２ガスセンサの製造方法。 A reverse mixed solution in which a reverse micelle solution containing Sn (OH) 6 2- ion in an alkaline reverse micelle and a reverse micelle solution of an acidic reverse micelle are mixed to precipitate Sn (OH) 4 in the reverse micelle. A micellar solution,
The mixed reverse micelle solution and a reverse micelle solution containing catalytic metal ions in acidic reverse micelles were mixed to precipitate a catalytic metal hydroxide on Sn (OH) 4 in the reverse micelles. A second mixed reverse micelle solution;
Next, Sn (OH) 4 on which the catalyst metal hydroxide is precipitated is separated from the second mixed reverse micelle solution and dried to obtain SnO 2 or tin hydroxide powder supporting the catalyst.
A method for producing a SnO 2 gas sensor, wherein the powder is molded and fired into a shape connected to an electrode to form a gas sensor.
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