JP2014161943A - Platinum nanoparticle-coated fine particle, method for manufacturing platinum nanoparticle-coated fine particle - Google Patents
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 title claims abstract description 619
- 229910052697 platinum Inorganic materials 0.000 title claims abstract description 303
- 239000010419 fine particle Substances 0.000 title claims abstract description 220
- 239000002105 nanoparticle Substances 0.000 title claims abstract description 173
- 238000004519 manufacturing process Methods 0.000 title claims description 26
- 238000000034 method Methods 0.000 title description 9
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims abstract description 110
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 75
- 229910052763 palladium Inorganic materials 0.000 claims abstract description 55
- 239000002243 precursor Substances 0.000 claims abstract description 37
- 230000009467 reduction Effects 0.000 claims abstract description 33
- 239000002245 particle Substances 0.000 claims description 41
- 239000003054 catalyst Substances 0.000 claims description 29
- 230000001603 reducing effect Effects 0.000 claims description 28
- OAKJQQAXSVQMHS-UHFFFAOYSA-N hydrazine group Chemical group NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 claims description 16
- 230000000694 effects Effects 0.000 claims description 14
- 239000012279 sodium borohydride Substances 0.000 claims description 9
- 229910000033 sodium borohydride Inorganic materials 0.000 claims description 9
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical group O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 8
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 7
- 239000002270 dispersing agent Substances 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 claims description 6
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 claims description 4
- 229910052814 silicon oxide Inorganic materials 0.000 claims description 3
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 3
- 229910001887 tin oxide Inorganic materials 0.000 claims description 2
- 230000015572 biosynthetic process Effects 0.000 claims 1
- 239000003795 chemical substances by application Substances 0.000 claims 1
- 230000003197 catalytic effect Effects 0.000 abstract description 6
- 239000000463 material Substances 0.000 abstract description 5
- 229910010413 TiO 2 Inorganic materials 0.000 description 41
- 239000000243 solution Substances 0.000 description 34
- 229910004298 SiO 2 Inorganic materials 0.000 description 32
- 239000007864 aqueous solution Substances 0.000 description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 20
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 18
- 239000007788 liquid Substances 0.000 description 18
- 239000011859 microparticle Substances 0.000 description 15
- 238000003756 stirring Methods 0.000 description 15
- 239000002253 acid Substances 0.000 description 14
- 229910044991 metal oxide Inorganic materials 0.000 description 14
- 150000004706 metal oxides Chemical class 0.000 description 14
- 239000000084 colloidal system Substances 0.000 description 13
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 9
- 238000009826 distribution Methods 0.000 description 9
- 238000011282 treatment Methods 0.000 description 9
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 8
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 8
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 8
- 239000000203 mixture Substances 0.000 description 7
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 238000000746 purification Methods 0.000 description 6
- 239000003153 chemical reaction reagent Substances 0.000 description 5
- 238000005342 ion exchange Methods 0.000 description 5
- 229910000510 noble metal Inorganic materials 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- 239000000969 carrier Substances 0.000 description 4
- 238000005119 centrifugation Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine hydrate Chemical compound O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-N 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 241000282994 Cervidae Species 0.000 description 2
- BAVYZALUXZFZLV-UHFFFAOYSA-N Methylamine Chemical compound NC BAVYZALUXZFZLV-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 239000002082 metal nanoparticle Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 238000011946 reduction process Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 239000004408 titanium dioxide Substances 0.000 description 2
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 1
- 238000010669 acid-base reaction Methods 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- MOOAHMCRPCTRLV-UHFFFAOYSA-N boron sodium Chemical compound [B].[Na] MOOAHMCRPCTRLV-UHFFFAOYSA-N 0.000 description 1
- RJTANRZEWTUVMA-UHFFFAOYSA-N boron;n-methylmethanamine Chemical compound [B].CNC RJTANRZEWTUVMA-UHFFFAOYSA-N 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000007613 environmental effect Effects 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
- 238000007654 immersion Methods 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 1
- 239000002071 nanotube Substances 0.000 description 1
- 231100000989 no adverse effect Toxicity 0.000 description 1
- SOQBVABWOPYFQZ-UHFFFAOYSA-N oxygen(2-);titanium(4+) Chemical compound [O-2].[O-2].[Ti+4] SOQBVABWOPYFQZ-UHFFFAOYSA-N 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- ACVYVLVWPXVTIT-UHFFFAOYSA-M phosphinate Chemical compound [O-][PH2]=O ACVYVLVWPXVTIT-UHFFFAOYSA-M 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229920000371 poly(diallyldimethylammonium chloride) polymer Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
Abstract
Description
本発明は白金ナノ粒子被覆微粒子とその製造方法に関し、さらに具体的には、白金前駆体を複数段階で異種の還元剤を用いて還元した白金ナノ粒子被覆微粒子とその製造方法に関する。 The present invention relates to platinum nanoparticle-coated fine particles and a method for producing the same, and more specifically to platinum nanoparticle-coated fine particles obtained by reducing a platinum precursor in a plurality of steps using different kinds of reducing agents and a method for producing the same.
近年粒子サイズが１００ｎｍ以下の金属ナノ粒子が、同種のバルク金属が有する物性とは異なる物性を有したり、体積に比してきわめて大きな表面積を有していたりするなど、その有するナノ粒子特有の特徴の活用に大きな期待が集まり、触媒を始め、工業分野における利用可能性が期待され、多くの改善が提案されている。白金などの貴金属を利用する活用分野では体積に対する表面積の大きさに注目され、触媒への利用が進められている。 In recent years, metal nanoparticles with a particle size of 100 nm or less have physical properties different from those of the same kind of bulk metal, or have a very large surface area relative to the volume. There are great expectations for the use of features, and the possibility of use in the industrial field including catalysts is expected, and many improvements have been proposed. In the field of utilization using noble metals such as platinum, attention has been paid to the size of the surface area relative to the volume, and the utilization for catalysts has been promoted.
貴金属のナノ粒子を工業利用する場合、その性能の高さに期待が集まると同時に、コストが高いことが問題になる。例えば白金を使用していた触媒のための物質として白金を代替する物質の発明を試みたり、白金の使用量を減らすなど、コスト低減が期待されている。 In the case of industrial use of noble metal nanoparticles, high performance is expected and at the same time high cost becomes a problem. For example, attempts are being made to invent a substance that substitutes platinum as a substance for a catalyst that uses platinum, and reductions in cost are expected, such as reducing the amount of platinum used.
特許文献１には、自動車の排ガス浄化用触媒に用いられるシリカ（酸化ケイ素）（ＳｉＯ2）粉末、酸化チタン（ＴｉＯ2）、酸化ジルコニウム（ＺｒＯ2）等に担持させた白金が記載されている。白金を浸漬で担持させている。 Patent Document 1 describes platinum supported on silica (silicon oxide) (SiO 2 ) powder, titanium oxide (TiO 2 ), zirconium oxide (ZrO 2 ), etc., used for automobile exhaust gas purification catalysts. . Platinum is supported by immersion.
特許文献２には、色素増感太陽電池等の光電変換素子の正極材料用に、酸化チタンナノチューブや酸化チタン微粒子に担持させた白金ナノ粒子が記載されている。白金ナノ粒子は白金微粒子前駆体を特に制限されない還元剤を用いて還元したものを用いている。白金を一種類の還元剤を用いて担持させている。 Patent Document 2 describes platinum nanoparticles supported on titanium oxide nanotubes or titanium oxide fine particles for a positive electrode material of a photoelectric conversion element such as a dye-sensitized solar cell. The platinum nanoparticle is obtained by reducing a platinum fine particle precursor using a reducing agent that is not particularly limited. Platinum is supported using one type of reducing agent.
白金微粒子触媒の性能改善がとりわけ期待されているのが固体高分子燃料電池の正極である。正極では酸素分子が還元されて水に変化する反応が起こるが、既存の白金触媒では活性が低いことが課題となっている。電池に必要な酸素還元速度を達成するためには多量の白金触媒の担持を必要とし、白金使用量の低減とコストダウンを妨げる最も大きな原因となっている。 The positive electrode of the solid polymer fuel cell is particularly expected to improve the performance of the platinum fine particle catalyst. The positive electrode undergoes a reaction in which oxygen molecules are reduced to water, but the existing platinum catalyst has a low activity. In order to achieve the oxygen reduction rate required for the battery, it is necessary to support a large amount of platinum catalyst, which is the biggest cause of hindering the reduction in the amount of platinum used and the cost reduction.
白金を用いた正極触媒の改善や白金を用いない正極触媒材料の探索が精力的に行われているが、現在のところ劇的なブレイクスルーは達成されていない。触媒活性の向上のための工夫のひとつとして白金触媒が担持されている担体を検討することが考えられる。貴金属微粒子を用いる有機合成反応および環境浄化触媒においては、目的とする反応に最適な担体を選択することにより著しい活性向上が期待できる場合もある。その一方で燃料電池触媒においては白金微粒子が担持される担体はカーボン系のものが主流であり、酸化物担体をはじめとするセラミックス系の物質はあまり検討されてこなかった。その理由は、カーボン系の担体は酸に耐性を有し、安価で導電性をもつのに対し、酸化物担体は酸に弱いものや絶縁体のものもあるからである。 Improvement of the positive electrode catalyst using platinum and search for a positive electrode catalyst material not using platinum have been energetically performed, but at present, a dramatic breakthrough has not been achieved. As one of the ideas for improving the catalytic activity, it is conceivable to examine a support on which a platinum catalyst is supported. In an organic synthesis reaction and environmental purification catalyst using noble metal fine particles, there may be a case where significant activity improvement can be expected by selecting an optimal carrier for the intended reaction. On the other hand, for fuel cell catalysts, carbon-based carriers on which platinum fine particles are supported are mainly used, and ceramic-based materials such as oxide carriers have not been studied much. The reason for this is that carbon-based carriers are resistant to acids, are inexpensive and have conductivity, whereas oxide carriers are weak against acids and are insulators.
しかし、酸化物担体は酸塩基反応や酸化還元反応において重要な酸点と塩基点を独特な幾何学的配置でもつのが特徴的であり、適切な金属微粒子との組み合わせにより優れた触媒活性を示すことがある。また、導電性の問題については酸化物担体の一部または全ての表面を導通を保ちながら覆うことで解決できる。白金の使用量を抑え、高い活性を保ちつつ電気的な接続を有する複合微粒子を合成することが酸化物担体を利用する際の重要なポイントである。 However, the oxide carrier is characterized by a unique geometrical arrangement of acid and base points that are important in acid-base reactions and redox reactions, and exhibits excellent catalytic activity when combined with appropriate metal fine particles. Sometimes. Further, the problem of conductivity can be solved by covering a part or all of the surface of the oxide carrier while maintaining conduction. It is an important point when using the oxide carrier to synthesize composite fine particles having an electrical connection while suppressing the amount of platinum used and maintaining high activity.
工業的レベルで金属酸化物微粒子の表面に白金ナノ粒子を担持させることは実際には簡単ではなく、多くの試みが行われており、未だ解決されていないのが実情である。その結果、今もって多くの特許が提案され続けている。本発明者らも、後述するように、ＳｉＯ2やＴｉＯ2などの金属酸化物微粒子の表面に白金ナノ粒子を担持させるべく、金属酸化物の微粒子を含む溶液に、分散剤たとえばＰＶＰ（ポリビニルピロリドン）を混ぜ、ＰＶＰで表面処理したＳｉＯ2コロイド液を作製し、遠心分離処理で取り出した粒子にイオン交換水を混ぜたものに白金前駆体としての塩化白金酸を加え、還元力が強い水素化ホウ素ナトリウムを用いて還元操作を行って、白金で被覆した金属酸化物微粒子を作製しようと試みた。また、還元剤を他の還元剤、例えばヒドラジンに変えて、ＳｉＯ2やＴｉＯ2等の金属酸化物微粒子表面をＰＶＰで表面処理したコロイド液を作製し、遠心分離処理で取り出した粒子にイオン交換水を混ぜたものに白金前駆体としての塩化白金酸を加えた液にこの還元剤を入れて還元操作を行ってみた。 It is actually not easy to support platinum nanoparticles on the surface of metal oxide fine particles at an industrial level, and many attempts have been made and the situation has not been solved yet. As a result, many patents continue to be proposed. As will be described later, the present inventors have also added a dispersant such as PVP (polyvinylpyrrolidone) in a solution containing metal oxide fine particles to support platinum nanoparticles on the surface of metal oxide fine particles such as SiO 2 and TiO 2. ) To prepare a SiO 2 colloidal solution surface-treated with PVP, and then add chloroplatinic acid as a platinum precursor to the particles extracted by centrifugation and mixed with ion-exchanged water. An attempt was made to produce metal oxide fine particles coated with platinum by performing a reduction operation using sodium boron. In addition, by changing the reducing agent to another reducing agent, such as hydrazine, a colloidal liquid is prepared by treating the surface of metal oxide fine particles such as SiO 2 and TiO 2 with PVP, and ion exchange is performed on the particles taken out by centrifugation. This reducing agent was added to a solution obtained by adding chloroplatinic acid as a platinum precursor to a mixture of water, and a reduction operation was performed.
しかし、金属酸化物微粒子の表面に白金ナノ粒子がある程度担持されるとそれ以上の担持が行われなくなるという現象がみられた。そして、反応が止まったこの液に対して遠心処理を行い、取り出した粒子に再びイオン交換水を加えて同様の還元を試みても、金属酸化物微粒子の表面に白金が追加して担持されず、金属酸化物微粒子の表面に白金で良好に被覆された白金被覆金属酸化物を得ることはできないという壁に突き当たった。 However, when platinum nanoparticles were supported to some extent on the surface of the metal oxide fine particles, a phenomenon was observed in which further support was not performed. Then, the liquid that has stopped reacting is centrifuged, and ion exchange water is added again to the removed particles to try the same reduction, but platinum is not additionally supported on the surface of the metal oxide fine particles. Then, it hit a wall that the surface of the metal oxide fine particles could not obtain a platinum-coated metal oxide well coated with platinum.
このように、白金ナノ粒子を金属酸化物微粒子の表面に触媒作用等白金ナノ粒子に近い効果を発揮できるように担持させることはきわめて難しいことである。触媒などに使用されている白金ナノ粒子は、触媒などの効果は著しいが、高価であるという経済的な欠点が大きな問題になっており、白金の使用量を減らすか白金以外の触媒等の効果の大きな材料の発見が解決すべき重要な課題となって久しい。 As described above, it is extremely difficult to support the platinum nanoparticles on the surface of the metal oxide fine particles so as to exhibit an effect close to that of the platinum nanoparticles such as catalytic action. Platinum nanoparticles used in catalysts, etc. have a remarkable effect as a catalyst, but the economic disadvantage of being expensive is a big problem, and the effect of reducing the amount of platinum used or catalysts other than platinum The discovery of large materials has long been an important issue to be solved.
上記の事情に鑑み、本発明の解決すべき課題は、自動車の排ガス浄化用触媒や電池用触媒などに用いる白金とは異なる素材の微粒子を下地として、下地の周囲に白金ナノ粒子で被覆し、白金ナノ粒子に近い効果を発揮できる、白金ナノ粒子被覆微粒子を安価に提供することにある。 In view of the above circumstances, the problem to be solved by the present invention is to coat fine particles of a material different from platinum used as an exhaust gas purification catalyst for automobiles, a catalyst for batteries, etc., and coat the periphery of the base with platinum nanoparticles, The object is to provide low-cost platinum nanoparticle-coated fine particles that can exhibit an effect close to that of platinum nanoparticles.
課題を解決するため、本発明者らは後記のような種々の検討を行い、下地となる白金及び／又はパラジウム以外の微粒子に白金を従来では期待のできないほどに被覆状態で担持させることに成功した。 In order to solve the problem, the present inventors have made various studies as described below, and succeeded in supporting platinum in a coated state to a degree that would not be expected in the past on platinum and / or fine particles other than palladium. did.
課題を解決するためになされた本発明の第１の実施の形態例及び発明（以下、発明１という）は、白金及び／又はパラジウム以外の微粒子を中心にして、その周囲に白金ナノ粒子を担持させて作製した白金ナノ粒子被覆微粒子において、前記白金ナノ粒子被覆微粒子を構成する白金ナノ粒子が、第１の白金前駆体を第１の還元剤によって還元して前記白金及び／又はパラジウム以外の微粒子の表面に形成した第１の白金ナノ粒子層と、前記第１の白金ナノ粒子層を形成した後、第２の白金前駆体を第１の還元剤とは還元作用の異なる第２の還元剤によって還元して前記白金及び／又はパラジウム以外の微粒子の表面に形成した第２の白金ナノ粒子層を少なくとも有することを特徴とする白金ナノ粒子被覆微粒子である。 The first embodiment of the present invention and the invention (hereinafter referred to as Invention 1) made to solve the problems are centered on fine particles other than platinum and / or palladium, and platinum nanoparticles are supported around the fine particles. In the platinum nanoparticle-coated fine particles produced by the above process, the platinum nanoparticles constituting the platinum nanoparticle-coated fine particles reduce the first platinum precursor with a first reducing agent, and the fine particles other than platinum and / or palladium. After forming the first platinum nanoparticle layer formed on the surface of the first platinum nanoparticle layer, the second reducing agent having a reducing action different from that of the first reducing agent is applied to the second platinum precursor. A platinum nanoparticle-coated fine particle characterized by having at least a second platinum nanoparticle layer formed on the surface of the fine particle other than platinum and / or palladium by reduction by the above.
課題を解決するためになされた本発明の第２の実施の形態例及び発明（以下、発明２という）は、白金及び／又はパラジウム以外の微粒子を中心にして、その周囲に白金ナノ粒子を担持させて作製した白金ナノ粒子被覆微粒子において、前記白金ナノ粒子被覆微粒子を構成する白金ナノ粒子が、第１の白金前駆体を第１の還元剤によって還元して前記白金及び／又はパラジウム以外の微粒子の表面に核を形成した第１の白金ナノ粒子層と、前記第１の白金ナノ粒子層を形成した後、第２の白金前駆体を第１の還元剤とは還元作用の異なる第２の還元剤によって還元して前記白金及び／又はパラジウム以外の微粒子の表面に被覆状態にした第２の白金ナノ粒子層を少なくとも有することを特徴とする白金ナノ粒子被覆微粒子である。 In order to solve the problem, the second embodiment of the present invention and the invention (hereinafter referred to as invention 2) are mainly composed of fine particles other than platinum and / or palladium, and platinum nanoparticles are supported around the fine particles. In the platinum nanoparticle-coated fine particles produced by the above process, the platinum nanoparticles constituting the platinum nanoparticle-coated fine particles reduce the first platinum precursor with a first reducing agent, and the fine particles other than platinum and / or palladium. After forming the first platinum nanoparticle layer having nuclei formed on the surface thereof and the first platinum nanoparticle layer, the second platinum precursor is converted into a second reductant having a reducing action different from that of the first reducing agent. A platinum nanoparticle-coated fine particle characterized by having at least a second platinum nanoparticle layer coated on the surface of the fine particle other than platinum and / or palladium by reducing with a reducing agent.
発明１又は２を展開してなされた本発明の第３の実施の形態例及び発明（以下、発明３という）は、発明１または２に記載の白金ナノ粒子被覆微粒子において、前記第１の白金前駆体と第２の白金前駆体が同一種類の前駆体であることを特徴とする白金ナノ粒子被覆微粒子である。 The third embodiment of the present invention and the invention (hereinafter referred to as invention 3) made by developing invention 1 or 2 are the platinum nanoparticle-coated fine particles according to invention 1 or 2, wherein the first platinum A platinum nanoparticle-coated fine particle, wherein the precursor and the second platinum precursor are the same type of precursor.
発明１〜３を展開してなされた本発明の第４の実施の形態例及び発明（以下、発明４という）は、発明１〜３のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記白金及び／又はパラジウム以外の微粒子の表面が分散剤によって覆われており、その表面に白金ナノ粒子で被覆されていることを特徴とする白金ナノ粒子被覆微粒子である。 The fourth embodiment of the present invention and the invention (hereinafter referred to as invention 4) made by developing inventions 1 to 3 are the platinum nanoparticle-coated fine particles according to any one of inventions 1 to 3, The surface of the fine particles other than the platinum and / or palladium is covered with a dispersant, and the surface is coated with platinum nanoparticles.
発明１〜４を展開してなされた本発明の第５の実施の形態例及び発明（以下、発明５という）は、発明１〜４のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記白金及び／又はパラジウム以外の微粒子が酸化ケイ素であることを特徴とする白金ナノ粒子被覆微粒子である。 The fifth embodiment of the present invention and the invention (hereinafter referred to as invention 5) made by developing inventions 1 to 4 are the platinum nanoparticle-coated fine particles according to any one of inventions 1 to 4, The platinum nanoparticle-coated fine particles, wherein the fine particles other than platinum and / or palladium are silicon oxide.
発明１〜４を展開してなされた本発明の第６の実施の形態例及び発明（以下、発明６という）は、発明１〜４のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記白金及び／又はパラジウム以外の微粒子が酸化チタンであることを特徴とする白金ナノ粒子被覆微粒子である。 The sixth embodiment of the present invention and the invention (hereinafter referred to as invention 6) made by developing inventions 1-4 are the platinum nanoparticle-coated fine particles according to any one of inventions 1-4, The platinum nanoparticle-coated fine particles, wherein the fine particles other than platinum and / or palladium are titanium oxide.
発明１〜４を展開してなされた本発明の第７の実施の形態例及び発明（以下、発明７という）は、発明１〜４のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記白金及び／又はパラジウム以外の微粒子が酸化スズであることを特徴とする白金ナノ粒子被覆微粒子である。 The seventh embodiment of the present invention and the invention (hereinafter referred to as invention 7) made by developing inventions 1-4 are the platinum nanoparticle-coated fine particles according to any one of inventions 1-4, The platinum nanoparticle-coated fine particles, wherein the fine particles other than platinum and / or palladium are tin oxide.
発明１〜４を展開してなされた本発明の第８の実施の形態例及び発明（以下、発明８という）は、発明１〜４のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記白金及び／又はパラジウム以外の微粒子が導電性微粒子であることを特徴とする白金ナノ粒子被覆微粒子である。 The eighth embodiment of the present invention and the invention (hereinafter referred to as invention 8) made by developing inventions 1-4 are the platinum nanoparticle-coated fine particles according to any one of inventions 1-4, The platinum nanoparticle-coated fine particles, wherein the fine particles other than platinum and / or palladium are conductive fine particles.
発明８を展開してなされた本発明の第９の実施の形態例及び発明（以下、発明９という）は、発明８に記載の白金ナノ粒子被覆微粒子において、前記白金及び／又はパラジウム以外の微粒子が炭素であることを特徴とする白金ナノ粒子被覆微粒子である。 The ninth embodiment of the present invention and the invention (hereinafter referred to as Invention 9), which are made by developing Invention 8, are the platinum nanoparticle-coated fine particles according to Invention 8, wherein the fine particles other than platinum and / or palladium are used. Is a fine particle coated with platinum nanoparticles, characterized in that is carbon.
発明１〜９を展開してなされた本発明の第１０の実施の形態例及び発明（以下、発明１０という）は、発明１〜９のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記第２の還元剤の標準電極電位より前記第１の還元剤の標準電極電位がその絶対値において大きい値を示すことを特徴とする白金ナノ粒子被覆微粒子である。 The tenth embodiment of the present invention and the invention (hereinafter referred to as invention 10) made by developing the inventions 1 to 9 are the platinum nanoparticle-coated fine particles according to any one of the inventions 1 to 9, The platinum nanoparticle-coated fine particles characterized in that the standard electrode potential of the first reducing agent is greater in absolute value than the standard electrode potential of the second reducing agent.
発明１〜１０を展開してなされた本発明の第１１の実施の形態例及び発明（以下、発明１１という）は、発明１〜１０のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記第１の還元剤が水素化ホウ素ナトリウムであり前記第２の還元剤がヒドラジンであることを特徴とする白金ナノ粒子被覆微粒子である。 The eleventh embodiment of the present invention and the invention (hereinafter referred to as Invention 11) made by developing Inventions 1 to 10 are the platinum nanoparticle-coated fine particles according to any one of Inventions 1 to 10, The platinum nanoparticle-coated fine particles, wherein the first reducing agent is sodium borohydride and the second reducing agent is hydrazine.
発明１〜１１を展開してなされた本発明の第１２の実施の形態例及び発明（以下、発明１２という）は、発明１〜１１のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記白金及び／又はパラジウム以外の微粒子の最大寸法の平均値が１０ｎｍ〜５００ｎｍであることを特徴とする白金ナノ粒子被覆微粒子である。 The twelfth embodiment of the present invention and the invention (hereinafter referred to as invention 12) made by developing the inventions 1 to 11 are the platinum nanoparticle-coated fine particles according to any one of the inventions 1 to 11, The platinum nanoparticle-coated fine particles, wherein the average value of the maximum dimension of fine particles other than platinum and / or palladium is 10 nm to 500 nm.
発明１〜１２を展開してなされた本発明の第１３の実施の形態例及び発明（以下、発明１３という）は、発明１〜１２のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記白金ナノ粒子被覆微粒子が電池用触媒としての効果を有することを特徴とする白金ナノ粒子被覆微粒子である。 The thirteenth embodiment of the present invention and the invention (hereinafter referred to as invention 13) made by developing inventions 1 to 12 are the platinum nanoparticle-coated fine particles according to any one of inventions 1 to 12, The platinum nanoparticle-coated microparticles are platinum nanoparticle-coated microparticles having an effect as a battery catalyst.
発明１〜１２を展開してなされた本発明の第１４の実施の形態例及び発明（以下、発明１４という）は、発明１〜１２のいずれか１項に記載の白金ナノ粒子被覆微粒子において、前記白金ナノ粒子被覆微粒子が自動車の排ガス用触媒としての効果を有することを特徴とする白金ナノ粒子被覆微粒子である。 The fourteenth embodiment of the present invention and the invention (hereinafter referred to as invention 14) made by developing the inventions 1 to 12 are the platinum nanoparticle-coated fine particles according to any one of the inventions 1 to 12, The platinum nanoparticle-coated microparticles are platinum nanoparticle-coated microparticles having an effect as a catalyst for automobile exhaust gas.
課題を解決するためになされた本発明の第１５の実施の形態例及び発明（以下、発明１５という）は、白金及び／又はパラジウム以外の微粒子を中心にして、その周囲に白金ナノ粒子を担持させて作製する白金ナノ粒子被覆微粒子の製造方法において、前記白金ナノ粒子被覆微粒子を構成する白金ナノ粒子の還元に、第１の白金前駆体を第１の還元剤によって還元して前記白金及び／又はパラジウム以外の微粒子の表面に形成した第１の白金ナノ粒子層を形成する工程と、前記第１の白金ナノ粒子層を形成した後、第２の白金前駆体を第１の還元剤とは還元作用の異なる第２の還元剤によって還元して前記白金及び／又はパラジウム以外の微粒子の表面に形成した第２の白金ナノ粒子層を形成する工程とを少なくとも有することを特徴とする白金ナノ粒子被覆微粒子の製造方法である。 The fifteenth embodiment and invention (hereinafter referred to as invention 15) of the present invention made to solve the problems are centered on fine particles other than platinum and / or palladium and carry platinum nanoparticles around them. In the method for producing platinum nanoparticle-coated microparticles produced by the above process, the platinum nanoparticle constituting the platinum nanoparticle-coated microparticles is reduced by reducing the first platinum precursor with a first reducing agent and reducing the platinum and / or Alternatively, a step of forming a first platinum nanoparticle layer formed on the surface of fine particles other than palladium, and after forming the first platinum nanoparticle layer, the second platinum precursor is the first reducing agent. And a step of forming a second platinum nanoparticle layer formed on the surface of the fine particles other than platinum and / or palladium by reducing with a second reducing agent having a different reducing action. It is a manufacturing method of gold nanoparticles coated microparticles.
課題を解決するためになされた本発明の第１６の実施の形態例及び発明（以下、発明１６という）は、白金及び／又はパラジウム以外の微粒子を中心にして、その周囲に白金ナノ粒子を担持させて作製した白金ナノ粒子被覆微粒子の製造方法において、前記白金ナノ粒子被覆微粒子を構成する白金ナノ粒子が、第１の白金前駆体を第１の還元剤によって還元して前記白金及び／又はパラジウム以外の微粒子の表面に核を形成した第１の白金ナノ粒子層を形成する工程と、前記第１の白金ナノ粒子層を形成した後、第２の白金前駆体を第１の還元剤とは還元作用の異なる第２の還元剤によって還元して前記白金及び／又はパラジウム以外の微粒子の表面に白金を被覆状態にする工程とを少なくとも有することを特徴とする白金ナノ粒子被覆微粒子である。 The sixteenth embodiment and the invention (hereinafter referred to as invention 16) of the present invention made to solve the problems are centered on fine particles other than platinum and / or palladium, and platinum nanoparticles are supported around the fine particles. In the method for producing platinum nanoparticle-coated fine particles produced by the above process, the platinum nanoparticles constituting the platinum nanoparticle-coated fine particles are obtained by reducing the first platinum precursor with a first reducing agent and thereby the platinum and / or palladium. A step of forming a first platinum nanoparticle layer in which nuclei are formed on the surface of fine particles other than the above, and after forming the first platinum nanoparticle layer, the second platinum precursor is the first reducing agent. A platinum nanoparticle-coated fine particle comprising at least a step of reducing the surface of the fine particle other than platinum and / or palladium to a platinum-coated state by a second reducing agent having a different reducing action. It is.
発明１５または１６を展開してなされた本発明の第１７の実施の形態例及び発明（以下、発明１７という）は、発明１５または１６に記載の白金ナノ粒子被覆微粒子の製造方法において、前記第１の白金前駆体と第２の白金前駆体に同一種類の前駆体を用いることを特徴とする白金ナノ粒子被覆微粒子の製造方法である。 The seventeenth embodiment of the present invention and the invention (hereinafter referred to as invention 17) made by developing the invention 15 or 16 include the platinum nanoparticle-coated microparticle production method according to the invention 15 or 16, wherein A method for producing platinum nanoparticle-coated fine particles, wherein the same kind of precursor is used for one platinum precursor and the second platinum precursor.
発明１５〜１７を展開してなされた本発明の第１８の実施の形態例及び発明（以下、発明１４という）は、発明１５〜１７のいずれか１項に記載の白金ナノ粒子被覆微粒子の製造方法において、前記白金及び／又はパラジウム以外の微粒子の表面が分散剤によって覆われており、その表面に白金ナノ粒子が被覆されていることを特徴とする白金ナノ粒子被覆微粒子の製造方法である。 The eighteenth embodiment of the present invention and the invention (hereinafter referred to as invention 14) made by developing the inventions 15 to 17 are the production of platinum nanoparticle-coated fine particles according to any one of the inventions 15 to 17. In the method, the surface of fine particles other than platinum and / or palladium is covered with a dispersing agent, and the surface is coated with platinum nanoparticles.
発明１５〜１８を展開してなされた本発明の第１９の実施の形態例及び発明（以下、発明１９という）は、発明１５〜１８のいずれか１項に記載の白金ナノ粒子被覆微粒子の製造方法において、前記第１と第２の還元剤に、前記第２の還元剤の標準電極電位より前記第１の還元剤の標準電極電位がその絶対値において大きい値を示す還元剤を用いることを特徴とする白金ナノ粒子被覆微粒子の製造方法である。 The nineteenth embodiment of the present invention and the invention (hereinafter referred to as invention 19) made by developing the inventions 15 to 18 are the production of platinum nanoparticle-coated fine particles according to any one of the inventions 15 to 18. In the method, a reducing agent having a standard electrode potential of the first reducing agent that is larger in absolute value than a standard electrode potential of the second reducing agent is used as the first and second reducing agents. This is a method for producing platinum nanoparticle-coated fine particles.
発明１５〜１９を展開してなされた本発明の第２０の実施の形態例及び発明（以下、発明２０という）は、発明１５〜１９のいずれか１項に記載の白金ナノ粒子被覆微粒子の製造方法において、前記第１の還元剤に水素化ホウ素ナトリウムを用い、前記第２の還元剤にヒドラジンを用いることを特徴とする白金ナノ粒子被覆微粒子の製造方法である。 The twentieth embodiment of the present invention and the invention (hereinafter referred to as invention 20) made by developing the inventions 15 to 19 are the production of platinum nanoparticle-coated fine particles according to any one of the inventions 15 to 19. In the method, a platinum nanoparticle-coated fine particle production method is characterized in that sodium borohydride is used as the first reducing agent and hydrazine is used as the second reducing agent.
本発明の白金被覆微粒子を自動車の排ガス浄化用触媒や電池用触媒などに用いることにより、白金の量を減じない場合の触媒効果と遜色のない効果を発揮することができ、自動車や電池などの価格を大幅に低減することができるという産業上多大な効果を発揮する。 By using the platinum-coated fine particles of the present invention as an exhaust gas purification catalyst for automobiles, a catalyst for batteries, etc., it is possible to exhibit an effect comparable to that of a catalyst when the amount of platinum is not reduced, such as automobiles and batteries. It has a great industrial effect that the price can be greatly reduced.
１，６：微粒子
１ａ，６ａ：白金を担持した微粒子
２：微粒子が重なって撮影された微粒子
３，７：第１段目の還元処理で微粒子に担持された白金ナノ粒子
４ａ，６ｂ：本発明の白金ナノ粒子で被覆された微粒子
５，８：第１，２段目の還元処理を通して微粒子に担持された白金ナノ粒子層
DESCRIPTION OF SYMBOLS 1,6: Fine particle 1a, 6a: Fine particle carrying platinum 2: Fine particle taken by superposing fine particles 3, 7: Platinum nanoparticle 4a, 6b carried on fine particle by first-stage reduction treatment: the present invention Particles 5 and 8 coated with platinum nanoparticles of platinum: platinum nanoparticle layers supported on the particles through the first and second stage reduction treatments
以下、本発明の実施の形態例について説明する。なお、説明の重複を避けるため、白金被覆微粒子の製造方法としての説明で白金被覆微粒子の説明を兼ねることもあり、その逆の場合もある。以下に、本発明の実施の形態例について説明する。 Hereinafter, embodiments of the present invention will be described. In addition, in order to avoid duplication of explanation, explanation as a method for producing platinum-coated fine particles may also serve as explanation of platinum-coated fine particles, and vice versa. Hereinafter, embodiments of the present invention will be described.
本発明者らは白金の使用量を減らす試みとして、白金ナノ粒子を白金よりも十分にコストの安い微粒子に被覆して、白金ナノ粒子の表面が大きいことによる性質を維持させたうえで、その触媒作用を発揮させようと試み、種々の実験を行った。 In an attempt to reduce the amount of platinum used, the present inventors coated platinum nanoparticles with fine particles that are sufficiently cheaper than platinum, and maintained the properties due to the large surface of the platinum nanoparticles. Various experiments were conducted in an attempt to exert the catalytic action.
しかし、前記のように、白金前駆体を単一の還元剤で還元処理をすることでは、金属酸化物微粒子の表面にまばらにきり白金ナノ粒子を担持させることができず、被覆レベルまで担持させることは困難であるとの結論に達した。 However, as described above, when the platinum precursor is reduced with a single reducing agent, platinum nanoparticles cannot be sparsely supported on the surface of the metal oxide fine particles but are supported up to the coating level. I came to the conclusion that it was difficult.
ここで、単一の還元剤とは、前記白金前駆体の１回の還元処理に用いる還元剤全体のことを示し、Ａ、Ｂを還元剤名とすると、その還元処理に、還元剤Ａだけを用いる場合と、還元剤Ｂだけを用いる場合と、還元剤Ａと還元剤Ｂを適切に混合して用いる場合のいずれの場合も、前記１回の還元処理に同時に用いる限りその還元剤を単一の還元剤ということにする。 Here, the single reducing agent indicates the whole reducing agent used for one reduction treatment of the platinum precursor, and when A and B are the names of the reducing agents, only the reducing agent A is included in the reduction treatment. In the case of using the reducing agent B, the case of using only the reducing agent B, and the case of using the reducing agent A and the reducing agent B in an appropriate mixture, the reducing agent is simply used as long as it is used simultaneously in the one reduction treatment. Let's call it one reducing agent.
還元剤としては、ＮａＢＨ4（水素化ホウ素ナトリウム）、ＮＨ2ＮＨ2・Ｈ2Ｏ（ヒドラジン１水和物）、次亜リン酸塩（ＮａＨ2ＰＯ2）、ジメチルアミンボラン（（ＣＨ3）２ＮＨＢＨ3）、ホルムアルデヒド、アルコールなど、多くの還元剤を用いることができる。 As the reducing agent, NaBH 4 (sodium borohydride), NH 2 NH 2 .H 2 O (hydrazine monohydrate), hypophosphite (NaH 2 PO 2 ), dimethylamine borane ((CH 3 )) Many reducing agents such as 2NHBH 3 ), formaldehyde, alcohol, etc. can be used.
溶液中における微粒子の金属被覆において重要なのは還元速度の制御であり、還元速度によって平滑な、または意図的に凹凸のある金属表面を形成させることができる。還元速度に大きな影響を与える因子として、還元剤、温度、ｐＨで定まる熱力学的因子と、撹拌速度や金属−還元剤−被被覆表面との相性が影響する速度論的因子がある。たとえば、本特許の実施例１，２で還元剤として使用している水素化ホウ素ナトリウムとヒドラジンの標準電極電位は、水素化ホウ素ナトリウムのＢ（ＯＨ）3＋７Ｈ+（＋８ｅ）と（ＢＨ4）＋３Ｈ2Ｏの間の反応における−０．４８１ボルトであり、ヒドラジンの標準電極電位は−０．２３ボルトである。この場合、ヒドラジンよりも水素化ホウ素ナトリウムの方が還元力が強い還元剤であるということができる。 What is important in the metal coating of fine particles in a solution is the control of the reduction rate, and a smooth or intentionally uneven metal surface can be formed by the reduction rate. Factors that greatly affect the reduction rate include a thermodynamic factor determined by the reducing agent, temperature, and pH, and a kinetic factor that is affected by the agitation speed and the compatibility of the metal-reducing agent-coated surface. For example, the standard electrode potentials of sodium borohydride and hydrazine used as reducing agents in Examples 1 and 2 of this patent are B (OH) 3 + 7H + (+ 8e) and (BH 4 ) of sodium borohydride. + 3H 2 O is -0.481 volts in the reaction between the standard electrode potential of hydrazine is -0.23 volts. In this case, it can be said that sodium borohydride is a reducing agent having a stronger reducing power than hydrazine.
本発明者らは、還元剤の種類をはじめとする還元速度に影響を与える因子を検討し、担体微粒子の表面に白金、パラジウムをはじめとする貴金属微粒子で被覆できないか調べた。 The present inventors examined factors affecting the reduction rate including the type of reducing agent, and investigated whether the surface of the carrier fine particles could be coated with noble metal fine particles such as platinum and palladium.
そこで、本発明者らは、白金前駆体の還元を、従来行われていなかった還元作用の異なる還元剤を用いて、複数段階で行うことの検討を行い実施した結果、良好な状態に白金で被覆した白金ナノ粒子被覆金属酸化物微粒子を得ることができることを見いだした。以下、その実施の形態例を具体的に説明する。 Therefore, the present inventors have conducted a study of performing the reduction of the platinum precursor in a plurality of steps using a reducing agent having a different reducing action, which has not been conventionally performed. It has been found that coated platinum nanoparticle-coated metal oxide fine particles can be obtained. The embodiment will be specifically described below.
本発明者らは、その一例として、還元力の強いことで知られている水素化ホウ素ナトリウム（ＮａＢＨ4）水溶液を還元剤に用いて、ＳｉＯ2微粒子、ａ−ＴｉＯ2（アモルファス状の二酸化チタン）、結晶性の二酸化チタン、二酸化スズなどの微粒子の周囲に白金ナノ粒子を膜状に付けて担持させ、触媒作用等を発揮させようと試みる実験を行った。 As an example, the present inventors used an aqueous solution of sodium borohydride (NaBH 4 ), which is known to have a strong reducing power, as a reducing agent to form SiO 2 fine particles, a-TiO 2 (amorphous titanium dioxide). ), An experiment was carried out in which platinum nanoparticles were attached in the form of a film around fine particles of crystalline titanium dioxide, tin dioxide, etc. to exert catalytic action and the like.
実施例１として、ＳｉＯ2微粒子を作製し、その表面に分散剤を吸着させ、その上に白金を被覆する試みを行った。 As Example 1, an attempt was made to produce SiO 2 fine particles, adsorb a dispersant on the surface thereof, and coat platinum thereon.
１００ｍｌの三角フラスコに、テトラエトキシシランＴＥＯＳ（関東化学株式会社製、特級試薬 純度、９５．０％）を２．３５８ｍｌ（ミリリットル）、エタノール（関東化学株式会社製、特級試薬、９９．５％）を２５．１４２ｍｌ添加した。 Into a 100 ml Erlenmeyer flask, 2.358 ml (milliliter) of tetraethoxysilane TEOS (manufactured by Kanto Chemical Co., Ltd., special grade reagent purity, 95.0%), ethanol (manufactured by Kanto Chemical Co., Ltd., special grade reagent, 99.5%) 25.142 ml was added.
そこへ、室温（２５°Ｃ）で、攪拌しながらイオン交換水２２ｍｌを加え、続けて１Ｍ（１ｍｏｌ／Ｌ）水酸化ナトリウム（関東化学株式会社製，特級試薬）水溶液０．５ｍｌを添加した。それを、３５°Ｃに加温し、２４時間攪拌を続けた。ＴＥＯＳの最終濃度は０．２Ｍになった。 Thereto, 22 ml of ion-exchanged water was added at room temperature (25 ° C.) while stirring, and 0.5 ml of 1M (1 mol / L) sodium hydroxide (manufactured by Kanto Chemical Co., Ltd., special grade reagent) aqueous solution was subsequently added. It was warmed to 35 ° C. and stirred for 24 hours. The final TEOS concentration was 0.2M.
得られたＳｉＯ2コロイド液から遠心操作により下地としてのＳｉＯ２粒子を取り出した（１５０００ｒｐｍ×３０ｍｉｎ×２回）（トミー精工株式会社製、高速冷却遠心機Ｓｕｐｒｅｍａ２５、ローター番号ＮＡ−７）。沈降しているＳｉＯ2粒子に、イオン交換水５０ｍｌを加え、再分散させ、ＳｉＯ2水分散コロイド液５０ｍｌを得た。その透過型電子顕微鏡（以下、ＴＥＭという）写真を図１に，動的散乱によって測定した粒度分布を図２に示す。符号１はＳｉＯ2微粒子、２は前記微粒子が重なって撮影された微粒子を示す。粒子径分布のピーク値は９１．２８ｎｍで、大半は、５０ｎｍ〜１５０ｎｍに分布している。 From the resulting SiO 2 colloidal solution, SiO2 particles as a base were taken out by centrifugation (15000 rpm × 30 min × 2 times) (manufactured by Tommy Seiko Co., Ltd., high-speed cooling centrifuge Suprema 25, rotor number NA-7). To the precipitated SiO 2 particles, 50 ml of ion-exchanged water was added and redispersed to obtain 50 ml of a SiO 2 water-dispersed colloidal solution. A photograph of the transmission electron microscope (hereinafter referred to as TEM) is shown in FIG. 1, and the particle size distribution measured by dynamic scattering is shown in FIG. Reference numeral 1 denotes SiO 2 fine particles, and 2 denotes fine particles photographed by overlapping the fine particles. The peak value of the particle size distribution is 91.28 nm, and most are distributed in the range of 50 nm to 150 nm.
このＳｉＯ2水分散コロイド液５０ｍｌを２００ｍｌ三角フラスコに移し、攪拌下、２ｇ／ＬのＰＶＰ（関東化学株式会社製、分子量３６００００）水溶液を５０ｍｌ添加し、３５°Ｃで２４時間攪拌した（攪拌速度５００ｒｐｍ）。この液を遠心操作（１５０００×３０ｍｉｎ×２回）して粒子を取り出し、イオン交換水１００ｍｌを加えることにより、ＰＶＰで表面処理したＳｉＯ2コロイド液（ＰＶＰ／ＳｉＯ2コロイド液）１００ｍｌを得た。 50 ml of this SiO 2 aqueous dispersion colloidal solution was transferred to a 200 ml Erlenmeyer flask, 50 ml of 2 g / L PVP (Kanto Chemical Co., Ltd., molecular weight 360000) aqueous solution was added with stirring, and the mixture was stirred at 35 ° C. for 24 hours (stirring speed). 500 rpm). The liquid was centrifuged (15000 × 30 min × 2 times) to take out the particles, and 100 ml of ion exchange water was added to obtain 100 ml of a SiO 2 colloid liquid (PVP / SiO 2 colloid liquid) surface-treated with PVP.
このＰＶＰ／ＳｉＯ2コロイド液２５ｍｌを、１００ｍｌ三角フラスコに取り分け、そこへイオン交換水１４．２９５ｍｌを添加して希釈した。次に、攪拌下、０．１Ｍのクエン酸水溶液４．１４５ｍｌ、１９．３ｍＭの塩化白金酸（Ｈ2ＰｔＣｌ6）（関東化学株式会社製、純度 ９８．５％）水溶液４．１４５ｍｌを添加した。更に、０．１ＭのＮａＯＨ水溶液を、液のｐＨが６．８になるまで添加した（０．１ＭのＮａＯＨ水溶液の添加量は約４．６ｍｌ）。 25 ml of this PVP / SiO 2 colloidal solution was placed in a 100 ml Erlenmeyer flask and diluted with 14.295 ml of ion-exchanged water. Next, 4.145 ml of 0.1 M citric acid aqueous solution and 4.145 ml of 19.3 mM chloroplatinic acid (H 2 PtCl 6 ) (manufactured by Kanto Chemical Co., Inc., purity 98.5%) were added with stirring. . Further, 0.1M NaOH aqueous solution was added until the pH of the solution reached 6.8 (the amount of 0.1M NaOH aqueous solution added was about 4.6 ml).
この液の温度を３５°Ｃに調整し、０．１ＭのＮａＢＨ4水溶液を０．９６０ｍｌを添加し、１５分間攪拌しながら塩化白金酸の第１段目の還元を行った。 The temperature of this solution was adjusted to 35 ° C., 0.960 ml of a 0.1 M NaBH 4 aqueous solution was added, and the first stage reduction of chloroplatinic acid was performed with stirring for 15 minutes.
この液を遠心操作（１５０００ｒｐｍ×３０ｍｉｎ×２回）し、粒子を取り出し、イオン交換水５０ｍｌを加えることにより、白金ナノ粒子を担持したＳｉＯ2コロイド液（Ｐｔ／ＳｉＯ2コロイド液）５０ｍｌを得た。 This liquid was centrifuged (15000 rpm × 30 min × 2 times), the particles were taken out, and 50 ml of ion exchange water was added to obtain 50 ml of a SiO 2 colloid liquid (Pt / SiO 2 colloid liquid) carrying platinum nanoparticles. .
図３に第１段目の還元で白金ナノ粒子を担持したＰｔ／ＳｉＯ2微粒子のＴＥＭ写真を、図４にその拡大して撮影したＴＥＭ写真を、図５にその粒度分布を示す。符号１ａは白金を担持した微粒子、３は前記微粒子に担持された白金ナノ粒子を示す。粒子径のピークは１０５．７ｎｍであった。図４から明らかなように、図４の微粒子は下地を白金で被覆した状態というにはほど遠い状態といえ、白金ナノ粒子は、ＳｉＯ2微粒子の表面の２０〜３０％覆っているかどうかというところである。 FIG. 3 shows a TEM photograph of Pt / SiO 2 fine particles carrying platinum nanoparticles in the first stage reduction, FIG. 4 shows an enlarged TEM photograph, and FIG. 5 shows the particle size distribution. Reference numeral 1 a represents fine particles carrying platinum, and 3 represents platinum nanoparticles carried by the fine particles. The peak of the particle diameter was 105.7 nm. As is clear from FIG. 4, the fine particles in FIG. 4 are far from being covered with platinum, and the platinum nanoparticles cover 20 to 30% of the surface of the SiO 2 fine particles. .
本発明者の観察結果の確認のため、前記で得られたＰｔ／ＳｉＯ2コロイド液０．５ｍｌを１０ｍｌの試験管に取り分け、イオン交換水を２．０ｍｌ添加して希釈した。その溶液を３５°Ｃに調整し、攪拌下、１．６ｍＭの塩化白金酸（Ｈ2ＰｔＣｌ6）水溶液を２．４９５ｍｌ加え、１時間攪拌した。その溶液を、前記と同様にして、ＮａＢＨ4による還元を続けた。 In order to confirm the observation results of the present inventors, 0.5 ml of the Pt / SiO 2 colloidal solution obtained above was placed in a 10 ml test tube and diluted by adding 2.0 ml of ion exchange water. The solution was adjusted to 35 ° C., and 2.495 ml of 1.6 mM chloroplatinic acid (H 2 PtCl 6 ) aqueous solution was added with stirring, followed by stirring for 1 hour. The solution was continued to be reduced with NaBH 4 as before.
この液を遠心操作（１５０００ｒｐｍ×３０ｍｉｎ×２回）し、粒子を取り出したがＳｉＯ2微粒子表面への白金担持状態は、後記のような白金により被覆されたというにはほど遠い状態であった。 This liquid was centrifuged (15000 rpm × 30 min × 2 times) to take out the particles, but the platinum-supported state on the surface of the SiO 2 fine particles was far from being covered with platinum as described later.
そこで本発明者は還元の条件を種々検討した結果、還元剤を変えて還元することによりＰｔ−ｃｏａｔｅｄ状態のＳｉＯ2コロイド液の作製が可能であることを見出した。その実施の形態例を以下に説明する。 Therefore, as a result of various investigations on the reduction conditions, the present inventor has found that it is possible to produce a Pt-coated SiO 2 colloidal solution by reducing the reducing agent. The embodiment will be described below.
図３と図４を用いて説明した前記Ｐｔ／ＳｉＯ2コロイド液から０．５ｍｌを１０ｍｌの試験管に取り出し、イオン交換水を２．０ｍｌ添加して希釈した。その溶液を５°Ｃに冷却し、攪拌下、１．６ｍＭの塩化白金酸（Ｈ2ＰｔＣｌ6）水溶液を２．４９５ｍｌ加え、１時間攪拌した。そこへ、ＮＨ2ＮＨ2・Ｈ2Ｏ（関東化学株式会社製、鹿特級試薬、９８．０％）を０．００５ｍｌ添加し、５°Ｃで２４時間攪拌し、本発明の第２段目の還元を行った。 From the Pt / SiO 2 colloidal solution described with reference to FIGS. 3 and 4, 0.5 ml was taken out into a 10 ml test tube, and diluted with 2.0 ml of ion-exchanged water. The solution was cooled to 5 ° C., and 2.495 ml of 1.6 mM chloroplatinic acid (H 2 PtCl 6 ) aqueous solution was added with stirring, followed by stirring for 1 hour. Thereto, 0.005 ml of NH 2 NH 2 .H 2 O (manufactured by Kanto Chemical Co., Inc., deer special grade reagent, 98.0%) was added and stirred at 5 ° C. for 24 hours. Second stage of the present invention Reduced.
この液を遠心操作（１５０００ｒｐｍ×３０ｍｉｎ×２回）し、粒子を取り出し、イオン交換水５ｍｌを加えることにより、Ｐｔで被覆されたＳｉＯ2コロイド液（白金被覆ＳｉＯ2コロイド液）を得ることができた。 This solution is centrifuged (15000 rpm x 30 min x 2 times), the particles are taken out, and 5 ml of ion-exchanged water is added to obtain a Pt-coated SiO 2 colloid solution (platinum-coated SiO 2 colloid solution). It was.
図６にそのＴＥＭ写真を、図７にその拡大して撮影したＴＥＭ写真を、図８にその粒度分布を示す。符号４ａは本発明の白金ナノ粒子で被覆されたＳｉＯ2微粒子、５は第１，２段目の還元処理を通して前記ＳｉＯ2微粒子に被覆した白金ナノ粒子層を示す。図からも確認できるように、直径がおおむね１００ｎｍのＳｉＯ2微粒子の表面の少なくとも５０％以上を白金ナノ粒子で覆われたＳｉＯ2微粒子が大半を占めているのがみられる。多くのＳｉＯ2微粒子は、その微粒子表面の７０％以上が白金ナノ粒子に覆われているのが分かる。 FIG. 6 shows the TEM photograph, FIG. 7 shows the enlarged TEM photograph, and FIG. 8 shows the particle size distribution. Reference numeral 4a denotes a SiO 2 fine particle coated with the platinum nanoparticles of the present invention, and 5 denotes a platinum nano particle layer coated on the SiO 2 fine particles through the first and second stage reduction treatments. As it can be seen from the figure, seen that SiO 2 particles at least 50% or more covered with platinum nanoparticles on the surface of the SiO 2 fine particles generally have a diameter 100nm is dominated. It can be seen that in many SiO 2 fine particles, 70% or more of the fine particle surface is covered with platinum nanoparticles.
次に、実施例２について説明する。本発明者らは、下地となる金属酸化物微粒子を種々変えて白金ナノ粒子で被覆する実験を行い、上記と同様にして白金被覆微粒子の作製ができることを確かめた。 Next, Example 2 will be described. The present inventors conducted experiments in which the metal oxide fine particles serving as the base were variously changed and coated with platinum nanoparticles, and confirmed that platinum coated fine particles could be produced in the same manner as described above.
実施例２としての下地としてのＴｉＯ2微粒子を作製し、その表面に分散剤をつけ、その上に白金で被覆することを説明する。 The production of TiO 2 fine particles as a base as Example 2 and the addition of a dispersing agent on the surface and covering with platinum will be described.
１００ｍｌの三角フラスコに、チタニウム テトライソプロポキシド（ＴＴＩＰ）（関東化学株式会社製、Ｏｒｇａｎｉｃｓ純度９７．０％）を０．４５８ｍｌ、２−プロパノール（関東化学株式会社製、特級薬品、９９．７％）を７．８８ｍｌ添加した。 In a 100 ml Erlenmeyer flask, 0.458 ml of titanium tetraisopropoxide (TTIP) (manufactured by Kanto Chemical Co., Inc., Organics purity 97.0%), 2-propanol (manufactured by Kanto Chemical Co., Ltd., special grade chemical, 99.7%) ) Was added in an amount of 7.88 ml.
そこへ、別の１００ｍｌ三角フラスコに調製した、メチルアミン（ＣＨ3ＮＨ2）（関東化学株式会社製、３８．０−４２．０％）０．０２２ｍｌ、イオン交換水０．２５７ｍｌ、アセトニトリル（ＣＨ3ＣＮ）（関東化学株式会社製、特級薬品、９９．５％）２０．６９ｍｌ、２−プロパノール２０．６９ｍｌの溶液を、室温（２５°Ｃ）で、攪拌しながら加えた。液を３０°Ｃに加温し、２時間攪拌を続けた。ＴＴＩＰの最終濃度は０．０３Ｍになる。 Thereto, 0.022 ml of methylamine (CH 3 NH 2 ) (manufactured by Kanto Chemical Co., Ltd., 38.0-42.0%), 0.257 ml of ion-exchanged water, acetonitrile (CH 2 ) prepared in another 100 ml Erlenmeyer flask 3 CN) (manufactured by Kanto Chemical Co., Ltd., special grade chemical, 99.5%) A solution of 20.69 ml and 2-propanol 20.69 ml was added with stirring at room temperature (25 ° C.). The solution was warmed to 30 ° C. and stirring was continued for 2 hours. The final concentration of TTIP is 0.03M.
得られたアモルファス状ＴｉＯ2（ａ−ＴｉＯ2）コロイド液５０ｍｌから、遠心操作により粒子を取り出した（１５０００ｒｐｍ×３０ｍｉｎ×２回）。沈降しているａ−ＴｉＯ2粒子に、イオン交換水５０ｍｌを加え、再分散し、ａ−ＴｉＯ2水分散コロイド液を得た。 From 50 ml of the obtained amorphous TiO 2 (a-TiO 2 ) colloidal solution, particles were taken out by centrifugation (15000 rpm × 30 min × 2 times). To the precipitated a-TiO 2 particles, 50 ml of ion-exchanged water was added and redispersed to obtain an a-TiO 2 aqueous dispersion colloidal solution.
図９にそのＴＥＭ写真を、図１０にそのＵＶ−ＶＩＳデータを示す。符号６はＴｉＯ2微粒子である。粒子径はおよそ２００ｎｍである。図１０の紫外線部分にＴｉＯ2の吸光特性が見られる。 FIG. 9 shows the TEM photograph, and FIG. 10 shows the UV-VIS data. Reference numeral 6 denotes TiO 2 fine particles. The particle size is approximately 200 nm. The absorption characteristic of TiO 2 can be seen in the ultraviolet part of FIG.
このａ−ＴｉＯ2水分散コロイド液５０ｍｌを２００ｍｌ三角フラスコに移し、そこへ０．３ｇ／ＬのＰＤＡＭＡＣ（ポリジアリルジメチルアンモニウムクロライド）（Ｓｉｇｍａ−Ａｌｄｒｉｃｈ社製、純度２０ｗｔ％、平均分子量１００，０００−２００，０００）水溶液５０ｍｌを添加し、３５°Ｃで２４時間攪拌した（攪拌速度５００ｒｐｍ）。 50 ml of this a-TiO 2 aqueous dispersion colloid liquid was transferred to a 200 ml Erlenmeyer flask, and 0.3 g / L of PDAMAC (polydiallyldimethylammonium chloride) (manufactured by Sigma-Aldrich, purity 20 wt%, average molecular weight 100,000- 200,000) aqueous solution was added and stirred at 35 ° C. for 24 hours (stirring speed 500 rpm).
この液を遠心操作（１５０００ｒｐｍ×３０ｍｉｎ×２回）し、粒子を取り出し、イオン交換水１００ｍｌを加えることにより、ＰＤＡＭＡＣで修飾されたａ−ＴｉＯ2コロイド液（ＰＤＡＭＡＣ／ａ−ＴｉＯ2コロイド液）１００ｍｌを得た。 This liquid is centrifuged (15000 rpm × 30 min × 2 times), the particles are taken out, and 100 ml of ion-exchanged water is added to thereby add 100 ml of a-TiO 2 colloid liquid (PDAMAC / a-TiO 2 colloid liquid) modified with PDAMAC. Got.
上記ＰＤＡＭＡＣ／ａ−ＴｉＯ2コロイド液２５ｍｌを、１００ｍｌ三角フラスコに取り分け、そこへイオン交換水１４．２９５ｍｌを添加した。次に、攪拌下、０．１Ｍのクエン酸水溶液１．０ｍｌ、１９．３ｍＭの塩化白金酸（Ｈ2ＰｔＣｌ6）（関東化学株式会社製，純度９８．５％）水溶液４．１４５ｍｌを順次添加した。そこへ、０．１ＭのＮａＯＨ水溶液を、液のｐＨが６．８になるまで添加した（０．１ＭのＮａＯＨ水溶液添加量 約４．６ｍｌ）。さらに、 液の温度を３５°Ｃに調整し、０．１ＭのＮａＢＨ4（関東化学株式会社製、９２．０％）水溶液を０．９６０ｍｌ添加し、１５分間攪拌し、塩化白金酸の第１段目の還元を行った。 25 ml of the PDAMAC / a-TiO 2 colloidal solution was placed in a 100 ml Erlenmeyer flask, and 14.295 ml of ion-exchanged water was added thereto. Next, under stirring, 1.0 ml of 0.1 M citric acid aqueous solution and 4.145 ml of 19.3 mM chloroplatinic acid (H 2 PtCl 6 ) (manufactured by Kanto Chemical Co., Inc., purity: 98.5%) aqueous solution were sequentially added. did. Thereto was added a 0.1M NaOH aqueous solution until the pH of the solution reached 6.8 (addition amount of 0.1M NaOH aqueous solution about 4.6 ml). Further, the temperature of the liquid was adjusted to 35 ° C., 0.960 ml of a 0.1 M NaBH 4 (Kanto Chemical Co., Ltd., 92.0%) aqueous solution was added, and the mixture was stirred for 15 minutes. The stage reduction was performed.
この液を遠心操作（１５０００ｒｐｍ×３０ｍｉｎ×２回）することにより粒子を取り出し、イオン交換水５０ｍｌを加え、Ｐｔナノ粒子が担持されたａ−ＴｉＯ2コロイド液（Ｐｔ／ａ−ＴｉＯ2コロイド液）５０ｍｌを得た。 This liquid is centrifuged (15000 rpm × 30 min × 2 times) to take out the particles, add 50 ml of ion-exchanged water, and a-TiO 2 colloid liquid carrying Pt nanoparticles (Pt / a-TiO 2 colloid liquid) 50 ml was obtained.
図１１にそのＴＥＭ写真を、図１２にその拡大して撮影したＴＥＭ写真を、図１３に動的散乱による粒子径分布図を示す。符号６ａは白金を担持したＴｉＯ2微粒子、７は微粒子６ａに担持された白金ナノ粒子を示す。図１３から、白金を担持したａ−ＴｉＯ2の微粒子の粒子径は、２９５．３ｎｍを中心に分布している。図１２から、ａ−ＴｉＯ2微粒子の表面に白金がまばらに担持されているが、ａ−ＴｉＯ2微粒子表面を十分に覆ってはいない。白金ナノ粒子の粒子径は、ＸＲＤ測定の結果１０．６ｎｍであった。 FIG. 11 shows a TEM photograph, FIG. 12 shows an enlarged TEM photograph, and FIG. 13 shows a particle size distribution diagram by dynamic scattering. Reference numeral 6a denotes a TiO 2 fine particle carrying platinum, and 7 denotes a platinum nanoparticle carried on the fine particle 6a. From FIG. 13, the particle diameter of the fine particles of a-TiO 2 supporting platinum is distributed around 295.3 nm. From FIG. 12, platinum is sparsely supported on the surface of the a-TiO 2 fine particles, but the surface of the a-TiO 2 fine particles is not sufficiently covered. The particle diameter of the platinum nanoparticles was 10.6 nm as a result of XRD measurement.
本発明者の観察結果の確認のため、、上記で得られたＰｔ／ａ−ＴｉＯ2コロイド液０．２５ｍｌを１０ｍｌの試験管に取り分け、イオン交換水を添加して希釈した。次に、攪拌下、０．１Ｍのクエン酸水溶液、１９．３ｍＭの塩化白金酸（Ｈ2ＰｔＣｌ6）（関東化学株式会社製，純度９８．５％）水溶液を順次添加した。そこへ、０．１ＭのＮａＯＨ水溶液を、液のｐＨが６．８になるまで添加した。さらに、 液の温度を３５°Ｃに調整し、０．１ＭのＮａＢＨ4（関東化学株式会社製、９２．０％）水溶液を添加し、１５分間攪拌した。 In order to confirm the observation results of the present inventors, 0.25 ml of the Pt / a-TiO 2 colloidal solution obtained above was placed in a 10 ml test tube and diluted by adding ion-exchanged water. Next, a 0.1 M citric acid aqueous solution and a 19.3 mM chloroplatinic acid (H 2 PtCl 6 ) (manufactured by Kanto Chemical Co., Inc., purity: 98.5%) aqueous solution were sequentially added with stirring. Thereto, a 0.1 M NaOH aqueous solution was added until the pH of the solution reached 6.8. Furthermore, the temperature of the liquid was adjusted to 35 ° C., a 0.1 M NaBH 4 (Kanto Chemical Co., Ltd., 92.0%) aqueous solution was added, and the mixture was stirred for 15 minutes.
この液を遠心操作（１５０００ｒｐｍ×３０ｍｉｎ×２回）し、粒子を取り出したがＴｉＯ2微粒子表面へのＰｔ担持状態は、後記のような白金により被覆されたＴｉＯ2微粒子というにはほど遠い状態であった。白金はＮａＢＨ4により還元されても多くはＴｉＯ2微粒子に担持されず、白金単独で凝集した状態になってしまうという結果になることがわかった。塩化白金酸の量を１０分の１に減らしたところ、やはり白金の担持量は塩化白金酸の量を１０分の１に減少させる前と同じであった。 This solution was centrifuged (15000rpm × 30min × 2 times), Pt-supported state of was removed particles into TiO 2 particles surface was in far from the rather TiO 2 particles coated with platinum as described below It was. It has been found that even if platinum is reduced by NaBH 4, most of the platinum is not supported on the TiO 2 fine particles, and is agglomerated by platinum alone. When the amount of chloroplatinic acid was reduced to 1/10, the amount of platinum supported was the same as before the amount of chloroplatinic acid was reduced to 1/10.
そこで本発明者らは還元の条件を種々検討した結果に基づき、還元剤を変えて還元することにより白金被覆状態のＴｉＯ2コロイド液の作製を試みた。 Therefore, the present inventors tried to produce a TiO 2 colloidal solution in a platinum coating state by changing the reducing agent based on the results of various investigations on the reduction conditions.
すなわち、最初に得られたＰｔ／ａ−ＴｉＯ2コロイド液０．２５ｍｌを１０ｍｌの試験官に取り出し、イオン交換水を２．２５ｍｌを添加して希釈した。その溶液を５°Ｃに冷却し、攪拌下、１．６ｍＭ塩化白金酸（Ｈ2ＰｔＣｌ6）水溶液を２．４９５ｍｌを加え、１時間攪拌した。そこへ、ヒドラジン１水和物（ＮＨ2ＮＨ2・Ｈ2Ｏ）（関東化学株式会社製，鹿特級試薬，９８．０％）を０．００５ｍｌ添加し、５°Ｃで２４時間攪拌し、本発明の第２段目の還元を行った。 That is, 0.25 ml of the initially obtained Pt / a-TiO 2 colloidal solution was taken out to a 10 ml examiner, and 2.25 ml of ion-exchanged water was added for dilution. The solution was cooled to 5 ° C, and 2.495 ml of 1.6 mM chloroplatinic acid (H 2 PtCl 6 ) aqueous solution was added with stirring, and the mixture was stirred for 1 hour. 0.005 ml of hydrazine monohydrate (NH 2 NH 2 .H 2 O) (manufactured by Kanto Chemical Co., Inc., deer grade reagent, 98.0%) was added thereto, and the mixture was stirred at 5 ° C. for 24 hours. The second stage reduction of the present invention was performed.
この液を遠心操作（１５０００ｒｐｍ×３０ｍｉｎ×２回）し、粒子を取り出し、イオン交換水５ｍｌを加えることにより、白金ナノ粒子で被覆されたａ−ＴｉＯ2コロイド液（Ｐｔ−ｃｏａｔｅｄ ＴｉＯ2コロイド液）５ｍｌを得た。 This solution is centrifuged (15000 rpm × 30 min × 2 times), the particles are taken out, and 5 ml of ion-exchanged water is added, thereby a-TiO 2 colloid solution coated with platinum nanoparticles (Pt-coated TiO 2 colloid solution). 5 ml was obtained.
図１４にそのＴＥＭ写真を、図１５にその拡大して撮影したＴＥＭ写真を示す。符号６ｂは本発明の白金ナノ粒子被覆ａ−ＴｉＯ2微粒子、８は本発明の第１，２段目の還元処理によってａ−ＴｉＯ2微粒子を被覆している白金ナノ粒子層である。図１５から直径がおおむね１００ｎｍのＴｉＯ2微粒子の表面の少なくとも５０％以上を白金ナノ粒子で覆われたＴｉＯ2微粒子が大半を占めているのがみられる。多くのＴｉＯ2微粒子は、その微粒子表面の７０％以上が白金ナノ粒子に覆われているのが分かる。図１６にＵＶ−ＶＩＳ測定データを示す。図１６の紫外線部分に図１０で現れたＴｉＯ2の吸光特性が見られないことから、ＴｉＯ2表面は表面に吸着された物質で覆われているということができる。 FIG. 14 shows the TEM photograph, and FIG. 15 shows the enlarged TEM photograph. Reference numeral 6b denotes a platinum nanoparticle-coated a-TiO 2 fine particle of the present invention, and 8 denotes a platinum nanoparticle layer coated with the a-TiO 2 fine particle by the first and second stage reduction treatments of the present invention. From FIG. 15, it can be seen that the majority of TiO 2 fine particles covered with platinum nanoparticles account for at least 50% of the surface of TiO 2 fine particles having a diameter of approximately 100 nm. It can be seen that in many TiO 2 fine particles, 70% or more of the fine particle surface is covered with platinum nanoparticles. FIG. 16 shows UV-VIS measurement data. Since the absorption characteristic of TiO 2 appearing in FIG. 10 is not seen in the ultraviolet part of FIG. 16, it can be said that the TiO 2 surface is covered with the substance adsorbed on the surface.
図１７はＰｔ−ｃｏａｔｅｄ ａ−ＴｉＯ2微粒子のＸＲＤ測定データで、結晶子サイズは１１．６ｎｍであった。 FIG. 17 shows XRD measurement data of Pt-coated a-TiO 2 fine particles, and the crystallite size was 11.6 nm.
このほかに、貴金属による被覆としてパラジウムでパラジウムや白金以外の微粒子の表面を被覆することも有効と期待されている。本発明者らは、前期実施例とは別に、パラジウムをパラジウムや白金以外の微粒子としてＳｉＯ2，ＴｉＯ2，炭素等を用い、前期白金ナノ粒子被覆の場合と同様に、複数の異なる還元剤を用いて、複数回すなわち複数段階の還元処理を重ねて行い、パラジウムを前期パラジウムや白金以外の微粒子の表面に膜状に担持させ、１種類の還元剤を用いて行った還元処理あるいは同じ還元処理の繰り返しを行って得られるパラジウムナノ粒子層ではとうてい得られない厚い膜状のパラジウムナノ粒子層を得ることができた。 In addition, it is expected to be effective to coat the surface of fine particles other than palladium or platinum with palladium as a noble metal coating. In addition to the previous examples, the inventors used SiO 2 , TiO 2 , carbon, etc. as fine particles other than palladium and platinum, and used a plurality of different reducing agents in the same manner as in the case of the platinum nanoparticle coating. Using multiple reduction steps, that is, performing a plurality of stages of reduction treatment, palladium is supported on the surface of fine particles other than palladium or platinum in the form of a film, or the same reduction treatment using one type of reducing agent. It was possible to obtain a thick film-like palladium nanoparticle layer that cannot be obtained with the palladium nanoparticle layer obtained by repeating the above steps.
さらに、本発明者らは、パラジウムや白金以外の微粒子の表面にパラジウムナノ粒子をつけ、その上に白金ナノ粒子を載せることができた。 Furthermore, the present inventors were able to attach palladium nanoparticles on the surface of fine particles other than palladium and platinum and place platinum nanoparticles thereon.
前期パラジウムや白金以外の微粒子の表面にパラジウムナノ粒子及び／又は白金ナノ粒子での被覆処理の過程に、置換めっきで少量のパラジウムナノ粒子及び／又は白金ナノ粒子を乗せることも有効であることが分かった。 It is also effective to place a small amount of palladium nanoparticles and / or platinum nanoparticles on the surface of fine particles other than palladium or platinum in the process of coating with palladium nanoparticles and / or platinum nanoparticles by displacement plating. I understood.
前記白金以外の微粒子としては、金属酸化物の微粒子、炭素微粒子等があげられ、微粒子のサイズは１０ｎｍ以上が好ましく、より好ましくは１０ｎｍ〜５００ｎｍで、１０ｎｍ〜２００ｎｍがさらに好ましい。また、前記微粒子にはナノチューブも含まれる。 Examples of the fine particles other than platinum include metal oxide fine particles and carbon fine particles, and the size of the fine particles is preferably 10 nm or more, more preferably 10 nm to 500 nm, and further preferably 10 nm to 200 nm. The fine particles also include nanotubes.
作製した白金ナノ粒子被覆微粒子を自動車の排ガス浄化用触媒や電池用触媒などに用いたところ、白金の量を減じた悪影響はみられなかった。 When the produced platinum nanoparticle-coated fine particles were used as a catalyst for exhaust gas purification of automobiles, a catalyst for batteries, etc., there was no adverse effect of reducing the amount of platinum.
本発明の白金ナノ粒子被覆微粒子は、自動車の排ガス浄化用触媒や電池用触媒など各種の触媒に用いることができ、広い技術分野において使用して大きな効果を発揮するものである。 The platinum nanoparticle-coated fine particles of the present invention can be used for various catalysts such as automobile exhaust gas purification catalysts and battery catalysts, and exhibit great effects when used in a wide range of technical fields.
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| CN114618476A (en) * | 2022-02-16 | 2022-06-14 | 中国科学院大连化学物理研究所 | Monoatomic platinum-based catalyst, and preparation method and application thereof |
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