JP7194938B2 - Method for producing hydrogen and/or oxygen - Google Patents
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- JP7194938B2 JP7194938B2 JP2019014652A JP2019014652A JP7194938B2 JP 7194938 B2 JP7194938 B2 JP 7194938B2 JP 2019014652 A JP2019014652 A JP 2019014652A JP 2019014652 A JP2019014652 A JP 2019014652A JP 7194938 B2 JP7194938 B2 JP 7194938B2
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 title claims description 37
- 239000001257 hydrogen Substances 0.000 title claims description 37
- 229910052739 hydrogen Inorganic materials 0.000 title claims description 37
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims description 24
- 239000001301 oxygen Substances 0.000 title claims description 24
- 229910052760 oxygen Inorganic materials 0.000 title claims description 24
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- 239000002245 particle Substances 0.000 claims description 120
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 47
- 239000003054 catalyst Substances 0.000 claims description 41
- 229910000480 nickel oxide Inorganic materials 0.000 claims description 36
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 claims description 36
- 229910000510 noble metal Inorganic materials 0.000 claims description 35
- 239000002923 metal particle Substances 0.000 claims description 31
- 239000010931 gold Substances 0.000 claims description 25
- 238000000034 method Methods 0.000 claims description 21
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 20
- 229910052737 gold Inorganic materials 0.000 claims description 20
- 239000013078 crystal Substances 0.000 claims description 17
- 238000007254 oxidation reaction Methods 0.000 claims description 12
- 230000003647 oxidation Effects 0.000 claims description 11
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 claims description 9
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 9
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 8
- 229910052709 silver Inorganic materials 0.000 claims description 8
- 239000004332 silver Substances 0.000 claims description 8
- 230000001678 irradiating effect Effects 0.000 claims description 4
- 229910052763 palladium Inorganic materials 0.000 claims description 4
- 229910052697 platinum Inorganic materials 0.000 claims description 4
- 239000010970 precious metal Substances 0.000 claims description 4
- 239000004065 semiconductor Substances 0.000 description 43
- 238000010521 absorption reaction Methods 0.000 description 11
- 238000000354 decomposition reaction Methods 0.000 description 9
- 238000010438 heat treatment Methods 0.000 description 8
- 239000002994 raw material Substances 0.000 description 8
- 239000011941 photocatalyst Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 230000000694 effects Effects 0.000 description 6
- 239000012528 membrane Substances 0.000 description 6
- 239000002105 nanoparticle Substances 0.000 description 6
- 238000002198 surface plasmon resonance spectroscopy Methods 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- 238000003917 TEM image Methods 0.000 description 4
- 230000005284 excitation Effects 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- FOIXSVOLVBLSDH-UHFFFAOYSA-N Silver ion Chemical compound [Ag+] FOIXSVOLVBLSDH-UHFFFAOYSA-N 0.000 description 3
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 3
- 238000002371 ultraviolet--visible spectrum Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910021607 Silver chloride Inorganic materials 0.000 description 2
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- 238000000862 absorption spectrum Methods 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 239000004202 carbamide Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000005119 centrifugation Methods 0.000 description 2
- 238000004817 gas chromatography Methods 0.000 description 2
- 239000012510 hollow fiber Substances 0.000 description 2
- 230000001699 photocatalysis Effects 0.000 description 2
- 229920001721 polyimide Polymers 0.000 description 2
- 238000006862 quantum yield reaction Methods 0.000 description 2
- 239000010948 rhodium Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 2
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(1+) nitrate Chemical compound [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910002601 GaN Inorganic materials 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 150000003841 chloride salts Chemical class 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000013068 control sample Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- LELOWRISYMNNSU-UHFFFAOYSA-N hydrogen cyanide Chemical compound N#C LELOWRISYMNNSU-UHFFFAOYSA-N 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 229910052741 iridium Inorganic materials 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 description 1
- 229910052762 osmium Inorganic materials 0.000 description 1
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 description 1
- 238000007146 photocatalysis Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 229910052703 rhodium Inorganic materials 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 229910052707 ruthenium Inorganic materials 0.000 description 1
- 229910052594 sapphire Inorganic materials 0.000 description 1
- 239000010980 sapphire Substances 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 229910001961 silver nitrate Inorganic materials 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- VEALVRVVWBQVSL-UHFFFAOYSA-N strontium titanate Chemical compound [Sr+2].[O-][Ti]([O-])=O VEALVRVVWBQVSL-UHFFFAOYSA-N 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 238000000870 ultraviolet spectroscopy Methods 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
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- Oxygen, Ozone, And Oxides In General (AREA)
- Catalysts (AREA)
Description
本発明は、水素と酸素を効率的に製造するための方法、および、当該方法において有効に使用できる触媒に関するものである。 The present invention relates to a method for efficiently producing hydrogen and oxygen, and a catalyst that can be effectively used in the method.
近年、化石資源の代替エネルギーとして水素が注目されており、太陽エネルギーと水のみから水素を生成できる光触媒が盛んに研究されている。光触媒性能を示す物質としては酸化チタンが最も有名だが、酸化チタン中の電子を励起させるには紫外光が必要である。 In recent years, attention has been focused on hydrogen as an alternative energy to fossil resources, and photocatalysts capable of producing hydrogen only from solar energy and water have been extensively studied. Titanium oxide is the most famous substance that exhibits photocatalytic performance, but ultraviolet light is required to excite the electrons in titanium oxide.
しかし、紫外線は太陽光の数パーセントを占めるに過ぎないため、太陽光の大部分を占める可視光を有効に利用できる光触媒が求められている。そこで、非特許文献１には、アルミニウム電極上に酸化ニッケル膜を形成し、更に金粒子が担持されている光触媒が開示されている。非特許文献１では、金粒子の局在表面プラズモン共鳴励起により、金から酸化ニッケル膜にホットホールが注入されることが報告されている。金粒子の表面プラズモン共鳴波長は粒径などに依存するが、可視光域に調整することは十分に可能である。 However, since ultraviolet light occupies only a few percent of sunlight, a photocatalyst that can effectively utilize visible light, which occupies most of sunlight, is desired. Therefore, Non-Patent Document 1 discloses a photocatalyst in which a nickel oxide film is formed on an aluminum electrode and gold particles are further supported. Non-Patent Document 1 reports that hot holes are injected from gold into a nickel oxide film by localized surface plasmon resonance excitation of gold particles. The surface plasmon resonance wavelength of gold particles depends on the particle size, etc., but it is fully possible to adjust it to the visible light range.
また、非特許文献２には、サファイア基板上にｐ－窒化ガリウム膜を形成し、更に金粒子が担持されている光触媒により、波長が約５７０ｎｍの光が吸収され、二酸化炭素が一酸化炭素に還元されたことが記載されている。 In addition, in Non-Patent Document 2, a photocatalyst in which a p-gallium nitride film is formed on a sapphire substrate and gold particles are supported absorbs light with a wavelength of about 570 nm, and carbon dioxide is converted to carbon monoxide. It is stated that it has been returned.
上述した通り、金粒子による局在表面プラズモン共鳴を利用した光触媒の原理は開発されている。しかし上記従来技術の効率は決して高いものではなかった。
例えば非特許文献１に記載の光触媒の内部量子効率（ＩＱＥ： Ｉｎｔｅｒｎａｌ Ｑｕａｎｔｕｍ Ｅｆｆｉｃｉｅｎｃｙ）は約０．２％以下である。外部量子効率（ＥＱＥ： Ｅｘｔｅｒｎａｌ Ｑｕａｎｔｕｍ Ｅｆｆｉｃｉｅｎｃｙ）は、内部量子効率に加えて光取り出し効率が考慮されたものであるので、この光触媒の外部量子効率は更に低くなるはずである。
そこで、本発明は、可視光により励起される触媒を用い、水を効率的に分解することにより水素および／または酸素を製造する方法を提供することを目的とする。
As described above, the principle of photocatalysis using localized surface plasmon resonance with gold particles has been developed. However, the efficiency of the above-described prior art is not high.
For example, the internal quantum efficiency (IQE) of the photocatalyst described in Non-Patent Document 1 is about 0.2% or less. External quantum efficiency (EQE) takes into consideration light extraction efficiency in addition to internal quantum efficiency, so the external quantum efficiency of this photocatalyst should be even lower.
Accordingly, an object of the present invention is to provide a method for producing hydrogen and/or oxygen by efficiently decomposing water using a catalyst excited by visible light.
本発明者らは、上記課題を解決するために鋭意研究を重ねた。その結果、特定の半導体粒子に貴金属粒子を担持した触媒を用いることにより、可視光を含む光を利用して水を効率的に分解することが可能になり、水素と酸素を容易に製造できることを見出して、本発明を完成した。
以下、本発明を示す。
The present inventors have made intensive studies to solve the above problems. As a result, by using a catalyst in which noble metal particles are supported on specific semiconductor particles, it becomes possible to efficiently decompose water using light including visible light, and hydrogen and oxygen can be easily produced. I found it and completed the present invention.
The present invention is shown below.
［１］ 水素および／または酸素を製造するための方法であって、
水中、貴金属粒子および半導体粒子を含む触媒に、可視光を含む光を照射する工程を含み、
上記半導体粒子は、その価電子帯の上限が水の酸化電位よりも正の位置にあるものであり、
上記貴金属粒子が上記半導体粒子に担持されていることを特徴とする方法。
［２］ 上記貴金属粒子が金粒子であり、赤色光を含む光を照射する上記［１］に記載の方法。
［３］ 上記貴金属粒子が銀粒子であり、緑色光を含む光を照射する上記［１］に記載の方法。
［４］ 上記貴金属粒子の粒子径の短軸が２ｎｍ以上、２００ｎｍ以下である上記［１］～［３］のいずれかに記載の方法。
［５］ 上記半導体粒子が酸化ニッケル粒子である上記［１］～［４］のいずれかに記載の方法。
［６］ 上記酸化ニッケル粒子の結晶方位＜１１１＞の結晶子サイズが２５．０ｎｍ以上、結晶方位＜２００＞の結晶子サイズが２５．０ｎｍ以上、結晶方位＜２２０＞の結晶子サイズが２１．０ｎｍ以上である上記［５］に記載の方法。
［７］ 上記半導体粒子の比表面積が３ｍ2／ｇ以上である上記［１］～［６］のいずれかに記載の方法。
［８］ 上記半導体粒子の大きさが１００ｎｍ以上、５００ｎｍ以下である上記［１］～［６］のいずれかに記載の方法。
［９］ 貴金属粒子および半導体粒子を含み、
上記半導体粒子の価電子帯の上限が水の酸化電位よりも正の位置にあり、
上記貴金属粒子が上記半導体粒子に担持されており、
上記半導体粒子の比表面積が３ｍ2／ｇ以上であることを特徴とする水素および／または酸素の製造用触媒。
[1] A method for producing hydrogen and/or oxygen, comprising:
A step of irradiating a catalyst containing precious metal particles and semiconductor particles in water with light containing visible light,
The semiconductor particles have an upper limit of the valence band at a position more positive than the oxidation potential of water,
A method, wherein the noble metal particles are supported on the semiconductor particles.
[2] The method according to [1] above, wherein the noble metal particles are gold particles, and light including red light is irradiated.
[3] The method according to [1] above, wherein the noble metal particles are silver particles, and light including green light is irradiated.
[4] The method according to any one of [1] to [3] above, wherein the minor axis of the particle diameter of the noble metal particles is 2 nm or more and 200 nm or less.
[5] The method according to any one of [1] to [4] above, wherein the semiconductor particles are nickel oxide particles.
[6] The crystallite size of the crystal orientation <111> of the nickel oxide particles is 25.0 nm or more, the crystallite size of the crystal orientation <200> is 25.0 nm or more, and the crystallite size of the crystal orientation <220> is 21.0 nm or more. The method according to the above [5], which is 0 nm or more.
[7] The method according to any one of [1] to [6] above, wherein the semiconductor particles have a specific surface area of 3 m 2 /g or more.
[8] The method according to any one of [1] to [6] above, wherein the semiconductor particles have a size of 100 nm or more and 500 nm or less.
[9] containing noble metal particles and semiconductor particles,
The upper limit of the valence band of the semiconductor particles is at a position more positive than the oxidation potential of water,
The noble metal particles are supported on the semiconductor particles,
A catalyst for producing hydrogen and/or oxygen, wherein the semiconductor particles have a specific surface area of 3 m 2 /g or more.
本発明方法によれば、太陽光に最も豊富に含まれる可視光の照射により、水を効率的に分解して水素と酸素を発生させることができる。また、特定の半導体粒子に貴金属粒子を担持した本発明に係る触媒は、簡便に製造することが可能である。よって本発明は、水から水素と酸素を容易に製造できる技術として、産業上極めて有用である。 According to the method of the present invention, water can be efficiently decomposed to generate hydrogen and oxygen by irradiating visible light, which is most abundantly contained in sunlight. Moreover, the catalyst according to the present invention in which noble metal particles are supported on specific semiconductor particles can be easily produced. Therefore, the present invention is industrially extremely useful as a technique for easily producing hydrogen and oxygen from water.
本発明に係る水素および／または酸素を製造するための方法は、水中、貴金属粒子および半導体粒子を含む触媒に、可視光を含む光を照射する工程を含むことを特徴とする。 A method for producing hydrogen and/or oxygen according to the present invention is characterized by including a step of irradiating a catalyst containing precious metal particles and semiconductor particles in water with light including visible light.
本発明で用いる半導体粒子は、その価電子帯の上限が水の酸化電位よりも正の位置にあるものである。本開示において「水の酸化」とは、２Ｈ2Ｏ＋４ｈ+→Ｏ2＋４Ｈ+［式中、ｈ+は正孔を示す］の式で表される反応をいい、「水の酸化電位」とは、＋１．２３Ｖ ｖｓ．ＮＨＥ（標準水素電極，Ｎｏｒｍａｌ Ｈｙｄｒｏｇｅｎ Ｅｌｅｃｔｒｏｄｅ） ａｔ ｐＨ０である。 The semiconductor particles used in the present invention have the upper limit of the valence band at a more positive position than the oxidation potential of water. In the present disclosure, "oxidation of water" refers to a reaction represented by the formula 2H 2 O + 4h + →O 2 + 4H + [wherein h + represents a hole], and "oxidation potential of water" , +1.23V vs. NHE (Normal Hydrogen Electrode) at pH0.
半導体は、導体や絶縁体に比べて中間的な抵抗率を持つ物質である。半導体中の電子は価電子帯中に存在しているが、禁制帯（バンドギャップ）を超えるエネルギーを電子に加えることで伝導帯に電子を励起させることが可能である。伝導価電子帯に励起した電子は自由に動くことが可能であり、他の物質に移って還元することも可能である。また、電子が励起した後に残った正孔が他の物質から電子を奪えば、自身は変化せずに他の物質を酸化還元することとなり、これが光触媒の基本的な原理である。なお、本開示において「価電子帯の上限」とは、価電子帯に含まれる電子の中で最も高いエネルギーを有する電子のエネルギー準位をいう。価電子帯の上限を求めるためには、インピーダンス測定装置（例えば、「ＨＺ－７０００＋ＨＺＡ－ＦＲＡ１」北斗電工社製）を用い、半導体粒子で作製した電極を電解質溶液に浸漬し、参照電極（Ａｇ／ＡｇＣｌ）との間に電圧を負荷し、２５℃で電気容量を測定する。電極および電解液界面の電気容量と電位との間には、Ｍｏｔｔ－Ｓｃｈｏｔｔｋｙの関係式が成り立つ。電気化学的に安定な半導体の測定結果をＭｏｔｔ－Ｓｃｈｏｔｔｋｙの関係式に代入すると、プロットに直線部分が存在する。その直線を外挿した際のＸ軸との交点から、価電子帯の上限が求められる。上記価電子帯の上限の測定には参照電極（Ａｇ／ＡｇＣｌ）を用いていることから、０．１９９Ｖを足すことにより標準水素電極を基準とする値に換算する。 Semiconductors are materials with intermediate resistivity compared to conductors and insulators. Electrons in a semiconductor exist in the valence band, but it is possible to excite the electrons in the conduction band by applying energy exceeding the forbidden band (bandgap) to the electrons. Electrons excited in the conduction valence band can move freely and can be transferred to other substances for reduction. Also, if the holes remaining after electrons are excited steal electrons from other substances, they will oxidize and reduce other substances without changing themselves. This is the basic principle of photocatalysts. In the present disclosure, the “upper limit of the valence band” refers to the energy level of the electron having the highest energy among the electrons included in the valence band. In order to determine the upper limit of the valence band, an impedance measuring device (eg, "HZ-7000+HZA-FRA1" manufactured by Hokuto Denko) is used, an electrode made of semiconductor particles is immersed in an electrolyte solution, and a reference electrode (Ag/ AgCl) and the capacitance is measured at 25°C. The Mott-Schottky relational expression holds between the capacitance and potential of the electrode and the electrolyte interface. Substituting the measurement results of the electrochemically stable semiconductor into the Mott-Schottky relationship, there is a linear portion in the plot. The upper limit of the valence band can be obtained from the point of intersection with the X-axis when the straight line is extrapolated. Since a reference electrode (Ag/AgCl) is used to measure the upper limit of the valence band, 0.199 V is added to convert to a value based on the standard hydrogen electrode.
本開示において「価電子帯の上限が水の酸化電位よりも正の位置にある」とは、価電子帯の上限が水の酸化電位よりもエネルギー準位で低い方向にあることをいう。本発明で用いる半導体粒子は、その価電子帯の上限が水の酸化電位よりも正の位置にあることにより、貴金属粒子の正孔が半導体粒子中の電子を奪うことによって、水に対する酸化力を有する正孔が半導体粒子中に生じ、水から酸素を発生させる酸化反応を進行させることができる。 In the present disclosure, "the upper limit of the valence band is at a more positive position than the oxidation potential of water" means that the upper limit of the valence band is in the direction lower in energy level than the oxidation potential of water. Since the upper limit of the valence band of the semiconductor particles used in the present invention is at a more positive position than the oxidation potential of water, the holes of the noble metal particles take away electrons in the semiconductor particles, thereby increasing the oxidizing power to water. Holes are generated in the semiconductor particles, and an oxidation reaction that generates oxygen from water can proceed.
価電子帯の上限が水の酸化電位よりも正の位置にある半導体としては、例えば、酸化ニッケル、酸化亜鉛、酸化チタン、酸化鉄、硫化モリブデン、グラファイト状窒化炭素、およびチタン酸ストロンチウムを挙げることができる。 Examples of semiconductors whose valence band upper limit is more positive than the oxidation potential of water include nickel oxide, zinc oxide, titanium oxide, iron oxide, molybdenum sulfide, graphitic carbon nitride, and strontium titanate. can be done.
本発明者らによる実験的知見によれば、半導体粒子を構成する結晶の結晶子サイズが大きいほど、水の分解活性が高くなり、水素と酸素の製造効率は高まる。例えば、酸化ニッケル粒子の結晶方位＜１１１＞の結晶子サイズとしては２５．０ｎｍ以上、結晶方位＜２００＞の結晶子サイズとしては２５．０ｎｍ以上、結晶方位＜２２０＞の結晶子サイズとしては２１．０ｎｍ以上が好ましい。一方、結晶子サイズが大きい半導体粒子を作製するには高温で焼成する必要があり、その結果、粒子の比表面積が小さくなるため、水との接触面積を十分に確保できなくなるおそれがあり得る。よって、例えば、酸化ニッケル粒子の結晶方位＜１１１＞の結晶子サイズとしては３０．０ｎｍ以下、結晶方位＜２００＞の結晶子サイズとしては３０．０ｎｍ以下、結晶方位＜２２０＞の結晶子サイズとしては２５．０ｎｍ以下が好ましい。なお、結晶子サイズは、半導体粒子をＸ線回折で分析し、得られたＸ線回折パターンと以下のシェラーの式から求めることができる。
τ＝Ｋλ／βｃｏｓθ
［式中、τは結晶子の平均サイズを示し、Ｋは形状因子を示し、λはＸ線波長を示し、βはピーク半値全幅（ラジアン単位）を示し、θはブラッグ角を示す。］
According to experimental findings by the present inventors, the larger the crystallite size of the crystals forming the semiconductor particles, the higher the water-splitting activity and the higher the production efficiency of hydrogen and oxygen. For example, the crystallite size of the crystal orientation <111> of the nickel oxide particles is 25.0 nm or more, the crystallite size of the crystal orientation <200> is 25.0 nm or more, and the crystallite size of the crystal orientation <220> is 21 nm. 0 nm or more is preferable. On the other hand, in order to produce semiconductor particles with a large crystallite size, it is necessary to bake them at a high temperature. Therefore, for example, the crystallite size of the crystal orientation <111> of the nickel oxide particles is 30.0 nm or less, the crystallite size of the crystal orientation <200> is 30.0 nm or less, and the crystallite size of the crystal orientation <220> is 30.0 nm or less. is preferably 25.0 nm or less. The crystallite size can be determined from the X-ray diffraction pattern obtained by analyzing the semiconductor particles by X-ray diffraction and the following Scherrer formula.
τ=Kλ/β cos θ
[wherein τ represents the average crystallite size, K represents the shape factor, λ represents the X-ray wavelength, β represents the peak full width at half maximum (in radians), and θ represents the Bragg angle. ]
本発明で用いる半導体粒子の比表面積としては、１ｍ2／ｇ以上、７０ｍ2／ｇ以下が好ましい。比表面積が１ｍ2／ｇ以上であれば、水との接触面積が十分に大きいので、水を効率的に分解することができる。一方、比表面積が７０ｍ2／ｇ以下であれば、半導体粒子が過剰に小さくなることはなく、取扱性を担保することができる。上記比表面積としては、３ｍ2／ｇ以上がより好ましく、５ｍ2／ｇ以上がより更に好ましく、また、２５ｍ2／ｇ以下がより好ましく、１０ｍ2／ｇ以下がより更に好ましい。 The specific surface area of the semiconductor particles used in the present invention is preferably 1 m 2 /g or more and 70 m 2 /g or less. If the specific surface area is 1 m 2 /g or more, the contact area with water is sufficiently large, so water can be efficiently decomposed. On the other hand, when the specific surface area is 70 m 2 /g or less, the semiconductor particles do not become excessively small, and handleability can be ensured. The specific surface area is more preferably 3 m 2 /g or more, still more preferably 5 m 2 /g or more, more preferably 25 m 2 /g or less, and even more preferably 10 m 2 /g or less.
半導体粒子の大きさとしては、１００ｎｍ以上、５００ｎｍ以下が好ましい。半導体粒子の大きさが５００ｎｍ以下であれば、水との接触面積が大きく、水の分解反応をより効率的に進行せしめることが可能になる。一方、半導体の大きさが１００ｎｍ以上であれば、粒子を構成する結晶子の大きさも十分に大きく、水の分解活性をより確実に確保できるといえる。なお、半導体粒子の大きさは、例えば、粒子を電子顕微鏡で拡大し、１～１００μｍ×１～１００μｍの視野内で全体を観察可能な結晶の最長径と最短径を測定し、その平均として求めることができる。 The size of the semiconductor particles is preferably 100 nm or more and 500 nm or less. If the size of the semiconductor particles is 500 nm or less, the contact area with water is large, and the water decomposition reaction can proceed more efficiently. On the other hand, if the size of the semiconductor is 100 nm or more, the size of the crystallites constituting the particles is sufficiently large, and it can be said that the water-splitting activity can be ensured more reliably. The size of the semiconductor particles is obtained by, for example, enlarging the particles with an electron microscope, measuring the longest diameter and the shortest diameter of the crystal that can be observed in its entirety within a field of view of 1 to 100 μm×1 to 100 μm, and calculating the average. be able to.
本発明に係る触媒は、半導体粒子に貴金属粒子が担持されているものである。本発明において貴金属粒子は、照射された光による局在表面プラズモン共鳴（ＬＳＰＲ）励起により生じた正孔を半導体粒子に注入し、半導体粒子に酸化力を付与すると共に、同じくＬＳＰＲ励起により生じた電子により水を還元して水素を生じる作用を示す。 The catalyst according to the present invention is a catalyst in which noble metal particles are supported on semiconductor particles. In the present invention, the noble metal particles inject holes generated by localized surface plasmon resonance (LSPR) excitation by irradiated light into the semiconductor particles, impart oxidizing power to the semiconductor particles, and also electrons generated by the LSPR excitation. shows the action of reducing water to produce hydrogen.
貴金属としては、金（Ａｕ）、銀（Ａｇ）、白金（Ｐｔ）、パラジウム（Ｐｄ）、ロジウム（Ｒｈ）、イリジウム（Ｉｒ）、ルテニウム（Ｒｕ）、およびオスミウム（Ｏｓ）が挙げられ、金、銀、白金およびパラジウムが好ましく、金および／または銀が好ましい。 Noble metals include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), and osmium (Os); Silver, platinum and palladium are preferred, gold and/or silver being preferred.
貴金属粒子の粒子径は適宜調整すればよいが、例えば、貴金属粒子の短軸の長さとしては、２ｎｍ以上、２００ｎｍ以下が好ましい。当該短軸長さが２００ｎｍ以下であれば、貴金属粒子の比表面積が十分に大きく、十分に光を吸収することができ、水を効率的に分解することができる。また、ＬＳＰＲ波長は粒子の大きさにも依存するが、上記短軸長さが上記範囲にあれば、太陽光に豊富に含まれる可視光による励起が可能になる。なお、上記短軸長さは、例えば、本発明の触媒を電子顕微鏡で観察し、０．１～１００μｍ×０．１～１００μｍの視野内で、半導体粒子に担持されている貴金属粒子の最短径を算出することで分布図として求めることができる。 The particle diameter of the noble metal particles may be appropriately adjusted, but for example, the length of the minor axis of the noble metal particles is preferably 2 nm or more and 200 nm or less. When the minor axis length is 200 nm or less, the noble metal particles have a sufficiently large specific surface area, can sufficiently absorb light, and can efficiently decompose water. Although the LSPR wavelength depends on the size of the particles, excitation by visible light abundantly contained in sunlight becomes possible if the minor axis length is within the above range. The short axis length is, for example, the shortest diameter of the noble metal particles supported on the semiconductor particles within a field of view of 0.1 to 100 μm × 0.1 to 100 μm when observing the catalyst of the present invention with an electron microscope. can be obtained as a distribution map by calculating
貴金属粒子の吸収極大波長は、上記の通り粒子の大きさにも依存し、粒子径が大きくなるほど吸収極大波長は長波長側にシフトする傾向がある。例えばあるデータによれば、２０ｎｍの金ナノ粒子の吸収極大波長は５２０ｎｍ、１００ｎｍの金ナノ粒子の吸収極大波長は５７０ｎｍであり、１００ｎｍ以上の金ナノ粒子は６００ｎｍ以上に及ぶ広い波長範囲の光を吸収することができる。また、１０ｎｍの銀ナノ粒子の吸収極大波長は約４００ｎｍ、１００ｎｍの銀ナノ粒子の吸収極大波長は５００ｎｍを超え、８０ｎｍ以上の銀ナノ粒子にはメインの吸収極大波長ピークよりも短波長側に二次ピークが見られるようになる。これら波長の光は太陽光に豊富に含まれるため、本発明に係る触媒は、太陽光など可視光が豊富に含まれる光を有効に利用することができる。 The maximum absorption wavelength of noble metal particles also depends on the size of the particles as described above, and the maximum absorption wavelength tends to shift to the longer wavelength side as the particle diameter increases. For example, according to certain data, the absorption maximum wavelength of 20 nm gold nanoparticles is 520 nm, the absorption maximum wavelength of 100 nm gold nanoparticles is 570 nm, and gold nanoparticles of 100 nm or more absorb light in a wide wavelength range of 600 nm or more. can be absorbed. In addition, the absorption maximum wavelength of 10 nm silver nanoparticles is about 400 nm, the absorption maximum wavelength of 100 nm silver nanoparticles exceeds 500 nm, and the absorption maximum wavelength of 80 nm or more is two short wavelengths from the main absorption maximum wavelength peak. The next peak can be seen. Since light of these wavelengths is abundantly contained in sunlight, the catalyst according to the present invention can effectively utilize light such as sunlight that contains abundant visible light.
貴金属粒子を担持する半導体粒子触媒は、常法により製造することができる。例えば、先ず、原料半導体粒子を熱処理する。原料半導体粒子の大きさは、目的とする触媒の所望の大きさに応じて適宜調整すればよい。また、原料半導体粒子の熱処理温度も、適宜調整する。例えば、当該熱処理の温度が高い程、結晶子が成長して活性が高くなるといえる。しかし当該温度が過剰に高いと、比表面積が小さくなり、活性が低下し得る。例えば、酸化ニッケル粒子の場合には、６００℃以上、７００℃以下で、１時間以上、１０時間以下熱処理することが好ましい。当該温度としては、６２０℃以上、６８０℃以下が好ましく、当該時間としては、２時間以上、５時間以下が好ましい。 A semiconductor particle catalyst supporting noble metal particles can be produced by a conventional method. For example, first, the raw material semiconductor particles are heat-treated. The size of the raw material semiconductor particles may be appropriately adjusted according to the desired size of the target catalyst. In addition, the heat treatment temperature of the raw material semiconductor particles is also appropriately adjusted. For example, it can be said that the higher the temperature of the heat treatment, the higher the crystallite growth and the higher the activity. However, if the temperature is excessively high, the specific surface area becomes small and the activity can be lowered. For example, in the case of nickel oxide particles, heat treatment is preferably performed at 600° C. or higher and 700° C. or lower for 1 hour or longer and 10 hours or shorter. The temperature is preferably 620° C. or higher and 680° C. or lower, and the time is preferably 2 hours or longer and 5 hours or shorter.
次に、貴金属酸の塩の水溶液など、貴金属元素を含む溶液に熱処理した原料半導体粒子を添加して含浸担持すればよい。貴金属酸の塩としては、塩化金酸などの塩化物を挙げることができる。その際、尿素が存在すると、７０℃付近から沈殿剤としてＮＨ4ＯＨが系内で生成し、貴金属粒子の析出が促進される。貴金属粒子が半導体粒子表面に十分に担持された後、遠心分離や濾過などにより触媒粒子を反応液から分離し、更に水などで十分に洗浄した後に乾燥すればよい。 Next, the heat-treated raw material semiconductor particles may be added to a solution containing a noble metal element such as an aqueous solution of a salt of a noble metal acid, and impregnated and supported. Salts of noble metal acids include chlorides such as chloroauric acid. At this time, if urea is present, NH 4 OH is produced as a precipitant in the system from around 70° C., promoting precipitation of the noble metal particles. After the noble metal particles are sufficiently supported on the surfaces of the semiconductor particles, the catalyst particles are separated from the reaction solution by centrifugation, filtration, etc., washed thoroughly with water, and then dried.
本発明に係る水素および／または酸素を製造するための方法では、水中、貴金属粒子および半導体粒子を含む触媒に、可視光を含む光を照射する。 In the method for producing hydrogen and/or oxygen according to the present invention, a catalyst containing noble metal particles and semiconductor particles in water is irradiated with light including visible light.
触媒の使用量は特に制限されず適宜調整すればよいが、例えば、水１ｍＬあたり０．１ｍｇ以上、３０ｍｇ以下程度とすることができる。使用する水は、酸素などの影響を排除するために、十分に脱気しておくことが好ましい。 The amount of the catalyst to be used is not particularly limited and may be adjusted as appropriate. The water to be used is preferably sufficiently degassed in order to eliminate the influence of oxygen and the like.
照射すべき可視光は、貴金属粒子の吸収極大波長に応じて適宜選択すればよい。例えば、金ナノ粒子には赤色光を含む光を照射し、銀ナノ粒子には緑色光を含む光を照射することが好ましい。可視光は、定義にもよるが、例えば３８０ｎｍ以上、８１０ｎｍ以下の波長の光をいう。可視光の内、紫色光は３８０ｎｍ以上、４５０ｎｍ以下、青色光は４５０ｎｍ以上、４９５ｎｍ以下、緑色光は４９５ｎｍ以上、５７０ｎｍ以下、黄色光は５７０ｎｍ以上、５９０ｎｍ以下、橙色光は５９０ｎｍ以上、６２０ｎｍ以下、赤色光は、通常、５９５ｎｍ以上、８００ｎｍ以下程度、特に６１０ｎｍ以上、７５０ｎｍ以下程度の波長の光をいう。可視光は太陽光にも豊富に含まれており、また、エネルギーが比較的低く安全である。勿論、水と触媒の混合液に照射する光には、可視光以外の光が含まれていてもよい。光の照度も適宜調整すればよいが、例えば、０．５ｍＷ／ｃｍ2以上、１００ｍＷ／ｃｍ2以下とすることができる。 The visible light to be irradiated may be appropriately selected according to the maximum absorption wavelength of the noble metal particles. For example, gold nanoparticles are preferably irradiated with light containing red light, and silver nanoparticles are preferably irradiated with light containing green light. Visible light refers to light with a wavelength of, for example, 380 nm or more and 810 nm or less, although it depends on the definition. Among visible light, violet light is 380 nm or more and 450 nm or less, blue light is 450 nm or more and 495 nm or less, green light is 495 nm or more and 570 nm or less, yellow light is 570 nm or more and 590 nm or less, orange light is 590 nm or more and 620 nm or less, Red light generally refers to light with a wavelength of approximately 595 nm or more and 800 nm or less, particularly approximately 610 nm or more and 750 nm or less. Visible light is also abundant in sunlight, and its energy is relatively low and safe. Of course, light other than visible light may be included in the light with which the mixture of water and catalyst is irradiated. The illuminance of the light may be adjusted as appropriate, and may be, for example, 0.5 mW/cm 2 or more and 100 mW/cm 2 or less.
触媒に光を照射する際の温度は、常温、特に５℃以上、４０℃以下でよい。光の照射時間は特に制限されず、光の照射時間が長い程より多くの水素と酸素を製造することができる。反応の進行に伴って水が消費された場合には、水を断続的または連続的に添加してもよい。 The temperature at which the catalyst is irradiated with light may be normal temperature, particularly 5° C. or higher and 40° C. or lower. The light irradiation time is not particularly limited, and the longer the light irradiation time, the more hydrogen and oxygen can be produced. If water is consumed as the reaction progresses, water may be added intermittently or continuously.
本発明方法により、半導体粒子表面からは正孔に由来する酸化力により水から酸素が発生し、貴金属粒子表面からは電子に由来する還元力により水から水素が発生する。なお、生じた水素と酸素は、分離膜モジュールを用いて分離することが可能である。水素と酸素と分離するための分離膜としては、ポリイミド中空糸膜、ポリイミド中空糸の炭素膜、リグノクレゾールを多孔質α－アルミナチューブにコートした複合膜の炭素膜、シリカ膜などが開発されている。 According to the method of the present invention, oxygen is generated from water by the oxidizing power derived from holes on the surface of the semiconductor particles, and hydrogen is generated from water by the reducing power derived from electrons on the surface of the noble metal particles. The generated hydrogen and oxygen can be separated using a separation membrane module. Separation membranes for separating hydrogen and oxygen include polyimide hollow fiber membranes, polyimide hollow fiber carbon membranes, composite carbon membranes in which lignocresol is coated on porous α-alumina tubes, and silica membranes. there is
以下、実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも勿論可能であり、それらはいずれも本発明の技術的範囲に包含される。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be modified appropriately within the scope that can conform to the gist of the above and later descriptions. It is of course possible to implement them, and all of them are included in the technical scope of the present invention.
実施例１： 触媒の調製
（１）触媒の調製
粒径５０ｎｍ未満の酸化ニッケル粒子（Ｓｉｇｍａ－Ａｌｄｒｉｃｈ社製）を、４５０℃、５５０℃、６５０℃、７５０℃、８５０℃、または１０００℃で４時間熱処理した。別途、２．４３ｍＭの塩化金酸水溶液１０ｍＬに、塩化金酸の１００倍質量の尿素を加え、更に酸化ニッケル粒子５００ｍｇを加えた後、８０℃で２４時間攪拌した。次いで、遠心分離により上澄液を除去した後、粒子を水で１０回、アセトンで１回洗浄し、真空乾燥した。乾燥した粉末をるつぼに移し、４００℃で１時間焼成した。
Example 1: Preparation of Catalyst (1) Preparation of Catalyst Nickel oxide particles (manufactured by Sigma-Aldrich) with a particle size of less than 50 nm were heated at 450°C, 550°C, 650°C, 750°C, 850°C, or 1000°C for 4 hours. heat treated for hours. Separately, to 10 mL of a 2.43 mM chloroauric acid aqueous solution, urea of 100 times the mass of chloroauric acid was added, and 500 mg of nickel oxide particles were further added, followed by stirring at 80° C. for 24 hours. After removing the supernatant by centrifugation, the particles were washed 10 times with water and once with acetone, and dried under vacuum. The dried powder was transferred to a crucible and calcined at 400° C. for 1 hour.
（２）ＴＥＭ観察
得られた触媒を透過型電子顕微鏡（ＴＥＭ）で観察した。６５０℃で熱処理した酸化ニッケル粒子から得られた触媒のＴＥＭ像を図１に示す。
図１の通り、酸化ニッケル粒子上には、１０～２０ｎｍ程度の金粒子が高分散に担持されていることが確認された。
(2) TEM Observation The obtained catalyst was observed with a transmission electron microscope (TEM). A TEM image of a catalyst obtained from nickel oxide particles heat-treated at 650° C. is shown in FIG.
As shown in FIG. 1, it was confirmed that gold particles with a size of about 10 to 20 nm were supported on the nickel oxide particles in a highly dispersed manner.
（３）紫外可視分光測定
６５０℃で熱処理した酸化ニッケル粒子から得られた触媒を、紫外可視分光法で分析した。また、対照試料として、６５０℃で熱処理した原料酸化ニッケル粒子も同様に分析した。紫外可視吸収スペクトル（ＵＶ－Ｖｉｓスペクトル）を図２に示す。図２中、ＮｉＯ粒子のＵＶ－ＶｉｓスペクトルとＡｕ／ＮｉＯ粒子のＵＶ－Ｖｉｓスペクトルとの差を点線で示す。
図２に示される結果の通り、Ａｕ／ＮｉＯ粒子には６００ｎｍ付近にＮｉＯ粒子のみには認められない大きな吸収ピークが認められる。このピークは、金ナノ粒子の局在表面プラズモン共鳴による吸収に由来するものであると考えられる。
(3) Ultraviolet-Visible Spectroscopic Measurement A catalyst obtained from nickel oxide particles heat-treated at 650° C. was analyzed by ultraviolet-visible spectroscopy. As a control sample, raw material nickel oxide particles heat-treated at 650° C. were also analyzed in the same manner. An ultraviolet-visible absorption spectrum (UV-Vis spectrum) is shown in FIG. In FIG. 2, the dotted line indicates the difference between the UV-Vis spectrum of the NiO particles and the UV-Vis spectrum of the Au/NiO particles.
As shown in FIG. 2, the Au/NiO particles have a large absorption peak near 600 nm, which is not observed only in the NiO particles. This peak is considered to be derived from absorption by localized surface plasmon resonance of gold nanoparticles.
試験例１： 水分解試験
純水１０ｍＬに各Ａｕ／ＮｉＯ粒子（１０ｍｇ）を加え、アルゴンガスを吹き込んで十分に脱気した。その後、赤色ＬＥＤ（λ＝６４０±４０ｎｍ，Ｉ＝３．３ｍＷ／ｃｍ2）を使って光照射した。所定時間ごとに気相成分を採取し、ガスクロマトグラフにより、生成した水素および酸素の定量を行った。６５０℃で熱処理した酸化ニッケル粒子から得られた触媒による結果を図３に示し、原料酸化ニッケル粒子の熱処理温度と水素生成速度との関係を図４に示す。
図３に示される結果の通り、暗所や、金粒子を担持していないＮｉＯ粒子に赤色光を照射した場合には、水素は全く発生しないか或いは極僅かしか生成していない。それに対してＡｕ／ＮｉＯ粒子に赤色光を照射した場合には、水素と酸素が経時的に増加している。水素と酸素の増加量のモル比は２：１であることから、水の分解反応が進行していることは明らかである。
また、図４に示される結果の通り、６５０℃で熱処理した酸化ニッケル粒子から得られた触媒が最も高い活性を有することが分かった。
更に、熱処理した原料酸化ニッケル粒子をＸ線回折法で分析し、シェラーの式から結晶子サイズを求めた。結果を図５と表１に示す。
Test Example 1: Water decomposition test Each Au/NiO particle (10 mg) was added to 10 mL of pure water, and argon gas was blown into the mixture for sufficient degassing. After that, light irradiation was performed using a red LED (λ=640±40 nm, I=3.3 mW/cm 2 ). Gas phase components were sampled at predetermined time intervals, and hydrogen and oxygen produced were quantified by gas chromatography. FIG. 3 shows the results of the catalyst obtained from the nickel oxide particles heat-treated at 650° C., and FIG. 4 shows the relationship between the heat treatment temperature of the starting nickel oxide particles and the hydrogen production rate.
As the results shown in FIG. 3 show, hydrogen was not generated at all or was generated in a very small amount when NiO particles not supporting gold particles were irradiated with red light in a dark place. On the other hand, when the Au/NiO particles were irradiated with red light, hydrogen and oxygen increased with time. Since the molar ratio of the increased amount of hydrogen and oxygen is 2:1, it is clear that the decomposition reaction of water is progressing.
Moreover, as shown in FIG. 4, it was found that the catalyst obtained from the nickel oxide particles heat-treated at 650° C. had the highest activity.
Furthermore, the heat-treated raw material nickel oxide particles were analyzed by the X-ray diffraction method, and the crystallite size was obtained from Scherrer's formula. The results are shown in FIG. 5 and Table 1.
図５と表１に示される結果の通り、熱処理温度の上昇と共に結晶子サイズが大きくなり、結晶性が向上していることが分かった。また、酸化ニッケルにおいては、熱処理温度とキャリアであるホールの密度には相関関係があることが報告されている。よって、６５０℃で熱処理した酸化ニッケル粒子から得られた触媒が最も高い活性を示す理由としては、結晶性とホール密度が共に高いことが考えられる。 As shown in FIG. 5 and Table 1, it was found that the crystallite size increased as the heat treatment temperature increased, and the crystallinity improved. In nickel oxide, it has been reported that there is a correlation between the heat treatment temperature and the density of holes, which are carriers. Therefore, the reason why the catalyst obtained from the nickel oxide particles heat-treated at 650° C. exhibits the highest activity is considered to be that both the crystallinity and the hole density are high.
試験例２： 水分解試験
上記試験例１において、照射光の波長を３６５ｎｍ、４６０ｎｍ、５３０ｎｍ、６４０ｎｍ、または８５０ｎｍに限定した以外の条件は同様にして、生成する水素の量を測定した。照射光の波長と水素生成速度およびＫｕｂｅｌｋａ－Ｍｕｎｋとの関係を図６と表２に、照射光の波長と外部量子収率およびＫｕｂｅｌｋａ－Ｍｕｎｋとの関係を図７と表２に示す。なお、Ｋｕｂｅｌｋａ－Ｍｕｎｋは、粉末の吸収スペクトルの指標であり、図６，７に示すＫｕｂｅｌｋａ－Ｍｕｎｋは、図２のＤｉｆｆｅｒｅｎｃｅと同様に、ＮｉＯ粒子のＵＶ－ＶｉｓスペクトルとＡｕ／ＮｉＯ粒子のＵＶ－Ｖｉｓスペクトルとの差を示している。
Test Example 2: Water Decomposition Test The amount of hydrogen produced was measured in the same manner as in Test Example 1 except that the wavelength of the irradiation light was limited to 365 nm, 460 nm, 530 nm, 640 nm, or 850 nm. FIG. 6 and Table 2 show the relationship between the wavelength of the irradiation light and the hydrogen production rate and Kubelka-Munk, and FIG. The Kubelka-Munk is an index of the absorption spectrum of the powder, and the Kubelka-Munk shown in FIGS. 6 and 7 are similar to the Difference in FIG. Differences from Vis spectra are shown.
図６，７と表２に示される結果の通り、波長６４０ｎｍの赤色光を照射した場合に水素の生成速度が高くなったことから、水の分解反応は金ナノ粒子の局在表面プラズモン共鳴による光吸収により進行していることは明らかである。
また、図６，７と表２に示される結果の通り、６４０ｎｍの赤色光を照射した場合における外部量子収率は約０．４％であった。この値は、水の分解におけるこの波長域で、従来に無い最高の値であるといえる。
As shown in FIGS. 6 and 7 and Table 2, the rate of hydrogen generation increased when red light with a wavelength of 640 nm was applied, suggesting that the water decomposition reaction is due to the localized surface plasmon resonance of gold nanoparticles. It is clear that it proceeds by light absorption.
Moreover, as shown in FIGS. 6 and 7 and Table 2, the external quantum yield was about 0.4% when irradiated with red light of 640 nm. This value can be said to be the highest value that has never existed in this wavelength range in the decomposition of water.
実施例２： 触媒の調製
（１）Ａｇ／ＮｉＯ粒子
粒径５０ｎｍ未満の酸化ニッケル粒子（Ｓｉｇｍａ－Ａｌｄｒｉｃｈ社製）を６５０℃で４時間熱処理した。１９ｍＭの硝酸銀水溶液１０ｍＬに、焼成した酸化ニッケル粒子１ｇを加えた後、５０℃で蒸発乾固した。粒子を乾燥した粉末をるつぼに移し、６００℃で１時間焼成した。
Example 2 Preparation of Catalyst (1) Ag/NiO Particles Nickel oxide particles (manufactured by Sigma-Aldrich) with a particle size of less than 50 nm were heat-treated at 650° C. for 4 hours. After adding 1 g of calcined nickel oxide particles to 10 mL of a 19 mM silver nitrate aqueous solution, the mixture was evaporated to dryness at 50°C. The dried powder of the particles was transferred to a crucible and calcined at 600° C. for 1 hour.
（２）ＴＥＭ観察
得られた触媒を透過型電子顕微鏡（ＴＥＭ）で観察した。得られた触媒のＴＥＭ像を図８に示す。
図８の通り、酸化ニッケル粒子上には、１０～２０ｎｍ程度の銀粒子が高分散に担持されていることが確認された。
(2) TEM Observation The obtained catalyst was observed with a transmission electron microscope (TEM). A TEM image of the obtained catalyst is shown in FIG.
As shown in FIG. 8, it was confirmed that silver particles of about 10 to 20 nm were highly dispersedly supported on the nickel oxide particles.
試験例３： 水分解試験
使用直前に、実施例２で得たＡｇ／ＮｉＯ粒子を、アルゴン気流下、５００℃で３０分間アニーリングした。当該Ａｇ／ＮｉＯ粒子（１０ｍｇ）を純水１０ｍＬに加え、アルゴンガスを吹き込んで十分に脱気した。その後、緑色ＬＥＤ（λex＝５３０±４０ｎｍ）を使って光照射した。所定時間ごとに気相成分を採取し、ガスクロマトグラフにより、生成した水素を定量した。結果を図９に示す。
図９に示される結果の通り、Ａｇ／ＮｉＯ粒子に緑色光を照射した場合には、水から水素を経時的に効率良く製造できることが示された。
Test Example 3: Water decomposition test Immediately before use, the Ag/NiO particles obtained in Example 2 were annealed at 500°C for 30 minutes under an argon stream. The Ag/NiO particles (10 mg) were added to 10 mL of pure water and thoroughly deaerated by blowing argon gas. It was then illuminated using a green LED (λ ex =530±40 nm). Gas phase components were sampled at predetermined time intervals, and the produced hydrogen was quantified by gas chromatography. The results are shown in FIG.
As the results shown in FIG. 9 show, when Ag/NiO particles were irradiated with green light, hydrogen could be efficiently produced from water over time.
Claims (9)
水中、貴金属粒子および酸化ニッケル粒子を含む触媒に、可視光を含む光を照射する工程を含み、
上記酸化ニッケル粒子は、その価電子帯の上限が水の酸化電位よりも正の位置にあるものであり、
上記貴金属粒子が上記酸化ニッケル粒子に担持されており、
上記酸化ニッケル粒子の結晶方位＜１１１＞の結晶子サイズが２５．０ｎｍ以上、結晶方位＜２００＞の結晶子サイズが２５．０ｎｍ以上、結晶方位＜２２０＞の結晶子サイズが２１．０ｎｍ以上であることを特徴とする方法。 A method for producing hydrogen and/or oxygen, comprising:
A step of irradiating a catalyst containing precious metal particles and nickel oxide particles in water with light containing visible light,
In the nickel oxide particles , the upper limit of the valence band is at a position more positive than the oxidation potential of water,
The noble metal particles are supported on the nickel oxide particles ,
The crystallite size of the crystal orientation <111> of the nickel oxide particles is 25.0 nm or more, the crystallite size of the crystal orientation <200> is 25.0 nm or more, and the crystallite size of the crystal orientation <220> is 21.0 nm or more. A method characterized by:
上記酸化ニッケル粒子の価電子帯の上限が水の酸化電位よりも正の位置にあり、
上記貴金属粒子が上記酸化ニッケル粒子に担持されており、
上記酸化ニッケル粒子の比表面積が３ｍ2／ｇ以上であり、上記酸化ニッケル粒子の結晶方位＜１１１＞の結晶子サイズが２５．０ｎｍ以上、結晶方位＜２００＞の結晶子サイズが２５．０ｎｍ以上、結晶方位＜２２０＞の結晶子サイズが２１．０ｎｍ以上であることを特徴とする水素および／または酸素の製造用触媒。 containing precious metal particles and nickel oxide particles ,
The upper limit of the valence band of the nickel oxide particles is at a position more positive than the oxidation potential of water,
The noble metal particles are supported on the nickel oxide particles ,
The specific surface area of the nickel oxide particles is 3 m 2 /g or more, the crystallite size of the crystal orientation <111> of the nickel oxide particles is 25.0 nm or more, and the crystallite size of the crystal orientation <200> is 25.0 nm. A catalyst for producing hydrogen and/or oxygen, wherein the crystallite size of the <220> crystal orientation is 21.0 nm or more .
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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| JP2014046236A (en) | 2012-08-30 | 2014-03-17 | Toyota Central R&D Labs Inc | Semiconductor hetero particle |
Non-Patent Citations (3)
| Title |
|---|
| Juan Gomez-Perez, et al.，Catalysis Today，2017年，Vol.284，PP.37-43 |
| Xiao-Bing Qian, et al.，International Journal of Hydrogen Energy，2018年，Vol.43，PP.2160-2170 |
| 石灰洋一，表面技術，2004年，Vol.55 No.5，PP.328-330 |
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