JP2016203031A - Photocatalyst and production method thereof - Google Patents
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- JP2016203031A JP2016203031A JP2015083341A JP2015083341A JP2016203031A JP 2016203031 A JP2016203031 A JP 2016203031A JP 2015083341 A JP2015083341 A JP 2015083341A JP 2015083341 A JP2015083341 A JP 2015083341A JP 2016203031 A JP2016203031 A JP 2016203031A
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- 239000011941 photocatalyst Substances 0.000 title claims abstract description 71
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 239000004065 semiconductor Substances 0.000 claims abstract description 106
- 230000003287 optical effect Effects 0.000 claims abstract description 96
- 229910005855 NiOx Inorganic materials 0.000 claims abstract description 77
- 229910002451 CoOx Inorganic materials 0.000 claims abstract description 66
- 229910052715 tantalum Inorganic materials 0.000 claims abstract description 24
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 21
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 46
- 125000004430 oxygen atom Chemical group O* 0.000 claims description 12
- 229910052759 nickel Inorganic materials 0.000 claims description 11
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical group [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 10
- 239000011258 core-shell material Substances 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 150000002815 nickel Chemical group 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 33
- 230000000694 effects Effects 0.000 abstract description 23
- 229910000510 noble metal Inorganic materials 0.000 abstract description 17
- 239000000463 material Substances 0.000 abstract description 5
- 238000000354 decomposition reaction Methods 0.000 abstract description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 30
- 238000000034 method Methods 0.000 description 19
- 150000001875 compounds Chemical class 0.000 description 17
- 229910021529 ammonia Inorganic materials 0.000 description 15
- 238000010438 heat treatment Methods 0.000 description 14
- 150000004767 nitrides Chemical class 0.000 description 11
- 239000002245 particle Substances 0.000 description 11
- 239000007864 aqueous solution Substances 0.000 description 10
- 239000002904 solvent Substances 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 9
- 239000002184 metal Substances 0.000 description 9
- 150000003839 salts Chemical class 0.000 description 9
- 125000004429 atom Chemical group 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 230000009467 reduction Effects 0.000 description 8
- -1 NiS Chemical class 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 7
- 229910052739 hydrogen Inorganic materials 0.000 description 7
- 239000001257 hydrogen Substances 0.000 description 7
- 239000004570 mortar (masonry) Substances 0.000 description 7
- 238000002360 preparation method Methods 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 6
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 6
- 229910001981 cobalt nitrate Inorganic materials 0.000 description 6
- 239000002131 composite material Substances 0.000 description 6
- 230000004907 flux Effects 0.000 description 6
- 239000011521 glass Substances 0.000 description 6
- 229910044991 metal oxide Inorganic materials 0.000 description 6
- 150000004706 metal oxides Chemical class 0.000 description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 5
- 238000002441 X-ray diffraction Methods 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 150000001728 carbonyl compounds Chemical class 0.000 description 4
- 230000003197 catalytic effect Effects 0.000 description 4
- 239000003426 co-catalyst Substances 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 4
- 230000001699 photocatalysis Effects 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 229910020599 Co 3 O 4 Inorganic materials 0.000 description 3
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 3
- 229910021193 La 2 O 3 Inorganic materials 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 229910002651 NO3 Inorganic materials 0.000 description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 3
- 229910010413 TiO 2 Inorganic materials 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 239000011780 sodium chloride Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- POILWHVDKZOXJZ-ARJAWSKDSA-M (z)-4-oxopent-2-en-2-olate Chemical class C\C([O-])=C\C(C)=O POILWHVDKZOXJZ-ARJAWSKDSA-M 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- 229910003266 NiCo Inorganic materials 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000004075 alteration Effects 0.000 description 2
- 229910000428 cobalt oxide Inorganic materials 0.000 description 2
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 239000008151 electrolyte solution Substances 0.000 description 2
- 230000001747 exhibiting effect Effects 0.000 description 2
- 150000004820 halides Chemical class 0.000 description 2
- 229910052736 halogen Inorganic materials 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000001678 irradiating effect Effects 0.000 description 2
- 229910000480 nickel oxide Inorganic materials 0.000 description 2
- 238000005121 nitriding Methods 0.000 description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 235000021317 phosphate Nutrition 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 239000005361 soda-lime glass Substances 0.000 description 2
- 238000010532 solid phase synthesis reaction Methods 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 238000000859 sublimation Methods 0.000 description 2
- 230000008022 sublimation Effects 0.000 description 2
- 150000003871 sulfonates Chemical class 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- RZVAJINKPMORJF-UHFFFAOYSA-N Acetaminophen Chemical compound CC(=O)NC1=CC=C(O)C=C1 RZVAJINKPMORJF-UHFFFAOYSA-N 0.000 description 1
- BTBUEUYNUDRHOZ-UHFFFAOYSA-N Borate Chemical compound [O-]B([O-])[O-] BTBUEUYNUDRHOZ-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 241000282341 Mustela putorius furo Species 0.000 description 1
- NIPNSKYNPDTRPC-UHFFFAOYSA-N N-[2-oxo-2-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)ethyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 NIPNSKYNPDTRPC-UHFFFAOYSA-N 0.000 description 1
- 229910021607 Silver chloride Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 150000001642 boronic acid derivatives Chemical class 0.000 description 1
- 230000005587 bubbling Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 150000007942 carboxylates Chemical class 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 150000004770 chalcogenides Chemical class 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- QGUAJWGNOXCYJF-UHFFFAOYSA-N cobalt dinitrate hexahydrate Chemical compound O.O.O.O.O.O.[Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O QGUAJWGNOXCYJF-UHFFFAOYSA-N 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 238000007716 flux method Methods 0.000 description 1
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- 238000000227 grinding Methods 0.000 description 1
- 230000005524 hole trap Effects 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- RLBIQVVOMOPOHC-UHFFFAOYSA-N parathion-methyl Chemical compound COP(=S)(OC)OC1=CC=C([N+]([O-])=O)C=C1 RLBIQVVOMOPOHC-UHFFFAOYSA-N 0.000 description 1
- 238000005504 petroleum refining Methods 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000005297 pyrex Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 238000000550 scanning electron microscopy energy dispersive X-ray spectroscopy Methods 0.000 description 1
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
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- 238000004506 ultrasonic cleaning Methods 0.000 description 1
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Abstract
Description
本発明は、太陽光を利用した水分解反応を行うことにより水素および／または酸素を製造可能な光水分解反応に特に好適に用いられる光触媒およびその製造方法に関する。 The present invention relates to a photocatalyst that is particularly preferably used in a photowater splitting reaction that can produce hydrogen and / or oxygen by performing a water splitting reaction using sunlight.
太陽エネルギーなどの再生可能エネルギーを利用した高性能な光エネルギー変換システムを実用化することは、地球温暖化の抑制、および枯渇しつつある化石資源依存からの脱却を目指す観点から、近年になって急激にその重要性が増している。中でも、太陽エネルギーを用いて水を分解し水素を製造する技術は、現行の石油精製、アンモニア、メタノールの原料供給技術としてのみならず、燃料電池をベースとした来たる水素エネルギー社会において、必須とされる技術である。 In recent years, the practical application of high-performance light energy conversion systems that use renewable energy such as solar energy has been aimed at controlling global warming and moving away from the depletion of fossil resources. Its importance is increasing rapidly. Above all, the technology that decomposes water using solar energy to produce hydrogen is indispensable not only in the current petroleum refining, ammonia and methanol raw material supply technology, but also in the future hydrogen energy society based on fuel cells. Technology.
例えば、光触媒を用いることで、太陽エネルギーを利用して水を分解し、効率的に水素や酸素を製造することができる（非特許文献１等）。有望な光触媒の一つとしては、可視光応答型の水分解用光触媒であるＴｉやＮｂを含む光半導体が挙げられる。 For example, by using a photocatalyst, water can be decomposed using solar energy, and hydrogen and oxygen can be produced efficiently (Non-Patent Document 1, etc.). One promising photocatalyst is an optical semiconductor containing Ti or Nb, which is a visible light responsive water splitting photocatalyst.
このような光半導体は、単独では水分解活性が小さいため、通常、助触媒を担持して使用される。助触媒としては、高活性であり且つ安定である理由から、通常、ＩｒＯ２、ＲｕＯ２、Ｐｔなどの貴金属触媒が使用される。
しかしながら、地表埋蔵量が極めて少なく高価な貴金属を使用することは好ましくない。 また、貴金属助触媒を用いたとしても、必ずしも水分解活性が十分であるとは言えない。
Since such an optical semiconductor alone has a small water splitting activity, it is usually used by supporting a promoter. As the cocatalyst, a noble metal catalyst such as IrO 2 , RuO 2 , or Pt is usually used because it is highly active and stable.
However, it is not preferable to use an expensive noble metal with a very small surface reserve. Moreover, even if a noble metal promoter is used, it cannot be said that the water splitting activity is sufficient.
一方、非貴金属助触媒としては、例えば酸素発生用助触媒としてＣｏ３Ｏ４、ＭｎＯｘ、ＮｉＯｘ、ＮｉＣｏ２Ｏ４等が比較的高活性であることが知られている（非特許文献２、３等）。
しかしながら、非貴金属助触媒は貴金属助触媒に比べると活性が劣る。そのため、貴金属助触媒と同等以上の水分解活性を示すような非貴金属助触媒が求められている。
他方、本発明者らは、金属元素Ｍを含む化合物を光半導体に担持させた後、当該金属元素Ｍを含む化合物を還元処理して金属Ｍおよび金属酸化物ＭＯｘとすることで、高活性な光触媒を得ることに成功した（特許文献１参照）。
しかし、この光触媒は、活性は得られるものの、耐久性には未だ課題が残されている。また、アンモニアを過剰に使用するため、光触媒の過剰還元の恐れがあり、またコアシェル成分比を制御するのが難しく、大量合成には適さないという課題があった。
On the other hand, as non-noble metal promoters, for example, Co 3 O 4 , MnO x , NiO x , NiCo 2 O 4 and the like as oxygen promoters are known to have relatively high activity (Non-patent Document 2). 3 etc.).
However, non-noble metal promoters are less active than noble metal promoters. Therefore, a non-noble metal promoter that exhibits a water splitting activity equal to or higher than that of the noble metal promoter is required.
On the other hand, the present inventors, after supporting a compound containing the metal element M on the optical semiconductor, reducing the compound containing the metal element M into the metal M and the metal oxide MO x , thereby increasing the activity. A successful photocatalyst (see Patent Document 1).
However, although this photocatalyst is active, there are still problems in durability. In addition, since ammonia is used in excess, there is a risk of excessive reduction of the photocatalyst, and it is difficult to control the core-shell component ratio, and there is a problem that it is not suitable for mass synthesis.
そこで本発明は、資源が豊富で比較的安価な材料より製造される光触媒用助触媒を有するとともに、貴金属助触媒を担持した場合と同等以上の水分解活性を示しつつも、耐久性に優れた光触媒およびその製造方法を提供することを課題とする。 Therefore, the present invention has a photocatalyst cocatalyst manufactured from a resource-rich and relatively inexpensive material, and has excellent durability while exhibiting water splitting activity equivalent to or higher than that of a noble metal cocatalyst supported. It is an object to provide a photocatalyst and a method for producing the same.
本発明者らは、上記の課題を解決すべく鋭意検討した結果、以下の知見を得た。
（１）Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体に非貴金属助触媒であるＮｉＯｘとＣｏＯｘとを混在させて担持した場合、ＣｏＯｘを単独で担持した場合と比較して、活性が向上する場合がある。その活性は、貴金属助触媒を担持した場合と同等以上である。
（２）特に、Ｔｉ、Ｔａおよび／またはＮｂを含む光半導体に、ＮｉＯｘを担持させた後、ＣｏＯｘを担持させた場合、極めて高活性で耐久性の高い光触媒を得ることができる。
As a result of intensive studies to solve the above problems, the present inventors have obtained the following knowledge.
(1) The activity is improved when NiOx and CoOx, which are non-noble metal promoters, are mixed and supported on an optical semiconductor containing Ti, Ta, and / or Nb, compared to the case where CoOx is supported alone. There is a case. Its activity is equal to or greater than that when a noble metal promoter is supported.
(2) In particular, when NiOx is supported on an optical semiconductor containing Ti, Ta and / or Nb and then CoOx is supported, a photocatalyst having extremely high activity and high durability can be obtained.
本発明は上記の知見に基づいてなされたものである。すなわち、
第１の本発明は、Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体に、ＮｉＯｘおよびＣｏＯｘを助触媒として担持したことを特徴とする光触媒である。
The present invention has been made based on the above findings. That is,
A first aspect of the present invention is a photocatalyst characterized in that NiOx and CoOx are supported as a cocatalyst on a photosemiconductor containing Ti, Ta, and / or Nb.
本発明において、「Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体」とは、当該元素を含む酸化物、酸窒化物、窒化物、（オキシ）カルコゲナイド等、光触媒として用いられる光半導体を意味する。中でも酸窒化物または窒化物が好ましく、酸窒化物がより好ましい。「光半導体」の形態としては、助触媒を担持し得るような形態であればよく、粒子状、塊状等種々の形態が採用できる。「ＮｉＯｘおよびＣｏＯｘを助触媒として担持した」とは、ニッケル酸化物とコバルト酸化物とが別々に担持した形態の他、ニッケルとコバルトとの複合酸化物を担持した形態をも含む概念である。 In the present invention, “an optical semiconductor containing Ti, Ta, and / or Nb” means an optical semiconductor used as a photocatalyst, such as an oxide, oxynitride, nitride, (oxy) chalcogenide, or the like containing the element. . Of these, oxynitrides or nitrides are preferable, and oxynitrides are more preferable. The form of the “photosemiconductor” may be any form that can support a cocatalyst, and various forms such as a particulate form and a massive form can be adopted. “Supporting NiOx and CoOx as a co-catalyst” is a concept including a form in which a nickel oxide and a cobalt oxide are separately supported, as well as a form in which a composite oxide of nickel and cobalt is supported.
第１の本発明において、光半導体が、ＬａＴｉＯ２Ｎ、ＣａＮｂＯ２Ｎ、ＢａＮｂＯ２Ｎ、ＳｒＮｂＯ２Ｎ、ＬａＮｂＯ２Ｎ、Ｔａ３Ｎ５、およびＢａＴａＯ２Ｎから選ばれる少なくとも１種であることが好ましい。これら光半導体を用いた場合に、ＮｉＯｘおよびＣｏＯｘを助触媒とした場合の触媒活性向上効果が一層顕著となるためである。 In the first invention, the optical semiconductor is at least one selected from LaTiO 2 N, CaNbO 2 N, BaNbO 2 N, SrNbO 2 N, LaNbO 2 N, Ta 3 N 5 , and BaTaO 2 N. preferable. This is because when these optical semiconductors are used, the catalytic activity improvement effect when NiOx and CoOx are used as promoters becomes more remarkable.
第１の本発明において、助触媒が、ＮｉＯｘとＣｏＯｘとのコアシェル型構造を有することが好ましい。このような構造とすると、結果的に触媒活性向上効果が一層顕著となる。 In the first aspect of the present invention, the promoter preferably has a core-shell structure of NiOx and CoOx. With such a structure, as a result, the effect of improving the catalytic activity becomes more remarkable.
第１の本発明において、助触媒を構成する酸素原子、窒素原子、およびコバルト原子の窒素原子またはコバルト原子に対する酸素原子の存在比（Ｏ／ＮｉまたはＯ／Ｃｏ）が、１より大きいことが好ましい。このように酸素原子が比率を大きくすることにより、各界面での電荷の移動がスムーズになり活性が向上する。 In the first aspect of the present invention, it is preferable that the oxygen atom, nitrogen atom, and cobalt atom constituting the cocatalyst have an abundance ratio of oxygen atom to nitrogen atom or cobalt atom (O / Ni or O / Co) is greater than 1. . By increasing the ratio of oxygen atoms in this manner, the movement of charges at each interface becomes smooth and the activity is improved.
第２の本発明は、Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体に、ＮｉＯｘおよびＣｏＯｘを助触媒として担持してなる光触媒の製造方法であって、Ｔｉ、Ｔａおよび／またはＮｂを含む光半導体に、ＮｉＯｘを担持させる第１の工程と、前記光半導体および／または前記ＮｉＯｘ上にＣｏＯｘを担持させる第２の工程と、を含むことを特徴とする光触媒の製造方法である。 A second aspect of the present invention is a method for producing a photocatalyst obtained by supporting NiOx and CoOx as a cocatalyst on an optical semiconductor containing Ti, Ta, and / or Nb, wherein the light contains Ti, Ta, and / or Nb. A method for producing a photocatalyst comprising a first step of supporting NiOx on a semiconductor and a second step of supporting CoOx on the optical semiconductor and / or NiOx.
第２の本発明において、光半導体が、ＬａＴｉＯ２Ｎ、ＣａＮｂＯ２Ｎ、ＢａＮｂＯ２Ｎ、ＳｒＮｂＯ２Ｎ、ＬａＮｂＯ２Ｎ、Ｔａ３Ｎ５、およびＢａＴａＯ２Ｎから選ばれる少なくとも１種であることが好ましい。 In the second present invention, the optical semiconductor is at least one selected from LaTiO 2 N, CaNbO 2 N, BaNbO 2 N, SrNbO 2 N, LaNbO 2 N, Ta 3 N 5 , and BaTaO 2 N. preferable.
第２の本発明において、第１の工程の後に第２の工程を行うことが好ましい。 In the second aspect of the present invention, it is preferable to perform the second step after the first step.
第１の本発明においては、Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体に、ＮｉＯｘおよびＣｏＯｘを助触媒として担持したことにより、貴金属を助触媒として担持した場合と同等以上の水分解活性を示すとともに、耐久性に優れた光触媒とすることができる。このような光触媒は、例えば第２の本発明に係る光触媒の製造方法により、複雑な工程を要さずに適切に製造することができる。すなわち、本発明によれば、資源が豊富で比較的安価な材料より製造される光触媒用助触媒を有するとともに、貴金属助触媒を担持した場合と同等以上の水分解活性を示すとともに、さらに耐久性を有する光触媒およびその製造方法を提供することができる。 In the first aspect of the present invention, NiOx and CoOx are supported on the optical semiconductor containing Ti, Ta, and / or Nb as a cocatalyst, so that the water splitting activity is equal to or higher than the case where noble metal is supported as a cocatalyst. It can be set as the photocatalyst excellent in durability while showing. Such a photocatalyst can be appropriately manufactured without requiring a complicated process by, for example, the photocatalyst manufacturing method according to the second aspect of the present invention. That is, according to the present invention, it has a cocatalyst for a photocatalyst produced from a resource-rich and relatively inexpensive material, exhibits a water splitting activity equivalent to or higher than that of a noble metal cocatalyst supported, and is further durable. It is possible to provide a photocatalyst having the following and a method for producing the same.
１．光触媒
本発明に係る光触媒は、Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体に、ＮｉＯｘおよびＣｏＯｘを助触媒として担持したことに特徴を有する。
1. Photocatalyst The photocatalyst according to the present invention is characterized in that NiOx and CoOx are supported as a cocatalyst on an optical semiconductor containing Ti, Ta, and / or Nb.
１．１．光半導体
Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体としては、光触媒として機能し得る光半導体であれば特に限定されるものではなく、例えば、希土類金属および／またはアルカリ土類金属とＴｉ、Ｔａ、および／またはＮｂとの複合光半導体等が挙げられる。より具体的にはＬａＴｉＯ２Ｎ、ＳｒＴａＯ２Ｎ，ＬａＴａＯＮ２，ＣａＮｂＯ２Ｎ、ＢａＮｂＯ２Ｎ、ＳｒＮｂＯ２Ｎ、ＬａＮｂＯ２Ｎ、ＢａＴａＯ２Ｎ等の酸窒化物やＴａ３Ｎ５等の窒化物が挙げられる。この中でも、酸窒化物が好ましく、ＬａＴｉＯ２Ｎ、ＳｒＮｂＯ２Ｎ、ＣａＮｂＯ２Ｎのいずれか１つ以上がより好ましく、ＬａＴｉＯ２Ｎが特に好ましい。本発明による水分解活性向上効果が特に顕著となるためである。
1.1. Optical semiconductor The optical semiconductor containing Ti, Ta, and / or Nb is not particularly limited as long as it is an optical semiconductor that can function as a photocatalyst. For example, rare earth metal and / or alkaline earth metal and Ti, Ta , And / or a composite optical semiconductor with Nb. More specifically, oxynitrides such as LaTiO 2 N, SrTaO 2 N, LaTaON 2 , CaNbO 2 N, BaNbO 2 N, SrNbO 2 N, LaNbO 2 N, BaTaO 2 N, and nitrides such as Ta 3 N 5 are used. Can be mentioned. Among these, oxynitrides are preferable, and at least one of LaTiO 2 N, SrNbO 2 N, and CaNbO 2 N is more preferable, and LaTiO 2 N is particularly preferable. This is because the effect of improving water splitting activity according to the present invention is particularly remarkable.
本発明において、Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体は、公知の方法により容易に得ることができる。例えば、固相法やゾル・ゲル法、錯体重合法、フラックス法等の複合酸化物を得るための公知の方法によりＴｉ、Ｔａ、および／またはＮｂを含む複合酸化物を得て、当該複合酸化物に対して、アンモニア雰囲気で高温処理すること等の窒化処理を施すことにより、Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体を得ることができる。 In the present invention, an optical semiconductor containing Ti, Ta, and / or Nb can be easily obtained by a known method. For example, a composite oxide containing Ti, Ta, and / or Nb is obtained by a known method for obtaining a composite oxide such as a solid phase method, a sol-gel method, a complex polymerization method, a flux method, and the composite oxidation. An optical semiconductor containing Ti, Ta, and / or Nb can be obtained by subjecting a material to nitriding treatment such as high-temperature treatment in an ammonia atmosphere.
光半導体の形態（形状）については、以下に説明する助触媒を担持して光触媒として機能し得るような形態であれば特に限定されるものではなく、光触媒の設置形態等に合わせて、粒子状、塊状、板状等を適宜選択すればよい。特に、水分解反応用光触媒とする場合は、粒子状の光半導体の表面に助触媒を担持することが好ましい。この場合、粒子径の下限が好ましくは５０ｎｍ以上であり、上限が好ましくは５００μｍ以下である。尚、本願において「粒子径」とは、定方向接線径（フェレ径）の平均値（平均粒子径）を意味し、ＸＲＤ、ＴＥＭ、ＳＥＭ法等の公知の手段によって測定することができる。 The form (shape) of the photo semiconductor is not particularly limited as long as it is a form capable of supporting a cocatalyst described below and functioning as a photocatalyst. A lump shape, a plate shape, or the like may be appropriately selected. In particular, when a photocatalyst for water splitting reaction is used, it is preferable to support a promoter on the surface of a particulate optical semiconductor. In this case, the lower limit of the particle diameter is preferably 50 nm or more, and the upper limit is preferably 500 μm or less. In the present application, the “particle diameter” means an average value (average particle diameter) of tangential diameters (ferret diameters) in a fixed direction and can be measured by a known means such as XRD, TEM, SEM method.
１．２．助触媒
本発明においては上記したような光半導体に、ＮｉＯｘ及びＣｏＯｘで表される金属酸化物が助触媒として担持されている。ＮｉＯｘは、ＮｉＯ、ＮｉＯ２等の少なくとも一種を含み、ＣｏＯｘはＣｏＯ、Ｃｏ２Ｏ３、Ｃｏ３Ｏ４等の少なくとも一種を含み、これらの混合物のほか、ＮｉＣｏ２Ｏ４、ＣｏＮｉＯｘ、ＮｉＣｅＯｘ、ＮｉＣｕＯｘ、ＮｉＬａＯｘ等の複合酸化物、またはその混合物であってもよい。
1.2. Cocatalyst In the present invention, a metal oxide represented by NiOx and CoOx is supported on the optical semiconductor as described above as a cocatalyst. NiOx includes at least one of NiO, NiO 2 and the like, and CoOx includes at least one of CoO, Co 2 O 3 , Co 3 O 4 and the like, in addition to a mixture thereof, NiCo 2 O 4 , CoNiOx, NiCeOx, NiCuOx. Or a complex oxide such as NiLaOx, or a mixture thereof.
なお、本発明においては、助触媒として上記のＮｉＯｘとＣｏＯｘのほか、Ｉｎ、Ｆｅ、Ｍｎを含む金属酸化物などの助触媒が担持されていてもよい。例えば、ＮｉＳ、ＭｏＳ２、ＮｉＭｏＳ等の硫化物が挙げられる。 In the present invention, in addition to the above-mentioned NiOx and CoOx, a promoter such as a metal oxide containing In, Fe, or Mn may be supported as a promoter. For example, sulfides such as NiS, MoS 2 and NiMoS can be used.
本発明においては、従来において助触媒としての活性が十分ではないと考えられていた金属であっても、所定の光半導体に、金属酸化物と金属との双方が助触媒として担持された光触媒とすることで、助触媒として貴金属が担持された光触媒と同等以上の水分解活性を得ることができる。 In the present invention, a photocatalyst in which both a metal oxide and a metal are supported as a cocatalyst on a predetermined photo-semiconductor, even if it is a metal that has been conventionally considered to have insufficient activity as a cocatalyst, By doing so, it is possible to obtain a water splitting activity equal to or higher than that of a photocatalyst carrying a noble metal as a promoter.
本発明において、助触媒はＮｉＯｘとＣｏＯｘとのコアシェル型構造となっていることが好ましい。この場合、通常、ＮｉＯｘがコア部、ＣｏＯｘがシェル部を構成する。例えば、図１に示すように、光半導体であるＬａＴｉＯ２Ｎの表面に、ＮｉＯｘおよびＣｏＯｘのコアシェル型構造を有する助触媒が担持された形態が挙げられる。このような光半導体にコアシェル型構造を有する助触媒が担持された光触媒の製造方法については後述する。 In the present invention, the cocatalyst preferably has a core-shell structure of NiOx and CoOx. In this case, NiOx usually constitutes the core part and CoOx constitutes the shell part. For example, as shown in FIG. 1, there is a form in which a promoter having a core-shell structure of NiO x and CoOx is supported on the surface of LaTiO 2 N that is an optical semiconductor. A method for producing a photocatalyst in which a cocatalyst having a core-shell structure is supported on such an optical semiconductor will be described later.
光半導体への助触媒の担持方法については、特に限定されるものではなく、公知の担持方法をいずれも適用することができる。例えば、助触媒となる金属源（Ｎｉを含む化合物）を含有する溶液やコロイド溶液に光半導体の粉体や成形体を浸漬し、蒸発乾固する方法、または金属Ｎｉのカルボニル化合物を昇華によって光半導体表面へ吸着させ、これを熱分解させる方法などによって、光半導体の表面に助触媒を担持することができる。また、文献（ＰＮＡＳ ｖｏｌ．１０６，２０６３３−２０６３６（２００９））に記載されている、助触媒となるＮｉイオンを含有する溶液に、光半導体の粉体や成型体を浸漬し、光照射する方法により担持してもよい。 The method for supporting the cocatalyst on the optical semiconductor is not particularly limited, and any known supporting method can be applied. For example, a method of immersing a photo-semiconductor powder or compact in a solution or colloidal solution containing a metal source (compound containing Ni) that serves as a cocatalyst and evaporating to dryness, or sublimating a metal Ni carbonyl compound by sublimation The cocatalyst can be supported on the surface of the optical semiconductor by a method of adsorbing it on the semiconductor surface and thermally decomposing it. Further, a method of immersing a light semiconductor powder or molded body in a solution containing Ni ions as a promoter described in the literature (PNAS vol. 106, 20633-20636 (2009)) and irradiating with light. You may carry by.
助触媒の担持量については、少なすぎても効果がなく、多すぎると助触媒自身が光を吸収・散乱するなどして光半導体の光吸収を妨げたり、再結合中心として働いたりして、かえって触媒活性が低下してしまう。このような観点から、光触媒における助触媒の担持量は、特に限定はされないが、光触媒全体を基準（１００質量％）として、好ましくは０．０１質量％以上２０質量％以下であり、より好ましくは１５質量％以下、特に好ましくは１０質量％以下である。 As for the amount of cocatalyst supported, there is no effect if it is too small, and if it is too large, the cocatalyst itself absorbs and scatters light and prevents light absorption of the optical semiconductor, or acts as a recombination center. On the contrary, the catalytic activity is lowered. From such a viewpoint, the amount of the cocatalyst supported in the photocatalyst is not particularly limited, but is preferably 0.01% by mass or more and 20% by mass or less, more preferably, based on the entire photocatalyst (100% by mass). It is 15 mass% or less, Most preferably, it is 10 mass% or less.
助触媒は、上記した光半導体の表面に担持可能な程度の大きさであればよい。光半導体の表面に助触媒を担持させるためには、粒子状、塊状、板状等の光半導体よりも酸化物粒子が小さい必要がある。特に粒子径が５０ｎｍ以上５００μｍ以下の光半導体粒子の表面に、粒子径が１．０ｎｍ以上２５ｎｍ以下の助触媒を担持させる形態が好ましい。助触媒の粒子径は下限がより好ましくは１．２ｎｍ以上、さらに好ましくは１．５ｎｍ以上であり、上限がより好ましくは２０ｎｍ以下、さらに好ましくは１０ｎｍ以下である。助触媒の粒子径をこのような範囲に調整することで、光触媒活性を一層向上可能な助触媒とすることができる。 The promoter may be any size that can be supported on the surface of the optical semiconductor. In order to support the cocatalyst on the surface of the optical semiconductor, it is necessary that the oxide particles are smaller than the optical semiconductor such as particles, lumps, and plates. Particularly preferred is a mode in which a cocatalyst having a particle size of 1.0 nm to 25 nm is supported on the surface of an optical semiconductor particle having a particle size of 50 nm to 500 μm. The lower limit of the particle diameter of the cocatalyst is more preferably 1.2 nm or more, still more preferably 1.5 nm or more, and the upper limit is more preferably 20 nm or less, still more preferably 10 nm or less. By adjusting the particle diameter of the promoter to such a range, a promoter capable of further improving the photocatalytic activity can be obtained.
また担持されるＮｉＯｘとＣｏＯｘの酸素原子、ニッケル原子、およびコバルト原子の存在比率は特に限定されないが、電荷移動の観点から酸素原子が大きい方が好ましい。好ましくはニッケル原子またはコバルト原子に対する酸素原子の存在が、１より大きく、より好ましくはニッケル原子に対する酸素原子の存在比が１．１以上、さらに好ましくは１．２以上、最も好ましくは１．３以上であり、コバルト原子に対する酸素原子の存在比が１．０以上、さらに好ましくは１．１以上、最も好ましくは１．２以上である。 Further, the abundance ratio of oxygen atoms, nickel atoms, and cobalt atoms of NiOx and CoOx to be supported is not particularly limited, but a larger oxygen atom is preferable from the viewpoint of charge transfer. Preferably the presence of oxygen atoms relative to nickel or cobalt atoms is greater than 1, more preferably the abundance ratio of oxygen atoms relative to nickel atoms is 1.1 or higher, more preferably 1.2 or higher, most preferably 1.3 or higher. The abundance ratio of oxygen atoms to cobalt atoms is 1.0 or more, more preferably 1.1 or more, and most preferably 1.2 or more.
本発明に係る光触媒を実際に水の分解に使用する場合において、光触媒の形態については特に限定されるものではなく、水中に光触媒粒子を分散・懸濁させる形態であってもよいし、光触媒粒子を固めて成形体として、当該成形体を水中に設置する形態或いは基材上に光触媒層を設けて積層体とし、当該積層体を水中に設置する形態等であってもよい。 In the case where the photocatalyst according to the present invention is actually used for water decomposition, the form of the photocatalyst is not particularly limited, and may be a form in which the photocatalyst particles are dispersed and suspended in water. The molded body may be in a form in which the molded body is placed in water or in a form in which a photocatalyst layer is provided on a substrate to form a laminated body, and the laminated body is placed in water.
２．光触媒の製造方法
本発明に係る光触媒の製造方法は、Ｔｉ、Ｔａ、および／またはＮｂを含む光半導体に、ＮｉＯｘおよびＣｏＯｘを助触媒として担持させてなる光触媒の製造方法であって、Ｔｉ、Ｔａおよび／またはＮｂを含む光半導体に、ＮｉＯｘを担持させる第１の工程と、前記光半導体および／または前記ＮｉＯｘ上にＣｏＯｘを担持させる第２の工程と、を含むことを特徴とする。
2. Photocatalyst Manufacturing Method A photocatalyst manufacturing method according to the present invention is a photocatalyst manufacturing method in which NiOx and CoOx are supported as a cocatalyst on an optical semiconductor containing Ti, Ta, and / or Nb. And / or an optical semiconductor containing Nb includes a first step of supporting NiOx, and a second step of supporting CoOx on the optical semiconductor and / or NiOx.
第１の工程は、Ｔｉ、Ｔａおよび／またはＮｂを含む光半導体に、ＮｉＯｘを担持させる工程である。 The first step is a step of supporting NiOx on an optical semiconductor containing Ti, Ta and / or Nb.
ここで、本発明においては、光半導体にＮｉ源を接触・担持させた後で、適当な処理を施すことによってＮｉＯｘとすることができる。本発明におけるＮｉ源は、ＮｉＯｘのような酸化物のほか、硝酸塩、硫酸塩、炭酸塩、リン酸塩、ヘキサフルオロリン酸塩、ホウ酸塩、テトラフルオロホウ酸塩、ハロゲンオキソ酸塩、カルボン酸塩、スルホン酸塩等のＮｉ元素を含む塩；アセチルアセトナート、カルボニル化合物等のＮｉ元素を含む錯体化合物；Ｎｉのハロゲン化物もしくはアンモニアが配位されたＮｉ錯体；金属Ｎｉの表面が酸化されＮｉＯｘの表面皮膜がついたもの等が挙げられる。このうちＮｉＯｘで表される金属酸化物、またはＮｉ元素を含む塩が好ましい。Ｎｉ元素を含む塩としては、溶解性、製造性の面で硝酸塩が好ましい。 Here, in the present invention, NiOx can be obtained by applying an appropriate treatment after contacting and supporting the Ni source on the optical semiconductor. In addition to oxides such as NiOx, the Ni source in the present invention is nitrate, sulfate, carbonate, phosphate, hexafluorophosphate, borate, tetrafluoroborate, halogen oxoacid salt, carboxyl Salts containing Ni elements such as acid salts and sulfonates; complex compounds containing Ni elements such as acetylacetonate and carbonyl compounds; Ni complexes coordinated with halides or ammonia of Ni; the surface of metal Ni is oxidized Examples include those with a NiOx surface coating. Among these, a metal oxide represented by NiOx or a salt containing Ni element is preferable. As the salt containing Ni element, nitrate is preferable in terms of solubility and manufacturability.
光半導体とＮｉＯｘとの形態については、上記したものと同様である。光半導体へのＮｉＯｘの担持方法も上述した通りであり特に限定されるものではない。例えば、助触媒の元となるＮｉ源を含む水溶液に、光半導体粉体を浸漬・懸濁させ、溶媒を蒸発乾固する方法、Ｎｉのカルボニル化合物を昇華によって光半導体表面へ吸着させ、これを熱分解させる方法などによって、光半導体の表面にＮｉを含む化合物を担持することができる。また助触媒となるＮｉ源のイオンを含有する溶液に光半導体の粉体や成型体を浸漬し、光照射することにより担持してもよい。 The forms of the optical semiconductor and NiOx are the same as those described above. The method of supporting NiOx on the optical semiconductor is also as described above and is not particularly limited. For example, a method of immersing and suspending a photo semiconductor powder in an aqueous solution containing a Ni source as a promoter, evaporating and drying the solvent, adsorbing a carbonyl compound of Ni on the surface of the photo semiconductor by sublimation, A compound containing Ni can be supported on the surface of the optical semiconductor by a thermal decomposition method or the like. Alternatively, it may be supported by immersing a photo-semiconductor powder or molded body in a solution containing ions of the Ni source serving as a promoter and irradiating with light.
これらＮｉ源やＮｉを含む化合物を担持した後、焼成処理をする工程を含んでいてもよい。具体的にはＮｉ源やＮｉを含む化合物として、溶解性が高い塩等の、均一性の高い溶液が得られるものを用いて光半導体に担持したのち、焼成処理を行う。助触媒を均一に担持できる点、塩化物イオン等の、後述する還元処理に際して残留が好ましくない成分の除去に有効である点で好ましい製造方法として挙げられる。 A step of carrying out a firing treatment after supporting these Ni source and Ni-containing compound may be included. Specifically, as a Ni source or a Ni-containing compound, a compound having a highly uniform solution such as a highly soluble salt is supported on the optical semiconductor, and then subjected to a firing treatment. It is mentioned as a preferable production method in that the cocatalyst can be uniformly supported, and it is effective in removing components such as chloride ions which are not preferably retained in the reduction treatment described later.
光半導体上に担持されたＮｉ源やＮｉを含む化合物は、適当な雰囲気下において加熱処理等を行うことによって容易にＮｉＯｘとすることができる。特に、光半導体の変質（酸化や過剰な還元）を抑えるため、アンモニア、水素、アルゴン、窒素のいずれかを含む気流下で加熱処理を行うことが好ましい。加熱処理の温度については、好ましくは １００℃以上、より好ましくは１５０℃以上とし、好ましくは７００℃以下、より好ましくは６００℃以下とする。加熱処理の時間については特に限定されるものではないが、好ましくは１０分以上、より好ましくは３０分以上とし、好ましくは５時間以下、より好ましくは ４時間以下とする。ここで、Ｎｉ源やＮｉを含む化合物を加熱処理によりＮｉＯｘとする場合、当該加熱処理は、後述する第２の工程の前の他、第２の工程と同時に行ってもよい。特に、第２の工程の前に行うことが好ましい。 The Ni source or Ni-containing compound carried on the optical semiconductor can be easily converted to NiOx by performing a heat treatment or the like in an appropriate atmosphere. In particular, in order to suppress alteration (oxidation or excessive reduction) of the optical semiconductor, it is preferable to perform heat treatment under an air stream containing any of ammonia, hydrogen, argon, and nitrogen. The temperature of the heat treatment is preferably 100 ° C. or higher, more preferably 150 ° C. or higher, preferably 700 ° C. or lower, more preferably 600 ° C. or lower. The time for the heat treatment is not particularly limited, but is preferably 10 minutes or more, more preferably 30 minutes or more, preferably 5 hours or less, more preferably 4 hours or less. Here, when the Ni source or the Ni-containing compound is converted to NiOx by heat treatment, the heat treatment may be performed simultaneously with the second step in addition to the second step described later. In particular, it is preferable to carry out before the second step.
第２の工程は、光半導体および／またはＮｉＯｘ上にＣｏＯｘを担持させる工程である。特に、ＮｉＯｘを担持させた後に、ＣｏＯｘを担持させる工程とすることが好ましい。本発明者らが鋭意研究したところ、所定の光半導体表面に、助触媒としてまずＮｉＯｘを担持させ、その後、ＣｏＯｘを担持させることにより、光触媒活性が著しく向上することを知見した。この現象は電荷移動の促進によって発現するものと推定される。これは種々の要因によるものと考えられるが、例えばその一つとして、光半導体に担持後のＮｉＯが光半導体表面と助触媒との界面に良好な接触が得られ、活性が向上したものと推測できる。または、ＮｉＯｘと光半導体との接触界面が増大し、触媒活性が向上したものと推測することができる。また耐久性の向上に関しては、ＮｉＯｘがホールトラップとして機能することにより、光触媒の劣化を抑制できるためであると推測することができる。 The second step is a step of supporting CoOx on the optical semiconductor and / or NiOx. In particular, it is preferable that the step of supporting CoOx after supporting NiOx. As a result of intensive studies by the present inventors, it was found that the photocatalytic activity is remarkably improved by supporting NiOx as a co-catalyst on a predetermined optical semiconductor surface and then supporting CoOx. This phenomenon is presumed to occur due to the promotion of charge transfer. This is considered to be due to various factors. For example, it is assumed that NiO after being supported on the optical semiconductor has good contact with the interface between the surface of the optical semiconductor and the cocatalyst, and the activity has been improved. it can. Alternatively, it can be assumed that the contact interface between NiOx and the optical semiconductor is increased, and the catalytic activity is improved. Further, regarding the improvement in durability, it can be assumed that NiOx functions as a hole trap to suppress deterioration of the photocatalyst.
第２の工程を経ることで、光半導体の表面に助触媒であるＮｉＯｘとＣｏＯｘが担持された光触媒が得られる。本発明に係る光触媒の製造方法により得られた光触媒は、光半導体の表面において、ＮｉＯｘとＣｏＯｘとがそれぞれ担持される形態の他、ＮｉＯｘ上にＣｏＯｘが形成されるコアシェル型構造（コア：ＮｉＯｘ、シェル：ＣｏＯｘ）を有する助触媒が担持される場合がある（例えば図１参照）。このような形態の光触媒は、貴金属を助触媒として担持した場合と比較して同等以上の光触媒活性を有するため好ましい。 By passing through the second step, a photocatalyst having NiOx and CoOx as promoters supported on the surface of the optical semiconductor is obtained. The photocatalyst obtained by the method for producing a photocatalyst according to the present invention has a core-shell structure (core: NiOx, in which CoOx is formed on NiOx, in addition to a form in which NiOx and CoOx are respectively supported on the surface of the optical semiconductor. In some cases, a co-catalyst having a shell (CoOx) is supported (see, for example, FIG. 1). Such a photocatalyst is preferable because it has a photocatalytic activity equivalent to or higher than that in the case where a noble metal is supported as a promoter.
本発明においては光半導体および／またはＮｉＯｘ上にＣｏ源を接触・担持させた後で、適当な処理を施すことによってＣｏＯｘとすることができる。光触媒および／またはＮｉＯｘ上に担持されるＣｏ源としては、ＣｏＯｘのような酸化物のほか、硝酸塩、硫酸塩、炭酸塩、リン酸塩、ヘキサフルオロリン酸塩、ホウ酸塩、テトラフルオロホウ酸塩、ハロゲンオキソ酸塩、カルボン酸塩、スルホン酸塩等のＣｏ元素を含む塩；アセチルアセトナート、カルボニル化合物等のＣｏ元素を含む錯体化合物；Ｃｏのハロゲン化物、もしくはさらにアンモニアが配位した錯体；金属Ｃｏの表面が酸化されＣｏＯｘの表面皮膜がついたもの等が挙げられる。このうちＣｏＯｘで表される金属酸化物、またはＣｏ元素を含む塩が好ましい。Ｃｏ元素を含む塩としては、溶解性、製造性の面で硝酸塩が好ましい。 In the present invention, after a Co source is brought into contact with and supported on the optical semiconductor and / or NiOx, CoOx can be obtained by performing an appropriate treatment. Co sources supported on the photocatalyst and / or NiOx include oxides such as CoOx, nitrates, sulfates, carbonates, phosphates, hexafluorophosphates, borates, and tetrafluoroboric acid. Salts containing Co elements such as salts, halogen oxoacid salts, carboxylates and sulfonates; complex compounds containing Co elements such as acetylacetonate and carbonyl compounds; Co halides or complexes coordinated with ammonia A metal Co surface oxidized and a CoOx surface film. Among these, a metal oxide represented by CoOx or a salt containing a Co element is preferable. As the salt containing Co element, nitrate is preferable in terms of solubility and manufacturability.
これらＣｏ源やＣｏを含む化合物を担持した後、焼成処理をする工程を含んでいてもよい。具体的にはＣｏ源やＣｏを含む化合物として、溶解性が高い塩等の、均一性の高い溶液が得られるものを用いて光半導体に担持したのち、焼成処理を行う。助触媒を均一に担持できる点、塩化物イオン等の、後述する還元処理に際して残留が好ましくない成分の除去に有効である点で好ましい製造方法として挙げられる。 A step of performing a baking treatment after supporting the Co source or the compound containing Co may be included. Specifically, as a Co source or a Co-containing compound, a compound that provides a highly uniform solution such as a highly soluble salt is supported on an optical semiconductor, and then subjected to a firing treatment. It is mentioned as a preferable production method in that the cocatalyst can be uniformly supported, and it is effective in removing components such as chloride ions which are not preferably retained in the reduction treatment described later.
光半導体および／またはＮｉＯｘ上に担持されたＣｏ源やＣｏを含む化合物は、適当な雰囲気下において加熱処理等を行うことによって容易にＣｏＯｘとすることができる。特に、光半導体の変質（酸化や過剰な還元）を抑えるため、アンモニア、水素、アルゴンのいずれかを含む気流下で加熱処理を行うことが好ましい。加熱処理の温度については、好ましくは１００℃以上、より好ましくは１５０℃以上とし、好ましくは７００℃以下、より好ましくは６００℃以下とする。加熱処理の時間については特に限定されるものではないが、好ましくは１０分以上、より好ましくは３０分以上とし、好ましくは５時間以下、より好ましくは４時間以下とする。ここで、Ｃｏ源やＣｏを含む化合物を加熱処理によりＣｏＯｘとする場合に、同時に、上述のＮｉ源やＮｉを含む化合物をＮｉＯｘとしてもよい。 The Co source and / or the Co-containing compound supported on the optical semiconductor and / or NiOx can be easily converted to CoOx by performing a heat treatment or the like in an appropriate atmosphere. In particular, in order to suppress alteration (oxidation or excessive reduction) of the optical semiconductor, it is preferable to perform the heat treatment under an air stream containing any of ammonia, hydrogen, and argon. The temperature of the heat treatment is preferably 100 ° C. or higher, more preferably 150 ° C. or higher, preferably 700 ° C. or lower, more preferably 600 ° C. or lower. The time for the heat treatment is not particularly limited, but is preferably 10 minutes or more, more preferably 30 minutes or more, preferably 5 hours or less, more preferably 4 hours or less. Here, when the Co source or the compound containing Co is converted to CoOx by heat treatment, the Ni source or the compound containing Ni may be simultaneously used as NiOx.
以上の通り、本発明によれば、資源が豊富で比較的安価な材料より製造される光触媒用助触媒を有するとともに、貴金属助触媒を担持した場合と同等以上の水分解活性を示しつつも、耐久性に優れた光触媒およびその製造方法を提供することができる。 As described above, according to the present invention, while having a photocatalyst promoter produced from a resource-rich and relatively inexpensive material, while exhibiting a water splitting activity equivalent to or higher than that when a noble metal promoter is supported, A photocatalyst excellent in durability and a method for producing the photocatalyst can be provided.
以下、実施例により本発明をさらに具体的に説明するが、本発明は、その要旨を超えない限り、以下の実施例により制限されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not restrict | limited by a following example, unless the summary is exceeded.
＜光触媒の調製＞
（光半導体１の調製）
文献（T. Minegishi, N. Nishimura, J. Kubota and K. Domen, Chem. Sci., 2013, 4, 1120-1124.）に記載された方法に従って光半導体１（ＬａＴｉＯ２Ｎ）を調製した。具体的には以下の通りである。
まず、前駆体であるＬａ２Ｔｉ２Ｏ７は、ＮａＣｉをフラックスとして用いた固相合成により行った。Ｌａ２Ｏ３（関東化学社製、９９．９９％）、ＴｉＯ２（Ｓｉｇｍａ−Ａｌｄｒｉｃｈ社製、９９．９９％）、ＮａＣｌ（和光純薬工業社製、９９．５％）をモル比でＬａ：Ｔｉ：Ｎａ＝１：１：１０ となるように混合し、この混合物を空気中１４２３Ｋで５時間焼成した後、１０２３Ｋまで１ Ｋ／ｍｉｎで冷却し、さらに室温まで自然放冷した。冷却後、得られた沈殿物を蒸留水で洗浄し、フラックスを除去することにより、Ｌａ２Ｔｉ２Ｏ７の酸化物を得た。さらに、アンモニア気流下（２５０ｍＬ／ｍｉｎ）、１２２３Ｋで１５時間窒化することにより、光半導体１（ＬａＴｉＯ２Ｎ）を得た。得られた窒化物はx-ray diffraction pattern（ＸＲＤ）とＤＲＳで測定して同定した。
<Preparation of photocatalyst>
(Preparation of optical semiconductor 1)
An optical semiconductor 1 (LaTiO 2 N) was prepared according to the method described in the literature (T. Minegishi, N. Nishimura, J. Kubota and K. Domen, Chem. Sci., 2013, 4, 1120-1124.). Specifically, it is as follows.
First, La 2 Ti 2 O 7 as a precursor was obtained by solid phase synthesis using NaCi as a flux. La 2 O 3 (manufactured by Kanto Chemical Co., Ltd., 99.99%), TiO 2 (manufactured by Sigma-Aldrich, 99.99%), NaCl (manufactured by Wako Pure Chemical Industries, Ltd., 99.5%) at a molar ratio of La. : Ti: Na = 1: 1: 10 The mixture was calcined in air at 1423K for 5 hours, cooled to 1023K at 1 K / min, and then allowed to cool naturally to room temperature. After cooling, the resulting precipitate was washed with distilled water, and the flux was removed to obtain an oxide of La 2 Ti 2 O 7 . Furthermore, the optical semiconductor 1 (LaTiO 2 N) was obtained by nitriding at 1223 K for 15 hours under an ammonia stream (250 mL / min). The obtained nitride was identified by measuring with x-ray diffraction pattern (XRD) and DRS.
（実施例１：ＣｏＯｘ／ＮｉＯｘ／光半導体１）
得られた光半導体１（ＬａＴｉＯ２Ｎ）（０．１ｇ）に、水（０．５ｍＬ）と硝酸ニッケル（ＬａＴｉＯ２Ｎに対して２質量％のＮｉＯｘを構成する濃度）を混ぜて１分間超音波で処理した後、減圧下、溶媒を留去し乾固させた。乾固した窒化物を取り出し、乳鉢ですり潰した後、アンモニア気流下（５０ｍＬ／ｍｉｎ）、５５０℃で１時間加熱処理を行なうことによりＮｉＯｘ／ＬａＴｉＯ２Ｎを得た。さらに得られたＮｉＯｘ／ＬａＴｉＯ２Ｎ（０．１ｇ）に、水（０．５ｍＬ）と硝酸コバルト水溶液（ＬａＴｉＯ２Ｎに対して２質量％のＣｏＯｘを構成する濃度）を混ぜて１分間超音波で処理した後、減圧下、溶媒を留去し乾固させた。乾固した窒化物を取り出し乳鉢ですり潰した後、アンモニア気流下（５０ｍＬ／ｍｉｎ）、６５０℃で１時間加熱処理を行なうことによりＣｏＯｘ（２質量％）／ＮｉＯｘ（２質量％）／光半導体１（ＬａＴｉＯ２Ｎ）を得た。なお、ＮｉＯｘとは、ＮｉＯ、ＮｉＯ２等のニッケル酸化物、ＣｏＯｘとは、ＣｏＯ、Ｃｏ２Ｏ３、Ｃｏ３Ｏ４等のコバルト酸化物の混合物をそれぞれ意味する。以下同様。
光半導体１におけるＮｉ原子に対するＣｏ原子の比率は１：１であった。
Example 1: CoOx / NiOx / Optical Semiconductor 1
The obtained optical semiconductor 1 (LaTiO 2 N) (0.1 g) was mixed with water (0.5 mL) and nickel nitrate (concentration constituting 2% by mass of NiOx with respect to LaTiO 2 N) for over 1 minute. After treatment with sonic waves, the solvent was distilled off under reduced pressure to dryness. The dried nitride was taken out, ground in a mortar, and then heat treated at 550 ° C. for 1 hour under an ammonia stream (50 mL / min) to obtain NiOx / LaTiO 2 N. Further, the obtained NiOx / LaTiO 2 N (0.1 g) was mixed with water (0.5 mL) and an aqueous cobalt nitrate solution (concentration constituting 2% by mass of CoOx with respect to LaTiO 2 N) for 1 minute. Then, the solvent was distilled off under reduced pressure to dryness. The dried nitride is taken out and crushed in a mortar, and then heat-treated at 650 ° C. for 1 hour in an ammonia stream (50 mL / min) to obtain CoOx (2 mass%) / NiOx (2 mass%) / photosemiconductor 1 (LaTiO 2 N) was obtained. Note that the NiOx, NiO, nickel oxide such as NiO 2, and is CoOx, means CoO, Co 2 O 3, Co 3 O 4 and the like a mixture of cobalt oxide, respectively. The same applies below.
The ratio of Co atoms to Ni atoms in the optical semiconductor 1 was 1: 1.
（実施例２：ＣｏＯｘ／ＮｉＯｘ／光半導体１）
硝酸コバルト水溶液のＣｏ濃度を「ＬａＴｉＯ２Ｎに対して３質量％のＣｏＯｘを構成する濃度」に変更した以外は、実施例１に記載の調製方法と同様の手順で、光半導体１にＮｉＯｘおよびＣｏＯｘを担持した光触媒「ＣｏＯｘ／ＮｉＯｘ／光半導体１（ＬａＴｉＯ２Ｎ）」を得た。
光半導体１におけるＮｉ原子に対するＣｏ原子の比率は１：１．５であった。
(Example 2: CoOx / NiOx / optical semiconductor 1)
Except for changing the Co concentration of the cobalt nitrate aqueous solution to “concentration constituting 3% by mass of CoOx with respect to LaTiO 2 N”, NiOx and NiOx were added to the optical semiconductor 1 in the same procedure as the preparation method described in Example 1. A photocatalyst “CoOx / NiOx / photosemiconductor 1 (LaTiO 2 N)” supporting CoOx was obtained.
The ratio of Co atoms to Ni atoms in the optical semiconductor 1 was 1: 1.5.
（実施例３：ＣｏＯｘ／ＮｉＯｘ／光半導体１）
硝酸コバルト水溶液のＣｏ濃度を「ＬａＴｉＯ２Ｎに対して４質量％のＣｏＯｘを構成する濃度」に変更した以外は、実施例１に記載の調製方法と同様の手順で、光半導体１にＮｉＯｘおよびＣｏＯｘを担持した光触媒「ＣｏＯｘ／ＮｉＯｘ／光半導体１（ＬａＴｉＯ２Ｎ）」を得た。
光半導体１におけるＮｉ原子に対するＣｏ原子の比率は１：２であった。
(Example 3: CoOx / NiOx / Optical semiconductor 1)
Except for changing the Co concentration of the cobalt nitrate aqueous solution to “concentration constituting 4 mass% CoOx with respect to LaTiO 2 N”, NiOx and NiOx were added to the optical semiconductor 1 in the same procedure as the preparation method described in Example 1. A photocatalyst “CoOx / NiOx / photosemiconductor 1 (LaTiO 2 N)” supporting CoOx was obtained.
The ratio of Co atoms to Ni atoms in the optical semiconductor 1 was 1: 2.
（比較例１：（ＣｏＯｘ／Ｃｏ）／光半導体２）
（光半導体２の調製）
文献（Journal of Flux Grouwth,2010,5,81/J.Am.Ceram.Soc 991,74,2876）に記載の方法に従って光半導体２（ＬａＴｉＯ２Ｎ）を調製した。具体的には以下の通りである。
Ｌａ２Ｏ３（関東化学社製、９９．９９％）とＴｉＯ２（Ｓｉｇｍａ−Ａｌｄｒｉｃｈ社製、９９．９９％）とをモル比１：２でエタノールを用いて湿式混合し、これにフラックスであるＮａＣｌ（和光純薬工業社製、９９．５％）とＫＣｌ（和光純薬工業社製、９９．５％）との混合物（モル比１：１）を（Ｌａ＋Ｔｉ）：（Ｎａ＋Ｋ）＝１：２のモル比で加えた。これをアルミナ坩堝に入れ、１４２３Ｋまで１０Ｋ／ｍｉｎで加熱し、同温度で５時間保持した。その後１０２３Ｋまで１Ｋ／ｍｉｎで冷却し、さらに室温まで自然冷却した。取り出した試料を蒸留水で洗浄、濾過することによってフラックスを除去後、乾燥することで前駆体となるＬａ２Ｔｉ２Ｏ７を得た。次にこの前駆体を２００ｍＬ／ｍｉｎのＮＨ３気流下、１２２３Ｋで１５時間窒化し、光半導体２（ＬａＴｉＯ２Ｎ）を得た。ＸＲＤにより単相のＬａＴｉＯ２Ｎの生成が確認された。
得られた光半導体２（０．３ｇ）を、Ｃｏ（ＮＯ３）２・６Ｈ２Ｏ（ＬａＴｉＯ２Ｎに対して２質量％のＣｏＯｘを構成し得る濃度（ただし、後述の通り、還元処理により一部Ｃｏとなる））を含む水溶液（３ｍＬ）に懸濁し、蒸発皿内、ウォーターバス上でガラス棒により攪拌しながら溶媒を蒸発乾燥させた。
得られたＣｏ（ＮＯ３）２／光半導体２を、２００ｍＬ／ｍｉｎのＮＨ３気流下で、７７３〜１０７３Ｋで１時間還元処理した後、室温まで冷却して、光半導体２にＣｏＯｘおよびＣｏを担持した光触媒「（ＣｏＯｘ／Ｃｏ）／光半導体２（ＬａＴｉＯ２Ｎ）」を得た。
(Comparative Example 1: (CoO x / Co) / Optical Semiconductor 2)
(Preparation of optical semiconductor 2)
An optical semiconductor 2 (LaTiO 2 N) was prepared according to the method described in the literature (Journal of Flux Grouwth, 2010, 5, 81 / J. Am. Ceram. Soc 991, 74, 2876). Specifically, it is as follows.
La 2 O 3 (manufactured by Kanto Chemical Co., 99.99%) and TiO 2 (manufactured by Sigma-Aldrich, 99.99%) are wet-mixed with ethanol at a molar ratio of 1: 2, and this is mixed with flux. A mixture of a certain NaCl (manufactured by Wako Pure Chemical Industries, 99.5%) and KCl (manufactured by Wako Pure Chemical Industries, 99.5%) (molar ratio 1: 1) is (La + Ti) :( Na + K) = 1. : The molar ratio was 2. This was put into an alumina crucible, heated to 1423K at 10 K / min, and kept at the same temperature for 5 hours. Thereafter, it was cooled to 1023 K at 1 K / min, and further naturally cooled to room temperature. The sample taken out was washed with distilled water and filtered to remove the flux, followed by drying to obtain La 2 Ti 2 O 7 as a precursor. Next, this precursor was nitrided at 1223 K for 15 hours under an NH 3 stream of 200 mL / min to obtain an optical semiconductor 2 (LaTiO 2 N). XRD confirmed the formation of single-phase LaTiO 2 N.
The concentration of the obtained optical semiconductor 2 (0.3 g) that can constitute 2% by mass of CoOx with respect to Co (NO 3 ) 2 .6H 2 O (LaTiO 2 N (however, as described later, by reduction treatment) It was suspended in an aqueous solution (3 mL) containing a part of Co), and the solvent was evaporated to dryness while stirring with a glass rod in an evaporating dish on a water bath.
The obtained Co (NO 3 ) 2 / photosemiconductor 2 was subjected to reduction treatment at 773-1073 K for 1 hour under an NH 3 stream of 200 mL / min, and then cooled to room temperature. A supported photocatalyst “(CoO x / Co) / photo semiconductor 2 (LaTiO 2 N)” was obtained.
（比較例２：（ＮｉＯｘ／Ｎｉ）／光半導体３）
（光半導体３の調製）
Ｌａ２Ｏ３とＴｉＯ２とをモル比１：２でエタノールを用いて湿式混合し、これにフラックスであるＮａＣｌを（Ｌａ＋Ｔｉ）：（Ｎａ）＝１：１０のモル比で加えた。それ以降の処理については、光半導体２の調製と同様の手順とし、光半導体３（ＬａＴｉＯ２Ｎ）を得た。ＸＲＤにより単相のＬａＴｉＯ２Ｎの生成が確認された。
光半導体３（０．３ｇ）をＮｉ（ＮＯ３）２・６Ｈ２Ｏ（ＬａＴｉＯ２Ｎに対して２質量％のＮｉＯｘを構成する濃度）を含む水溶液（３ｍＬ）に添加し、蒸発皿内、ウォーターバス上でガラス棒により攪拌しながら溶媒を蒸発乾燥させた。その後、空気中、４７３Ｋで焼成することによって、ＮｉＯｘを光半導体３に担持してなる「ＮｉＯｘ／光半導体３」を得た。
得られたＮｉＯｘ／光半導体３を、２００ｍＬ／ｍｉｎのＮＨ３気流下で、９２３Ｋで１時間還元処理した後、室温まで冷却して、光半導体２にＮｉＯｘおよびＮｉを担持した光触媒「（ＮｉＯｘ／Ｎｉ）／光半導体３」を得た。
(Comparative Example 2: (NiO x / Ni) / Optical Semiconductor 3)
(Preparation of optical semiconductor 3)
La 2 O 3 and TiO 2 and a molar ratio of 1: 2 with ethanol were wet-mixed, to which the NaCl is flux (La + Ti) :( Na) = 1: was added at 10 molar ratio. For subsequent processing, the same procedure as preparation of optical semiconductor 2, to obtain the optical semiconductor 3 (LaTiO 2 N). XRD confirmed the formation of single-phase LaTiO 2 N.
The optical semiconductor 3 (0.3 g) was added to an aqueous solution (3 mL) containing Ni (NO 3 ) 2 .6H 2 O (concentration constituting 2% by mass of NiOx with respect to LaTiO 2 N). The solvent was evaporated to dryness while stirring with a glass rod on a water bath. Thereafter, in the air, by baking at 473 K, to obtain a formed by carrying NiO x to the optical semiconductor 3 "NiO x / optical semiconductor 3 '.
The obtained NiO x / photosemiconductor 3 was subjected to reduction treatment at 923 K for 1 hour under an NH 3 stream of 200 mL / min, then cooled to room temperature, and the photocatalyst “(N) supported on the optical semiconductor 2 with NiO x and Ni” NiO x / Ni) / optical semiconductor 3 ”was obtained.
（比較例３：ＮｉＯｘ／光半導体１）
得られた光半導体１（０．１ｇ）に、水（０．５ｍＬ）と硝酸ニッケル（ＬａＴｉＯ２Ｎに対して２質量％のＮｉＯｘを構成する濃度）水溶液を混ぜて１分間超音波処理した後、減圧下、溶媒を留去し乾固させた。乾固した窒化物を取り出し乳鉢ですり潰した後、アンモニア気流下（５０ｍＬ／ｍｉｎ）、５５０℃で１時間加熱処理を行なうことによりＮｉＯｘ／ＬａＴｉＯ２Ｎを得た。
(Comparative Example 3: NiOx / Optical Semiconductor 1)
After mixing the obtained optical semiconductor 1 (0.1 g) with water (0.5 mL) and an aqueous solution of nickel nitrate (concentration constituting 2% by mass of NiOx with respect to LaTiO 2 N) and sonicating for 1 minute. The solvent was distilled off under reduced pressure to dryness. The dried nitride was taken out and ground in a mortar, and then heated at 550 ° C. for 1 hour in an ammonia stream (50 mL / min) to obtain NiOx / LaTiO 2 N.
（比較例４：ＣｏＯｘ／光半導体１）
得られた光半導体１（０．１ｇ）に、水（０．５ｍＬ）と硝酸コバルト（ＬａＴｉＯ２Ｎに対して３質量％のＣｏＯｘを構成する濃度）水溶液を混ぜて１分間超音波処理した後、減圧下、溶媒を留去し乾固させた。乾固した窒化物を取り出し乳鉢ですり潰した後、アンモニア気流下（５０ｍＬ／ｍｉｎ）、６５０℃で１時間加熱処理を行なうことによりＣｏＯｘ／ＬａＴｉＯ２Ｎを得た。
(Comparative Example 4: CoOx / Optical Semiconductor 1)
After mixing the obtained optical semiconductor 1 (0.1 g) with water (0.5 mL) and an aqueous solution of cobalt nitrate (concentration constituting 3% by mass of CoOx with respect to LaTiO 2 N) and sonicating for 1 minute. The solvent was distilled off under reduced pressure to dryness. After the dried nitride was taken out and ground in a mortar, heat treatment was performed at 650 ° C. for 1 hour in an ammonia stream (50 mL / min) to obtain CoOx / LaTiO 2 N.
（参考例１：ＣｏＯｘ：ＮｉＯｘ／ＬａＴｉＯ２Ｎ）
得られた光半導体１（０．１ｇ）に水（０．５ｍＬ）と硝酸ニッケル（ＬａＴｉＯ２Ｎに対して２質量％のＮｉＯｘを構成する濃度）水溶液と硝酸コバルト（ＬａＴｉＯ２Ｎに対して３質量％のＣｏＯｘを構成する濃度）水溶液とを混ぜて１分間超音波処理した後、減圧下、溶媒を留去し乾固させた。乾固した窒化物を取り出し乳鉢ですり潰した後、アンモニア気流下（５０ｍＬ／ｍｉｎ）、６５０℃で１時間加熱処理を行なうことによりＣｏＯｘ：ＮｉＯｘ／ＬａＴｉＯ２Ｎを得た。
光半導体１におけるＮｉ原子に対するＣｏ原子の比率は１：１．２であった。
(Reference Example 1: CoOx: NiOx / LaTiO 2 N)
The obtained optical semiconductor 1 (0.1 g) was mixed with water (0.5 mL), nickel nitrate (concentration constituting 2% by mass of NiOx with respect to LaTiO 2 N) and cobalt nitrate (3 with respect to LaTiO 2 N). After mixing with an aqueous solution (concentration constituting mass% CoOx) and sonicating for 1 minute, the solvent was distilled off under reduced pressure to dryness. After the dried nitride was taken out and ground in a mortar, heat treatment was performed at 650 ° C. for 1 hour in an ammonia stream (50 mL / min) to obtain CoOx: NiOx / LaTiO 2 N.
The ratio of Co atoms to Ni atoms in the optical semiconductor 1 was 1: 1.2.
（参考例２：ＮｉＯｘ／ＣｏＯｘ／ＬａＴｉＯ２Ｎ）
得られた光半導体１（０．１ｇ）に、水（０．５ｍＬ）と硝酸コバルト（ＬａＴｉＯ２Ｎに対して３質量％のＣｏＯｘを構成する濃度）を混ぜて１分間超音波で処理した後、減圧下、溶媒を留去し乾固させた。乾固した窒化物を取り出し、乳鉢ですり潰した後、アンモニア気流下（５０ｍＬ／ｍｉｎ）、６５０℃で１時間加熱処理を行なうことによりＣｏＯｘ／ＬａＴｉＯ２Ｎを得た。さらに得られたＣｏＯｘ／ＬａＴｉＯ２Ｎ（０．１ｇ）に、水（０．５ｍＬ）と硝酸ニッケル水溶液（ＬａＴｉＯ２Ｎに対して２質量％のＮｉＯｘを構成する濃度）を混ぜて１分間超音波で処理した後、減圧下、溶媒を留去し乾固させた。乾固した窒化物を取り出し乳鉢ですり潰した後、アンモニア気流下（５０ｍＬ／ｍｉｎ）、５５０℃で１時間加熱処理を行なうことによりＮｉＯｘ（２質量％）／ＣｏＯｘ（２質量％）／光半導体１（ＬａＴｉＯ２Ｎ）を得た。
(Reference Example 2: NiOx / CoOx / LaTiO 2 N)
After mixing the obtained optical semiconductor 1 (0.1 g) with water (0.5 mL) and cobalt nitrate (concentration constituting 3% by mass of CoOx with respect to LaTiO 2 N) and treating with ultrasonic waves for 1 minute. The solvent was distilled off under reduced pressure to dryness. After the dried nitride was taken out and ground in a mortar, heat treatment was performed at 650 ° C. for 1 hour in an ammonia stream (50 mL / min) to obtain CoOx / LaTiO 2 N. Further, the obtained CoOx / LaTiO 2 N (0.1 g) was mixed with water (0.5 mL) and a nickel nitrate aqueous solution (concentration constituting 2% by mass of NiOx with respect to LaTiO 2 N) for 1 minute. Then, the solvent was distilled off under reduced pressure to dryness. Nitrox (2% by mass) / CoOx (2% by mass) / photosemiconductor 1 is obtained by removing the dried nitride and grinding it in a mortar and then heat-treating it in an ammonia stream (50 mL / min) at 550 ° C. for 1 hour. (LaTiO 2 N) was obtained.
＜光水分解反応用電極の作製＞
得られた光触媒（３０ｍｇ）を１ｍＬの２−プロパノールに懸濁させ、この懸濁液２００μＬを第１のガラス基材（ソーダライムガラス３０×３０ｍｍ）上に滴下、乾燥を３回繰り返して光触媒層を形成した。次に、接触層となるＴａをスパッタ法により積層した。装置はＵＬＶＡＣ ＶＰＣ−２６０Ｆを使用し、数百ｎｍ程度積層した。次に、集電導体層となるＴｉをスパッタ法により数μｍ程度積層した。その後、導電性両面カーボンテープの片面を第２のガラス基材（ソーダライムガラス；図示せず）に接着し、さらに片面を集電層に接着した。最後に第１のガラス基材を除去し、純水中で１０分間超音波洗浄することで、複合光触媒層／接触層／集電層を備えた光水分解反応用電極を得た。
<Production of electrode for photohydrolysis reaction>
The obtained photocatalyst (30 mg) was suspended in 1 mL of 2-propanol, 200 μL of this suspension was dropped onto the first glass substrate (soda lime glass 30 × 30 mm), and drying was repeated three times to form a photocatalyst layer. Formed. Next, Ta serving as a contact layer was laminated by sputtering. The apparatus used was ULVAC VPC-260F and was laminated about several hundred nm. Next, Ti which becomes a current collecting conductor layer was laminated by about several μm by sputtering. Thereafter, one side of the conductive double-sided carbon tape was bonded to a second glass substrate (soda lime glass; not shown), and one side was further bonded to the current collecting layer. Finally, the first glass substrate was removed, and ultrasonic cleaning was performed in pure water for 10 minutes to obtain a photowater decomposition reaction electrode including a composite photocatalyst layer / contact layer / current collecting layer.
＜電極の性能評価＞
調製した光触媒電極の性能は、ポテンショスタットを用いた３電極系での電流−電位測定によって行った（図２）。平面窓付きのパイレックス（登録商標）ガラス製電気化学セルを用い、参照極にＡｇ／ＡｇＣｌ電極、対極にＰｔワイヤを用いた。電解液にはＫ２ＨＰＯ４０．２Ｍ水溶液（ｐＨ＝１３）を用いた。電気化学セル内部はアルゴンで満たし、かつ、測定前に十分にバブリングを行うことによって溶存する酸素、二酸化炭素を除去した。光電気化学測定には、ソーラーシュミレーター（ＡＭ１．５）を光源として用い、電気化学セルの平面窓から波長４２０ｎｍ以上の白色光を照射した。それぞれの電極について、測定電位１．２３Ｖ（ｖｓ． ＲＨＥ）における光電流密度（ｍＡ／ｃｍ２）を測定した。結果を下記表１に示す。
<Electrode performance evaluation>
The performance of the prepared photocatalytic electrode was measured by current-potential measurement in a three-electrode system using a potentiostat (FIG. 2). A Pyrex (registered trademark) glass electrochemical cell with a flat window was used, an Ag / AgCl electrode was used as the reference electrode, and a Pt wire was used as the counter electrode. A K 2 HPO 4 0.2M aqueous solution (pH = 13) was used as the electrolytic solution. The inside of the electrochemical cell was filled with argon, and dissolved oxygen and carbon dioxide were removed by sufficiently bubbling before measurement. In the photoelectrochemical measurement, a solar simulator (AM1.5) was used as a light source, and white light having a wavelength of 420 nm or more was irradiated from a planar window of the electrochemical cell. For each electrode, the photocurrent density (mA / cm 2 ) at a measurement potential of 1.23 V (vs. RHE) was measured. The results are shown in Table 1 below.
＜電極の耐久性の評価＞
上記と同様の測定条件によって、電解液の分解を３０分間連続して行い、当該３０分経過後における光電流密度を耐久性評価の指標とした。結果を以下の表１に示す。
<Evaluation of electrode durability>
Under the same measurement conditions as described above, the electrolytic solution was continuously decomposed for 30 minutes, and the photocurrent density after the lapse of 30 minutes was used as an index for durability evaluation. The results are shown in Table 1 below.
また、元素分析により、実施例２において担持された助触媒に含まれるＯ、Ｃｏ、Ｎｉの元素比率の平均値と、比較例５において担持された助触媒に含まれるＯ、Ｃｏ、Ｎｉの元素比率の平均値とをそれぞれ特定した。元素比率はSEM-EDXを用いたライン分析測定を行い、その平均値は３点測定したのち平均を取り算出した。結果を下記表２に示す。 Further, by elemental analysis, the average value of the element ratios of O, Co, and Ni contained in the promoter supported in Example 2, and the elements of O, Co, and Ni contained in the promoter supported in Comparative Example 5 The average ratio was specified. The element ratio was calculated by taking the line analysis using SEM-EDX and measuring the average value after measuring three points. The results are shown in Table 2 below.
表１に示す結果から明らかなように、光半導体１を用いた場合においては、助触媒としてＣｏＯｘのみ（比較例３）、ＮｉＯｘのみ（比較例４）を担持した場合や、ＣｏＯｘとＣｏ（比較例１）、ＮｉＯｘとＮｉ（比較例２）を担持した場合と比較して、助触媒としてＮｉＯｘとＣｏＯｘを担持した光触媒（実施例１〜３）方が、高い非光電密度と耐久性を有することが分かる。またＮｉＯｘとＣｏＯｘと同時に担持させた場合（参考例１）と比較すると、本願発明の方法で担持させた光触媒の方が高い光電密度と耐久性を示すことも分かる。 As is apparent from the results shown in Table 1, when the optical semiconductor 1 is used, only CoOx (Comparative Example 3), only NiOx (Comparative Example 4) is supported as a co-catalyst, or CoOx and Co (comparison). example 1), compared with the case of carrying NiOx and Ni (Comparative example 2), it photocatalyst carrying NiOx and CoO x as a cocatalyst (example 1-3) has a high non-photoelectric density and durability It turns out that it has. It can also be seen that the photocatalyst supported by the method of the present invention exhibits higher photoelectric density and durability than the case where NiOx and CoOx are simultaneously supported (Reference Example 1).
さらに、参考例１と実施例２との比較から、助触媒を構成する酸素原子、ニッケル原子、およびコバルト原子のニッケル原子またはコバルト原子に対する酸素原子の存在比（Ｏ／ＮｉまたはＯ／Ｃｏ）が、１より大きいほうが、高い光電密度と耐久性を示すことも分かる。 Further, from the comparison between Reference Example 1 and Example 2, the oxygen atom, nickel atom, and cobalt atom constituting the promoter have an abundance ratio of oxygen atom to nickel atom or cobalt atom (O / Ni or O / Co). It can also be seen that a value larger than 1 indicates higher photoelectric density and durability.
以上、現時点において、もっとも、実践的であり、かつ、好ましいと思われる実施形態に関連して本発明を説明したが、本発明は、本願明細書中に開示された実施形態に限定されるものではなく、請求の範囲および明細書全体から読み取れる発明の要旨或いは思想に反しない範囲で適宜変更可能であり、そのような変更を伴う光触媒およびその製造方法もまた本発明の技術的範囲に包含されるものとして理解されなければならない。 While the present invention has been described in connection with embodiments that are presently the most practical and preferred, the present invention is not limited to the embodiments disclosed herein. However, the present invention can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification, and a photocatalyst and a method for producing the same are also included in the technical scope of the present invention. Must be understood.
本発明に係る光触媒は高い水分解活性を有し、太陽光を利用した水分解反応を行うことにより水素および／または酸素を製造する光水分解反応に特に好適に用いられる。 The photocatalyst according to the present invention has a high water splitting activity, and is particularly preferably used for a photowater splitting reaction that produces hydrogen and / or oxygen by performing a water splitting reaction using sunlight.
Claims (7)
Ｔｉ、Ｔａおよび／またはＮｂを含む光半導体に、ＮｉＯｘを担持させる第１の工程と、
前記光半導体および／または前記ＮｉＯｘ上にＣｏＯｘを担持させる第２の工程と、を有することを特徴とする光触媒の製造方法。 A method for producing a photocatalyst obtained by supporting NiOx and CoOx as a cocatalyst on an optical semiconductor containing Ti, Ta, and / or Nb,
A first step of supporting NiOx on an optical semiconductor containing Ti, Ta and / or Nb;
And a second step of supporting CoOx on the optical semiconductor and / or the NiOx.
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Cited By (3)
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| CN111250094A (en) * | 2020-03-24 | 2020-06-09 | 辽宁大学 | Double Z type Co3O4/NiCo2O4/NiO photocatalyst and preparation method and application thereof |
| CN111804323A (en) * | 2020-06-24 | 2020-10-23 | 广东邦普循环科技有限公司 | Photocatalyst and application thereof in photocatalytic environment-friendly treatment of power battery |
| CN117244579A (en) * | 2023-10-31 | 2023-12-19 | 海南师范大学 | Photo-thermal synthesis method and application of cocatalyst-modified thin-layer carbon nitride material |
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Cited By (7)
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| CN111250094A (en) * | 2020-03-24 | 2020-06-09 | 辽宁大学 | Double Z type Co3O4/NiCo2O4/NiO photocatalyst and preparation method and application thereof |
| CN111250094B (en) * | 2020-03-24 | 2022-06-14 | 辽宁大学 | Double Z type Co3O4/NiCo2O4/NiO photocatalyst and preparation method and application thereof |
| CN111804323A (en) * | 2020-06-24 | 2020-10-23 | 广东邦普循环科技有限公司 | Photocatalyst and application thereof in photocatalytic environment-friendly treatment of power battery |
| WO2021258856A1 (en) * | 2020-06-24 | 2021-12-30 | 广东邦普循环科技有限公司 | Photocatalyst and application thereof in photocatalytic environmentally-friendly treatment of power batteries |
| US11826729B2 (en) | 2020-06-24 | 2023-11-28 | Guangdong Brunp Recycling Technology Co., Ltd. | Photocatalyst and application thereof in environmentally friendly photocatalytic treatment of power battery |
| CN117244579A (en) * | 2023-10-31 | 2023-12-19 | 海南师范大学 | Photo-thermal synthesis method and application of cocatalyst-modified thin-layer carbon nitride material |
| CN117244579B (en) * | 2023-10-31 | 2024-05-10 | 海南师范大学 | Photo-thermal synthesis method and application of cocatalyst-modified thin-layer carbon nitride material |
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