KR20200099858A - Synthetic method of zinc iron oxide on graphene and its photocatalytic activity under sunlight irradation - Google Patents
Synthetic method of zinc iron oxide on graphene and its photocatalytic activity under sunlight irradation Download PDFInfo
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- KR20200099858A KR20200099858A KR1020190018020A KR20190018020A KR20200099858A KR 20200099858 A KR20200099858 A KR 20200099858A KR 1020190018020 A KR1020190018020 A KR 1020190018020A KR 20190018020 A KR20190018020 A KR 20190018020A KR 20200099858 A KR20200099858 A KR 20200099858A
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 43
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 33
- 230000001699 photocatalysis Effects 0.000 title abstract description 26
- NNGHIEIYUJKFQS-UHFFFAOYSA-L hydroxy(oxo)iron;zinc Chemical compound [Zn].O[Fe]=O.O[Fe]=O NNGHIEIYUJKFQS-UHFFFAOYSA-L 0.000 title 1
- 238000010189 synthetic method Methods 0.000 title 1
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 174
- 239000002114 nanocomposite Substances 0.000 claims abstract description 72
- 239000011941 photocatalyst Substances 0.000 claims abstract description 39
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- 238000000034 method Methods 0.000 claims abstract description 25
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- 239000011701 zinc Substances 0.000 claims abstract description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910001308 Zinc ferrite Inorganic materials 0.000 claims abstract description 17
- WGEATSXPYVGFCC-UHFFFAOYSA-N zinc ferrite Chemical compound O=[Zn].O=[Fe]O[Fe]=O WGEATSXPYVGFCC-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000008367 deionised water Substances 0.000 claims abstract description 16
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 16
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- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 claims abstract description 11
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 11
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- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims abstract description 8
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 12
- 239000006185 dispersion Substances 0.000 claims description 9
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- ONDPHDOFVYQSGI-UHFFFAOYSA-N zinc nitrate Chemical compound [Zn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ONDPHDOFVYQSGI-UHFFFAOYSA-N 0.000 claims description 9
- MVFCKEFYUDZOCX-UHFFFAOYSA-N iron(2+);dinitrate Chemical compound [Fe+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MVFCKEFYUDZOCX-UHFFFAOYSA-N 0.000 claims description 4
- JIAARYAFYJHUJI-UHFFFAOYSA-L zinc dichloride Chemical compound [Cl-].[Cl-].[Zn+2] JIAARYAFYJHUJI-UHFFFAOYSA-L 0.000 claims description 4
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- ZOIORXHNWRGPMV-UHFFFAOYSA-N acetic acid;zinc Chemical compound [Zn].CC(O)=O.CC(O)=O ZOIORXHNWRGPMV-UHFFFAOYSA-N 0.000 claims description 2
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 2
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 2
- PVFSDGKDKFSOTB-UHFFFAOYSA-K iron(3+);triacetate Chemical compound [Fe+3].CC([O-])=O.CC([O-])=O.CC([O-])=O PVFSDGKDKFSOTB-UHFFFAOYSA-K 0.000 claims description 2
- 239000004246 zinc acetate Substances 0.000 claims description 2
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/39—Photocatalytic properties
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- B01J35/004—
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/18—Carbon
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- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/80—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with zinc, cadmium or mercury
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- C02F1/00—Treatment of water, waste water, or sewage
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Abstract
Description
본 발명은 그래핀 상에서의 아연페라이트의 합성방법 및 이를 이용한 태양광 하에서의 광촉매 활성에 관한 것으로, 구체적으로 환원된 산화그래핀(rGO) 상에 아연페라이트 (ZnFe2O4) 나노입자가 결합된 나노복합체(ZnFe2O4@rGO)를 제조하고, 이를 광촉매로 이용하는 것이다.The present invention relates to a method for synthesizing zinc ferrite on graphene and photocatalytic activity under sunlight using the same, and specifically, nanoparticles in which zinc ferrite (ZnFe 2 O 4 ) nanoparticles are bound on reduced graphene oxide (rGO) A composite (ZnFe 2 O 4 @rGO) was prepared and used as a photocatalyst.
페라이트는 화학식 AB2O4를 갖는 화합물이며, A와 B는 철 (Fe)을 포함한 다양한 금속양이온을 나타낸다. 최근 아연페라이트 (ZnFe2O4, A=Zn 및 B=Fe) 및 그 복합체의 특성 및 응용에 관한 연구가 활발히 진행되고 있다. 아연페라이트는 4 면체의 A-사이트를 차지하는 Zn2+ 이온, 8 면체의 B-사이트를 차지하는 Fe3+ 이온, 그리고 입방밀집구조 (cubic close-packed; ccp) 배열의 32개의 산소 원자로 이루어진 단위 셀을 가진 전통적인 스피넬형 복합 산화물이다. 광촉매 용도의 반도체로서 아연페라이트는 1.9 eV의 좁은 광학밴드갭, 높은 광화학적 안정성, 낮은 표면 재결합속도, 낮은 독성, 실온에서의 강자성 특성, 저렴한 비용, 친환경적인 특징이 있다. 아연페라이트는 고체 상태 반응, 가수분해, 공침, 연소, 폴리올 공정, 열분해, 수열 방법, 용매열 방법 등과 같은 다양한 방법으로 합성되어진다.Ferrite is a compound having the formula AB 2 O 4 , and A and B represent various metal cations including iron (Fe). Recently, studies on the properties and applications of zinc ferrite (ZnFe 2 O 4 , A=Zn and B=Fe) and composites thereof have been actively conducted. Zinc ferrite is a unit cell consisting of Zn 2+ ions occupying tetrahedral A-site, Fe 3+ ions occupying octahedral B-site, and 32 oxygen atoms in a cubic close-packed (ccp) arrangement. It is a traditional spinel type composite oxide with As a semiconductor for photocatalytic applications, zinc ferrite has a narrow optical band gap of 1.9 eV, high photochemical stability, low surface recombination rate, low toxicity, ferromagnetic properties at room temperature, low cost, and eco-friendly features. Zinc ferrite is synthesized by various methods such as solid state reaction, hydrolysis, coprecipitation, combustion, polyol process, pyrolysis, hydrothermal method, solvent heat method, and the like.
그러나 일반적으로 금속산화물 나노입자 (nanoparticles, NP)는 높은 표면에너지 때문에 큰 입자로 응집되는 경향이 있으며, 이로 인해 표면적이 감소하고 촉매 응용에서 성능이 떨어지는 문제점이 있어 왔다. 이에, 많은 연구자들이 금속산화물 나노입자를 변형하여 나노복합체를 제조하려는 시도가 이루어지고 있으나, 나노복합체를 제조하기 위해 높은 열쳐리 또는 마이크로웨이브 처리를 필요로 하는 등 제조방법이 복잡하며, 광촉매로서 응용하기 위한 성능 또한 우수하지 못한 문제점이 있다.However, in general, metal oxide nanoparticles (NPs) tend to agglomerate into large particles due to their high surface energy, resulting in a reduction in surface area and poor performance in catalyst applications. Accordingly, many researchers have attempted to manufacture nanocomposites by modifying metal oxide nanoparticles, but the manufacturing method is complicated, such as requiring high heat treatment or microwave treatment to produce nanocomposites, and applied as a photocatalyst. There is also a problem that the performance to do is not excellent.
따라서 광촉매로서 성능이 우수하며, 손쉽게 합성 가능한 금속산화물 나노복합체의 제조방법 및 이를 이용한 광촉매 활성에 대한 연구가 필요한 실정이다.Therefore, there is a need for research on a method of manufacturing a metal oxide nanocomposite that has excellent performance as a photocatalyst and can be easily synthesized and a photocatalytic activity using the same.
본 발명의 목적은 광촉매로서 성능이 우수하며, 손쉽게 합성 가능한 ZnFe2O4@rGO 나노복합체 광촉매 제조방법을 제공하는 데에 있다.An object of the present invention is to provide a method for manufacturing a photocatalyst of ZnFe 2 O 4 @rGO nanocomposite that has excellent performance as a photocatalyst and can be easily synthesized.
또한, 본 발명의 다른 목적은 상기 ZnFe2O4@rGO 나노복합체 광촉매 제조방법으로 제조된 ZnFe2O4@rGO 나노복합체 광촉매를 제공하는 데에 있다.In addition, another object of the present invention is to provide a ZnFe 2 O 4 @rGO nanocomposite photocatalyst prepared by the method of manufacturing the ZnFe 2 O 4 @rGO nanocomposite photocatalyst.
상기 목적을 달성하기 위하여, 본 발명아연 전구체 및 철 전구체를 탈이온수에 용해시켜 제1혼합용액을 준비하는 단계; 산화그래핀(GO)을 탈이온수에 분산시켜 GO 분산액을 준비하는 단계; 상기 제1혼합용액에 아세트산나트륨(sodium acetate)를 첨가하여 제2혼합용액을 준비하는 단계; 상기 제2혼합용액에 GO 분산액을 첨가하여 제3혼합용액을 준비하는 단계; 상기 제3혼합용액에 수산화나트륨(sodium hydroxide)를 첨가하여 현탁액을 준비하는 단계; 및 상기 현탁액을 열처리하여 환원된 산화그래핀(rGO) 상에 아연페라이트(ZnFe2O4) 나노입자가 결합된 나노복합체(ZnFe2O4@rGO)를 수득하는 단계; 를 포함하는, ZnFe2O4@rGO 나노복합체 광촉매 제조방법을 제공한다.In order to achieve the above object, preparing a first mixed solution by dissolving a zinc precursor and an iron precursor of the present invention in deionized water; Preparing a GO dispersion by dispersing graphene oxide (GO) in deionized water; Preparing a second mixed solution by adding sodium acetate to the first mixed solution; Preparing a third mixed solution by adding a GO dispersion to the second mixed solution; Preparing a suspension by adding sodium hydroxide to the third mixed solution; And heat-treating the suspension to obtain a nanocomposite (ZnFe 2 O 4 @rGO) in which zinc ferrite (ZnFe 2 O 4 ) nanoparticles are bonded on the reduced graphene oxide (rGO). It provides a method for producing a photocatalyst of ZnFe 2 O 4 @rGO nanocomposite comprising a.
또한, 본 발명은 상기 ZnFe2O4@rGO 나노복합체 광촉매 제조방법에 의해 제조된 ZnFe2O4@rGO 나노복합체 광촉매를 제공한다.In addition, the present invention provides a ZnFe 2 O 4 @rGO nanocomposite photocatalyst prepared by the method of manufacturing the ZnFe 2 O 4 @rGO nanocomposite photocatalyst.
본 발명의 ZnFe2O4@rGO 나노복합체 광촉매 제조방법은 높은 열처리나 마이크로웨이브 처리 없이 또한, 독성물질의 필요 없이 간단하고, 친환경적으로 수열합성방법을 통해 제조될 수 있다.The ZnFe 2 O 4 @rGO nanocomposite photocatalyst manufacturing method of the present invention can be manufactured through a simple and environmentally friendly hydrothermal synthesis method without high heat treatment or microwave treatment and without the need for toxic substances.
또한, 본 발명에 따라 제조된 ZnFe2O4@rGO 나노복합체는 메조기공을 가져 비표면적이 높으며, 높은 결정성, 태양광 흡광능력, 빠른 전자이동능력 특성을 갖춰 과산화수소(hydrogen peroxide)를 사용하지 않고 태양광 하에서 오염물질을 분해할 수 있어 광촉매로서의 성능이 우수하다.In addition, the ZnFe 2 O 4 @rGO nanocomposite prepared according to the present invention has mesopores, has a high specific surface area, has high crystallinity, solar absorption capacity, and fast electron mobility characteristics, so that hydrogen peroxide is not used. It has excellent performance as a photocatalyst because it can decompose pollutants under sunlight without it.
또한, 본 발명에 따라 제조된 ZnFe2O4@rGO 나노복합체는 재사용성이 우수하며, 자기적 분리도 가능한 효과가 있다.In addition, the ZnFe 2 O 4 @rGO nanocomposite prepared according to the present invention has excellent reusability, and magnetic separation is possible.
도 1은 ZnFe2O4@rGO 나노복합체의 수열합성 반응을 나타낸 도면이다.
도 2는 ZnFe2O4 및 ZnFe2O4@rGO 나노복합체의 (a) XRD 패턴 및 (b) 라만 스펙트럼을 나타낸 도면이다.
도 3은 GO와 ZnFe2O4@rGO 나노복합체의 FT-IR 스펙트럼을 나타낸 도면이다.
도 4는 (a-e) ZnFe2O4@rGO-H20(NaOH)-1 및 (f) GO의 XPS 스펙트럼을 나타낸 도면이다.
도 5는 ZnFe2O4-H20(NaOH)(왼쪽) 및 ZnFe2O4@rGO-H20(NaOH)-1(오른쪽) 시료의 (a, b) FE-SEM, (c-f) HRTEM 이미지 및 (g, h) SEAD 패턴을 나타낸 이미지이다.
도 6은 (a, b) ZnFe2O4-H20(NaOH) 및 (c, d) ZnFe2O4@rGO-H20(NaOH)-1 나노복합체의 N2 흡탈착등온선 및 기공크기분포(pore-size distribution; PSD)를 나타낸 도면이다.
도 7은 (a) UV-vis 확산반사 스펙트럼, (b) 나이퀴스트선도(Nyquist plot), (c) 태양광시뮬레이터(solar simulator)를 이용하여 태양광 조사 하에서의 광전류 반응, (d) ZnFe2O4 및 ZnFe2O4@rGO 복합체의 광발광(photoluminescence) 스펙트럼, (e) 염료분해실험 결과 (삽입된 도면은 자기장 없이 MB 수용액에서 분산된 ZnFe2O4@rGO-H20(NaOH)-1의 촉매(왼쪽) 및 수 초 내에 접촉된 자기장과 함께 분산된 ZnFe2O4@rGO-H20(NaOH)-1의 촉매(오른쪽)을 보여준다), (f) 포집시약(trapping agent)을 첨가한 후 염료광분해의 백분율 감소에 대한 포집실험 결과를 나타낸 도면이다.
도 8은 태양광 조사 하에서 ZnFe2O4@rGO-H20(NaOH)-1의 MB 분해반응메카니즘을 나타낸 도면이다.1 is a diagram showing a hydrothermal synthesis reaction of a ZnFe 2 O 4 @rGO nanocomposite.
2 is a diagram showing (a) XRD patterns and (b) Raman spectra of ZnFe 2 O 4 and ZnFe 2 O 4 @rGO nanocomposites.
3 is a view showing the FT-IR spectrum of GO and ZnFe 2 O 4 @rGO nanocomposite.
4 is a view showing the XPS spectrum of (ae) ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 and (f) GO.
Figure 5 is a ZnFe 2 O 4 -H 2 0 (NaOH) (left) and ZnFe 2 O 4 @rGO-H 2 0 (NaOH) -1 (right) samples of (a, b) FE-SEM, (cf) It is an image showing the HRTEM image and (g, h) SEAD pattern.
Figure 6 is (a, b) ZnFe 2 O 4 -H 2 0 (NaOH) and (c, d) ZnFe 2 O 4 @rGO-H 2 0 (NaOH)-1 N 2 adsorption and desorption isotherms and pores of the nanocomposite It is a diagram showing pore-size distribution (PSD).
7 shows (a) UV-vis diffuse reflection spectrum, (b) Nyquist plot, (c) photocurrent reaction under sunlight irradiation using a solar simulator, (d) ZnFe 2 Photoluminescence spectrum of O 4 and ZnFe 2 O 4 @rGO complex, (e) dye decomposition test result (Insert drawing shows ZnFe 2 O 4 @rGO-H 2 0(NaOH) dispersed in MB aqueous solution without magnetic field -1 catalyst (left) and the catalyst of ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 dispersed with a magnetic field in contact within a few seconds (shown right)), (f) trapping agent ) Is added and the result of the collection experiment for the percentage reduction of dye photolysis is shown.
8 is a view showing the mechanism of the MB decomposition reaction of ZnFe 2 O 4 @rGO-H 2 0 (NaOH)-1 under sunlight irradiation.
이하에서는 본 발명을 구체적으로 설명한다.Hereinafter, the present invention will be described in detail.
본 발명자들은 아세트산나트륨 및 수산화나트륨의 첨가에 의해 간단한 제조방법으로 ZnFe2O4@rGO 나노복합체 광촉매를 제조할 수 있으며, 이렇게 제조된 ZnFe2O4@rGO 나노복합체는 메조기공을 가져 비표면적이 높으며, 높은 결정성, 태양광 흡광능력, 빠른 전자이동능력 특성을 갖춰 과산화수소를 사용하지 않고 태양광 하에서 오염물질을 분해할 수 있어 광촉매로서 유용하게 활용될 수 있음을 밝혀내어 본 발명을 완성하였다.The present inventors can prepare a ZnFe 2 O 4 @rGO nanocomposite photocatalyst by a simple manufacturing method by adding sodium acetate and sodium hydroxide, and the thus prepared ZnFe 2 O 4 @rGO nanocomposite has mesopores and has a specific surface area. The present invention was completed by finding that it can be usefully used as a photocatalyst because it has high crystallinity, solar absorption capacity, and fast electron mobility characteristics, so that contaminants can be decomposed under sunlight without using hydrogen peroxide.
본 발명은 아연 전구체 및 철 전구체를 탈이온수에 용해시켜 제1혼합용액을 준비하는 단계; 산화그래핀(GO)을 탈이온수에 분산시켜 GO 분산액을 준비하는 단계; 상기 제1혼합용액에 아세트산나트륨을 첨가하여 제2혼합용액을 준비하는 단계; 상기 제2혼합용액에 GO 분산액을 첨가하여 제3혼합용액을 준비하는 단계; 상기 제3혼합용액에 수산화나트륨을 첨가하여 현탁액을 준비하는 단계; 및 상기 현탁액을 열처리하여 환원된 산화그래핀(rGO) 상에 아연페라이트(ZnFe2O4) 나노입자가 결합된 나노복합체(ZnFe2O4@rGO)를 수득하는 단계;를 포함하는, ZnFe2O4@rGO 나노복합체 광촉매 제조방법을 제공한다.The present invention comprises the steps of preparing a first mixed solution by dissolving a zinc precursor and an iron precursor in deionized water; Preparing a GO dispersion by dispersing graphene oxide (GO) in deionized water; Preparing a second mixed solution by adding sodium acetate to the first mixed solution; Preparing a third mixed solution by adding a GO dispersion to the second mixed solution; Preparing a suspension by adding sodium hydroxide to the third mixed solution; And obtaining a nanocomposite (ZnFe 2 O 4 @rGO) in which zinc ferrite (ZnFe 2 O 4 ) nanoparticles are bound on reduced graphene oxide (rGO) by heat treatment of the suspension; containing, ZnFe 2 O 4 @rGO Nanocomposite photocatalyst manufacturing method is provided.
이때, 상기 아연 전구체는 질산아연(II) (Zn(NO3)2), 염화아연(ZnCl2), 황산아연(ZnSO4) 및 초산아연(Zn(CH3COO)2)으로 이루어진 군에서 선택되는 어느 하나일 수 있으나, 이에 제한되는 것은 아니다.At this time, the zinc precursor is selected from the group consisting of zinc nitrate (II) (Zn(NO 3 ) 2 ), zinc chloride (ZnCl 2 ), zinc sulfate (ZnSO 4 ) and zinc acetate (Zn(CH 3 COO) 2 ) It may be any one, but is not limited thereto.
또한, 상기 철 전구체는 질산철(Ⅲ) (Fe(NO3)3), 염화철(FeCl3), 황산철(FeSO4) 및 초산철(Fe(CH3COO)2)로 이루어진 군에서 선택되는 어느 하나일 수 있으나, 이에 제한되는 것은 아니다.In addition, the iron precursor is selected from the group consisting of iron nitrate (III) (Fe(NO 3 ) 3 ), iron chloride (FeCl 3 ), iron sulfate (FeSO 4 ) and iron acetate (Fe(CH 3 COO) 2 ) It may be any one, but is not limited thereto.
또한, 상기 아연 전구체와 철 전구체는 1:2의 몰비로 용해시키는 것을 특징으로 하며, 상기 산화그래핀(GO)은 탈이온수 100 중량부에 대해 20 내지 50 중량부를 포함될 수 있다.In addition, the zinc precursor and the iron precursor are characterized by dissolving in a molar ratio of 1:2, and the graphene oxide (GO) may be included in 20 to 50 parts by weight based on 100 parts by weight of deionized water.
또한, 상기 제3혼합용액에 수산화나트륨을 첨가하여 현탁액을 준비하는 단계는 수산화나트륨을 첨가하여 염기성 pH로 조절할 수 있으나, 바람직하게는 pH 11로 조절할 수 있다.In addition, in the step of preparing a suspension by adding sodium hydroxide to the third mixed solution, the basic pH may be adjusted by adding sodium hydroxide, but preferably, the pH may be adjusted to 11.
이에, 수산화나트륨은 상기 ZnFe2O4@rGO 나노복합체 제조과정 중 pH를 조절하거나 유용한 광물(mineral)을 첨가해주는 역할을 할 수 있다.Thus, sodium hydroxide may play a role of adjusting pH or adding useful minerals during the manufacturing process of the ZnFe 2 O 4 @rGO nanocomposite.
또한, 상기 현탁액을 열처리하는 단계는 150 내지 250℃에서 5 내지 15시간 수행하는 것을 특징으로 하며, 바람직하게는 200℃ 에서 10시간 동안 열처리할 수 있으나, 이에 제한되는 것은 아니다.In addition, the step of heat-treating the suspension may be performed at 150 to 250° C. for 5 to 15 hours, and preferably at 200° C. for 10 hours, but is not limited thereto.
이때, 상기 제조방법의 조건을 벗어나면 본 발명에 따른 환원된 산화그래핀(rGO) 상에 아연페라이트(ZnFe2O4) 나노입자가 결합된 나노복합체(ZnFe2O4@rGO)가 제대로 형성되지 않아 광촉매활성이 우수하지 못하여 광촉매로서 유용하게 활용될 수 없는 문제가 야기될 수 있다.At this time, if the conditions of the manufacturing method are out of the above, a nanocomposite (ZnFe 2 O 4 @rGO) in which zinc ferrite (ZnFe 2 O 4 ) nanoparticles are bonded on the reduced graphene oxide (rGO) according to the present invention is properly formed. As a result, the photocatalytic activity is not excellent, and thus a problem that cannot be effectively used as a photocatalyst may be caused.
또한, 상기 아세트산나트륨(Sodium acetate)은 아연페라이트 나노입자의 크기를 조절해주며 안정화시키는 역할을 하여 큰 결정성장을 방해함으로써 아연페라이트 나노입자의 응집을 제한할 수 있다.In addition, the sodium acetate controls and stabilizes the size of the zinc ferrite nanoparticles, thereby preventing large crystal growth, thereby limiting the aggregation of the zinc ferrite nanoparticles.
이때, 아연페라이트(ZnFe2O4) 나노입자의 평균 입자크기는 1 내지 15 nm로 제조되며, 상기 ZnFe2O4@rGO 나노복합체는 평균 직경 3 내지 15 nm의 기공을 포함하여 비표면적을 증가시킬 수 있으며, 이에 따라 광촉매활성을 증가시킬 수 있다.At this time, the average particle size of the zinc ferrite (ZnFe 2 O 4 ) nanoparticles is prepared to be 1 to 15 nm, and the ZnFe 2 O 4 @rGO nanocomposite includes pores having an average diameter of 3 to 15 nm to increase the specific surface area. And, accordingly, the photocatalytic activity can be increased.
또한, 본 발명은 상기 ZnFe2O4@rGO 나노복합체 광촉매 제조방법에 의해 제조된 ZnFe2O4@rGO 나노복합체 광촉매를 제공한다.In addition, the present invention provides a ZnFe 2 O 4 @rGO nanocomposite photocatalyst prepared by the method of manufacturing the ZnFe 2 O 4 @rGO nanocomposite photocatalyst.
본 발명은 환원된 그래핀 산화물 (rGO)에 자기적으로 분리 가능한 ZnFe2O4 나노입자가 결합된 나노복합체(ZnFe2O4@rGO)를 추가적인 고온의 열처리 없이 간단하고, 친환경적으로 수열합성방법을 사용하여 제조하였다. 이러한 ZnFe2O4@rGO 나노복합체는 우수한 촉매활성을 위한 중요한 특성인 우수한 결정성 및 높은 BET 비표면적을 나타냈다. 또한, 나노복합체는 과산화수소의 도움 없이 태양광 조사 하에서 메틸렌블루(MB) 분해에 대한 우수한 광촉매 성능을 나타내었으며, 3회 이상 재사용이 가능하였다. 따라서 본 발명에 따른 나노복합체 제조방법은 무독성 시약의 사용, 간단한 단계 및 상대적으로 낮은 반응온도로 인해 대규모 작업에 적용될 수 있을 것이다.The present invention is a simple, eco-friendly hydrothermal synthesis method without additional high-temperature heat treatment of a nanocomposite (ZnFe 2 O 4 @rGO) in which magnetically separable ZnFe 2 O 4 nanoparticles are bonded to reduced graphene oxide (rGO) It was prepared using. This ZnFe 2 O 4 @rGO nanocomposite exhibited excellent crystallinity and high BET specific surface area, which are important properties for excellent catalytic activity. In addition, the nanocomposite exhibited excellent photocatalytic performance against decomposition of methylene blue (MB) under sunlight irradiation without the help of hydrogen peroxide, and could be reused three or more times. Therefore, the nanocomposite preparation method according to the present invention may be applied to large-scale operations due to the use of non-toxic reagents, simple steps, and relatively low reaction temperatures.
이하, 실시예를 통하여 본 발명을 더욱 상세히 설명하고자 한다. 이들 실시예는 오로지 본 발명을 보다 구체적으로 설명하기 위한 것으로, 본 발명의 요지에 따라 본 발명의 범위가 이들 실시예에 의해 제한되지 않는다는 것은 본 발명이 속하는 기술분야에서 통상의 지식을 가진 자에 있어서 자명할 것이다.Hereinafter, the present invention will be described in more detail through examples. These examples are only for describing the present invention in more detail, and that the scope of the present invention is not limited by these examples according to the gist of the present invention, to those of ordinary skill in the art. It will be self-evident.
<참고예> 실험재료<Reference Example> Experimental material
그래파이트(graphite;흑연, 99.9995 %, Junsei Chemical Co. Ltd.), 질산아연 (II) 6 수화물 (Zn(NO3)2 ·6H2O, 대정화학공업(주)), 질산철(Ⅲ) 9 수화물(Fe(NO3)3 ·9H2O, 대정화학공업(주)), 무수 아세트산나트륨(CH3COONa; NaOAc, 대정화학공업(주)), 에탄올 (> 94.5 %, 대정화학공업(주)), 메틸렌블루 (MB, CI 52015, 고순도, Alfa Aesar), 및 로다민 B (RhB, CI 45170, 대정화학공업(주))을 추가 정제 없이 사용하였다.Graphite (graphite, 99.9995%, Junsei Chemical Co. Ltd.), zinc nitrate (II) hexahydrate (Zn(NO 3 ) 2 · 6H 2 O, Daejung Chemical Industries Co., Ltd.), iron nitrate (III) 9 Hydrate (Fe(NO 3 ) 3 · 9H 2 O, Daejung Chemical Industry Co., Ltd.), Anhydrous Sodium Acetate (CH 3 COONa; NaOAc, Daejung Chemical Industry Co., Ltd.), ethanol (> 94.5%, Daejung Chemical Industry Co., Ltd.) )), methylene blue (MB, CI 52015, high purity, Alfa Aesar), and rhodamine B (RhB, CI 45170, Daejung Chemical Industries Co., Ltd.) were used without further purification.
<실시예 1> ZnFe<Example 1> ZnFe 22 OO 44 @rGO 광촉매 복합체의 제조Preparation of @rGO photocatalyst composite
산화그래핀(Graphene oxide; GO)은 Marcano-Tour의 방법에 따라 그라파이트의 화학적 박리를 통해 합성되었다(ACS Nano 2010, 4(8), 4806-4814). 탈이온 (Deionized;DI)수는 물과 관련된 모든 준비에 사용되었다.Graphene oxide (GO) was synthesized by chemical exfoliation of graphite according to the Marcano-Tour method ( ACS Nano 2010, 4(8), 4806-4814). Deionized (DI) water was used for all water related preparations.
ZnFe2O4@rGO 나노복합체는 탈이온수, NaOAc 및 1 M NaOH를 사용하여 수열, 자기조립공침(coprecipitation)법에 의해 합성되었다. 구체적으로, 도 1과 같이 Zn(NO3)2·6H2O 0.44 mmol과 Fe(NO3)3 ·9H2O 0.88 mmol을 탈이온수 20 ml에 용해시키고, GO 25 mg을 10분 동안 초음파 처리하여 5 ml의 탈이온수에 분산시켰다. 이후, 1.0 g의 NaOAc를 10분 동안 일정하게 교반하면서 Zn2+ 및 Fe3+ 이온을 함유하는 용액에 첨가하였다. 이 금속산화물 전구체 용액을 GO 분산액에 가한 다음 20 분 동안 초음파처리 하였다. 생성된 용액에 1M NaOH 용액을 첨가하여 pH를 11로 만들었다. 최종 현탁액을 50 ml Teflon-lined 스테인레스스틸 고압반응기(autoclave)로 옮기고 200 ℃에서 10 시간 동안 열처리한 후 자연적으로 실온에서 냉각시켰다. 이후, 진공 여과하여 고체 복합체를 수집하고, 탈이온수 및 에탄올로 연속적으로 세척하고, 대기 조건하에 60 ℃의 오븐에서 건조시켜 ZnFe2O4@rGO 광촉매 나노복합체를 제조하였다 (이하 'ZnFe2O4@rGO-H20(NaOH)-1'라 명명함). The ZnFe 2 O 4 @rGO nanocomposite was synthesized by hydrothermal and self-assembly coprecipitation using deionized water, NaOAc and 1 M NaOH. Specifically, as shown in FIG. 1, 0.44 mmol of Zn(NO 3 ) 2· 6H 2 O and 0.88 mmol of Fe(NO 3 ) 3 · 9H 2 O were dissolved in 20 ml of deionized water, and 25 mg of GO was sonicated for 10 minutes. And dispersed in 5 ml of deionized water. Thereafter, 1.0 g of NaOAc was added to the solution containing Zn 2+ and Fe 3+ ions with constant stirring for 10 minutes. This metal oxide precursor solution was added to the GO dispersion, followed by sonication for 20 minutes. 1M NaOH solution was added to the resulting solution to bring the pH to 11. The final suspension was transferred to a 50 ml Teflon-lined stainless steel autoclave, heat-treated at 200° C. for 10 hours, and then naturally cooled at room temperature. Thereafter, the solid complex was collected by vacuum filtration, washed successively with deionized water and ethanol, and dried in an oven at 60° C. under atmospheric conditions to prepare a ZnFe 2 O 4 @rGO photocatalytic nanocomposite (hereinafter'ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1').
<비교예 1> ZnFe<Comparative Example 1> ZnFe 22 OO 4 4 광촉매의 제조Preparation of photocatalyst
상기 제조예 1에서 GO 분산액을 첨가하지 않은 것을 제외하고는 동일한 방법으로 ZnFe2O4 나노입자를 제조하였다 (이하 'ZnFe2O4-H2O(NaOH)'라 명명함).ZnFe 2 O 4 nanoparticles were prepared in the same manner except that the GO dispersion was not added in Preparation Example 1 (hereinafter referred to as'ZnFe 2 O 4 -H 2 O (NaOH)').
<비교예 2> ZnFe<Comparative Example 2> ZnFe 22 OO 44 @rGO 광촉매 복합체의 제조Preparation of @rGO photocatalyst composite
상기 제조예 1에서 GO 50 mg을 첨가한 것을 제외하고는 동일한 방법으로 ZnFe2O4@rGO 광촉매 나노복합체를 제조하였다 (이하 'ZnFe2O4@rGO-H20(NaOH)-2'라 명명함).A ZnFe 2 O 4 @rGO photocatalyst nanocomposite was prepared in the same manner except that 50 mg of GO was added in Preparation Example 1 (hereinafter referred to as'ZnFe 2 O 4 @rGO-H 2 0 (NaOH)-2' Name).
<실시예 2> 분석<Example 2> Analysis
상기 실시예 1 내지 비교예 1, 2에 따라 제조된 광촉매 시료의 결정성은 벌크 X-선 회절기 (XRD; PANalytical, X'Pert-PRO MPD)에 의해 조사되었으며, 이는 Cu Kα 선 (λ = 0.154 nm) 하에서 40 kV의 가속전압, 30 mA의 전류 및 0.101°s-1의 스캔속도 (2θ)에서 수행되었다. The crystallinity of the photocatalytic samples prepared according to Examples 1 to 1 and 2 was investigated by a bulk X-ray diffractometer (XRD; PANalytical, X'Pert-PRO MPD), which is a Cu Kα ray (λ = 0.154). nm) at an acceleration voltage of 40 kV, a current of 30 mA, and a scan rate (2θ) of 0.101°s -1 .
또한, 시료의 형태 및 구조는 전계방출 주사전자현미경 (FE-SEM; Hitachi, S-4100) 및 투과전자현미경 (TEM; Philips, CM 200)에 의해 분석되었다. TITAN G2 ChemiSTEM Cs Probe 전자현미경을 사용하여 200 kV의 가속전압에서 고해상도 투과전자현미경 (HR-TEM) 이미지를 얻었다. In addition, the shape and structure of the sample were analyzed by a field emission scanning electron microscope (FE-SEM; Hitachi, S-4100) and a transmission electron microscope (TEM; Philips, CM 200). High-resolution transmission electron microscopy (HR-TEM) images were obtained at an acceleration voltage of 200 kV using a TITAN G2 ChemiSTEM Cs Probe electron microscope.
시료의 푸리에변환적외선 (Fourier-transform infrared; FT-IR) 분광분석은 Bio-Rad, Excalibur Series FTS 3000 분광기에서 수행되었다.Fourier-transform infrared (FT-IR) spectroscopy analysis of the sample was performed on a Bio-Rad,
라만분광법은 532 nm의 레이저 여기에서 XploRA plus (HORIBA) 라만분광기 모델을 사용하여 수행되었다. Raman spectroscopy was performed using the XploRA plus (HORIBA) Raman spectroscopy model at 532 nm laser excitation.
Al Kα 단색화 방사선을 사용하여 X-선 광전자분광법 (XPS, Kratos Analytical, AXIS Nova)에 의해 시료의 표면 원소 조성 및 화학적 상태를 조사하였다. The surface element composition and chemical state of the samples were investigated by X-ray photoelectron spectroscopy (XPS, Kratos Analytical, AXIS Nova) using Al Kα monochromatic radiation.
-196℃의 온도에서 N2 흡탈착장치 (Micromeritics Instruments Corp., Micromeritics 3Flex 표면특성분석기)를 사용하여 시료의 Brunauer-Emmett-Teller (BET) 비표면적 (SBET) 및 기공크기분포 (PSD)를 분석하였다. 흡착-탈착 실험 전에 시료를 200 ℃에서 24시간 동안 탈기시켰으며, BET 방정식을 사용하여 SBET를 계산하였고, BJH (Barrett-Joyner-Halenda) 분석을 적용하여 PSD를 얻었다. The Brunauer-Emmett-Teller (BET) specific surface area (S BET ) and pore size distribution (PSD) of the sample were determined using an N 2 adsorption/desorption device (Micromeritics Instruments Corp., Micromeritics 3Flex surface characterization analyzer) at -196℃. Analyzed. Before the adsorption-desorption experiment, the sample was degassed at 200° C. for 24 hours, S BET was calculated using the BET equation, and PSD was obtained by applying BJH (Barrett-Joyner-Halenda) analysis.
고체 시료의 UV-vis 확산반사스펙트럼 (UV-vis diffuse reflectance spectra; DRS)은 200 내지 800 nm의 파장 범위에 걸쳐 Varian Cary 5000 UV-vis-NIR 분광광도계를 사용하여 얻어졌다. The UV-vis diffuse reflectance spectra (DRS) of the solid sample was obtained using a Varian Cary 5000 UV-vis-NIR spectrophotometer over a wavelength range of 200 to 800 nm.
실온에서 호리바 (HORIBA) scientific 광발광분광기 (325 nm의 여기 레이저 파장)에서 광발광 (photoluminescence; PL) 분광분석을 수행하였다. Photoluminescence (PL) spectroscopy was performed in a HORIBA scientific photoluminescence spectrometer (excitation laser wavelength of 325 nm) at room temperature.
전기화학 임피던스분광법 (electrochemical impedance spectroscopy; EIS) 및 광전류 반응분석은 기존 3 전극 전지시스템을 사용하는 Autolab PGSTAT 302N (Metrohm) 기기에서 수행되었다.Electrochemical impedance spectroscopy (EIS) and photocurrent response analysis were performed on an Autolab PGSTAT 302N (Metrohm) instrument using an existing three-electrode battery system.
<실시예 3> 광촉매 활성 측정<Example 3> Photocatalytic activity measurement
제조된 시료의 광촉매활성은 태양광시뮬레이터 (ABET Technologies, 150W,> 300nm)를 사용하는 태양광 조사 하에서 염료분해를 통해 평가되었다. 광촉매 시료의 광분해효율을 분석하기 위해 폐수에서 모델 오염원으로 MB와 RhB가 사용되었다. 반응은 광화학반응기에서 실온 조건으로 수행되었다.The photocatalytic activity of the prepared sample was evaluated through dye decomposition under solar irradiation using a solar simulator (ABET Technologies, 150W,> 300nm). MB and RhB were used as model pollutants in wastewater to analyze the photolysis efficiency of the photocatalytic sample. The reaction was carried out at room temperature in a photochemical reactor.
20 mg의 광촉매 시료를 수성염료 용액 (10 mg L-1 농도) 40 ml (0.5 g L-1 촉매 부하)에 첨가하고, 염료와 촉매 사이의 흡착-탈착 평형을 확보하기 위해 반응 혼합물을 암실에서 30분 동안 교반하였다. 그 후, 광원의 스위치를 켰으며, 미리 설정된 시간 간격에서, 3 ml 시료를 회수하고, 13,000 rpm에서 7분간 원심분리하여 광촉매를 분리하였다. 광분해 과정 동안의 잔류염료농도는 각각 664 및 554 nm에서 MB 및 RhB 용액의 흡광도를 측정하여 모니터링 하였다. 20 mg of a photocatalyst sample was added to 40 ml of an aqueous dye solution (10 mg L -1 concentration) (0.5 g L -1 catalyst load), and the reaction mixture was placed in the dark to establish an adsorption-desorption equilibrium between the dye and catalyst. Stir for 30 minutes. Thereafter, the light source was switched on, and at a preset time interval, a 3 ml sample was collected and centrifuged at 13,000 rpm for 7 minutes to separate the photocatalyst. The residual dye concentration during the photolysis process was monitored by measuring the absorbance of the MB and RhB solutions at 664 and 554 nm, respectively.
포획(trapping) 실험은 염료의 광분해에 관여하는 지배적인 반응 종을 분석하기 위해 수행되었는데, 상기 포획 실험은 광 조사 전에 포획 또는 제거(scavenging) 화합물을 첨가(즉, 슈퍼옥사이드(superoxide) 라디칼(O2 ˙-)를 위한 0.001 M p-벤조퀴논(p-benzoquinone; p-BZQ), 하이드록시 라디칼(˙OH)을 위한 0.2M 이소프로필 알콜(isopropyl alcohol; IPA), 또는 정공(h +)을 위한 0.2 M 탄산수소나트륨(sodium bicarbonate; NaHCO3))하는 것을 제외하고는 광촉매활성 측정과 유사한 실험이다.The trapping experiment was performed to analyze the dominant reactive species involved in the photolysis of the dye, and the trapping experiment was performed by adding a trapping or scavenging compound (i.e., superoxide radical (O 2 ˙- ) for 0.001 M p -benzoquinone ( p- benzoquinone; p- BZQ), 0.2 M isopropyl alcohol (IPA) for hydroxy radicals (˙OH), or holes ( h + ). It is an experiment similar to the measurement of photocatalytic activity except for 0.2 M sodium bicarbonate (NaHCO 3 )).
10 mg L-1 MB 용액의 광촉매분해를 통한 ZnFe2O4@rGO-H20(NaOH)-1 광촉매의 재사용성을 분석하기 위해 촉매를 3회 재사용하였다. 매회 재사용 후, 다음 사이클 수행 전에 촉매를 수집하고, 탈이온수로 세척하여 60 ℃의 오븐에서 30분 동안 건조시켜 사용하였다.The catalyst was reused three times to analyze the reusability of the ZnFe 2 O 4 @rGO-H 2 0 (NaOH)-1 photocatalyst through photocatalytic decomposition of a 10 mg L -1 MB solution. After each reuse, the catalyst was collected before performing the next cycle, washed with deionized water, and dried in an oven at 60° C. for 30 minutes before use.
<< 실험예Experimental example 1> 상(phase) 및 형태 분석 1> Phase and shape analysis
도 2a는 흑연, 그래핀 산화물, 수열방법을 통해 제조된 ZnFe2O4@rGO 나노복합체 및 맨(bare) ZnFe2O4 NP의 XRD 패턴을 나타낸다. 그래파이트의 경우, 2θ = 26.0° (002)에서 날카로운 피크와 2θ = 54.5 ° (004)에서 낮은 세기의 피크는 육각형 흑연 구조를 나타낸다. 이 두 피크는 그래핀산화물의 XRD 패턴에서는 발견되지 않았는데, 이로써 Marcano-Tour의 방법으로 산화 및 박리공정을 통해 그래파이트가 GO로 전환되는 것을 확인하였다.Figure 2a shows the XRD pattern of graphite, graphene oxide, ZnFe 2 O 4 @rGO nanocomposite and bare ZnFe 2 O 4 NP prepared through a hydrothermal method. In the case of graphite, a sharp peak at 2θ = 26.0° (002) and a low intensity peak at 2θ = 54.5° (004) indicate a hexagonal graphite structure. These two peaks were not found in the XRD pattern of graphene oxide, whereby it was confirmed that graphite was converted to GO through oxidation and peeling processes by Marcano-Tour's method.
ZnFe2O4와 그 복합체의 XRD 패턴에 있어서 18.0, 29.7, 34.9, 42.6, 53.1, 56.3, 62.0 및 73.4° 2θ에서 (111), (220), (311), (400), (422), (511), (440) 및 (622) 격자면의 존재로 Fd-3m 공간 그룹을 갖는 입방 스피넬-형 ZnFe2O4 (JCPDS No. 22-1012) 구조의 형성이 확인되었다. 산화그래핀의 XRD 패턴과 비교하여, 2θ = 10.8° (001 면)의 피크는 ZnFe2O4@rGO-H20(NaOH) 나노복합체의 XRD 패턴에서 나타나지 않았으며, 이는 그래핀산화물 시트의 재응집(restacking)에 기인할 수 있다. 반면에, rGO는 18-25° 2θ 범위에서 특징적인 피크 (002)를 나타냈지만, 이 피크는 ZnFe2O4@rGO 나노복합체의 XRD 패턴에서는 검출되지 않았으며, 이는 스페이서로서 작용하는 ZnFe2O4 NP를 이용하여 수열방법을 통한 GO의 환원 후에 그래파이트 시트의 재응집(restacking)이 최소화됨을 나타낸다.In the XRD pattern of ZnFe 2 O 4 and its composite, 18.0, 29.7, 34.9, 42.6, 53.1, 56.3, 62.0 and 73.4° at 2θ (111), (220), (311), (400), (422), The presence of (511), (440) and (622) lattice planes confirmed the formation of cubic spinel-type ZnFe 2 O 4 (JCPDS No. 22-1012) structures with Fd-3m spatial groups. Compared with the XRD pattern of graphene oxide, the peak of 2θ = 10.8° (001 plane) did not appear in the XRD pattern of the ZnFe 2 O 4 @rGO-H 2 0 (NaOH) nanocomposite, which was found in the graphene oxide sheet. It can be due to restacking. On the other hand, rGO showed a characteristic peak (002) in the range of 18-25° 2θ, but this peak was not detected in the XRD pattern of the ZnFe 2 O 4 @rGO nanocomposite, which is ZnFe 2 O acting as a spacer. 4 It shows that the re-aggregation (restacking) of the graphite sheet is minimized after the reduction of GO through the hydrothermal method using NP.
또한, 본 발명에 따른 ZnFe2O4 NP와 ZnFe2O4@rGO 나노복합체는 5 ~ 6 사이의 초기 산성 pH로부터 1 M NaOH 용액을 사용하여 만든 탈이온수 내 GO, 금속산화물 전구체 및 아세트산나트륨의 염기성 분산액 (pH = 11)을 사용한 수열합성을 통하여 합성되었다. In addition, the ZnFe 2 O 4 NP and ZnFe 2 O 4 @rGO nanocomposite according to the present invention contains GO, metal oxide precursor, and sodium acetate in deionized water made using 1 M NaOH solution from the initial acidic pH between 5 and 6. It was synthesized through hydrothermal synthesis using a basic dispersion (pH = 11).
라만분광법은 GO와 rGO와 같은 탄소 기반 물질의 화학적 처리 과정에서 중요한 구조적 변화의 확인 및 아연페라이트의 존재를 확인하기 위한 것이다. GO의 라만스펙트럼 (도 2b)은 탄소 재료의 결함 및 무질서에 기인한 1353 cm-1 (D 밴드) 및 sp2 결합 탄소 원자의 진동과 E2g 모드의 1 차 산란에서 기인된 1594 cm-1 (G 밴드)에서 유래된 두 개의 특징적인 피크를 나타낸다. 반면에, ZnFe2O4@rGO-H20(NaOH)-1의 D 및 G 밴드는 각각 1341 및 1601 cm-1로 이동하였으며, 이는 복합체에서 GO가 환원되었음을 의미한다. ZnFe2O4@rGO-H20(NaOH)-1 (ID/IG = 1.18)에 대한 계산된 세기비율은 GO (ID/IG = 0.94)보다 더 크며, 이는 sp2 도메인의 평균크기가 수열공정 동안 그래핀산화물이 환원될 때 감소되거나 많은 새로운 흑연 도메인이 생성됨을 나타낸다. 또한, 나노복합체에 대한 ID/IG 비의 증가는 탈산소화 및 GO가 rGO 로 환원되었음을 나타낸다. Raman spectroscopy is to identify important structural changes and the presence of zinc ferrite in the chemical treatment of carbon-based substances such as GO and rGO. The Raman spectrum of GO (Fig.2b) shows the vibration of 1353 cm -1 (D band) and sp 2 bonded carbon atoms due to defects and disorders in the carbon material and 1594 cm -1 (1594 cm -1 ) due to primary scattering in the E 2g mode. G band). On the other hand, the D and G bands of ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 moved to 1341 and 1601 cm -1 , respectively, which means that GO was reduced in the complex. ZnFe 2 O 4 @ rGO-H 2 0 (NaOH) -1 the intensity ratio calculated for the (I D / I G = 1.18 ) is greater than the GO (I D / I G = 0.94), that of sp 2 domain The average size decreases when the graphene oxide is reduced during the hydrothermal process or indicates that many new graphite domains are created. In addition, an increase in the I D /I G ratio for the nanocomposite indicates deoxygenation and reduction of GO to rGO.
ZnFe2O4 (333, 494, 663 cm- 1)와 ZnFe2O4@rGO-H20(NaOH)-1 나노복합체 (320, 470, 646 cm-1) 모두 라만스펙트럼은 모두 낮은 진동수 영역에서 세 개의 피크를 보여줬는데, 이는 각각 Brillouin zone의 Γ-point에서 ZnFe2O4의 F2g (2), F2g (3) 및 A1g 광학 음자(phonon) 모드에 해당한다. 페라이트에서 600 cm-1 이상의 음자모드는 4면체 AO4 그룹의 산소 원자의 운동을 나타내지만, 다른 낮은 진동수모드는 8 면체 BO6 사이트의 특성에 기인한다. 상기와 같이 이러한 광학 음자 모드의 존재는 스피넬 구조에 대한 높은 안정성을 나타낸다.Both ZnFe 2 O 4 (333, 494, 663 cm - 1 ) and ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 nanocomposite (320, 470, 646 cm -1 ) all have low frequency Raman spectrum. Three peaks were shown in, respectively, corresponding to the F 2g (2), F 2g (3) and A 1g optical phonon modes of ZnFe 2 O 4 at the Γ-point of the Brillouin zone. In ferrite, the negative mode of 600 cm -1 or more indicates the motion of the oxygen atom of the tetrahedral AO4 group, but other low frequency modes are due to the characteristics of the octahedral BO6 site. As described above, the presence of this optical negative mode indicates high stability for the spinel structure.
GO 표면의 산소작용기의 감소에 대한 증거는 도 3에서와 같이 GO 및 ZnFe2O4@rGO-H20(NaOH) 나노복합체의 FT-IR 스펙트럼으로부터 얻을 수 있다. GO 스펙트럼에서, COOH 그룹의 C=O 신축진동 (1713 cm-1), COOH 그룹의 O-H 변형진동 (1624 cm-1), 3차 C-OH의 O-H 변형진동 (1397 cm-1), 에폭시기의 C-O 신축진동 (1047 cm- 1)과 같이 산소작용기에 대한 특징적인 피크가 관찰되었다. 또한, 3222 cm-1을 중심으로 하는 2900 내지 3700 cm-1 범위의 넓은 흡수피크는 O-H 신축진동에 기인한다. 반면에, 수열 처리 후, C=O의 피크는 소실되고, O-H 및 C-O의 피크 세기는 감소하였으며, 이는 GO의 부분 환원 또는 산소를 포함하는 작용기의 제거를 나타내며, 이로써 나노복합체에서 환원된 그래핀의 형성을 확인할 수 있다. 또한, 낮은 진동수에서 ZnFe2O4@rGO-H20(NaOH)-1 (531 ~ 400 cm- 1)과 ZnFe2O4@rGO-H20(NaOH)-2 (534 ~ 400 cm-1) 나노복합체의 두 개의 강한 흡수피크는 각각 Fe-O 결합과 Zn-O 결합의 신축진동에 해당되며, ZnFe2O4@rGO-H20(NaOH)-1과 ZnFe2O4@rGO-H20(NaOH)-2 복합체의 1581과 1566 cm-1의 피크는 산화되지 않은 탄소 골격의 신축진동에 해당한다.Evidence for the reduction of the oxygen functional groups on the GO surface can be obtained from the FT-IR spectrum of the GO and ZnFe 2 O 4 @rGO-H 2 0 (NaOH) nanocomposite as shown in FIG. 3. In the GO spectrum, the C=O stretching vibration of the COOH group (1713 cm -1 ), the OH deformation vibration of the COOH group (1624 cm -1 ), the OH deformation vibration of the tertiary C-OH (1397 cm -1 ), the epoxy group Characteristic peaks for oxygen functional groups were observed, such as CO stretching vibration (1047 cm - 1 ). In addition, the wide absorption peak in the range of 2900 to 3700 cm -1 centered on 3222 cm -1 is due to the OH stretching vibration. On the other hand, after hydrothermal treatment, the peak of C=O disappeared, and the peak intensity of OH and CO decreased, indicating partial reduction of GO or removal of functional groups containing oxygen, thereby reducing graphene in the nanocomposite. The formation of can be confirmed. Also, ZnFe 2 O at a low frequency 4 @ rGO-H 2 0 ( NaOH) -1 (531 ~ 400 cm - 1) and ZnFe 2 O 4 @ rGO-H 2 0 (NaOH) -2 (534 ~ 400 cm - 1 ) The two strong absorption peaks of the nanocomposite correspond to the expansion and contraction vibration of the Fe-O bond and the Zn-O bond, respectively, and ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 and ZnFe 2 O 4 @rGO The peaks at 1581 and 1566 cm -1 of the -H 2 0 (NaOH)-2 complex correspond to the stretching vibration of the unoxidized carbon skeleton.
ZnFe2O4@rGO 나노복합체의 표면화학적 조성과 전자상태는 도 4의 XPS 스펙트럼에서 볼 수 있다. 도 4a의 스펙트럼은 Zn 2p, Fe 2p, O 1s 및 C 1s 에너지 영역의 존재를 보여준다. 도 4b의 고분해능 Zn 2p 스펙트럼은 각각 Zn 2p1 /2와 Zn 2p3 /2에 해당되는 1044.78와 1021.58eV를 중심으로 두 개의 주요 피팅 피크를 보여 주며, 이는 ZnFe2O4에서 Zn (II) 산화상태를 나타낸다. 도 4c 스펙트럼에서, 712.98 및 711.08eV에서의 Fe2p3 /2에 대한 결합에너지는 각각 사면체 및 팔면체 부위에 대응하는 반면, 결합에너지에서의 피크인 726.38 및 724.98eV는 Fe 2p1 /2 와 일치한다. 또한, 733.58과 719.48 eV의 두 신호는 나노복합체의 ZnFe2O4에 Fe3 +만 존재함을 의미한다. 도 4d의 O 1s 스펙트럼은 533.08, 531.68 및 530.18 eV의 세 가지 다른 피크로 역회선(deconvolution) 될 수 있다. 530.18 eV의 O 1s 결합에너지는 Fe와 Zn (Fe-O와 Zn-O로 표시됨)과의 격자 산소 결합에 해당된다. 또한, 결합에너지가 533.08 및 531.68 eV 인 피크는 그래핀 (C-O 및 C=O)의 C 원자와 결합된 잔여 산소를 포함하는 그룹의 존재 및 각각 O2 - ads와 O- ads와 같은 표면 흡착된 산소 종에 해당된다. 이러한 촉매 표면상에 화학흡착된 산소는 산화반응에서 중요한 역할을 하는 활성산소이다.The surface chemical composition and electronic state of the ZnFe 2 O 4 @rGO nanocomposite can be seen in the XPS spectrum of FIG. 4. The spectrum of FIG. 4A shows the presence of the
XPS는 또한 수열반응을 통한 환원과정에서 GO의 상당한 탈산소화를 확인할 수 있다. 도 4e 및 도 4f는 각각 ZnFe2O4@rGO-H20(NaOH)-1 나노복합체 및 GO의 전형적인 C 1s 스펙트럼을 보여준다. 도 3f과 같이, GO의 C 1s 시그널에 대한 피크는 284.48eV의 비 산소 링 C-C 및 C=C 결합, 285.18eV의 C-O (에폭시 및 하이드록실) 결합, 287.08 eV에서 C=O (카르보닐) 결합, 288.68 eV에서 O-C=O (카르복실레이트) 결합을 나타내는 여러 시그널이 역회선 되어 있다. 그러나 도 4e와 같이 나노복합체의 경우, C-O와 O-C=O의 피크 세기는 상당히 감소한 반면, C-C와 C=C의 피크 세기는 GO와 비교하여 현저하게 증가하였으며, 나노복합체의 C=O 피크는 더이상 C 1s 스펙트럼에서 확인할 수 없었다.XPS can also confirm significant deoxygenation of GO during reduction through hydrothermal reaction. 4E and 4F show
도 5는 ZnFe2O4-H20(NaOH) NP 및 ZnFe2O4@rGO-H20(NaOH)-1 나노복합체의 FE-SEM 및 HRTEM 이미지 및 선택된 영역 전자 회절 (selected-area electron diffraction; SAED) 패턴을 나타낸다. SEM (도 5a 및 b)과 HRTEM (도 5c 및 d) 이미지는 ZnFe2O4 NP가 rGO 시트 표면에 균일하게 증착된 나노복합체의 하이브리드 구조를 나타낸다. ZnFe2O4 NP와 그래핀 시트 사이의 강한 상호작용은 빠른 전자수송을 가능하게 하고 전자와 정공의 분리를 향상시킨다. 평균적으로, ZnFe2O4 NP는 약 12 nm 크기인 반면, rGO 시트의 표면상에 증착된 ZnFe2O4 NP는 크기는 약 10 nm 미만이어서 ZnFe2O4 NP와 그래핀 시트 사이의 상호작용이 결정성 ZnFe2O4 NP의 응집을 어느 정도 제한한다는 것을 알 수 있다. 또한, 아세테이트 분자는 보호제 역할을 하여 나노 크기의 ZnFe2O4 NP의 형성에 기여하며, 생성된 나노 결정을 안정화시켜 큰 결정의 성장을 방해한다.FIG. 5 is a FE-SEM and HRTEM image of ZnFe 2 O 4 -H 2 0 (NaOH) NP and ZnFe 2 O 4 @rGO-H 2 0 (NaOH)-1 nanocomposite and selected area electron diffraction (selected-area electrons). diffraction; SAED) pattern. SEM (Figs. 5a and b) and HRTEM (Figs. 5c and d) images show the hybrid structure of the nanocomposite in which ZnFe 2 O 4 NP is uniformly deposited on the surface of the rGO sheet. The strong interaction between the ZnFe 2 O 4 NP and the graphene sheet enables rapid electron transport and improves the separation of electrons and holes. On average, ZnFe 2 O 4 NPs are about 12 nm in size, whereas ZnFe 2 O 4 NPs deposited on the surface of rGO sheets are less than about 10 nm in size, so the interaction between ZnFe 2 O 4 NPs and graphene sheets. It can be seen that the aggregation of this crystalline ZnFe 2 O 4 NP is limited to some extent. In addition, the acetate molecule acts as a protective agent, contributing to the formation of nano-sized ZnFe 2 O 4 NPs, and stabilizing the generated nanocrystals to hinder the growth of large crystals.
도 5e와 같이, ZnFe2O4 NP의 HR-TEM 이미지에서 (400), (222) 및 (220) 면의 면간 간격에 상응하는 0.207, 0.243 및 0.294 nm의 근사 d-간격을 갖는 잘 분해 된 격자줄무늬가 관찰되었다. 마찬가지로 도 5f에서 d-간격이 0.255와 0.291 nm 인 격자줄무늬가 ZnFe2O4@rGO 복합체의 HRTEM 이미지에서 관찰되었는데, 이것은 스피넬 ZnFe2O4 상에서 각각 (311) 및 (220)면의 면간 간격에 해당한다. 도 5g 및 5h의 SAED 패턴은 ZnFe2O4 NP 및 ZnFe2O4@rGO-H20(NaOH)-1의 높은 결정성을 추가로 확인할 수 있다. 이러한 결정성은 높은 광촉매활성을 나타낼 것이다.As shown in Fig.5e, in the HR-TEM image of ZnFe 2 O 4 NP, the well resolved with approximate d -spacings of 0.207, 0.243 and 0.294 nm corresponding to the interplanar spacing of (400), (222) and (220) planes. Grid stripes were observed. Similarly, in FIG. 5f, lattice stripes with d -intervals of 0.255 and 0.291 nm were observed in the HRTEM image of the ZnFe 2 O 4 @rGO composite, which was observed in the interplanar spacing of the (311) and (220) planes on the spinel ZnFe 2 O 4, respectively. It corresponds. The SAED pattern of FIGS. 5G and 5H can further confirm the high crystallinity of ZnFe 2 O 4 NP and ZnFe 2 O 4 @rGO-H 2 0 (NaOH)-1. This crystallinity will show high photocatalytic activity.
<실험예 2> BET 비표면적 및 기공크기 분포<Experimental Example 2> BET specific surface area and pore size distribution
ZnFe2O4-H2O(NaOH)와 ZnFe2O4@rGO-H20(NaOH)-1의 N2 흡착-탈착 등온선은 도 6a 및 c에 각각 나타내었다. IUPAC 분류에 따르면, 두 시료는 메조기공(mesoporous)의 특성을 보여주며, IV 등온선 유형을 나타냈다. 이력곡선(hysteresis loop)의 형태는 Type H2이며, 이는 기공의 무작위 분포와 상호 연결된 기공시스템의 존재를 나타낸다. ZnFe2O4@rGO-H20(NaOH)-1 복합체의 Brunauer-Emmett-Teller (BET) 비표면적 (SBET)은 141.3 m2 g-1로 계산되었는데, 이는 ZnFe2O4-H2O(NaOH)가 113.8m2 g-1 로 계산된 것과 비교하여 높게 나타났다. 이러한 큰 표면적은 광촉매반응 동안 흡착/반응 부위를 더 많이 제공하여 광촉매 활성을 향상시킬 수 있을 것이다. 또한, 도 6b 및 d는 각각 ZnFe2O4-H2O(NaOH)와 ZnFe2O4@rGO-H20(NaOH)-1에 상응하는 Barrett-Joyner-Halenda (BJH) 흡착기공 크기분포(PSD)를 나타내며, 여기서 평균 기공직경은 각각 12.4 및 5.2 nm로, 합성된 물질에 메조기공이 풍부하게 존재함을 확인하였다.The N 2 adsorption-desorption isotherms of ZnFe 2 O 4 -H 2 O(NaOH) and ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 are shown in FIGS. 6a and c, respectively. According to the IUPAC classification, the two samples showed mesoporous properties and exhibited IV isotherm type. The type of hysteresis loop is Type H2, which indicates the presence of a random distribution of pores and interconnected pore systems. The Brunauer-Emmett-Teller (BET) specific surface area (S BET ) of the ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 complex was calculated to be 141.3 m 2 g -1 , which is ZnFe 2 O 4 -H 2 O(NaOH) was higher than that calculated as 113.8m 2 g -1 . Such a large surface area may improve photocatalytic activity by providing more adsorption/reaction sites during the photocatalytic reaction. 6b and d are Barrett-Joyner-Halenda (BJH) adsorption pore size distributions corresponding to ZnFe 2 O 4 -H 2 O (NaOH) and ZnFe 2 O 4 @rGO-H 2 0 (NaOH)-1, respectively. (PSD), where the average pore diameters were 12.4 and 5.2 nm, respectively, and it was confirmed that the synthesized material had abundant mesopores.
<실험예 3> 광학 및 전기화학적 분석<Experimental Example 3> Optical and electrochemical analysis
물질의 광 흡수 범위는 광촉매, 특히 태양광에 의한 광분해와 관련된 응용 분야에서 상당히 중요한 역할을 한다. 도 7a과 같이, UV-vis-NIR 분광 광도계를 사용하여 시료의 흡광도를 조사하였다. ZnFe2O4-H2O(NaOH)는 약 710 nm에서 흡광도가 낮아지며, 가시 영역에서 넓은 흡수를 보였는데, 이는 약 1.75 eV의 밴드갭에 해당한다. 그러나 ZnFe2O4-H2O(NaOH)와 비교하여 ZnFe2O4@rGO-H20(NaOH)-1, ZnFe2O4@rGO-H20(NaOH)-2의 흡광도는 상당히 증가되었다. 이러한 2개의 ZnFe2O4@ rGO 나노복합체에 대한 가시광선 흡수의 향상은 주로 rGO의 도입에 의해 발생된 것으로, 이는 태양광에서 활용도가 우수할 것이다. The light absorption range of a material plays a significant role in photocatalysts, especially in applications involving photolysis by sunlight. As shown in Fig. 7a, the absorbance of the sample was investigated using a UV-vis-NIR spectrophotometer. ZnFe 2 O 4 -H 2 O (NaOH) has a low absorbance at about 710 nm and shows a wide absorption in the visible region, which corresponds to a band gap of about 1.75 eV. However, compared to ZnFe 2 O 4 -H 2 O(NaOH), the absorbance of ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 and ZnFe 2 O 4 @rGO-H 2 0(NaOH)-2 is considerably Increased. The improvement of visible light absorption for these two ZnFe2O4@ rGO nanocomposites is mainly caused by the introduction of rGO, which will have excellent utility in sunlight.
그래핀이 복합재료의 표면적을 향상시키는 것 외에도, 또 다른 중요한 역할은 전자수용체 및 광유도 전자의 분리 및 이동을 촉진시키는 전달채널로서 작용하는 것이다. 도 7b와 같이, ZnFe2O4@rGO-H20(NaOH)-1 시료의 EIS 플롯의 반원은 rGO의 도입에 의해 더 작아졌으며, 이는 고체상태의 계면-층 저항 및 표면 전하전달저항의 감소를 나타낸다. 전반적으로, 나노복합체에서의 그래핀의 전자수용 및 이동특성은 전하 재조합의 억제에 기여할 수 있으며, 이는 광촉매 활성에 더 높은 비율로 이용될 수 있다. 그러나 첨가된 산화 그래핀의 양을 두 배로 늘리면 ZnFe2O4@rGO-H20(NaOH)-2 시료의 반원이 더 커져 최상의 전하전달능력을 위한 최적의 rGO 함량이 있음을 알 수 있다. ZnFe2O4@rGO-H20(NaOH)-2에서 더 높은 전하전달저항은 과도한 rGO에 기인한 것으로, 이는 나노복합체의 내부에서 표면으로 전자의 이동을 방해할 수 있는 광 생성 전하의 새로운 재조합의 중심으로 작용할 수 있다. 또한, rGO가 과도하게 적재되면 반도체 표면의 활성 부위를 막아 빛이 반응이 일어나는 광촉매 표면에 도달하는 것을 막을 수 있다.In addition to improving the surface area of graphene, another important role is to act as a transport channel that promotes the separation and movement of electron acceptors and light-induced electrons. As shown in FIG. 7B, the semicircle of the EIS plot of the ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 sample was smaller by the introduction of rGO, which is the solid state interface-layer resistance and surface charge transfer resistance. Indicates a decrease. Overall, the electron accepting and transport properties of graphene in the nanocomposite can contribute to the inhibition of charge recombination, which can be used at a higher ratio to photocatalytic activity. However, if the amount of graphene oxide added is doubled, the semicircle of the ZnFe 2 O 4 @rGO-H 2 0 (NaOH)-2 sample becomes larger, indicating that there is an optimal rGO content for the best charge transfer capability. The higher charge transfer resistance in ZnFe 2 O 4 @rGO-H 2 0(NaOH)-2 is due to excessive rGO, which is a novel photogenerated charge that can hinder the transfer of electrons from the inside of the nanocomposite to the surface. It can act as a center of recombination. In addition, when rGO is excessively loaded, it is possible to prevent light from reaching the photocatalyst surface where the reaction occurs by blocking active sites on the semiconductor surface.
광전류 측정은 불소가 도핑된 산화주석(FTO) 전극 위에 드롭캐스팅 (drop casting) 한 후, ZnFe2O4-H2O(NaOH) 나노입자와 ZnFe2O4@rGO 복합체에 대해 0.5 M Na2SO4 수용액에서 포화 칼로멜전극 (saturation calomel electrode, SCE)에 대한 0.3 V 전위로 시뮬레이션된 태양광을 여러 차례 on-off 사이클로 조사하여 수행되었다. ZnFe2O4@rGO-H20(NaOH) 전극의 광전류는 ZnFe2O4-H2O(NaOH) 전극의 광전류의 두 배였으며, 이는 ZnFe2O4 NP와 그래핀 시트 사이의 전자 상호 작용으로 인해 광 유도된 전자와 정공의 분리가 상당히 증가되었음을 나타낸다(도 7c).Photocurrent measurement is performed by drop casting on a fluorine-doped tin oxide (FTO) electrode, and then 0.5 M Na2SO4 aqueous solution for ZnFe 2 O 4 -H 2 O (NaOH) nanoparticles and ZnFe 2 O 4 @rGO composite. The simulated sunlight with a potential of 0.3 V against a saturation calomel electrode (SCE) was irradiated with several on-off cycles. The photocurrent of the ZnFe 2 O 4 @rGO-H 2 0 (NaOH) electrode was twice that of the ZnFe 2 O 4 -H 2 O (NaOH) electrode, which was ZnFe 2 O 4 It shows that the separation of light-induced electrons and holes is significantly increased due to the electron interaction between the NP and the graphene sheet (Fig. 7c).
ZnFe2O4-H2O(NaOH) NP 및 ZnFe2O4@rGO-H20(NaOH) 복합체의 광학 특성을 분석하기 위해 325 nm 레이저의 여기하에 실온에서 광발광 분광분석을 수행하였다. 개념적으로 물질에 대한 PL 방출세기가 높을수록 광 생성된 전자와 정공의 재결합속도가 빨라져 광촉매 활성을 낮춘다. 도 7d에서 보면, ZnFe2O4@rGO-H20(NaOH)-1 및 ZnFe2O4@rGO-H20(NaOH)-2 복합체의 방출 강도는 각각 ZnFe2O4-H2O(NaOH) 보다 23 및 17 % 낮았다. 이는 복합체가 ZnFe2O4-H2O(NaOH) NP와 비교하여 더 나은 전하 분리능을 가짐을 확인하였다. 그러나, 두 복합체의 방출 세기를 비교하면 ZnFe2O4@rGO-H20(NaOH)-2 복합체의 가장 낮은 세기와 비교하여 약 7 %의 매우 작은 차이가 있음을 알 수 있었으며, 이는 ZnFe2O4에서 GO의 두 배의 첨가는 전하 분리를 크게 향상시키지 않음을 확인하였다.In order to analyze the optical properties of the ZnFe 2 O 4 -H 2 O (NaOH) NP and ZnFe 2 O 4 @rGO-H 2 0 (NaOH) composites, photoluminescence spectroscopy was performed at room temperature under excitation of a 325 nm laser. Conceptually, the higher the PL emission intensity for a material, the faster the recombination rate of photogenerated electrons and holes increases, thereby lowering the photocatalytic activity. 7D, the emission intensity of the ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 and ZnFe 2 O 4 @rGO-H 2 0(NaOH)-2 complexes are respectively ZnFe 2 O 4 -H 2 O 23 and 17% lower than (NaOH). It was confirmed that the composite had better charge resolution compared to ZnFe 2 O 4 -H 2 O (NaOH) NP. However, when comparing the emission intensity of the two complexes, it was found that there is a very small difference of about 7% compared to the lowest intensity of the ZnFe 2 O 4 @rGO-H 2 0(NaOH)-2 complex, which is ZnFe 2 In O 4 It was confirmed that the addition of twice the GO did not significantly improve the charge separation.
<실험예 4> 광촉매 활성 및 안정성 측정<Experimental Example 4> Photocatalytic activity and stability measurement
EIS, 광전류 반응 및 PL의 결과를 토대로 수열 합성으로 합성된 물질을 촉매제로 사용하여 태양광 조사 하에서 10 mg L-1 MB 및 RhB 용액의 광촉매에 의한 분해를 측정하였다. MB 및 RhB는 광촉매분해를 위한 오염물질 모델이며, 섬유폐수에 있는 대표적인 유기염료이다. Based on the results of EIS, photocurrent reaction, and PL, the material synthesized by hydrothermal synthesis was used as a catalyst to measure the photocatalytic decomposition of 10 mg L -1 MB and RhB solutions under sunlight irradiation. MB and RhB are pollutant models for photocatalytic decomposition, and are representative organic dyes in textile wastewater.
도 7e와 같이 태양광 조사 하에서, MB는 60분 후에 6.6 % 자기분해를 보였다. 또한, ZnFe2O4-H2O(NaOH) NP (0.5 g L-1)를 첨가하면 태양광 조사 하에서 60 분 후에 MB가 12.8 % 저하되었다. 반면에, MB를 분해하는 ZnFe2O4-H2O(NaOH) NP의 광촉매 활성은 ZnFe2O4@rGO-H20(NaOH)-1(0.5 g L-1)에서 rGO의 도입에 의해 60 분 후에 94.2 % 으로 상당히 증가되었다. ZnFe2O4@rGO-H20(NaOH)-1의 촉매 적재량을 0.5 에서 0.25 g L-1로 감소시킨 경우 MB 용액의 64.7 %가 분해되었다.Under solar irradiation as shown in FIG. 7e, MB showed 6.6% autolysis after 60 minutes. In addition, when ZnFe 2 O 4 -H 2 O (NaOH) NP (0.5 g L -1 ) was added, the MB decreased by 12.8% after 60 minutes under sunlight irradiation. On the other hand, the photocatalytic activity of ZnFe 2 O 4 -H 2 O(NaOH) NP that decomposes MB is due to the introduction of rGO in ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 (0.5 g L -1 ). It increased significantly to 94.2% after 60 minutes. When the catalyst loading of ZnFe 2 O 4 @rGO-H 2 0(NaOH) -1 was reduced from 0.5 to 0.25 g L -1 , 64.7% of the MB solution was decomposed.
또한, ZnFe2O4@rGO-H20(NaOH)-1을 0.5 g L-1 투입하여 RhB 용액 10mg L-1을 분해시켰을 때 태양광 조사 60 분 후 분해효율은 49 %로 나타났다. 이러한 RhB에 대한 촉매의 낮은 광촉매 분해활성은 RhB 분자의 크고 복잡한 구조 때문이다. 또한, 도 7e의 삽입된 도면은 촉매가 자성의 특성을 가짐을 보여준다.In addition, when 0.5 g L -1 of ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 was added to decompose 10 mg L -1 of the RhB solution, the decomposition efficiency was 49% after 60 minutes of sunlight irradiation. The low photocatalytic decomposition activity of the catalyst for RhB is due to the large and complex structure of the RhB molecule. In addition, the inserted diagram of FIG. 7E shows that the catalyst has magnetic properties.
도 7f의 제거(scavenging) 결과는 태양광 조사 하에서의 MB의 광분해가 각각 이소프로필알콜, 탄산수소나트륨 및 p-벤조퀴논의 첨가로 4.6, 23.2 및 70.8 % 감소되었음을 보여준다. 이것은 염료의 분해에 관여하는 주요 활성 종이 슈퍼옥사이드(superoxide) 라디칼 및 정공임을 의미한다. IPA의 첨가는 분해공정에 거의 영향을 미치지 않으며, 이는 하이드록시 라디칼이 MB의 광분해에 결정적인 역할을 하지 않음을 의미한다.The scavenging results of FIG. 7F show that the photolysis of MB under sunlight irradiation was reduced by 4.6, 23.2 and 70.8% by the addition of isopropyl alcohol, sodium hydrogen carbonate and p-benzoquinone, respectively. This means that the main active species involved in the decomposition of the dye are superoxide radicals and holes. The addition of IPA has little effect on the decomposition process, which means that hydroxy radicals do not play a critical role in the photolysis of MB.
ZnFe2O4@rGO-H20(NaOH)-1 나노복합체를 사용한 MB의 광분해의 주요 메커니즘은 하기 반응식 1 및 도 8에 의해 하기와 같이 설명할 수 있다 (도 8).The main mechanism of photolysis of MB using the ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 nanocomposite can be explained as follows by the following
[반응식 1][Scheme 1]
흡착과정에서, MB 염료 분자는 벌크 용액에서 나노복합체 표면으로 이동하고, 염료와 그래핀 시트의 방향족 영역 사이의 π-π 접합을 통해 오프셋(offset) 대면 방향에 흡착된다. MB 염료와 같은 유기화합물 수용액의 존재 하에서 태양광을 나노복합체에 조사할 때, 광자에 의한 ZnFe2O4 NPs의 여기는 전자/정공 (eCB -/hVB +) 쌍을 발생시킨다(식 1). 광여기된 전자는 ZnFe2O4의 전도대에서 퍼콜레이션(percolaton) 메카니즘 (식 2)을 통해 그래핀 시트의 표면으로 쉽게 이동한 후 그래핀 층의 표면에 흡착된 O2 분자와 반응하여 O2 ˙- 라디칼을 발생시켜(식 3) MB 분자를 산화시키도록 한다 (식 4). ZnFe2O4 와 그래핀 사이의 강한 계면접촉 때문에, 그래핀 시트로의 전자의 직접 이동이 가속화될 수 있으며, 이는 광생성 전하의 수명을 증가시키고, ZnFe2O4의 양자효율을 높일 수 있다. 더욱이 ZnFe2O4의 가전자대의 반응성 정공은 ZnFe2O4의 VB 포텐셜이 표면에 흡착된 H2O를 히드록실 라디칼로 산화시키는데 필요한 포텐셜보다 낮기 때문에 직접적으로 MB를 산화시킬 수 있다 (식 5). 따라서 O2 ˙- 라디칼의 생성과 반응성 정공의 존재 때문에 MB는 H2O, CO2 및 기타 물질로 분해될 수 있으며, 전자전달과정으로 ZnFe2O4@rGO-H20(NaOH)-1 나노복합체에서 전하 재조합이 억제되어 광촉매 성능의 효율이 크게 향상되었다.In the adsorption process, MB dye molecules migrate from the bulk solution to the surface of the nanocomposite, and are adsorbed in an offset facing direction through the π-π junction between the dye and the aromatic region of the graphene sheet. In the presence of an organic compound solution, such as a MB dye when irradiated with sunlight in the nanocomposite, this is the electron / hole of ZnFe 2 O 4 NPs by the photon-to generate a (e CB / h VB +) pair (formula 1) . Photoexcitation of electrons ZnFe 2 O 4 In the conduction band of the through percolation (percolaton) mechanism (Equation 2) yes then easily move to the surface of the fin sheet yes react with the adsorbed O 2 molecules on the surface of the pin layer O 2 ˙- Generate radicals (Equation 3) to oxidize MB molecules (Equation 4). Because of the strong interfacial contact between ZnFe 2 O 4 and graphene, the direct transfer of electrons to the graphene sheet can be accelerated, which can increase the life of photogenerated charges and increase the quantum efficiency of ZnFe 2 O 4 . Further reactive hole in the valence band of ZnFe 2 O 4 can be oxidized directly to the MB because VB potential of ZnFe 2 O 4 is to oxidize the H 2 O adsorbed to the surface by a hydroxyl radical is lower than that needed potential (equation 5 ). Therefore, due to the generation of O 2 ˙- radicals and the presence of reactive holes, MB can be decomposed into H 2 O, CO 2 and other substances, and ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 by electron transfer process. Charge recombination was suppressed in the nanocomposite, which greatly improved the efficiency of photocatalytic performance.
또한, 광분해를 위한 ZnFe2O4@rGO-H20(NaOH)-1 나노복합체의 안정성을 확인하기 위해, 촉매는 태양광 조사 하에서 MB 염료의 분해를 위해 3회 재사용되었다. In addition, in order to confirm the stability of the ZnFe 2 O 4 @rGO-H 2 0(NaOH)-1 nanocomposite for photolysis, the catalyst was reused three times for decomposition of MB dye under sunlight irradiation.
그 결과 두 번째 및 세 번째 사이클에서 광촉매 분해효율은 각각 92.7 및 91.2 % 이었으며, 이는 재처리 동안 촉매량의 손실 및 광분해 공정 동안 촉매의 응집 가능성 때문일 것이다.As a result, the photocatalytic decomposition efficiencies in the second and third cycles were 92.7 and 91.2%, respectively, probably due to the loss of catalyst amount during reprocessing and the possibility of agglomeration of the catalyst during the photolysis process.
Claims (10)
산화그래핀(GO)을 탈이온수에 분산시켜 GO 분산액을 준비하는 단계;
상기 제1혼합용액에 아세트산나트륨(sodium acetate)를 첨가하여 제2혼합용액을 준비하는 단계;
상기 제2혼합용액에 GO 분산액을 첨가하여 제3혼합용액을 준비하는 단계;
상기 제3혼합용액에 수산화나트륨(sodium hydroxide)를 첨가하여 현탁액을 준비하는 단계; 및
상기 현탁액을 열처리하여 환원된 산화그래핀(rGO) 상에 아연페라이트(ZnFe2O4) 나노입자가 결합된 나노복합체(ZnFe2O4@rGO)를 수득하는 단계;
를 포함하는, ZnFe2O4@rGO 나노복합체 광촉매 제조방법.Preparing a first mixed solution by dissolving a zinc precursor and an iron precursor in deionized water;
Preparing a GO dispersion by dispersing graphene oxide (GO) in deionized water;
Preparing a second mixed solution by adding sodium acetate to the first mixed solution;
Preparing a third mixed solution by adding a GO dispersion to the second mixed solution;
Preparing a suspension by adding sodium hydroxide to the third mixed solution; And
Heat-treating the suspension to obtain a nanocomposite (ZnFe 2 O 4 @rGO) in which zinc ferrite (ZnFe 2 O 4 ) nanoparticles are bonded on reduced graphene oxide (rGO);
Containing, ZnFe 2 O 4 @rGO nanocomposite photocatalyst manufacturing method.
상기 아연 전구체는,
질산아연(II)(Zn(NO3)2), 염화아연(ZnCl2), 황산아연(ZnSO4) 및 초산아연(Zn(CH3COO)2)으로 이루어진 군에서 선택되는 어느 하나인 것을 특징으로 하는, ZnFe2O4@rGO 나노복합체 광촉매 제조방법.The method of claim 1,
The zinc precursor,
Zinc nitrate (II) (Zn(NO 3 ) 2 ), zinc chloride (ZnCl 2 ), zinc sulfate (ZnSO 4 ), and zinc acetate (Zn(CH 3 COO) 2 ) characterized by being any one selected from the group consisting of As, ZnFe 2 O 4 @rGO nanocomposite photocatalyst manufacturing method.
상기 철 전구체는,
질산철(Ⅲ)(Fe(NO3)3), 염화철(FeCl3), 황산철(FeSO4) 및 초산철(Fe(CH3COO)2)로 이루어진 군에서 선택되는 어느 하나인 것을 특징으로 하는, ZnFe2O4@rGO 나노복합체 광촉매 제조방법.The method of claim 1,
The iron precursor,
It characterized in that any one selected from the group consisting of iron nitrate (III) (Fe(NO 3 ) 3 ), iron chloride (FeCl 3 ), iron sulfate (FeSO 4 ) and iron acetate (Fe(CH 3 COO) 2 ) To, ZnFe 2 O 4 @rGO nanocomposite photocatalyst manufacturing method.
상기 아연 전구체와 철 전구체는 1:2의 몰비로 용해시키는 것을 특징으로 하는, ZnFe2O4@rGO 나노복합체 광촉매 제조방법.The method of claim 1,
The zinc precursor and the iron precursor are dissolved in a molar ratio of 1:2, ZnFe 2 O 4 @rGO nanocomposite photocatalyst manufacturing method.
상기 산화그래핀은 탈이온수 100 중량부에 대해 20 내지 50 중량부를 포함하는 것을 특징으로 하는, ZnFe2O4@rGO 나노복합체 광촉매 제조방법.The method of claim 1,
The graphene oxide is characterized in that it contains 20 to 50 parts by weight based on 100 parts by weight of deionized water, ZnFe 2 O 4 @rGO nanocomposite photocatalyst manufacturing method.
상기 제3혼합용액에 수산화나트륨을 첨가하여 현탁액을 준비하는 단계는,
수산화나트륨을 첨가하여 염기성 pH로 조절하는 것을 특징으로 하는, ZnFe2O4@rGO 나노복합체 광촉매 제조방법.The method of claim 1,
The step of preparing a suspension by adding sodium hydroxide to the third mixed solution,
ZnFe 2 O 4 @rGO nanocomposite photocatalyst manufacturing method, characterized in that by adding sodium hydroxide to adjust the basic pH.
상기 현탁액을 열처리하는 단계는,
150 내지 250℃에서 5 내지 15시간 수행하는 것을 특징으로 하는, ZnFe2O4@rGO 나노복합체 광촉매 제조방법.The method of claim 1,
The step of heat treating the suspension,
ZnFe 2 O 4 @rGO nanocomposite photocatalyst manufacturing method, characterized in that carried out for 5 to 15 hours at 150 to 250 ℃.
아연페라이트(ZnFe2O4) 나노입자의 평균 입자 크기는 1 내지 15nm인 것을 특징으로 하는, ZnFe2O4@rGO 나노복합체 광촉매.The method of claim 1,
Zinc ferrite (ZnFe 2 O 4 ) ZnFe 2 O 4 @rGO nanocomposite photocatalyst, characterized in that the average particle size of the nanoparticles is 1 to 15nm.
상기 ZnFe2O4@rGO 나노복합체는,
평균 직경 3 내지 15nm의 기공을 포함하는 것을 특징으로 하는, ZnFe2O4@rGO 나노복합체 광촉매.The method of claim 1,
The ZnFe 2 O 4 @rGO nanocomposite,
ZnFe 2 O 4 @rGO nanocomposite photocatalyst comprising pores having an average diameter of 3 to 15 nm.
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| CN112371171A (en) * | 2020-11-19 | 2021-02-19 | 北华大学 | Preparation and application of bismuth ferrite loaded graphene composite material |
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| CN112371171A (en) * | 2020-11-19 | 2021-02-19 | 北华大学 | Preparation and application of bismuth ferrite loaded graphene composite material |
| CN112371171B (en) * | 2020-11-19 | 2023-03-24 | 北华大学 | Preparation and application of bismuth ferrite loaded graphene composite material |
| CN114604957A (en) * | 2022-03-17 | 2022-06-10 | 中南大学 | Method for treating organic dye and heavy metal ions in water body |
| CN114669301A (en) * | 2022-04-19 | 2022-06-28 | 华北理工大学 | Three-dimensional graphene gel composite material and preparation and application methods thereof |
| CN114985000A (en) * | 2022-05-05 | 2022-09-02 | 宁夏医科大学 | Preparation method and application of MCM-48 composite catalyst |
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