CN109078645B - Photocatalyst coated with Z-shaped structure and preparation method and application thereof - Google Patents
Photocatalyst coated with Z-shaped structure and preparation method and application thereof Download PDFInfo
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- 239000011941 photocatalyst Substances 0.000 title claims abstract description 63
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 229940043267 rhodamine b Drugs 0.000 claims abstract description 99
- PYWVYCXTNDRMGF-UHFFFAOYSA-N rhodamine B Chemical compound [Cl-].C=12C=CC(=[N+](CC)CC)C=C2OC2=CC(N(CC)CC)=CC=C2C=1C1=CC=CC=C1C(O)=O PYWVYCXTNDRMGF-UHFFFAOYSA-N 0.000 claims abstract description 97
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- 230000001699 photocatalysis Effects 0.000 claims abstract description 25
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- 239000000843 powder Substances 0.000 claims description 44
- 229910019901 yttrium aluminum garnet Inorganic materials 0.000 claims description 35
- 239000000243 solution Substances 0.000 claims description 25
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- 238000003756 stirring Methods 0.000 claims description 15
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 8
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- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 7
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 7
- 238000001354 calcination Methods 0.000 claims description 7
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- YBMRDBCBODYGJE-UHFFFAOYSA-N germanium oxide Inorganic materials O=[Ge]=O YBMRDBCBODYGJE-UHFFFAOYSA-N 0.000 claims description 7
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 6
- 239000011259 mixed solution Substances 0.000 claims description 6
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- 229910021586 Nickel(II) chloride Inorganic materials 0.000 claims description 3
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- 238000009835 boiling Methods 0.000 claims description 3
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- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 claims description 3
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- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 9
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- -1 rare earth ion Chemical class 0.000 description 6
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- VQCBHWLJZDBHOS-UHFFFAOYSA-N erbium(III) oxide Inorganic materials O=[Er]O[Er]=O VQCBHWLJZDBHOS-UHFFFAOYSA-N 0.000 description 2
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- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 1
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- SOCTUWSJJQCPFX-UHFFFAOYSA-N dichromate(2-) Chemical compound [O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O SOCTUWSJJQCPFX-UHFFFAOYSA-N 0.000 description 1
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/14—Phosphorus; Compounds thereof
- B01J27/186—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
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- 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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Abstract
The invention discloses a Z-structure-coated photocatalyst, a preparation method thereof and application thereof in photocatalysis and simultaneous conversion of Cr (VI) and degradation of rhodamine B (RhB) in an aqueous solution under the irradiation of simulated sunlight. The photocatalyst is CNT/Ni2P/Er3+:Y3Al5O12‑CNT@Bi12GeO20Prepared by a hydrothermal method and a sol-gel method. The photocatalytic reaction efficiency is obviously improved because photoproduction electrons are transferred through the CNT, the recombination of electron holes is effectively inhibited, more active sites are released by the combination of the CNT and the photocatalyst with a coating structure, Cr (VI) is reduced on the surface of the CNT, and rhodamine B (RhB) is reduced on Bi12GeO20Is degraded at the surface. Therefore, the photocatalytic system shows excellent photocatalytic performance and has wide prospect in the application of simultaneously converting Cr (VI) and degrading rhodamine B (RhB).
Description
Technical Field
The invention belongs to the field of photocatalysis, and particularly relates to a Z-type structure-coated photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The preparation method and the application thereof in photocatalysis and simultaneous conversion of Cr (VI) and degradation of rhodamine B (RhB).
Background
With the development of modern industry, environmental pollution is more and more serious. Environmental protection is listed as one of ten rough war tasks for reformation and development in China, wherein water resource protection is a major subject of environmental protection. Heavy metal ions and organic pollutants in industrial wastewater generated in various industries such as textile, paper making, leather making and the like bring great harm to the environment and human health. In the experiment, a solution containing heavy metal Cr (VI) and organic dye rhodamine B (RhB) is used as a sewage system for simulating coexistence of heavy metal ions and organic pollutants to verify the conversion and degradation effects of the photocatalyst. Heavy metals Cr (VI) and chromate (HCrO)4-/CrO4 2-) And dichromate (Cr)2O7 2-) Into the environment. Studies have shown that cr (vi) is 1000 times more carcinogenic than cr (iii) and generally has higher solubility, toxicity, instability, and biological activity. If the drinking water contains Cr (VI), the possibility of liver cancer, skin cancer and bladder cancer of human body can be increased. Rhodamine B (RhB) is a stable cationic basic dye commonly used in the printing and dyeing industry, and has stronger carcinogenicity. In the face of dyes which are difficult to be fully degraded, how to completely treat them in a harmless way is a problem which is always puzzled to scientists. Therefore, it is essential to reduce Cr (VI) to Cr (III) and to perform a complete harmless treatment of the printing and dyeing wastewater at the same time.
In recent years, semiconductor heterogeneous photocatalytic technology has attracted more attention to treat Cr (VI) and rhodamine B (RhB). If they are allowed to simultaneously perform in a system, respectively perform reduction reaction on a conduction band and oxidation reaction on a valence band, and finally generate Cr (III) on the conduction band, and rhodamine B (RhB) degrades in the valence band, the two substances can be simultaneously converted and degraded. However, one problem with this semiconductor photocatalytic technique, to do so simultaneously, is the ease with which the photogenerated electron and hole pairs recombine. Photocatalytic systems are required to have both oxidation and reduction reactions, and the catalyst must have sufficient bandwidth. However, the semiconductor catalysts are rarely used, so that the present invention introduces a coated Z-type photocatalytic system.
Among numerous photocatalysts, Bi12GeO20And Ni2P is a typical broad band semiconductor and narrow band semiconductor photocatalyst with bandwidths of 3.2eV and 1.0eV respectively. Bi12GeO20Is a relatively broad band semiconductor capable of utilizing high energy light in sunlight, Ni2P is a relatively narrow-band semiconductor, capable of utilizing low-energy light in sunlight. Compared with the nano material, the CNT is a longer tubular material (0.5-2.0 mu m) and has good conductive performance. Electrons are transferred through the CNT, the recombination of electron holes can be effectively inhibited, more active sites are released by the combination of the CNT and the photocatalyst with a coating structure, Cr (VI) is reduced on the surface of the CNT, and rhodamine B (RhB) is added in Bi12GeO20Degradation on the surface. Thereby realizing the conversion of Cr (VI) and the degradation of rhodamine B (RhB) at the same time. Therefore, the Z-type photocatalyst CNT/Ni is coated in the invention2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Has wide application prospect in the reaction of photocatalytic conversion of Cr (VI) and degradation of rhodamine B (RhB).
Disclosure of Invention
In order to provide more active sites and solve the problem of recombination of photogenerated electrons and holes, the invention designs and synthesizes a composite photocatalyst CNT/Ni which takes CNT as a conductive channel to effectively separate the photogenerated electrons and the holes2P/Er3+:Y3Al5O12-CNT@Bi12GeO20. The invention relates to a compound belonging to a coated Z-type semiconductor photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20. The method is applied to the reaction for simultaneously converting Cr (VI) in the aqueous solution and degrading rhodamine B (RhB), and has the advantages of simple operation, no pollution, easy separation, no byproduct generation and no environmental pollution.
The technical scheme adopted by the invention is as follows:
the Z-structure coated photocatalyst is CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20。
A preparation method of the photocatalyst with the Z-shaped coating structure comprises the following steps:
1) adding GeO2Dissolving in concentrated ammonia water to obtain GeO2Ammonia solution; adding BiCl3Adding into anhydrous ethanol, adding GeO after completely dissolving2Stirring for 2 hours in an ammonia solution to generate white viscous sol;
2) equal mass of Er3+:Y3Al5O12And CNT/Ni2Adding P into ultrapure water, fully dispersing for 5min by using ultrasound, heating the suspension to a boiling point, keeping the constant temperature for 2min, centrifuging, and drying at 80 ℃ for 12 h. Grinding the dried powder, then calcining for 2h at 400 ℃, and finally grinding to obtain CNT/Ni2P/Er3+:Y3Al5O12And (3) nanoparticle powder.
3) Addition of CNT/Ni to white viscous sols2P/Er3+:Y3Al5O12Stirring the nano powder at room temperature for 12h, then drying for 48h, grinding the powder, calcining for 2h in a tube furnace at 600 ℃, cooling to room temperature, and grinding to obtain the target product CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20。
The preparation method, the CNT/Ni in the step 2)2The preparation method of the P powder comprises the following steps: mixing NiCl2·6H2Adding O and red phosphorus into ultrapure water, and stirring at room temperature for 20min to obtain a mixed solution; adding CNT into the mixed solution, and stirring for 1 hr to obtain suspensionTransferring the solution into a reaction kettle at 140 deg.C for 36h, collecting, washing with distilled water and anhydrous ethanol for several times, centrifuging, drying at 60 deg.C for 12h, and grinding the dried powder to obtain CNT/Ni2And (3) P powder.
The preparation method is that Er is obtained in the step 2)3+:Y3Al5O12The preparation method of the powder comprises the following steps: adding Er2O3、Y2O3Dissolving the powder in concentrated nitric acid, magnetically heating and stirring until the solution is colorless and transparent to obtain a rare earth ion solution; then Al (NO)3)·9H2Dissolving O in distilled water, stirring with a glass rod at room temperature, slowly adding into the rare earth ion solution, dissolving citric acid as chelating agent and cosolvent with distilled water, heating and stirring at 50-60 deg.C, and stopping when the solution is viscous to obtain viscous solution; and (3) heating the viscous solution in an oven at a constant temperature of 80 ℃ for 36h until no precipitate is generated in the drying process until the solvent is evaporated to dryness, finally obtaining foamed sol, heating the obtained sol at 500 ℃ for 50min, and then respectively calcining the sol at 1100 ℃ for 2 h. Finally, the sintered mass was removed from the high temperature furnace and cooled in air to room temperature to give Er3+:Y3Al5O12And (3) powder.
The preparation method comprises the following steps of (1) according to molar ratio: rare earth ion 3: 1.
An application of the Z-type structure-coated photocatalyst in simultaneous conversion of Cr (VI) and degradation of rhodamine B (RhB) in photocatalysis.
The application comprises the following steps: mixing CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Adding the nanoscale powder into a solution to be converted and degraded, and performing illumination under the condition of xenon lamp illumination with the pH value of 2 and 500W, wherein the solution to be converted and degraded is an aqueous solution containing Cr (VI) and rhodamine B (RhB).
The use of, the CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The concentration of the nanoscale powder in the solution to be converted-degraded was 1.0 g/L.
The concentration ratio of Cr (VI) to rhodamine B (RhB) in the solution to be converted and degraded is 3: 1.
The application is characterized in that the illumination time is 40 min.
The invention has the following beneficial effects:
the Z-type photocatalyst-coated CNT/Ni prepared by the invention2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Is prepared by reacting Bi12GeO20Photo-generated electrons generated by conduction band pass through CNT as conduction channel and Ni2Photo-generated holes generated in the P-valence band combine, and Ni2Photo-generated electrons generated by P conduction band pass through Bi from CNT12GeO20Surface of Ni2Electrons generated by the P conduction band are transferred. Thereby improving the separation efficiency of the photo-generated electrons and holes. And the CNT also provides more active sites for the photocatalytic conversion of Cr (VI) and increases Bi12GeO20Exposed surfaces of holes for degradation of rhodamine B (RhB). It is known that Bi is used12GeO20Has a band width of 3.20eV, wherein the valence band is 2.55eV and the conduction band is-0.25 eV. Ni2The P bandwidth is 1.00eV, the valence band is-0.23 eV, and the conduction band is-1.23 eV. Under the excitation of simulated sunlight, electrons transit from a Valence Band (VB) to a Conduction Band (CB) to form electron-hole pairs with high energy, and the carriers are easily recombined and annihilated to release light or heat, and the CNT/Ni is caused by photogenerated electrons and holes which are not annihilated2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Showing excellent photocatalytic performance. Thus, in this method CNT acts as a conductive channel for Bi12GeO20Conduction band generated electrons and Ni2Hole bonding of P valence band to Ni2The electron transfer generated by the P conduction band effectively reduces the recombination of the photo-generated electrons and the holes. In the reaction of photocatalysis to simultaneously convert Cr (VI) and degrade rhodamine B (RhB), under the excitation of simulated sunlight, electrons generated by the photocatalyst are transferred through the CNT and are stored on the surface of the CNT again, so that the Cr (VI) is reduced to Cr (III) on the surface of the CNT. At the same time, in Bi12GeO20Surface of (2) notThe generation of voids is avoided. The resulting holes directly decompose the rhodamine b (rhb) dye. The method effectively avoids the recombination of photo-generated electrons and holes by utilizing a conductive channel, and the conductive channel is Bi12GeO20The surface releases more active sites and thus the conversion and degradation efficiency of the catalyst is improved greatly.
CNT/Ni prepared by the invention2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The nano photocatalyst has high performance. The performance of the material is high temperature resistant and acid and alkali corrosion resistant. And Ni2P/Er3+:Y3Al5O12@Bi12GeO20And Ni2P@Bi12GeO20Compared with the prior art, the catalyst has greatly improved efficiency in the degradation reaction of simultaneously converting Cr (VI) and rhodamine B (RhB) under the irradiation of simulated sunlight. The composite photocatalyst CNT/Ni of the invention2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Not only has the advantages of the traditional photocatalyst, but also has the most attention to Bi12GeO20And Ni2P-bandwidth characteristics and the positional uniqueness of conduction and valence bands, CNTs were designed as photocatalysts for conducting channels. The method solves the problem of the recombination of photo-generated electrons and holes, provides more active sites for the photocatalytic reaction, and greatly improves the efficiency of photocatalytic conversion of Cr (VI) and degradation of rhodamine B (RhB).
Drawings
FIG. 1a is Er3+:YAlO3X-ray powder diffraction (XRD) pattern of (A), FIG. 1b is Bi12GeO20X-ray powder diffraction (XRD) pattern of (A), FIG. 1c is Ni2X-ray powder diffraction (XRD) pattern of P, FIG. 1d is Ni2P@Bi12GeO20X-ray powder diffraction (XRD) pattern of (A), FIG. 1e is Ni2P/Er3+:Y3Al5O12@Bi12GeO20X-ray powder diffraction (XRD) pattern of (1 f) CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20X-ray powder diffraction (XRD) pattern of d.
FIG. 2a is Er3+:YAlO3FIG. 2b is a Scanning Electron Microscope (SEM) picture of (A), and Bi is12GeO20FIG. 2c is a Scanning Electron Microscope (SEM) picture of (A), Ni2Scanning Electron Microscope (SEM) picture of P, FIG. 2d is Ni2P@Bi12GeO20FIG. 2e is a Scanning Electron Microscope (SEM) picture of (A), Ni2P/Er3+:Y3Al5O12@Bi12GeO20FIG. 2f is a Scanning Electron Microscope (SEM) image of CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Scanning Electron Microscope (SEM) images of (a).
FIG. 3 is CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Transmission Electron Microscope (TEM) images of (a).
FIG. 4 is Ni2P@Bi12GeO20And CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Photoluminescence spectrum (PL) diagram of (a).
FIG. 5 is a graph showing the effect of photocatalyst on converting Cr (VI) and degrading rhodamine B (RhB) simultaneously in different illumination times.
FIG. 6 shows different contents of photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20And (3) simultaneously converting Cr (VI) and degrading rhodamine B (RhB) under the irradiation of simulated sunlight.
FIG. 7 shows photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20And (3) an effect diagram for simultaneously converting Cr (VI) with different concentrations and degrading 5.0mg/L rhodamine B (RhB) under the irradiation of simulated sunlight.
FIG. 8 shows a photocatalyst CNT/Ni coated with a Z-shaped structure2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Meanwhile, the mechanism diagram of converting Cr (VI) in the aqueous solution and degrading rhodamine B (RhB) is shown.
Detailed Description
Example 1 photocatalyst CNT/Ni coated with Z-type structure2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Preparation method and detection of
The preparation method comprises the following steps:
1)Bi12GeO20preparation of the powder
0.031g GeO2Dissolving in 50mL of concentrated ammonia water to obtain GeO2An aqueous ammonia solution. 1.140g of BiCl3Adding into anhydrous ethanol, adding GeO after completely dissolving2Stirring the mixture in an ammonia solution for 2 hours to generate white viscous sol. Drying at 80 ℃ for 12h to obtain Bi12GeO20And (3) powder. Grinding the powder, calcining for 2h in a tube furnace at 600 ℃, cooling to room temperature, and grinding to obtain Bi12GeO20And (3) powder.
2)Er3+:Y3Al5O12Preparation of the powder
2.7281g Er2O3(99.99％)、0.0464g Y2O3(99.99%) the powder was dissolved in concentrated nitric acid (65.00%) and stirred magnetically until colorless and transparent to obtain a rare earth ion solution. 12.6208g of Al (NO) were then weighed out3)3·9H2O (99.99%) was dissolved in distilled water, stirred with a glass rod at room temperature and slowly added to the rare earth ion solution. Using citric acid as a chelating agent and a cosolvent, wherein the molar ratio of the citric acid: weighing rare earth ions (3: 1), dissolving in distilled water, heating at 50-60 deg.C, stirring, and stopping when the solution is viscous. No precipitate was formed during this process, and a foamed viscose solution was finally obtained. And (4) putting the viscous solution into an oven, keeping the temperature constant at 80 ℃, and heating for 36 h. No precipitate is formed during the drying process until the solvent is evaporated to dryness, and finally a foamed sol is obtained. The sol obtained was heated at 500 ℃ for 50min and then calcined at 1100 ℃ for 2h, respectively. Finally, the sintered mass was removed from the high temperature furnace and cooled in air to room temperature to give Er3+:Y3Al5O12And (3) powder.
3)CNT/Ni2Preparation of P powderPrepare for
3.80g of NiCl2·6H2O and 2.80g of red phosphorus are mixed and added into 30mL of deionized water, and the mixture is stirred for 20min at room temperature to obtain a mixed solution. Weighing 0.10g of CNT, transferring into the mixed solution, and continuously stirring for 1 h; then transferring the mixture into a 30mL reaction kettle, sealing the reaction kettle, keeping the reaction kettle in an air drying furnace at 140 ℃ for 36h, collecting the mixture, washing the mixture for 3 times by using distilled water and absolute ethyl alcohol, drying the mixture for 12h at 60 ℃ after centrifugation, grinding the dried powder to finally obtain CNT/Ni2P nanoparticle powder.
4)CNT/Ni2P/Er3+:Y3Al5O12Preparation of the powder
1.00g of Er3+:Y3Al5O12And 1.00g CNT/Ni2Adding P into 20mL of ultrapure water, fully dispersing for 5min by using ultrasonic, heating the suspension to the boiling point, keeping the constant temperature for 2min, centrifuging, and drying at 80 ℃ for 12 h. The dried powder was milled and then calcined at 400 ℃ for 2 h. Finally grinding to obtain CNT/Ni2P/Er3+:Y3Al5O12And (3) nanoparticle powder.
5)CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Preparation of the powder
0.031g GeO2Dissolved in 50mL of concentrated ammonia. 1.140g of BiCl3The mixture was added to 50mL of absolute ethanol, and the mixture was added to the above solution after completely dissolving. Stirring for 2h at normal temperature until a white viscous sol is formed. 2.030g CNT/Ni addition2P/Er3+:Y3Al5O12The nano powder is stirred for 12 hours at room temperature. And then dried for 48 h. Grinding the powder, calcining in a tube furnace at 600 deg.C for 2h, cooling to room temperature, and grinding to obtain CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20And (3) powder.
(II) detection
(1) Is Er3+:YAlO3、Bi12GeO20、Ni2P、Ni2P@Bi12GeO20、Ni2P/Er3+:Y3Al5O12@Bi12GeO20、CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20X-ray powder diffraction (XRD) picture analysis of (a).
As shown in fig. 1, the structure and composition of the prepared sample was verified by XRD. The results are shown in FIG. 1. Some sharp absorption peaks are shown in fig. 1a at 18.10 ° (211), 27.76 ° (321), 29.78 ° (400), 33.38 ° (420), 35.07 ° (332), 36.68 ° (422), 41.14 ° (521), 46.53 ° (532), 52.74 ° (444), 55.06 ° (640), 57.32 ° (642) and 61.83 ° (800), which is related to Y θ (2 θ), which is related to Y (321), for example3Al5O12The standard card JCPDS card33-0040 completely agrees. It proves Er3+:Y3Al5O12Has been successfully prepared, and Er3+Has entered Y3Al5O12Lattice of (2) is substituted for Y3+. As shown in FIG. 1b, the diffraction peaks clearly appear at 24.7 °, 33.0 °, 35.3 °, 41.7 °, 45.5 °, 49.1 °, 54.1 °, 55.8 °, 61.9 °, corresponding to Bi12GeO20The diffraction peak crystal planes of (220), (321), (400), (332), (510), (521), (600), (532) and (631) of (2), which is in contrast to Bi12GeO20Matches the standard card JCPDS card 14-0117. This can prove that Bi12GeO20Was successfully prepared. As shown in fig. 1c, the sample has distinct diffraction peaks at 2 θ of 40.8 ° (111), 44.6 ° (201), 47.3 ° (210) and 54.2 ° (300), which is in contrast to Ni2The standard card JCPDS card 03-0953 of P is in agreement, confirming that pure Ni can be successfully synthesized at present2P crystal. Can find Ni2P and Bi12GeO20The characteristic diffraction peaks appear clearly in fig. 1 d. This indicates that Ni2P@Bi12GeO20Composite materials have been prepared. As can be seen from FIG. 1e, except for Ni2P and Bi12GeO20Outside the characteristic diffraction peak of Er3+:Y3Al5O12Also appears clearly in FIG. 1e, indicating that Ni has been successfully prepared2P/Er3+:Y3Al5O12@Bi12GeO20. Whereas the diffraction peak for the CNT in fig. 1f is not evident, probably due to its lower content. We can further demonstrate its presence by SEM and TEM.
(2) Is Er3+:YAlO3、Bi12GeO20、Ni2P、Ni2P@Bi12GeO20、Ni2P/Er3+:Y3Al5O12@Bi12GeO20、CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20SEM image analysis of (1).
FIG. 2 shows the Er produced3+:Y3Al5O12，Bi12GeO20，Ni2P、Ni2P@Bi12GeO20，Ni2P/Er3+:Y3Al5O12@Bi12GeO20，CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20SEM spectra of the powder were used to study its surface morphology. From FIG. 2a, many grape-shaped particles with a particle size of 40-60 nm, which are nano-sized up-conversion luminescent materials Er, can be observed3+:Y3Al5O12. FIG. 2b presents a large number of irregular lamellar crystalline particles of about 800nm to 1 μm, identified as Bi12GeO20And (3) granules. In FIG. 2c it is shown that spherical particles of around 50nm are present, these nanoparticles being considered as Ni2And P. In FIGS. 2d and e, there are numerous irregular particles with a size of about 400nm to 600 nm. The surface is smooth, the appearance is different from that of figure 2b, and the particle size is reduced. It is believed that Bi is present during the coating process12GeO20The particles are crushed and dispersed. Furthermore we found that the presence of CNTs was observed in figure 2f, which can prove that we successfully introduced CNT as a nanomaterial during the experimental procedure. The length of which is about 800nm to 1.0 μm. These findings again demonstrate the predicted CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Has already been synthesized.
(3) Is CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Transmission Electron Microscope (TEM) picture analysis of (a).
FIG. 3 shows coated Z-type photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20TEM images at different magnification ratios, where the corresponding unit scale lengths are 100nm, 20nm, 10nm and 5nm, respectively. As shown in fig. 3(100nm), some irregular spherical particles in which nanoparticles of different sizes are distributed, the presence of CNTs can be observed on the surface and inside of the particles. We believe that CNTs cross Bi12GeO20Cladding Ni2P and Er3+:Y3Al5O12The formed coated structured nanoparticles. Some of the small-sized spherical particles in FIG. 3(100nm) should be Ni2P, around which the presence of CNT was observed, could prove Ni2P successfully bound to CNTs. We can also observe that some slightly larger spherical black particles should be Er3+:Y3Al5O12Which is dispersed in Ni2P and CNT, and thus Ni can be confirmed2P-CNT and Er3+:Y3Al5O12And (4) successfully combining. On a scale of 20nm and 10nm, as shown in FIGS. 3(20nm) and (10nm), it was found that the presence of CNT and the coating structure are more clearly seen, from which Ni is more clearly observed2P and Er3+:Y3Al5O12Has been coated with Bi12GeO20And the inside. The coating structure has CNTs on the surface and inside thereof. When the unit scale is further enlarged to 5nm, many clear lattice fringes are shown in fig. 3(5 nm). By calculating the lattice fringe spacing and comparing with XRD data, the crystal plane of the prepared photocatalyst can be determined. They are clearly marked in FIG. 3(5nm), Er3+:Y3Al5O12(d＝0.293nm(221))，Ni2P(d＝0.238nm(111))，Bi12GeO20(d is 0.276nm (321)). Thus, TEM results show that Bi12GeO20Form a layer of Ni2P and Er3+:Y3Al5O12A core-shell coated structure in the center. The coating structure has CNTs on both the surface and the interior thereof.
(4) Is Ni2P@Bi12GeO20And CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Photo luminescence spectroscopy (PL) picture analysis.
Photoluminescence (PL) spectroscopy is an important method for confirming the recombination of photogenerated electron-hole pairs in semiconductors. Generally, a lower intensity signal in the PL spectrum indicates that the photo-generated electron-hole pairs are susceptible to recombination. Conversely, higher intensity indicates a relatively higher rate of electron-hole pair recombination. As is clear from FIG. 4, CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Is significantly lower than Ni2P@Bi12GeO20Description of CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Has a lower electron-hole pair recombination rate. This phenomenon may occur due to the following reasons: CNT-Ni2P，Er3+:Y3Al5O12And Bi12GeO20Formation of the coated Z-type photocatalytic system is advantageous for Bi12GeO20Photo-generated electrons (e) on Conduction Band (CB)–) And Ni2Hole (h) in the P Valence Band (VB)+) Is compounded with Ni2The photo-generated electrons generated by the P conduction band are transported and transferred through the CNT. In summary, the experimental results show that the CNT has Bi12GeO20Can not only act as an active site to accept electrons, but also inhibit the recombination rate of electron-hole pairs. In addition, due to the presence of CNTs as electron-conducting media, the transfer rate of electrons can be further increased. Therefore, novel coated Z-structured catalyst CNT/Ni is designed2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Has excellent photocatalytic performance.
Example 2 photocatalyst CNT/Ni coated with Z-type structure2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Application of different light irradiation time and different photocatalysts in photocatalytic simultaneous conversion of Cr (VI) and degradation of rhodamine B (RhB)
The experimental conditions are as follows:
50mL of an aqueous solution containing 10.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) was used as group A.
50mg photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The powder was added to 50mL of an aqueous solution containing 10.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) as group B.
50mg photocatalyst Ni2P/Er3+:Y3Al5O12@Bi12GeO20The powder was added to 50mL of an aqueous solution containing 10.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) as group C.
50mg photocatalyst Ni2P@Bi12GeO20The powder was added to 50mL of an aqueous solution containing 10.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) as group D.
Under the conditions of pH of 2 and 500W xenon lamp irradiation, the irradiation time is-20 min, 0min, 20min and 40min respectively. The experimental result is shown in FIG. 5, when the illumination time is 40min, the photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20At a concentration of 1.0g/L, the conversion rate for Cr (VI) reaches 92.0%, and the degradation rate for rhodamine B (RhB) reaches 48.0%. The reason is that CNT is used as conductive channel to make Bi12GeO20Conduction band generated photo-generated electrons and Ni2Photoproduction of hole-binding, Ni, generated in the P-valence band2The photon-generated electrons generated by the P conduction band are transferred. The recombination of photogenerated electrons and holes is effectively reduced, and the separation efficiency of the electrons and the holes is remarkably improved. Thus in contrast to the absence of a conductive pathPhotocatalyst Ni2P/Er3+:Y3Al5O12@Bi12GeO20And Ni2P@Bi12GeO20Compared with the prior art, the conversion rate of Cr (VI) and the degradation rate of rhodamine B (RhB) are obviously improved to 35.0 percent, 57.0 percent, 42.0 percent and 46.0 percent. Thus demonstrating photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Has high photocatalytic activity.
The photocatalyst is influenced by the change of the photocatalyst along with time in different illumination time, and the optimal illumination time is 40min for simultaneously converting Cr (VI) and degrading rhodamine B (RhB).
(II) different content of photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Photocatalytic effect on simultaneous conversion and degradation of Cr (VI) to rhodamine B (RhB)
70mg photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The powder was added to 50mL of an aqueous solution containing 10.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) as group A.
50mg photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The powder was added to 50mL of an aqueous solution containing 10.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) as group B.
30mg photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The powder was added to 50mL of an aqueous solution containing 20.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) as group C.
Under the conditions of pH of 2 and 500W xenon lamp irradiation, the irradiation time is-20 min, 0min, 20min, 40min, 60min and 80min respectively. The results of the experiment are shown in FIG. 6. When the concentration of the photocatalyst is 1.4g/L and 1.0g/L, the conversion efficiency and the removal efficiency are similar, and the photocatalyst has higher effects of converting Cr (VI) and degrading rhodamine B (RhB). And when the concentration of the photocatalyst is 0.6g/L, the conversion and removal rate is reduced. When in lightInterval is 80min, photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20At the concentration of 1.0g/L, the conversion rate of the rhodamine B (RhB) reaches 98 percent, and the degradation rate of the rhodamine B (RhB) reaches 59.0 percent. Therefore, 1.0g/L is the optimum concentration for the photocatalyst. When the photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The conversion and degradation efficiency drops to 15.0% and 10.0% at a concentration of 0.6g/L, probably because this concentration of photocatalyst does not provide enough photo-generated electrons and holes for the photocatalytic reaction. The high efficiency of the photocatalytic reaction is affected.
(III) photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Simultaneously has photocatalysis influence on the conversion of Cr (VI) with different concentrations and the degradation of 5ppm rhodamine B (RhB)
The experimental conditions are as follows:
50mg photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The powder was added to 50mL of an aqueous solution containing 10.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) as group A.
50mg photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The powder was added to 50mL of an aqueous solution containing 15.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) as group B.
50mg photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The powder was added to 50mL of an aqueous solution containing 20.0mg/L Cr (VI) and 5.0mg/L rhodamine B (RhB) as group C.
Under the conditions of pH of 2 and 500W xenon lamp irradiation, the irradiation time is-20 min, 0min, 20min, 40min, 60min and 80min respectively. The experimental results are shown in FIG. 7, where the light irradiation time is 80min and the photocatalyst CNT/Ni is2P/Er3+:Y3Al5O12-CNT@Bi12GeO20The concentration is 1.0g/L, the concentration of Cr (VI) in the solution is 10.0mg/L and 15.0mg/L, the conversion and degradation efficiency is similar when the concentration of rhodamine B is 5.0mg/L, the conversion and degradation efficiency is 98.0 percent, 96.0 percent, 58.0 percent and 52.0 percent, and the conversion and degradation effects are higher. When the concentration of Cr (VI) in the solution is 20.0mg/L and the concentration of rhodamine B is 5.0mg/L, the conversion and degradation rates are obviously reduced to 40.0 percent and 20.0 percent. Therefore, when the Cr (VI) concentration is 15.0mg/L, and the rhodamine B concentration is 5.0mg/L, the concentration is the optimal concentration for the conversion and degradation of the photocatalyst. Whereas the conversion and degradation efficiency at Cr (VI) concentration of 20.0mg/L is significantly reduced, probably due to excessive HCrO4-Adsorption on the catalyst surface affects the response of the photocatalyst to light.
Example 3 photocatalyst CNT/Ni coated with Z-type structure2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Mechanism for simultaneously converting Cr (VI) and degrading rhodamine B (RhB) by photocatalysis
As can be seen from FIG. 8, Bi12GeO20Has a band width of 3.20eV, wherein the valence band is +2.55eV and the conduction band is-0.25 eV. Ni2The P bandwidth is 1.00eV, the valence band is-0.23 eV, and the conduction band is-1.23 eV. From Bi12GeO20Potential of conduction band and Ni2P has similar valence band potential, so that an ideal Z-type photocatalytic system can be formed, and photo-generated electron and hole pairs can be efficiently transferred. But Ni because of its clad structure2P is Bi12GeO20Coated with Ni2Photo-generated electrons generated by P conduction band cannot be transferred in order to transfer Ni2Photo-generated electron transfer from the P conduction band, we add CNT to Bi12GeO20And Ni2P forms a putative redox recombination center. So that the photo-generated electrons are transferred. Thereby forming the special coated Z-shaped photocatalyst CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20. In the reaction of photocatalysis for simultaneously converting Cr (VI) and degrading rhodamine B (RhB), Ni2Photo-generated electrons generated by the P conduction band pass through Bi through CNT12GeO20To make a turnAnd (6) moving. CNTs exist both inside and outside the encapsulated structured catalyst. The CNTs present inside the coating structure can act as conductive channels, while the CNTs present outside the coating structure can act as active sites for the photocatalytic conversion of cr (vi). Due to the longer tubular structure of CNTs, the active sites for conversion of cr (vi) can be significantly increased. At the same time increase Bi12GeO20Is Bi on the exposed surface of the active site of12GeO20Degrading rhodamine B (RhB) provides more photogenerated holes. And the photo-generated holes are in Bi12GeO20Can directly decompose the organic pollutants until completely decomposed.
Claims (7)
1. A photocatalyst coated with a Z-shaped structure, characterized in that: the photocatalyst with the Z-shaped structure is CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20；
The preparation method of the photocatalyst with the Z-type structure comprises the following steps:
1) adding GeO2Dissolving in concentrated ammonia water to obtain GeO2Ammonia solution; adding BiCl3Adding into anhydrous ethanol, adding GeO after completely dissolving2Stirring for 2 hours in an ammonia solution to generate white viscous sol;
2) equal mass of Er3+:Y3Al5O12And CNT/Ni2Adding P into ultrapure water, fully dispersing for 5min by using ultrasound, heating the suspension to a boiling point, keeping the constant temperature for 2min, centrifuging, and drying at 80 ℃ for 12 h; grinding the dried powder, then calcining for 2h at 400 ℃, and finally grinding to obtain CNT/Ni2P/Er3+:Y3Al5O12A nanoparticle powder;
3) addition of CNT/Ni to white viscous sols2P/Er3+:Y3Al5O12Stirring the nano powder at room temperature for 12h, then drying for 48h, grinding the powder, calcining for 2h in a tube furnace at 600 ℃, cooling to room temperature, and grinding to obtain the target product CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20。
2. The photocatalyst having a Z-type cladding structure according to claim 1, wherein CNT/Ni in the step 2)2The preparation method of the P powder comprises the following steps: mixing NiCl2• 6H2Adding O and red phosphorus into ultrapure water, and stirring at room temperature for 20min to obtain a mixed solution; adding CNT into the mixed solution, stirring for 1h, transferring the obtained suspension solution to a reaction kettle at 140 deg.C for 36h, collecting and washing with distilled water and anhydrous ethanol for several times, centrifuging, drying at 60 deg.C for 12h, and grinding the dried powder to obtain CNT/Ni2And (3) P powder.
3. The use of the Z-structure coated photocatalyst of claim 1 for the photocatalytic simultaneous conversion of cr (vi) and degradation of rhodamine b (rhb).
4. The application of claim 3, wherein the application process is as follows: mixing CNT/Ni2P/Er3+:Y3Al5O12-CNT@Bi12GeO20Adding the nanoscale powder into a solution to be converted and degraded, and performing illumination under the condition of xenon lamp illumination with the pH value of 2 and 500W, wherein the solution to be converted and degraded is an aqueous solution containing Cr (VI) and rhodamine B (RhB).
5. The use of claim 4, wherein the CNT/Ni is selected from the group consisting of CNT and Ni2P/Er3+:Y3Al5O12-CNT@ Bi12GeO20The concentration of the nanoscale powder in the solution to be converted-degraded was 1.0 g/L.
6. The use according to claim 5, wherein the ratio of the mass concentrations of Cr (VI) and rhodamine B (RhB) in the solution to be converted and degraded is 3: 1.
7. Use according to claim 5, wherein the illumination time is 40 min.
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