CN116943700A - Preparation method of dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst - Google Patents
Preparation method of dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst Download PDFInfo
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 80
- JMANVNJQNLATNU-UHFFFAOYSA-N oxalonitrile Chemical compound N#CC#N JMANVNJQNLATNU-UHFFFAOYSA-N 0.000 title claims abstract description 71
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 68
- 239000010439 graphite Substances 0.000 title claims abstract description 68
- 229910003440 dysprosium oxide Inorganic materials 0.000 title claims abstract description 66
- NLQFUUYNQFMIJW-UHFFFAOYSA-N dysprosium(iii) oxide Chemical compound O=[Dy]O[Dy]=O NLQFUUYNQFMIJW-UHFFFAOYSA-N 0.000 title claims abstract description 66
- 239000003054 catalyst Substances 0.000 title claims abstract description 53
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 40
- 230000007547 defect Effects 0.000 title claims abstract description 32
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 239000011941 photocatalyst Substances 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 16
- 239000000725 suspension Substances 0.000 claims abstract description 12
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 238000001354 calcination Methods 0.000 claims abstract description 6
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 16
- 239000004202 carbamide Substances 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 230000002950 deficient Effects 0.000 claims description 11
- 238000001291 vacuum drying Methods 0.000 claims description 11
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- 239000007787 solid Substances 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 7
- 239000000126 substance Substances 0.000 claims description 7
- 238000003756 stirring Methods 0.000 claims description 5
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000007864 aqueous solution Substances 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- 239000011363 dried mixture Substances 0.000 claims description 4
- 229910052573 porcelain Inorganic materials 0.000 claims description 4
- 238000005406 washing Methods 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims 2
- 238000009210 therapy by ultrasound Methods 0.000 claims 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 abstract description 21
- 239000001257 hydrogen Substances 0.000 abstract description 21
- 229910052739 hydrogen Inorganic materials 0.000 abstract description 21
- 238000004519 manufacturing process Methods 0.000 abstract description 18
- 230000001699 photocatalysis Effects 0.000 abstract description 11
- 239000004065 semiconductor Substances 0.000 abstract description 9
- 238000005215 recombination Methods 0.000 abstract description 7
- 230000006798 recombination Effects 0.000 abstract description 7
- 230000004298 light response Effects 0.000 abstract description 3
- 238000001308 synthesis method Methods 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 6
- 238000010521 absorption reaction Methods 0.000 description 5
- 239000000969 carrier Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 5
- 238000007792 addition Methods 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- 239000002131 composite material Substances 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 230000031700 light absorption Effects 0.000 description 3
- 150000002829 nitrogen Chemical class 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- WUPHOULIZUERAE-UHFFFAOYSA-N 3-(oxolan-2-yl)propanoic acid Chemical compound OC(=O)CCC1CCCO1 WUPHOULIZUERAE-UHFFFAOYSA-N 0.000 description 2
- 229910052692 Dysprosium Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 238000007146 photocatalysis Methods 0.000 description 2
- 238000000985 reflectance spectrum Methods 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000001362 electron spin resonance spectrum Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 230000005283 ground state Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006303 photolysis reaction Methods 0.000 description 1
- 230000015843 photosynthesis, light reaction Effects 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
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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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/04—Mixing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/06—Washing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
- C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
- C01B3/042—Decomposition of water
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
- C01B2203/10—Catalysts for performing the hydrogen forming reactions
- C01B2203/1041—Composition of the catalyst
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Abstract
The invention belongs to the technical field of semiconductor photocatalysts, and particularly relates to a preparation method of a dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst. The preparation method comprises the steps of preparing modified nitrogen-defect graphite phase carbon nitride, preparing nitrogen-defect graphite phase carbon nitride suspension, mixing the nitrogen-defect graphite phase carbon nitride suspension with dysprosium oxide, and preparing the dysprosium oxide/graphite phase carbon nitride photocatalyst by a calcination method. Modified ND-g-C prepared by the invention 3 N 4 In the method, due to the existence of nitrogen defects, the catalyst has smaller forbidden bandwidth and lower carrier recombination rate, and can be used for constructing a heterojunction with dysprosium oxide to adjust the band gap of the dysprosium oxide, so that the light response range is widened, the dysprosium oxide/graphite phase carbon nitride visible light catalyst has higher photocatalytic hydrogen production efficiency compared with dysprosium oxide, and the synthesis method is simpler and easy to operate and can be synthesized in one step.
Description
Technical Field
The invention belongs to the technical field of semiconductor photocatalysts, and particularly relates to a preparation method of a dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst.
Background
Due to the acceleration of the urban and industrial processes, the problems of energy shortage and environmental pollution are increasingly serious. Hydrogen energy, a clean energy source with a high heating value, is considered to be the most ideal alternative to conventional fossil fuels. The method for producing hydrogen by decomposing water through solar energy is a promising hydrogen production party with low cost and high efficiency. 43% of sunlight is in a visible light region, so that the study on water decomposition awareness under the irradiation of visible light has a certain practical significance.
The key point of producing hydrogen by decomposing water with visible light is to construct a high-efficiency and stable photocatalyst. Various catalysts for photocatalytic hydrogen evolution have been explored so far, such as titanium dioxide (TiO 2 ) Zinc oxide (ZnO), cadmium sulfide (CdS), graphite phase carbon nitride (g-C) 3 N 4 ) And semiconductor photocatalysts. However, these single semiconductor photocatalysts generally have the problems of large forbidden bandwidth and high electron-hole pair recombination rate, so that the light absorption range is small, the effective charge separation rate is low, and the high capability of producing hydrogen by visible light catalysis is not possessed. Dysprosium oxide (Dy) 2 O 3 ) The unpaired electrons of the inner layer 4f orbit make it have electron energy level, the f shell captures the excited electrons in the irradiation process of visible light, further delay the recombination process of electron-hole pairs. Dy, however 2 O 3 The photocatalytic activity of the catalyst is not high, mainly because the forbidden bandwidth is large, only ultraviolet light accounting for about 4% of sunlight can be absorbed, and the catalyst has poor response to visible light, so that the research and development of dysprosium oxide in the aspect of photocatalytic hydrogen production are greatly limited. Based on the above drawbacks, in order to improve Dy 2 O 3 The visible light catalytic efficiency of the semiconductor device is modified by utilizing the heterojunction formed by coupling of the narrow band gap semiconductor. Graphite phase carbon nitride (g-C) 3 N 4 ) The light-emitting diode has good stability, the energy band structure is easy to regulate and control, and the light-emitting diode is cheap and easy to obtain, so that the light-emitting diode becomes one of research hotspots in the field of photocatalysis. Defect engineering can regulate g-C 3 N 4 And reduces the recombination rate of carriers, is considered as an effective strategy for improving the photocatalytic performance thereof. The introduction of nitrogen defects not only expands g-C 3 N 4 And more efficient electron excitation is generated, facilitating charge transport. Therefore, a new preparation method of a composite catalyst is sought, and the problem to be solved is urgent.
Disclosure of Invention
The invention aims to solve the technical problem of providing a preparation method of a dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst, which is prepared by doping nitrogen defect graphite phase carbon nitride (ND-g-C) 3 N 4 ) And a heterojunction is constructed by the semiconductor photocatalyst and dysprosium oxide, so that the semiconductor photocatalyst with excellent performance is prepared, the forbidden bandwidth of the semiconductor is regulated, the recombination rate of photon-generated carriers is reduced, and the hydrogen production efficiency of the photocatalyst is improved. The technical scheme adopted is as follows:
the preparation method of the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst specifically comprises the following steps:
(1) Modified nitrogen-deficient graphite phase carbon nitride (ND-g-C) 3 N 4 ) Is prepared from the following steps: dissolving urea in a certain volume of KOH aqueous solution, and drying in an oven; transferring the dried mixture to a crucible, roasting in a muffle furnace, naturally cooling to room temperature, washing with absolute ethyl alcohol and deionized water for three times, and placing in a vacuum drying oven to obtain modified ND-g-C 3 N 4 ；
(2)Preparation of ND-g-C 3 N 4 Suspension: ND-g-C obtained in step (1) 3 N 4 Placing into deionized water, and ultrasonic dispersing to obtain ND-g-C 3 N 4 A suspension;
(3) Mixing: to ND-g-C 3 N 4 Dysprosium oxide (Dy) is added to the suspension 2 O 3 ) Ultrasonic stirring to mix them uniformly, and placing them in a vacuum drying oven to obtain solid matter;
(4) Preparing dysprosium oxide/graphite phase carbon nitride photocatalyst by a calcination method: transferring the solid substance obtained in the step (3) to a porcelain boat, and roasting in a tube furnace to obtain the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst.
Preferably, in the step (1), the mass ratio of KOH to urea is (2-10): 750, and the drying temperature is 60 ℃.
Preferably, the mass ratio of KOH to urea is 6:750.
Preferably, in the step (1), the ratio of the urea to the KOH aqueous solution is 7.5/50g/ml.
Preferably, in the step (1), the roasting temperature is 550 ℃, the roasting time is 3 hours, the heating rate is 5 ℃/min, and the vacuum drying temperature is 55 ℃.
Preferably, in the step (2) and the step (3), the mass ratio of the nitrogen-defective graphite phase carbon nitride to dysprosium oxide is 1:2-19.
Preferably, in the step (4), the heating rate of the tube furnace is 5 ℃/min, the roasting temperature is 500 ℃, and the roasting time is 3h.
Preferably, in the prepared dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst, the mass percent of the nitrogen defect graphite phase carbon nitride is 20-30%, especially 25%, and the photocatalytic hydrogen production efficiency is highest.
Compared with the prior art, the invention has the beneficial effects that:
modified ND-g-C prepared by the invention 3 N 4 In the process, due to the existence of nitrogen defects, the nitrogen defects have smaller forbidden bandwidth and lower recombination rate of carriers, and can be used for constructing heterojunction with dysprosium oxide to adjust the band gap of the dysprosium oxideThe light response range is widened, so that the dysprosium oxide/graphite phase carbon nitride visible light catalyst has higher photocatalysis hydrogen production efficiency compared with dysprosium oxide, and the synthesis method is simpler and easy to operate, and can be synthesized in one step.
In the preparation method, when the mass ratio of KOH to urea is 6:750 and the mass percentage of nitrogen-defect graphite phase carbon nitride is 25%, the prepared dysprosium oxide/nitrogen-defect graphite phase carbon nitride visible-light-induced photocatalyst is applied to photolysis water, and the hydrogen production rate can reach 470 mu mol.h -1 ·g -1 Left and right.
Drawings
FIG. 1 is an XRD spectrum of a dysprosium oxide/nitrogen-deficient graphite phase carbon nitride photocatalyst with varying KOH doping levels.
FIG. 2 shows ND-g-C obtained by the present invention 3 N 4 XRD spectrum of dysprosium oxide/nitrogen defect graphite phase carbon nitride photocatalyst with variable loading.
Fig. 3 is an SEM image of dysprosium oxide/nitrogen deficient graphite phase carbon nitride photocatalyst prepared in example 9 of the present invention.
FIG. 4 is a graph of EPR spectra of graphite phase carbon nitride and nitrogen-deficient graphite phase carbon nitride prepared according to the present invention.
FIG. 5 is a graph of the ultraviolet-visible diffuse reflectance spectra of dysprosium oxide/nitrogen deficient graphite phase carbon nitride and pure dysprosium oxide with varying doping levels of KOH made in accordance with the present invention.
FIG. 6 is a diagram of ND-g-C obtained by the present invention 3 N 4 And a dysprosium oxide/nitrogen defect graphite phase carbon nitride with variable loading and a pure dysprosium oxide ultraviolet-visible diffuse reflection spectrum.
FIG. 7 is a graph showing the hydrogen production of dysprosium oxide/nitrogen-deficient graphite phase carbon nitride photocatalyst with varying KOH doping levels and pure dysprosium oxide over 4 hours.
FIG. 8 shows ND-g-C obtained by the present invention 3 N 4 Dysprosium oxide/nitrogen defect graphite phase carbon nitride photocatalyst with variable loading and a pure dysprosium oxide 4h hydrogen production amount diagram.
Detailed Description
The drawings are for illustrative purposes only; some well known structures in the drawings and descriptions thereof may be omitted to those skilled in the art, and thus, should not be construed as limiting the invention.
The source of the raw materials used in the present invention is not particularly limited and may be commercially available.
The technical scheme and effect of the present invention will be described in detail with reference to the accompanying drawings.
Example 1
The preparation method of the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst specifically comprises the following steps:
(1) Modified nitrogen-deficient graphite phase carbon nitride (ND-g-C) 3 N 4 ) Is prepared from the following steps: 7.5g of urea was dissolved in 50ml of aqueous KOH solution, with a mass of KOH of 0.02g.
Then drying in a 60 ℃ oven, transferring the dried mixture to a crucible, roasting in a muffle furnace at 550 ℃ for 3 hours and at a heating rate of 5 ℃/min, taking out after sintering, naturally cooling to room temperature, respectively washing with absolute ethyl alcohol and deionized water for three times, and drying in a 55 ℃ vacuum drying oven to obtain modified ND-g-C 3 N 4 。
(2) Preparation of ND-g-C 3 N 4 Suspension: ND-g-C obtained in step (1) 3 N 4 Placing into deionized water, and ultrasonic dispersing to obtain ND-g-C 3 N 4 And (3) suspending liquid.
(3) Mixing: to ND-g-C 3 N 4 Dysprosium oxide (Dy) is added to the suspension 2 O 3 ) And (3) uniformly mixing the materials by ultrasonic stirring, and then placing the materials in a vacuum drying oven to obtain a solid substance.
(4) Preparing dysprosium oxide/graphite phase carbon nitride photocatalyst by a calcination method: transferring the solid substance obtained in the step (3) to a porcelain boat, and roasting in a tube furnace to obtain the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst. Wherein, the mass ratio of the nitrogen defect graphite phase carbon nitride to dysprosium oxide is 1:19, namely ND-g-C in the catalyst prepared 3 N 4 Is 5% by mass, marked Dy 2 O 3 -5％CN-0.02。
Example 2
7.5g of urea was dissolved in 50ml of aqueous KOH solution, with a mass of KOH of 0.04g. In the prepared catalyst, ND-g-C 3 N 4 Is 5% by mass, marked Dy 2 O 3 -5% cn-0.04. Other points not described are the same as in example 1.
Example 3
7.5g of urea was dissolved in 50ml of aqueous KOH solution, with a mass of KOH of 0.06g. In the prepared catalyst, ND-g-C 3 N 4 Is 5% by mass, marked Dy 2 O 3 -5% cn-0.06. Other points not described are the same as in example 1.
Example 4
7.5g of urea were dissolved in 50ml of aqueous KOH solution, with a KOH mass of 0.08g. In the prepared catalyst, ND-g-C 3 N 4 Is 5% by mass, marked Dy 2 O 3 -5% cn-0.08. Other points not described are the same as in example 1.
Example 5
7.5g of urea were dissolved in 50ml of aqueous KOH solution, with a mass of KOH of 0.1g. In the prepared catalyst, ND-g-C 3 N 4 Is 5% by mass, marked Dy 2 O 3 -5% cn-0.1. Other points not described are the same as in example 1.
EXAMPLE 6
The preparation method of the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst specifically comprises the following steps:
(1) Modified nitrogen-deficient graphite phase carbon nitride (ND-g-C) 3 N 4 ) Is prepared from the following steps: 7.5g of urea was dissolved in 50ml of aqueous KOH solution, with a mass of KOH of 0.06g.
Then drying in a 60 ℃ oven, transferring the dried mixture to a crucible, roasting in a muffle furnace at 550 ℃ for 3 hours and at a heating rate of 5 ℃/min, taking out after sintering, naturally cooling to room temperature, respectively washing with absolute ethyl alcohol and deionized water for three times, and drying in a 55 ℃ vacuum drying oven to obtain modified ND-g-C 3 N 4 。
(2) Preparation of ND-g-C 3 N 4 Suspension: ND-g-C obtained in step (1) 3 N 4 Placing into deionized water, and ultrasonic dispersing to obtain ND-g-C 3 N 4 And (3) suspending liquid.
(3) Mixing: to ND-g-C 3 N 4 Dysprosium oxide (Dy) is added to the suspension 2 O 3 ) And (3) uniformly mixing the materials by ultrasonic stirring, and then placing the materials in a vacuum drying oven to obtain a solid substance.
(4) Preparing dysprosium oxide/graphite phase carbon nitride photocatalyst by a calcination method: transferring the solid substance obtained in the step (3) to a porcelain boat, and roasting in a tube furnace to obtain the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst. Wherein, the mass ratio of the nitrogen defect graphite phase carbon nitride to dysprosium oxide is 1:9, ND-g-C in the catalyst prepared 3 N 4 Is 10% by mass, marked Dy 2 O 3 -10％CN-0.06。
Example 7
The mass ratio of the nitrogen-defect graphite phase carbon nitride to dysprosium oxide is 3:17, namely ND-g-C in the prepared catalyst 3 N 4 15% by mass of Dy-marked 2 O 3 15% CN-0.06. Other points not described are the same as in example 6.
Example 8
The mass ratio of the nitrogen-defect graphite phase carbon nitride to dysprosium oxide is 1:4, namely ND-g-C in the prepared catalyst 3 N 4 Is 20% by mass, marked Dy 2 O 3 -20% cn-0.06. Other points not described are the same as in example 6.
Example 9
The mass ratio of the nitrogen-defect graphite phase carbon nitride to dysprosium oxide is 1:3, namely ND-g-C in the prepared catalyst 3 N 4 25% by mass, dy-marked 2 O 3 25% CN-0.06, as shown in FIG. 3, is an SEM image of the prepared catalyst. Other points not described are the same as in example 6.
Example 10
The mass ratio of the nitrogen-defect graphite phase carbon nitride to dysprosium oxide is 3:7, namely ND-g-C in the prepared catalyst 3 N 4 Is 30% by mass, marked Dy 2 O 3 -30% cn-0.06. Other points not described are the same as in example 6.
Comparative example 1
Using unmodified graphite-phase carbon nitride (g-C 3 N 4 ) Is prepared through ultrasonic dispersing, adding dysprosium oxide (Dy) 2 O 3 ) Stirring with ultrasonic wave to mix them uniformly, placing in vacuum drying oven, calcining to obtain dysprosium oxide/graphite phase carbon nitride photocatalyst, and g-C in the prepared catalyst 3 N 4 Is 5% by mass, marked Dy 2 O 3 -5% cn-0. Other points not described are the same as in example 1.
Dy, as shown in FIG. 1 2 O 3 Characteristic peaks appear at 2θ=20.32°,29.04 °,33.64 °,43.25 °,48.36 °,57.32 °, respectively corresponding to cubic Dy phase 2 O 3 (JCPDS card: no. 78-0388), crystal planes (211), (222), (400), (134), (400), (622). Dy (Dy) 2 O 3 Characteristic peak of 5% CN-x sample and Dy 2 O 3 Is substantially the same and is difficult to find ND-g-C 3 N 4 Is described as ND-g-C 3 N 4 Is contained in a small amount and does not change its crystal structure during the preparation.
As shown in FIG. 2, with respect to the prepared catalyst, dy in the prepared catalyst was observed to increase with the increase in the content of CN-0.06 2 O 3 Is the position of the characteristic peak of (a) and pure Dy 2 O 3 Is the same, indicating that the addition of CN-0.06 did not change Dy 2 O 3 Is a crystal form of (a). Dy in the prepared catalyst when the addition amount of CN-0.06 was 25% and 30% 2 O 3 The peak intensity of (C) gradually decreases, possibly due to an increase in the content of CN-0.06, which is in Dy 2 O 3 The coating amount of the surface is increased to lead Dy 2 O 3 The crystallinity of (2) decreases. At the same time, in the prepared catalyst Dy 2 O 3 -20％CN-0.06、Dy 2 O 3 -25％CN-0.06、Dy 2 O 3 In 30% CN-0.06, a corresponding CN-0.0 was observed at 27.53 °6 due to the higher dispersibility and lower crystallinity of CN-0.06. Peak-to-average of the remaining diffraction and Dy 2 O 3 (JCPDS card: NO. 78-0388) is consistent, and the composite material is proved to be made of Dy 2 O 3 And CN-0.06.
As shown in FIG. 3, from the prepared catalyst scanning electron microscope, ND-g-C 3 N 4 Uniformly dispersed in Dy 2 O 3 Between but not destroy Dy 2 O 3 The original rod-shaped structure of the Dy-synthesizing material shows that the Dy is successfully synthesized 2 O 3 /ND-g-C 3 N 4 The catalyst prepared.
ND-g-C as shown in FIG. 4 3 N 4 And g-C 3 N 4 Shan Luolun-z wire with g value of 2.004 is shown. Wherein ND-g-C 3 N 4 A strong symmetrical resonance signal is obtained, and the existence of unpaired electrons and nitrogen vacancies on the carbon atoms of the aromatic ring is verified. Indicating that KOH was added to g-C during the high temperature polymerization of urea 3 N 4 The matrix forms nitrogen defects, thereby enhancing light absorption.
As shown in FIG. 5, dy 2 O 3 As can be seen in the UV diffuse reflectance spectrum of 5% CN-x (x represents 0.02, 0.04, 0.06, 0.08, 0.1), in ND-g-C 3 N 4 When the doping amount of Dy is only 5%, dy is compared with the rest of the sample 2 O 3 Absorption peak of 5% CN-0.06 with Dy 2 O 3 The forbidden bandwidth is also reduced from 4.85eV to 4.75eV compared to the occurrence of a significant red shift. This indicates that doping with CN-0.06, dy 2 O 3 The light absorption range of (2) is affected more. Therefore, CN-0.06 and Dy are selected 2 O 3 Dy preparation 2 O 3 /ND-g-C 3 N 4 A composite catalyst. Wherein, in the present specification and drawings, CN represents ND-g-C 3 N 4 。
As shown in FIG. 6, dy 2 O 3 In the ultraviolet diffuse reflection spectrum of (2), it can be seen that Dy 2 O 3 Besides the absorption peak at 230nm, there are absorption peaks at 349nm, 803 nm,385nm,424nm,450nm,473nm,respectively correspond to 6H 15/2 Ground state to 6P 7/2 ，6P 5/2 ，4F 7/2 +4I 13/2 ，4G 11/2 ，4I 15/2 ，4F 9/2 Transition of upper energy level. The ultraviolet diffuse reflection spectrum of the prepared catalyst can show that with the increase of the addition amount of CN-0.06, the absorption peak of the prepared catalyst is red shifted, and when the doping amount is 20%,25% and 30%, the absorption peak of the prepared catalyst is obviously shifted to the visible light region. As can be seen from fig. 4, the forbidden bandwidth of the prepared catalyst gradually decreases with the increase of CN-0.06. Wherein the prepared catalyst Dy 2 O 3 25% CN-0.06 has the smallest forbidden band width (2.62 eV), and is compared with pure Dy 2 O 3 (4.85 eV) is reduced by 2.23eV. Experimental results show that CN-0.06 can effectively reduce Dy 2 O 3 The forbidden bandwidth of (2) widens the photoresponse range, thereby generating more photon-generated carriers and being beneficial to improving the photocatalytic hydrogen production efficiency.
As shown in FIG. 7, with pure Dy 2 O 3 In contrast, the catalyst Dy prepared 2 O 3 The hydrogen production rate of 5% CN-x is increased. Wherein the catalyst prepared is ND-g-C 3 N 4 Is 5% by mass, marked Dy 2 O 3 The maximum hydrogen production rate of the sample of 5% CN-0.06 is shown in the preparation of ND-g-C 3 N 4 There is an optimum amount of KOH doping.
As shown in FIG. 8, with pure Dy 2 O 3 In contrast, the catalyst Dy prepared 2 O 3 /ND-g-C 3 N 4 The hydrogen production rate of (2) is significantly increased. Wherein, the mass ratio of the nitrogen defect graphite phase carbon nitride to dysprosium oxide is 1:3, namely ND-g-C in the prepared catalyst 3 N 4 Is 25% by mass and is marked as Dy 2 O 3 The hydrogen production rate was maximum for the 25% cn-0.06 sample. This indicates that ND-g-C was added 3 N 4 After that, dy is widened 2 O 3 The light response range of the prepared catalyst is increased for absorbing visible light. And, load ND-g-C 3 N 4 Can be combined with Dy 2 O 3 Forming heterojunction and effectivelyThe recombination rate of photo-generated carriers is reduced, and the speed of the photocatalytic hydrogen production reaction is improved. But when ND-g-C 3 N 4 At 30% loading, the hydrogen production efficiency of the prepared catalyst is significantly reduced, which can be attributed to excessive ND-g-C 3 N 4 Cover and distribute in Dy 2 O 3 Active reactive sites on the surface and can shield part of the incidence of visible light, thereby reducing the photocatalytic activity of the system, thus ND-g-C 3 N 4 There is an optimal load ratio.
It should be understood that the above description is not intended to limit the invention to the particular embodiments disclosed, but to limit the invention to the particular embodiments disclosed, and that the invention is not limited to the particular embodiments disclosed, but is intended to cover modifications, adaptations, additions and alternatives falling within the spirit and scope of the invention.
Claims (8)
1. The preparation method of the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst is characterized by comprising the following steps of:
(1) Preparation of modified nitrogen-defective graphite phase carbon nitride: dissolving urea in a certain volume of KOH aqueous solution, and drying in an oven; transferring the dried mixture to a crucible, roasting in a muffle furnace, naturally cooling to room temperature, respectively washing with absolute ethyl alcohol and deionized water for three times, and placing in a vacuum drying oven to obtain modified nitrogen-defective graphite phase carbon nitride;
(2) Preparing a nitrogen-defect graphite phase carbon nitride suspension: placing the nitrogen-defective graphite phase carbon nitride obtained in the step (1) into deionized water, and carrying out ultrasonic treatment to uniformly disperse the nitrogen-defective graphite phase carbon nitride to obtain nitrogen-defective graphite phase carbon nitride suspension;
(3) Mixing: adding dysprosium oxide into the nitrogen-defective graphite phase carbon nitride suspension, stirring by ultrasonic to uniformly mix the dysprosium oxide and placing the mixture in a vacuum drying oven to obtain a solid substance;
(4) Preparing dysprosium oxide/graphite phase carbon nitride photocatalyst by a calcination method: transferring the solid substance obtained in the step (3) to a porcelain boat, and roasting in a tube furnace to obtain the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible light catalyst.
2. The method for preparing the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible-light-induced photocatalyst according to claim 1, wherein in the step (1), the mass ratio of KOH to urea is (2-10): 750, the drying temperature was 60 ℃.
3. The method for preparing the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible-light-induced photocatalyst according to claim 2, wherein the mass ratio of KOH to urea is 6:750.
4. the method of producing a dysprosium oxide/nitrogen deficient graphite phase carbon nitride visible light catalyst according to claim 1, wherein in said step (1), the ratio of urea to KOH aqueous solution volume is 7.5/50g/ml.
5. The method for preparing the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible-light-induced photocatalyst according to claim 1, wherein in the step (1), the roasting temperature is 550 ℃, the roasting time is 3 hours, the heating rate is 5 ℃/min, and the vacuum drying temperature is 55 ℃.
6. The method for preparing a dysprosium oxide/nitrogen-deficient graphite phase carbon nitride visible light catalyst according to claim 1, wherein in the step (2) and the step (3), the mass ratio of the nitrogen-deficient graphite phase carbon nitride to dysprosium oxide is 1:2-19.
7. The method for preparing the dysprosium oxide/nitrogen defect graphite phase carbon nitride visible-light-induced photocatalyst according to claim 1, wherein in the step (4), the heating rate of the tube furnace is 5 ℃/min, the roasting temperature is 500 ℃, and the roasting time is 3 hours.
8. The method for preparing the dysprosium oxide/nitrogen-defective graphite phase carbon nitride visible-light-induced photocatalyst according to claim 1, wherein the mass percentage of the nitrogen-defective graphite phase carbon nitride in the prepared dysprosium oxide/nitrogen-defective graphite phase carbon nitride visible-light-induced photocatalyst is 20-30%.
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