CN116212909A - Vanadium-substituted phosphomolybdic acid/g-C 3 N 4 Nanosheet Z-type heterojunction as well as preparation method and application thereof - Google Patents
Vanadium-substituted phosphomolybdic acid/g-C 3 N 4 Nanosheet Z-type heterojunction as well as preparation method and application thereof Download PDFInfo
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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
- 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
- B01J27/195—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with vanadium, niobium or tantalum
- B01J27/198—Vanadium
- B01J27/199—Vanadium with chromium, molybdenum, tungsten or polonium
-
- 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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/24—Nitrogen compounds
-
- B01J35/39—
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
Abstract
The invention discloses a vanadium-substituted phosphomolybdic acid/g-C 3 N 4 A nano-sheet Z-type heterojunction, a preparation method and application thereof relate to the technical field of synthesis of nano-photocatalytic materials. The method comprises the following steps: naVO is processed 3 And Na (Na) 2 HPO 4 Dissolving in boiling water, adding concentrated sulfuric acid dropwise, adding Na 2 MoO 4 Extracting with concentrated sulfuric acid and diethyl ether to obtain VPOM powder; roasting urea to obtain block-shaped g-C 3 N 4 Grinding the solid, and then roasting the ground solid for the second time to obtain g-C 3 N 4 A nanosheet; dispersing into HCl solution, ultrasonic treating, adding VPOM powder, stirring, filtering, washing and freeze drying to obtain vanadium substituted phosphomolybdic acid/g-C 3 N 4 Nanoplate Z-type heterojunction. The VPOM/CNNS heterojunction provided by the invention can be used as a photocatalyst to catalyze and activate plastic polymers at normal temperature and normal pressure, and can be converted into formic acid, so that a new idea is provided for sustainable reuse of future plastics.
Description
Technical Field
The invention relates to the technical field of synthesis of nano photocatalytic materials, in particular to a vanadium-substituted phosphomolybdic acid/g-C 3 N 4 A Z-type heterojunction of nano-sheet and its preparing process and application are disclosed.
Background
Plastic has become an integral part of modern life as an artificially synthesized polymer, however, the ubiquitous nature of plastic articles is considered to be a double-edged sword. It is estimated that about 50 million tons of plastic become plastic waste between 1950 and 2015, accumulate in the earth's ecosystem, most of them are difficult to degrade, and because of their corrosion resistance, they can exist in nature for decades, and plastic is widely distributed in fresh water, sea and groundwater environments, which not only causes serious environmental pollution, but also is a great waste of resources. Thus, sustainable plastic recycling technologies are essential to the development of recycling economies.
Polyolefins have been the largest share of the plastics market and have been more than half of the global plastics waste, however, recovery of polyolefins by C-C bond cleavage processes is still challenging due to their low solubility and strong inertness; compared with pyrolysis treatment mode with high energy consumption, the photocatalysis technology provides a sustainable and economic plastic recycling mode, and generally, the photodegradation process of plastic generally requires that photo-generated holes have very positive oxidation potential>1.9V vs NHE) for cleaving long polymer chains, while the corresponding electrons will react with oxygen to generate superoxide radicals (O 2 /O 2 ·- = -0.33V vs NHE), O generated by reaction 2 ·- The hydroperoxide groups can be further formed by extracting hydrogen atoms from the polymer chain, which can break the polymer chain. In view of the above limitations, current research generally employs ultraviolet light absorbing wide bandgap semiconductors, including TiO 2 ZnO and Nb 2 O 5 This generally results in a lower solar collection efficiency; in addition, a great deal of carbon dioxide emission is generated in the photocatalytic degradation process of plastics, and the problems still need to be solved. Therefore, there is an urgent need to develop efficient and sustainable technology to convert plastics into high value added products.
Polyoxometallates (POMs) are a series of transition metal oxyanion clusters that exhibit reversible multiple electron redox switching properties while maintaining a stable structure, which has led to a broad spectrum in the field of photo/electro catalysisAttention is paid. Wherein phosphovanadate molybdate (H) 5 PMo 12-n V n O 40 ) Is widely regarded as a high-efficiency catalyst for aerobic oxidation reaction, and has a Keggin structure H 5 PMo 10 V 2 O 40 The valence state of the vanadium atom in (denoted as VPOM) can be dynamically changed during the reaction, and thus has the ability to catalyze C-C bond cleavage by electron transfer-oxygen transfer reactions. However, VPOM materials have the following problems: the bandgap structure determines that the photo-generated carriers are severely compounded and have poor redox capability, which severely limits the photocatalytic application. Therefore, developing a heterojunction system based on POM is an effective strategy to solve the above problems, especially a biomimetic Z-schema heterostructure, not only promotes carrier separation, but also retains the powerful redox capability of electrons and holes.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The nano-sheet Z-type heterojunction and the preparation method and the application thereof are used for solving the problems of serious photo-generated carrier recombination, poor oxidation-reduction capability and poor photocatalysis effect of the conventional VPOM material.
The technical scheme for solving the technical problems is as follows: providing vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The Z-shaped heterojunction of the nanometer sheet, in the heterojunction, vanadium substituted phosphomolybdic acid is uniformly dispersed in g-C in the form of nanometer clusters 3 N 4 The surface of the nano-sheet has photo-generated charge in vanadium to replace phosphomolybdic acid and g-C 3 N 4 And on the interface of the nano sheet, the nano sheet is transmitted through a Z-shaped transmission route.
The beneficial effects of the invention are as follows: in the VPOM/CNNS heterojunction, VPOM is uniformly dispersed on the surface of CNNS in the form of ultra-small nano clusters, and photo-generated charges are transmitted on the interfaces of the VPOM and the CNNS through a Z-type transmission mechanism, so that the efficient separation of electrons and holes is facilitated, the carrier recombination is reduced, the strong reducibility of the CNNS and the strong oxidizing property of the VPOM are fully utilized, sufficient high-energy charges are provided for photocatalytic activation of plastics, the plastic polymers can be efficiently catalytically activated at normal temperature and normal pressure by utilizing light energy, and the photo-generated charges are converted into formic acid, so that the purposes of simultaneously eliminating plastic wastes and synthesizing renewable chemicals are achieved.
The invention also provides the vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The preparation method of the Z-shaped heterojunction of the nano sheet comprises the following steps:
(1) NaVO is processed 3 And Na (Na) 2 HPO 4 Dissolving in boiling water, adding concentrated sulfuric acid dropwise, stirring, and adding Na 2 MoO 4 And concentrating sulfuric acid for the second time to obtain a mixture, extracting with diethyl ether, and removing diethyl ether to obtain VPOM powder;
(2) Roasting urea to obtain block-shaped g-C 3 N 4 Grinding the solid, and then roasting the ground solid for the second time to obtain g-C 3 N 4 A nanosheet;
(3) g-C obtained in the step (2) 3 N 4 Dispersing the nano-sheets into HCl solution, performing ultrasonic treatment, adding the VPOM powder prepared in the step (1), stirring for 10-15h, and sequentially performing filtration, washing and freeze drying to obtain vanadium-substituted phosphomolybdic acid/g-C 3 N 4 Nanoplate Z-type heterojunction.
Based on the technical scheme, the invention can also be improved as follows:
further, naVO 3 、Na 2 HPO 4 、Na 2 MoO 4 The molar volume ratio of the boiling water, the concentrated sulfuric acid and the secondary concentrated sulfuric acid is 0.01-0.05mol:1-10mmol:0.02-0.1mol:20-40mL:0.5-2mL:8-9mL.
Further, in the step (1), the diethyl ether is removed by air drying.
Further, in the step (2), roasting is performed for 3.5-4.5 hours at the temperature of 520-550 ℃.
Further, the roasting heating rate is 4-6 ℃/min.
Further, in the step (2), the secondary roasting is carried out for 1.5 to 2.5 hours at the temperature of 480 to 510 ℃.
Further, the temperature rising rate of the secondary roasting is 4-6 ℃/min.
Further, in the step (2), both the roasting is performed under an air atmosphere.
Further, in the step (3), g-C 3 N 4 Nanoplatelets, VPOM powdersThe mass volume ratio of the HCl solution is 100mg:10-25mg:100mL.
Further, the pH of the HCl solution is 2-4.
Further, in the step (3), the ultrasonic treatment is performed for 25-35min.
Further, in the step (3), the filtrate is washed until the pH value is neutral.
The invention also provides the vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The application of the Z-shaped heterojunction of the nano sheet in the aspect of plastic photocatalytic degradation.
The invention also provides a photocatalytic degradation method of plastics, which comprises the following steps: acetonitrile, plastics and vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The Z-shaped heterojunction of the nano sheet is mixed, and reacts under the conditions of oxygen atmosphere and illumination, so that the plastic is degraded into formic acid by photocatalysis.
Further, acetonitrile, plastic and vanadium substituted phosphomolybdic acid/g-C 3 N 4 The volume mass ratio of the Z-shaped heterojunction of the nano sheet is 8-12mL:18-22mg:8-12mg.
Further, the plastic is polyethylene, polypropylene, polyacrylamide, polyvinyl chloride or polyethylene glycol.
The invention has the following beneficial effects:
1. the VPOM/CNNS heterojunction has high-efficiency photocatalytic degradation activity on various plastic polymers, successfully converts plastics into high-added-value industrial product formic acid, and has good catalytic stability. The invention uses cheap nontoxic semiconductor g-C 3 N 4 And the narrow forbidden band vanadium substituted phosphomolybdic acid form a VPOM/CNNS semiconductor Z-type heterojunction through electrostatic interaction, and CNNS (g-C) 3 N 4 Nanoplatelets) and VPOM (vanadium substituted phosphomolybdic acid) semiconductors show good absorption to solar spectrum, the photo-generated charge separation efficiency is improved, the carrier recombination probability is greatly reduced, and sufficient high-energy charge is provided for photo-catalytic activation of plastics, so that the catalytic activity is improved.
2. The VPOM/CNNS semiconductor Z-type heterojunction is prepared by adopting the electrostatic self-assembly method, and the preparation method has the characteristics of convenience in operation, simple process, low cost and environment friendliness, and is suitable for industrialized mass production in the future.
3. The VPOM/CNNS semiconductor Z-type heterojunction photocatalyst can catalyze and activate plastic polymers at normal temperature and normal pressure, and can be converted into formic acid, so that a new thought is provided for sustainable reuse of future plastics, and potential application value is provided.
4. The invention provides vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The nano-sheet Z-type heterojunction is a phosphomolybdic acid group Z-type heterojunction system reported for the first time at present, and the preparation method has the advantages of convenient operation, simple process, low price and easy obtainment of raw materials, and accords with the green development concept; phosphomolybdic acid and g-C according to the invention 3 N 4 The Z-type charge transmission mechanism between the nano sheets can fully retain the strong reducibility of photo-generated electrons and the strong oxidability of photo-generated holes generated in the heterojunction, realize the high-efficiency separation of electrons and holes, greatly reduce the carrier recombination probability and provide sufficient high-energy charge for the photocatalytic activation of plastics; the VPOM/CNNS heterojunction photocatalyst provided by the invention can catalyze and activate plastic polymers at normal temperature and normal pressure, and convert the plastic polymers into formic acid, so that a new thought is provided for sustainable reuse of future plastics, and a sustainable and extensible strategy is provided for simultaneously eliminating plastic waste and synthesizing renewable chemicals.
Drawings
FIG. 1 is a TEM spectrum of the heterojunction prepared in example 1;
FIG. 2 is a FTIR spectrum of the heterojunction made in example 1;
FIG. 3 is a schematic diagram of heterojunction Z-type charge transport prepared in example 1;
FIG. 4 is a graph of the catalytic performance of the heterojunction made in examples 1 and 7-9;
FIG. 5 is a graph of heterojunction stability testing prepared in example 1.
Detailed Description
The principles and features of the present invention are described below with reference to the drawings, the examples are illustrated for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
Example 1:
vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The preparation method of the Z-shaped nano-sheet heterojunction comprises the following steps:
(1) 0.02mol of NaVO 3 And 5mmol of Na 2 HPO 4 Dissolving in 30mL boiling water, adding 1mL concentrated sulfuric acid dropwise to obtain red solution, adding 0.05mol Na under stirring 2 MoO 4 And 8.5mL of second concentrated sulfuric acid, transferring the obtained mixture to a separating funnel containing diethyl ether, collecting a bottom solution, and air-drying to remove diethyl ether to obtain orange VPOM powder;
(2) Roasting urea for 4 hours at 520 ℃ in an air atmosphere, wherein the heating rate is 5 ℃/min, and completing the first roasting to obtain blocky g-C 3 N 4 Grinding the solid uniformly, roasting for 2 hours at 500 ℃ with the temperature rising rate of 5 ℃/min, and completing the second roasting to obtain the g-C 3 N 4 Nanoplatelets (CNNS);
(3) 100mg of g-C obtained in step (2) was added 3 N 4 Dispersing the nanosheets into 100mL of HCl solution with pH value of 3, carrying out ultrasonic treatment, then adding 15mg of VPOM powder prepared in the step (1), carrying out vigorous stirring for 12h, filtering, washing until the pH value of the filtrate is neutral, and carrying out freeze drying to obtain vanadium-substituted phosphomolybdic acid/g-C 3 N 4 Nanoplate Z-heterojunction (VPOM/CNNS-15).
A method for photocatalytic degradation of plastics comprises the following steps:
10mL of acetonitrile, 20mg of polyethylene and 10mg of the vanadium-substituted phosphomolybdic acid/g-C described above 3 N 4 The Z-shaped heterojunction of the nano sheet is mixed, oxygen is introduced for 30min under the stirring condition, air in the system is discharged, a 300W Xe lamp (provided with a 420nm cut-off filter) provides a light source, the reaction is carried out for 36h, and the plastic is degraded into formic acid by photocatalysis.
Example 2:
vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The preparation method of the Z-shaped nano-sheet heterojunction comprises the following steps:
(1) 0.01mol of NaVO 3 And 1mmol of Na 2 HPO 4 Dissolving in 20mL boiling water, adding 0.5mL concentrated sulfuric acid dropwise to obtain red solution, adding 0.02mol Na under stirring 2 MoO 4 And 8mL of second concentrated sulfuric acid, transferring the obtained mixture into a separating funnel containing diethyl ether, collecting a bottom solution, and air-drying to remove diethyl ether to obtain orange VPOM powder;
(2) Roasting urea for 4.5 hours under the condition of 520 ℃ in an air atmosphere, wherein the heating rate is 4 ℃/min, and completing the first roasting to obtain a block-shaped g-C 3 N 4 Grinding the solid uniformly, roasting for 2.5 hours at 480 ℃ with the temperature rising rate of 4 ℃/min, and completing the second roasting to obtain the g-C 3 N 4 A nanosheet;
(3) 100mg of g-C obtained in step (2) was added 3 N 4 Dispersing the nanosheets into 100mL of HCl solution with pH value of 2, carrying out ultrasonic treatment, then adding 10mg of VPOM powder prepared in the step (1), carrying out vigorous stirring for 10h, filtering, washing until the pH value of the filtrate is neutral, and carrying out freeze drying to obtain vanadium-substituted phosphomolybdic acid/g-C 3 N 4 Nanoplate Z-type heterojunction.
A method for photocatalytic degradation of plastics comprises the following steps:
10mL of acetonitrile, 18mg of polyethylene and 8mg of the vanadium-substituted phosphomolybdic acid/g-C described above 3 N 4 The Z-shaped heterojunction of the nano sheet is mixed, oxygen is introduced for 30min under the stirring condition, air in the system is discharged, a 300W Xe lamp (provided with a 420nm cut-off filter) provides a light source, the reaction is carried out for 36h, and the plastic is degraded into formic acid by photocatalysis.
Example 3:
vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The preparation method of the Z-shaped nano-sheet heterojunction comprises the following steps:
(1) 0.05mol of NaVO is reacted with 3 And 10mmol of Na 2 HPO 4 Dissolving in 40mL boiling water, adding 2mL concentrated sulfuric acid dropwise to obtain red solution, adding 0.1mol Na under stirring 2 MoO 4 And 9mL of second concentrated sulfuric acid, transferring the obtained mixture to a separating funnel containing diethyl ether, collecting the bottom solution, and air-drying to removeDiethyl ether, to give orange VPOM powder;
(2) Roasting urea for 3.5 hours at 550 ℃ in an air atmosphere, wherein the heating rate is 6 ℃/min, and completing the first roasting to obtain a block g-C 3 N 4 Grinding the solid uniformly, roasting for 1.5h at 510 ℃ with the heating rate of 6 ℃/min, and completing the second roasting to obtain the g-C 3 N 4 A nanosheet;
(3) 100mg of g-C obtained in step (2) was added 3 N 4 Dispersing the nanosheets into 100mL of HCl solution with pH value of 4, carrying out ultrasonic treatment, then adding 25mg of VPOM powder prepared in the step (1), vigorously stirring for 10-15h, filtering, washing until the pH value of the filtrate is neutral, and freeze-drying to obtain vanadium-substituted phosphomolybdic acid/g-C 3 N 4 Nanoplate Z-type heterojunction.
A method for photocatalytic degradation of plastics comprises the following steps:
10mL of acetonitrile, 18-22mg of polyethylene and 8-12mg of vanadium-substituted phosphomolybdic acid/g-C as described above 3 N 4 The Z-shaped heterojunction of the nano sheet is mixed, oxygen is introduced for 30min under the stirring condition, air in the system is discharged, a 300W Xe lamp (provided with a 420nm cut-off filter) provides a light source, the reaction is carried out for 36h, and the plastic is degraded into formic acid by photocatalysis.
Examples 4-6:
vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The preparation method of the Z-shaped nano-sheet heterojunction comprises the following steps:
in the step (2), the first firing temperatures were 530 ℃, 540 ℃ and 550 ℃, respectively, and the rest was the same as in example 1.
A method for photocatalytic degradation of plastics comprises the following steps:
the vanadium-substituted phosphomolybdic acid/g-C is adopted respectively 3 N 4 The nanosheet Z-type heterojunction was the same as in example 1.
Examples 7 to 9:
vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The preparation method of the Z-shaped nano-sheet heterojunction comprises the following steps:
in the step (3), 10mg, 20mg and 25mg of the VPOM powder prepared in the step (1) were added, respectively, and the rest was the same as in example 1.
A method for photocatalytic degradation of plastics comprises the following steps:
the vanadium-substituted phosphomolybdic acid/g-C is adopted respectively 3 N 4 The nanosheet Z-type heterojunction was the same as in example 1.
Examples 10 to 13:
vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The preparation method of the Z-shaped nano-sheet heterojunction comprises the following steps:
as in example 1.
A method for photocatalytic degradation of plastics comprises the following steps:
the plastics are polypropylene, polyacrylamide, polyvinyl chloride and polyethylene glycol, respectively, with the remainder being the same as in example 1.
Comparative example 1:
g-C 3 N 4 The preparation method of the Z-shaped nano-sheet heterojunction comprises the following steps:
in the step (3), the VPOM powder obtained in the step (1) was not added, and the rest was the same as in example 1.
Test examples
1. The heterojunction prepared in example 1 was subjected to TEM, FTIR and Z-type charge transfer detection, and the results are shown in FIGS. 1-3.
As can be seen from FIG. 1, the VPOM/CNNS-15 exhibits a typical dispersed platelet structure with lateral dimensions of hundreds of nanometers, and on an enlarged scale, the CNNS platelet layer is dispersed with ultra-small size VPOM clusters of bright spots without the generation of agglomerated bulk particles.
As can be seen from FIG. 2, there is a vibration characteristic peak (809 cm -1 ，1150-1600cm -1 And 2900-3400cm -1 ) And the vibration characteristic peaks of VPOM at wave numbers 1059, 959, 864, 790 and 603cm, respectively -1 Is due to P-O a 、Mo-O b 、Mo-O c -Mo、Mo-O d -asymmetric stretching vibration signal of Mo and V-O bonds.
As can be seen from fig. 3, the bandgap structures of VPOM and CNNS in VPOM/CNNS-15, due to the difference of fermi levels, cause charge transfer at the interface of contact, and electrons flow from CNNS with higher fermi level onto VPOM material with low fermi level until the fermi level is balanced; the transfer of charge causes a built-in electric field to form at the interface, the direction pointing from CNNS to VPOM; when excited by light, CNNS and VPOM are simultaneously excited to generate electron-hole, and driven by built-in electric field, photo-generated electrons flow from CB of VPOM to VB of CNNS to form Z-type charge transmission mechanism, so that strong reducing power of photo-generated electrons of CNNS and strong oxidizing power of photo-generated holes on VB in VPOM are maintained.
2. The formic acid yield obtained in examples 1 and 7-9 was examined, 1mL of the reaction mixture was taken every 6 hours, filtered with a 0.22 μm Nylon syringe filter, and the reaction product was tested by HPLC as formic acid HCOOH, as shown in FIG. 4 (at 36h on the abscissa, examples 1, 7-9 on the ordinate from top).
As can be seen from fig. 4, VPOM plays an important role in the photocatalytic rate conversion reaction, as the mass fraction of VPOM in the VPOM/CNNS heterojunction catalyst increases, the performance of the VPOM in the photocatalytic plastic degradation conversion to formic acid tends to increase and decrease, and when the mass fraction of VPOM is 15%, the formic acid yield is 24.66 μmol h -1 g -1 。
3. The stability of the heterojunction of example 1 for long-term conversion was examined and the results are shown in fig. 5.
As can be seen from fig. 5, the formic acid content in the product increased linearly with the increase of the reaction time, and the formic acid production rate remained stable, indicating that the catalyst did not undergo degradation during the long-term reaction, indicating that the reaction had good stability.
4. The yield of formic acid from examples 1, 4-13 was examined, 1mL of the reaction mixture was taken every 6 hours, filtered through a 0.22 μm Nylon syringe filter, and the reaction product was tested by HPLC as formic acid HCOOH, the results of which are shown in Table 1.
TABLE 1 yield of formic acid
| Product(s) | Yield/. Mu.mol h -1 g -1 | |
| Example 1 | Formic acid | 24.66 |
| Example 4 | Formic acid | 20.99 |
| Example 5 | Formic acid | 17.29 |
| Example 6 | Formic acid | 11.99 |
| Example 7 | Formic acid | 20.15 |
| Example 8 | Formic acid | 17.64 |
| Example 9 | Formic acid | 14.78 |
| Example 10 | Formic acid | 26.68 |
| Example 11 | Formic acid | 156.57 |
| Example 12 | Formic acid | 29.85 |
| Example 13 | Formic acid | 208.65 |
As can be seen from Table 1, the degradation and conversion of photocatalytic plastics into formic acid is closely related to the VPOM content of the VPOM/CNNS heterojunction catalyst, the calcination temperature of CNNS in the catalyst, and the properties of the plastic substrate. With the increase of the VPOM mass fraction, the performance of the VPOM in carrying out photocatalytic plastic degradation and conversion into formic acid tends to be increased and then reduced; the higher the burnt temperature of CNNS in the catalyst is, the higher the stripping degree of CNNS is, resulting in the reduction of the formic acid content in the product; in the degradation reaction of various plastic substrates, the degradation difficulty of polyacrylamide and polyethylene glycol is low, and the formic acid plastic produced by conversion is higher.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (10)
1. Vanadium-substituted phosphomolybdic acid/g-C 3 N 4 The Z-shaped heterojunction of the nano sheet is characterized in that in the heterojunction, vanadium-substituted phosphomolybdic acid is uniformly dispersed in g-C in the form of nano clusters 3 N 4 The surface of the nano-sheet has photo-generated charge in vanadium to replace phosphomolybdic acid and g-C 3 N 4 On the interface of the nano sheet, the Z-shaped transmission route is adopted for carrying outAnd (5) transmission.
2. Vanadium substituted phosphomolybdic acid/g-C according to claim 1 3 N 4 The preparation method of the Z-shaped heterojunction of the nanosheet is characterized by comprising the following steps of:
(1) NaVO is processed 3 And Na (Na) 2 HPO 4 Dissolving in boiling water, adding concentrated sulfuric acid dropwise, stirring, and adding Na 2 MoO 4 And concentrating sulfuric acid for the second time to obtain a mixture, extracting with diethyl ether, and removing diethyl ether to obtain VPOM powder;
(2) Roasting urea to obtain block-shaped g-C 3 N 4 Grinding the solid, and then roasting the ground solid for the second time to obtain g-C 3 N 4 A nanosheet;
(3) g-C obtained in the step (2) 3 N 4 Dispersing the nano-sheets into HCl solution, performing ultrasonic treatment, adding the VPOM powder prepared in the step (1), stirring for 10-15h, and sequentially performing filtration, washing and freeze drying to obtain vanadium-substituted phosphomolybdic acid/g-C 3 N 4 Nanoplate Z-type heterojunction.
3. Vanadium substituted phosphomolybdic acid/g-C according to claim 2 3 N 4 The preparation method of the Z-shaped heterojunction of the nanosheet is characterized by comprising the following steps of (1) NaVO 3 、Na 2 HPO 4 、Na 2 MoO 4 The molar volume ratio of the boiling water, the concentrated sulfuric acid and the secondary concentrated sulfuric acid is 0.01-0.05mol:1-10mmol:0.02-0.1mol:20-40mL:0.5-2mL:8-9mL.
4. Vanadium substituted phosphomolybdic acid/g-C according to claim 2 3 N 4 The preparation method of the Z-type heterojunction of the nanosheet is characterized in that in the step (2), the nanosheet is baked for 3.5-4.5 hours at the temperature of 520-550 ℃.
5. Vanadium substituted phosphomolybdic acid/g-C according to claim 2 3 N 4 The preparation method of the Z-shaped heterojunction of the nanosheet is characterized by comprising the step (2) of carrying out secondary roasting for 1.5-2.5 hours at 480-510 ℃.
6. Vanadium substituted phosphomolybdic acid/g-C according to claim 2 3 N 4 The preparation method of the Z-shaped heterojunction of the nanosheet is characterized by comprising the following steps of (3) g-C 3 N 4 The mass volume ratio of the nano-sheet, the VPOM powder and the HCl solution is 100mg:10-25mg:100mL.
7. Vanadium substituted phosphomolybdic acid/g-C according to claim 2 3 N 4 The preparation method of the Z-shaped heterojunction of the nanosheet is characterized by comprising the step (3) of washing until the pH value of filtrate is neutral.
8. The vanadium-substituted phosphomolybdic acid/g-C of claim 1 3 N 4 The application of the Z-shaped heterojunction of the nano sheet in the aspect of plastic photocatalytic degradation.
9. A method for photocatalytic degradation of plastics is characterized by comprising the following steps: acetonitrile, plastic and vanadium-substituted phosphomolybdic acid/g-C according to claim 1 3 N 4 The Z-shaped heterojunction of the nano sheet is mixed, and reacts under the conditions of oxygen atmosphere and illumination, so that the plastic is degraded into formic acid by photocatalysis.
10. The method of photocatalytic degradation of plastic according to claim 9, wherein the plastic is polyethylene, polypropylene, polyacrylamide, polyvinyl chloride or polyethylene glycol.
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| Title |
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| CHUANWANG XING ET AL: ""Solar energy-driven upcycling of plastic waste on direct Z-scheme heterostructure of V-substituted phosphomolybdic acid/g-C3N4 nanosheets"", 《APPLIED CATALYSIS B: ENVIRONMENTAL》, vol. 315, 11 May 2022 (2022-05-11), pages 1 - 2, XP087104405, DOI: 10.1016/j.apcatb.2022.121496 * |
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