Disclosure of Invention
The invention aims to provide a BiVO4@CdIn2S4/g-C3N4Preparation method of visible light response photocatalyst, g-C3N4The multicomponent metallic sulfide CdIn2S4And BiVO4A heterojunction composite system is constructed, and the photo-generated charge separation efficiency is improved, so that the photo-catalytic effect is good.
Another object of the present invention is to provide a BiVO4@CdIn2S4/g-C3N4The visible light responds to the photocatalyst, and the photocatalyst has good photocatalytic performance and high hydrogen production effect.
The technical problem to be solved by the invention is realized by adopting the following technical scheme.
The invention provides a BiVO4@CdIn2S4/g-C3N4The preparation method of the visible light response photocatalyst comprises the following steps:
few-lamellar layer g-C3N4Preparation: calcining carbon nitride precursor to obtain low-sheet g-C3N4;
Monolithic or minority layer CdIn2S4Preparation: respectively dissolving divalent cadmium salt, trivalent indium salt and thioacetamide in a first solvent according to a molar ratio, mixing, heating at 140-200 ℃ for 22-30h, and separating, washing, drying and grinding to obtain a reaction product; placing the reaction product in a mixed solution, heating and refluxing for 1-3 h to obtain single-chip or few-chip CdIn2S4Wherein the mixed solution is an aqueous solution containing sodium bicarbonate, isopropanol and polyvinyl pyrrolidone;
CdIn2S4/g-C3N4preparation of a mixture: subjecting said g-C to3N4And the CdIn2S4Mixing the obtained product in a second solvent, evaporating the second solvent to dryness, and drying to obtain CdIn2S4/g-C3N4Mixing;
BiVO4@CdIn2S4/g-C3N4preparation: dissolving trivalent bismuth salt in an acetic acid solution to obtain a first solution, dissolving ammonium metavanadate in an ammonia water solution to obtain a second solution, and slowly mixing the first solution and the second solution to obtain a third solution; adjusting the pH value of the third solution to 7-8, stirring for 30-60 min, and adding the CdIn 2S4/g-C3N4Ultrasonically dispersing the mixture, reacting for 2-4h at 140-200 ℃, cooling, separating, washing, drying and grinding to obtain BiVO4@CdIn2S4/g-C3N4The visible light is responsive to the photocatalyst.
Further, in a preferred embodiment of the present invention, the step of calcining the carbon nitride precursor comprises:
heating to 500-550 ℃ at a first heating rate, calcining for 1-3 h, and cooling and grinding the obtained calcined product to obtain a first calcined substance; then, the user can use the device to perform the operation,
heating the first calcined substance to 500-550 ℃ at a second heating rate, calcining for 1-3 h, cooling and grinding the calcined product to obtain the few-lamellar g-C3N4。
Further, in a preferred embodiment of the present invention, the first temperature-raising speed is 1 to 2 ℃/min, and the second temperature-raising speed is 3 to 5 ℃/min.
Further, in a preferred embodiment of the present invention, the carbon nitride precursor is selected from one or more of urea, cyanamide, dicyandiamide and melamine.
Further, in a preferred embodiment of the present invention, the first solvent is an ethanol aqueous solution.
Further, in a preferred embodiment of the present invention, the concentration of the sodium bicarbonate in the mixed solution is 0.1 to 0.2g/ml, the volume concentration of the isopropanol is 8 to 12% v/v, and the concentration of the polyvinylpyrrolidone is 4 to 6 mg/ml.
Further, in a preferred embodiment of the present invention, the second solvent is one or more selected from the group consisting of absolute ethanol, polyethylene glycol and pyridine.
Further, in a preferred embodiment of the present invention, CdIn2S4/g-C3N4In the step of preparing the mixture, the CdIn2S4And said g-C3N4The mass ratio of (A) to (B) is 0.3-0.8: 1.
Further, in the preferred embodiment of the present invention, BiVO4@CdIn2S4/g-C3N4In the preparation step, the CdIn2S4/g-C3N4The adding amount of the mixture in the third solution is 2-12 mg/ml.
The invention also provides BiVO4@CdIn2S4/g-C3N4The visible light response photocatalyst is prepared according to the preparation method.
BiVO of the embodiment of the invention4@CdIn2S4/g-C3N4The visible light response photocatalyst and the preparation method thereof have the beneficial effects that:
few-lamellar layer g-C3N4The photocatalyst is a polymer semiconductor visible light photocatalyst, has stable structure and hydrogen production performance by photocatalytic water decomposition, can be repeatedly used, and is environment-friendly. The few-lamellar structure provides a larger specific surface area for photocatalytic hydrolysis hydrogen production, and the quantum yield is high. Monolithic or minority layer CdIn2S4During preparation, the CdIn is effectively regulated and controlled by heating the reaction product in an aqueous solution containing sodium bicarbonate, isopropanol and polyvinyl pyrrolidone in a refluxing manner2S4The nucleation and growth of the catalyst are carried out, so that the metal sulfide with a single layer or less layers is formed, the formation of a blocky structure is avoided, and the hydrogen production efficiency is improved.
Furthermore, BiVO4The band gap is 2.40eV, the valence band and the conduction band are respectively positioned at +2.70eV and +0.30 eV, and the photo-generated electron-hole pair has stronger redox capability. Through in-situ compounding of BiVO4And CdIn2S4/g-C3N4The mixture can regulate and control the particle size of a product, construct a heterojunction composite system, improve the charge transmission capability, realize high photo-generated charge separation efficiency, prolong the service life of photo-generated carriers and ensure that the photocatalyst has a good photo-catalytic hydrogen production effect.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Following are embodiments of the present inventionBiVO (b)4@CdIn2S4/g-C3N4The visible light response photocatalyst and the preparation method thereof are concretely explained.
The embodiment of the invention provides a BiVO4@CdIn2S4/g-C3N4The preparation method of the visible light response photocatalyst comprises the following steps:
s1, few layers g-C3N4Preparation: calcining carbon nitride precursor to obtain low-sheet g-C 3N4。
Further, in this step, the step of calcining the carbon nitride precursor is: heating to 500-550 ℃ at a first heating rate, calcining for 1-3 h, cooling the obtained calcined product, and grinding to obtain a first calcined product; then heating the first calcined substance to 500-550 ℃ at a second heating rate, calcining for 1-3 h, cooling the obtained calcined product, and grinding to obtain the few-lamellar g-C3N4。
Further, in the step, the first temperature rise speed is 1-2 ℃/min; the second temperature rise speed is 3-5 ℃/min. Firstly heating to 500-550 ℃ at a lower heating rate for calcination, cooling and grinding the calcined product, then heating to 500-550 ℃ at a higher heating rate for calcination again, and thus g-C can be calcined3N4The shape of the nano-sheet is regulated, so that the nano-sheet is beneficial to driving of a nano-sheet structure, separation and transfer of photon-generated carriers are facilitated, and the hydrogen production efficiency is improved.
Further, in this step, the carbon nitride precursor is selected from one or more of urea, cyanamide, dicyandiamide, and melamine. More preferably, the carbon nitride precursor is urea.
Further, in the step, after the calcined product is cooled, grinding the calcined product by adopting zirconia balls with a ball-to-material ratio of 1:7 for 0.5-1 h. The surface stress of the product can be removed by grinding after calcination, and the particles form a few-sheet structure through repeated crushing-cold welding-crushing processes, thereby being beneficial to the rapid transmission of charges and the compounding with other components.
S2, monolithic or minority layer CdIn2S4Preparation: respectively dissolving divalent cadmium salt, trivalent indium salt and thioacetamide in a first solvent according to a molar ratio, mixing, heating at 140-200 ℃ for 22-30h, and separating, washing, drying and grinding to obtain a reaction product; placing the reaction product in a mixed solution, heating and refluxing for 1-3 h to obtain single-chip or few-chip CdIn2S4Wherein the mixed solution is an aqueous solution containing sodium bicarbonate, isopropanol and polyvinyl pyrrolidone.
Further, In the step, cadmium acetate is selected as a divalent cadmium salt, indium chloride is selected as a trivalent indium salt, and cadmium acetate, indium chloride and thioacetamide are respectively weighed according to the mass ratio of Cd to In to S being 1:2: 4.
Further, in this step, the first solvent is an aqueous ethanol solution. Under the action of alcoholic solution, a thin-layer nanosheet structure can be obtained, and the nanosheets are beneficial to separation and transfer of photon-generated carriers, so that the hydrogen production efficiency is improved.
Further, in the step, the concentration of the sodium bicarbonate in the mixed solution is 0.1-0.2 g/ml, the volume concentration of the isopropanol is 8-12% v/v, and the concentration of the polyvinylpyrrolidone is 4-6 mg/ml.
Further, in the step, the feed-liquid ratio of the reaction product to the mixed liquid is 1-10 mg/ml.
Further, in the step, the temperature of the reaction product in the mixed solution is heated and refluxed to be 80-110 ℃. The reaction product is heated and refluxed in the mixed solution, so that the sample morphology and the dispersion performance of the product are regulated and controlled, the aggregation growth of particles is avoided, and the obtained CdIn2S4The structure is a single-layer structure or a few-layer structure, the specific surface area is larger, and more reactive sites can be provided.
S3,CdIn2S4/g-C3N4Preparation of a mixture: subjecting said g-C to3N4And the CdIn2S4Mixing the obtained product in a second solvent, evaporating the second solvent to dryness, and drying to obtain CdIn2S4/g-C3N4And (3) mixing.
Further, in the step, the second solvent is one or more selected from the group consisting of absolute ethyl alcohol, polyethylene glycol and pyridine. More preferably, the second solvent is selected from anhydrous ethanol.
Further, in the step, a rotary evaporator is adopted to evaporate the second solvent to dryness, the rotary evaporation temperature is 40-50 ℃, and the second solvent is dried for 6 hours at the temperature of 60 ℃ after evaporation to dryness, so that the composite few-piece layer CdIn is obtained2S4/g-C3N4And (3) mixing.
Further, in this step, CdIn2S4And g-C3N4In a mass ratio of 0.3 to 0.8:1, more preferably, CdIn2S4And g-C3N4The mass ratio of (A) to (B) is 0.6: 1.
CdIn by rotary evaporation in absolute ethanol solution2S4And g-C3N4The process is simple, the solvent can be recovered, and the reaction condition is mild.
S4,BiVO4@CdIn2S4/g-C3N4Preparation: dissolving trivalent bismuth salt in an acetic acid solution to obtain a first solution, dissolving ammonium metavanadate in an ammonia water solution to obtain a second solution, and slowly mixing the first solution and the second solution to obtain a third solution; adjusting the pH value of the third solution to 7-8, stirring for 30-60 min, and adding the CdIn2S4/g-C3N4Ultrasonically dispersing the mixture, reacting for 2-4h at 140-200 ℃, cooling, separating, washing, drying and grinding to obtain BiVO4@CdIn2S4/g-C3N4The visible light is responsive to the photocatalyst.
Further, in this step, the trivalent bismuth salt is selected from one or more of bismuth nitrate, bismuth chloride, bismuth acetate, and bismuth citrate. More preferably, the trivalent bismuth salt is bismuth nitrate. The acetic acid solution is a mixed solution of acetic acid and water in a volume ratio of 1: 1. The concentration of bismuth nitrate in the acetic acid solution is 2-5 mol/L.
Further, in this step, the aqueous ammonia solution was a mixed solution of aqueous ammonia (containing 25 wt% of ammonia) and water in a volume ratio of 3: 1. The concentration of the ammonium metavanadate in the ammonia water solution is 2-5 mol/L.
Further, in the step, adjusting the pH value of the third solution to 7-8 by using ammonia water, specifically, adjusting the process as follows: and (3) firstly adding 20ml of ammonia water in the adjusting process, and then slowly dropwise adding the ammonia water until the pH value is 7-8.
Further, in this step, CdIn2S4/g-C3N4The addition amount of the mixture in the third solution is 2-12 mg/ml, and more preferably, CdIn2S4/g-C3N4The adding amount of the mixture in the third solution is 8-10 mg/ml.
Further, in the step, the ultrasonic dispersion condition is that the ultrasonic dispersion is carried out for 1-2 hours under the power of 400-600W. Under the action of ultrasonic waves, the size of a product can be effectively reduced, and the product is degraded into a nano-sheet structure.
BiVO4The band gap is 2.40eV, the valence band and the conduction band are respectively positioned at +2.70eV and +0.30eV, and the photo-generated electron-hole pair has stronger redox capability. By hydrothermal reaction, in CdIn2S4/g-C3N4BiVO is coated on the surface of the mixture4Form BiVO4@CdIn2S4/g-C3N4The core-shell structure is more beneficial to charge transfer between interfaces, inhibits the recombination of photon-generated carriers and improves the photocatalytic activity.
The embodiment of the invention also provides BiVO4@CdIn2S4/g-C3N4The visible light response photocatalyst is prepared according to the preparation method.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
BiVO provided by the embodiment4@CdIn2S4/g-C3N4A visible light-responsive photocatalyst, prepared according to the steps of:
(1) 10g of urea was placed in an alumina crucible with a lid and placed in a muffle furnace at a rate of 1 ℃/min Heating to 550 deg.C, holding for 2h, naturally cooling to room temperature, grinding for 0.5h to obtain sample, placing into aluminum oxide crucible with cover, heating to 500 deg.C at 4 deg.C/min in muffle furnace, holding for 3h, naturally cooling to room temperature, grinding for 0.5h to obtain few-lamellar g-C3N4And (3) powder.
(2) Under the condition of room temperature, cadmium acetate, indium chloride and thioacetamide are weighed according to the mass ratio of Cd to In to S of 1:2:4 and are respectively dissolved In 30ml of ethanol water solution, the mixture is magnetically stirred for 30min, the mixture is transferred into a polytetrafluoroethylene lining, and then the polytetrafluoroethylene lining is placed into a stainless steel reaction kettle and is heated and reacted for 24h at the temperature of 180 ℃. After the reaction is finished, centrifuging at 1000rpm for 30min, washing with deionized water for 3 times, then washing with absolute ethyl alcohol for three times, drying at 60 ℃ for 12 hours, and grinding to obtain a reaction product A.
(3) Adding the reaction product A in the step (2) into a reflux device which is connected with a condensation pipe and a 500ml three-neck flask with a thermometer, adding 10g of sodium bicarbonate, 10ml of isopropanol, 0.5g of polyvinylpyrrolidone and 100ml of deionized water, placing on an electric heating sleeve with magnetic stirring for heating and refluxing for 2h, filtering, washing for 3 times by using the deionized water, then washing for three times by using absolute ethyl alcohol to obtain single-piece or few-piece layer CdIn 2S4And (3) powder.
(4) The obtained CdIn2S4And g-C3N4Mixing the sample in 50ml of absolute ethyl alcohol according to the mass ratio of 0.6:1, evaporating to dryness in a vacuum rotary evaporator, and drying in a drying oven at 60 ℃ for 6h to obtain the composite few-layer CdIn2S4/g-C3N4And (3) mixing.
(5) In volume ratio V(acetic acid):V(Water)1: 1 preparing acetic acid solution, accurately weighing 1g of bismuth nitrate and dissolving in the acetic acid solution, and magnetically stirring for 20min to fully dissolve the bismuth nitrate. In volume ratio V(Ammonia water):V(Water)3: 1 preparing an ammonia water solution, accurately weighing 0.2g of ammonium metavanadate and dissolving the ammonium metavanadate in the ammonia water solution, and completely dissolving the ammonium metavanadate by magnetic stirring for 20 min.
(6) Slowly mixing the two solutions in the step (5), magnetically stirring for 1h, and adjusting pH to 7 with ammonia water (adding the solution during the adjustment process)20mL of ammonia water, slowly adding dropwise until the pH is 7), and adding CdIn after continuously stirring for 0.5h2S4/g-C3N4Ultrasonically dispersing the mixture for 1h, transferring the mixture into a high-pressure reaction kettle container containing a polytetrafluoroethylene lining, reacting for 3h at 160 ℃, cooling the sample to room temperature, taking out the sample, placing the sample into a centrifuge tube, centrifuging, repeatedly washing with distilled water and absolute ethyl alcohol for three times, drying at 60 ℃ for 18h, and grinding to obtain BiVO4@CdIn2S4/g-C3N4The visible light responds to the photocatalyst sample.
Example 2
BiVO provided by the embodiment4@CdIn2S4/g-C3N4A visible-light-responsive photocatalyst, which is different from example 1 in that:
the step (1) is as follows: putting 10g of urea into an alumina crucible with a cover, heating to 550 ℃ in a muffle furnace at the speed of 1 ℃/min, preserving heat for 5h, naturally cooling to room temperature, taking out and grinding for 1h to obtain g-C3N4And (3) powder.
Comparative example 1
This comparative example provides a CdIn2S4/g-C3N4Visible light-responsive photocatalyst, CdIn obtained according to the method of example 12S4/g-C3N4And (3) mixing.
Comparative example 2
This comparative example provides a visible light responsive photocatalyst, obtained according to the following steps:
(1) less lamellar g-C was obtained according to step (1) of example 13N4And (3) powder.
(2) The reaction product a was obtained according to the step (2) of example 1.
(3) The reaction products A and g-C obtained3N4Mixing the sample in 50ml of absolute ethyl alcohol, evaporating to dryness in a vacuum rotary evaporator, and drying in a drying oven at 60 ℃ for 6h to obtain the composite few-lamellar layer CdIn2S4/g-C3N4And (3) mixing.
(4) According to the procedure of the examples(5) And step (6) of obtaining BiVO4@CdIn2S4/g-C3N4The visible light responds to the photocatalyst sample.
Comparative example 3
This comparative example provides a visible light responsive photocatalyst, obtained according to the following steps:
(1) less lamellar g-C was obtained according to step (1) of example 1 3N4And (3) powder.
(2) The less lamellar CdIn was obtained according to the steps (2) and (3) of example 12S4And (3) powder.
(3) In volume ratio V(acetic acid):V(Water)1: 1 preparing acetic acid solution, accurately weighing 1g of bismuth nitrate and dissolving in the acetic acid solution, and magnetically stirring for 20min to fully dissolve the bismuth nitrate. In volume ratio V(Ammonia water):V(Water)3: 1 preparing an ammonia water solution, accurately weighing 0.2g of ammonium metavanadate and dissolving the ammonium metavanadate in the ammonia water solution, and completely dissolving the ammonium metavanadate by magnetic stirring for 20 min.
(4) Slowly mixing the two solutions in the step (3), magnetically stirring for 1h, adjusting the pH to 7 with ammonia water (adding 20mL of ammonia water during the adjustment process, then slowly dropwise adding until the pH is 7), and adding the few-lamellar g-C obtained in the step (1) after continuously stirring for 0.5h3N4Powder and the little-sheet layer CdIn obtained in the step (2)2S4Performing ultrasonic dispersion on the powder for 1h, transferring the powder into a high-pressure reaction kettle container with a polytetrafluoroethylene lining, reacting for 3h at 160 ℃, cooling the sample to room temperature, taking out the sample, placing the sample into a centrifuge tube, centrifuging, repeatedly washing with distilled water and absolute ethyl alcohol for three times, drying for 18h at 60 ℃, and grinding to obtain BiVO4@CdIn2S4/g-C3N4The visible light responds to the photocatalyst sample.
Test examples measurement of Hydrogen production Performance
The products obtained in examples 1-2 and comparative examples 1-3 were used as catalysts for photocatalytic reactions carried out in a 500mL Pyrex reactor system at a temperature of 25 ℃. The photocatalyst was added to an aqueous solution containing methanol as a reaction medium. The reaction medium is placed in a photoreactor. After the reaction system was purged with argon for 30min, the system was illuminated with visible light (420< lambda < 800nm) for 4h using a 300W xenon lamp (fitted with a filter) that surrounded the side of the photoreactor. Condensed water is introduced in the reactor in an external circulation manner. The photocatalytic effects of the five samples are shown in table 1:
TABLE 1
Sample (I)
|
Average hydrogen production rate (first use)
|
Average hydrogen production rate (after 20 times of use)
|
Example 1
|
519.2μmol/(h·g)
|
488.0μmol/(h·g)
|
Example 2
|
457.4μmol/(h·g)
|
416.2μmol/(h·g)
|
Comparative example 1
|
361.3μmol/(h·g)
|
130.1μmol/(h·g)
|
Comparative example 2
|
422.5μmol/(h·g)
|
219.7μmol/(h·g)
|
Comparative example 3
|
417.6μmol/(h·g)
|
186.2μmol/(h·g) |
The embodiments described above are some, but not all embodiments of the invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.