CN114011394B - Nonmetallic composite photocatalytic material and preparation and application thereof - Google Patents

Nonmetallic composite photocatalytic material and preparation and application thereof Download PDF

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CN114011394B
CN114011394B CN202111398636.2A CN202111398636A CN114011394B CN 114011394 B CN114011394 B CN 114011394B CN 202111398636 A CN202111398636 A CN 202111398636A CN 114011394 B CN114011394 B CN 114011394B
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siqds
ultrasonic
centrifuging
elution
crushing
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CN114011394A (en
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肖咪
徐颖峰
冯华军
吴梦然
谢茜青
郭薇
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Zhejiang Gongshang University
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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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • 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—
    • 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
    • B01J37/34—Irradiation by, or application of, electric, magnetic or wave energy, e.g. ultrasonic waves ; Ionic sputtering; Flame or plasma spraying; Particle radiation
    • B01J37/348—Electrochemical processes, e.g. electrochemical deposition or anodisation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/40—Carbon monoxide

Abstract

The invention discloses a nonmetallic composite photocatalytic material, a preparation method and an application thereof, wherein the composite photocatalytic material comprises C 3 N 4 And is loaded at C 3 N 4 Silicon quantum dots, siQDs, on the surface; dispersing commercial silicon powder in an organic solvent, performing ultrasonic crushing, centrifuging after crushing, and performing gradient ultrasonic elution on the supernatant for a plurality of times; centrifuging to obtain a precipitate after the last ultrasonic elution, and freeze-drying the obtained precipitate to obtain silicon quantum dots SiQDs; dispersing silicon quantum dots SiQDs in pure water after nitrogen blowing to be coated with C 3 N 4 FTO of (2) is positive and negative electrodes, and SiQDs are uniformly loaded on C by combining electrophoretic deposition with high-voltage pulse 3 N 4 And (3) upper part. The material prepared by the method has the advantages that the absorption and utilization of the visible light region are obviously improved, the separation efficiency of photo-generated electrons and holes is effectively increased, and the photocatalytic performance is obviously improved.

Description

Nonmetallic composite photocatalytic material and preparation and application thereof
Technical Field
The invention belongs to the technical field of environmental catalysis and nano materials, and particularly relates to silicon quantum dots (SiQDs) in-situ loaded carbon nitride (C) 3 N 4 ) The preparation and application of the novel nonmetallic composite photocatalytic material.
Background
Currently, photocatalytic materials decompose aqueous hydrogen and photo-reduce CO by illumination 2 The formation of C-H fuels, etc., which can convert solar energy directly into chemical energy, is considered one of the best ways of solar energy conversion and utilization in the future, as it is convenient, clean, and continuously producing renewable and "carbon neutral" fuels, attracting attention and being widely studied by countless scientists worldwide. Wherein C is 3 N 4 As a novel cheap, nontoxic and stable photocatalysis materialCan use the visible light with the wavelength less than 450nm and is widely paid attention to. But C is 3 N 4 The visible spectrum utilization range of (c) is to be further widened.
The photo-generated electron holes generated simultaneously are easily recombined, which leads to C 3 N 4 The light energy efficiency is low, and the wide application of the light energy is greatly limited in the field of environmental energy. Thus, for C 3 N 4 The effective modification is carried out, and the light energy utilization rate of the light source in the visible light region and the separation efficiency of photo-generated electron holes become the current research hot spots. At present to C 3 N 4 The modification method of (2) is mainly focused on the following three aspects: noble metal compounding, nonmetallic element doping and surface photosensitization, but noble metal compounding cost is higher, nonmetallic doped C 3 N 4 The problems of low absorption coefficient in the visible light region, unstable organic dye photosensitization, easy occurrence of photo-corrosion in narrow-band semiconductor photosensitization, etc. therefore, development of an effective modification means which is stable, low-cost and mass-producible is highly demanded to improve C 3 N 4 Photocatalytic efficiency.
Disclosure of Invention
The invention aims to provide a preparation method of a novel in-situ supported silicon quantum dot modified nonmetal composite photocatalytic material and application thereof in the field of photocatalysis, and the preparation method is stable, low in cost and capable of realizing mass production while improving the photocatalytic efficiency of the catalytic material.
A preparation method of a nonmetallic composite photocatalytic material comprises the following steps:
(1) Dispersing commercial silicon powder in an organic solvent, performing ultrasonic crushing, centrifuging after crushing, performing ultrasonic elution on the supernatant for a plurality of times, centrifuging after each ultrasonic elution except the last ultrasonic elution to obtain the supernatant, and centrifuging except the last ultrasonic elution to adopt gradient centrifugation; centrifuging to obtain a precipitate after the last ultrasonic elution, and freeze-drying the obtained precipitate to obtain silicon quantum dots SiQDs;
(2) C is C 3 N 4 Dispersing the powder into absolute ethyl alcohol by ultrasonic, preparing slurry, uniformly coating on fluorine doped tin oxide (FTO) glass, drying at room temperature,as an electrode;
(3) Dispersing SiQDs prepared in the step (1) into pure water solution purged by nitrogen to obtain SiQDs dispersion liquid, and placing a positive electrode and a negative electrode in the SiQDs dispersion liquid, wherein the positive electrode and the negative electrode are electrodes obtained in the step (2); firstly, applying a constant electric field to enable SiQDs to be enriched to an electrode through electrophoresis; then applying high pulse voltage to rivet SiQDs to C 3 N 4 Preparing a substrate to obtain SiQDs-loaded C 3 N 4 A composite material.
The preparation method mainly couples electrophoresis and pulse voltage, rivets the silicon quantum dots to the carbon nitride substrate, and forms the silicon quantum dot-loaded carbon nitride composite photocatalytic material. Coupling electrophoresis with pulse voltage to make C 3 N 4 Coating the silicon quantum dots SiQDs on the surface of an electrode, and enriching the silicon quantum dots SiQDs to C by utilizing low-voltage swimming 3 N 4 After which a pulsed high voltage is applied to rivet the silicon quantum dots SiQDs to C 3 N 4 A substrate. Silicon quantum dots SiQDs are obtained by continuous ultrasonic crushing gradient centrifugation and are combined with C 3 N 4 The silicon quantum dots are successfully and evenly loaded by a two-step method of piezophoresis deposition and high pulse voltage riveting, and the silicon quantum dots are arranged in C 3 N 4 The epitaxial growth on the substrate is effectively inhibited, the nano-scale crystal structure of the substrate is kept complete, the riveting strength of the composite material obtained by the process is considerable, and the obtained coating structure is compact and uniform.
In the invention, the silicon quantum dots SiQDs have narrower band gap, so that the silicon quantum dots SiQDs are connected with C 3 N 4 The spectrum utilization range of the loaded semiconductor material is expanded, and the light energy utilization of the material to the visible light region is improved. In the composite material obtained by the two-step method, the agglomeration of SiQDs can be effectively inhibited by adopting a mode of electrophoresis and pulse high-voltage coupling, so that the SiQDs are uniformly loaded on C 3 N 4 A surface; meanwhile, the method is rapid, convenient and low in energy consumption, and is a novel green material preparation technology. Compounded SiQDs with C 3 N 4 And a heterojunction structure can be formed between the two layers, so that the separation efficiency of photo-generated electron hole pairs is improved. The double pipes are aligned, so that the in-situ loaded SiQ prepared in the inventionDs C 3 N 4 The light energy utilization efficiency of the composite semiconductor material is obviously improved, and high-efficiency CO is realized 2 Photo-reduction to CO, CH 4 Etc. "carbon neutral" fuels.
The preparation method of the invention ensures that SiQDs are uniformly dispersed in C 3 N 4 On the substrate, a nanocomposite non-metallic photocatalytic material is formed. Compared with pure C 3 N 4 The material prepared by the method has the advantages that the absorption and utilization of the visible light region are obviously improved, the separation efficiency of photo-generated electron holes is effectively increased, and the photocatalytic performance is obviously improved. Meanwhile, the SiQDs raw material has low cost, can be produced in a large scale, and has wide application prospects in the fields of indoor pollutant photocatalytic degradation, water pollution photocatalytic degradation, organic light synthesis and the like. In addition, the loading method in the invention ensures that SiQDs are in C 3 N 4 The uniformity of surface distribution, the aggregation and epitaxial growth of quantum dots in the preparation process are avoided, and the integrity of the nano particles before and after the crystal structure loading is high, so that the catalytic performance of the obtained composite material is stable.
C 3 N 4 The microstructure is a lamellar layer, the structure is similar to nano graphene, and the specific surface area is large. Optionally, the C 3 N 4 The size of (2) is 20-80 nanometers; the particle size of the silicon quantum dot is 1-3 nanometers. Further preferably, the silicon quantum dot particle size is 2 nanometers. The C is 3 N 4 The dimensions of (C) can be understood as C 3 N 4 The particle size of the silicon quantum dot can be understood as its maximum particle size.
Optionally, in step (1): the organic solvent is ethanol, ethylenediamine or ethylene glycol; other organic solvents with similar properties can be substituted.
Optionally, in the step (1), considering ultrasonic efficiency, the proportion of the silicon powder to the organic solvent is 20-25 mg:35mL meter.
Optionally, in step (1): the temperature is controlled to be 15-20 ℃ in the ultrasonic crushing and ultrasonic washing processes; the time of ultrasonic crushing and single ultrasonic elution is 6-8 hours; the ultrasonic crushing and ultrasonic washing accumulation time is 36-48 hours.
And (3) controlling the temperature of liquid in the ultrasonic to be not too high in the ultrasonic crushing and ultrasonic elution processes, centrifuging at a low speed every 6-8 hours to remove sediment, keeping supernatant liquid, continuing ultrasonic treatment, repeating the processes until large-particle silicon powder is crushed completely, eluting the finally obtained supernatant liquid for a plurality of times, centrifuging at a high speed, keeping sediment, and freeze-drying the sediment to obtain SiQDs. The total time of ultrasonic crushing and washing is more than 36 hours and is controlled between 36 and 48 hours.
Optionally, the gradient centrifugation is: centrifuging for 5-8 min at 3000r/min after ultrasonic crushing; centrifuging for 5-8 min at 3450-3550 r/min after the first ultrasonic elution, and gradually increasing the centrifugal speed by 450-550 r/min after each ultrasonic elution except the last ultrasonic elution, wherein the centrifugal time is 5-8 min; centrifuging for 14-16 min at 12500-13500 r/min after the last ultrasonic elution.
Further, the gradient centrifugation is: centrifuging at 3000r/min for 5min after ultrasonic crushing; centrifuging at 3500r/min for 5min after the first ultrasonic elution, and sequentially increasing the centrifugal speed by 500r/min after each ultrasonic elution, wherein the centrifugal time is 5min; centrifuging at 13000r/min for 15min after the final ultrasonic elution is finished.
In the ultrasonic crushing and each ultrasonic washing process, the ultrasonic equipment is conventional ultrasonic equipment, and the power is more than 2000W.
The SiQDs manufacturing process requires special attention to low temperature ultrasound and step centrifugation: the temperature of the ultrasonic process is controlled between 15 and 20 ℃, so that the influence of the agglomeration of the silicon quantum dots on the dispersibility and the catalytic performance caused by the excessive temperature is prevented; after each ultrasonic treatment for 6-8 hours, standing to observe whether the brown color of the supernatant is stable, centrifuging the sample in a centrifuge for 5min after no obvious change, separating the supernatant from the precipitate, transferring the separated supernatant into a new container, continuing ultrasonic timing observation, wherein the rotating speed is 3000r/min after the ultrasonic treatment is finished for the first time, and then sequentially increasing the rotating speed by 500r/min when centrifuging after the ultrasonic treatment is finished for each time.
The low-speed centrifugal rotating speed is controlled to be 3000-6000 r/min in the whole SiQDs preparation process, so that the influence of the excessive rotating speed on the obtaining rate caused by mixing of silicon powder scraps generated after crushing into sediment is prevented, and the centrifugal time is 5-8 min; the total time length of ultrasonic crushing and ultrasonic elution is more than 36 hours and is controlled between 36 and 48 hours; after timing is finished, the obtained solution is respectively washed for 3 times by using ethanol and deionized water to remove impurities, and then centrifuged for 15 minutes at the speed of 13000r/min, the supernatant is removed, and the sediment is reserved; and finally, freeze-drying for 12-15 hours in a freeze dryer, and grinding to obtain SiQDs samples.
The synthesis of the nano composite nonmetallic photocatalytic material is obtained by a two-step method of electrophoresis-high pulse voltage deposition and then cold drying. Enrichment of SiQDs to C by electrophoresis with low electric field 3 N 4 An electrode surface; riveting SiQDs to C using high pulse voltages 3 N 4 On the substrate, preparing SiQDs-loaded C 3 N 4 A composite material.
Optionally, in step (2): the preparation concentration of the slurry is 10-40 mg/mL. Further, the concentration of the slurry is 10-15 mg/mL.
Optionally, in step (3): the dispersion ratio of SiQDs in pure water is 10-20 mg:20mL.
Optionally, in step (3): the electric field intensity of electrophoresis is 3-5V/cm, the temperature is kept at 25-40 ℃, and the action time is 20-40 min.
Optionally, in step (3): when the high pulse voltage acts, the high pulse voltage is set to be 60-80V/cm; the total acting time is maintained for 20-40 s.
Most preferably, in step (2): the preparation concentration of the slurry is 10mg/mL; in the step (3): the dispersion ratio of the SiQDs in pure water is 20mg:20mL; the electric field intensity of electrophoresis is 3V/cm, the temperature is kept at 25 ℃, and the action time is 30min; setting the high-voltage pulse voltage to be 60V/cm when the high-voltage pulse voltage acts; the total duration of action was maintained for 30s.
Optionally, also includes a C to be loaded with SiQDs 3 N 4 And a step of peeling the composite material from the FTO peel. The stripped composite material is dispersed in deionized water by ultrasonic, and then freeze-dried.
The invention also provides a nonmetal photocatalytic material prepared by the preparation method, which is used in the field of photocatalysis and can be used for CO 2 And (3) photocatalytic reduction.
Drawings
FIG. 1 is a schematic diagram of SiQDs-C formed by loading SiQDs prepared in example 1 and an electrophoresis-high pulse voltage coupling technique 3 N 4 Transmission Electron Microscope (TEM) photograph of (a) SiQDs (b) SiQDs-C 3 N 4 )。
FIG. 2 is pure C 3 N 4 And SiQDs-C prepared in example 1 3 N 4 Is an X-ray powder diffraction pattern of (c).
FIG. 3 is pure C 3 N 4 And SiQDs-C prepared in example 1 3 N 4 Is a UV-visible absorption spectrum of (C).
FIG. 4 is a SiQDs-C prepared in example 1 3 N 4 X-ray photoelectron spectroscopy of (c).
FIG. 5 is pure C 3 N 4 And SiQDs-C prepared in example 1 3 N 4 CO of (c) 2 And a photo-catalytic reduction experimental result diagram.
Detailed Description
The technical solutions of the present invention will be clearly and completely described in connection with the embodiments, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
SiQDs-C provided by the invention 3 N 4 SiQDs obtained by ultrasonic crushing gradient centrifugation of the nano material are uniformly distributed in C through electrophoretic deposition-high pulse voltage riveting 3 N 4 On the surface, a nonmetallic composite photocatalytic material is formed. In the invention, the nano material is an organic semiconductor composite structure of in-situ loaded surface photosensitizer, and is prepared bySiQDs are uniformly distributed in C 3 N 4 On the surface, the absorption and utilization of the material to the visible light area are obviously improved, the separation efficiency of photo-generated electron holes is effectively increased, and the photocatalytic performance is obviously improved; the loading method controls the SiQDs not to epitaxially grow and keep higher integrity through the action of an electric field, and simultaneously ensures that the purity and the strength of the SiQDs are obviously improved.
SiQDs-C 3 N 4 The preparation of the nanomaterial comprises the following steps:
first, silicon quantum dots were prepared: adding a certain amount of commercial silicon powder into the mixture, and sufficiently crushing the mixture by low-temperature ultrasonic; standing after ultrasonic treatment for a period of time to observe whether the supernatant is brown or not, separating the supernatant from the large-particle silicon powder by low-speed centrifugation, repeatedly carrying out ultrasonic crushing on the supernatant, and separating and retaining the supernatant at fixed time until the original silicon powder is completely crushed; centrifuging the supernatant at high speed, cleaning to remove impurities, and freeze drying for a period of time;
then, C is firstly carried out 3 N 4 Dispersing the powder into absolute ethanol solution by ultrasonic, preparing slurry, uniformly coating the slurry on fluorine-doped tin oxide (FTO) glass, and drying at room temperature to fix the powder as a required electrode; dispersing the SiQDs into pure water solution purged by nitrogen, wherein the electrodes of the anode and the cathode are coated with C 3 N 4 FTO glass of (c). Applying a constant electric field with a certain intensity to enable SiQDs to be deposited on the electrode through electrophoresis enrichment, and then applying a high pulse voltage to enable the SiQDs to be riveted to C 3 N 4 Preparing a substrate to obtain SiQDs-loaded C 3 N 4 A composite material.
The silicon quantum dots dispersed in the electrolyte are enriched in the electrolyte containing C by utilizing the electrophoresis 3 N 4 Performing preliminary enrichment deposition on the working electrode of (2), and then combining the silicon quantum dots with C under the action of high pulse voltage 3 N 4 And tightly riveting to finish loading, removing the formed coating, scraping the coating into deionized water, performing ultrasonic dispersion, and freeze-drying to obtain the composite photocatalytic material.
Pure C 3 N 4 The method comprises calcining at a certain temperature for one periodThe precursor powder is rearranged in lattice, fully mixed with water and centrifuged, and the particles are crushed and fine to prepare the pure nano C 3 N 4 And (3) particles. In particular, as an example, with respect to pure nano-C 3 N 4 The calcination process of (2) may be: heating from room temperature to 550 ℃ in a high-temperature furnace at a heating rate of 5 ℃/min, maintaining at 550 ℃ for 2 hours, and naturally cooling to room temperature. Cooling, centrifuging and drying after the reaction is finished to obtain pure nano C 3 N 4 And (3) powder. Wherein the precursor is one of melamine, cyanamide and urea.
Of course, C 3 N 4 The powder may also be prepared by other known methods.
The following is a description of specific examples:
example 1
(1) 6 portions of 25mg commercial silicon powder were weighed into 6 50mL capped centrifuge tubes, and 35mL absolute ethanol was added to each tube.
(2) And (3) placing the centrifuge tube filled with the materials and the ethanol into ultrasonic waves for breaking, wherein the water level of the centrifuge tube is beyond the scale mark of the solution in the centrifuge tube, so that the sufficiency of ultrasonic waves is ensured.
(3) In order to ensure and maintain the low-temperature environment contacted by the centrifuge tube, an ice bag is placed in the ultrasonic box, meanwhile, the temperature change is monitored, and the ice bag is replaced in time to enable the temperature to be about 20 ℃.
(4) And (3) collecting and processing the ultrasonic sample with a period of 8 hours, centrifuging for 5 minutes at 3000r/min, and then placing the obtained supernatant into a clean centrifuge tube to repeat the steps (2) and (3), wherein the centrifugal speed is increased by 500r/min on the basis of the last time each time (namely, the centrifugal speed is sequentially 3000r/min, 3500r/min, 4000r/min, 4500r/min and 5000 r/min), and the total ultrasonic time is 48 hours (namely, 6 times of total ultrasonic time).
(5) After the last ultrasonic treatment is finished, centrifuging the material for 15min at 13000r/min, carefully removing the supernatant to reserve the precipitate, wherein the precipitate is the silicon quantum dot.
(6) Adding 20mL of absolute ethyl alcohol into the centrifuge tube filled with the silicon quantum dots in the step (5), sufficiently oscillating the material and the ethyl alcohol for 2min, centrifuging to remove the ethyl alcohol, and repeatedly cleaning for 3 times; then deionized water is added for cleaning, and the operation process is the same as that of ethanol.
(7) And freeze-drying the obtained precipitate for 12 hours to obtain the silicon quantum dots SiQDs of the sample.
(8) 200mg C is weighed 3 N 4 The powder is dispersed into 20mL absolute ethanol solution by ultrasonic to prepare uniform slurry, then is sucked by a dropper and uniformly coated on 1cm x 5cm FTO stripping, and is dried at room temperature to fix the powder, and then is used as a working electrode for standby.
(9) Weighing 10mg of SiQDs obtained by preparation, dispersing in 20mL of pure water solution purged by nitrogen, wherein the electrodes of the anode and the cathode are all coated C obtained in (8) 3 N 4 FTO glass of (c).
(10) In the electrophoresis of the preliminary deposition plating process, the electric field intensity is selected to be 3V/cm, the temperature is maintained at 25 ℃, and the action time is 30min.
(11) Applying a high pulse voltage to rivet SiQDs to C 3 N 4 The high voltage pulse voltage was 60V/cm on the substrate, and the total time of the pulses was 30 seconds.
(12) Removing the FTO electrode after riveting in the step (11), scraping a coating formed on the surface into deionized water, performing ultrasonic dispersion, and freeze-drying for 10 hours to obtain SiQDs-C 3 N 4 。
Photocatalytic reduction of CO Using the catalyst prepared in this example 2 The experimental steps of (a) are as follows:
(1) Sample C was taken 3 N 4 0.5g is placed in a photocatalysis reactor, 2-4 mL of distilled water is added, and the mixture is dried at 60 ℃ until the catalyst can be paved at the bottom of the reactor.
(2) By CO 2 Purging the reactor by gas for 20min to exhaust the impurity gas in the reactor, and ensuring pure CO 2 An environment.
(3) CO is processed by 2 Introducing into a water washing bottle for water washing, and then introducing CO carrying water vapor 2 A gas is introduced into the reactor.
(4) The reactor was illuminated using a 25A/h current density 350W xenon lamp as the light source.
(5) The illumination period is 5h, the reactor is aerated every 1h, and the gas components are detected by gas chromatography.
(6) Sampling SiQDs-C 3 N 4 And (5) repeating the steps (1) - (5) by 0.5 g. The two sets of samples were compared for performance differences.
FIG. 1 shows the SiQDs-C with successful loading by coupling SiQDs and electrophoresis-high pulse voltage prepared in example 1 3 N 4 A Transmission Electron Microscope (TEM) photograph of (a); it can be seen that SiQDs particles prepared after ultrasonic crushing are uniform and still uniformly distributed in C of layered two-dimensional structure after in-situ loading 3 N 4 SiQDs do not have particle growth and agglomeration phenomena on the substrate. FIG. 2 is pure C 3 N 4 And SiQDs-C prepared in example 1 3 N 4 X-ray powder diffraction pattern of (2); since SiQDs are loaded at C 3 N 4 Surface, siQDs modified C 3 N 4 Due to the low SiQDs content and high dispersion, no diffraction peak changes could be seen, indicating that the introduction of silicon quantum dots does not alter C 3 N 4 Is a chemical structure of (a). FIG. 3 is pure C 3 N 4 And SiQDs-C prepared in example 1 3 N 4 An ultraviolet visible absorption spectrum of (a); siQDs-C 3 N 4 Absorption in the visible region is significantly enhanced, as well as a broader visible absorption range. FIG. 4 is a SiQDs-C prepared in example 1 3 N 4 In the total spectrum, signal peaks appear in the carbon element, the nitrogen element and the silicon element, and the signal of the silicon is weaker because of lower load concentration; FIG. 5 pure C 3 N 4 And SiQDs-C prepared in example 1 3 N 4 CO of (c) 2 A photocatalytic reduction experimental diagram; siQDs-C in the illumination process under the same condition 3 N 4 The sample is capable of converting CO 2 More efficient catalytic reduction to carbon monoxide than pure C 3 N 4 The catalytic effect of the catalyst is better.
Example 2
SiQDs were prepared as in example 1;
SiQDs and C 3 N 4 The dispersion ratio of the silicon quantum dots in pure water was 20mg:20mL; selecting electrophoresis deposition with electric field strength of 3V/cm, temperature of 40deg.C, and high pulse voltage riveting after 40min of common action timeThe high-voltage pulse voltage was 80V/cm, and the total time was 30s. After the completion, the working electrode is taken down, the surface material is scraped into deionized water for ultrasonic treatment and centrifugal drying is carried out for 10 hours, and SiQDs-C is obtained 3 N 4 And (3) nanoparticles.
It should also be understood that the above embodiments are only for further illustrating the present invention, and should not be construed as limiting the scope of the present invention, and that some insubstantial modifications and adjustments made by those skilled in the art in light of the above disclosure are within the scope of the present invention. The specific process parameters and the like described below are also merely examples of suitable ranges, i.e., one skilled in the art can make a suitable selection from the description herein and are not intended to be limited to the specific values described below.

Claims (10)

1. The preparation method of the nonmetallic composite photocatalytic material is characterized by comprising the following steps:
(1) Dispersing commercial silicon powder in an organic solvent, performing ultrasonic crushing, centrifuging after crushing, performing ultrasonic elution on the supernatant for a plurality of times, centrifuging after each ultrasonic elution except the last ultrasonic elution to obtain the supernatant, and centrifuging except the last ultrasonic elution to adopt gradient centrifugation; centrifuging to obtain a precipitate after the last ultrasonic elution, and freeze-drying the obtained precipitate to obtain silicon quantum dots SiQDs;
(2) C is C 3 N 4 Dispersing the powder into absolute ethyl alcohol by ultrasonic, preparing slurry, uniformly coating the slurry on FTO glass, and drying at room temperature to serve as an electrode;
(3) Dispersing the SiQDs of the silicon quantum dots prepared in the step (1) into pure water purged by nitrogen to obtain SiQDs dispersion liquid, and placing a positive electrode and a negative electrode in the SiQDs dispersion liquid, wherein the positive electrode and the negative electrode are the electrodes obtained in the step (2); firstly, applying a constant electric field to enable SiQDs to be enriched to an electrode through electrophoresis; then applying high pulse voltage to rivet SiQDs to C 3 N 4 Preparing a substrate to obtain SiQDs-loaded C 3 N 4 A composite material.
2. The method according to claim 1, wherein in step (1): the organic solvent is ethanol, ethylenediamine or ethylene glycol; the proportion of the commercial silicon powder to the organic solvent is 20-25 mg:35mL.
3. The method according to claim 1, wherein in step (1): the temperature is controlled to be 15-20 ℃ in the ultrasonic crushing and ultrasonic washing processes; the time of ultrasonic crushing and single ultrasonic elution is 6-8 hours; the ultrasonic crushing and ultrasonic washing accumulation time is 36-48 hours.
4. The method of claim 1, wherein the gradient centrifugation is: centrifuging for 5-8 min at 3000r/min after ultrasonic crushing; centrifuging for 5-8 min at 3450-3550 r/min after the first ultrasonic elution, and gradually increasing the centrifugal speed by 450-550 r/min after each ultrasonic elution except the last ultrasonic elution, wherein the centrifugal time is 5-8 min; and centrifuging for 14-16 min at 12500-13500 r/min after the last ultrasonic elution.
5. The method according to claim 1, wherein in step (2): the preparation concentration of the slurry is 10-40 mg/mL.
6. The method according to claim 1, wherein in the step (3): the dispersion ratio of the SiQDs silicon quantum dots in pure water is 10-20 mg:20mL.
7. The method according to claim 1, wherein in the step (3): the electric field intensity of electrophoresis is 3-5V/cm, the temperature is kept at 25-40 ℃, and the electrophoresis time is 20-40 min.
8. The method according to claim 1, wherein in the step (3): the high pulse voltage is 60-80V/cm, and the total time of the pulse is 20-40 s.
9. A nonmetallic composite photocatalytic material prepared by the preparation method according to any one of claims 1 to 8.
10. Use of the non-metallic composite photocatalytic material according to claim 9 in the field of photocatalysis.
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CN110465318A (en) * 2019-07-12 2019-11-19 广东工业大学 Hollow nitride porous carbon ball composite photo-catalyst of a kind of carbon quantum dot load and its preparation method and application

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