Preparation method of composite photocatalyst graphene oxide / biVO4

Abstract

The application belongs to the field of photocatalytic material preparation, and aims at solving the problem of low photocatalytic efficiency. The preparation method comprises the following steps: firstly, pre-oxidized graphene is put into distilled water and uniformly dispersed by ultrasonic, so as to obtain an oxidized graphene suspension; bismuth nitrate and ammonium metavanadate are respectively dissolved in nitric acid and ammonia water to obtain two solutions A and B; under ultrasonic state, A and B are added into the oxidized graphene suspension and uniformly dispersed, and then a precursor solution is obtained after magnetic stirring; secondly, the precursor solution is loaded into a reaction kettle with a polytetrafluoroethylene lining, and the reaction kettle is kept at 110 DEG C for 24 hours; the reaction liquid is obtained after the temperature is reduced to 60 DEG C; thirdly, the precipitated solid phase material in the lower layer of the reaction liquid is collected, washed, dried and ground into powder, so as to obtain graphene oxide / BiVO4 composite photocatalytic nanoparticles. The preparation method is simple, and the graphene oxide / BiVO4 composite photocatalytic nanoparticles obtained by the method effectively improve the photocatalytic oxidation performance.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation and relates to a method for preparing graphene oxide / BiVO4 composite photocatalytic particles. Background Technology

[0002] BiVO4 is a high-performance visible-light photocatalyst with excellent activity in the photocatalytic decomposition and degradation of organic pollutants. It has three crystal structures: tetragonal zircon, monoclinic scheelite, and tetragonal scheelite. The monoclinic phase exhibits the highest visible-light activity. Rapid recombination of photogenerated charge carriers during photocatalytic reactions is the main reason for inhibited photocatalytic efficiency. In photocatalysis, charge carriers must first be captured to suppress recombination and promote charge transfer at the interface. Two key factors typically determine quantum yield and charge transfer at the interface: the competition between charge carrier recombination and capture; and the competition between captured charge carrier recombination and interfacial charge migration. However, the electron-hole migration rate is much lower than the recombination rate, resulting in a low quantum yield for the catalyst. The recombination and migration mechanisms between photoexcited electron-hole pairs jointly determine the total quantum yield of interfacial charge transfer. Because BiVO4 has a conduction band potential of 0-V and a band gap of 2.45V, photogenerated charge carriers recombine easily, and its adsorption performance of reactants is poor. In recent years, researchers both domestically and internationally have employed numerous methods to improve the photocatalytic performance of BiVO4. The main methods fall into two categories: 1) Noble metal deposition on the BiVO4 surface is considered an effective modification method for trapping electrons. Noble metals such as Pt, Pd, and Ag, deposited on the semiconductor surface, can form a Schottky barrier with the semiconductor, trapping photogenerated electrons and reducing electron-hole pair recombination, thereby improving the photocatalytic performance of the semiconductor material. 2) Semiconductor recombination can form trapping traps for excited electrons in the photocatalyst, also extending the electron-hole pair lifetime. Currently, numerous publications have reported on Co… ； While various 5566 semiconductors, such as O4-BiVO4, TiO2-BiVO4, and Bi2O3-BiVO4, can partially improve the performance of photocatalysts, they still present many challenges. These include complex noble metal deposition processes and stringent preparation conditions; and the potential for electron traps in composite semiconductors to become recombination centers for electron-hole pairs. Therefore, promoting electron transport and reducing carrier recombination have become the research goals of many scholars.

[0003] Graphite oxide (GO) is a layered compound obtained by oxidizing natural graphite with a strong oxidizing agent. Its interlayer spacing is much larger than that of graphite, and its overall structure is very stable. No carbon atom loss has ever been observed in previous experimental data. Therefore, using graphite oxide as a modifier, and leveraging GO's high conductivity, high carrier mobility, and extremely large specific surface area, a novel graphene-based photocatalyst can be prepared to improve the quantum efficiency of the photocatalyst and thus enhance the pollutant removal effect. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of low photocatalytic efficiency of bismuth vanadate, and to provide a method for preparing graphene oxide / BiVO4 composite photocatalytic particles.

[0005] The preparation method of the graphene oxide / BiVO4 composite photocatalytic particles of the present invention is carried out according to the following steps:

[0006] I. Preparation of precursor solution: Pre-oxidized graphene was placed in distilled water and ultrasonically dispersed evenly to obtain an oxidized graphene suspension. Two solutions, A and B, were obtained by dissolving bismuth nitrate and ammonium metavanadate in nitric acid and ammonia water, respectively. A and B were added to the oxidized graphene suspension under ultrasonic conditions and dispersed evenly. The pH was adjusted to 7 with NaOH and HNO3 solution and then magnetically stirred to obtain the precursor solution.

[0007] II. Hydrothermal preparation of composite particles: The precursor solution was loaded into a reaction vessel with a polytetrafluoroethylene liner, kept at 110℃ for 24 hours, and then the vessel was opened after cooling to 60℃ to obtain the reaction solution.

[0008] 3. Washing and grinding: Collect the precipitated solid phase at the bottom of the reaction liquid. Wash the solid phase multiple times with distilled water by centrifugation, dry it and grind it into powder to obtain graphene oxide / BiVO4 composite photocatalytic particles.

[0009] In step one, the mass ratio of bismuth vanadate synthesized from graphene oxide and solutions A and B is 1:1.

[0010] This invention proposes a simple method for preparing graphene oxide / BiVO4 composite particles. Using graphene oxide particles as the core, monoclinic BiVO4 is grown on its surface. The photocatalytic oxidation performance is significantly improved compared to pure BiVO4 particles, and the photoresponse range is broadened.

[0011] The preparation method of the graphene oxide / BiVO4 composite photocatalytic particles of the present invention has the following beneficial effects:

[0012] 1. The preparation method is simple and does not require subsequent calcination treatment, which ensures the stability of the BiVO4 crystal form.

[0013] 2. The growth process is controllable. The growth of BiVO4 on the surface of graphene oxide particles can be controlled by adjusting the ratio of graphene oxide to BiVO4, as well as the reaction time, temperature, and pH.

[0014] 3. The composite of graphene oxide / BiVO4 photocatalytic particles effectively improves the photocatalytic oxidation performance. Attached Figure Description

[0015] Figure 1The XRD pattern of the graphene oxide / BiVO4 composite photocatalytic particles obtained in the examples is shown below.

[0016] Figure 2 The image shows the full XPS spectrum of the graphene oxide / BiVO4 composite photocatalytic particles obtained in the examples.

[0017] Figure 3 The image shows the V 2p XPS spectra of the graphene oxide / BiVO4 composite photocatalytic particles obtained in the examples.

[0018] Figure 4 The image shows the C1s XPS spectrum of the graphene oxide / BiVO4 composite photocatalytic particles obtained in the examples.

[0019] Figure 5 This is a SEM image of the graphene oxide composite photocatalytic particles obtained in the examples;

[0020] Figure 6 Here is a SEM image of the graphene oxide / BiVO4 composite photocatalytic particles obtained in the examples;

[0021] Figure 7 The graphs show the graphene oxide / BiVO4 composite photocatalytic particles obtained in the examples, as well as the methylene blue degradation rate test results of different proportions and pure BiVO4. Detailed Implementation Specific implementation method one:

[0023] The preparation method of the graphene oxide / BiVO4 composite photocatalytic particles in this embodiment is carried out according to the following steps:

[0024] I. Preparation of the precursor solution. Pre-oxidized graphene was placed in distilled water and ultrasonically dispersed to obtain a graphene oxide suspension. Two solutions, A and B, were obtained by dissolving bismuth nitrate and ammonium metavanadate in nitric acid and ammonia, respectively. A and B were added to the graphene oxide suspension under ultrasonic conditions and dispersed evenly. The pH was adjusted to 7 with NaOH and HNO3 solutions, and the mixture was magnetically stirred to obtain the precursor solution.

[0025] II. Hydrothermal preparation of composite particles. The precursor solution was loaded into a reaction vessel with a polytetrafluoroethylene liner, kept at 110℃ for 24 hours, and then cooled to 60℃ before being opened to obtain the reaction solution;

[0026] 3. Washing and grinding. Collect the precipitated solid phase from the bottom of the reaction solution. Wash the solid phase multiple times with distilled water by centrifugation, dry it, and grind it into powder to obtain graphene oxide / BiVO4 composite photocatalytic particles;

[0027] In step one, the mass ratio of bismuth vanadate synthesized from graphene oxide and solutions A and B is 1:1. Specific Implementation Method Two:

[0029] The difference between this embodiment and specific embodiment one is that the average particle size of the graphene oxide powder in step one is 3 to 5 micrometers. Specific implementation method three:

[0031] The difference between this embodiment and specific embodiment one or two is that the magnetic stirring time in step one is 40 to 50 minutes. Specific implementation method four:

[0033] The difference between this embodiment and one of the specific embodiments one to three is that the solid phase in step three is washed with distilled water by filtration 3 to 5 times. Specific implementation method five:

[0035] The difference between this embodiment and one of the specific embodiments one to four is that the drying temperature in step three is room temperature (25°C). Specific implementation method six:

[0037] The difference between this embodiment and one of the specific embodiments one to five is that the particle size of the graphene oxide / BiVO4 composite photocatalytic particles obtained in step three is 3 to 5 micrometers.

[0038] Example:

[0039] The preparation method of the graphene oxide / BiVO4 composite photocatalytic particles in this embodiment is carried out according to the following steps:

[0040] I. Preparation of precursor solution: Pre-oxidized graphene (average particle size of 4 micrometers) was added to distilled water and ultrasonically dispersed evenly to obtain an oxidized graphene suspension. Bismuth nitrate and solution A dissolved in nitric acid were added to the oxidized graphene suspension and ultrasonicated for 10 min. Then, solution B of ammonium metavanadate dissolved in ammonia was slowly added and dispersed evenly. The pH was adjusted to 7 with NaOH and HNO3 solution and magnetically stirred for 40-50 min to obtain the precursor solution.

[0041] II. Hydrothermal preparation of composite particles: The precursor solution is loaded into a reaction vessel with a polytetrafluoroethylene liner. The volume of the precursor solution in the reaction vessel is three-quarters of the total volume. After loading, the reaction is carried out at 110°C for 24 hours. The temperature is then programmed to drop to 60°C. After cooling, the reaction vessel is opened to obtain the reaction solution.

[0042] 3. Washing and grinding: Collect the precipitated solid phase at the bottom of the reaction liquid, wash the solid phase 5 times with distilled water, dry it at room temperature (25℃), and grind it into powder to obtain graphene oxide / bismuth vanadate composite photocatalytic particles.

[0043] In step one, the mass ratio of graphene oxide to bismuth vanadate synthesized from solutions A and B is 1:1.

[0044] In this embodiment, X-ray diffraction (XRD) was used to determine the crystal form of the graphene oxide / BiVO4 composite particles; X-ray photoelectron spectroscopy (XPS) was used to characterize the elemental valence states (C, V) of the composite particles.

[0045] from Figure 1 The XRD pattern shows obvious diffraction peaks around 18.3°, 24.3°, 30.50°, 32.6°, 34.5°, 35.0°, 39.8°, 42.4°, 45.9°, 47.2°, 48.3°, and 53.1°, corresponding to the monoclinic scheelite-type BiVO4 crystal planes (standard card JCPDS 14-0688) (110), (011), (121), (040), (200), (002), (211), (150), (060), (240), (222), (161), (321), and (123). This indicates that monoclinic scheelite-type BiVO4 was successfully prepared.

[0046] from Figures 2-4 XPS analysis clearly shows that elements C, Bi, and O can be observed significantly at their respective standard binding energies, as indicated by the full-scan XPS spectrum. The characteristic peak of V2p is 517.1 eV; the Cls characteristic peak in GO / BiVO4 has one peak, and the peak near 284.8 eV is attributed to the CC vibration, mainly originating from the added GO. This result indicates the presence of elements C, Bi, and O in the GO / BiVO4 composite photocatalyst. 2 Hybridized CV current-carrying conductor.

[0047] Figures 5-6 The SEM images show that graphene oxide and BiVO4 are tightly bonded together, and a composite catalyst has been successfully prepared.

[0048] Methylene blue was used as the target degradation product, with an initial concentration of 50 mg / L. The degradation rate of methylene blue under visible light irradiation for 4 hours was measured (the concentration of photocatalyst was 1 g / L). The photocatalytic oxidation ability of the composite particles was characterized by comparing pure bismuth vanadate with particle photocatalysts with different graphene oxide doping amounts. Figure 7 The methylene blue degradation rate test chart shows that, compared with pure bismuth vanadate (BiVO4) particles, the 1:1 composite photocatalytic particles prepared in this embodiment have improved photocatalytic oxidation performance, and the methylene blue degradation rate has increased from 62% to 75%.

Claims

1. A method for preparing a composite photocatalyst graphene oxide / BiVO4, characterized in that... This method is implemented in the following steps: I. Preparation of precursor solution: Pre-oxidized graphene was placed in distilled water and ultrasonically dispersed evenly to obtain graphene oxide suspension. Bismuth nitrate and ammonium metavanadate were dissolved in nitric acid and ammonia water respectively to obtain two solutions, A and B. A and B were added to the graphene oxide suspension under ultrasonic conditions and dispersed evenly. The pH was adjusted to 7 with NaOH and HNO3 solution and magnetically stirred to obtain the precursor solution. II. Hydrothermal preparation of composite particles: The precursor solution was loaded into a reaction vessel with a polytetrafluoroethylene liner, kept at 110℃ for 24 hours, and then the vessel was opened after cooling to 60℃ to obtain the reaction solution.

3. Washing and grinding: Collect the precipitated solid phase at the bottom of the reaction liquid. Wash the solid phase multiple times with distilled water by centrifugation, dry it and grind it into powder to obtain graphene oxide / BiVO4 composite photocatalytic particles. In step one, the mass ratio of the pre-oxidized graphene to the bismuth vanadate synthesized from solutions A and B is 1:

1. The average particle size of the graphene oxide powder in step one is 20–50 nanometers.

2. The method for preparing graphene oxide / BiVO4 composite photocatalytic particles according to claim 1, characterized in that... The magnetic stirring time in step one is 40-50 minutes.

3. The method for preparing graphene oxide BiVO4 composite photocatalytic particles according to claim 1, characterized in that... Step 3: Wash the solid phase with deionized water by centrifugation 3 to 5 times.

4. The method for preparing graphene oxide / BiVO4 composite photocatalytic particles according to claim 1, characterized in that... The drying temperature in step three is 25℃.

5. The method for preparing graphene oxide / BiVO4 composite photocatalytic particles according to claim 1, characterized in that... The particle size of the graphene oxide / BiVO4 composite photocatalytic particles obtained in step three is 6–10 μm.

Images