Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure and preparation method thereof

Abstract

The present invention belongs to the technical field of photocatalysts, and discloses a Bi7O9I3 / graphite paper flexible composite photocatalyst with a hierarchical structure and a preparation method thereof. The preparation method of the composite photocatalyst of the present invention comprises: S1, adding Bi(NO3)3 and KI to a mixed solvent of ethylene glycol and water to prepare a Bi(NO3)3 and KI mixed solution; S2, the graphite paper is immersed in the ethylene glycol solution of Bi(NO3)3, then rinsed with ethylene glycol, and then immersed in the mixed solution of Bi(NO3)3 and KI obtained in step S1 until red deposits appear on the graphite paper, and after rinsing and drying, a BiOI / graphite paper composite precursor is obtained; S3, the prepared BiOI / graphite paper composite precursor is burned on a flame to turn the red deposits into yellow, and the BiOI in the precursor is in situ converted into oxygen-rich Bi7O9I3 to form a Bi7O9I3 / graphite paper flexible composite. The substrate of the Bi7O9I3 / graphite paper flexible composite photocatalyst of the present invention is flexible graphite paper, and Bi7O9I3 is formed by in-situ oxidation of BiOI in a precursor, which can effectively separate the photogenerated carriers of Bi7O9I3 in the composite.

Description

Technical Field

[0001] The invention relates to the technical field of photocatalysts, and in particular to a Bi7O9I3 / graphite paper flexible composite photocatalyst with a hierarchical structure and a preparation method thereof. Background Art

[0002] Photocatalytic technology has a good application prospect in sewage treatment, and the use of visible light for photocatalytic pollutant removal has more advantages in practical applications. On the one hand, visible light accounts for the largest proportion of solar energy; on the other hand, visible light is safer for the human body and can be used with indoor light sources.

[0003] Among visible light photocatalysts, BiOI is a common visible light photocatalyst with a narrow band gap, easy preparation, safety, and low cost, which makes it have good application prospects. However, the narrow band gap also makes BiOI's oxidation and reduction ability weak, which is not conducive to its use in the photocatalytic oxidation of some difficult-to-decompose pollutants. Increasing the band gap of BiOI can enhance its oxidation and reduction ability, but it also makes its excitation difficult. Properly increasing the band gap width can increase the redox ability with less sacrifice of light absorption, which is conducive to the oxidation and decomposition of difficult-to-decompose pollutants. Therefore, Bi7O9I3 with a relatively high ratio of Bi and O often performs better than BiOI. However, when Bi7O9I3 is used alone, the performance is not ideal because photogenerated electrons and holes are easy to recombine. At the same time, Bi7O9I3 powder is not easy to recycle when used, which is also very unfavorable for its large-scale application.

[0004] Although surface modification using carbon nanomaterials such as graphene, graphene oxide, and carbon nanotubes can effectively separate photogenerated electrons and holes, these materials are all nanoscale and cannot be used as macroscale substrate materials. The prepared composite materials are still powders and cannot solve the problem of recycling. Therefore, the problem of charge separation and recycling can only be solved by combining macroscale carbon materials with Bi7O9I3. Among them, graphite paper is a suitable substrate material. However, Bi7O9I3 can be prepared by a variety of methods, but due to the non-polarity of graphite, it is very difficult to deposit Bi7O9I3 in situ on the surface of graphite paper. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned background technology and provide a Bi7O9I3 / graphite paper flexible composite photocatalyst with a hierarchical structure and a preparation method thereof. The Bi7O9I3 / graphite paper flexible composite photocatalyst with a hierarchical structure described in the present invention is prepared in situ by flame burning, and its substrate is flexible graphite paper. Bi7O9I3 is formed by in-situ oxidation of BiOI in the precursor and has a hierarchical structure similar to the original BiOI, ensuring that the graphite paper maintains its original flexibility and graphite structure, and can effectively separate the photogenerated carriers of Bi7O9I3 in the composite.

[0006] To achieve the purpose of the present invention, the preparation method of the hierarchical Bi7O9I3 / graphite paper flexible composite photocatalyst comprises the following steps:

[0007] S1, adding Bi(NO3)3 and KI into a mixed solvent of ethylene glycol and water to prepare a mixed solution of Bi(NO3)3 and KI;

[0008] S2, the graphite paper is immersed in an ethylene glycol solution of Bi(NO3)3, and then rinsed with ethylene glycol to remove the Bi(NO3)3 solution adhering to the surface of the graphite paper, and immersed in a mixed solution of Bi(NO3)3 and KI obtained in step S1 until a red precipitate appears on the graphite paper, and after rinsing and drying, a BiOI / graphite paper composite precursor is obtained;

[0009] Among them, the purpose of impregnation with Bi(NO3)3 ethylene glycol solution is to form Bi on the surface of graphite paper. 3+ The adsorption of is beneficial to in-situ deposition and shortening the deposition time. Without surface treatment, although the sample can be prepared, the deposition time will be relatively long, possibly exceeding 8h.

[0010] S3, burning the prepared BiOI / graphite paper composite precursor on a flame, so that the red deposit on the precursor turns yellow, and the BiOI in the precursor is in situ converted into oxygen-rich Bi7O9I3, forming a Bi7O9I3 / graphite paper flexible composite.

[0011] Furthermore, in some embodiments of the present invention, the volume ratio of ethylene glycol to water in step S1 is 1:1 to 6:1.

[0012] Furthermore, in some embodiments of the present invention, the concentration of Bi(NO3)3 in the mixed solution of step S1 is 10-20 g / L; preferably, the molar ratio of Bi(NO3)3 to KI is 0.5:1 to 2.0:1.

[0013] Furthermore, in some embodiments of the present invention, the concentration of the Bi(NO3)3 ethylene glycol solution in step S2 is 0.7 to 1.3 g / L.

[0014] Furthermore, in some embodiments of the present invention, in step S2, the graphite paper is immersed in the ethylene glycol solution of Bi(NO3)3 for 0.5 to 1.5 hours.

[0015] Furthermore, in some embodiments of the present invention, the immersion time in the mixed solution of Bi(NO3)3 and KI obtained in step S1 is 2 to 4 hours.

[0016] Furthermore, in some embodiments of the present invention, the fuel of the flame in step S3 is ethanol.

[0017] Furthermore, in some embodiments of the present invention, the burning time in step S3 is 3-10 min, preferably 5-10 min.

[0018] On the other hand, the present invention also provides a Bi7O9I3 / graphite paper flexible composite photocatalyst with a hierarchical structure, wherein the Bi7O9I3 / graphite paper flexible composite photocatalyst substrate with a hierarchical structure is flexible graphite paper, Bi7O9I3 is formed by in-situ oxidation of BiOI in a precursor, and has a hierarchical structure similar to the original BiOI.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] In the existing preparation methods, Bi7O9I3 is mainly prepared by calcination or hydrothermal method, and its composite with carbonaceous materials is mainly to combine the pre-prepared Bi7O9I3 with materials such as graphene oxide by hydrothermal and self-assembly methods. In the prepared composite material, the combination of Bi7O9I3 and the carbonaceous substrate material is not tight, and the composite is not macroscopic, and the effective separation of photogenerated charges cannot be achieved, and the recovery is inconvenient. The present invention uses an in-situ deposition method to first in-situ deposit BiOI on graphite paper to prepare a precursor in which BiOI is tightly combined with graphite paper, and the BiOI in the precursor forms an obvious hierarchical structure. By burning with an ethanol flame, BiOI is in-situ converted into Bi7O9I3 to form a Bi7O9I3 / graphite paper composite photocatalyst with a hierarchical structure. At the same time, since the burning time is much shorter than the calcination time, the oxidation of graphite is weaker, which can ensure that the graphite paper maintains its original flexibility and graphite structure. It can not only effectively separate the photogenerated carriers of Bi7O9I3 in the composite, but also make the composite soft, cuttable, and able to be operated by hand. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the XRD spectra of graphite paper (CP), BiOI, Bi7O9I3, BiOI / graphite paper (BiOI-CP) and Bi7O9I3 / graphite paper (Bi7O9I3-CP) in Example 1 of the present invention;

[0022] Figure 2 (a) is the BiOI / graphite paper (BiOI-CP) in Example 1 of the present invention, (b) is the SEM image of Bi7O9I3 / graphite paper (Bi7O9I3-CP) in Example 1 of the present invention (the inset is an optical photograph);

[0023] Figure 3 It is a performance comparison of the photocatalytic degradation of phenol by BiOI / graphite paper (BiOI-CP) and Bi7O9I3 / graphite paper (Bi7O9I3-CP) in Example 1 of the present invention;

[0024] Figure 4 The degradation rate (1-C / C0) of phenol when the catalyst prepared in Examples 1-6 of the present invention degrades phenol for 90 min. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. It should be understood that the following description is only used to explain the present invention and is not intended to limit the present invention.

[0026] As used herein, the terms "comprises," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0027] When amount, concentration or other value or parameter is expressed as range, preferred range or a series of upper preferred value and lower preferred value limit range, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when disclosing range "1 to 5", described range should be interpreted as including range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When numerical range is described in this article, unless otherwise stated, the range is intended to include its end value and all integers and fractions within the range.

[0028] Singular forms include plural references unless the context clearly indicates otherwise. "Optional" or "either" means that the subsequently described event or incident may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

[0029] The indefinite articles "a" and "an" before the elements or components of the present invention have no limitation on the quantity requirements (i.e. the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the quantity obviously refers to the singular form only.

[0030] In addition, the descriptions of the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" described below mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0031] Example 1

[0032] Bi(NO3)3 ethylene glycol solution (for the convenience of description, marked as solution A): Weigh a certain amount of Bi(NO3)3 and add ethylene glycol to prepare a 1g / L solution.

[0033] Mixed solution of Bi(NO3)3 and KI (marked as solution B for convenience): Weigh a certain amount of Bi(NO3)3 and KI with a molar ratio of 1:1. According to the amount of Bi(NO3)3 weighed, add a mixed solvent of ethylene glycol and water in a volume ratio of 1.5:1 to make the concentration of Bi(NO3)3 12g / L.

[0034] The graphite paper was immersed in solution A for 1 hour, then rinsed with ethylene glycol, and then immersed in solution B for 3 hours until a red solid was deposited on the graphite paper to obtain a BiOI / graphite paper precursor. After rinsing and drying, the BiOI / graphite paper precursor was placed on an ethanol flame for calcination for 5 minutes. At this time, the red deposit turned yellow to obtain a Bi7O9I3 / graphite paper composite. The Bi7O9I3 in the composite had a hierarchical structure similar to that of BiOI.

[0035] Figure 1 XRD patterns of the BiOI / graphite paper precursor and Bi7O9I3 / graphite paper flexible composite photocatalyst prepared in Example 1 of the present invention; the structure of Bi7O9I3 is determined based on existing theoretical calculations and experimental reports.

[0036] Figure 2 This is the SEM image of the BiOI / graphite paper precursor and Bi7O9I3 / graphite paper flexible composite photocatalyst prepared in Example 1 of the present invention (the inset is an optical photograph); the hierarchical structure, color and flexibility of Bi7O9I3 / graphite paper can be seen.

[0037] Figure 3 The performance comparison of the Bi7O9I3 / graphite paper flexible composite photocatalyst prepared in Example 1 of the present invention with Bi7O9I3 powder and BiOI / graphite paper in catalytic degradation of phenol is shown. The relative concentration of phenol (C / C0) is used to reflect the degradation of phenol. The reduction of phenol is determined according to the decrease of C / C0 over time. The greater the decrease of C / C0, the more phenol is degraded. As can be seen from the figure, the photocatalytic effect of the Bi7O9I3 / graphite paper composite photocatalyst prepared in the embodiment of the present invention is significantly better than that of Bi7O9I3 powder and BiOI / graphite paper precursor.

[0038] Example 2

[0039] The difference between Example 2 and Example 1 is that in step S1, the molar ratio of Bi(NO3)3 and KI is 0.5:1, and the concentration of the Bi(NO3)3 solution is 10 g / L.

[0040] Example 3

[0041] The difference between Example 3 and Example 1 is that in step S1, the molar ratio of Bi(NO3)3 and KI is 2:1, and the concentration of the Bi(NO3)3 solution is 20 g / L.

[0042] Example 4

[0043] The difference between Example 4 and Example 1 is that in step S1, the volume ratio of ethylene glycol to water is 1:1, and the burning time in step S3 is 8 minutes.

[0044] Example 5

[0045] The difference between Example 5 and Example 1 is that in step S1, the volume ratio of ethylene glycol to water is 6:1, and the burning time in step S3 is 3 minutes.

[0046] Example 6

[0047] The difference between Example 6 and Example 1 is that the burning time in step S3 is 8 minutes.

[0048] Examples 2-6 prepare Bi7O9I3 / graphite paper composites with different proportions of Bi7O9I3, but all are Bi7O9I3 / graphite paper composites with comparable performance to that of Example 1.

[0049] Figure 4 The degradation rate (1-C / C0) of phenol when the samples prepared in Examples 1-6 degraded phenol for 90 minutes indicated that Example 1 had the best degradation effect, the performance of Examples 2-6 was roughly equivalent to that of Example 1, and the performance of Example 5 was relatively poor.

[0050] It will be easily understood by those skilled in the art that the above description is merely an example of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a Bi7O9I3 / graphite paper flexible composite photocatalyst with a hierarchical structure, characterized in that: The preparation method of the Bi7O9I3 / graphite paper flexible composite photocatalyst with a hierarchical structure comprises the following steps: S1, adding Bi(NO3)3 and KI into a mixed solvent of ethylene glycol and water to prepare a mixed solution of Bi(NO3)3 and KI; S2, the graphite paper is immersed in an ethylene glycol solution of Bi(NO3)3, and then rinsed with ethylene glycol to remove the Bi(NO3)3 solution adhering to the surface of the graphite paper, and immersed in a mixed solution of Bi(NO3)3 and KI obtained in step S1 until a red precipitate appears on the graphite paper, and after rinsing and drying, a BiOI / graphite paper composite precursor is obtained; S3, burning the prepared BiOI / graphite paper composite precursor on a flame, so that the red deposit on the precursor turns yellow, and the BiOI in the precursor is in situ converted into oxygen-rich Bi7O9I3, forming a Bi7O9I3 / graphite paper flexible composite.

2. The method for preparing the Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure according to claim 1, characterized in that: In step S1, the volume ratio of ethylene glycol to water is 1:1 to 6:

1.

3. The method for preparing the Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure according to claim 1, characterized in that: The concentration of Bi(NO3)3 in the mixed solution of step S1 is 10-20 g / L.

4. The method for preparing the Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure according to claim 1, characterized in that: The molar ratio of Bi(NO3)3 to KI in step S1 is 0.5:1 to 2.0:

1.

5. The method for preparing the Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure according to claim 1, characterized in that: The concentration of the Bi(NO3)3 ethylene glycol solution in step S2 is 0.7-1.3 g / L.

6. The method for preparing the Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure according to claim 1, characterized in that: In step S2, the graphite paper is immersed in the ethylene glycol solution of Bi(NO3)3 for 0.5 to 1.5 hours.

7. The method for preparing the Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure according to claim 1, characterized in that: In the step S2, the immersion time in the mixed solution of Bi(NO3)3 and KI obtained in the step S1 is 2 to 4 hours.

8. The method for preparing the Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure according to claim 1, characterized in that: The fuel of the flame in step S3 is ethanol.

9. The method for preparing the Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure according to claim 1, characterized in that: The burning time in step S3 is 3-10 minutes.

10. The method for preparing the Bi7O9I3 / graphite paper flexible composite photocatalyst with hierarchical structure according to claim 1, characterized in that: The burning time in step S3 is 5-10 minutes.

11. A Bi7O9I3 / graphite paper flexible composite photocatalyst with a hierarchical structure, characterized in that: The Bi7O9I3 / graphite paper flexible composite photocatalyst with a hierarchical structure is prepared by the method described in any one of claims 1 to 10, wherein the substrate is a flexible graphite paper, and Bi7O9I3 is formed by in-situ oxidation of BiOI in a precursor and has a hierarchical structure similar to that of the original BiOI.

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