阅读说明：本技术 一种基于共价有机骨架的光阳极材料及其制备方法和应用 (Photoanode material based on covalent organic framework and preparation method and application thereof ) 是由 申燕 周志明 陈金金 于 2020-07-16 设计创作，主要内容包括：本发明属于材料制备领域,具体公开一种基于共价有机骨架的光阳极材料及其制备方法和应用,材料包括助催化剂和基于三嗪结构的共价有机骨架；其中,助催化剂和基于三嗪结构的共价有机骨架通过层层堆积构成二维层状结构,优选的助催化剂为MoS-2。本发明采用的基于三嗪结构的共价有机骨架材料具有高结晶性、高比表面积和良好的化学稳定性,且由于N组分含量丰富,有较强的可见光吸收性质,能够作为优良的非均相光催化剂,另外结合助催化剂,由助催化剂与基于三嗪结构的共价有机骨架(TTZ-COF)通过层层堆积构成二维层状结构,作为光阳极材料,能够有效提高光阳极材料的光利用率,保证光分解水的效率。(The invention belongs to the field of material preparation, and particularly discloses a photo-anode material based on a covalent organic framework, a preparation method and application thereof, wherein the material comprises a cocatalyst and a covalent organic framework based on a triazine structure; wherein the cocatalyst and the covalent organic framework based on the triazine structure form a two-dimensional layered structure through layer-by-layer stacking, and the preferred cocatalyst is MoS 2 . The covalent organic framework material based on the triazine structure has high crystallinity, high specific surface area and good chemical stability, and has stronger visible light due to rich N component contentThe absorption property can be used as an excellent heterogeneous photocatalyst, in addition, the catalyst promoter is combined, the catalyst promoter and a triazine structure-based covalent organic framework (TTZ-COF) form a two-dimensional layered structure through layer-by-layer stacking, and the two-dimensional layered structure is used as a photo-anode material, so that the photo-utilization rate of the photo-anode material can be effectively improved, and the photo-decomposition efficiency of water is ensured.)

1. A photoanode material based on a covalent organic framework, which is characterized by comprising a cocatalyst and a covalent organic framework based on a triazine structure; wherein the cocatalyst and the triazine structure-based covalent organic framework form a two-dimensional layered structure by layer-by-layer stacking.

2. The photoanode material based on a covalent organic framework of claim 1, wherein the co-catalyst is MoS₂。

3. The photoanode material based on a covalent organic framework of claim 2, wherein the MoS is selected from the group consisting of₂The mass percentage of the covalent organic framework is 1-10%.

4. A method of preparing the photoanode material based on a covalent organic framework of claim 1, comprising:

and (2) adding a cocatalyst, 4 '- (1,3, 5-triazine-2, 4, 6-triyl) triphenylamine and 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tri [ benzaldehyde ] into a mixed system consisting of 1, 4-dioxane, mesitylene and an aqueous solution of acetic acid, and reacting at 100-130 ℃ for 3-5 days to obtain the photoanode material based on the covalent organic framework.

5. The method of claim 4, wherein the co-catalyst is usedThe agent is MoS₂The method specifically comprises the following steps:

s1, MoS₂Dispersed in the mixed system and sonicated to obtain a uniformly dispersed MoS₂Suspending the 4,4 '- (1,3, 5-triazine-2, 4, 6-triyl) triphenylamine and the 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tris [ benzaldehyde]Is thrown into the MoS₂Suspending liquid to obtain mixed solution and carrying out ultrasonic oscillation on the mixed solution;

s2, performing flame sealing on a reaction vessel where the mixed solution after ultrasonic vibration is located, placing the reaction vessel at 100-130 ℃ for reaction for 3-5 days, generating solid powder and recycling the solid powder to prepare the photo-anode material based on the covalent organic framework.

6. The method according to claim 4, wherein the molar ratio of 4,4',4 "- (1,3, 5-triazine-2, 4, 6-triyl) triphenylamine to 4,4', 4" - (1,3, 5-triazine-2, 4, 6-triyl) tris [ benzaldehyde ] is 1: 1.

7. The method according to claim 4, wherein the concentration of the aqueous acetic acid solution is 3 to 7 mol/L.

8. The method according to claim 4, wherein the volume ratio of the 1, 4-dioxane to the mesitylene is 1:2 to 1: 5.

9. The method according to claim 4, wherein the molar ratio of the 1, 4-dioxane to the acetic acid in the aqueous acetic acid solution is 5: 4.

10. Use of a photoanode material based on a covalent organic framework according to any of claims 1 to 3 for photoelectrochemical decomposition of water.

Technical Field

The invention belongs to the field of material preparation, and particularly relates to a photoanode material based on a covalent organic framework, and a preparation method and application thereof.

Background

In response to global climate warming and sustainable demand for alternative fuels, solar-driven photoelectrochemical split water has received much attention as a green, sustainable regenerative and alternative energy prospective solution.

In the photoelectrochemical water decomposition process, the surface of the photoactive material absorbs light under the action of light to obtain energy to generate photo-generated electrons and holes, and the photo-generated electrons and the holes are separated under the action of bias voltage to respectively participate in Hydrogen Evolution Reaction (HER) on a photocathode and Oxygen Evolution Reaction (OER) on a photoanode. The main challenge of this system is how to accelerate the slow kinetic OER process on the photoanode.

However, most of the conventional photocatalysts (i.e., photoanode materials) in photoactive materials are concentrated on inorganic semiconductor materials, and cannot meet the increasing demand for high efficiency of photodecomposition of water.

Disclosure of Invention

The invention provides a photo-anode material based on a covalent organic framework, and a preparation method and application thereof, which are used for solving the technical problem of low efficiency in the photo-decomposition and water-hydration of the existing photo-anode material.

The technical scheme for solving the technical problems is as follows: a photoanode material based on a covalent organic framework, comprising a co-catalyst and a covalent organic framework based on a triazine structure; wherein the cocatalyst and the triazine structure-based covalent organic framework form a two-dimensional layered structure by layer-by-layer stacking.

The invention has the beneficial effects that: the covalent organic framework material based on the triazine structure has high crystallinity, high specific surface area and good chemical stability, and can be used as an excellent heterogeneous photocatalyst due to the rich content of N component and strong visible light absorption property, and in addition, the promoter is combined, and the promoter and the covalent organic framework (TTZ-COF) based on the triazine structure are stacked layer by layer to form a two-dimensional layered structure as a photoanode material, so that the light utilization rate of the photoanode material can be effectively improved, and the efficiency of photolysis of water is ensured.

On the basis of the technical scheme, the invention can be further improved as follows.

Further, the cocatalyst is MoS₂。

The invention has the further beneficial effects that: by introducing MoS₂As a cocatalyst, the composite photo-anode material can further enhance the light absorption of the composite photo-anode material, improve the separation efficiency of photo-generated electrons and hole pairs, accelerate the transfer of interface charges of the composite photo-anode material, and show good water decomposition activity of photoelectrocatalysis.

Preferably, the MoS₂The mass percentage of the covalent organic framework is 1-10%.

The invention also provides a preparation method of the photoanode material based on the covalent organic framework, which comprises the following steps:

and (2) adding a cocatalyst, 4 '- (1,3, 5-triazine-2, 4, 6-triyl) triphenylamine and 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tri [ benzaldehyde ] into a mixed system consisting of 1, 4-dioxane, mesitylene and an aqueous solution of acetic acid, and reacting at 100-130 ℃ for 3-5 days to obtain the photoanode material based on the covalent organic framework.

The invention has the beneficial effects that: by introducing the cocatalyst and a cocatalyst/TTZ-COF (thermal transfer radical-COF) co-catalytic composite system synthesized by in-situ reaction under the solvothermal condition, the light absorption of the composite light anode material can be further enhanced, the separation efficiency of photo-generated electrons and hole pairs is improved, the transfer of interface charges is accelerated, good water decomposition activity of photoelectrocatalysis is shown, and the covalent organic framework material based on the triazine structure has better application potential in the field of photoelectrocatalysis water decomposition.

Preferably, when the cocatalyst is MoS₂The method specifically comprises the following steps:

s1, MoS₂Dispersed in the mixed systemAnd sonicated to obtain a uniformly dispersed MoS₂Suspending the 4,4 '- (1,3, 5-triazine-2, 4, 6-triyl) triphenylamine and the 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tris [ benzaldehyde]Is thrown into the MoS₂Suspending liquid to obtain mixed solution and carrying out ultrasonic oscillation on the mixed solution;

s2, performing flame sealing on a reaction vessel where the mixed solution after ultrasonic vibration is located, placing the reaction vessel at 100-130 ℃ for reaction for 3-5 days, generating solid powder and recycling the solid powder to prepare the photo-anode material based on the covalent organic framework.

The invention has the further beneficial effects that: the equipment and chemical reagents used in the synthetic method are easy to obtain, the preparation condition is mild, the process operation is simple and convenient, the cost is low, the popularization and the utilization are easy, and the method has a great industrial application prospect.

Preferably, the molar ratio of the 4,4 '- (1,3, 5-triazine-2, 4, 6-triyl) triphenylamine to the 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tris [ benzaldehyde ] is 1: 1.

Preferably, the concentration of the acetic acid aqueous solution is 3-7 mol/L.

Preferably, the volume ratio of the 1, 4-dioxane to the mesitylene is 1: 2-1: 5.

Preferably, the molar ratio of the 1, 4-dioxane to the acetic acid in the aqueous acetic acid solution is 5: 4.

The invention has the further beneficial effects that: the reasonable volume ratio or molar ratio of the 1, 4-dioxane, the mesitylene and the acetic acid aqueous solution can ensure the reaction rate of the in-situ reaction and the crystallinity of the finally obtained photo-anode material, thereby improving the quality of the product.

The invention also provides the application of the photoanode material based on the covalent organic framework, which is used for photoelectrochemical water decomposition.

The invention has the beneficial effects that: the photoanode material based on the covalent organic framework can efficiently realize water decomposition, and is environment-friendly and low in cost.

Drawings

FIG. 1 is a schematic structural diagram of a photoanode material based on a covalent organic framework according to an embodiment of the present invention;

FIG. 2 shows a MoS according to an embodiment of the present invention₂X-ray powder diffractograms of/TTZ-COF, TTZ-COF and synthetic monomers;

FIG. 3 shows a MoS according to an embodiment of the present invention₂Fourier transform infrared spectrograms of/TTZ-COF, TTZ-COF and synthetic monomers;

FIG. 4 shows a MoS according to an embodiment of the present invention₂X-ray powder diffraction patterns of/TTZ-COF after treatment in various solution conditions;

FIG. 5 shows a MoS according to an embodiment of the present invention₂a/TTZ-COF solid ultraviolet absorption spectrum diagram;

FIG. 6 shows a MoS according to an embodiment of the present invention₂the/TTZ-COF photoelectrochemical linear scanning voltammetry test chart.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example one

A photoanode material based on a covalent organic framework, comprising a co-catalyst and a covalent organic framework based on a triazine structure; wherein the cocatalyst and the covalent organic framework based on the triazine structure form a two-dimensional layered structure through layer-by-layer stacking.

The triazine structure-based covalent organic framework material has high crystallinity, high specific surface area and good chemical stability, and can be used as an excellent heterogeneous photocatalyst due to the rich content of N component and strong visible light absorption property, the embodiment proposes that a cocatalyst and a covalent organic framework TTZ-COF are stacked layer by layer to form a two-dimensional layered structure as a photoanode material, the structure is shown in figure 1, and each ring represents one structural unit. The covalent organic framework in the photo-anode material is rich in imine bonds (-C ═ N-) and triazine groups, so that nitrogen atom components in the structure are rich, and the photo-anode material has good visible light absorption property.

Wherein, the structural unit of the covalent organic framework based on the triazine structure is as follows:

wherein the cocatalyst can be MoS₂CoS and CdS, etc., preferably the cocatalyst is MoS₂. By introducing MoS₂As a cocatalyst, the composite photo-anode material can further enhance the light absorption of the composite photo-anode material, improve the separation efficiency of photo-generated electrons and hole pairs, accelerate the transfer of interface charges of the composite photo-anode material, and show good water decomposition activity of photoelectrocatalysis. It should be noted that the stacking position of the cocatalyst on the organic framework may be random.

Preferably, MoS₂The mass percentage of the organic skeleton to the covalent organic skeleton is 1-10%. The structure of the photoanode material shown in FIG. 1 is that under the condition that the mass of the covalent organic framework is constant, MoS is covered on the photoanode material₂The larger the number, the more MoS₂The greater the mass percent of the organic skeleton to be copolymerized, when MoS₂When the mass percentage of the photo-anode material to the covalent organic framework is 1-10%, the obtained photo-anode material can show good photo-catalytic water decomposition activity, and the optional MoS₂The mass percentage of the organic skeleton to the covalent organic skeleton is preferably 5%.

Example two

A method for preparing a photoanode material based on a covalent organic framework as described in example one, comprising: and (2) adding a cocatalyst, 4 '- (1,3, 5-triazine-2, 4, 6-triyl) triphenylamine and 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tri [ benzaldehyde ] into a mixed system consisting of 1, 4-dioxane, mesitylene and an aqueous solution of acetic acid, and reacting at 100-130 ℃ for 3-5 days to obtain the photoanode material based on the covalent organic framework.

By introducing the cocatalyst and a cocatalyst/TTZ-COF (thermal transfer radical-COF) co-catalytic composite system synthesized by in-situ reaction under the solvothermal condition, the light absorption of the composite light anode material can be further enhanced, the separation efficiency of photo-generated electrons and hole pairs is improved, the transfer of interface charges is accelerated, good water decomposition activity of photoelectrocatalysis is shown, and the covalent organic framework material based on the triazine structure has better application potential in the field of photoelectrocatalysis water decomposition.

For example, when the cocatalyst is MoS₂The specific reaction route is as follows:

specific examples are as follows:

mixing MoS₂(1.5mg) was dispersed in a mixed solution of 1, 4-dioxane/mesitylene (1:3v/v, 1.0mL) and sonicated for 4h to obtain a uniformly dispersed black suspension. 4,4 '- (1,3, 5-triazine-2, 4, 6-triyl) triphenylamine (18.02mg, 50.84. mu. mol) and 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tris [ benzaldehyde](20.0mg, 50.84. mu. mol) was added to a Pyrex tube (body length 20cm, neck length 1cm) having a volume of 5mL, and dissolved in the above MoS at room temperature₂The black suspension and 6.0M aqueous acetic acid (0.2mL) were sonicated for 15 minutes. The Pyrex tubes were then snap frozen and thawed in a liquid nitrogen bath, evacuated three times to an internal pressure of 0mbar and flame sealed. After cooling to room temperature, the Pyrex tube was placed in an oven at 120 ℃ for 3 days to obtain a dark green solid powder. The powder was collected by suction filtration, washed three times with anhydrous tetrahydrofuran and three times with acetone. The greenish black powder was dried overnight under vacuum at 80 ℃ to yield a photo-anode material based on covalent organic frameworks MoS 2/TTZ-COF.

Preferably, the concentration of the acetic acid aqueous solution can be any concentration within 3-7 mol/L, the concentration of the acetic acid aqueous solution can influence the reaction rate, and the crystallinity of the final product can be influenced by too high or too low concentration.

Preferably, the volume ratio of the 1, 4-dioxane to the mesitylene is 1 (2-5), and when the volume ratio is too high or too low, the crystallinity of a final product is influenced, and further the quality of the product is influenced. For the same reason, it is preferable that the molar ratio of 1, 4-dioxane to acetic acid in the aqueous acetic acid solution is 5:4, 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tris [ benzaldehyde ] to acetic acid is 1 (8-12).

In order to verify the beneficial effects of the invention, a preparation method of the traditional triazine structure-based covalent organic framework material TTZ-COF is provided, which comprises the following steps:

4,4 '- (1,3, 5-triazine-2, 4, 6-triyl) triphenylamine (18.02mg, 50.84. mu. mol) and 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tris [ benzaldehyde ] (20.0mg, 50.84. mu. mol) were added to a 1.2mL 1, 4-dioxane/mesitylene/6M aqueous acetic acid mixed system (v: v: v ═ 5:15:4), and placed in a Pyrex tube (body length 20cm, neck length 1cm) having a volume of 5mL, and sonicated for 10 minutes. The Pyrex tubes were then snap frozen and thawed in a liquid nitrogen bath, evacuated three times to an internal pressure of 0mbar and flame sealed. The Pyrex tube was then placed in an oven at 120 ℃ for 3 days to react, yielding a yellow solid powder. The powder was collected by suction filtration, washed three times with anhydrous tetrahydrofuran and three times with acetone. The yellow powder was dried under vacuum at 80 ℃ overnight to give the covalent organic framework material TTZ-COF based on triazine structure in 80% yield.

Photo-anode material MoS based on covalent organic framework prepared as exemplified above₂The X-ray powder diffraction pattern of the/TTZ-COF is shown in FIG. 2, and the Fourier transform infrared spectrum is shown in FIG. 3. MoS₂Crystallinity of/TTZ-COF determined by powder X-ray diffraction (PXRD) analysis, MoS₂The X-ray powder diffraction pattern of/TTZ-COF is similar to that of TTZ-COF, and PXRD pattern shows peaks at 2 θ ═ 3.9o, 6.9o, 8.1o, 10.7o and 25.8o, which correspond to the 100, 110, 200, 210 and 001 crystal planes respectively (see fig. 2 in particular). Due to MoS₂Is added in a low content and uniformly dispersed, and therefore in MoS₂No MoS was clearly observed in the/TTZ-COF composites₂Due to MoS₂The diffraction peak of (a) is covered by the diffraction peak intensity of the organic skeleton. MoS₂Fourier transform infrared spectroscopy of/TTZ-COF and TTZ-COF showed significant stretching vibration at 1621-1606cm-1, indicating 4,4' - (1)3, 5-triazine-2, 4, 6-triyl) triphenylamine and 4,4' - (1,3, 5-triazine-2, 4, 6-triyl) tris [ benzaldehyde]Successful condensation forms imine linkages (-C ═ N-), the two strong absorption bands at 1505cm-1 and 1359cm-1 corresponding to the triazine rings of TTZ-COF (see in particular FIG. 3).

Further performing MoS₂Chemical stability test of/TTZ-COF. 20mg of MoS₂the/TTZ-COF samples were immersed overnight in 10mL of Acetonitrile (ACN), Dimethylformamide (DMF), 1M aqueous NaOH, 1M aqueous HCl and boiling distilled water (H2O), respectively, at room temperature. The sample was then rinsed with acetone and recovered by suction filtration, dried at 80 ℃ for 12h under vacuum and characterized by PXRD, as shown in FIG. 4, for the photo-anode material MoS₂No obvious change appears in the diffraction peak intensity and peak position of the/TTZ-COF, which indicates that the crystal degree and the structural integrity of the/TTZ-COF can be maintained in common organic solvents, water and acid-base aqueous solutions.

Further performing MoS₂And testing the performance of the photoelectrochemical linear scanning voltammetry of the/TTZ-COF. Photoelectrochemical activity tests were performed using an electrochemical workstation of standard three-electrode configuration (CHI 660D), in which MoS₂the/TTZ-COF photoanode (irradiation area of 1cm2), Ag/AgCl electrode and platinum wire were used as working electrode, reference electrode and counter electrode, respectively. 0.1M Na was used₂SO₄(pH 7) as an electrolyte and high purity N was used before testing₂Purge for 20 minutes to remove any dissolved oxygen. Linear Sweep Voltammetry (LSV) measurements of the prepared films were recorded at a scan rate of 10mV s-1 under chopped illumination (5 second on/off cycle) using a 300W xenon lamp (Newport, model 69911, USA) in combination with an AM 1.5G filter. MoS₂the/TTZ-COF has a similar UV broad absorption band as TTZ-COF, since MoS₂Is introduced so that MoS₂The absorption intensity of/TTZ-COF is higher than that of TTZ-COF (see FIG. 5). At the same potential, MoS compared with TTZ-COF₂the/TTZ-COF shows higher photocurrent intensity, indicating MoS₂The photoelectrochemical activity of/TTZ-COF was higher (see FIG. 6).

EXAMPLE III

Use of a photoanode material based on a covalent organic framework as described in example one above for photoelectrochemical decomposition. Specifically, the application may be that the photoanode material based on covalent organic framework described in the first embodiment is covered on an FTO substrate to serve as an anode for photoelectrochemical water splitting.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.