Preparation of Pt NPs (at) CNQDs / TpTAPyT-COF catalyst material and photocatalytic full decomposition of water

Abstract

The invention provides a novel Pt NPs (at) CNQDs / TpTAPyT-COF catalyst material, and aims to solve the problems that the absorption light response range of TpTAPyT-COF is wide, and electron holes are easy to compound. The method comprises the following steps: 1, preparing Pt NPs; 2, preparing the CNQDs; and 3, preparation of the Pt NPs (at) CNQDs / TpTAPyT-COF composite material. The preparation process is simple and effective, the reagent consumption is low, and the performance is high; the photocatalyst provided by the invention can effectively solve the problem of low photocatalytic water decomposition efficiency. The composite material is applied to the field of photocatalytic full water decomposition, experiments show that the composite material has excellent photocatalytic water decomposition performance, the water decomposition hydrogen production rate under visible light irradiation can reach 391.96 [mu] mol.h <-1 >. G <-1 >, and the oxygen production efficiency is 195.45 [mu] mol.h <-1 >. G <-1 >.

Description

Technical Field

[0001] The invention relates to the preparation of a PtNPs@CNQDs / TpTAPyT-COF catalyst material and photocatalytic complete water splitting.

[0002] With the continuous development of science and technology, the increasing depletion of fossil fuels, the demand for new clean energy continues to expand. Among them, photocatalytic water splitting is a technology that uses light energy to drive the decomposition of water into hydrogen and oxygen, and catalysts play a key role in this process. In principle, photocatalytic water splitting includes two half reactions, namely the reaction of water oxidation to generate oxygen (oxygen production reaction) and the reaction of water reduction to generate hydrogen (hydrogen production reaction). After the photocatalyst absorbs photons, the valence band electrons are excited to the conduction band, thereby generating electron-hole pairs. These photogenerated carriers migrate to the surface of the catalyst and participate in the hydrogen production and oxygen production reactions respectively. However, although some inorganic semiconductors and metal oxides can photocatalytically split water, they often bring many problems due to their shortcomings such as low electron-hole recombination efficiency and environmental pollution. Therefore, it is urgent to develop new materials to solve such problems.

[0003] Covalent organic frameworks (COFs) are a class of crystalline porous polymers formed by organic monomers connected by covalent bonds. TpTAPyT-COF, as one of them, has a highly ordered two-dimensional or three-dimensional pore structure and a large specific surface area, which provides abundant space for the adsorption and diffusion of molecules. At the same time, the π-π conjugated system in its skeleton structure is conducive to the transmission of electrons, showing good application potential in gas storage, separation, catalysis and other fields. However, TpTAPyTCOF itself also has certain limitations, such as the limited absorption range of visible light in the photocatalytic process, and the migration rate of photogenerated carriers needs to be further improved. Carbon nitride quantum dots, as a new type of carbon nanomaterial, have excellent optical properties, such as good fluorescence stability and high fluorescence quantum yield. Its size is usually below 10nm, and its surface is rich in various functional groups, which gives it good water solubility and biocompatibility. These characteristics make CNQDs have potential application value in the fields of bioimaging, sensors, photocatalysis and so on. However, CNQDs also face some challenges in practical applications. For example, when used alone, their photogenerated carriers are easy to recombine, resulting in limited photocatalytic efficiency; in some systems, the dispersion stability is poor, which affects the full performance of their performance. The CNQDs / TpTAPyTCOF composite material formed by combining CNQDs with TpTAPyT-COF is expected to complement the advantages of both. On the one hand, CNQDs can act as a sensitizer to broaden the response range of TpTAPyT-COF to light and improve the efficiency of photogenerated carrier generation; on the other hand, the regular pore structure and large specific surface area of ​​TpTAPyT-COF can provide a good dispersion carrier for CNQDs, inhibit the agglomeration of CNQDs, and promote the transmission and separation of photogenerated carriers. The synergistic effect of the two can show its excellent performance in photocatalytic water splitting. Summary of the invention

[0004] The purpose of the present invention is to solve the problem of low efficiency of photocatalytic water splitting of current materials, and to provide a preparation method of PtNPs@CNQDs / TpTAPyT-COF catalyst material and application of photocatalytic water splitting.

[0005] The preparation method of Pt NPs@CNQDs / TpTAPyT-COF of the present invention is completed by the following steps: 1. Preparation of Pt NPs@CNQDs / TpTAPyT-COF material: A certain amount of 2,4,6-tris(4-aminopyridinyl)-1,3,5-triazine was dissolved in 1 ml DMSO solution and added to a Pyrex tube, to which a certain amount of 1,3,5-trialdehyde phloroglucinol ethanol dispersion and a certain amount of CNQDs aqueous dispersion were added, and ultrasonicated at 120 Hz for 2 h, followed by adding 17 mol / L acetic acid solution, and degassed by cyclic freezing and degassing in liquid nitrogen three times. After sealing, the mixture was heated at 120 °C for 72 h. After the reaction, it was filtered and washed several times with DMF and ethanol in turn, and dried in vacuo at 80 °C to obtain a yellow powder, which is the PtNPs@CNQDs / TpTAPyT-COF catalyst material. The concentration of the DMSO solution containing PtNPs used in step 1 is 2.96 mg / ml; The mass ratio of PtNPs to TpTAPyT-COF in step 1 is 0.05:1; The concentration of the CNQDs aqueous dispersion used in step 1 is 30 mg / ml; The molar ratio of 2,4,6-tris(4-aminopyridyl)-1,3,5-triazine to 1,3,5-trialdehyde phloroglucinol in step 1 is 1:1; The volume ratio of DMSO, ethanol and acetic acid in step 1 is 5:5:2; After sealing as described in step 1, heat at 120°C for 72h.

[0006] Beneficial effects of the present invention: The present invention adopts the solvothermal method, takes 2,4,6-tris(4-aminopyridyl)-1,3,5-triazine and 1,3,5-trialdehyde phloroglucinol as raw materials, and successfully synthesizes PtNPs@CNQDs / TpTAPyT-COF by in situ addition of PtNPs and CNQDs. The hydrogen production efficiency is measured to be 391.96 μmol·h -1 ·g -1 Compared with PtNPs@TpTAPyT-COF, the efficiency of hydrogen production from water decomposition under visible light is lower at 148 μmol·h -1 ·g -1 Therefore, the material effectively improves the photocatalytic water splitting performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 X-ray powder diffraction pattern of Pt NPs@CNQDs / TpTAPyT-COF material; Figure 2 Infrared spectrum of PtNPs@CNQDs / TpTAPyT-COF material; Figure 3This is the photocatalytic water decomposition and hydrogen production performance diagram of PtNPs@CNQDs / TpTAPyT-COF material.

[0008] The present invention is further described below with reference to examples. These examples are only used to illustrate the method of the present invention and have no limitation on the scope of application of the present invention.

[0009] Example 1: The preparation of a PtNPs@CNQDs / TpTAPyT-COF material of this embodiment is completed by the following steps: 1. Preparation of Pt nanoparticles: Weigh a certain amount of polyvinyl pyrrolidone (PVP) and put it into a three-necked bottle. Add ethylene glycol solution containing sodium hydroxide into it, stir and heat it under vacuum, put it into a reactor at 180°C for 3 minutes. Cool it to room temperature, centrifuge the resulting solution with acetone, and wash it with n-hexane several times. Finally, the nanoparticles are dispersed in 2 ml of dimethyl sulfoxide solution. The concentration of the chloroplatinic acid solution in step 1 is 7.4 mg / ml; The concentration of the ethylene glycol solution containing sodium hydroxide in step 1 is 0.15 mol·L -1 ; The volume ratio of the chloroplatinic acid solution, the ethylene glycol solution containing sodium hydroxide and ethylene glycol in step 1 is 0.5:1:5; The concentration of the DMSO solution containing PtNPS in step 1 is 2.96 mg / ml. 2. Preparation of CNQDs: 1.68mmol urea and 0.28mmol sodium citrate were mixed in agate mortar and ground into a uniform powder. The mixture was placed in an autoclave and heated to 180°C in a drying oven for 1 hour. The mixture was purified by alternating ethanol washing and centrifugation at 12000rpm three times, and then dialyzed against pure water for 24 hours through a dialysis membrane to obtain a light yellow mixture. The obtained CNQDs have good solubility in water and have bright fluorescence properties under ultraviolet light. The mass of urea described in step 2 is 0.101g; The mass of sodium citrate in step 2 is 0.081 g; The concentration of the CNQDs aqueous dispersion used in step 2 is 30 mg / ml; 3. Preparation of PtNPs@CNQDs / TpTAPyT-COF composite material: 14-16 mg of 2,4,6-tris(4-aminopyridinyl)-1,3,5-triazine was dissolved in 1 ml of DMSO solution and added to a Pyrex tube, to which was added 1 ml of 12-15 mg / ml 1,3,5-trialdehyde ethanol dispersion and 0.16 ml of 30 mg / ml CNQDs aqueous dispersion. The mixture was ultrasonicated at 120 Hz for 2 h, and then 17 mol / L acetic acid solution was added. The mixture was degassed by cyclic freezing and cycle degassing in liquid nitrogen three times, sealed, and heated at 120°C for 72 h. After the reaction, it was filtered and washed several times with DMF and ethanol in turn, and dried in vacuo at 80°C to obtain a yellow powder, which is the PtNPs@CNQDs / TpTAPyT-COF catalyst material. The step 3 is PtNPs@20%CNQDs / TpTAPyT-COF;

[0010] Example 2: This embodiment differs from Example 1 in that: in step three, 0.28 ml of 30 mg / ml CNQDs aqueous dispersion is added, and the other steps and parameters are the same as those in Example 1; Pt NPs@30% CNQDs / TpTAPyT-COF catalyst material is obtained.

[0011] Example 3: This embodiment differs from Example 1 in that: in step three, 0.45 ml of 30 mg / ml CNQDs aqueous dispersion is added, and the other steps and parameters are the same as those in Example 1; Pt NPs@40% CNQDs / TpTAPyTCOF catalyst material is obtained. To verify the beneficial effects of the present invention, the following tests were performed: In order to investigate the photocatalytic water splitting effect of PtNPs@30%CNQDs / TpTAPyT-COF catalyst material, the visible light photocatalytic water splitting performance was tested according to the following method. The test process and measurement results are as follows: PtNPs@30%CNQDs / TpTAPyT-COF (10 mg) was used as the photocatalyst and distilled water was used as the reaction liquid. Under visible light, the hydrogen production efficiency of the single PtNPs@TpTAPyT-COF photocatalytic water splitting was 148.0 μmol·h -1 ·g -1 , oxygen production is only 74 μmol·h -1 ·g -1 The Pt NPs@30% CNQDs / TpTAPyT-COF composite material exhibited excellent photocatalytic water splitting performance, with a photocatalytic water splitting hydrogen production efficiency of 391.96 μmol·h -1 ·g -1 , oxygen production efficiency is 195.45 μmol·h -1 ·g-1 。

Claims

1. Preparation of a Pt NPs@CNQDs / TpTAPyT-COF catalyst material and photocatalytic water splitting, characterized in that The method is carried out according to the following steps: Preparation of Pt NPs@CNQDs / TpTAPyT-COF material: a certain amount of 2,4,6-tris(4-aminopyridinyl)-1,3,5-triazine is dissolved in 1 ml of DMSO solution and added to a Pyrex tube, a certain amount of 1,3,5-trialdehyde phloroglucinol ethanol dispersion and a quantitative CNQDs aqueous dispersion are added thereto, ultrasonicated at a frequency of 120 Hz for 2 hours, then a 17 mol / L acetic acid solution is added, and the mixture is degassed by cyclic freezing and cycling in liquid nitrogen three times, sealed and heated at 120°C for 72 hours, filtered after the reaction and washed several times with DMF and ethanol in turn, and vacuum dried at 80°C to obtain a yellow powder, which is the Pt NPs@CNQDs / TpTAPyT-COF catalyst material.

2. The preparation of a Pt NPs@CNQDs / TpTAPyT-COF material according to claim 1, characterized in that The mass of 2,4,6-tris(4-aminopyridyl)-1,3,5-triazine described in step 2 is 14-16 mg, and the mass of 1,3,5-trialdehyde phloroglucinol is 12-15 mg. The concentration of the CNQDs aqueous dispersion solution is 30 mg / ml, and the amount added is 0.16-0.45 ml.

3. The preparation of a Pt NPs@CNQDs / TpTAPyT-COF material according to claim 1, characterized in that In step 2, the content ratio of CNQDs in TpTAPyT-COF is 20% to 40%.

4. The preparation of a Pt NPs@CNQDs / TpTAPyT-COF material according to claim 1, characterized in that The optimal ratio described in step 1 is 30%.

5. The preparation of a Pt NPs@CNQDs / TpTAPyT-COF material according to claim 1, characterized in that In step 2, the volume ratio of DMSO, ethanol and acetic acid is 5:5:2, and the optimal dosage of Pt is 0.45 ml.

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