Preparation of CQDs / Pt / TpBpy-COF double-promoter material and application of CQDs / Pt / TpBpy-COF double-promoter material in photocatalytic full water splitting

Abstract

The invention relates to preparation of a CQDs / Pt / TpBpy-COF composite material and photocatalytic water decomposition. The invention provides a novel CQDs / Pt / TpBpy-COF double-promoter composite material, and aims to solve the problems that the light utilization rate is low and electron holes are easy to compound when the conventional TpBpy-COF photocatalytically decomposes water. The method comprises the following steps: 1, preparing Pt nanoparticles; 2, preparation of CQDs (carbon quantum dots); (3) preparing a CQDs / Pt / TpBpy-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 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 232.1 [mu] mol.h <-1 >. G <-1 >, and the oxygen production efficiency is 115.5 [mu] mol.h <-1 >. G <-1 >.

Description

Technical Field

[0001] The invention relates to the preparation and photocatalysis of a CQDs / Pt / TpBpy-COF dual-promoter catalyst material. Background Art

[0002] With the rapid development of society and the continuous increase in population, the demand for energy in human social development is increasing day by day. The combustion of fossil fuels has inevitably led to two major problems: fossil energy shortage and ecological environmental pollution. Therefore, it is particularly important to develop and utilize clean, renewable green energy to replace fossil energy and change the environmental pollution problem. Among many energy sources, hydrogen energy has the advantages of being renewable, high in energy density, and zero pollution. It is considered to be one of the most promising energy sources to solve the energy crisis. Photocatalytic water splitting using inexhaustible solar energy as the driving force to produce hydrogen and oxygen is the cleanest and most effective way. However, due to the problem of easy recombination of electrons and holes in photocatalysts, the efficiency of water splitting is extremely low. Therefore, loading co-catalysts, enhancing electron transmission efficiency, and improving electron-hole separation efficiency are more effective ways.

[0003] Covalent Organic Frameworks (COFs) are a new type of crystalline porous material connected by covalent bonds. They are mainly composed of lightweight elements such as H, C, O, and N. They have the advantages of adjustable nanopore size, high specific surface area, pre-designed building units, rich active sites, designable chain structure, and programmable topological structure. COFs have shown great potential in many fields such as gas adsorption and separation, catalysis, sensing, energy storage, and photoelectric conversion, and have been widely developed. However, COFs photocatalysts have the problem of easy recombination of electron holes, which limits the overall water splitting activity of COFs photocatalysts. Therefore, loading different catalysts to improve the water splitting efficiency has become a research hotspot. Carbon quantum dots (CQDs) have high conductivity as a carbon material, so they are used as co-catalysts for recombination. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that electron holes in photocatalysts are easy to recombine and the water decomposition efficiency is low, and to provide a preparation method of a CQDs / Pt / TpBpy-COF dual-cocatalyst material and its application in photocatalytic water decomposition.

[0005] The preparation method of a CQDs / Pt / TpBpy-COF dual promoter material of the present invention is completed by the following steps: 1. Preparation of CQDs / Pt / TpBpy-COF dual promoter material: N,N-dimethylacetamide (DMA) solution containing Pt nanoparticles, N,N-dimethylacetamide solution containing CQDs, 5,5-diamino-2,2-bipyridine, and 1,3,5-trialdehyde phloroglucinol were added to a heat-resistant glass tube, and o-dichlorobenzene and DMA were added in sequence. The mixture was ultrasonically treated at an ultrasonic frequency of 35 to 45 kHz for 25 to 40 min, and then 6 mol·L -1 The acetic acid solution was cyclically frozen and degassed in liquid nitrogen three times, sealed, heated at 120°C for 72h, filtered and washed with DMA and ethanol several times, and vacuum dried at 80°C to obtain a reddish-brown powder, which is the CQDs / Pt / TpBpy-COF dual-promoter material. The concentration of the DMA solution containing Pt nanoparticles used in step 1 is 2.96 mg / mL; The mass ratio of the Pt nanoparticles to TpBpy-COF in step 1 is 0.05:1; The amount of N,N-dimethylacetamide solution containing CQDs used in step 1 added was 0.3 mL; The mass ratio of CQDs to TpBpy-COF in step 1 is 0.0036:1; The molar ratio of 5,5-diamino-2,2-bipyridine to 1,3,5-trialdehyde phloroglucinol in step 1 is 3:2; The volume ratio of o-dichlorobenzene, DMA and acetic acid in step 1 is 0.5:1.5:0.2; After sealing as described in step 1, heat at 120°C for 72h.

[0006] Beneficial effects of the present invention: The present invention adopts a solvothermal method, uses 5,5-diamino-2,2-bipyridine and 1,3,5-trialdehyde phloroglucinol as raw materials, and in situ adds Pt nanoparticles and CQDs to successfully synthesize CQDs / Pt / TpBpy-COF. However, the efficiency of this material in decomposing water to produce hydrogen without a catalyst under visible light is low, which is 96.0 μmol·h -1 ·g -1 Therefore, the invention adds another co-catalyst CQDs to Pt / TpBpy-COF for compounding to synthesize CQDs / Pt / TpBpy-COF dual-catalyst composite material, which effectively improves the photocatalytic water splitting performance, and the hydrogen production efficiency is 206-232 μmol·h -1 ·g -1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1is the X-ray powder diffraction pattern of CQDs / Pt / TpBpy-COF material; Figure 2 It is the infrared spectrum of CQDs / Pt / TpBpy-COF material; Figure 3 This is the performance diagram of photocatalytic water decomposition and hydrogen production of CQDs / Pt / TpBpy-COF material. DETAILED DESCRIPTION

[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 CQDs / Pt / TpBpy-COF material of this embodiment is completed by the following steps: 1. Preparation of Pt nanoparticles: Add chloroplatinic acid solution, polyvinyl pyrrolidone (PVP), ethylene glycol solution containing sodium hydroxide and ethylene glycol into a three-necked flask, stir and heat under vacuum, and maintain at 180°C for 3 min; cool to room temperature, centrifuge the resulting solution with acetone, and wash three times with n-hexane; finally, the nanoparticles are dispersed in 2 mL DMA. 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 0.2 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 DMA solution containing Pt nanoparticles in step 1 is 2.96 mg / mL. 2. Preparation of CQDs: Add citric acid (CA), diethylenetriamine and deionized water into a beaker, and ultrasonically treat for 30-35 min at an ultrasonic frequency of 35-45 kHz. Transfer the mixture after ultrasonication to a 50 mL autoclave and heat it. After cooling to room temperature, obtain a solid by rotary evaporation. Then, dissolve the solid in ethanol and remove the insoluble precipitate in the solution by centrifugation. Further purify the solution by dialyzing distilled water in a dialysis bag (Mw=1000) for 4 days. Finally, obtain pure CQDs by rotary evaporation and dissolve the pure CQDs in DMA for dispersion. The mass of citric acid (CA) in step 2 is 420 mg; The volume ratio of diethylenetriamine and deionized water in step 2 is 0.683:10; The mixture in step 2 is sealed in an autoclave and heated at 200° C. for 5 h; The pure CQDs described in step 2 were dissolved in 10 mL of N,N-dimethylacetamide (DMA) solution. 3. Preparation of CQDs / Pt@TpBpy-COF composites: N,N-dimethylacetamide solution containing Pt nanoparticles, N,N-dimethylacetamide solution containing CQDs, 5,5-diamino-2,2-bipyridine, and 1,3,5-trialdehyde phloroglucinol were added to a heat-resistant glass tube, and o-dichlorobenzene and DMA were added in sequence. The tube was ultrasonically treated at an ultrasonic frequency of 35 to 45 kHz for 25 to 40 min, and then 6 mol·L -1 The acetic acid solution was cyclically frozen and degassed in liquid nitrogen three times, sealed, heated at 120°C for 72h, filtered and washed with DMA and ethanol several times, and vacuum dried at 80°C to obtain a reddish-brown powder, which is the CQDs / Pt / TpBpy-COF dual-promoter material. The concentration of the DMA solution containing Pt nanoparticles used in step 3 is 2.96 mg / mL; The mass ratio of Pt nanoparticles to TpBpy-COF in step 3 is 0.05:1; The amount of N,N-dimethylacetamide (DMA) solution containing CQDs added in step 3 is 0.3 mL; The mass ratio of CQDs to TpBpy-COF in step 3 is 0.0036:1; The molar ratio of 5,5-diamino-2,2-bipyridine to 1,3,5-trialdehyde phloroglucinol in step 3 is 3:2; The volume ratio of o-dichlorobenzene, DMA and acetic acid in step 3 is 0.5:1.5:0.2; After sealing as described in step 3, heat at 120°C for 72h.

[0010] Example 2: This embodiment differs from Example 1 in that the amount of N,N-dimethylacetamide (DMA) solution containing CQDs added in step 2 is 0.1 mL, the amount of CQDs added is 0.024 mg, and the other steps and parameters are the same as those in Example 1; a CQDs / Pt / TpBpy-COF (volume 0.1 mL) composite material is obtained.

[0011] Example 3: This embodiment is different from Example 1 in that the amount of N,N-dimethylacetamide (DMA) solution containing CQDs added in step 2 is 0.5 mL, the amount of CQDs added is 0.12 mg, and the other steps and parameters are the same as those in Example 1; a CQDs / Pt / TpBpy-COF (volume 0.5 mL) composite material is obtained.

[0012] To verify the beneficial effects of the present invention, the following tests were performed: In order to investigate the photocatalytic water splitting effect of CQDs / Pt / TpBpy-COF material, its visible light photocatalytic decomposition performance was tested according to the following method; the test process is as follows: CQDs / Pt / TpBpy-COF (10 mg) was used as the photocatalyst and distilled water was used as the reaction liquid; under visible light, the photocatalytic water splitting efficiency of Pt / TpBpy-COF alone was low, only 96.0 μmol·h -1 ·g -1 , oxygen production is only 40.6 μmol·h -1 ·g -1 The CQDs / Pt / TpBpy-COF composite material exhibited excellent photocatalytic water splitting performance, with a hydrogen production efficiency of 232.1 μmol·h -1 ·g -1 , oxygen production efficiency is 115.5 μmol·h -1 ·g -1 .

Claims

1. Preparation of a CQDs / Pt / TpBpy-COF composite material, Features The method proceeds as follows:

1. Preparation of CQDs / Pt / TpBpy-COF composites: N,N-dimethylacetamide (DMA) solution containing Pt nanoparticles, 5,5-diamino-2,2-bipyridine, 1,3,5-trialdehyde phloroglucinol, and CQDs were added to a heat-resistant glass tube, and o-dichlorobenzene and DMA were added in sequence. The mixture was ultrasonically treated at an ultrasonic frequency of 35 to 45 kHz for 25 to 40 min, and then 6 mol·L -1 The acetic acid solution was cyclically frozen and degassed in liquid nitrogen three times, sealed, heated at 120°C for 72h, filtered and washed with DMA and ethanol several times, and vacuum dried at 80°C to obtain a reddish-brown powder, which is the CQDs / Pt / TpBpy-COF composite material.

Images