Method for preparing solar energy conversion material through carbon dot in-situ induced phenolic aldehyde reaction

Abstract

The invention discloses a method for preparing a solar energy conversion material through carbon dot in-situ induction of phenolic resin reaction, and the method utilizes carbon dot induction to increase the number of quinonoid structure receptors in phenolic resin, and is more beneficial to photo-generated charge separation and transfer; a-COOH group on the surface of the carbon dot is used as a photo-generated hole reaction site, and a catalytic reaction path from superoxide carboxylic acid to hydrogen peroxide is opened; the carbon dots are combined, so that the composite resin material has a wider wavelength absorption range, has higher light capture capability and shows efficient photo-thermal interface water evaporation performance.

Description

Technical Field

[0001] The present invention belongs to the field of new materials, and particularly relates to a method for preparing a solar energy conversion material by in-situ inducing the reaction of phenolic resin with carbon dots. Background Art

[0002] As a renewable energy source, solar energy is ubiquitous, does not produce pollutants during use, and is environmentally friendly. Therefore, people have long hoped to efficiently convert it into thermal energy, electrical energy, and chemical energy for use, reducing the dependence on fossil energy. Solar energy conversion materials are the material basis for maximizing the collection and absorption of solar radiation energy and converting it into different forms of energy, determining the conversion efficiency and cost of solar energy. Phenolic resin is an emerging photocatalyst, which is prepared from inexpensive and readily available monomers. By creating an electron donor-acceptor molecular structure, it can achieve high-efficiency solar-to-chemical energy conversion. However, some inherent properties of phenolic resin hinder the further improvement of its photocatalytic activity, such as poor charge separation ability and low specific surface area. To address these challenges, it is necessary to regulate the charge separation and mass transfer properties of phenolic resin. In particular, formaldehyde, as a reactant for synthesizing phenolic resin, is a Class 1 carcinogen, volatile, and poses a serious hazard to human health. Therefore, there is an urgent need to seek non-toxic or low-toxic aldehyde substances to replace formaldehyde for the development and preparation of functional phenolic resins.

[0003] As a zero-dimensional carbon nanomaterial with semiconductor properties, carbon dots (CDs) have broad application prospects in the fields of bioimaging, ion detection, photothermal therapy, pollutant degradation, photocatalysis, and water evaporation due to their good biocompatibility, non-toxicity, and easy functionalization. CDs are a special "core-shell" nanostructure, with an internal core of sp 2 hybridized crystalline carbon and a surface shell composed of a large number of oxygen-containing functional groups such as -COOH and -OH. This surface structure endows it with various functions and applications. CDs can combine with various organic and inorganic materials to form functional hybrid or composite materials, achieving the purpose of reducing costs and improving performance. As a component of solar energy conversion materials, CDs can not only improve the capture of sunlight, but also promote the separation and transfer of photo-generated charges, creating more catalytic active sites, thus effectively enhancing the performance of solar energy conversion materials. In addition, during organic polymerization, addition and other reaction processes, adding CDs can also act as a catalyst to promote the formation of functional polymers and obtain higher yields.

[0004] Microwaves can penetrate deep into the interior of substances. Instead of relying on the thermal conduction of the substances themselves, the entire heating process can be completed in only one-tenth to one-hundredth of the time required by conventional methods. Therefore, microwave synthetic material technology usually has advantages such as fast heating speed, high thermal energy utilization rate, energy saving, and being conducive to improving working conditions. Currently, the hydrothermal synthesis method is mainly used to synthesize photocatalytically active phenolic resins. In order to create a quinone structure in the resin, this method often requires heating at temperatures above 240 °C for dozens of hours, not only with a low yield, but also with potential safety hazards due to long-term high temperature and high pressure, which limits its large-scale preparation and production. Summary of the Invention

[0005] A method for preparing a solar energy conversion material by in-situ inducing a phenolic resin reaction with carbon dots, comprising the following steps:

[0006] Step 1: Add A mol of phloroglucinol to a mixture of B L of ammonia water and B L of deionized water, stir at a speed of 200 - 300 rmp for more than 30 min, and then ultrasonically disperse for more than 20 min until the added phloroglucinol is completely dissolved; wherein, the molar concentration of ammonia water is 13.3 mol / L, and A:B is 3 - 4.5;

[0007] Step 2: Add C g of CDs powder to D L of glutaraldehyde solution, stir and ultrasonically disperse at a speed of 300 rmp for more than 15 min each until the CDs are completely and evenly dispersed; wherein, the molar concentration of glutaraldehyde is 5.3 mol / L, the ratio of C to A in Step 1 is 10 - 19, and the ratio of A in Step 1 to D is 4.3 - 10.7;

[0008] Step 3: Mix the solutions obtained in Step 1 and Step 2, stir at a speed of 200 - 300 rmp for more than 10 min to allow phloroglucinol, glutaraldehyde, and CDs to be fully adsorbed and in contact;

[0009] Step 4: Pour the mixed solution obtained in Step 3 into a ceramic crucible, microwave in a microwave oven with a power of 600 - 700 W for 8 - 10 min to obtain a brownish-black lump; grind the obtained brownish-black lump into powder, wash the powder three times with water and ethanol in sequence, and after drying at 50 - 60 °C, obtain the solar energy conversion material CDs-PG powder.

[0010] The CDs powder is obtained by selectively etching coal tar pitch with formic acid and hydrogen peroxide according to the method for preparing multi-color luminescence tunable carbon dots using coal tar pitch disclosed in Patent ZL201610534465.4.

[0011] The present invention has the following beneficial effects:

[0012] Under the induction of carbon dots, the increase in the number of quinone-type structure receptors in phenolic resin helps the separation and transfer of photo-generated charges; at the same time, the -COOH groups on the surface of carbon dots serve as reaction sites for photo-generated holes, opening the catalytic reaction path from superoxocarboxylic acid to hydrogen peroxide. Due to the incorporation of carbon dots, the composite resin material has a wider wavelength absorption range, stronger light trapping ability, and exhibits efficient photothermal interfacial water evaporation performance. Therefore, the composite resin has great application potential as a solar energy conversion material in the fields of seawater desalination, sewage purification, and photocatalysis. Description of the Drawings

[0013] Figure 1 SEM image of CDs-PG prepared in the present invention.

[0014] Figure 2 High-resolution X-ray photoelectron spectroscopy O1s diagram of CDs-PG prepared in the present invention and resin PG synthesized without the presence of CDs under other unchanged conditions.

[0015] Figure 3 Structural diagram of CDs-PG prepared in the present invention.

[0016] Figure 4 Solid state 13 13C nuclear magnetic resonance spectrum of CDs-PG prepared in the present invention.

[0017] Figure 5 Solid state 13 13C nuclear magnetic resonance spectrum of PG without CDs.

[0018] Figure 6 UV-visible absorption spectra of CDs-PG and PG prepared in the present invention.

[0019] Figure 7 Photoluminescence spectrum (PL) diagrams of CDs-PG and PG prepared in the present invention.

[0020] Figure 8 Electrochemical impedance spectra of CDs-PG and PG prepared in the present invention.

[0021] Figure 9 Transient photocurrent response diagrams of CDs-PG and PG prepared in the present invention.

[0022] Figure 10 Photocatalytic H2O2 production diagrams of CDs-PG and PG prepared in the present invention.

[0023] Figure 11 Water evaporation performance measured by floating CDs-PG and PG prepared in the present invention on the surface of melamine sponge and then simulating sunlight conditions. Detailed Description of the Invention

[0024] Method for preparing solar energy conversion material by in-situ induction of carbon dots in phenolic resin reaction, comprising the following steps:

[0025] Step 1: Add A mol of phloroglucinol to a mixture of B L of ammonia water and B L of deionized water, stir at a rotation speed of 200 - 300 rmp for more than 30 min, and then ultrasonically disperse for more than 20 min until the added phloroglucinol is completely dissolved; wherein, the molar concentration of ammonia water is 13.3 mol / L, and A:B is 3 - 4.5;

[0026] Step 2: Add C g of CDs powder to D L of glutaraldehyde solution, stir and ultrasonically disperse at a rotation speed of 300 rmp for more than 15 min each until the CDs are completely and uniformly dispersed; wherein, the molar concentration of glutaraldehyde is 5.3 mol / L, the ratio of C to A in Step 1 is 10 - 19, and the ratio of A in Step 1 to D is 4.3 - 10.7;

[0027] Step 3: Mix the solutions obtained in Step 1 and Step 2, stir at a rotation speed of 200 - 300 rmp for more than 10 min to allow phloroglucinol, glutaraldehyde, and CDs to be fully adsorbed and in contact;

[0028] Step 4: Pour the mixed solution obtained in Step 3 into a ceramic crucible, microwave in a microwave oven with a power of 600 - 700 W for 8 - 10 min to obtain a brownish - black lump; grind the obtained brownish - black lump into powder, wash the powder three times with water and ethanol in sequence, and after drying at 50 - 60 °C, obtain the solar energy conversion material CDs - PG powder.

[0029] The CDs powder is obtained by selectively etching coal tar pitch with formic acid and hydrogen peroxide according to the method for preparing multi - color luminescence - tunable carbon dots using coal tar pitch disclosed in Patent ZL201610534465.4.

[0030] Example 1

[0031] Method for preparing solar energy conversion material by in - situ induction of carbon dots in phenolic resin reaction, comprising the following steps:

[0032] Step 1: Add 1 mol of phloroglucinol to a mixture of 0.3 L of ammonia water with a molar concentration of 13.3 mol / L and 0.3 L of deionized water, stir at a rotation speed of 250 rmp for 50 min, and then ultrasonically disperse for 30 min;

[0033] Step 2: Add 15 g of CDs powder to 0.2 L of glutaraldehyde solution with a molar concentration of 5.3 mol / L, stir and ultrasonically disperse at a rotation speed of 300 rmp for 25 min each;

[0034] Step 3 Mix the solutions obtained in Step 1 and Step 2, and stir at a speed of 250 rmp for 20 min to allow phloroglucinol, glutaraldehyde, and CDs to be fully adsorbed and in contact.

[0035] Step 4 Pour the mixed solution obtained in Step 3 into a ceramic crucible, and microwave it in a microwave oven with a power of 650 W for 10 min to obtain a brownish-black lump; grind the obtained brownish-black lump into powder, wash the powder three times with water and ethanol in sequence, and after drying at 55 °C, obtain the solar energy conversion material CDs-PG powder.

[0036] Characterize the obtained CDs-PG powder. Figure 1 is the SEM image of the prepared CDs-PG powder. It can be seen from the figure that the material is granular and the size distribution is about 1.0 μm. Figure 2 is the high-resolution X-ray photoelectron spectrum O1s of the prepared CDs-PG and the resin PG synthesized without changing other conditions in the absence of CDs. Figure 3 is the structural diagram of the prepared CDs-PG. It can be seen from the figure that the C=O / C-O ratio (0.54) of CDs-PG is higher than that of PG (0.31). Therefore, the introduction of CDs affects the conversion between phloroglucinol and quinone, increasing the number of quinone units and enhancing the photocatalytic performance. Figure 4 and Figure 5 are the solid-state 13 13C nuclear magnetic resonance spectra of the CDs-PG prepared in this invention and PG without CDs respectively, Figure 5 showing that according to the integrated peak area of the fitting, the content of quinone carbon (C=O) in the 13C NMR spectrum of CDs-PG is 1.8 times that of PG, indicating that the introduction of CDs increases the number of quinone units, which is beneficial to the separation and transfer of photo-generated charges. 13 is the ultraviolet-visible absorption spectra of the prepared CDs-PG and PG. It can be seen from the figure that compared with the pure PG resin, the CDs-PG resin shows significantly stronger light absorption, reflecting its better ability to capture sunlight. Figure 6 is the photoluminescence spectrum (PL) of the prepared CDs-PG and PG. It can be seen from the figure that the photoluminescence (PL) intensity of CDs-PG is significantly lower than that of the PG resin, indicating that the increase of more quinone units in the resin leads to a decrease in radiative recombination and more efficient separation of photo-generated carriers. Figure 7 is the electrochemical impedance spectra of the prepared CDs-PG and PG. It can be seen from the figure that the semicircle of CDs-PG is smaller, indicating that the interfacial resistance is smaller, which is beneficial to the migration of photo-generated charges. Figure 8 Figure 9 ​Transient photocurrent response diagrams of the prepared CDs-PG and PG are shown. It can be seen from the figures that under light illumination, CDs-PG exhibits a stronger photocurrent response than PG, indicating that CDs-PG has a higher charge separation ability during the photocatalytic process. Figure 10 Photocatalytic H2O2 production diagrams of the prepared CDs-PG and PG are shown. It can be seen from the figures that both CDs-PG and PG exhibit photocatalytic activity for generating H2O2, and it increases steadily with the increase of irradiation time. Compared with PG, the H2O2 production on CDs-PG has reached nearly a 5-fold increase, indicating that the in-situ addition of CDs during the material synthesis process can promote the production of H2O2. Figure 11 The water evaporation performance measured under simulated sunlight conditions is shown for the prepared CDs-PG and PG loaded on melamine sponges and shaped by wrapping with polyvinyl alcohol (PVA) hydrogels, then floating on the surface of brine. It can be seen from the figure that the evaporation rate of CDs-PG is much higher than that of PG, and its evaporation rate reaches 4.23 kg·m -2 ·h -1 , exceeding that of the reported similar solar evaporators.

Claims

1. A method for preparing solar energy conversion materials by in-situ carbon dot-induced phenolic resin reaction, characterized in that: Use the following steps: Step 1: Add A mol of phloroglucinol to a mixture of BL ammonia water and BL deionized water, stir at a speed of 200-300 rpm for more than 30 minutes, and then ultrasonically disperse for more than 20 minutes until the added phloroglucinol is completely dissolved; wherein the molar concentration of the ammonia water is 13.3 mol / L, and A:B is 3-4.5; Step 2: adding C g CDs powder to DL glutaraldehyde solution, stirring at a speed of 300 rpm and ultrasonic dispersion for more than 15 minutes each, until CDs are completely dispersed, wherein the molar concentration of glutaraldehyde is 5.3 mol / L, the ratio of C to A in step 1 is 10-19, and the ratio of A to D in step 1 is 4.3-10.7; Step 3: Mix the solutions obtained in step 1 and step 2, and stir at a speed of 200-300 rpm for more than 10 minutes to allow phloroglucinol, glutaraldehyde and CDs to be fully adsorbed and contacted; Step 4: Pour the mixed solution obtained in step 3 into a ceramic crucible, microwave it in a microwave oven with a power of 600 to 700 W for 8 to 10 minutes to obtain brown agglomerates; grind the obtained brown agglomerates into powder, wash the powder three times with water and ethanol in sequence, and after drying at 50 to 60° C., obtain the solar energy conversion material CDs-PG powder.

2. The method for preparing solar energy conversion materials by in-situ induction of phenolic resin reaction by carbon dots according to claim 1, characterized in that: The CDs powder is obtained by selectively etching coal tar pitch with formic acid and hydrogen peroxide according to the method for preparing multi-color luminescent adjustable carbon dots using coal tar pitch disclosed in Patent ZL201610534465.4.

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