An organic small-molecule assisted enhanced copper nanoparticle photocatalyst, a preparation method and application thereof

Abstract

The application discloses a small molecule loaded copper nanoparticle photocatalyst, and the photocatalyst comprises copper nanoparticles and small molecule coating on the surface of the copper nanoparticles; the small molecule coating is lithocholic acid, dehydrocholic acid, cholic acid or (2-(9H-carbazole-9-yl) ethyl) phosphonic acid; wherein the photocatalyst obtained by coating the copper nanoparticles with lithocholic acid and (2-(9H-carbazole-9-yl) ethyl) phosphonic acid respectively is in a spherical structure, and the size is 10-20 nm; the application utilizes the heat electrons generated on the surface of the copper nanoparticles, and through the small molecule wrapping on the surface of the copper nanoparticles to form a composite, the interaction between the lithocholic acid or 2PACz and the copper nanoparticles can be utilized to improve the hydrogen production effect.

Description

Technical Field

[0001] This invention relates to the field of plasma photocatalytic materials technology, specifically to a method for preparing an organic small molecule-assisted enhanced copper nanoparticle photocatalyst and its application. Background Technology

[0002] The direct production of "zero-carbon" hydrogen using sunlight and water is considered one of the most sustainable energy conversion pathways. Plasma metal nanoparticles exhibit unique light absorption characteristics by exciting surface plasmon resonances and also possess catalytically active surface properties, thus they can be regarded as a novel photocatalytic system for solar-driven catalytic reactions. Copper nanoparticles have become highly promising candidate materials due to their strong surface plasmon resonance absorption in the visible light band of the solar spectrum, and have received widespread attention in recent years. However, the plasma photocatalytic system still faces three major challenges: (1) the short hot electron lifetime (fs–ps) and the severe mismatch between surface proton reduction kinetics (μs–ms) result in most of the energy being dissipated in the form of heat loss; (2) the spatial misalignment between the local electromagnetic field enhancement region and the semiconductor carrier depletion region makes it impossible for the built-in electric field of the Schottky junction to effectively separate the LSPR-induced electrons. - / h + Yes; (3) The Joule heating effect induced by high carrier density causes PNPs to sinter, Cu to oxidize or Ag to etch, and the catalytic activity drops by 1-2 orders of magnitude within a few hours. The chemical stability of Cu nanoparticles is the main challenge for their use in photocatalytic hydrogen generation. Therefore, a convenient method should be considered to obtain Cu nanoparticles with high stability for hydrogen generation. Cholic acid has a rigid steroidal framework structure and good chemical stability. It can participate in photocatalytic reactions under mild conditions such as visible light irradiation, room temperature, neutral or weakly acidic conditions, and is not prone to side reactions or framework degradation. In addition, 2PACz is often used as a hole-selective contact layer in photovoltaic devices and has phosphate hydrophilic groups, which is beneficial for the separation of electrons and holes.

[0003] Currently reported noble metal catalysts based on the LSPR effect are expensive and their stability needs to be improved. Therefore, this invention aims to find a low-cost, simple-to-prepare, and stable photocatalyst. Summary of the Invention

[0004] The purpose of this invention is to provide a small molecule supported copper nanoparticle photocatalyst; the second purpose of this invention is to provide a method for preparing the small molecule supported copper nanoparticle photocatalyst; and the third purpose of this invention is to provide an application of the small molecule supported copper nanoparticle photocatalyst.

[0005] Technical solution: This invention provides a small molecule supported copper nanoparticle photocatalyst, wherein the photocatalyst comprises copper nanoparticles and a small molecule coating on the surface of the copper nanoparticles; the small molecule coating is lithocholic acid (LCA), dehydrocholic acid (DHCA), cholic acid (CA), or (2-(9H-carbazole-9-yl)ethyl)phosphonic acid (2PACz); wherein the photocatalyst obtained by coating copper nanoparticles with lithocholic acid and (2-(9H-carbazole-9-yl)ethyl)phosphonic acid respectively has a spherical structure with a size of 10~20 nm.

[0006] Preferably, the photocatalyst contains 13.0~53.0 mol% lithocholic acid, with the remainder being copper nanoparticles.

[0007] Preferably, the content of (2-(9H-carbazole-9-yl)ethyl)phosphonic acid in the photocatalyst is 4.0~60.0 wt%, and the remainder is copper nanoparticle components.

[0008] This invention also provides a method for preparing a small molecule supported copper nanoparticle photocatalyst, comprising the following steps:

[0009] (1) Dissolve copper acetate in deionized water to obtain a copper acetate solution;

[0010] (2) Dissolve the small molecule coating in ethanol to obtain a small molecule coating solution;

[0011] (3) Using deionized water as the reaction substrate, lactic acid as a sacrificial agent, and polyethylene glycol as a dispersant, a mixed solution is obtained;

[0012] (4) Add the small molecule coating solution and copper acetate solution to the mixed solution in sequence, mix well, remove oxygen with nitrogen, react under light, and then obtain the solid product by centrifugation.

[0013] (5) The solid product is washed and vacuum dried to obtain a photocatalyst.

[0014] Preferably, in step (2), the small molecule coating material is lithocholic acid, and the amount of material fed is 100~400 μg.

[0015] Preferably, in step (2), the small molecule coating is (2-(9H-carbazole-9-yl)ethyl)phosphonic acid, and the amount of feed is 5~50 μg.

[0016] This invention also provides the application of a small molecule supported copper nanoparticle photocatalyst in photocatalytic water splitting to produce hydrogen, wherein the photocatalyst can produce hydrogen under simulated sunlight irradiation.

[0017] The design principle of this invention is as follows: Small molecules are simultaneously encapsulated on the surface of copper nanoparticles using an in-situ growth method. The synergistic effect between the small molecules and the copper nanoparticles enhances the photocatalytic hydrogen production performance. Lithocholic acid (possessing a steroidal framework structure with multiple chiral centers and hydroxyl functional groups) and 2PACz (containing an electron-rich carbazole host and ethylphosphonic acid) are selected as small molecule supports. Under simulated sunlight irradiation, the small molecules promote the separation and transport of photogenerated carriers through their unique electronic structure. Simultaneously, the surface plasmon resonance effect broadens the photoresponse range, ultimately yielding a low-cost, easy-to-prepare, and significantly more stable copper-based composite photocatalyst. This overcomes the problems of high cost of traditional noble metal catalysts and the easy deactivation of pure copper nanoparticles.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] I. This invention utilizes the hot electrons generated on the surface of copper nanoparticles to form a complex by encapsulating small molecules on the surface of the copper nanoparticles. The interaction between lithocholic acid or 2PACz and the copper nanoparticles can then enhance hydrogen production. Specifically, the hydrogen production rate of the Cu / LCA complex is 21.2 mmol / g. -1 h -1 It is pure copper (9.3 mmol / g). -1 h -1 The hydrogen production rate of the Cu / 2PACz complex was 47.2 mmol / g, which is 2.27 times that of the original complex. -1 h -1 It is pure copper (33 mmol / g) -1 h -1 1.43 times that of ).

[0020] Second, the preparation method of the present invention can delay the oxidation process of copper nanoparticles and improve the stability of photocatalysts. On the other hand, the introduction of small molecule lithocholic acid or 2PACz can broaden the photoresponse range, which can open up new opportunities for the design of new copper-based materials and catalysts. It has broad application prospects in wastewater treatment, new energy hydrogen production, composite materials, batteries and other fields. Attached Figure Description

[0021] Figure 1 The images show the morphology of the copper nanoparticles prepared in this invention, where a is a scanning electron microscope (SEM) image and a transmission electron microscope (TEM) image; b is an EDS distribution map of the copper nanoparticles.

[0022] Figure 2 The images show the UV absorption spectrum of copper nanoparticles and the XRD patterns of photocatalysts with different contents of LCA, where a is the UV absorption spectrum of copper nanoparticles and b is the XRD pattern of composites with different contents of LCA.

[0023] Figure 3 The graphs show the hydrogen production effects of photocatalysts with different LCA contents, where a represents the hydrogen production of LCA complexes with different contents over 5 hours; and b represents the hydrogen production rate of LCA complexes with different contents.

[0024] Figure 4 The graphs show the hydrogen production effects of photocatalysts with different contents of 2PACz, where a is the hydrogen production of complexes with different contents of 2PACz over 4 hours; and b is the hydrogen production rate of complexes with different contents of LCA. Detailed Implementation

[0025] Example 1

[0026] In-situ growth method was used to prepare Cu / LCA catalyst and its photocatalytic hydrogen production performance was tested: 9.1 mg Cu(OAc)₂ was dissolved in 25 ml of deionized water to obtain 2 mmol L⁻¹ -1 A Cu(OAc)₂ solution was prepared by dissolving 5 mg of lithocholic acid in 5 ml of ethanol to obtain a 1 g / L lithocholic acid solution. In a reactor, 50 ml of deionized water was added as the substrate, 10 ml of lactic acid as a sacrificial agent, 1 ml of PEG as a dispersant, 1 ml of Cu(OAc)₂ solution, and 300 μl of LCA to achieve an LCA concentration of 26 mol%. After thorough mixing, nitrogen gas was introduced into the system for 30 minutes, followed by irradiation under a xenon lamp. Hydrogen production was measured hourly. The solution was centrifuged to obtain a solid product, which was then washed, vacuum dried, and used for XRD and other tests.

[0027] Example 2

[0028] The preparation steps were exactly the same as in Example 1, except that the LCA content was 13 mol%, 40 mol%, and 53 mol, respectively.

[0029] Example 3

[0030] In-situ growth method was used to prepare Cu / DHCA catalyst and its photocatalytic hydrogen production performance was tested: 9.1 mg Cu(OAc)₂ was dissolved in 25 ml of deionized water to obtain 2 mmol L⁻¹ -1A Cu(OAc)₂ solution was prepared by dissolving 5 mg of DHCA in 5 ml of ethanol to obtain a 1 g / L DHCA solution. In a reactor, 50 ml of deionized water was added as the substrate, 10 ml of lactic acid as a sacrificial agent, 1 ml of PEG as a dispersant, 1 ml of Cu(OAc)₂ solution, and 300 μl of DHCA. After stirring the solution thoroughly, nitrogen gas was introduced into the system for 30 minutes, and the system was irradiated under a xenon lamp. Hydrogen production performance was tested hourly. After centrifugation, a solid product was obtained. The solid product was washed and vacuum dried to obtain a solid photocatalyst.

[0031] Example 4

[0032] In-situ growth method was used to prepare Cu / CA catalyst and its photocatalytic hydrogen production performance was tested: 9.1 mg Cu(OAc)₂ was dissolved in 25 ml of deionized water to obtain 2 mmol L⁻¹ -1 A Cu(OAc)₂ solution was prepared by dissolving 5 mg of CA in 5 ml of ethanol to obtain a 1 g / L CA solution. In a reactor, 50 ml of deionized water was added as the substrate, 10 ml of lactic acid as a sacrificial agent, 1 ml of PEG as a dispersant, 1 ml of Cu(OAc)₂ solution, and 300 μl of CA. After stirring the solution thoroughly, nitrogen gas was introduced into the system for 30 minutes, and the system was irradiated under a xenon lamp. Hydrogen production performance was tested hourly. The solution was centrifuged to obtain a solid product, which was then washed and vacuum dried to obtain a solid photocatalyst.

[0033] Example 5

[0034] In-situ growth method was used to prepare Cu / 2PACz catalyst and its photocatalytic hydrogen production performance was tested: 9.1 mg Cu(OAc)2 was dissolved in 25 ml of deionized water to obtain 2 mmol L -1 A Cu(OAc)₂ solution was prepared by dissolving 5 mg of 2PACz in 5 ml of ethanol to obtain a 1 g / L 2PACz solution. In a reactor, 50 ml of deionized water was added as the substrate, 10 ml of lactic acid as a sacrificial agent, 1 ml of PEG as a dispersant, 1 ml of Cu(OAc)₂ solution, and 15 μl of 2PACz, resulting in a 2PACz concentration of 12 wt%. After thorough mixing, nitrogen gas was introduced into the system for 30 minutes, followed by irradiation under a xenon lamp. Hydrogen production performance was tested hourly. The solution was centrifuged to obtain a solid product, which was then washed, vacuum dried, and used for XRD and other tests.

[0035] Example 6

[0036] The preparation steps were exactly the same as in Example 1, except that the 2PACz content was 4 wt%, 8 wt%, and 16 wt%, respectively.

[0037] Comparative Example 1

[0038] In-situ growth method was used to prepare copper nanoparticle catalysts and to test their photocatalytic hydrogen production performance: 9.1 mg Cu(OAc)₂ was dissolved in 25 ml of deionized water to obtain 2 mmol L⁻¹ -1 A Cu(OAc)₂ solution was prepared by adding 50 ml of deionized water as the reaction substrate, 10 ml of lactic acid as the sacrificial agent, 1 ml of PEG as the dispersant, and 1 ml of 2 mmol L⁻¹ to the reactor. -1 A Cu(OAc)₂ solution was stirred thoroughly, then nitrogen gas was introduced into the system for 30 minutes. The system was then irradiated under a xenon lamp, and hydrogen production performance was tested hourly. The solution was then dropped onto a silicon wafer, dried, and scanned using SEM. The results are as follows. Figure 1 As shown in Figure a, copper nanoparticles partially aggregate. A solution is dropped onto a copper mesh for TEM testing, as shown... Figure 1 As shown in the illustration in Figure a, the particle size of the copper nanoparticles is approximately 10-15 nm. Figure 1 The 'b' in the figure corresponds to the EDS of copper nanoparticles, proving that the catalyst contains copper. After centrifugation, a solid product was obtained. The solid product was then washed and vacuum dried to prepare the solid copper nanoparticle catalyst.

[0039] like Figure 2 The image shows the XRD patterns of photocatalysts with different contents of LCA prepared in Examples 1 and 2. Figure 2 In the diagram, 'a' represents the ultraviolet absorption spectrum of copper nanoparticles, and the absorption peak around 600 nm corresponds to the absorption of copper nanoparticles. Figure 2 Figure b shows the XRD patterns of LCA and copper nanoparticle composites with different contents. 44.2°, 51.4°, and 75° correspond to the (111), (200), and (220) crystal planes of copper, respectively, while approximately 17° corresponds to the diffraction peak of LCA. Furthermore, the LCA peak gradually increases with increasing LCA content, demonstrating the successful composite of LCA and copper nanoparticles.

[0040] like Figure 3 As shown, the hydrogen production effects of LCA photocatalysts with different contents prepared in Examples 1 and 2, and the Cu NPs catalyst prepared in Comparative Example 1 are illustrated. Figure 3 As shown in a, the hydrogen production of pure copper over five hours is 46.6 mmol g. -1 When the LCA content is 26 mol%, the hydrogen production reaches 106.1 mmol g. -1 ;like Figure 3As shown in b, the hydrogen production rate of pure copper over five hours is 9.3 mmol g. -1 h -1 When the LCA content is 26 mol%, the hydrogen production rate is 21.2 mmol g. -1 h -1 .

[0041] like Figure 4 As shown, the hydrogen production effects of the 2PACz photocatalysts with different contents prepared in Examples 5 and 6, and the Cu NPs catalyst prepared in Comparative Example 1 are illustrated in the figure. Figure 4 As shown in a, the hydrogen production of pure copper over four hours was 132.0 mmol g. -1 When the 2PACz content is 12 wt%, the hydrogen production is 188.8 mmol g. -1 ;like Figure 4 As shown in b, the hydrogen production rate of pure copper over four hours is 33.0 mmol g. -1 h -1 When the 2PACz content was 12 wt%, the hydrogen production rate was 47.2 mmol g. -1 h -1 .

Claims

1. A small-molecule supported copper nanoparticle photocatalyst, characterized in that, The photocatalyst comprises copper nanoparticles and small molecule coatings on the surface of the copper nanoparticles; the small molecule coatings are lithocholic acid, dehydrocholic acid, cholic acid, or (2-(9H-carbazole-9-yl)ethyl)phosphonic acid; wherein, the photocatalysts obtained by coating copper nanoparticles with lithocholic acid and (2-(9H-carbazole-9-yl)ethyl)phosphonic acid respectively have a spherical structure with a size of 10~20 nm.

2. The small molecule supported copper nanoparticle photocatalyst according to claim 1, characterized in that, The photocatalyst contains 13.0~53.0 mol% lithocholic acid, with the remainder being copper nanoparticles.

3. The small molecule supported copper nanoparticle photocatalyst according to claim 1, characterized in that, The photocatalyst contains 4.0~60.0 wt% (2-(9H-carbazole-9-yl)ethyl)phosphonic acid, with the remainder being copper nanoparticles.

4. The preparation method of the small molecule supported copper nanoparticle photocatalyst as described in claim 1, characterized in that, Includes the following steps: (1) Dissolve copper acetate in deionized water to obtain a copper acetate solution; (2) Dissolve the small molecule coating in ethanol to obtain a small molecule coating solution; (3) Using deionized water as the reaction substrate, lactic acid as a sacrificial agent, and polyethylene glycol as a dispersant, a mixed solution is obtained; (4) Add the small molecule coating solution and copper acetate solution to the mixed solution in sequence, mix well, remove oxygen with nitrogen, react under light, and then obtain the solid product by centrifugation. (5) The solid product is washed and vacuum dried to obtain a photocatalyst.

5. The method for preparing the small molecule supported copper nanoparticle photocatalyst according to claim 4, characterized in that, In step (2), the small molecule coating material is lithocholic acid, and the amount of material added is 100~400 μg.

6. The method for preparing the small molecule supported copper nanoparticle photocatalyst according to claim 4, characterized in that, In step (2), the small molecule coating is (2-(9H-carbazole-9-yl)ethyl)phosphonic acid, and the amount of feed is 5~50 μg.

7. The application of the small molecule supported copper nanoparticle photocatalyst as described in claim 1 in photocatalytic water splitting for hydrogen production, characterized in that, The photocatalyst described above can produce hydrogen gas under simulated sunlight irradiation.

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