A carbon dioxide reduction photocatalyst and its preparation method and application

Abstract

The present invention relates to a carbon dioxide reduction photocatalyst, its preparation method, and application. The catalyst comprises PCN-224(Cu) and BiVO4 nanosheets supported thereon. The preparation method comprises the following steps: uniformly dispersing BiVO4 in N,N-dimethylformamide, sequentially adding copper tetrakis-(4-carboxyphenyl)porphyrin, ZrCl4, and benzoic acid, and reacting to produce the carbon dioxide reduction photocatalyst. Compared with the prior art, the present invention synthesizes a novel rod-shaped PCN-224(Cu)@BiVO4 composite photocatalyst for photocatalytic CO2 reduction for the first time through a convenient solvothermal method. The prepared photocatalyst has high catalytic activity, selectivity, and stability, and has potential application value in solar photocatalytic CO2 conversion.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis technology, and in particular to a carbon dioxide reduction photocatalyst and a preparation method and application thereof. Background Art

[0002] In recent years, with the rapid development of global industrialization and the increasing use of fossil fuels, CO2 emissions have been increasing, posing a huge threat to the environment and climate. Using photocatalytic technology to convert CO2 into usable hydrocarbon fuels (such as CO, CH4, CH3OH, and C2H5OH) is an effective solution. The core of photocatalytic technology is the photocatalyst. However, traditional carbon dioxide photoreduction catalysts (such as metal oxides, metal sulfides, graphite-phase carbon nitride, etc.) still have problems such as low solar energy utilization, low catalytic efficiency, and poor stability. Therefore, the development of new and efficient photocatalysts still faces huge challenges.

[0003] Metal-organic frameworks (MOFs) are porous inorganic-organic hybrid materials composed of metal nodes (metal ions or metal clusters) connected to organic ligands. MOFs have a large specific surface area, high porosity, and tunable composition and pore structure, and have attracted widespread attention in the field of photocatalytic reduction of carbon dioxide in recent years. As a member of MOFs, PCN-224(Cu) is a metal-organic framework composed of copper porphyrin ligands and six connected Zr6 clusters. It has a band gap of approximately 1.7 eV and can effectively absorb visible light. In addition, the abundant nitrogen content of its framework facilitates its adsorption of carbon dioxide. Wang et al. (L.Wang, P.Jin, J.Huang, H.She, Q.Wang, ACSSustainable Chem.Eng.2019, 7, 15660-15670) used a solvothermal method to prepare cubic PCN-224(Cu) and applied it for the first time to the photocatalytic reduction of carbon dioxide. The results showed that PCN-224(Cu) can reduce CO2 to CO under visible light, but the activity of single PCN-224(Cu) is very low. Summary of the Invention

[0004] The purpose of the present invention is to provide a carbon dioxide reduction photocatalyst and its preparation method and application, which has high activity and selectivity for carbon dioxide photoreduction reaction and good stability.

[0005] The purpose of the present invention can be achieved through the following technical solution: A carbon dioxide reduction photocatalyst includes PCN-224 (Cu) and BiVO4 nanosheets supported thereon.

[0006] Preferably, the PCN-224(Cu) is in a rod shape, and the mass percentage of BiVO4 in the carbon dioxide reduction photocatalyst is 5%-20%.

[0007] Further preferably, the mass percentage of BiVO4 in the carbon dioxide reduction photocatalyst is 15%.

[0008] The catalyst is a PCN-224(Cu)@BiVO4 composite visible light catalyst, which is composed of PCN-224(Cu) and BiVO4. The BiVO4 is in the form of nanosheets and is evenly distributed on the surface of the rod-shaped PCN-224(Cu).

[0009] A method for preparing the above-mentioned carbon dioxide reduction photocatalyst includes the following steps: uniformly dispersing BiVO4 in N,N-dimethylformamide, sequentially adding tetrakis-(4-carboxyphenyl)porphyrin copper, ZrCl4 and benzoic acid, and reacting to obtain the carbon dioxide reduction photocatalyst.

[0010] Preferably, the reaction temperature is 110-130° C., and the reaction time is 40-50 h.

[0011] Preferably, the preparation method of BiVO4 comprises the following steps:

[0012] (1) Dissolve Bi(NO3)3·5H2O in HNO3 solution to obtain solution A, and add NH4VO3 to deionized water to obtain solution B;

[0013] (2) Add solution A dropwise to solution B under stirring, add a certain amount of sodium dodecylbenzenesulfonate (SDBS), and continue stirring;

[0014] (3) adding alkaline solution to adjust the pH of the solution;

[0015] (4) Transfer the solution to a high-pressure reactor and react at 160-200°C for 3-12 hours;

[0016] (5) The solid product is centrifuged, washed, and dried to obtain flaky BiVO4.

[0017] Further preferably, the molar ratio of Bi(NO3)3·5H2O, NH4VO3 and sodium dodecylbenzenesulfonate is 1:1:0.2-0.4.

[0018] Further preferably, the alkaline solution includes NaOH, KOH, and Na2CO3.

[0019] Further preferably, the step is to adjust the pH value of the solution to 7.

[0020] An application of the carbon dioxide reduction photocatalyst is to use the catalyst for photocatalytic reduction of carbon dioxide.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The composite photocatalyst prepared by the present invention has a close contact structure of nanosheets / nanorods, which is more conducive to the migration of photogenerated charges at the interface;

[0023] 2. The composite photocatalyst prepared by the present invention is an S-type heterojunction, which is not only conducive to the separation of photogenerated electrons and holes, but also maintains a high redox capacity of the photogenerated charges;

[0024] 3. The PCN-224(Cu)@BiVO4 visible light photocatalyst prepared by the present invention can highly selectively reduce CO2 to CO in the absence of any sacrificial agent or photosensitizer, and has potential application value in the field of solar energy conversion.

[0025] 4. This paper synthesizes a novel rod-shaped PCN-224(Cu)@BiVO4 composite photocatalyst for the first time through a convenient solvothermal method and uses it for photocatalytic CO2 reduction. The prepared photocatalyst has high catalytic activity, selectivity and stability, and has potential application value in solar photocatalytic CO2 conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The XRD spectra of the composites obtained in Examples 1-4, Comparative Example 1 and Comparative Example 2;

[0027] Figure 2 The scanning electron microscope, transmission electron microscope and elemental surface scan images of the composite photocatalyst obtained in Example 1 are shown;

[0028] Figure 3 The performance diagram of photocatalytic reduction of CO2 of the catalysts obtained in Examples 1-4 and Comparative Example;

[0029] Figure 4 This is a photocatalytic cycle performance diagram of the catalyst obtained in Example 1. DETAILED DESCRIPTION

[0030] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0031] Example 1

[0032] A method for preparing a carbon dioxide reduction photocatalyst comprises the following steps:

[0033] A. Preparation of BiVO4

[0034] (1) Dissolve 2.4463 g Bi(NO3)3·5H2O in 10 mL 4.0 mol·L -1 Solution A was obtained by adding HNO3 solution.

[0035] (2) Add 0.5805 g of NH4VO3 to 30 mL of deionized water to obtain solution B.

[0036] (3) A was added dropwise to B under stirring, and 0.4989 g of SDBS was added, and stirring was continued for 0.5 h.

[0037] (4) Using 2.0 mol·L -1 Adjust the pH value of the solution to about 7 with NaOH solution.

[0038] (5) The solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 160 °C for 6 h.

[0039] (6) The solid product was centrifuged, washed with water, and dried at 60°C for 10 h to obtain flaky BiVO4. B. Preparation of PCN-224(Cu)@BiVO4

[0040] (1) 0.0106 g of BiVO4 was dispersed in 16 mL of DMF.

[0041] (2) 0.1023 g CuTCPP, 0.1605 g ZrCl4 and 5.4019 g benzoic acid were added to the above solution in sequence and ultrasonicated for 20 min.

[0042] (3) The above solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 120°C for 48 hours.

[0043] (4) The obtained solid product was centrifuged, washed with DMF and acetone five times each, and then dried at 60°C for 10 h to finally obtain PCN-224(Cu)@BiVO4 with a BiVO4 mass fraction of 15%.

[0044] Example 2

[0045] A method for preparing a carbon dioxide reduction photocatalyst comprises the following steps:

[0046] A. Preparation of BiVO4

[0047] The operation process is the same as in Example 1.

[0048] B. Preparation of PCN-224(Cu)@BiVO4

[0049] The operation process is the same as that of Example 1 except for the following differences.

[0050] 0.0032g BiVO4 was dispersed in 16mL DMF to finally prepare PCN-224(Cu)@BiVO4 with a BiVO4 mass fraction of 5%.

[0051] Example 3

[0052] A method for preparing a carbon dioxide reduction photocatalyst comprises the following steps:

[0053] A. Preparation of BiVO4

[0054] The operation process is the same as in Example 1.

[0055] B. Preparation of PCN-224(Cu)@BiVO4

[0056] The operation process is the same as that of Example 1 except for the following differences.

[0057] 0.0067 g BiVO4 was dispersed in 16 mL DMF to finally prepare PCN-224(Cu)@BiVO4 with a BiVO4 mass fraction of 10%.

[0058] Example 4

[0059] A method for preparing a carbon dioxide reduction photocatalyst comprises the following steps:

[0060] A. Preparation of BiVO4

[0061] The operation process is the same as in Example 1.

[0062] B. Preparation of PCN-224(Cu)@BiVO4

[0063] The operation process is the same as that of Example 1 except for the following differences.

[0064] 0.0150 g BiVO4 was dispersed in 16 mL DMF to finally prepare PCN-224(Cu)@BiVO4 with a BiVO4 mass fraction of 20%.

[0065] Comparative Example 1

[0066] (1) 0.1023 g CuTCPP, 0.1605 g ZrCl4, and 5.4019 g benzoic acid were added to 16 mL DMF and sonicated for 20 min.

[0067] (2) The above solution was transferred to a polytetrafluoroethylene-lined autoclave and reacted at 120°C for 48 hours.

[0068] (3) The obtained solid product was centrifuged, washed with DMF and acetone five times each, and then dried at 60°C for 10 h to finally obtain pure PCN-224(Cu).

[0069] Comparative Example 2

[0070] Comparative Example 2 is pure BiVO4.

[0071] Photocatalytic reduction of CO2 experiment:

[0072] The photocatalytic reduction of carbon dioxide performance test was conducted in a CEL-PAEM-D8 photocatalytic activity evaluation system, manufactured by Beijing Zhongjiao Jinyuan Technology Co., Ltd. The specific procedure was as follows: 10 mg of the photocatalyst was evenly dispersed in 3 mL of ethanol solution and then evenly dropped onto a round white quartz sand plate. After the ethanol solution completely evaporated, the plate was placed in a glass reactor, and 10 mL of deionized water was added to the reactor. The reactor was tightly connected to the system and the entire system was evacuated to a vacuum. 99.995% pure carbon dioxide gas was then introduced into the system until the vacuum reading reached 0.5 MPa. A small fan was then turned on to allow the carbon dioxide gas to diffuse through the system for 30 minutes. Finally, the light source (300 W xenon lamp, λ > 420 nm) was turned on for the experiment, and the product was analyzed using an online gas chromatograph (GC-7920). The gas chromatograph was operated with nitrogen as the carrier, a hydrogen ion flame (FID) detector, and the inlet temperature was set at 200°C, the column oven temperature at 60°C, and the detector temperature at 200°C.

[0073] See attached Figure 1 , Figure 1 The XRD spectra of the PCN-224(Cu)@BiVO4 composite obtained in Examples 1-4 of the present invention, Comparative Example 1 and Comparative Example 2. Figure 1 It can be seen that six characteristic peaks appear at 2θ = 4.6°, 6.4°, 7.9°, 9.1°, 11.2° and 13.7° in Comparative Example 1, corresponding to the (002), (022), (222), (004), (224) and (006) crystal planes of PCN-224 (Cu), respectively. The XRD peaks of Comparative Example 2 are consistent with the standard card (JCPDS14-0688) of monoclinic BiVO4. In the XRD patterns of the samples synthesized in Examples 1-4, characteristic diffraction peaks of BiVO4 and PCN-224 (Cu) appear at the same time, indicating that the PCN-224 (Cu) @ BiVO4 composite photocatalyst was successfully synthesized.

[0074] See attached Figure 2 , Figure 2The scanning electron microscope, transmission electron microscope, and elemental surface scan of the PCN-224(Cu)@BiVO4 composite obtained in Example 1 of the present invention are shown. It can be seen that the synthesized PCN-224(Cu) has a rod-like morphology with a rod length of about 3-6 μm. Pure BiVO4 is a nanosheet with a size of 300-400 nm. From the electron microscope image of PCN-224(Cu)@BiVO4, it can be observed that the BiVO4 nanosheets are evenly distributed on the surface of the rod-shaped PCN-224(Cu), and the two are in close contact. The elemental surface scan of the composite shows that C, N, O, Zr, Cu, V, and Bi elements are present in the PCN-224(Cu)@BiVO4 sample, and the elements are evenly distributed.

[0075] See attached Figure 3 , Figure 3 The performance graphs for the photocatalytic reduction of CO2 using the catalysts obtained in Examples 1-4 and the comparative example are shown. Under these experimental conditions, no other gaseous or liquid products were detected except CO, indicating that the synthesized catalysts can convert CO2 to CO with high selectivity. As can be seen from the graph, pure BiVO4 is inactive for photocatalytic CO2 reduction. PCN-224(Cu) alone has low photocatalytic activity, with a carbon monoxide yield of only 13.93 μmol·g -1 ·h -1 After PCN-224(Cu) was combined with BiVO4, the photocatalytic activity of PCN-224(Cu)@BiVO4 was significantly improved, and the photocatalytic activity increased with the increase of BiVO4 content. When the BiVO4 content was 15%, the photocatalytic activity was the highest, and the carbon monoxide yield reached 70.5μmol·g -1 ·h -1 , which is about 5 times that of pure PCN-224(Cu).

[0076] See attached Figure 4 , Figure 4 This is a graph showing the photocatalytic cycling performance of the catalyst obtained in Example 1. The results show that PCN-224(Cu)@BiVO4 maintains high catalytic activity after five photocatalytic experiments, indicating that PCN-224(Cu)@BiVO4 has good reusability.

[0077] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A carbon dioxide reduction photocatalyst, characterized in that including PCN-224(Cu) and BiVO4 nanosheets supported thereon; The PCN-224 (Cu) is in rod shape, and the mass percentage of BiVO4 in the carbon dioxide reduction photocatalyst is 5%-20%; The catalyst is a PCN-224(Cu)@BiVO4 composite visible light catalyst, which is composed of PCN-224(Cu) and BiVO4. The BiVO4 is in the form of nanosheets and is evenly distributed on the surface of the rod-shaped PCN-224(Cu).

2. The carbon dioxide reduction photocatalyst according to claim 1, characterized in that The mass percentage of BiVO4 in the carbon dioxide reduction photocatalyst is 15%.

3. A method for preparing a carbon dioxide reduction photocatalyst according to any one of claims 1 to 2, characterized in that: The following steps are involved: BiVO4 is uniformly dispersed in N,N-dimethylformamide, and tetrakis-(4-carboxyphenyl)porphyrin copper, ZrCl4 and benzoic acid are added in sequence and reacted to obtain the carbon dioxide reduction photocatalyst.

4. The method for preparing a carbon dioxide reduction photocatalyst according to claim 3, wherein: The reaction temperature is 110-130° C., and the reaction time is 40-50 h.

5. The method for preparing a carbon dioxide reduction photocatalyst according to claim 3, wherein: The preparation method of BiVO4 comprises the following steps: (1) Dissolve Bi(NO3)3·5H2O in HNO3 solution to obtain solution A, and add NH4VO3 to deionized water to obtain solution B; (2) Add solution A dropwise to solution B under stirring, add a certain amount of sodium dodecylbenzenesulfonate, and continue stirring; (3) adding alkaline solution to adjust the pH of the solution; (4) Transfer the solution to a high-pressure reactor and react at 160-200°C for 3-12 hours; (5) The solid product is centrifuged, washed, and dried to obtain flaky BiVO4.

6. The method for preparing a carbon dioxide reduction photocatalyst according to claim 5, characterized in that: The molar ratio of Bi(NO3)3·5H2O, NH4VO3 and sodium dodecylbenzenesulfonate is 1:1:0.2-0.

4.

7. The method for preparing a carbon dioxide reduction photocatalyst according to claim 5, wherein: The alkaline solution includes NaOH, KOH, and Na2CO3.

8. The method for preparing a carbon dioxide reduction photocatalyst according to claim 5, wherein: Step (3) adjusting the pH value of the solution to 7.

9. Use of the carbon dioxide reduction photocatalyst according to any one of claims 1 to 2, characterized in that: The catalyst is used for photocatalytic reduction of carbon dioxide.

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