A z-type photocatalyst based on copper phthalocyanine, a preparation method and application thereof in photocatalytic reduction of carbon dioxide

Abstract

The application discloses a Z-type photocatalyst based on copper phthalocyanine, a preparation method and application of the Z-type photocatalyst in photocatalytic reduction of carbon dioxide, and the photocatalyst is prepared by using potassium permanganate, manganese nitrate, copper phthalocyanine and phosphoric acid as raw materials, and using ethanol and deionized water as polar solvents and adopting a hydrothermal method. The microstructure of the prepared Z-type photocatalyst of copper phthalocyanine (CuPc) / alpha-MnO2 presents a layered self-assembly flower shape, a relatively high surface area provides more active adsorption sites, and mass transfer of reactants is facilitated. The method proves that the Z-type heterojunction formed by CuPc / PO-alpha-MnO2 can realize hole capture, spatial separation and transfer of charge carriers, and solves the problem that CuPc / PO-alpha-MnO2 exhibits unprecedented activity of photo-reduction of CO2 into CO and CH4 without a noble metal cocatalyst and a sacrificial agent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of semiconductor photocatalysis, and particularly relates to a Z-type photocatalyst based on copper phthalocyanine (CuPc) / α-MnO2, a preparation method and application thereof in photocatalytic reduction of carbon dioxide (CO2). TECHNICAL BACKGROUND

[0002] At present, our energy demand is met by carbon dioxide emission technology, which has adverse effects on human beings and human life due to climate change and global warming. In order to reduce the impact of these problems, it is urgent to decarbonize the energy system. Photocatalysis plays a potential key role in reducing CO2 emissions by converting CO2 into benign and environmentally friendly products.

[0003] Recently, semiconductor-based photocatalysis has attracted great attention to the CO2 reduction reaction. However, the research field of photocatalytic CO2 reduction (PCR) is still in its infancy. The development of efficient PCR photocatalysts is an ongoing process. In order to overcome the efficiency bottleneck in the existing PCR photocatalysts, the design of advanced photocatalysts should focus on the expansion of visible light absorption and efficient charge separation and transport. The generation of heterojunctions between asymmetric catalysts is a feasible strategy to enhance the absorption of longer wavelength photons and the spatial separation and transfer of electron-hole pairs.

[0004] The actual efficiency of the heterojunction photocatalyst mainly depends on the physical and chemical properties involved in the catalyst. Although the heterojunction photocatalyst is more advantageous than the single photocatalyst, the loss of charge carriers due to recombination and the lack of appropriate catalytic sites for redox reactions are several major challenges that have not been overcome. SUMMARY

[0005] In order to solve the problems existing in the background art, the present application provides a Z-type photocatalyst based on copper phthalocyanine (CuPc) / α-MnO2, a preparation method and application thereof in photocatalytic reduction of CO2.

[0006] The present application specifically adopts the following technical solutions:

[0007] A preparation method of a Z-type photocatalyst based on copper phthalocyanine, which is prepared by using potassium permanganate, manganese nitrate, copper phthalocyanine and phosphoric acid as raw materials, and ethanol and deionized water as polar solvents, and by using a hydrothermal method.

[0008] Further, the preparation method of the Z-type photocatalyst based on copper phthalocyanine comprises the following steps:

[0009] (1) In an aqueous solution, manganese nitrate and potassium permanganate are uniformly mixed in a certain proportion, and are loaded into an oven for hydrothermal treatment for a period of time. The mixture after hydrothermal treatment is centrifuged and washed with water and ethanol;

[0010] (2) The rinsed material is dried at a certain temperature for a period of time, and then calcined in a muffle furnace to obtain three-dimensional layered self-assembled alpha-MnO2 nanoflowers;

[0011] (3) Phosphoric acid is added to the alpha-MnO2, and the mixture is dispersed in ethanol and stirred;

[0012] (4) The phosphated alpha-MnO2 and CuPc are dispersed in ethanol while stirring, and evaporated in a water bath; the dried sample is placed in an oven to remove water, and a copper phthalocyanine (CuPc) / alpha-MnO2-based Z-type photocatalyst is prepared.

[0013] Further, the molar ratio of manganese nitrate to potassium permanganate in step (1) is 1:7-7.5, and the total volume is 50-100 ml.

[0014] Further, the oven temperature in step (1) is 150-250℃, and the hydrothermal treatment time is 10-15h.

[0015] Further, the rinsed material in step (2) is dried at 100-120℃ for 10-15h.

[0016] Further, the sample in step (2) is placed in a muffle furnace and calcined at 250-350℃ for 2-4h (4-6℃ / min -1 ).

[0017] Further, in step (3), 0.1-1mmol L -1 phosphoric acid and 0.2-0.6g alpha-MnO2 are taken in 50-100ml ethanol and stirred for 10-15h.

[0018] Further, in step (4), the phosphated alpha-MnO2 and CuPc are evenly dispersed in 40-60ml ethanol, and evaporated in a water bath at 75-85℃.

[0019] The application also provides a copper phthalocyanine-based Z-type photocatalyst for use in photocatalytic reduction of CO2.

[0020] The application has the following beneficial effects:

[0021] In the application, potassium permanganate, manganese nitrate and copper phthalocyanine are used as raw materials, ethanol and deionized water are used as polar solvents, and a hydrothermal method is used for preparation. The alpha-MnO2 prepared by potassium permanganate and manganese nitrate can enhance the activity of charge separation, reduce the diffusion length of charge carriers and have a large specific surface area. Copper phthalocyanine (CuPc) is a planar conjugated macrocyclic molecule, and the HOMO energy level is lower than the CB minimum value of alpha-MnO2, which meets the standard of energy band arrangement. Phosphate can prevent the self-aggregation of the molecular catalyst CuPc on the alpha-MnO2 support through strong interface H-bond interaction. Cu 2+ The active sites of the catalytic function are provided, the high dispersity of CuPc provides abundant catalytic sites for the adsorption, activation and photoreduction of CO2, and the CuPc / alpha-MnO2 Z-type heterojunction modulated by phosphate can realize hole capture, spatial separation and transfer of charge carriers. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A preparation flow chart of the copper phthalocyanine (CuPc) / alpha-MnO2-based Z-type photocatalyst prepared in the embodiment;

[0023] Figure 2 A scanning electron microscope image of the copper phthalocyanine (CuPc) / alpha-MnO2-based Z-type photocatalyst prepared in the embodiment;

[0024] Figure 3 A transmission electron microscope image of the copper phthalocyanine (CuPc) / alpha-MnO2-based Z-type photocatalyst prepared in the embodiment;

[0025] Figure 4 An X-ray diffraction pattern of the copper phthalocyanine (CuPc) / alpha-MnO2-based Z-type photocatalyst prepared in the embodiment;

[0026] Figure 5 A photocatalytic CO2 reduction performance graph of the copper phthalocyanine (CuPc) / alpha-MnO2-based Z-type photocatalyst prepared in the embodiment.

[0027] DETAILED DESCRIPTION

[0028] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be described in further detail below with reference to the drawings.

[0029] Embodiment 1

[0030] As Figure 1 shown, a preparation method of a copper phthalocyanine (CuPc) / alpha-MnO2-based Z-type photocatalyst includes the following steps:

[0031] (1) 0.5 g of potassium permanganate and 0.075 g of manganese nitrate solution were added to 70 ml of water, and then the mixture was hydrothermally treated in an oven at 200°C for 12 hours. The hydrothermally treated mixture was centrifuged and washed with water and ethanol;

[0032] (2) The rinsed material was dried at 105°C for 12 hours, and then calcined in a muffle furnace at 300°C for 3 hours (5°C / min);

[0033] (3) 0.2 mmol / L of phosphoric acid was added to a dispersion mixture of 0.4 g of α-MnO2 in 60 ml of ethanol and stirred for 12 hours; -1

[0034] (4) 1.0 g of the phosphoric acid-modified α-MnO2 and CuPc were evenly dispersed in 50 ml of ethanol while stirring, and then evaporated in a water bath at 80°C. Then, the dried sample was placed in an oven to remove moisture, to prepare a Z-type photocatalyst based on copper phthalocyanine (CuPc) / α-MnO2.

[0035] Photocatalysis experiment: 0.1 g of photocatalyst powder was dispersed in 5 ml of water, and then added to a reactor. High-purity CO2 gas was passed through water, and then into the reaction device to reach ambient pressure. The photocatalyst was equilibrated in the CO2 / H2O system for 20 minutes, and then irradiated for 4 hours. During irradiation, 250 μL of gaseous reactants were drawn from the reaction cell at regular intervals, and the concentrations of CO, CH4 and O2 were analyzed using a gas chromatograph (CO and CH4 using Techcomp GC-7920 with FID detector; O2 using Techcomp GC-7900 with TCD detector).

[0036] Figure 2 A scanning electron microscope image of the Z-type photocatalyst based on copper phthalocyanine (CuPc) / α-MnO2 prepared in this example is shown in Figure 1. Figure 2 As can be seen, the Z-type photocatalyst based on copper phthalocyanine (CuPc) / α-MnO2 exhibits a layered self-assembled flower-like morphology, with uniform morphology, large quantity, uniform structure and no other impurity morphology.

[0037] Figure 3 A transmission electron microscope image of the Z-type photocatalyst based on copper phthalocyanine (CuPc) / α-MnO2 prepared in this example is shown in Figure 2. Figure 3 It can be further confirmed that the Z-type photocatalyst based on copper phthalocyanine (CuPc) / α-MnO2 has a self-assembled flower-like morphology.

[0038] Figure 4 An X-ray diffraction pattern of the Z-type photocatalyst based on copper phthalocyanine (CuPc) / α-MnO2 prepared in this example is shown in Figure 3. Figure 4 ​It can be seen that the typical XRD peaks are completely consistent with α-MnO2 (JCPDS NO. 44-0141). No obvious CuPc peaks and phosphate modification peaks are found in the patterns of xCuPc / α-MnO2 and 1.5CuPc / 9PO-α-MnO2, because their dispersity is very high and CuPc effectively changes the light absorption of α-MnO2.

[0039] Figure 5 is a photocatalytic CO2 reduction performance diagram of the copper phthalocyanine (CuPc) / α-MnO2-based Z-type photocatalyst prepared in the embodiment, prepared by Figure 5 It can be seen that the rate of CO and CH4 produced by the copper phthalocyanine (CuPc) / α-MnO2-based Z-type photocatalyst almost linearly increases with the extension of irradiation time, and the photocatalytic performance does not obviously attenuate in the 6-hour collection process, indicating that the structure of the copper phthalocyanine (CuPc) / α-MnO2-based Z-type photocatalyst prepared in the embodiment is relatively stable.

[0040] Example 2

[0041] As shown in Figure 1 , a preparation method of a copper phthalocyanine (CuPc) / α-MnO2-based Z-type photocatalyst includes the following steps:

[0042] (1) 0.5 g of potassium permanganate and 0.075 g of manganese nitrate solution are added to 70 ml of water, and then the mixture after hydrothermal treatment at 200°C for 12 hours is centrifuged and washed with water and ethanol;

[0043] (2) The rinsed material is dried at 105°C for 12 hours, and then calcined at 300°C in a muffle furnace (5°C / min) for 3 hours;

[0044] (3) 0.4 mmol / L of phosphoric acid is added to 0.4 g of α-MnO2 in a dispersion mixture of 60 ml of ethanol and stirred for 12 hours;

[0045] (4) 1.0 g of phosphate-modified α-MnO2 and CuPc are evenly dispersed in 50 ml of ethanol while stirring, and then evaporated in a water bath at 80°C, and then the dried sample is placed in an oven to remove moisture, to prepare a copper phthalocyanine (CuPc) / α-MnO2-based Z-type photocatalyst.

[0046] Example 3

[0047] As shown in Figure 1 , a preparation method of a copper phthalocyanine (CuPc) / α-MnO2-based Z-type photocatalyst includes the following steps:

[0048] (1) 0.5 g of potassium permanganate and 0.075 g of manganese nitrate solution were added to 70 ml of water, and then the mixture was hydrothermally treated in an oven at 200°C for 12 hours. The hydrothermally treated mixture was centrifuged and washed with water and ethanol;

[0049] (2) The rinsed material was dried at 105°C for 12 hours, and then calcined in a muffle furnace at 300°C for 3 hours (5°C / min);

[0050] (3) 0.2 mmol L"1of phosphoric acid was added to 0.6 g of α-MnO2in a dispersion mixture in 60 ml of ethanol and stirred for 12 hours; -1

[0051] (4) 1.0 g of the phosphated α-MnO2was evenly dispersed in 50 ml of ethanol with CuPc while stirring, and then evaporated in a water bath at 80°C. The dried sample was then placed in an oven to remove moisture, and a Z-type photocatalyst based on copper phthalocyanine (CuPc) / α-MnO2was prepared.

[0052] The above description is only for understanding the method and core idea of the present application, and it should be noted that those skilled in the art can make several improvements and modifications to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the scope of the protection of the present application.​

Claims

1. A method for preparing a Z-type photocatalyst based on copper phthalocyanine, characterized in that: Comprising the steps of: (1) mixing manganese nitrate and potassium permanganate in a certain ratio in an aqueous solution, loading into an oven for hydrothermal treatment for a period of time, centrifugal separation of the mixture after hydrothermal treatment and washing with water and ethanol; (2) drying the rinsed material at a certain temperature for a period of time, then calcining in a muffle furnace to obtain three-dimensional layered self-assembled α-MnO2 nanoflowers; (3) adding phosphoric acid to α-MnO2 in a dispersion mixture in ethanol and stirring; (4) dispersing the phosphated α-MnO2 and CuPc in ethanol while stirring, evaporating in a water bath, removing water from the dried sample in an oven to prepare a copper phthalocyanine (CuPc) / α-MnO2-based Z-type photocatalyst; The molar ratio of manganese nitrate and potassium permanganate in step (1) is 1:7-7.5, and the total volume is 50-100 ml; The oven temperature in step (1) is 150-250°C, and the hydrothermal treatment time is 10-15 h; In step (2), the sample is placed in a muffle furnace and calcined at 250-350°C for 2-4 h; In step (3), take 0.1-1 mmol L -1 phosphoric acid, 0.2-0.6 grams of α-MnO2, in 50-100 mL of ethanol and stir for 10-15 hours; In step (4), the phosphated α-MnO2 and CuPc are dispersed in 40-60 ml of ethanol on average, and evaporated in a water bath at 75-85°C.

2. The method for preparing a Z-type photocatalyst based on copper phthalocyanine according to claim 1, characterized by, The rinsed material in step (2) is dried at 100-120°C for 10-15 h.

3. A copper phthalocyanine-based Z-type photocatalyst prepared by the method of claim 1 or 2.

4. Use of the copper phthalocyanine-based Z-type photocatalyst of claim 3 in photocatalytic reduction of carbon dioxide.

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