Heterojunction composite material and preparation method and application thereof

Abstract

The invention discloses a heterojunction composite material and a preparation method and application thereof, and belongs to the technical field of catalysts, and the preparation method comprises the following steps: dispersing LaFeO3 and g-C3N4 in water, adding CuCl2, uniformly stirring, adding a sodium citrate aqueous solution, continuously stirring for 12-24 hours, centrifuging, washing and drying to obtain the heterojunction composite material; the mass ratio of the LaFeO3 to the g-C3N4 to the CuCl2 is (10 to 30) to (70 to 90) to (10 to 30). According to the invention, two narrow-band gap semiconductors (LaFeO3 and Cu2O) and a wide-band gap semiconductor (g-C3N4) are compounded to form the composite material with the double-heterojunction structure. As a photocatalyst, the material can be effectively applied to pollution control, and has excellent capabilities of removing organic water pollutants and air pollutants and sterilizing.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and particularly to a heterojunction composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Photocatalysis is a process of accelerating reactions using photocatalysts. Under the irradiation of light, the photocatalyst absorbs the photon energy of the light and is excited to generate active species such as photogenerated electrons and holes, which have high redox reaction activities. Therefore, scientists have been exploring different materials as photocatalysts to improve their efficiency and extend their light absorption ability from the ultraviolet range to the visible spectrum. Photocatalysis technology has thus been widely applied in fields such as environmental remediation, water treatment, energy production, and self-cleaning surfaces.

[0003] Despite decades of research, photocatalysis technology has made certain progress, but due to low light utilization efficiency, the practical application of photocatalysis technology still faces challenges. Therefore, improving the efficiency of light absorption and charge carrier separation to make photocatalysis technology economically suitable for large-scale applications is the focus of current research and development in this field. Photocatalysis is expected to become a sustainable solution to environmental and energy problems.

[0004] In view of this, the present application is proposed. Summary of the Invention

[0005] An object of the present invention is to overcome the deficiencies existing in the prior art, and to provide a heterojunction composite material, a preparation method thereof, and an application thereof. The heterojunction composite material can be used as a photocatalyst in pollution control and has excellent capabilities for removing organic water pollutants, air pollutants, and sterilization.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a heterojunction composite material, comprising the following steps:

[0008] Disperse LaFeO 3 and g-C 3 N 4 in water, add CuCl 2 , stir evenly, then add an aqueous solution of sodium citrate, continue to stir evenly for 12 - 24 h, centrifuge, wash, and dry to obtain the heterojunction composite material;

[0009] The mass ratio of the LaFeO 3 , g-C 3 N 4 , and CuCl 2 is (10 - 30):(70 - 90):(10 - 30).

[0010] The present invention creatively combines two narrow-bandgap semiconductors (LaFeO 3 and Cu 2 O) with a wide-bandgap semiconductor (g-C 3 N 4 ) to form a composite photocatalyst with a double heterojunction structure. Under the interaction of the three, the designed composite material not only broadens the response range of sunlight, but also promotes the separation and transfer of photoinduced electrons and holes, thereby improving the photocatalytic redox ability of the catalyst and ultimately enhancing its photocatalytic performance. As a photocatalyst, this material can be applied to pollution control and has excellent capabilities for removing organic water pollutants, air pollutants, and sterilization. For example, it has good removal effects on rhodamine B, Escherichia coli, etc.

[0011] As a preferred embodiment of the present invention, the mass concentration of the sodium citrate aqueous solution is 5-15%, and the solid-liquid ratio of CuCl 2 to the sodium citrate aqueous solution is (10-30) mg:(50-100) mL.

[0012] As a preferred embodiment of the present invention, the solid-liquid ratio of LaFeO 3 to water is (10-30) mg:(50-200) mL.

[0013] As a preferred embodiment of the present invention, the preparation method of LaFeO 3 is as follows: Dissolve La(NO 3 ) 3 ·6H 2 O and Fe(NO 3 ) 3 ·9H 2 O in water to form solution A; dissolve citric acid in water to form solution B, add solution B to solution A, stir evenly, dry, and sinter to obtain LaFeO 3 .

[0014] As a preferred embodiment of the present invention, the molar ratio of La(NO 3 ) 3 ·6H 2 O, Fe(NO 3 ) 3 ·9H 2 O, and citric acid is (2-10):(2-10):(4-20).

[0015] As a preferred embodiment of the present invention, the sintering temperature is 600-1000 °C, and the sintering time is 1-4 h.

[0016] As a preferred embodiment of the present invention, LaFeO 3The preparation method is as follows: Dissolve 2 - 10 mmol of La(NO 3 ) 3 ·6H 2 O and 2 - 10 mmol of Fe(NO 3 ) 3 ·9H 2 O in 10 - 50 mL of water to form solution A; Dissolve 4 - 20 mmol of citric acid in 30 - 100 mL of water to form solution B, add solution B to solution A, stir evenly, dry, and sinter to obtain LaFeO 3 .

[0017] As a preferred embodiment of the present invention, the preparation method of the g-C 3 N 4 is as follows:

[0018] Place melamine in a muffle furnace, first heat-treat it at 400 - 600 °C for 1 - 3 hours, and then heat-treat it at 400 - 600 °C for 1 - 3 hours to obtain g-C 3 N 4 .

[0019] The present invention also provides a heterojunction composite material prepared by the above preparation method.

[0020] The present invention also provides an application of a heterojunction composite material as a photocatalyst in treating polluted wastewater.

[0021] As a preferred embodiment of the present invention, the organic matter in sewage is removed by the heterojunction photocatalytic material under photocatalysis and / or the heterojunction photocatalytic material sterilizes under photocatalysis.

[0022] The beneficial effects of the present invention are as follows: By combining two narrow-bandgap semiconductors (LaFeO 3 and Cu 2 O) with a wide-bandgap semiconductor (g-C 3 N 4 ), a double heterojunction structure composite photocatalyst is formed. Under the combined action of the three, the designed composite material not only broadens the response range of sunlight but also promotes the separation and transfer of photoinduced electrons and holes, thereby improving the photocatalytic redox ability of the catalyst and ultimately enhancing its photocatalytic performance. This material can be used as a photocatalyst in pollution control and has excellent abilities to remove organic water pollutants, air pollutants, and sterilize, such as having good removal effects on rhodamine B, Escherichia coli, etc. Description of the Drawings

[0023] Figure 1 It is the degradation diagram of rhodamine B by the heterojunction composite material of Example 1. Detailed Embodiments

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without making creative efforts fall within the scope of protection of this application.

[0025] In this application, among the technically characterized described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open technical solutions containing the listed features.

[0026] In this application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0027] In this application, there are no particular limitations on the specific dispersion and stirring treatment methods.

[0028] Unless otherwise specified, the component raw materials or instruments used in the embodiments and comparative examples of the present invention are all commercially available raw materials or instruments, and the component raw materials used in each parallel experiment are of the same kind.

[0029] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0030] The following embodiments are provided to facilitate the understanding of the present invention. These embodiments are not provided to limit the scope of the claims.

[0031] Example 1

[0032] A method for preparing a heterojunction composite material, comprising the following steps:

[0033] (1) Synthesize LaFeO 3 : Mix 5 mmol of La(NO 3 ) 3 ·6H 25 mmol of La(NO 3 ) 3 ·9H 2 O was dissolved in 30 mL of water to form solution A; 10 mmol of citric acid was dissolved in 30 mL of water to form solution B. Solution B was added to solution A, stirred for 30 minutes, and then dried in an oven at 100 °C for 12 hours. The obtained powder was placed in a tube furnace and sintered at 800 °C for 2 hours to obtain LaFeO 3 .

[0034] (2) Synthesis of g-C 3 N 4 : Melamine was heat-treated in a muffle furnace at 500 °C for 2 hours and then heat-treated at 500 °C for another 2 hours.

[0035] (3) Synthesis of Cu 2 O / LaFeO 3 / g-C 3 N 4 : 20 mg of LaFeO 3 and 80 mg of g-C 3 N 4 were dispersed in 100 ml of deionized water, and then 25 mg of CuCl 2 was added to the above mixed solution and stirred evenly. Then, the sodium citrate solution (120 mL, 10 wt%) was slowly added to the above mixture. The solution was continuously stirred at 100 °C for 24 hours. Subsequently, the mixture was centrifuged, washed, and dried in vacuo at 60 °C to obtain the heterojunction composite material.

[0036] Example 2

[0037] A method for preparing a heterojunction composite material, comprising the following steps:

[0038] (1) Synthesis of LaFeO 3 : 5 mmol of La(NO 3 ) 3 ·6H 2 O and 5 mmol of Fe(NO 3 ) 3 ·9H 2 O were dissolved in 30 mL of water to form solution A; 10 mmol of citric acid was dissolved in 30 mL of water to form solution B. Solution B was added to solution A, stirred for 30 minutes, and then dried in an oven at 100 °C for 12 hours. The obtained powder was placed in a tube furnace and sintered at 800 °C for 2 hours to obtain LaFeO 3 .

[0039] (2) Synthesis of g-C 3 N 4: Melamine is heat-treated in a muffle furnace at 500 °C for 2 hours and then heat-treated at 500 °C for 2 h.

[0040] (3) Synthesize Cu 2 O / LaFeO 3 / g-C 3 N 4 : Disperse 10 mg of LaFeO 3 and 90 mg of g-C 3 N 4 in 100 ml of deionized water, then add 10 mg of CuCl 2 to the above mixed solution and stir evenly. Then slowly add the sodium citrate solution (120 mL, 10 wt%) to the above mixture. The solution is continuously stirred at 100 °C for 24 hours. Subsequently, the mixture is centrifuged, washed, and dried in vacuo at 60 °C to obtain the heterojunction composite material.

[0041] Example 3

[0042] A method for preparing a heterojunction composite material, comprising the following steps:

[0043] (1) Synthesize LaFeO 3 : Dissolve 5 mmol of La(NO 3 ) 3 ·6H 2 O and 5 mmol of Fe(NO 3 ) 3 ·9H 2 O in 30 mL of water to form solution A; dissolve 10 mmol of citric acid in 30 mL of water to form solution B. Add solution B to solution A, stir for 30 minutes, and place it in an oven at 100 °C for 12 hours. The obtained powder is placed in a tube furnace and sintered at 800 °C for 2 hours to obtain LaFeO 3 .

[0044] (2) Synthesize g-C 3 N 4 : Heat-treat melamine in a muffle furnace at 500 °C for 2 hours. After cooling to room temperature, heat-treat it at 500 °C for 2 h.

[0045] (3) Synthesize Cu 2 O / LaFeO 3 / g-C 3 N 4 : Disperse 30 mg of LaFeO 3 and 70 mg of g-C 3 N 4 in 100 ml of deionized water, then add 30 mg of CuCl 2Add it to the above mixed solution and stir evenly. Then slowly add the sodium citrate solution (120 mL, 10 wt%) to the above mixture. The solution is continuously stirred at 100 °C for 24 hours. Subsequently, the mixture is centrifuged and washed, and dried in vacuum at 60 °C to obtain the heterojunction composite material.

[0046] Comparative Example 1

[0047] A preparation method of a heterojunction composite material, comprising the following steps:

[0048] (1) Synthesize LaFeO 3 : Dissolve 5 mmol of La(NO 3 ) 3 ·6H 2 O and 5 mmol of Fe(NO 3 ) 3 ·9H 2 O in 30 mL of water to form solution A; dissolve 10 mmol of citric acid in 30 mL of water to form solution B. Add solution B to solution A, stir for 30 minutes, and place it in an oven at 100 °C for drying for 12 hours. The obtained powder is placed in a tube furnace and sintered at 800 °C for 2 hours to obtain LaFeO 3 .

[0049] (2) Synthesize g-C 3 N 4 : Heat-treat melamine in a muffle furnace at 500 °C for 2 hours. After the temperature drops to room temperature, heat-treat it at 500 °C for another 2 hours.

[0050] (3) Synthesize Cu 2 O / LaFeO 3 / g-C 3 N 4 : Disperse 5 mg of LaFeO 3 and 120 mg of g-C 3 N 4 in 100 ml of deionized water, and then add 2 mg of CuCl 2 to the above mixed solution and stir evenly. Then slowly add the sodium citrate solution (120 mL, 10 wt%) to the above mixture. The solution is continuously stirred at 100 °C for 24 hours. Subsequently, the mixture is centrifuged and washed, and dried in vacuum at 60 °C to obtain the heterojunction composite material.

[0051] Comparative Example 2

[0052] A preparation method of a heterojunction composite material, comprising the following steps:

[0053] (1) Synthesize LaFeO 3 : Dissolve 5 mmol of La(NO 3 )3 ·6H 2 O and 5 mmol Fe(NO 3 ) 3 ·9H 2 O are dissolved in 30 mL of water to form solution A; 10 mmol of citric acid is dissolved in 30 mL of water to form solution B. Solution B is added to solution A, stirred for 30 minutes, and then dried in an oven at 100 °C for 12 hours. The obtained powder is placed in a tube furnace and sintered at 800 °C for 2 hours to obtain LaFeO 3 .

[0054] (2) Synthesis of g-C 3 N 4 : Melamine is heat-treated in a muffle furnace at 500 °C for 2 hours. After the temperature drops to room temperature, it is heat-treated at 500 °C for another 2 hours.

[0055] (3) Synthesis of Cu 2 O / LaFeO 3 / g-C 3 N 4 : 50 mg of LaFeO 3 and 50 mg of g-C 3 N 4 are dispersed in 100 ml of deionized water, and then 50 mg of CuCl 2 is added to the above mixed solution and stirred evenly. Then, the sodium citrate solution (120 mL, 10 wt%) is slowly added to the above mixture. The solution is continuously stirred at 100 °C for 24 hours. Subsequently, the mixture is centrifuged, washed, and dried in vacuum at 60 °C to obtain the heterojunction composite material.

[0056] Comparative Example 3

[0057] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, LaFeO 3 is not added, and an equal amount of CuCl 2 is used for replacement.

[0058] A preparation method of a heterojunction composite material, comprising the following steps:

[0059] (1) Synthesis of LaFeO 3 : 5 mmol of La(NO 3 ) 3 ·6H 2 O and 5 mmol of Fe(NO 3 ) 3 ·9H 2O is dissolved in 30 mL of water to form solution A; 10 mmol of citric acid is dissolved in 30 mL of water to form solution B. Solution B is added to solution A, stirred for 30 minutes, and then dried in an oven at 100 °C for 12 hours. The obtained powder is placed in a tube furnace and sintered at 800 °C for 2 h to obtain LaFeO 3 .

[0060] (2) Synthesis of g-C 3 N 4 : Melamine is heat-treated in a muffle furnace at 500 °C for 2 hours, and then heat-treated at 500 °C for another 2 hours.

[0061] (3) Disperse 80 mg of g-C 3 N 4 in 100 ml of deionized water, and then add 45 mg of CuCl 2 to the above mixed solution and stir evenly. Then, slowly add the sodium citrate solution (120 mL, 10 wt%) to the above mixture. The solution is continuously stirred at 100 °C for 24 hours. Subsequently, the mixture is centrifuged and washed, and dried in vacuo at 60 °C to obtain the heterojunction composite material.

[0062] Comparative Example 4

[0063] The difference between Comparative Example 4 and Example 1 is that CuCl 2 was not added in Comparative Example 4, and an equal amount of LaFeO 3 was used for replacement.

[0064] A preparation method of a heterojunction composite material, comprising the following steps:

[0065] (1) Synthesis of LaFeO 3 : Dissolve 5 mmol of La(NO 3 ) 3 ·6H 2 O and 5 mmol of Fe(NO 3 ) 3 ·9H 2 O in 30 mL of water to form solution A; dissolve 10 mmol of citric acid in 30 mL of water to form solution B. Solution B is added to solution A, stirred for 30 minutes, and then dried in an oven at 100 °C for 12 hours. The obtained powder is placed in a tube furnace and sintered at 800 °C for 2 hours to obtain LaFeO 3 .

[0066] (2) Synthesis of g-C 3 N 4 : Melamine is heat-treated in a muffle furnace at 500 °C for 2 hours. After the temperature drops to room temperature, it is heat-treated at 500 °C for another 2 hours.

[0067] (3) Synthesis of Cu2 O / LaFeO 3 / g-C 3 N 4 : Disperse 45 mg of LaFeO 3 and 80 mg of g-C 3 N 4 in 100 ml of deionized water, and then slowly add the sodium citrate solution (120 mL, 10 wt%) to the above mixture. Stir the solution continuously at 100 °C for 24 hours. Subsequently, centrifuge and wash the mixture, and dry it under vacuum at 60 °C to obtain the heterojunction composite material.

[0068] Test Example 1

[0069] 1. Disperse 20 mg of the heterojunction composite material in 50 ml (10 mM / L) of rhodamine B. After ultrasonic dispersion for 30 minutes, irradiate it with a xenon lamp at 100 mW / cm 2 . Take samples every half hour to test the concentration of rhodamine B.

[0070] Among them, the degradation effect of the heterojunction composite material in Example 1 on rhodamine B is as Figure 1 shown.

[0071] 2. Culture 50 μl of Escherichia coli strain (10 -6 CFU concentration) in 5 ml of medium at 250 rpm and 37 °C overnight. Take 30 μl of the culture and put it into 300 ml (0.85%) of autoclaved sodium chloride solution. Take 50 ml and dispense it into a serum bottle containing 150 mg of the heterojunction composite material, and seal it with aluminum foil. Place the bottle in an oscillating incubator with a photosynthesis lamp, culture it at 250 rpm and 37 °C for 5 hours, and then perform a colony content test on the LB agar plate to calculate the antibacterial rate.

[0072] Table 1

[0073]

[0074] As can be seen from Table 1, the heterojunction composite material described in the present invention can be used as a photocatalyst to treat polluted wastewater, and has excellent ability to remove organic pollutants and sterilize. It has good removal effects on rhodamine B, Escherichia coli, etc.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a heterojunction composite material, characterized in that: The following steps are involved: LaFeO3 and g-C3N4 are dispersed in water, CuCl2 is added, stirred evenly, and then sodium citrate aqueous solution is added, stirring is continued for 12-24 hours, centrifuged, washed, and dried to obtain a heterojunction composite material; The mass ratio of LaFeO3, g-C3N4 and CuCl2 is (10-30):(70-90):(10-30).

2. The method for preparing a heterojunction composite material according to claim 1, characterized in that: The mass concentration of the sodium citrate aqueous solution is 5-15%, and the solid-liquid ratio of the LaFeO3 to the sodium citrate aqueous solution is (10-30) mg: (50-100) mL.

3. The method for preparing a heterojunction composite material according to claim 1, characterized in that: The solid-liquid ratio of the LaFeO3 to water is (10-30) mg: (50-200) mL.

4. The method for preparing a heterojunction composite material according to claim 1, characterized in that: The preparation method of LaFeO3 is: La(NO3)3·6H2O and Fe(NO3)3·9H2O are dissolved in water to form solution A; citric acid is dissolved in water to form solution B, solution B is added to solution A, stirred evenly, dried, and sintered to obtain LaFeO3.

5. The method for preparing the heterojunction composite material according to claim 4, characterized in that: The molar ratio of La(NO3)3·6H2O, Fe(NO3)3·9H2O and citric acid is (2-10):(2-10):(4-20).

6. The method for preparing a heterojunction composite material according to claim 4, characterized in that: The sintering temperature is 600-1000° C., and the sintering time is 1-4 hours.

7. A heterojunction composite material, characterized in that: The preparation method is described in claims 1 to 6.

8. Use of the heterojunction composite material according to claim 7 as a photocatalyst in treating polluted wastewater.

9. The use according to claim 8, characterized in that: The heterojunction photocatalytic material removes organic matter from sewage and air under the photocatalytic effect and / or the heterojunction photocatalytic material sterilizes under the photocatalytic effect.

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