A method for preparing CuInS2-BiFeO3 piezoelectric photocatalyst and its application

Abstract

The invention discloses a preparation method and application of a CuInS2-BiFeO3 piezoelectric semiconductor heterojunction catalyst, wherein CuInS2 modified with positive charge is dispersed in isopropanol, BiFeO3 nanosheets synthesized by a hydrothermal method are added, stirred and heated together to evaporate the solvent, and a CuInS2-BiFeO3 composite piezoelectric photocatalyst is obtained by electrostatic self-assembly. The heterojunction can further drive the effective separation of photogenerated carriers at the heterojunction interface during the photocatalytic process by means of the polarization electric field formed inside the material when BiFeO3 is subjected to external mechanical force. Under the synergistic effect of mechanical vibration and visible light irradiation, the rate of hydrogen production by water decomposition is significantly higher than the rate of hydrogen production under a single condition. The introduction of piezoelectric effect to increase the rate of hydrogen production by heterojunction piezoelectric-photosynergistic catalysis has broad application prospects in the field of renewable energy production.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric photocatalytic materials, and more specifically to a CuInS2-BiFeO3 piezoelectric photocatalytic material and a preparation method and application thereof. Background Art

[0002] In recent years, the growing demand for energy and the related environmental problems have forced humans to develop and utilize sustainable clean energy to replace non-renewable energy. Among the many clean energy sources, hydrogen energy has attracted widespread attention due to its high energy density, zero pollution, high efficiency and other advantages, and is considered to have great development potential. At present, hydrogen energy has been included in my country's important strategic energy sources. The development of the hydrogen energy industry is a permanent strategic choice for mankind to get rid of its dependence on fossil energy and solve energy and environmental problems. In recent years, scientists at home and abroad have regarded semiconductor photocatalytic water splitting hydrogen production technology based on sunlight as one of the ideal ways to develop sustainable hydrogen energy.

[0003] CuInS2 is a typical ternary metal chalcogenide semiconductor with a narrow band gap (1.5 eV) structure and stable physical and chemical properties. It is an ideal material for photocatalytic water decomposition to produce hydrogen. However, the problem of rapid recombination of photogenerated carriers seriously limits the further improvement of its photocatalytic efficiency. In recent years, researchers have developed a variety of strategies such as doping elements, constructing heterojunctions, and introducing built-in electric fields to promote the separation and transfer of photogenerated charges. Among them, the construction of Z-type heterostructures can form a built-in electric field at the interface of the two materials to promote the separation of photogenerated carriers. BiFeO3 has been widely studied due to its narrow band gap (2.2 eV) and good chemical stability. Importantly, as a piezoelectric material, the polarization electric field formed inside the material when BiFeO3 is subjected to external mechanical force can effectively drive the efficient separation of photogenerated carriers at the heterojunction interface during the photocatalytic process. Therefore, it is of great significance to construct a CuInS2-BiFeO3 heterojunction and use the polarization electric field and Z-type heterojunction to synergistically promote the separation and migration of photogenerated carriers, thereby greatly improving the photocatalytic efficiency of photocatalysts. Summary of the invention

[0004] The object of the present invention is to provide a CuInS2-BiFeO3 composite piezoelectric photocatalyst and a preparation method thereof, and to apply the composite piezoelectric photocatalytic hydrogen production, which has high piezoelectric photocatalytic activity.

[0005] The present invention adopts the following technical solutions:

[0006] A CuInS2-BiFeO3 composite piezoelectric photocatalyst, characterized in that its preparation method is as follows:

[0007] (1) Dispersing an appropriate amount of positively charged CuInS2 in a certain amount of isopropanol, and ultrasonically dispersing to obtain a black suspension;

[0008] (2) adding an appropriate amount of BiFeO3 to the above black suspension, stirring at a certain temperature to completely evaporate the solvent, washing the obtained product with deionized water and ethanol respectively, and vacuum drying to obtain a CuInS2-BiFeO3 composite piezoelectric photocatalyst;

[0009] In step (1) of the present invention, the CuInS2 modified with positive charge is characterized in that the preparation method comprises the following steps:

[0010] First, CuInS2 was prepared based on the hydrothermal method: 0.5~2 mmol copper chloride was dissolved in 10~50 mL ethanol to form solution A, 0.5~2 mmol indium nitrate was dissolved in 10~50 mL ethanol to form solution B, and the two solutions A and B were mixed and stirred for 1 hour; then 1~5 mmol thiourea and 0.1~0.5 mmol oxalic acid were added to obtain a white suspension; the suspension was transferred into a hydrothermal reactor and heated at 100~300 ℃ for 10~20 hours; after the reaction was completed, the black precipitate was collected, washed with deionized water and ethanol, and then dried to obtain CuInS2 nanosheets;

[0011] Subsequently, a surfactant was used to prepare positively charged CuInS2: 0.2 mmol of the prepared CuInS2 was weighed and dispersed in deionized water, 0-0.5 mmol of hexadecyltrimethylammonium bromide was added, and the mixture was stirred for 3 h and then filtered and washed to obtain positively charged CuInS2.

[0012] In step (2) of the present invention, the BiFeO3 is characterized in that the preparation method comprises the following steps:

[0013] 2-10 mmol bismuth nitrate was dissolved in 50-200 mL ethylene glycol to obtain solution A, 2-10 mmol ferric chloride was dissolved in 50-200 mL water to obtain solution B, then the two solutions A and B were mixed and stirred, 5-100 mL concentrated ammonia was added to adjust the pH to 10-11, and the precipitate was collected by centrifugation after reacting for 5-60 min; the obtained precipitate was placed in 1-10 M sodium hydroxide solution and transferred to a hydrothermal autoclave, and reacted at 100-300 °C for 12-72 h; after the reaction was completed, it was naturally cooled, centrifuged, and dried to obtain BiFeO3 nanosheets.

[0014] In step (2), the stirring temperature is 70-100 °C.

[0015] In addition, the present invention also provides an application of the CuInS2-BiFeO3 piezoelectric photocatalyst prepared by the preparation method in piezoelectric photocatalytic hydrogen production.

[0016] Furthermore, the CuInS2-BiFeO3 piezoelectric photocatalyst was ultrasonically dispersed in an aqueous solution containing a sacrificial agent, nitrogen was introduced into the solution to fully deoxygenate it, and a catalytic reaction was carried out under the combined action of visible light and ultrasound.

[0017] The significant advantages of the present invention are:

[0018] The present invention uses electrostatic self-assembly technology to modify CuInS2 with modified surface charge onto BiFeO3 nanosheets to prepare a CuInS2-BiFeO3 composite piezoelectric photocatalyst. Under the combined action of visible light and ultrasound, a large number of photogenerated electrons on BiFeO3 recombine with photogenerated holes in CuInS2, thereby promoting the photogenerated electrons in CuInS2 to react with H + At the same time, the good piezoelectricity of BiFeO3 can generate a polarization electric field under the condition of mechanical vibration, further promoting the transfer of charges between material interfaces and improving the efficiency of photocatalytic reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 X-ray diffraction patterns of CuInS2, positively charged CuInS2, BiFeO3 and CuInS2-BiFeO3 composite piezoelectric photocatalysts prepared in Examples 1 to 4.

[0020] Figure 2 This is a transmission electron microscope image of CuInS2 prepared by Example 1 of the present invention.

[0021] Figure 3 This is a transmission electron microscopy image of the positively charged modified CuInS2 prepared in Example 2 of the present invention.

[0022] Figure 4 This is a transmission electron microscope image of BiFeO3 prepared by Example 3 of the present invention.

[0023] Figure 5 This is a transmission electron microscope image of the CuInS2-BiFeO3 composite piezoelectric photocatalyst prepared in Example 4.

[0024] Figure 6 Zeta potential diagrams of CuInS2 prepared in Examples 1 to 3, CuInS2 modified with positive charge, and BiFeO3.

[0025] Figure 7 The piezoelectric photocatalytic hydrogen production performance diagram of CuInS2, BiFeO3 and CuInS2-BiFeO3 prepared in Examples 1, 2, and 4. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0027] Embodiment 1

[0028] A method for preparing a CuInS2 photocatalyst comprises the following steps:

[0029] 1 mmol of copper chloride was dissolved in 20 mL of ethanol to obtain solution A, and 1 mmol of indium nitrate was dissolved in 20 mL of ethanol to obtain solution B. The two solutions were mixed and stirred for 1 h. Then 4 mmol of thiourea and 0.18 mmol of oxalic acid were added to obtain a white suspension. The suspension was transferred into a hydrothermal reactor and heated at 200 °C for 12 h. After the reaction was completed, the black precipitate was collected, washed with deionized water and ethanol, and then dried to obtain CuInS2 nanosheets. Its X-ray diffraction spectrum is shown in FIG. Figure 1 As shown by the middle curve a; its morphology is shown in Figure 2 As shown; Zeta potential diagram as Figure 6 As shown in bar graph a.

[0030] The following is an application example of using the catalyst prepared in this embodiment for piezoelectric-photocatalytic hydrogen production:

[0031] Weigh 20 mg of the above CuInS2 and place it in a quartz reactor filled with 50 mL Na2S / Na2SO3 solution as a sacrificial agent; seal the reactor and introduce nitrogen for deoxygenation for 30 min under magnetic stirring; then, piezoelectric photocatalytic hydrogen production was carried out under 850 r / min magnetic stirring, 300 W light irradiation, and 40 kHz, 80 W ultrasound, and 1 mL of gas was extracted every 1 h and analyzed using a gas chromatograph; the calculated results are shown in Figure 7 As shown in bar graph a.

[0032] Embodiment 2

[0033] A method for preparing a positively charged CuInS2 photocatalyst comprises the following steps:

[0034] 0.2 mmol of CuInS2 prepared in Example 1 was dispersed in deionized water, and 0.2 mmol of hexadecyltrimethylammonium bromide was added. After stirring for 3 h, the mixture was filtered and washed to obtain positively charged CuInS2. Its X-ray diffraction spectrum is shown in FIG. Figure 1 As shown in the middle curve b; its morphology is as follows Figure 3 As shown; Zeta potential diagram as Figure 6 As shown in bar graph b.

[0035] Embodiment 3

[0036] A preparation method of BiFeO3 piezoelectric photocatalyst

[0037] 5 mmol bismuth nitrate was dissolved in 20 mL ethylene glycol, and then stirred vigorously after ultrasonic dispersion to dissolve it to obtain solution A; 5 mmol ferric chloride was dissolved in 100 mL water to obtain solution B; solution B was added dropwise to solution A and stirred evenly, and 5-100 mL concentrated ammonia water was added to adjust the pH to 11, and the reaction was carried out for 30 min and then the precipitate was collected by centrifugation; the obtained precipitate was placed in 5 M sodium hydroxide solution and transferred to a hydrothermal autoclave, and reacted at 180 ° C for 48 h; after the reaction was completed, it was naturally cooled, centrifuged, and dried to obtain BiFeO3 nanosheets; its X-ray diffraction spectrum is shown as follows Figure 1 As shown by the curve c in the figure; its morphology is as follows Figure 4 As shown; Zeta potential diagram as Figure 6 As shown in bar graph c.

[0038] The prepared BiFeO3 was subjected to a piezoelectric-photocatalytic experiment under the same conditions as in Example 1, and the results of the piezoelectric-photocatalytic hydrogen production are shown in Figure 7 As shown in bar graph b.

[0039] Embodiment 4

[0040] A preparation method of CuInS2-BiFeO3 piezoelectric photocatalyst

[0041] 100 mg of the positively charged CuInS2 prepared in Example 2 was dispersed in 40 mL of isopropanol and ultrasonically dispersed to obtain a black suspension. 15 mg of BiFeO3 prepared in Example 3 was added to the suspension and stirred at 80 °C until the solvent was completely evaporated. The obtained product was washed with deionized water and ethanol respectively and vacuum dried to obtain CuInS2-BiFeO3. Its X-ray diffraction spectrum is shown in FIG. Figure 1 As shown by the middle curve d; its morphology is as follows Figure 5 shown.

[0042] The prepared CuInS2-BiFeO3 was subjected to piezoelectric-photocatalytic experiment under the same conditions as in Example 1. The piezoelectric-photocatalytic hydrogen production results are shown in Figure 7 As shown in bar graph c.

[0043] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the art can easily think of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications and substitutions should all be included in the protection scope of the present invention.

Claims

1. Application of CuInS2-BiFeO3 piezoelectric photocatalyst in piezoelectric photocatalytic hydrogen production, characterized in that: The preparation method of the piezoelectric photocatalyst comprises the following steps: (1) Dispersing an appropriate amount of positively charged CuInS2 in a certain amount of isopropanol, and ultrasonically dispersing to obtain a black suspension; (2) adding an appropriate amount of BiFeO3 to the above black suspension, stirring at a certain temperature to completely evaporate the solvent, washing the obtained product with deionized water and ethanol respectively, and vacuum drying to obtain a CuInS2-BiFeO3 piezoelectric photocatalyst; The preparation method of CuInS2 modified with positive charge includes the following steps: weighing 0.2 mmol of prepared CuInS2 and dispersing it in deionized water, adding 0-0.5 mmol of hexadecyltrimethylammonium bromide, the amount of hexadecyltrimethylammonium bromide added is not 0, stirring for 3 h and then filtering and washing to obtain CuInS2 modified with positive charge.

2. The use according to claim 1, characterized in that: In step (1), the preparation method of the positively charged CuInS2 comprises the following steps: first, dissolving 0.5-2 mmol copper chloride in 10-50 mL ethanol to form solution A, dissolving 0.5-2 mmol indium nitrate in 10-50 mL ethanol to form solution B, mixing solutions A and B and stirring for 1 h; then adding 1-5 mmol thiourea and 0.1-0.5 mmol oxalic acid to obtain a white suspension; transferring the suspension into a hydrothermal reactor and heating it at 100-300 °C for 10-20 h; after the reaction is completed, collecting the black precipitate, washing it with deionized water and ethanol, and drying it to obtain CuInS2 nanosheets.

3. The use according to claim 1, characterized in that: In step (2), the preparation method of BiFeO3 comprises the following steps: dissolving 2-10 mmol bismuth nitrate in 50-200 mL ethylene glycol to obtain solution A, dissolving 2-10 mmol ferric chloride in 50-200 mL water to obtain solution B, then mixing solutions A and B and stirring, adding 5-100 mL concentrated ammonia water to adjust the pH to 10-11, reacting for 5-60 min and collecting the precipitate by centrifugation; placing the obtained precipitate in 1-10 M sodium hydroxide solution and transferring it to a hydrothermal autoclave, reacting at 100-300 °C for 12-72 h; after the reaction is completed, naturally cooling, centrifuging and drying to obtain BiFeO3 nanosheets.

4. The use according to claim 1, characterized in that: In step (2), the stirring temperature is 70-100 °C.

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