Preparation method and application of ZnSnO3@rGO piezoelectric photocatalytic material

Abstract

The present invention belongs to the field of semiconductor photocatalysis, and specifically relates to a preparation method and application of a ZnSnO3@rGO composite piezoelectric photocatalyst. ZnSnO3 nanoplates synthesized by a hydrothermal method are dispersed in deionized water, and rGO aqueous dispersion is added dropwise for hydrothermal treatment, and a ZnSnO3@rGO composite piezoelectric photocatalyst is obtained by a simple electrostatic adsorption method. Since ZnSnO3 has piezoelectricity, the polarization electric field caused by external force causes the conduction band edge to tilt toward a more negative potential, breaking through the thermodynamic limitation that the conduction band of ZnSnO3 is not conducive to hydrogen production; in addition, based on the piezoelectric field, the Schottky barrier between rGO and ZnSnO3 further promotes the separation of photogenerated carriers, realizes the coupling of light and mechanical stress, and greatly broadens its application prospects in the field of hydrogen production. The present invention solves the problems that the existing composite piezoelectric photocatalyst is complicated to prepare, has high cost, and fails to fully utilize the piezoelectric photocatalytic activity of ZnSnO3.

Description

[0001] The present invention relates to the technical field of piezoelectric photocatalytic materials, and more specifically to a ZnSnO3@rGO piezoelectric photocatalytic material and a preparation method and application thereof. Background Art

[0002] In recent years, the growing demand for energy and the environmental problems associated with it have forced humans to develop and utilize sustainable clean energy to replace traditional fuels. Hydrogen energy has high energy density and is harmless to the environment, and has been considered an important alternative to traditional energy. Therefore, using sunlight to decompose water into H2 and O2 through photocatalytic technology has broad prospects in solving energy and environmental problems. However, the rapid recombination of photogenerated carriers in photocatalysts limits their efficient application. In order to further improve the photocatalytic efficiency, researchers have proposed piezoelectric photocatalysis, which uses the polarization electric field formed inside the piezoelectric material when it is subjected to external mechanical force to promote the effective separation of photogenerated carriers in the photocatalytic process, thereby improving the photocatalytic performance.

[0003] Zinc stannate (ZnSnO3), as a piezoelectric semiconductor, has been widely used in the fields of photocatalytic pollution degradation, self-powered photodetectors, gas sensors, etc. due to its outstanding piezoelectric properties and high conductivity. However, since the conduction band edge of ZnSnO3 is around -0.13 eV, it is not conducive to H + Reduction reaction, which limits the application of ZnSnO3 in photocatalytic hydrogen evolution. Fortunately, the polarization electric field caused by external force can cause the conduction band edge to tilt toward a more negative potential, making the conduction band of ZnSnO3 thermodynamically favorable for hydrogen production, while promoting the separation of photogenerated carriers and realizing the coupling of light and mechanical stress, which is expected to greatly broaden its application prospects in the field of hydrogen production.

[0004] In addition, excellent conductivity is conducive to enhancing the induced potential on the surface of piezoelectric semiconductors, thereby inducing more charges to drive redox reactions during piezoelectric catalysis. Reduced graphene oxide (rGO) has high conductivity and electron mobility. Combining it with ZnSnO3 can not only improve the surface conductivity of ZnSnO3, but also form a Schottky barrier between rGO and ZnSnO3 by forming a semiconductor / rGO Schottky heterostructure, reducing the recombination of photoinduced electron-hole pairs. Summary of the invention

[0005] The purpose of the present invention is to provide a ZnSnO3@rGO composite piezoelectric photocatalyst and a preparation method thereof, and to apply the same to piezoelectric photocatalytic hydrogen production, which has high piezoelectric photocatalytic activity.

[0006] The present invention adopts the following technical solutions:

[0007] A ZnSnO3@rGO composite piezoelectric photocatalyst, characterized in that its preparation method is as follows:

[0008] (1) Dispersing an appropriate amount of ZnSnO3 nanosheets in a certain amount of deionized water, and ultrasonically dispersing to obtain a white suspension;

[0009] (2) Add an appropriate amount of rGO dispersion dropwise to the above white suspension, stir at room temperature, hydrothermally treat the resulting black suspension at a certain temperature, wash the resulting product with deionized water, and vacuum dry to obtain ZnSnO3@rGO;

[0010] In step (1) of the present invention, the ZnSnO3 nanosheets are characterized in that the preparation method comprises the following steps: weighing 0.1-0.5 mmol zinc acetate and dissolving it in 20 mL deionized water at room temperature, and the solution obtained after sufficient stirring is recorded as solution A; weighing 0.1-0.5 mmol sodium stannate and dissolving it in 20 mL deionized water at room temperature, and the solution obtained after sufficient stirring is recorded as solution B; mixing and stirring the prepared solution A and solution B, and obtaining suspension A after sufficient reaction; wherein the molar ratio of zinc acetate to sodium stannate is 1:0.5-1.5; transferring the suspension A to a reaction kettle, placing it in an oven at 180-260°C for hydrothermal reaction for 12-36 hours, and then naturally cooling it to room temperature, washing the obtained precipitate with deionized water and anhydrous ethanol alternately for several times, transferring it to an oven at 60-80°C for drying for 12 hours, and obtaining ZnSnO3 nanosheets with excellent piezoelectric photocatalytic properties;

[0011] In step (2) of the present invention, the rGO dispersion is characterized in that, before being dropwise added to the white suspension in step (1), it is treated with a cell disruptor for 0 to 60 minutes to obtain rGO with different sheet sizes;

[0012] In step (2), the hydrothermal treatment temperature is 130-160 °C, the reaction time is 1-5 h, and the mass ratio of ZnSnO3 to rGO is 1:0.005-0.04.

[0013] In addition, the present invention also provides an application of the ZnSnO3@rGO piezoelectric photocatalyst prepared by the preparation method in piezoelectric photocatalytic hydrogen production.

[0014] Furthermore, the ZnSnO3@rGO piezoelectric photocatalyst was ultrasonically dispersed in an aqueous solution containing a sacrificial agent, nitrogen was introduced to fully deoxygenate the solution, and after photodeposition of 1wt% Pt as a co-catalyst, the catalytic reaction was carried out under the combined action of visible light and ultrasound.

[0015] The significant advantages of the present invention are:

[0016] (1) The ZnSnO3@rGO composite piezoelectric photocatalyst prepared by the present invention has good crystallinity, simple operation and low preparation cost;

[0017] (2) The electrostatic adsorption method used in the present invention to prepare the ZnSnO3@rGO composite piezoelectric photocatalyst is simple and has undemanding conditions. In addition, ultrasonic crushing can break a large area of ​​rGO into a smaller area, which can better match the size of ZnSnO3.

[0018] (3) The ZnSnO3@rGO composite piezoelectric photocatalyst prepared in the present invention has piezoelectric photocatalytic performance. Under the assistance of ultrasound, the piezoelectric effect can be triggered to generate a polarization electric field, which promotes the inclination of the energy band edge and effectively separates the photoinduced carriers, further improving the piezoelectric photocatalytic efficiency of the catalyst;

[0019] (4) The ZnSnO3@rGO composite piezoelectric photocatalyst prepared by the present invention can form a semiconductor / rGO Schottky heterostructure between rGO and ZnSnO3 to reduce the recombination of photoinduced electron-hole pairs;

[0020] (5) The ZnSnO3@rGO composite piezoelectric photocatalyst prepared in the present invention realizes the simultaneous utilization of mechanical energy and light energy, providing a new way to enhance photocatalytic effect by multi-field coupling. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 X-ray diffraction patterns of ZnSnO3 and ZnSnO3@rGO composite piezoelectric photocatalysts prepared in Examples 1 to 5.

[0022] Figure 2 It is a scanning electron microscope image of ZnSnO3 prepared by Example 1 of the present invention.

[0023] Figure 3 This is a scanning electron microscope image of ZnSnO3@rGO prepared in Example 2 of the present invention.

[0024] Figure 4 It is a piezoelectric photocatalytic hydrogen production performance diagram of ZnSnO3 and ZnSnO3@rGO composite piezoelectric photocatalysts prepared by Examples 1 to 5 of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0026] Embodiment 1

[0027] A method for preparing a ZnSnO3 composite piezoelectric photocatalyst comprises the following steps:

[0028] 0.1 mmol zinc acetate was weighed and dissolved in 20 mL deionized water at room temperature, and the solution obtained after sufficient stirring was recorded as solution A; 0.1 mmol sodium stannate was weighed and dissolved in 20 mL deionized water at room temperature, and the solution obtained after sufficient stirring was recorded as solution B; the prepared solution A and solution B were mixed and stirred, and suspension A was obtained after sufficient reaction. The suspension A was transferred to a reactor, placed in a 230 ° C oven for hydrothermal reaction for 24 h, and then naturally cooled to room temperature. The obtained precipitate was washed alternately with deionized water and anhydrous ethanol for several times, and transferred to a 60 ° C oven for drying for 12 h to obtain ZnSnO3 nanosheets with excellent piezoelectric photocatalytic properties; its X-ray diffraction spectrum is shown as follows Figure 1 As shown by the middle curve a, its morphology is as follows Figure 2 shown.

[0029] The following is an application example of using the catalyst prepared in this embodiment for piezoelectric photocatalytic hydrogen production:

[0030] Weigh 20 mg of the above ZnSnO3 and place it in a quartz reactor filled with 40 mL of deionized water and 10 mL of methanol as a sacrificial agent; add 5.3 μL of H 14 Cl6O6Pt·6H2O (0.1 g / mL) was used as a co-catalyst and ultrasonically dispersed for 15 min. The reactor was sealed and nitrogen was introduced for deoxygenation for 30 min under magnetic stirring. A 300 W Xe lamp was used as the light source to complete the photodeposition of the co-catalyst Pt on the surface of ZnSnO3. Next, piezoelectric photocatalytic hydrogen production was carried out under 850 r / min magnetic stirring, 300 W light irradiation, and 40 kHz, 80 W ultrasound. 1 mL of gas was extracted every 1 h and analyzed using a gas chromatograph. The calculated results are shown in Figure 4 As shown in the middle curve a.

[0031] Embodiment 2

[0032] A method for preparing a ZnSnO3@rGO composite piezoelectric photocatalyst comprises the following steps:

[0033] 160 mg of the ZnSnO3 nanosheets obtained in Example 1 were dispersed in 30 mL of deionized water, and were uniformly dispersed by ultrasonic and magnetic stirring at room temperature; 0.8 mL of a 2 mg / mL rGO dispersion that had been crushed by a cell crusher for 30 min was added dropwise during stirring; the mixed suspension was stirred for 30 min, transferred to a 50 mL polytetrafluoroethylene sealed autoclave, and hydrothermally reacted at 150 °C for 3 h; washed three times with deionized water, and the obtained gray precipitate was placed in a vacuum drying oven at 60 °C and vacuum dried for 12 h to obtain a ZnSnO3@rGO (1 wt%) composite piezoelectric photocatalyst; its X-ray diffraction spectrum is shown in Figure 1As shown by the curve c in the figure, its morphology is as follows Figure 3 shown.

[0034] The following is an application example of using the catalyst prepared in this embodiment for piezoelectric photocatalytic hydrogen production:

[0035] Weigh 20 mg of the above ZnSnO3@rGO (1 wt%) and place it in a quartz reactor filled with 40 mL of deionized water and 10 mL of methanol as a sacrificial agent; add 5.3 μL of H 14 Cl6O6Pt·6H2O (0.1 g / mL) was used as a co-catalyst and ultrasonically dispersed for 15 min. The reactor was sealed and nitrogen was introduced for deoxygenation for 30 min under magnetic stirring. A 300 W Xe lamp was used as the light source to complete the photodeposition of the co-catalyst Pt on the surface of ZnSnO3@rGO (1 wt%). Next, piezoelectric photocatalytic hydrogen production was carried out under 850 r / min magnetic stirring, 300 W light irradiation, and 40 kHz, 80 W ultrasound. 1 mL of gas was extracted every 1 h and analyzed using a gas chromatograph. The calculated results are shown in Figure 4 As shown in the middle curve c.

[0036] Embodiment 3

[0037] The same parts of this embodiment as those of the third embodiment are not described in detail, except that:

[0038] The amount of rGO dispersion added was 0.4 mL, and ZnSnO3@rGO (0.5 wt%) was obtained; its X-ray diffraction spectrum is shown in Figure 1 As shown in the middle curve b.

[0039] The prepared ZnSnO3@rGO (0.5 wt%) was subjected to a piezoelectric photocatalytic experiment under the same conditions as in Example 2. The results of the piezoelectric photocatalytic hydrogen production are shown in Figure 4 As shown in the middle curve b.

[0040] Embodiment 4

[0041] The same parts of this embodiment as those of the third embodiment are not described in detail, except that:

[0042] The amount of rGO dispersion added was 1.6 mL, and ZnSnO3@rGO (2 wt%) was obtained; its X-ray diffraction spectrum is shown in Figure 1 As shown in the middle curve d.

[0043] The prepared ZnSnO3@rGO (2 wt%) was subjected to a piezoelectric photocatalytic experiment under the same conditions as in Example 2. The results of the piezoelectric photocatalytic hydrogen production are shown in Figure 4 As shown in the middle curve d.

[0044] Embodiment 5

[0045] The same parts of this embodiment as those of the third embodiment are not described in detail, except that:

[0046] The amount of rGO dispersion added was 3.2 mL, and ZnSnO3@rGO (4 wt%) was obtained; its X-ray diffraction spectrum is shown in Figure 1 As shown in the middle curve e.

[0047] The prepared ZnSnO3@rGO (4 wt%) was subjected to a piezoelectric photocatalytic experiment under the same conditions as in Example 2. The results of the piezoelectric photocatalytic hydrogen production are shown in Figure 4 As shown in the middle curve e.

[0048] 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 ZnSnO3@rGO piezoelectric photocatalyst in piezoelectric photocatalytic hydrogen production, characterized in that: The ZnSnO3@rGO piezoelectric photocatalyst is ultrasonically dispersed in an aqueous solution containing a sacrificial agent, nitrogen is introduced to fully deoxygenate the solution, 1wt% Pt is photodeposited as a co-catalyst, and then a catalytic hydrogen production reaction is carried out under the combined action of visible light and ultrasound; the preparation method of the ZnSnO3@rGO piezoelectric photocatalyst comprises the following steps: (1) Dispersing an appropriate amount of ZnSnO3 nanosheets in a certain amount of deionized water, and ultrasonically dispersing to obtain a white suspension; (2) An appropriate amount of rGO dispersion was added dropwise to the above white suspension and stirred at room temperature. The resulting black suspension was hydrothermally treated at a certain temperature. The product was washed with deionized water and vacuum dried to obtain ZnSnO3@rGO.

2. The use according to claim 1, characterized in that: In step (1), the method for preparing ZnSnO3 nanosheets comprises the following steps: weighing 0.1-0.5 mmol zinc acetate and dissolving it in 20 mL deionized water at room temperature, and stirring the solution obtained is recorded as solution A; weighing 0.1-0.5 mmol sodium stannate and dissolving it in 20 mL deionized water at room temperature, and stirring the solution obtained is recorded as solution B; mixing and stirring the prepared solution A and solution B, and obtaining suspension A after sufficient reaction; wherein the molar ratio of zinc acetate to sodium stannate is 1:0.5-1.5; transferring suspension A to a reactor, placing it in an oven at 180-260 °C for hydrothermal reaction for 12-36 h, and then naturally cooling it to room temperature, washing the obtained precipitate alternately with deionized water and anhydrous ethanol for several times, transferring it to an oven at 60-80 °C for drying for 12 h, and obtaining a white powder, i.e., obtaining ZnSnO3 nanosheets with excellent piezoelectric photocatalytic properties.

3. The use according to claim 1, characterized in that: In step (2), the rGO dispersion is treated with a cell disruptor for 0 to 60 min (excluding the endpoint value of 0 min) before being dropwise added to the white suspension in step (1) to obtain rGO with different sheet sizes.

4. The use according to claim 1, characterized in that: In step (2), the hydrothermal treatment temperature is 130-160 °C and the reaction time is 1-5 h.

5. The use according to claim 1, characterized in that: In step (2), the mass ratio of ZnSnO3 to rGO is 1:0.005~0.04.

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