A CSB / rGO composite photocatalyst and its preparation method and application

Abstract

The present invention belongs to the field of energy and environmental catalysis technology, and specifically relates to a CSB / rGO composite photocatalyst, its preparation method and application. The preparation method of the CSB / rGO composite photocatalyst includes the following steps: S1, dissolving a tin salt in a hydrobromic acid solution, stirring, and then adding a cesium salt to obtain a mixed solution, and washing, centrifuging, and drying the product after the mixed solution undergoes a hydrothermal reaction to obtain CSB; S2, dispersing CSB and graphene oxide in a saturated HBr and H3PO2 mixed solution, and performing photoreduction to obtain a CSB / rGO composite photocatalyst. The present invention obtains a CSB / rGO composite photocatalyst by compounding Cs2SnBr6 (CSB) with rGO. A fast charge transfer channel is established between CSB and rGO, which solves the defect of poor separation efficiency of photogenerated electron-hole pairs in tin-based perovskites. The improvement of the carrier separation efficiency of the CSB / rGO composite photocatalyst enables it to have excellent photocatalytic HMF oxidation performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy and environmental catalysis, and specifically relates to a CSB / rGO composite photocatalyst and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Biomass materials are a renewable carbon resource with abundant reserves in nature. The efficient utilization of biomass resources will inevitably reduce the consumption and dependence on petroleum and fossil fuels. Biomass-derived 5-hydroxymethylfurfural (HMF) is considered to be a bridge connecting biomass raw materials with alternative fuels, chemicals and materials. It can be selectively oxidized to various furan products. Traditional oxidation methods of HMF usually require precious metal catalysts, toxic and corrosive chemical oxidants and harsh reaction conditions, and are accompanied by dangerous operating conditions and high energy consumption. Solar-driven photocatalytic reactions use green oxygen to provide a potential strategy for achieving the selective oxidation of HMF. However, the efficiency of photocatalytic selective oxidation of HMF is limited by the lack of efficient and stable photocatalysts.

[0004] In recent years, halide perovskites have attracted considerable attention due to their excellent optoelectronic properties, such as large optical coefficients, tunable band gaps, and high carrier mobility. However, the high toxicity and bioaccumulation of classic lead-based perovskites have limited their development in photocatalysis. Researchers have gradually turned their attention to lead-free metal halide perovskites. Among them, tin-based perovskites are considered ideal alternatives to lead-based perovskites, as lead and tin are both carbon group elements and share similarities in the ns2 electron configurations of their outermost s orbitals. As low-toxic and stable photocatalytic materials, tin-based perovskites (Sn(+4)) have shown great potential in photocatalytic reduction reactions such as CO2 reduction and photocatalytic hydrogen production. However, the numerous defects on the perovskite surface result in poor separation efficiency of photogenerated electron-hole pairs, resulting in poor photocatalytic oxidation ability of tin-based perovskites, limiting their application in photocatalytic HMF oxidation. Summary of the Invention

[0005] To address the deficiencies of the prior art, the present invention provides a CSB / rGO composite photocatalyst, its preparation method, and its application. This invention combines Cs2SnBr6 (CSB) with rGO to create a CSB / rGO composite photocatalyst. A rapid charge transfer channel is established between CSB and rGO, improving the poor separation efficiency of photogenerated electron-hole pairs in tin-based perovskites. This improved carrier separation efficiency of the CSB / rGO composite photocatalyst enables it to exhibit excellent photocatalytic HMF oxidation performance.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a CSB / rGO composite photocatalyst, comprising the following steps:

[0008] S1. Dissolving a tin salt in a hydrobromic acid solution, stirring, and then adding a cesium salt to obtain a mixed solution. After the mixed solution undergoes a hydrothermal reaction, the product is washed, centrifuged, and dried to obtain CSB;

[0009] S2. CSB and graphene oxide are dispersed in a saturated HBr and H3PO2 mixed solution and photoreduced to obtain a CSB / rGO composite photocatalyst.

[0010] In a second aspect, the present invention provides a CSB / rGO composite photocatalyst obtained by the preparation method described in the first aspect.

[0011] In a third aspect, the present invention provides an application of the CSB / rGO composite photocatalyst described in the second aspect in the photocatalytic oxidation of 5-hydroxymethylfurfural.

[0012] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0013] This method utilizes an in-situ photoreduction method to deposit rGO on an all-inorganic tin-based halide perovskite (CSB) to create a CSB / rGO composite photocatalyst. This method establishes a rapid charge transfer channel between CSB and rGO, improving carrier separation efficiency. The preparation method offers advantages such as simplicity, low cost, and high yield.

[0014] The main active oxygen species in the photocatalytic selective oxidation of HMF by CSB / rGO composite catalyst is superoxide radical (·O2 - ) and singlet oxygen ( 1 A conversion of greater than 99.5% and a product selectivity of 88% were achieved in the solar-driven photocatalytic oxidation of HMF. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0016] Figure 1 Raman spectra of the CSB / rGO composite photocatalyst (Cs2SnBr6 / rGO) of Example 1, Cs2SnBr6 of Comparative Example 1, and GO of Comparative Example 2;

[0017] Figure 2 These are the SEM images, EDS Mapping images, and TEM images of the CSB / rGO composite photocatalyst of Example 1, where a is an SEM image, b is an EDS Mapping image of the Cs element, c is an EDS Mapping image of the Sn element, d is an EDS Mapping image of the C element, e is an EDS Mapping image of the O element, f is a TEM image, and g is a high-magnification TEM image;

[0018] Figure 3 XPS spectra of the CSB / rGO composite photocatalyst (Cs2SnBr6 / rGO) of Example 1, the Cs2SnBr6 of Comparative Example 1, and the GO of Comparative Example 2, where a is the Cs 3d spectrum, b is the Sn 3d spectrum, c is the Br 3d spectrum, d is the C1s spectrum, e is the O1s spectrum, and f is the XPS total spectrum;

[0019] Figure 4 a is the reaction equation for photocatalytic HMF oxidation, b is the activity comparison of photocatalytic HMF oxidation under different conditions using Cs2SnBr6 / 1.6%rGO as catalyst, and c is a comparison of the conversion rate (left column) and selectivity (right column) of photocatalytic HMF oxidation of Cs2SnBr6, Cs2SnBr6 / 0.8%rGO, Cs2SnBr6 / 1.6%rGO and Cs2SnBr6 / 2.6%rGO;

[0020] Figure 5 Single particle spectra of Cs2SnBr6 and the CSB / rGO composite photocatalyst of Example 1, wherein a is a single particle imaging photograph of Cs2SnBr6 (embedded points 1-3 in the figure are test points), b is the PL spectrum of Cs2SnBr6, c is the PL lifetime diagram of Cs2SnBr6, d is a single particle imaging photograph of CSB / rGO (embedded points 1-6 in the figure are test points), e is the PL spectrum of CSB / rGO, and f is the PL lifetime diagram of CSB / rGO;

[0021] Figure 6a is a comparison of the photocatalytic HMF oxidation conversion rate using Cs2SnBr6 / 1.6% rGO as a catalyst with the addition of scavengers benzoquinone (BQ), silver nitrate (AgNO3), 4-chloro-2-nitrophenol (CN), and sodium formate (HCOONa) and without adding scavengers (Control); b is the signal detection result of superoxide radicals of the CSB / rGO composite photocatalyst (Cs2SnBr6 / rGO) of Example 1 and the Cs2SnBr6 of Comparative Example 1 under dark and light conditions; c is the signal detection result of singlet oxygen of the CSB / rGO composite photocatalyst (Cs2SnBr6 / rGO) of Example 1 and the Cs2SnBr6 of Comparative Example 1 under dark and light conditions; d is the detection of hydrogen peroxide before and after the reaction of the photocatalytic system containing the CSB / rGO composite photocatalyst of Example 1;

[0022] Figure 7 Mechanism diagram of photocatalytic HMF oxidation over CSB / rGO composite photocatalyst. DETAILED DESCRIPTION

[0023] A first exemplary embodiment of the present invention is a method for preparing a CSB / rGO composite photocatalyst, comprising the following steps:

[0024] S1. Dissolving a tin salt in a hydrobromic acid solution, stirring, and then adding a cesium salt to obtain a mixed solution. After the mixed solution undergoes a hydrothermal reaction, the product is washed, centrifuged, and dried to obtain CSB;

[0025] S2. CSB and graphene oxide are dispersed in a saturated HBr and H3PO2 mixed solution and photoreduced to obtain a CSB / rGO composite photocatalyst.

[0026] In one or more examples of this embodiment, the tin salt includes one or more of tin acetate and tin bromide, the cesium salt includes one or more of cesium acetate and cesium bromide, and the molar ratio of the tin salt to the cesium salt is 1:2.

[0027] In one or more examples of this embodiment, in step S1, the hydrothermal reaction temperature is 150-170° C., and the hydrothermal time is 2-4 hours.

[0028] In one or more examples of this embodiment, in step S1, isopropyl alcohol is used for washing, and the drying temperature is 50-70° C. and the drying time is 5-7 hours.

[0029] In one or more examples of this embodiment, the mass ratio of CSB to graphene oxide is 125:1-3.25.

[0030] In one or more examples of this embodiment, the graphene oxide is obtained by oxidizing flake graphite by the Hummers method.

[0031] In one or more examples of this embodiment, in step S2, dispersion is performed by ultrasound and stirring, the ultrasound time is 30-60 minutes, and the stirring time is 30-60 minutes.

[0032] In one or more examples of this embodiment, in step S2, the photoreduction is performed using a xenon lamp equipped with an AM1.5 filter, and the power of the xenon lamp is 300-350W.

[0033] The second typical embodiment of the present invention is a CSB / rGO composite photocatalyst, characterized in that it is obtained by the preparation method described in the first typical embodiment.

[0034] A third typical embodiment of the present invention is the use of the CSB / rGO composite photocatalyst described in the second typical embodiment in the photocatalytic oxidation of 5-hydroxymethylfurfural.

[0035] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0036] Example 1

[0037] Preparation of CSB

[0038] Dissolve 0.2368 g of tin acetate in 30 mL of 48% hydrobromic acid solution, stir for 20 minutes, then add 0.3839 g of cesium acetate and continue stirring. The mixture is then transferred to a 50 mL reactor and hydrothermally reacted at 160°C for 2 hours. After cooling the reactor, the resulting product is washed with isopropanol, centrifuged, and dried at 60°C for 6 hours to obtain CSB.

[0039] Preparation of graphene oxide (GO)

[0040] Under constant stirring in an ice-water bath, 1g of flake graphite was added to a 200mL beaker containing 46mL of the strong acid H2SO4. 1g of NaNO3 was then added, and 6g of KMnO4 was slowly added to the beaker to obtain a mixture. The mixture was transferred to a 38°C environment and stirred for 30 hours for oxidation and further intercalation. 40mL of deionized water was slowly added to the mixture at room temperature. After stirring for 1 hour, 80mL of deionized water was added to dilute the mixture, and the mixture was stirred at 95°C for 1 hour. Next, 6mL of H2O2 was added dropwise, and the color of the solution turned golden yellow, indicating that graphene oxide had been successfully synthesized. The resulting solution was centrifuged and washed with 10% HCl and deionized water until the pH of the supernatant reached 7. Finally, the resulting graphene oxide powder was freeze-dried to obtain GO.

[0041] Preparation of CSB / rGO composite photocatalyst

[0042] 200 mg of Cs2SnBr6 was added to 15 mL of a saturated HBr and H3PO2 solution and stirred uniformly. 3.2 mg of graphene oxide was added to this mixture, followed by sonication for 30 minutes and stirring for 30 minutes to achieve uniform dispersion. The mixture was then photoreduced using a 300 W xenon lamp equipped with an AM1.5 filter. The resulting CSB / rGO composite photocatalyst was designated Cs2SnBr6 / 1.6% rGO.

[0043] Example 2

[0044] The difference from Example 1 is that 1.6 mg of graphene oxide was added, and the obtained CSB / rGO composite photocatalyst was recorded as Cs2SnBr6 / 0.8% rGO.

[0045] Example 3

[0046] The difference from Example 1 is that 5.2 mg of graphene oxide was added, and the obtained CSB / rGO composite photocatalyst was recorded as Cs2SnBr6 / 2.6% rGO.

[0047] Example 4

[0048] Preparation of CSB

[0049] Dissolve 0.438g of tin bromide in 30mL of 48% hydrobromic acid solution, stir for 20 minutes, then add 0.4256g of cesium bromide and continue stirring. The mixture is then transferred to a 50ml reactor and hydrothermally reacted at 160°C for 2 hours. After cooling the reactor, the resulting product is washed with isopropanol, centrifuged, and dried at 60°C for 6 hours to obtain CSB.

[0050] The preparation of graphene oxide (GO) and the preparation of CSB / rGO composite photocatalyst were the same as those in Example 1.

[0051] Comparative Example 1

[0052] Dissolve 0.355g of tin acetate in 30mL of 48% hydrobromic acid solution, stir for 20 minutes, then add 0.3839g of cesium acetate and continue stirring. The mixture is then transferred to a 50ml reactor and hydrothermally reacted at 160°C for 2 hours. After cooling the reactor, the resulting product is washed with isopropanol, centrifuged, and dried at 60°C for 6 hours to obtain Cs2SnBr6.

[0053] Comparative Example 2

[0054] Under constant stirring in an ice-water bath, 1g of flake graphite was added to a 200mL beaker containing 46mL of the strong acid H2SO4. 1g of NaNO3 was then added, and 6g of KMnO4 was slowly added to the beaker to obtain a mixture. The mixture was transferred to a 38°C environment and stirred for 30 hours for oxidation and further intercalation. 40mL of deionized water was slowly added to the mixture at room temperature. After stirring for 1 hour, 80mL of deionized water was added to dilute the mixture, and the mixture was stirred at 95°C for 1 hour. Next, 6mL of H2O2 was added dropwise, and the color of the solution turned golden yellow, indicating that graphene oxide had been successfully synthesized. The resulting solution was centrifuged and washed with 10% HCl and deionized water until the pH of the supernatant reached 7. Finally, the resulting graphene oxide powder was freeze-dried to obtain GO.

[0055] like Figure 1 As shown, compared with GO, it can be seen that the relative intensities of D-band and G-band in the CSB / rGO composite photocatalyst of Example 1 are D / I G The ratio changes, indicating that GO is successfully reduced to rGO; secondly, the shape and position of the CSB / rGO characteristic peak match well with the Raman spectrum of CSB, indicating that the CSB / rGO composite photocatalyst is successfully prepared.

[0056] like Figure 2 As shown, the CSB / rGO of Example 1 presents the lattice of CSB and rGO, and the Cs, Sn, C, and O elements are uniformly distributed in CSB / rGO, proving that rGO is successfully introduced.

[0057] The XPS spectra of the CSB / rGO composite photocatalyst, Cs2SnBr6 and GO in Example 1 are as follows: Figure 3 As shown. Generally, a decrease in electron concentration leads to a weakening of the electron shielding effect and an increase in binding energy. On the other hand, an increase in electron concentration leads to an enhanced electron shielding effect and a decrease in binding energy. Therefore, according to the binding energy results, the binding energy of Cs 3d, Sn 3d, and Br 3d in CSB / rGO shifts to higher energy, while the binding energy of O 1s shifts to lower energy. In addition, new peaks appear in the C1s and O 1s spectra, proving the existence of Sn-OC bonds and indicating a strong interaction between CSB and rGO in CSB / rGO.

[0058] Example 5

[0059] Photocatalytic HMF oxidation experiments were performed using a Pyrex reaction cell that can be directly connected to a vacuum system. Before the photoreaction, 15 mg of the photocatalyst was dispersed in 10 mL of acetonitrile containing 5 mM HMF and placed in the reactor. Oxygen was then introduced into the reactor (maintained at 1 atm). The reactor was connected to circulating cooling water to maintain the reaction at 288 K to avoid selectivity changes caused by excessive temperatures. A 300 W xenon lamp with a 400 nm cutoff filter was used as the light source. After completion of the reaction, the reaction was analyzed using a liquid chromatograph (SHIMADZU) to determine changes in conversion and selectivity.

[0060] Photocatalytic HMF oxidation experiments were carried out using Cs2SnBr6, Cs2SnBr6 / 0.8% rGO, Cs2SnBr6 / 1.6% rGO, and Cs2SnBr6 / 2.6% rGO as photocatalysts. The results are shown in Figure 2. Figure 4 As shown. Figure 4 As shown in a, the reactant HMF generates the target product DFF under the drive of catalyst, oxygen and light, and a small part of DFF will be further oxidized to form FFCA. Figure 4 As shown in b, by comparing single variables, it is shown that under dark conditions or in the absence of catalyst Cs2SnBr6 / 1.6% rGO, the conversion rate of DFF will drop significantly, indicating that this reaction is a light-driven reaction. The photocatalytic HMF oxidation of Cs2SnBr6 / 1.6% rGO achieved a conversion rate of >99.5% and a selectivity of 88% for the target product DFF. The conversion rate and selectivity of the photocatalytic HMF oxidation of Cs2SnBr6, Cs2SnBr6 / 0.8% rGO, Cs2SnBr6 / 1.6% rGO, and Cs2SnBr6 / 2.6% rGO were compared, as shown in Figure 2. Figure 4 As shown in (b), the conversion rate of photocatalytic HMF oxidation of CSB / rGO is improved compared with Cs2SnBr6, and Cs2SnBr6 / 1.6%rGO has the best photocatalytic HMF oxidation performance.

[0061] like Figure 5 As shown, single-particle spectroscopy was used to investigate the charge carrier dynamics of the photocatalyst. The peak PL emission intensity of CSB is 2500 a.u., while that of CSB / rGO in Example 1 is 1200 a.u. The fluorescence intensity of CSB / rGO is significantly reduced, indicating a lower recombination rate of photogenerated electrons and holes. The increased PL lifetime of CSB / rGO indicates that the Sn-O-C bond between CSB and rGO facilitates carrier transport and separation, thus contributing to improved photocatalytic performance.

[0062] like Figure 6As shown in a, the conversion rate of CSB / rGO in Example 1 is reduced when adding different capture agents for photocatalytic HMF oxidation. Figure 6 As shown in Figures b and c, the spin-active O can be detected using the trapping agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). 2- and 1 O2. Compared with CSB, the DMPO-·O 2- and DMPO- 1 The signal intensity of O2 increased significantly, and the signal intensity increased with the increase of illumination time, indicating that the active oxygen species originated from the photogenerated carriers of the catalyst. Figure 6 Panel d shows that the reactive oxygen species are gradually converted into hydrogen peroxide (H2O2) in the subsequent reaction with HMF, and the generated H2O2 is measured by iodine titration colorimetry using a UV-visible spectrophotometer.

[0063] Figure 7 The mechanism diagram of photocatalytic oxidation of HMF by CSB / rGO is shown. Under light irradiation, photogenerated electron-hole pairs are generated and separated and transferred to the surface of CSB. The electrons on the surface of CSB are quickly captured by rGO and reduced to activated ·O through molecular oxygen reduction. 2- , formed by ·O 2- Combined with a proton of HMF to form ·OOH, HMF is converted into the corresponding anionic alcohol oxide. This anionic alcohol oxide generates alcohol oxide free radicals after interacting with h+, which are then oxidized by ·OOH to generate the target product DFF. On the other hand, the energy conversion is generated by the interaction between the hole and the superoxide radical or molecular oxygen. 1 O2, 1 O2 abstracts a proton from HMF to generate an alcohol oxygen radical, which then reacts with ·OOH to produce the target product DFF.

[0064] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. Application of a CSB / rGO composite photocatalyst in photocatalytic oxidation of 5-hydroxymethylfurfural, characterized in that: The preparation method of the CSB / rGO composite photocatalyst comprises the following steps: S1. Dissolve tin salt in hydrobromic acid solution, stir, and then add cesium salt to obtain a mixed solution. After the mixed solution undergoes hydrothermal reaction, the product is washed, centrifuged, and dried to obtain Cs2SnBr6, i.e., CSB. S2. CSB and graphene oxide are dispersed in a saturated HBr and H3PO2 mixed solution and photoreduced to obtain a CSB / rGO composite photocatalyst; the mass ratio of CSB to graphene oxide is 125:1-3.

25.

2. The use according to claim 1, characterized in that The tin salt includes one or more of tin acetate and tin bromide, the cesium salt includes one or more of cesium acetate and cesium bromide, and the molar ratio of the tin salt to the cesium salt is 1:

2.

3. The use according to claim 1, characterized in that In step S1, the hydrothermal reaction temperature is 150-170° C., and the hydrothermal time is 2-4 h.

4. The use according to claim 1, wherein In step S1, isopropyl alcohol is used for washing, and the drying temperature is 50-70° C. and the drying time is 5-7 h.

5. The use according to claim 1, characterized in that The graphene oxide is obtained by oxidizing flake graphite through the Hummers method.

6. The use according to claim 1, wherein In step S2, dispersion is performed by ultrasound and stirring, wherein the ultrasound time is 30-60 min, and the stirring time is 30-60 min.

7. The use according to claim 1, wherein In step S2, the photoreduction is performed using a xenon lamp equipped with an AM1.5 filter, and the power of the xenon lamp is 300-350 W.

Images