Photocatalyst for synthesizing H2O2 and preparation method thereof

Abstract

The invention discloses a photocatalyst for synthesizing H2O2 and a preparation method of the photocatalyst, and belongs to the field of catalyst preparation and H2O2 synthesis. The photocatalyst is a bimetallic structure material with La and In, contains rich sulfur vacancy defects and has a regular porous square nano-morphology. The preparation method comprises the following steps: adding lanthanum nitrate and indium nitrate in different proportions, adjusting the molar ratio of La to In in the catalyst, uniformly mixing deionized water and absolute ethyl alcohol by taking thiourea as a sulfur source and sodium dodecyl benzene sulfonate as a surfactant, and synthesizing a catalyst precursor by a hydrothermal method; and finally, calcining in a hydrogen atmosphere to obtain the LayInSX photocatalyst which contains rich sulfur vacancy defects and has a regular porous square nano-morphology. The LayInSx photocatalyst prepared by the invention has the advantages that the LayInSx photocatalyst has higher and more stable photocatalytic H2O2 synthesis performance (2676 mu mol.h <-1 >. G <-1 >) in a pure water phase at normal temperature under the condition of not adding any sacrificial agent, is suitable for an actual engineering environment, and has a better application prospect.

Description

Technical Field

[0001] The present invention relates to the field of catalyst preparation and H2O2 synthesis, and in particular to a novel La catalyst for synthesizing H2O2. y InS x Photocatalyst and method for preparing the same.

[0002] Background Field

[0003] Hydrogen peroxide (H2O2), as an important oxidant, is an environmentally friendly and widely used chemical raw material and fine chemical. It can be used in pulp bleaching, sewage treatment, food and medicine, metallurgy and other fields. However, its mainstream production method, the anthraquinone method, has the disadvantages of high energy consumption and great safety hazards. Therefore, the synthesis of H2O2 through artificial photosynthesis using water and oxygen as raw materials has the characteristics of safety, environmental protection and energy saving, and has become a current research hotspot.

[0004] In recent years, most catalysts have focused on materials such as COF, MOF and transition metals (such as iridium, ruthenium and platinum), and there has been little research on lanthanide metal catalysts. Compared with some of the metal elements mentioned above, lanthanide metals have the advantages of low price and abundant content. In addition, the 4f orbital of lanthanide elements (La) is not fully occupied and the 5f orbital is empty, which can provide effective electron capture ability, thereby improving the separation efficiency of photoexcited carriers. As a typical lanthanide compound, La's shallow potential well induced by its all-electronic configuration can effectively regulate the electronic structure and catalytic activity of photocatalysts, so we chose La metal in the lanthanide series as one of the raw materials.

[0005] At the same time, studies have shown that bimetallic catalysts have many advantages compared to monometallic catalysts: bimetallic photocatalysts can usually absorb a wider range of spectra; heterogeneous structures can be formed between the two metals in bimetallic catalysts, which can effectively separate photogenerated electrons and holes, thereby reducing the recombination rate of electron-hole pairs and improving photocatalytic efficiency. And bimetallic catalysts also have obvious advantages over monometallic catalysts in terms of selectivity and stability. In the latest research, it was found that indium (In) synthesized photocatalysts in the form of sulfides have excellent photocatalytic performance and are widely used in the field of photocatalysis. In addition, the construction of sulfur vacancy defects on the surface of sulfide catalysts can act as electron capture centers and adsorption activation centers of reactants, which can effectively separate photogenerated electrons and holes, prolong the carrier lifetime, and facilitate the adsorption and activation of reactants, thereby effectively enhancing the photocatalytic activity. Therefore, the introduction of La and In two metal materials to prepare bimetallic sulfides with rich sulfur vacancy defects has theoretically high photocatalytic performance, which can provide new catalyst design ideas and options for photocatalytic synthesis of H2O2. Summary of the invention

[0006] In view of the shortcomings of the existing research and application of lanthanide catalysts for photocatalytic synthesis of H2O2, the technical problem to be solved by the present invention is to provide a new La photocatalyst for synthesizing H2O2. y InS X A photocatalyst and a preparation method thereof are provided, so that the catalyst has good photocatalytic performance without adding any sacrificial agent.

[0007] The present invention is achieved through the following technical solutions.

[0008] The invention provides a photocatalyst for synthesizing H2O2. The photocatalyst is a bimetallic structural material with La and In, contains abundant sulfur vacancy defects and has a regular porous square nano morphology.

[0009] Furthermore, the molar ratio of La to In in the photocatalyst is (2-5):1.

[0010] Furthermore, the molar ratio of La to In in the photocatalyst is 4:1.

[0011] The present invention also provides a method for preparing the above-mentioned photocatalyst, which specifically comprises the following preparation steps:

[0012] (1) Lanthanum nitrate and indium nitrate are added as metal sources, thiourea is used as a sulfur source, and deionized water and anhydrous ethanol are added and stirred thoroughly until dissolved.

[0013] (2) Then add an appropriate amount of sodium dodecylbenzene sulfonate to the mixture and continue stirring until it dissolves.

[0014] (3) placing the mixed solution in a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction; then centrifuging, drying, calcining and grinding in sequence to obtain La y InS X The calcination is carried out under a hydrogen atmosphere.

[0015] Furthermore, the stirring time of step (1) and step (2) is 20 minutes; wherein the volume ratio of deionized water to anhydrous ethanol in step (1) is 2:1.

[0016] Furthermore, the hydrothermal temperature in step (3) is 120° C., and the hydrothermal time is 10 to 14 hours.

[0017] Furthermore, the calcination temperature in the step (3) is 300-400° C., and the calcination time is 2 hours.

[0018] The photocatalyst provided by the invention can photocatalytically synthesize H2O2 in a pure water phase at room temperature.

[0019] Compared with the prior art, the present invention has the following technical effects:

[0020] 1. A new type of La synthesized by the present invention y InS X The photocatalyst has the advantage of having a relatively high and stable photocatalytic H2O2 synthesis performance (2676 μmol·h -1 ·g -1 ), which is suitable for actual engineering environments, has good application prospects, and provides new catalyst selection and design ideas for the field of H2O2 synthesis.

[0021] 2. The preparation method of the present invention is simple and low in cost. The bimetallic reaction sites and sulfur vacancy defects are introduced by combining the hydrothermal method and the reducing atmosphere calcination method, and the contact between the components is optimized by adding sodium dodecylbenzene sulfonate to prepare La with sulfur vacancy defects. y InS X Photocatalyst.

[0022] 3. La synthesized by the present invention y InS X The material can serve as a good carrier, and modification and doping can further improve the performance of photocatalytic synthesis of H2O2. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure is a flow chart for preparing the catalyst material synthesized by the present invention.

[0024] Figure 2 This is the H2O2 standard curve data graph.

[0025] Figure 3 This is the test data of photocatalytic H2O2 activity of different samples.

[0026] Figure 4 The La4InS obtained in the present invention X Sample reaction stability data graph.

[0027] Figure 5 The La4InS obtained in the present invention x Microscopic morphology of the material.

[0028] Figure 6 The La4InS obtained in the present invention x Electron NMR spectra of the materials. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] 1.2990g of lanthanum nitrate, 0.6897g of indium nitrate and 0.6851g of thiourea were weighed into a beaker, i.e., the molar ratio of La:In = 2:1 was added, 40mL of water and 20mL of anhydrous ethanol were added, and a certain amount of sodium dodecylbenzene sulfonate was added after stirring at room temperature for 20min on a magnetic stirrer, and stirred again for 20min, and then placed in a polytetrafluoroethylene autoclave for hydrothermal treatment at 120℃ for 12h. After taking out, the solid matter was centrifuged, dried, and finally calcined at 300℃ for 2h in a hydrogen atmosphere to prepare the catalyst La2InS x .

[0032] Example 2

[0033] 1.9485g of lanthanum nitrate, 0.6897g of indium nitrate and 0.6851g of thiourea were weighed into a beaker, i.e., the molar ratio of La:In=3:1 was added, 40mL of water and 20mL of anhydrous ethanol were added thereto, and a certain amount of sodium dodecylbenzene sulfonate was added after stirring at room temperature for 20min on a magnetic stirrer, and stirred again for 20min, and then placed in a polytetrafluoroethylene autoclave for hydrothermal treatment at 120℃ for 12h. After taking out, the solid matter was centrifuged, dried, and finally calcined at 300℃ for 2h in a hydrogen atmosphere to prepare the catalyst La3InS x .

[0034] Example 3

[0035] 2.5980g of lanthanum nitrate, 0.6897g of indium nitrate and 0.6851g of thiourea were weighed into a beaker, i.e., the molar ratio of La:In=4:1 was added, 40mL of water and 20mL of anhydrous ethanol were added thereto, and a certain amount of sodium dodecylbenzene sulfonate was added after stirring at room temperature for 20min on a magnetic stirrer, and stirred again for 20min, and then placed in a polytetrafluoroethylene autoclave for hydrothermal treatment at 120℃ for 12h. After taking out, the solid matter was centrifuged, dried, and finally calcined at 300℃ for 2h in a hydrogen atmosphere to prepare the catalyst La4InS X .

[0036] Example 4

[0037] 3.2475 g of lanthanum nitrate, 0.6897 g of indium nitrate and 0.6851 g of thiourea were weighed into a beaker, i.e., the molar ratio of La:In = 5:1 was added, 40 mL of water and 20 mL of anhydrous ethanol were added thereto, and a certain amount of sodium dodecylbenzene sulfonate was added after stirring at room temperature for 20 min on a magnetic stirrer, and then stirred for another 20 min, and then placed in a polytetrafluoroethylene autoclave for hydrothermal treatment at 120 ° C for 12 h. After taking out, the solid matter was centrifuged, dried, and finally calcined at 300 ° C for 2 h in a hydrogen atmosphere to prepare the catalyst LasInS x .

[0038] Example 5

[0039] Weigh 0.6897g of indium nitrate and 0.6851g of thiourea into a beaker, add 40mL of water and 20mL of anhydrous ethanol, stir for 20min at room temperature on a magnetic stirrer, add a certain amount of sodium dodecylbenzene sulfonate, stir for another 20min, and then place in a polytetrafluoroethylene autoclave for hydrothermal treatment at 120℃ for 12h. After taking out, the solid material was centrifuged, dried, and finally calcined at 300℃ for 2h in a hydrogen atmosphere to prepare the catalyst InSx.

[0040] Example 6

[0041] 1.9485g of lanthanum nitrate and 0.6851g of thiourea were weighed into a beaker, 40mL of water and 20mL of anhydrous ethanol were added thereto, and a certain amount of sodium dodecylbenzene sulfonate was added after stirring at room temperature for 20min on a magnetic stirrer, and stirred again for 20min, and then placed in a polytetrafluoroethylene autoclave for hydrothermal treatment at 120℃ for 12h. After taking out, the solid matter was centrifuged, dried, and finally calcined at 300℃ for 2h in a hydrogen atmosphere to prepare the catalyst LaSx.

[0042] in, Figure 1 This is a flow chart for preparing the catalyst materials in Examples 1 to 6.

[0043] Example 7

[0044] Determination of H2O2 standard curve:

[0045] Step 1: Prepare a H2O2 standard solution with a certain concentration gradient. Take 1.0210mL of 30% H2O2 solution and use a volumetric flask to prepare 100mL of 0.1mol·L -1 Then, take 0.05mL, 0.1mL, 0.3mL, 0.5mL and 1mL of standard solution A respectively and use volumetric flasks to prepare 100mL of 0.05mmol·L -1 (A1), 0.1mmol·L -1 (A2), 0.3mmol·L -1(A3), 0.5mmol·L -1 (A4) and 1mmol·L -1 (A5) H2O2 standard solution.

[0046] Step 2: Prepare the color developer. Weigh 2.0420g potassium hydrogen phthalate and 6.6400g potassium iodide reagent and dissolve them in a beaker. Use a volumetric flask to prepare 100mL of 0.1M and 0.4M standard solution B and standard solution C, respectively.

[0047] Step 3: Determine the H2O2 standard curve. Take 1 mL of A1, A2, A3, A4 and A5 solutions respectively into the reaction tube, and add 1 mL of solution B and 1 mL of solution C. Shake well and let stand for 30 minutes. Use deionized water as blank reference and use a spectrophotometer to measure the absorbance A0 of the characteristic absorption peak of H2O2 at 350 nm. Plot the standard curve with hydrogen peroxide content (mmol·L -1 ) versus absorbance (A0) standard curve, the results are as follows Figure 2 shown.

[0048] Example 8

[0049] The catalysts prepared in Examples 1 to 6 were tested for activity and compared. 0.01 g of the prepared catalyst was weighed into a reactor, and 30 mL of deionized water was added. The mixture was stirred at 500 r / min under a magnetic stirrer. -1 Stir continuously at 80 mL min -1 O2 was continuously introduced into the reaction system. The system was kept in the dark for 1 hour to allow for sufficient aeration and oxygenation. Then, the xenon lamp was turned on for light reaction. After 1 hour, the absorbance of the characteristic absorption peak of H2O2 at a wavelength of 350nm was measured using the iodine titration method and UV-visible spectrophotometer. The measured results are shown in the figure. Figure 3 The results show that when the ratio of La to In is 4:1, the H2O2 yield is the highest without any sacrificial agent, reaching 2676 μmol·g -1 ·h -1 , which is at least 46 times higher than that of single metal sulfide.

[0050] Example 9

[0051] The La4InS prepared in Example 3 X The stability test of the material was carried out similar to Example 8, with the reaction time being 20, 40, 60 and 80 min and each sample was taken once. The test results are shown in FIG. Figure 4 As shown in the figure, it can be concluded that the catalyst has good stability.

[0052] Example 10

[0053] The La4InS prepared in Example 3X The material was subjected to two characterization tests. First, its morphology was tested using a scanning electron microscope (SEM). Figure 5 Shown: Discover La y InS x The catalyst solid particles are regular block morphology with abundant pores, which is conducive to the adsorption and activation of reactants. Secondly, the electron nuclear magnetic resonance spectroscopy (EPR) test was performed on it, and the results are as follows Figure 6 As shown: It shows that the catalyst surface contains abundant sulfur vacancy defects.

Claims

1. A photocatalyst for synthesizing H2O2, characterized in that: The photocatalyst is a bimetallic structure material with La and In, which contains abundant sulfur vacancy defects and has a regular porous square nano-morphology.

2. A photocatalyst for synthesizing H2O2 as claimed in claim 1, characterized in that: The molar ratio of La to In in the photocatalyst is (2-5):

1.

3. A photocatalyst for synthesizing H2O2 as claimed in claim 2, characterized in that: The molar ratio of La to In in the photocatalyst is 4:

1.

4. The method for preparing a photocatalyst for synthesizing H2O2 as claimed in claim 1, characterized in that The method comprises the following preparation steps: (1) adding lanthanum nitrate and indium nitrate as metal sources, thiourea as sulfur source, adding deionized water and anhydrous ethanol and stirring thoroughly until dissolved; (2) then adding sodium dodecylbenzene sulfonate to the mixture and stirring continuously until dissolved; (3) placing the mixed solution in a polytetrafluoroethylene high-pressure reactor for hydrothermal reaction; Then centrifugation, drying, calcination and grinding are carried out in sequence to obtain the product; the calcination is carried out under a hydrogen atmosphere.

5. The method for preparing a photocatalyst for synthesizing H2O2 according to claim 4, characterized in that: The stirring time of step (1) and step (2) is 20 minutes; wherein the volume ratio of deionized water to anhydrous ethanol in step (1) is 2:

1.

6. The method for preparing a photocatalyst for synthesizing H2O2 as claimed in claim 4, characterized in that: The hydrothermal temperature in step (3) is 120° C. and the hydrothermal time is 10 to 14 hours.

7. The method for preparing a photocatalyst for synthesizing H2O2 as claimed in claim 4, characterized in that: The calcination temperature in the step (3) is 300-400° C. and the calcination time is 2 hours.

8. Use of the photocatalyst as claimed in claim 1 for photocatalytic synthesis of H2O2 in a pure water phase at room temperature.

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