Photocatalyst for degrading organic silicon as well as preparation method and application of photocatalyst

Abstract

The invention provides a photocatalyst for degrading organic silicon as well as a preparation method and application of the photocatalyst, and belongs to the technical field of photocatalysts. The preparation method comprises the following steps: mixing a titanium source with a solvent, adjusting the pH value, hydrolyzing, adding a silicon source under the protection of an inert atmosphere to carry out condensation reaction to obtain a TiO2 / SiO2 substrate; the preparation method comprises the following steps: introducing an MXene two-dimensional material on a TiO2 / SiO2 substrate through in-situ growth to form an MXene / TiO2 / SiO2 aerogel structure, and sequentially carrying out supercritical drying and segmented calcination to obtain the composite photocatalyst. A strong electron transmission channel is formed between the MXene and the substrate, agglomeration is effectively inhibited, the charge separation efficiency is enhanced, and therefore separation of photon-generated carriers is accelerated; the MXene two-dimensional material grows directionally along the surface of the substrate to form a layered heterojunction structure, and separation of photo-induced electron-hole pairs is promoted through a Schottky barrier.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysts, and in particular to a photocatalyst for degrading organic silicon, a preparation method thereof, and an application thereof. Background Art

[0002] With the widespread application of organosilicon materials in electronic packaging, medical devices, and other fields, the issue of waste disposal has become increasingly prominent. Traditional pyrolysis methods suffer from high energy consumption and secondary pollution, while photocatalytic degradation technology has become a research hotspot due to its advantages such as mild reaction conditions and non-selective degradation. Current mainstream photocatalysts, such as pure TiO2, have drawbacks such as wide band gaps, low visible light utilization, and insufficient adsorption capacity for hydrophobic organosilicon.

[0003] In recent years, existing technologies have improved the dispersibility of materials by loading TiO2 onto SiO2 substrates. However, composite materials prepared by traditional sol-gel methods suffer from low porosity and poor mechanical strength. Two-dimensional materials, such as MXene, have recently been shown to effectively promote photogenerated electron transfer due to their excellent conductivity and surface functional groups. However, their composite technology with TiO2 / SiO2 systems is still not mature. While supercritical drying technology can maintain nanostructure integrity, it still faces challenges in balancing multi-level pore structure with thermal stability.

[0004] Currently, the photocatalytic degradation of organosilicon pollutants generally suffers from problems such as easy catalyst deactivation and low reuse rate. In particular, the high chemical stability of methylsiloxane substances requires the catalyst to have both strong oxidation ability and adsorption enrichment function. For example, in the Chinese patent application with application number 202010327660.6, silica aerogel is used as a carrier, MXene and nano-titanium dioxide with photocatalytic activity are dispersed in the silica aerogel to form a TiO2 / MXene / SiO2 aerogel composite system, and MXene and TiO2 nanoparticles are directly dispersed into the three-dimensional porous network of SiO2 aerogel through physical or chemical mixing. However, in this prior art, the MXene is randomly distributed and difficult to arrange in a directional manner. In addition, the MXene and TiO2 are mainly bonded by physical adsorption or weak chemical bonds, resulting in local agglomeration, weak interfacial bonding, high photogenerated carrier recombination rate, and easy oxidation failure of MXene.

[0005] Based on this, it is very important to provide a photocatalyst that can synergistically improve the carrier separation efficiency and structural stability through multidimensional heterojunction design and segmented calcination process. Summary of the Invention

[0006] The purpose of the present invention is to provide a photocatalyst for degrading organosilicon, a preparation method and application thereof, so as to solve the technical problems in the prior art of low interfacial reaction efficiency and high photogenerated carrier recombination rate caused by low solubility of organosilicon.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for preparing a photocatalyst for degrading organosilicon, comprising the following steps: 1) Mixing a titanium source with a solvent and adjusting the pH to hydrolyze the mixture, forming a sol, and then adding a silicon source under an inert atmosphere to carry out a condensation reaction to obtain a TiO2 / SiO2 substrate; 2) MXene two-dimensional material is introduced by in situ growth on the TiO2 / SiO2 substrate to form a MXene / TiO2 / SiO2 aerogel structure, which is then subjected to supercritical drying and staged calcination to obtain a composite photocatalyst.

[0008] Furthermore, the titanium source includes butyl titanate; The solvent includes anhydrous ethanol; The silicon source includes methyltrimethoxysilane and / or ethyl orthosilicate.

[0009] Furthermore, the mass ratio of the titanium source, the solvent and the silicon source is 1:2-5:0.3-0.7; The mass ratio of the MXene two-dimensional material to the TiO2 / SiO2 substrate is 1:6~15.

[0010] Furthermore, in step 1), the reagent used to adjust the pH is glacial acetic acid, and the pH is 2-4; The hydrolysis temperature is 30-50° C., and the hydrolysis time is 1-3 hours.

[0011] Furthermore, the inert atmosphere is argon and / or nitrogen; The condensation reaction temperature is 40-60° C., and the condensation reaction time is 3-8 hours.

[0012] Furthermore, the in-situ growth temperature is 60-100° C., and the in-situ growth time is 4-8 hours.

[0013] Furthermore, the supercritical drying temperature is 35-40° C., the supercritical drying pressure is 8-10 MPa, and the supercritical drying time is 3-4 hours.

[0014] Furthermore, the staged calcination is divided into two stages, the calcination temperature of the first stage is 250-400°C, the calcination time of the first stage is 1-2 hours, the calcination temperature of the second stage is 500-600°C, and the calcination time of the second stage is 2-3 hours.

[0015] The invention provides a photocatalyst for degrading organic silicon prepared by the preparation method.

[0016] The present invention also provides an application of the photocatalyst in degrading organic silicon.

[0017] Beneficial effects of the present invention: 1) The preparation method of the present invention first constructs a TiO2 / SiO2 composite substrate, and then controllably grows a MXene two-dimensional material on the substrate surface through an in-situ condensation reaction to form a chemically bonded interface (such as Ti-O-Ti, Ti-OC or Si-O-MXene). A strong electron transport channel is formed between the MXene and the substrate, effectively suppressing agglomeration and enhancing charge separation efficiency, thereby accelerating the separation process of photogenerated carriers; 2) In the preparation method of the present invention, the MXene two-dimensional material grows in a directional manner along the substrate surface to form a layered heterojunction structure, which promotes the separation of photogenerated electron-hole pairs through the Schottky barrier and enhances the adsorption capacity of pollutants by utilizing the mesoporous structure of SiO2; 3) The present invention utilizes the silanol (-Si-OH) groups on the surface of the TiO2 / SiO2 composite substrate to specifically bind to organosilicon molecules through hydrogen bonds, thereby increasing the concentration of local reactants. The conductive properties of MXene match the energy band structure of TiO2, enabling rapid desorption of photogenerated electrons, inhibiting recombination reactions, and extending the lifetime of holes. 4) The preparation method of the present invention, through the synergistic effect of "ternary composite system construction + in situ growth + supercritical drying + staged calcination", not only preserves the aerogel network structure and maintains the integrity of the porous structure, avoids the pore collapse caused by traditional drying, ensures the full exposure of active sites, but also avoids lattice defects, improves crystallinity, and promotes crystal form transformation when removing organic matter. DETAILED DESCRIPTION

[0018] The present invention provides a method for preparing a photocatalyst for degrading organosilicon, comprising the following steps: 1) Mixing a titanium source with a solvent and adjusting the pH to hydrolyze the mixture, forming a sol, and then adding a silicon source under an inert atmosphere to carry out a condensation reaction to obtain a TiO2 / SiO2 substrate; 2) MXene two-dimensional material is introduced by in situ growth on the TiO2 / SiO2 substrate to form a MXene / TiO2 / SiO2 aerogel structure, which is then subjected to supercritical drying and staged calcination to obtain a composite photocatalyst.

[0019] In the present invention, the titanium source is preferably butyl titanate; The solvent is preferably anhydrous ethanol; The silicon source includes methyltrimethoxysilane and / or ethyl orthosilicate, preferably methyltrimethoxysilane.

[0020] In the present invention, the mass ratio of the titanium source, the solvent and the silicon source is 1:2-5:0.3-0.7, preferably 1:2.5-4.5:0.4-0.6, and more preferably 1:3-4:0.5; The mass ratio of the MXene two-dimensional material to the TiO2 / SiO2 substrate is 1:6~15, preferably 1:7~14, and more preferably 1:8~13.

[0021] In the present invention, in step 1), the reagent used to adjust the pH is preferably glacial acetic acid, and the pH is 2 to 4, preferably 2.5 to 3.5, and more preferably 3; The hydrolysis temperature is 30-50° C., preferably 35-45° C., more preferably 40° C.; the hydrolysis time is 1-3 h, preferably 1.5-2.5 h, more preferably 2 h.

[0022] In the present invention, the inert atmosphere is argon and / or nitrogen, preferably argon; The condensation reaction temperature is 40-60° C., preferably 45-55° C., more preferably 50° C.; the condensation reaction time is 3-8 h, preferably 4-7 h, more preferably 5-6 h.

[0023] In the present invention, the in-situ growth temperature is 60-100° C., preferably 65-95° C., more preferably 70-90° C.; the in-situ growth time is 4-8 h, preferably 4.5-7.5 h, more preferably 5-7 h.

[0024] In the present invention, the supercritical drying temperature is 35-40°C, preferably 36-39°C, and more preferably 37-38°C; the supercritical drying pressure is 8-10 MPa, preferably 8.5-9.5 MPa, and more preferably 9 MPa; the supercritical drying time is 3-4 h, preferably 3.2-3.8 h, and more preferably 3.4-3.6 h.

[0025] In the present invention, the staged calcination is divided into two stages, the calcination temperature of the first stage is 250~400℃, preferably 280~380℃, more preferably 300~350℃; the calcination time of the first stage is 1~2h, preferably 1.2~1.8h, more preferably 1.4~1.6h; the calcination temperature of the second stage is 500~600℃, preferably 520~580℃, more preferably 540~560℃; the calcination time of the second stage is 2~3h, preferably 2.2~2.8h, more preferably 2.4~2.6h.

[0026] The invention provides a photocatalyst for degrading organic silicon prepared by the preparation method.

[0027] The present invention also provides an application of the photocatalyst in degrading organic silicon.

[0028] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0029] Example 1

[0030] Butyl titanate was mixed with anhydrous ethanol and glacial acetic acid was added to adjust the pH to 3. The mixture was then hydrolyzed at 40°C for 2 hours. After the hydrolysis formed a sol, methyltrimethoxysilane (the mass ratio of butyl titanate, anhydrous ethanol, and methyltrimethoxysilane was 1:3:0.4) was added under argon atmosphere. The condensation reaction was carried out at 50°C for 6 hours to obtain a TiO2 / SiO2 substrate. MXene two-dimensional material was introduced on the TiO2 / SiO2 substrate by in situ growth (the mass ratio of MXene two-dimensional material and TiO2 / SiO2 substrate was 1:10). The in situ growth temperature was 80°C. After 6 hours of in situ growth, a MXene / TiO2 / SiO2 aerogel structure was formed. Then, supercritical drying was carried out at 40°C and 9MPa. After 2.5 hours of supercritical drying, segmented calcination was carried out. The calcination temperature of the first stage was 300°C, and the calcination time of the first stage was 1.5 hours; the calcination temperature of the second stage was 550°C, and the calcination time of the second stage was 2.5 hours. After the calcination, a composite photocatalyst was obtained.

[0031] Example 2

[0032] Butyl titanate was mixed with anhydrous ethanol, and glacial acetic acid was added to adjust the pH to 3.5. The mixture was then hydrolyzed at 40°C for 2.5 hours. After the hydrolysis formed a sol, methyltrimethoxysilane (the mass ratio of butyl titanate, anhydrous ethanol, and methyltrimethoxysilane was 1:3:0.4) was added under argon atmosphere. The condensation reaction was carried out at 50°C for 6 hours to obtain a TiO2 / SiO2 substrate. MXene two-dimensional material was introduced on the TiO2 / SiO2 substrate by in situ growth (the mass ratio of MXene two-dimensional material and TiO2 / SiO2 substrate was 1:10). The in situ growth temperature was 90°C. After 6 hours of in situ growth, a MXene / TiO2 / SiO2 aerogel structure was formed. Then, supercritical drying was carried out at 35°C and 9MPa. After supercritical drying for 4 hours, segmented calcination was carried out. The calcination temperature of the first stage was 350°C, and the calcination time of the first stage was 1 hour; the calcination temperature of the second stage was 600°C, and the calcination time of the second stage was 2 hours. After the calcination, a composite photocatalyst was obtained.

[0033] Example 3

[0034] Compared with Example 1, the difference is that in Example 3, the mass ratio of butyl titanate, anhydrous ethanol and methyltrimethoxysilane is 1:4:0.5; the mass ratio of MXene two-dimensional material and TiO2 / SiO2 substrate is 1:8.

[0035] Comparative Example 1 Tetrabutyl titanate is dissolved in anhydrous ethanol for hydrolysis and polycondensation to form a TiO2 sol; MXene two-dimensional material is dispersed in deionized water to obtain a MXene dispersion; The MXene dispersion was mixed with the TiO2 sol (the mass ratio of MXene to TiO2 sol was 1:5), stirred until uniform, dried, and then calcined at 500°C for 2h to obtain the TiO2 / MXene composite photocatalyst.

[0036] Comparative Example 2 Using tetraethyl orthosilicate as a precursor, it is hydrolyzed in an ethanol / water solution to generate SiO2 sol; dispersing the MXene two-dimensional material in deionized water to obtain a MXene dispersion; After mixing the MXene dispersion with the SiO2 sol, the pH was adjusted to 4 and the mixing was carried out while stirring for 8 hours. After the mixing was completed, the mixture was centrifuged and dried, and finally calcined at 400°C under argon atmosphere for 2 hours to obtain a SiO2 / MXene composite photocatalyst.

[0037] Comparative Example 3 Ethyl orthosilicate, anhydrous ethanol, and deionized water in a mass ratio of 1:4:0.2 were mixed evenly, and then oxalic acid was added to adjust the pH to 2.5 for hydrolysis to obtain a hydrolyzate; The hydrolyzate, nano-titanium dioxide and Ti3C2-MXene two-dimensional material in a mass ratio of 10:0.5:1 were stirred and dispersed evenly, and sodium carbonate was added to adjust the pH to 9.0 for a condensation reaction to obtain a wet gel. Finally, the composite photocatalyst was obtained after vacuum drying.

[0038] Application Examples 1 to 6 The photocatalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were used to degrade organosilicon in organosilicon compound fertilizer (organosilicon was selected from SY-3532 produced by Hebei Silicon Valley Fertilizer Co., Ltd.).

[0039] Application Example 7 Compared with Application Example 1, the difference is that Application Example 7 uses thermal catalytic degradation of silicone.

[0040] Application Example 8 Compared with Application Example 1, the difference is that Application Example 8 does not add the photocatalyst prepared in Example 1 to degrade the organosilicon.

[0041] Application Example 9 Compared with Application Example 1, the difference is that Application Example 9 degrades organic silicon under natural light without adding the photocatalyst prepared in Example 1.

[0042] The degradation rate of organosilicon was tested. The test results showed that the catalytic efficiency of Application Examples 1 to 3 was significantly higher than that of Application Examples 4 to 9. The degradation rate of Application Example 1 was 92.5%, the degradation rate of Application Example 2 was 94.8%, and the degradation rate of Application Example 3 was 90.1%. The degradation rates of Application Examples 4 to 6 were all below 80%, with Application Example 6 having the lowest degradation rate of only 71.3%. The degradation rate of Application Example 7 was 83.2%, the degradation rate of Application Example 8 was 65%, and the degradation rate of Application Example 9 was 69.2%. This further proves that the photocatalyst of the present invention has a good degradation effect on organosilicon, can effectively reduce the accumulation of organosilicon, and reduce biological toxicity.

[0043] The stability and repeatability were tested, and the test results showed that the degradation rate of the photocatalysts in Application Examples 1 and 2 remained above 85% after 5 cycles, indicating that supercritical drying and staged calcination effectively improved the structural stability; while the degradation rate of the photocatalyst in Application Example 4 dropped to 60% after 3 cycles, and the interface between MXene and TiO2 fell off due to non-in-situ bonding.

[0044] As can be seen from the above examples, the present invention provides a photocatalyst for the degradation of organosilicon, as well as its preparation method and application, comprising the following steps: mixing a titanium source with a solvent, adjusting the pH, and hydrolyzing the mixture; after the hydrolysis forms a sol, adding a silicon source under inert atmosphere for condensation reaction to obtain a TiO2 / SiO2 substrate; introducing a two-dimensional MXene material onto the TiO2 / SiO2 substrate via in situ growth to form a MXene / TiO2 / SiO2 aerogel structure; and then sequentially undergoing supercritical drying and staged calcination to obtain a composite photocatalyst. In the present invention, a strong electron transport channel is formed between the MXene and the substrate, effectively suppressing agglomeration and enhancing charge separation efficiency, thereby accelerating the separation of photogenerated carriers; the two-dimensional MXene material grows directionally along the substrate surface, forming a layered heterojunction structure, which promotes the separation of photogenerated electron-hole pairs via a Schottky barrier.

[0045] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a photocatalyst for degrading organosilicon, characterized in that: The following steps are involved: 1) Mixing a titanium source with a solvent and adjusting the pH to hydrolyze the mixture, forming a sol, and then adding a silicon source under an inert atmosphere to carry out a condensation reaction to obtain a TiO2 / SiO2 substrate; 2) MXene two-dimensional material is introduced by in situ growth on the TiO2 / SiO2 substrate to form a MXene / TiO2 / SiO2 aerogel structure, which is then subjected to supercritical drying and staged calcination to obtain a composite photocatalyst.

2. The method for preparing a photocatalyst for degrading organic silicon according to claim 1, characterized in that: The titanium source includes butyl titanate; The solvent includes anhydrous ethanol; The silicon source includes methyltrimethoxysilane and / or ethyl orthosilicate.

3. The method for preparing a photocatalyst for degrading organosilicon according to claim 1 or 2, characterized in that: The mass ratio of the titanium source, the solvent and the silicon source is 1:2-5:0.3-0.7; The mass ratio of the MXene two-dimensional material to the TiO2 / SiO2 substrate is 1:6~15.

4. The method for preparing a photocatalyst for degrading organic silicon according to claim 3, characterized in that: In step 1), the reagent used to adjust the pH is glacial acetic acid, and the pH is 2-4; The hydrolysis temperature is 30-50° C., and the hydrolysis time is 1-3 hours.

5. The method for preparing a photocatalyst for degrading organosilicon according to claim 1, 2 or 4, characterized in that: The inert atmosphere is argon and / or nitrogen; The condensation reaction temperature is 40-60° C., and the condensation reaction time is 3-8 hours.

6. The method for preparing a photocatalyst for degrading organic silicon according to claim 5, characterized in that: The in-situ growth temperature is 60-100° C., and the in-situ growth time is 4-8 hours.

7. The method for preparing a photocatalyst for degrading organic silicon according to claim 6, characterized in that: The supercritical drying temperature is 35-40° C., the supercritical drying pressure is 8-10 MPa, and the supercritical drying time is 3-4 hours.

8. The method for preparing a photocatalyst for degrading organosilicon according to claim 4, 6 or 7, characterized in that: The staged calcination is divided into two stages. The calcination temperature of the first stage is 250-400° C. and the calcination time of the first stage is 1-2 hours. The calcination temperature of the second stage is 500-600° C. and the calcination time of the second stage is 2-3 hours.

9. A photocatalyst for degrading organosilicon prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the photocatalyst according to claim 9 in the degradation of organosilicon.