A simple method for synthesising ultrafine TIO2@C7H80@C photocatalysts and use of the photocatalysts in degradation of methanal

Abstract

An ultrafine photocatalyst comprising TiO2, the surface of which is doped with carbon and an interlayer of C7H8O. The catalyst is prepared by1) adding titanium tetrachloride dropwise into phenylethan

Description

[0001] The present disclosure relates to a simple and low-cost method for preparing a titanium dioxide photocatalyst and use of the photocatalyst in removing methanal in air. BACKGROUND

[0002] Photocatalytic technology is a sustainable green technology driven by sunlight, and is one of the most promising methods to effectively solve problems of the current energy crisis and environmental pollution. Since Fujishima discovered the TiO2 photocatalytic phenomenon in 1972, the photocatalytic oxidation technology, represented by semiconductor photocatalysts, has become a practical and valuable treatment technology for environmental remediation. TIO2 is widely used as a photocatalytic material, and is of great interest due to its advantages such as high stability, excellent photocatalytic performance and environmental friendliness.

[0003] In order to take full use of solar energy, especially visible light, various methods have been developed to modify TiO2 to overcome problems of its wide tend gap and rapid electronhole recombination, including doping with heteroatoms, assembling with co-catalysts and defect engineering. As a result, a series of highly active TiO2 photocatalysts with visible light responsiveness have been developed. It is a relatively effective means to dope TiO2 with other materials for enhancing the photocatalytic performance of TIO2, as various dopants could reduce the recombination rate of photogenerated electron-hole palrs, enhance light absorption and even effectively adsorb target pollutants. Such dopants usually include precious or non-precious metals, metal oxides, carbonaceous materials, co-catalysts and the like.

[0004] Carbonaceous materials have excellent properties, such as high specific surface area and strong adsorption properties. Doping TiO2 with carbon could effectively adsorb target substances and reduce the mass transfer resistance between TiO2 and the target substances. Moreover, the relatively low charge transfer resistance could reduce the electron-hole pair recombination of carbon-doped TiO2, thus improving the photocatalytic rate of TiO2. However, the synthesis methods of carbon-doped TiO2 photocatalytic materials are mostly performed in a laboratory, and generally require high cost, high temperature and high pressure or protective gas, which increase the preparation cost and are not conducive to large-scale industrial production of TiO2. The present disclosure provides a simple and low-cost method for preparing an efficient carbon-doped TIO2 (TiO2@C7H8O@C) photocatalyst, in which the photocatalyst could not only take full use of visible light, but also introduce defect sites on the surface of TiOz to fully absorb pollutants, and an interlayer of C?HsO also enhances dispersibility of the catalyst. In addition, the synthesized cataiyst could be applied to remove methanal in air. SUMMARY

[0005] The present disclosure provides an efficient TiOz@C7H8O@C photocatalyst prepared by a simple and low-cost method, and the method comprises decomposing an organic solvent phenyl ethanol adsorbed on a surface of TiOz in situ to carbon by calcinating the TiO2@C?H8O@C photocatalyst at a low temperature, wherein the carbon is uniformly doped on the surface of TiOz. The carbon doped on the surface of TiO? could not only effectively adsorb a target pollutant, but also modulate the band gap of TiOs, such that TiCh could fully absorb visible light, and the interlayer of C?HsO enhances the dispersibility of the catalyst. The obtained TiOz@C photocatalyst has higher photocatalytic activity.

[0006] The present disclosure provides a method for preparing an efficient photocatalyst TiO2@C / H8O@C responsive to visible light, and use of the photocatalyst in photocatalytic degradation of methanal (HCHO) in air, comprising:

[0007] (i) adding titanium tetrachloride (TiCI4) dropwise into phenylethanol (C / HaO) slowly to obtain a mixture, in which a reaction rate is controlled by adding dropwise slowly;

[0008] (i i) stl rri ng the mi xture at 50t® for 5 days for a react! on;

[0009] (ill) washing a suspension obtained after the reaction of step (li) several tim^ with ethanol, and centrifuging the suspension to obtain a light yellow solid T ICWCzHsO;

[0010] (iv) drying the light yellow solid TiCMgKzHgO in an oven at 60 eC for 24 h to obtain a I i ght yel I ow powder T i Oz@ C 7H sO;

[0011] (v) placing a certain amount of the light yellow powder TiCWCzHgO in a ceramic boat and heating the ceramic boat containing the light yellow powder TiCWCzHsO in a CVD furnace under conditions of a calcination temperature of 100 eC, a high-temperature treatment atmosphere of air, an operating pressure of atmospheric pressure, and a reaction time of 2 h, to obtain the efficient photocatalyst TiOz@C7HsO@C responsive to visible light; and

[0012] (vi) photocatalytic degradation of HCHO by using TiO2@C7HsO@C:

[0013] spraying a suspension of the TiO2@C?H8O@C catalyst onto a piece of cotton cloth in a sealed device, and then spraying an HCHO solution onto a surface of the cotton cl oth;

[0014] volatilizing HCHO to evenly diffuse HCHO in the sealed device by a fan configured inside the sealed dance;

[0015] irradiating the cotton cloth with four 5W L E Ds; and

[0016] monitoring and recording an amount of HCHO in the sealed device online by a formaldehyde sensor.

[0017] T he present disclosure has the following beneficial effects:

[0018] In the present disclosure, TiO2@C?H8O@C photocatalyst is prepared simply, at low cost and with low energy consumption, under conditions of a low temperature, normal atmospheric pressure and no protective gas. A thin layer of carbon on the surface of TiO2@C?HsO@C photocatalyst could effectively adsorb a target pollutant in an environment and reduce mass transfer resistance between TiOz and the target pollutant. The thin layer of carbon on the surface of TiO2@C7HsO@C photocatalyst introduces defect sites on the surface of TiOz, thus reducing the energy band of TiOz and enabling it to fully absorb visible light. Meanwhile, an interlayer of GHsO enhances the dispersibility of the carbon and significantly improves the photocatalytic performance of TiOz.

[0019] The present disclosure is to provide the simple and low-cost method for preparing an ultrafine titanium dioxide photocatalyst and use of the photocatalyst in photocatalytic degradation of methanal. DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 shows transmission electron microscope images of phenyl ethanol supporting titanium dioxide (TiOz@C7HsO) prepared according to Example 1.

[0021] FIG. 2 shows transmission electron microscope images of carbon-doped TiOz (TiO2@C?H8O@C) prepared according to Example 1.

[0022] FIG. 3 shows an X-ray diffraction (X RD) pattern of TKMKzHsO and TiO2@C7HgO@C (calcined at various temperatures) prepared according to Example 1.

[0023] FIG. 4 shows Raman spectrum of TiOz@C7HsO and TiO2@C7HsO@C (calcined at various temperatures) prepared according to Example 1.

[0024] FIG. 5 shews diagrams of a device for degrading HCHO by TIOz@C?H8O@C prepared accord! ng to E xample 1.

[0025] FIG. 6 shows a kinetic graph of photocatalytic degradation of methanal by TiCWCzHgO andTIO2@C7HsO@C (calcined at various temperatures) prepared according to Example 1.

[0026] FIG. 7 shows an ultraviolet absoiption spectrum of TiCWC / HsO and TiOz@C7HsO@C (calcined at various temperatures) prepared according to Example 1.

[0027] FIG. 8 shows Taue graph of Kubelka-Munk equation of TiOz@C?H8O and TiOz@C7H8O@C (calcined at various temperatures) prepared according to Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The technical solutions of the present disclosure are not limited to the specific examples listed below, but also includes any combination among them.

[0029] Example 1

[0030] An ultrafine photocatalyst TiO2@C7HsO@C prepared by a simple and low-cost method, consisted of:

[0031] carbon, which is doped in situ on a surface of TiCh to form an ultra-thin layer having active sites, and fully absorbs visible light and a target pollutant and

[0032] an interlayer of CyHsO, which enhances dispersibility of the ultrafine photocatalyst,

[0033] wherein the ultrafine photocatalyst TiO2@C7H8O@C has excellent performance of photocatalytic degradation of methanal.

[0034] Example2

[0035] A simple and low-cost method for preparing the ultrafine photocatalyst TiO2@C7HsO@C according to Example 1, and a test for photocatalytic degradation of methanal (H C H O) were performed as fol I ows: (i) titanium tetrachloride (TiCU) was added dropwise into phenyl ethanol (CyHsO) slowly to obtain a mixture, in which a reaction rate was controlled by adding dropwise slowly; (ii) the mixture was stirred at 501© for 5 days for a reaction; (iii) a suspension obtained after the reaction of step (ii) was washed several times with ethanol and then centrifuged to obtain a light yellow solid TIO2@C?HsO; (iv) the light yellow solid TiCWC / HsO was dried In an oven at 60±® for 24 h to obtain a I ight yel I ow powder T i Oz@ C ?H gO; (v) a certain amount of the light yellow powder TiCWC / HsO was placed in a ceramic boat, and the ceramic boat containing the light yellow powder TiCWC / HgO was heated in a CVD furnace under conditions of a calcination temperature of 100 eC, a high-temperature treatment atmosphere of air, an operating pressure of atmospheric pressure and a reaction time of 2 h, obtaining the efficient photocatalyst TiO2@C7HsO@C responsive to visible light; and (vi) photocatalytic degradation of HCHO by TiO2@C?H8O@C: a suspension of the TiO2@C7HsO@C catalyst was sprayed onto a piece of cotton cloth in a sealed device, and an HC HO solution was sprayed onto a surface of the cotton cloth; HCHO was volatilized to evenly diffuse in the sealed device by a fan configured inside the sealed device; the cotton cloth was Irradiated with four 5W L E Ds; and an amount of HCHO in the sealed device was monitored and recorded online by a formaldehyde sensor.

[0036] Examples

[0037] The present example differs from Example 2 in that the calcination temperature in step (v) i s 150 eC. Other steps are the same as those i n E xampl e 2.

[0038] Example4

[0039] The present example differs from Example 2 or 3 in that the calcination temperature in step (v) i s 175 eC Other steps are the same as those i n E xampl e 2 or 3.

[0040] Examples

[0041] The present example differs from Example 2 to 4 in that the calcination temperature in step (v) i s 200 eC. Other steps are the same as those i n E xampl e 2 to 4.

[0042] Example6

[0043] T he present exampl e differs from E xampl e 2 to 5 I n that the cal ci nati on temperature i n step (v) is 225 eC Other steps are the same as those in Example 2 to 5.

[0044] Example?

[0045] T he present exampl e differs from E xampl e 2 to 6 i n that the cal ci nati on temperature I n step (v) i s 250 eC. Other steps are the same as those I n E xampl e 2 to 6.

[0046] Examples

[0047] T he present ecampl e differs from E xampl e 2 to 7 i n that the cal ci nati on temperature i n step (v) I s 300 C. Other steps are the same as those i n E xampl e 2 to 7.

[0048] In order to prove the beneficial effect of the present disclosure, the inventors synthesized TiO2@C7H8O@C-150 for visible light The absorption edges of TiO2@C7H8O@C-150, TiO2@C7H8O@C-175, and Ti02@C7H80@C-200 are at 419 nm, 437 nm and 398 nm respectively, which have obvious red shift compared with 374 nm of TiCWCvHsO (see FIG. 7), wherein the absorption edge of TiO2@C7H8O@C-175 has a red shift by 437 nm. Taue graph is obtained according to Kubeika-Munk formula Ah®2 = A(h®g). As shown in FIG. 8, the band gap energy (Eg) values of TiO2@C7H8O, TiO2@C7H8O@C-150, TiO2@C7H8O@C-175 andTI02@C7H80@C-200 are3.07 eV, 2.65 eV, 2.51 eV and 2.78 eV, respectively. It was found that the Eg values of various TiO2@C7H8O@Cs are smaller than that of the original TiO2@C7HgO (see FIG. 8), in which the Eg value of TIO2@C7H8O@C-175 is the lowest. This is consistent with the results of photocatalytic degradation test, which shows that the energy band structure of TiO2@C7HsO could be effectively reduced by calcination, allowing for full use of the energy of visible light. It means that carbon sites are evenly doped on the surface of TIO2, forming a novel hybrid structure, which enriches the defect active sites, reduces the band gap of TiO2, and is beneficial to the dual functions of physical adsorption and chemical degradation. In conclusion, it is demonstrated that the photocatalyst TiO2@C7HsO@C synthesized by a simple and low-cost method of the present disclosure could take full use of visible light to remove methanal in air.

Claims

1. An ultrafine photocatalyst TiO2@C7HsO@C prepared by a simple and low-cost method, comprising,carbon, which is doped in situ on a surface of TiCh to form an ultra-thin layer having active sites, and fully absorbs visible light and a target pollutant, andan interlayer of C?HgO, which enhances dispersibility of the ultrafine photocatalyst;wherein the ultrafine photocatalyst TiO2@C7HsO@C has excellent performance of photocatalytic degradation of methanal.

2. A simple and low-cost method for preparing the ultrafine photocatalyst TiO2@C?H8O@C of claim 1, and a test for photocatalytic degradation of methanal (HCHO), comprising steps of:(i) adding titanium tetrachloride (TiCU) dropwise into phenylethanol (CyHsO) slowly to obtain a mixture, in which a reaction rate is controlled by adding dropwise slowly;(II) stirring the mixture obtained in step (i) at 50ii for 5 days for a reaction;(ill) washing a suspension obtained after the reaction of step (ii) several times with ethanol and centrifuging the suspension to obtain a light yellow solid TiO2@C?H8O;(iv) drying the light yellow solid TiCWCzHsO in an oven at 60±g for 24 h to obtain a light yellow powderTiO2@C7HsO;(v) placing a certain amount of the light yellow powder TiO2@CzH8O in a ceramic boat, and heating the ceramic boat containing the light yellow powder TiCWCvHgO in a CV D furnace under conditions of a calcination temperature of 100 eC, a high-temperature treatment atmosphere of air, an operating pressure of atmospheric pressure, and a reaction time of 2h, to obtain an efficient photocatalyst TiO2@C7HgO@C responsive to visible light; and(vi) photocatalytic degradation of HCHO by using TiO2@C7HsO@C:spraying a suspension of the TiO2@C7HgO@C catalyst onto a piece of cotton cloth in a sealed device, and spraying an HCHO solution onto a surface of the cotton cloth;volatilizing HCHO to evenly diffuse in the sealed device by a fan configured inside the sealed device;irradiating the cotton cloth with four 5W L E Ds; andmonitoring and recording an amount of HCHO in the sealed device online by a formaldehyde sensor.

3. The method of claim 2, wherein the calcination temperature in step (v) is 150 eC.

4. The method of claim 2, wherein the calcination temperature in step (v) is 175 eC.

5. The method of claim 2, wherein the calcination temperature in step (v) is 200 eC.

6. The method of claim 2, wherein the calcination temperature in step (v) is 225 eC.

7. The method of claim 2, wherein the calcination temperature in step (v) is 250 eC.

8. The method of claim 2, wherein the calcination temperature in step (v) is 300 eC

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