TiO (titanium dioxide) 2 Preparation method of ZnO heterogeneous nanofiber high-efficiency photocatalyst
Technical Field
The invention belongs to the field of photocatalyst preparation, and in particular relates to TiO 2 A preparation method of ZnO heterogeneous nanofiber high-efficiency photocatalyst.
Background
With the rapid development of modern industry, the energy crisis and environmental pollution problem are increasingly aggravated, and the development and utilization of clean high-efficiency energy become urgent for various countries. Solar energy is taken as a renewable clean energy source, so how to effectively utilize the solar energy becomes a hot spot of current research. The photocatalysis technology has the advantages of directly absorbing solar energy at room temperature to drive reaction, and the like, and becomes an ideal production technology for directly or indirectly converting solar energy into human available energy. The heart of the application of photocatalytic technology is the development of photocatalysts, of which hundreds have been reported in the last decades of development. However, the photocatalyst reported at present has the problems of narrow photoresponse wavelength, poor stability, low efficiency and the like, and severely restricts the large-scale use of the photocatalyst. Therefore, the development of the high-efficiency photocatalyst is heavy and far away.
In order to solve the problems of the photocatalyst, researchers have made a great deal of research, and the research is mainly conducted from the aspects of material structure, component optimization and the like. Optimization of material structure mainly refers to changing micro-morphology features of a catalyst to enable the catalyst to haveHigh specific surface area and stable geometric structure, and can raise the light capturing rate and reactant adsorbing capacity. The research shows that the one-dimensional nanofiber structure has high-efficiency and stable photocatalytic activity due to the unique geometric structure and the high specific surface area. The component optimization reduces the forbidden bandwidth and prolongs the service life of the photogenerated carriers by changing the energy band structure. Mainly comprises non-metal element doping, semiconductor compounding, noble metal loading and the like. The coupling of different semiconductor materials can effectively block the recombination of photon-generated carriers and enhance the utilization rate of solar energy. TiO (titanium dioxide) 2 Semiconductor photocatalyst materials which are the most representative with ZnO have been reported in literature as the research work of two kinds of composite semiconductor photocatalysts alone or in combination, but TiO with nanofiber structure 2 The ZnO composite photocatalyst material has not been reported yet.
Disclosure of Invention
The invention aims to solve the problems of low solar energy utilization rate, low photocatalytic efficiency and the like of the traditional photocatalyst and provides a TiO (titanium dioxide) 2 Preparation method of ZnO heterogeneous nanofiber high-efficiency photocatalyst and prepared TiO 2 The ZnO heterogeneous nanofiber visible light photocatalyst has high specific surface area, and can efficiently decompose water to prepare hydrogen under the irradiation of simulated sunlight.
The above object of the present invention is achieved by the following means: tiO (titanium dioxide) 2 The preparation method of the ZnO heterogeneous nanofiber high-efficiency photocatalyst comprises the following steps:
1) TiO is prepared by electrostatic spinning 2 A nanofiber;
2) TiO is mixed with 2 The nanofiber is placed in an atomic layer deposition system, diethyl zinc and water are used as raw materials, znO grows layer by layer after deposition circulation, and ZnO modified TiO is obtained 2 Heterogeneous nanofiber high-efficiency photocatalyst material.
The invention modifies TiO by ZnO 2 The nano fiber photocatalyst with one-dimensional structure is prepared from heterogeneous nano fibers, and the photocatalyst can strengthen the photocatalytic performance of the catalyst from two directions simultaneously, so that the problems of poor stability and poor efficiency of the traditional photocatalyst are solvedLow, etc. The TiO is as described above 2 In the preparation method of the ZnO heterogeneous nanofiber high-efficiency photocatalyst, the cycle times in the atomic layer deposition technology are 50-200 times. Too many cycles can result in too thick ZnO deposited, impeding light absorption and thus decreasing photocatalytic performance, while too little deposition results in insufficient interfacial charge transfer capability and also decreasing photocatalytic performance.
The TiO is as described above 2 In the preparation method of the ZnO heterogeneous nanofiber high-efficiency photocatalyst, tiO is prepared by electrostatic spinning 2 The nanofiber specifically comprises the following steps:
polyvinyl pyrrolidone (PVP) and tetrabutyl titanate (TBOT) are used as raw materials, absolute ethyl alcohol and glacial acetic acid are used as solvents, and precursor spinning solution is formed;
electrostatic spinning the precursor spinning solution to obtain solid precursor fibers;
calcining the solid precursor fiber to TiO at high temperature 2 A nanofiber.
Preferably, 3-6g of butyl titanate is added to 1g of PVP when preparing the precursor spinning solution.
Preferably, the volume ratio of the absolute ethyl alcohol to the glacial acetic acid is 2-3:1 when the precursor spinning solution is prepared.
Preferably, the distance between the anode and the cathode in the electrostatic spinning is 12cm-18cm, and the high voltage is 15kV-20kV.
Preferably, the drying temperature is 50-70 ℃.
Preferably, the high-temperature calcination temperature is 480-520 ℃, the heat preservation is carried out for 1-3 hours, and the heating rate is 0.5-3 ℃/min.
The TiO is as described above 2 In the preparation method of the ZnO heterogeneous nanofiber high-efficiency photocatalyst, the prepared TiO 2 The ZnO heterogeneous nanofiber high-efficiency photocatalyst is of a one-dimensional nanofiber structure and is prepared from TiO (titanium dioxide) 2 And ZnO.
The TiO is as described above 2 In the preparation method of the ZnO heterogeneous nanofiber high-efficiency photocatalyst, the prepared TiO 2 The crystal form of (C) is mainly anatase phase, and the crystal form of ZnO is sphalerite phase.
The TiO is as described above 2 ZnO heterogeneous nanofiber high-efficiency photocatalystIn the preparation method of (1), the atomic percentages of Zn, O and Ti are respectively 3.05-7.45 at%, 58.49-69.49 at% and 23.06-38.46 at%.
The invention also provides the TiO 2 The ZnO heterogeneous nanofiber high-efficiency photocatalyst is applied to hydrogen production by photolysis of water.
TiO 2 The application of the ZnO heterogeneous nanofiber high-efficiency photocatalyst in the high-efficiency photocatalyst is to apply TiO (titanium dioxide) 2 The ZnO heterogeneous nanofiber high-efficiency photocatalyst is dispersed in a decomposed substance to perform catalytic reaction under light irradiation, wherein the decomposed substance is an aqueous substance (the aqueous substance can be water, saline water and other substances containing a proper amount of water, namely, the aqueous substance contains water in a liquid state and can enable the nanofiber serving as a catalyst to be dispersed in the liquid state).
The light source used for producing hydrogen by photolysis of water is a xenon lamp light source.
Compared with the prior art, the invention has the following effects:
1. the invention realizes TiO 2 Preparing ZnO heterogeneous nanofiber high-efficiency photocatalyst;
2.TiO 2 the ZnO heterogeneous nanofiber photocatalyst has a one-dimensional nanofiber structure with a high specific surface, and the two semiconductor composite photocatalysts can effectively inhibit the recombination of photo-generated electron-hole pairs and cooperatively strengthen the photocatalytic performance;
3.TiO 2 the ZnO heterogeneous nanofiber photocatalyst has the advantages of enhanced charge separation efficiency, higher solar energy utilization rate and better application prospect in solving the environmental problems and energy crisis.
Drawings
FIG. 1 shows TiO according to example 1 of the present invention 2 A nanofiber low power Scanning Electron Microscope (SEM) image;
FIG. 2 shows the TiO of example 1 of the present invention 2 High-power Scanning Electron Microscope (SEM) images of the nanofibers;
FIG. 3 shows the TiO of example 1 of the present invention 2 X-ray diffraction (XRD) pattern of nanofibers;
FIG. 4 shows the TiO of example 1 of the present invention 2 Low-power Scanning Electron Microscope (SEM) image of ZnO heterogeneous nanofibers;
FIG. 5 shows the TiO of example 1 of the present invention 2 High-power Scanning Electron Microscope (SEM) image of ZnO heterogeneous nanofiber;
FIG. 6 shows the TiO of example 1 of the present invention 2 X-ray diffraction (XRD) pattern of ZnO hetero-nanofibers;
FIG. 7 shows the TiO of example 1 of the present invention 2 Transmission Electron Microscopy (TEM) image of ZnO heterogeneous nanofibers;
FIG. 8 shows the TiO of example 1 of the present invention 2 Selecting An Electron Diffraction (SAED) diagram of the ZnO heterogeneous nanofiber;
FIG. 9 shows the TiO of example 1 of the present invention 2 High Resolution Transmission Electron Microscope (HRTEM) image of ZnO heterogeneous nanofibers;
FIG. 10 shows the TiO of example 1 of the present invention 2 An amplified High Resolution Transmission Electron Microscope (HRTEM) image of the ZnO heterogeneous nanofiber;
FIG. 11 shows the TiO of example 1 of the present invention 2 An amplified High Resolution Transmission Electron Microscope (HRTEM) image of the ZnO heterogeneous nanofiber;
FIG. 12 shows the TiO of example 1 of the present invention 2 Energy spectrum (EDS) plot of ZnO heterogeneous nanofibers;
FIG. 13 shows TiO according to example 1 of the present invention 2 Nano fiber and TiO with different atomic layer deposition times 2 A graph of efficiency contrast of the change of photocatalytic hydrogen production amount of the ZnO heterogeneous nanofiber material along with illumination time;
FIG. 14 shows TiO according to example 1 of the present invention 2 Nano fiber and TiO with different atomic layer deposition times 2 And (3) comparing the photocatalytic hydrogen production efficiency of the ZnO heterogeneous nanofiber material.
Detailed Description
The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described with reference to the accompanying drawings, but the present invention is not limited to these embodiments.
Example 1
0.7g polyvinylpyrrolidone (PVP) was dissolved in 7ml ethanol andand (3) in 3ml of acetic acid mixed solvent, magnetically stirring for 6 hours to obtain a uniform PVP solution, slowly dropwise adding 3ml of butyl titanate (TBOT), and continuously strongly stirring for 2 hours to obtain PVP/TBOT precursor spinning solution. Spinning under the condition of electric spinning with voltage of 18kV and distance of 15cm to obtain precursor fiber, and drying in a constant temperature oven at 60 ℃ to obtain cured precursor fiber. Calcining the prepared precursor fiber in a muffle sintering program furnace at 500 ℃ at a heating rate of 1 ℃/min for 2h, and cooling to room temperature along with the furnace to obtain TiO 2 And (5) the nanofiber is preserved for standby. FIGS. 1 and 2 show the prepared TiO 2 SEM pictures of the nanofibers under different magnification show that the prepared material is a high-purity nanofiber material. FIG. 3 is a corresponding X-ray diffraction pattern showing that the nanofibers produced are anatase TiO 2 A material.
0.5g of prepared TiO is taken 2 The nano fiber is placed in an atomic layer deposition system, and after 150 cycles, the nano fiber is arranged in TiO 2 ZnO with a certain thickness is wrapped on the surface of the nanofiber, so that TiO is obtained 2 ZnO heterogeneous nanofiber photocatalyst. The TiO prepared in this example 2 The ZnO hetero-nanofibers were subjected to Scanning Electron Microscopy (SEM) at different magnifications, the results are shown in fig. 4 and 5, indicating that the prepared materials are still high purity nanofibers. FIG. 6 is a corresponding X-ray diffraction pattern (XRD) showing that the nanofibers produced are TiO 2 ZnO composite material. FIG. 7 shows the prepared TiO 2 TEM image of ZnO heterogeneous nanofiber, again illustrating that the material is a typical one-dimensional nanofiber structure. FIG. 9 is a High Resolution Transmission Electron Micrograph (HRTEM) of the corresponding nanofiber again demonstrating the nanofiber as composed of ZnO and TiO 2 Composition is prepared. FIG. 10 is a corresponding selected electron diffraction pattern (SAED) demonstrating that the nanofibers are composed of ZnO and TiO 2 A polycrystalline structure. FIG. 10 shows the prepared TiO 2 TiO in ZnO heterogeneous nanofiber 2 Corresponding magnified high resolution transmission electron micrographs, confirming TiO 2 Is in anatase phase. FIG. 11 shows the prepared TiO 2 The amplified high-resolution transmission electron microscope photo corresponding to ZnO in the ZnO heterogeneous nanofiber proves that ZnO is zinc blendeAnd (3) a mineral phase. Fig. 12 is a corresponding Elemental Distribution Spectroscopy (EDS) chart illustrating that the material is composed of three elements, ti, O, and Zn, with atomic percentages of Zn, otti of 4.32at.%,66.84at.% and 28.84at.%, respectively.
And weighing 0.01g of the prepared catalyst, dispersing in 40ml of distilled water, performing ultrasonic dispersion for 15min, adding 10ml of methanol as a sacrificial agent, adopting a 300W xenon lamp as a simulated sunlight light source, detecting generated hydrogen by an online gas chromatograph, detecting once every 30min, and ending the test after 6 hours.
Example 2
The difference from example 1 is that the deposition cycle of the ZnO layer is 50 times, and other processes are the same as in example 1, and will not be repeated here.
Example 3
The difference from example 1 is that the deposition cycle of the ZnO layer is 100 times, and other processes are the same as in example 1, and will not be repeated here.
Example 4
The difference from example 1 is that the deposition cycle of the ZnO layer is 200 times, and other processes are the same as in example 1, and will not be repeated here.
Comparative example
The nanofibers produced according to the method of example 1 were anatase TiO 2 A material. I.e. the comparative example did not deposit ZnO.
The results of the hydrogen production test of the catalysts prepared in examples 1 to 4 and comparative example are shown in fig. 13, and fig. 13 is a graph showing the change of hydrogen production with time of irradiation, and the increase of the surface hydrogen production with time is linearly increased. FIG. 14 is a graph showing comparison of hydrogen production efficiency of different photocatalysts, illustrating the prepared TiO 2 The ZnO heterogeneous nanofiber has obviously improved photocatalysis performance, and the hydrogen production efficiency can reach 1190.9 mu mol g -1 h -1 Compared with pure phase TiO 2 The hydrogen production efficiency is improved by more than 6.5 times. As can be seen from fig. 13 and 14, the hydrogen production efficiency of the catalyst produced was the best when the deposition cycle was 150 times.
The embodiments herein are not exhaustive of the values of points in the technical scope of the invention claimed, and new technical solutions formed by equivalent substitution of single or multiple technical features in the technical solutions of the embodiments are also within the scope of the invention claimed, and all the parameters involved in the solutions of the invention are not mutually and non-replaceable unique combinations unless specifically stated.
The specific embodiments described herein are offered by way of example only to illustrate the spirit of the invention. Various modifications or additions to the described embodiments may be made by those skilled in the art to which the invention pertains or may be substituted in a similar manner without departing from the spirit of the invention or beyond the scope of the appended claims.
While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.