CN111607808A

CN111607808A - Core-shell structure of ultrathin metal organic framework material UiO-67 coated titanium dioxide nanorod and preparation method thereof

Info

Publication number: CN111607808A
Application number: CN202010426404.2A
Authority: CN
Inventors: 田洋; 王学维
Original assignee: Capital Normal University
Current assignee: Capital Normal University
Priority date: 2020-05-19
Filing date: 2020-05-19
Publication date: 2020-09-01
Anticipated expiration: 2040-05-19
Also published as: CN111607808B

Abstract

The invention discloses a core-shell structure of an ultrathin metal organic framework material UiO-67 coated titanium dioxide nanorod and a preparation method thereof, which are used for improving the photoelectric catalytic performance. Firstly, synthesizing nano-rod-shaped titanium dioxide on a conductive glass substrate by adopting a simple one-step hydrothermal method, and then coating an ultrathin UO-67 nano shell layer on the surface of a titanium dioxide nano-rod. The preparation method is simple, novel and highly controllable. The synthesized core-shell material of the UiO-67 coated titanium dioxide nanorod is beneficial to photo-generated carrier separation, enhances the photoelectric conversion efficiency, can improve the performance of a photo-anode for photoelectrocatalysis water decomposition, and meets the requirements of the latest clean energy and sustainable energy.

Description

Core-shell structure of ultrathin metal organic framework material UiO-67 coated titanium dioxide nanorod and preparation method thereof

Technical Field

The invention relates to the field of preparation of a photo-electrolysis water anode material, in particular to a core-shell nanorod of an ultrathin metal organic framework material (UiO-67) coated titanium dioxide nanorod, a preparation method of the core-shell nanorod and an effect of improving the photoelectric catalytic performance of the core-shell nanorod.

Background

Hydrogen is a clean, efficient and renewable novel energy source. At present, photoelectrocatalytic water decomposition is the acquisition of hydrogenOne potential method of gas is to convert solar energy into green, pollution-free hydrogen energy by using this technology. In the photoanode part of photoelectrocatalysis, titanium dioxide (TiO)₂) Is one of the most common materials, mainly due to TiO₂The corrosion inhibitor has the advantages of no toxicity, low price, strong corrosion resistance, high stability, thorough decomposition and no secondary pollution. However, TiO₂The photo-generated electron-hole recombination probability is high, the light absorption efficiency is low, and the catalysis effect is not ideal, so that the photo-generated electron-hole recombination method is greatly limited in photoelectrocatalysis. Research shows that the titanium dioxide and other materials are compounded to form a heterostructure, so that the photoelectric separation efficiency of the titanium dioxide can be improved.

Metal organic frameworks (hereinafter referred to as MOFs) are coordination compounds formed by metal oxygen-containing groups and organic ligands, and are widely used because of their advantages of high specific surface area, high porosity, adjustable structure and the like. Currently, MOFs have attracted extensive attention in the field of photoelectrocatalysis, but a single MOF material has the problem of too high electron-hole recombination rate, the conductivity is not high, and the utilization efficiency of light is also low due to too large volume of some MOFs, so that the photoelectrocatalysis performance of some MOFs is weakened to a certain extent. In order to further improve the utilization efficiency of the photoelectric catalyst to solar energy and reduce the recombination rate of 'electron-hole', the method is implemented in TiO₂An ultra-thin MOF layer (2-3 nm thick) is formed on the surface of the nano-rod, and the chemical component of the MOF layer is UiO-67 (see figure 1a), so that TiO is improved₂The performance of photoelectrocatalysis.

Disclosure of Invention

In view of the problems of the prior art, it is an object of the present invention to provide a UO-67 coated TiO₂Method for preparing core-shell structure of nano rod for improving TiO₂The nano-rod has the performance of photoelectrocatalysis water decomposition, and the preparation method comprises the following steps:

1) pretreating a fluorine-doped tin oxide conductive glass substrate (hereinafter referred to as FTO substrate, 4cm multiplied by 1cm multiplied by 0.11 cm): and cleaning the substrate by ultrasonic bath (ultrapure water, ethanol, acetone and ultrapure water) for 15 minutes in sequence, and drying the FTO substrate in an oven at 80 ℃ for 30 minutes for later use after cleaning.

2) Preparation of hydrochloric acid solution: 6mL of concentrated hydrochloric acid is dissolved in 6mL of deionized water, and the mixture is stirred for 5 minutes after being mixed until the mixture is uniformly mixed, wherein the hydrochloric acid concentration is 36-38%.

3)TiO₂Preparing a precursor solution: 200. mu.L of an isobutyl titanate solution was added to the solution prepared in step 2) and stirred for 3 hours.

4) Subjecting the TiO prepared in step 3)₂Adding the precursor solution into a polytetrafluoroethylene lining of a 15 ml high-pressure reaction kettle, putting the pretreated FTO substrate into the high-pressure reaction kettle, screwing a kettle cover down with the conductive surface facing downwards, putting the reaction kettle into an electrothermal blowing dry box at 170 ℃, and keeping for 10 hours.

5) Taking out the reaction kettle, cooling to room temperature, and taking out the white TiO₂The FTO substrate of (1) was repeatedly washed with absolute ethanol and ultrapure water.

6) Putting the FTO substrate obtained in the step 5) into a muffle furnace, raising the temperature of the muffle furnace to 450 ℃ at the temperature rise rate of 3 ℃/min, keeping the temperature for 3 hours, naturally cooling to room temperature, taking out the product to obtain rutile-phase TiO₂The nanorods were grown on an FTO substrate.

7)ZrCl₄Preparing a precursor solution: 0.067 to 0.25 mmol of ZrCl₄Ultrasonically dispersed in 10mL of DMF, or ethanol, or oleylamine, preferably 0.1 mmol to 0.2 mmol, more preferably 0.125 mmol, and the solvent is preferably DMF.

8) Preparation of UiO-67 precursor solution: 0.087 to 0.35 moles of 4, 4-biphenyldicarboxylic acid (BPDC) was added to the solution of step 7), preferably 0.1 to 0.25 moles, more preferably 0.175 moles, and stirred for 30 minutes.

9) Adding the UiO-67 precursor solution prepared in the step 8) into a polytetrafluoroethylene lining of a 15 ml high-pressure reaction kettle, putting the FTO substrate treated in the step 6) into the inner lining, screwing down a kettle cover, putting the reaction kettle into an electrothermal blowing dry box at 120 ℃, and keeping for 12-36 hours, preferably 12 hours

10) Taking out the reaction kettle and cooling to room temperatureOpening the kettle cover, taking out the FTO substrate, washing the substrate with DMF and absolute ethyl alcohol three times respectively, and then drying in an oven at 50 ℃ for 1 hour to obtain the TiO coated by the ultra-thin layer of UiO-67₂The nanorods were grown on an FTO substrate.

Another object of the present invention is to provide a photoanode material for photoelectrocatalytic decomposition of water, which is prepared by the above preparation method, and the TiO₂The height of the nano rod is about 5 microns, the diameter is about 50-60 nanometers, and the thickness of the ultra-thin UiO-67 shell layer is about 2-3 nanometers. The UiO-67 is coated with TiO₂The nanorod photoanode can effectively increase the charge separation efficiency of photoelectrocatalysis in the electrolyte with full pH value, and improve the photoelectrocatalysis performance.

Advantageous effects

UiO-67 coated TiO according to the invention₂The nano-rods uniformly and vertically grow on the surface of the FTO conductive glass, and the thickness of the UiO-67 layer is about 2-3 nm. The generated nano rod of the titanium dioxide coated by the UiO-67 has stronger oxidation potential and reduction potential, can further improve the charge separation efficiency and improve the performance of photoelectrocatalysis water decomposition. Photocurrent density at full pH range without sacrificial agent compared to pure TiO₂The nano rod is improved by about 3 times. The preparation method of the photoelectric anode has the advantages of simple process, mild reaction conditions and environmental friendliness.

Drawings

FIG. 1 is a chemical structure of UiO-67 (a); schematic diagram (b) of the synthesized product.

FIG. 2 shows TiO 2 on the FTO substrate obtained in step 6) of example 1₂X-ray diffraction pattern of nanorod samples.

FIG. 3 shows TiO 2 on the FTO substrate obtained in step 6) of example 1₂Scanning electron micrographs of nanorods at different magnifications (panels a and b); TiO 2₂Transmission electron microscope image (c) and high resolution transmission electron microscope image (d) of nanorods.

FIG. 4 shows the UiO-67-coated TiO obtained in step 10) of example 1₂Scanning electron microscope (a) and high-resolution transmission electron microscope (b) of the nano-rods; x-ray energy scattering spectroscopy (c); distribution diagram of three elements of titanium (d), oxygen (e) and zirconium (f) in sampleLike this.

FIG. 5 shows TiO obtained in step 6) and step 10) of example 1₂Nanorod and UiO-67 coated TiO₂Infrared contrast plot of nanorods.

FIG. 6 shows the step 6) of example 1 to obtain pure TiO₂The nanorods were used as a photocurrent density map of a photoelectrocatalytic photoanode.

FIG. 7 example 1 step 10) obtained UiO-67 coated TiO₂The nanorods were used as a photocurrent density map of a photoelectrocatalytic photoanode.

FIG. 8 shows a comparative example 1 in which TiO is coated with a layer of UiO-67 synthesized using ethanol and DMF as solvents, respectively₂The nanorods serve as the photocurrent density of the photoelectrocatalytic photoanode.

FIG. 9 is a graph showing comparative example 2 in which TiO is coated with a layer of UiO-67 synthesized using oleylamine and DMF as solvents, respectively₂The nanorods serve as the photocurrent density of the photoelectrocatalytic photoanode.

FIG. 10 shows a UiO-67 layer coated TiO synthesized in comparative example 3₂The nanorods serve as the photocurrent density of the photoelectrocatalytic photoanode.

FIG. 11 shows a layer of TiO coated with UiO-67 synthesized in comparative example 4₂The nanorods serve as the photocurrent density of the photoelectrocatalytic photoanode.

FIG. 12 shows UiO-67 coated TiO films obtained at different reaction times in comparative example 5₂The nanorods serve as the photocurrent density of the photoelectrocatalytic photoanode.

FIG. 13 shows the UiO-67-coated TiO obtained in step 10) of example 1₂Photoelectric conversion efficiency of the nanorods.

FIG. 14 shows UiO-67 coated TiO obtained in step 10) of example 1 at 1.50V (vs. standard hydrogen electrode)₂The nanorods are used as a curve of the change of theoretical values and measured values of the amount of gas generated by the photoelectrocatalytic decomposition of water with time.

Detailed Description

Hereinafter, the present invention will be described in detail. Before the description is made, it should be understood that the terms used in the present specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Accordingly, the description proposed herein is just a preferable example for the purpose of illustrations only, not intended to limit the scope of the invention, so it should be understood that other equivalents and modifications could be made thereto without departing from the spirit and scope of the invention.

Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to general and dictionary meanings, but interpreted based on the meanings and concepts corresponding to technical aspects of the present invention on the basis of the principle that the inventor is allowed to define terms appropriately for the best explanation. Accordingly, the description herein is of preferred examples for the purpose of illustration only and is not intended to limit the scope of the present invention, so it will be understood that other equivalent implementations and modifications may be made without departing from the spirit and scope of the present invention. Unless otherwise stated, the reagents and apparatus used in the following examples are commercially available products.

The specific experimental part is as follows: pure TiO₂Nanorod and UiO-67 coated TiO₂A method for preparing nano-rods. The samples obtained were characterized by the following techniques, respectively: an X-ray powder diffractometer, a transmission electron microscope, a scanning electron microscope, a high-resolution transmission electron microscope, an infrared spectrometer and an electrochemical workstation.

Example 1: UiO-67 coated TiO₂Preparation of nanorods

1) Preparation of FTO substrate: and cleaning the substrate by ultrasonic bath (ultrapure water, ethanol, acetone and ultrapure water) for 15 minutes in sequence, and drying the FTO substrate in an oven at 80 ℃ for 30 minutes for later use after cleaning.

2) Preparation of hydrochloric acid solution: 6mL of concentrated HCl was dissolved in 6mL of deionized water, mixed and stirred for 5 minutes until it was well mixed.

3)TiO₂Preparing a precursor solution: adding 200 mu L of isobutyl titanate solution into the solution prepared in the step 2) dropwise and stirringFor 3 hours.

4) Adding 12 ml of the solution obtained in the step 3) into a polytetrafluoroethylene lining of a reaction kettle, immersing the pretreated FTO substrate into the solution, wherein the conductive surface faces downwards, screwing down a kettle cover, putting the reaction kettle into an electrothermal blowing dry box at 170 ℃, and keeping for 10 hours.

5) And taking out the reaction kettle, naturally cooling the reaction kettle to a room temperature state, opening the kettle cover, pouring out the supernatant, taking out the FTO substrate, and washing away the surface precipitate by using absolute ethyl alcohol and deionized water.

7)ZrCl₄Preparing a precursor solution: 0.125 mmol of ZrCl₄Ultrasonically dispersed into 10mL of DMF.

8) Preparation of UiO-67 precursor solution: 0.175 mmol of 4, 4-biphenyldicarboxylic acid (BPDC) was added to step 7) and stirred for 30 minutes.

9) Adding the UiO-67 precursor solution prepared in the step 8) into a polytetrafluoroethylene lining of a 15 ml high-pressure reaction kettle, putting the FTO substrate obtained in the step 6) into the inner liner, screwing a kettle cover down with the conductive surface, putting the reaction kettle into an electrothermal blowing dry box at 120 ℃, and keeping for 12 hours.

10) Taking out the reaction kettle, cooling the reaction kettle to a room temperature state, opening a kettle cover, taking out the FTO substrate, respectively washing the substrate with DMF and absolute ethyl alcohol for three times, and then placing the substrate in an oven at the temperature of 50 ℃ for 1 hour to obtain the TiO coated by the ultra-thin layer of UiO-67₂The nanorods were grown on an FTO substrate.

FIG. 2 shows TiO 2 on the FTO substrate obtained in step 6) of example 1₂X-ray diffraction pattern of nanorod samples. It can be seen that the synthesized titanium dioxide was in the rutile phase, and no anatase phase was detected.

FIG. 3 shows TiO 2 on the FTO substrate obtained in step 6) of example 1₂Scanning electron micrographs of nanorods at different magnifications (panels a and b); from FIG. 3b IOne can see TiO₂The diameter of the nano rod is about 500-600nm, and the length of the nano rod is 5-6 μm. TiO 2₂Transmission electron microscope image (c) and high resolution transmission electron microscope image (d) of nanorods. The high resolution transmission electron microscope image in FIG. 3d shows rutile TiO phase₂The lattice fringes of (2). In image (d), a lattice spacing of 0.324 nm corresponds to TiO₂The (110) crystal face of (A), the lattice spacing of 0.295 nm corresponds to TiO₂The (001) plane of (a).

FIG. 4 is a scanning electron micrograph (a) and a high-resolution transmission electron micrograph (b) of the UO-67-coated titanium dioxide nanorods obtained in step 10) of example 1. Figure 4b shows a clear core-shell structure. In the inner core, a lattice spacing of 0.324 nm corresponds to TiO₂(110) A crystal face; the amorphous shell of the surface should be a layer of UiO-67 coated on the surface of the nanorod. The existence of Ti, O and Zr in the nanorods can be seen by X-ray energy scattering spectroscopy (FIGS. 4 c-4 f). The zirconium element was distributed mainly on the surface (fig. 4e), confirming that the surface amorphous layer should be UiO-67.

FIG. 5 shows pure TiO in step 6) and step 10)₂Nanorod and UiO-67 coated TiO₂Infrared contrast plot of nanorods. For comparison, the same test was also performed on the starting 4, 4-biphenyldicarboxylic acid (BPDC), and pure UiO-67 powder, as shown in fig. 5. The infrared spectrum of 4, 4-biphenyldicarboxylic acid (BPDC) was shown to be 2500-3000cm^-1There is a broad absorption band corresponding to the-OH vibration of the carboxyl group in BPDC. 1690cm^-1The peak at (a) is the characteristic-C ═ O vibration of the BPDC molecule. 1400 and 1600cm^-1The broad bands in between represent phenyl groups in BPDC. In FIG. 5, pure UiO-67 and UiO-67 coat TiO₂The infrared spectra of the nanorods all showed characteristic peaks for-C ═ O and phenyl, indicating the presence of BPDC linking groups in the samples. Pure UiO-67 and UiO-67 coated TiO ₂2500 + 3000cm in two samples of the nanorod^-1The vibration of-OH at the carboxyl group disappeared, indicating that the hydrogen of-COOH was replaced by zirconium due to the coordination reaction. All the above results demonstrate that UiO-67 is successfully coated on TiO₂And (4) the surface of the nano rod.

FIG. 6 shows pure TiO prepared in step 6) of this example₂Nanorods useful as photocatalystsPhoto current density map of photo anode of decomposed water.

FIG. 7 shows the UiO-67 coated TiO obtained in step 10) of this example₂Nanorods used as photocurrent density profile of a photoelectrocatalytic photoanode. At 1.23 volts (versus a reversible hydrogen electrode), UiO-67 coated TiO₂The photocurrent density of the nanorods was approximately pure TiO₂Three times of the nano rod.

Comparative example 1: UiO-67 coated TiO using ethanol as solvent₂Preparation of nanorod material

The DMF solvent in step 7) of example 1 was changed to ethanol. 0.125 mmol of ZrCl was weighed₄And 0.175 mmol of 4, 4-biphenyldicarboxylic acid were added to ethanol and stirred for 30 minutes. Adding the mixed solution into a polytetrafluoroethylene lining of a 15 ml high-pressure reaction kettle, putting the pretreated FTO substrate into the mixed solution, screwing down a kettle cover, putting the reaction kettle into an electrothermal blowing dry box at 120 ℃, and keeping for 12 hours. Naturally cooling to room temperature, taking out the FTO substrate, washing the FTO substrate with DMF and absolute ethyl alcohol for three times respectively, and then placing in an oven at 50 ℃ for 1 hour to obtain the TiO coated by UiO-67₂The nanorods were grown on an FTO substrate.

FIG. 8 shows the photocurrent density of the photo-anode synthesized with ethanol and DMF as solvents, respectively, for the photoelectrocatalytic decomposition of water. The photocurrent density of the product synthesized at 1.23 volts (relative to the reversible hydrogen electrode) with ethanol as solvent was much lower than the product prepared with DMF as solvent.

Comparative example 2: preparation of UiO-67 coated TiO using oleylamine as solvent₂Nano-rod

The DMF solvent in step 7) of example 1 was changed to oleylamine. 0.125 mmol of ZrCl was weighed₄And 0.175 mmol of 4, 4-biphenyldicarboxylic acid were added to oleylamine, and stirred for 30 minutes. Adding the mixed solution into a polytetrafluoroethylene lining of a 15 ml high-pressure reaction kettle, putting the pretreated FTO substrate into the mixed solution, screwing down a kettle cover, putting the reaction kettle into an electrothermal blowing dry box at 120 ℃, and keeping for 12 hours. Naturally cooling to room temperature, taking out the FTO substrate, and respectively flushing the FTO substrate with DMF (dimethyl formamide) and absolute ethyl alcoholWashed three times and then placed in an oven at 50 ℃ for 1 hour to obtain the UiO-67 coated TiO₂The nanorods were grown on an FTO substrate.

FIG. 9 shows the synthesis of UiO-67 coated TiO using oleylamine and DMF as solvents respectively₂The nanorods were used as photo-anode for photo-catalytic decomposition of water. The photocurrent density of the product synthesized at 1.23 volts (relative to the reversible hydrogen electrode) using oleylamine as the solvent was much lower than that of the product prepared using DMF as the solvent.

Comparative example 3: reduction of ZrCl₄And 4, 4-Biphenyldicarboxylic acid (BPDC) in the amount used to prepare UiO-67 coated TiO₂Nano-rod

ZrCl obtained in step 7) of example 1₄The addition amount of (a) was changed to 0.067 mmol; correspondingly, the amount of 4, 4-biphenyldicarboxylic acid (BPDC) added in step 8) of example 1 was changed to 0.087 mmol. The remaining procedure and procedure were the same as in example 1 to prepare a UiO-67 coated TiO₂And (4) nanorods.

FIG. 10 shows the UiO-67 coated TiO obtained in this example₂And the nano-rods are used for photoelectric current density when the photo-anode is used for photo-catalytically decomposing water. When ZrCl at 1.23 volts (vs. reversible hydrogen electrode)₄At 0.125 mmol of 4, 4-biphenyldicarboxylic acid and 0.175 mmol of 4, 4-biphenyldicarboxylic acid, the resulting UiO-67 coated TiO was obtained₂The photocurrent density of the nanorods was maximal.

Comparative example 4: increasing ZrCl₄And 4, 4-Biphenyldicarboxylic acid (BPDC) in the amount used to prepare UiO-67 coated TiO₂Nano-rod

ZrCl obtained in step 7) of example 1₄The addition amount of (a) was changed to 0.25 mmol; correspondingly, the amount of 4, 4-biphenyldicarboxylic acid (BPDC) added in step 8) of example 1 was changed to 0.35 mmol. The remaining procedure and procedure were the same as in example 1 to prepare UiO-67-coated TiO₂The nanorod of (4).

FIG. 11 shows the UiO-67 coated TiO obtained in this example₂And the nano-rods are used for photoelectric current density when the photo-anode is used for photo-catalytically decomposing water. When ZrCl at 1.23 volts (vs. reversible hydrogen electrode)₄In the case of an amount of 0.125 mmol and 4, 4-biphenyldicarboxylic acid of 0.175 mmol, the reaction mixture was obtainedTo UiO-67 coating TiO₂The photocurrent density of the nanorods was maximal.

Comparative example 5: preparation of UiO-67-coated TiO at different reaction times₂Nano-rod

Three comparative tests were carried out by adjusting the incubation time in step 4) of example 1 to 12, 24 and 36 hours, respectively. The remaining procedure and procedure were the same as in example 1, to prepare three different UiO-67 coated TiO materials₂And (4) nanorods.

FIG. 12 shows the preparation of UiO-67 coated TiO in an oven at different reaction times₂The nano rod material is used as the photocurrent density when the water photoanode is decomposed by photoelectrocatalysis. The photocurrent density was optimized for a product with a reaction time of 12 hours at 1.23 volts (versus a reversible hydrogen electrode).

Test examples: photoelectrochemical water splitting reaction

The electrochemical workstation (CHI 660D) of Beijing Hua science and technology Limited is adopted to measure various electrical properties of the sample, and a 350W xenon lamp adopts an optical filter (400-. The products in different embodiments are respectively used as working electrodes (photo-anodes), the exposure area is 1.0 square centimeter, and the photo-current density and the photoelectric conversion efficiency of the photoelectrocatalysis decomposed water are respectively represented.

Electrochemical testing was performed using a three-electrode system with silver/silver chloride as the reference electrode, a platinum sheet (1 square millimeter surface area) as the cathode, and 1 mole/liter sodium hydroxide as the electrolyte solution (pH 14). The chronoamperometric (I-t) curve was characterized on an electrochemical workstation (CH Instruments660D) at a scan rate of 50 mv/sec).

According to the nernst equation: e_RHE＝E_Ag/AgCl+0.098+0.059 × pH (standard potential of Ag/AgCl electrode at 25 ℃ 0.1976V) E_RHE＝E_Ag/AgC+0.1976+0.059 ×13.6＝E_Ag/AgC+1

The chronoamperometric (I-t) curve refers to the potential applied to the working electrode as a linear function of time, an electrochemical method. The current response as a function of time is measured after a single potential step or a double potential step is applied to the working electrode of the electrochemical system, thereby studying the properties of the working electrode in a three-electrode system.

Linear sweep voltammetry parameters:

initial potential (volts): 0.23

Sampling interval (volts): 0.05

Experimental time (seconds): 200

Standing time (sec): 2

Sensitivity (ampere/volt): 0.001

As shown in FIG. 7, pure TiO₂Nanorod and UiO-67 coated TiO₂And comparing the photocurrent density of the nanorods. Pure TiO on FTO when light source is on₂The current density of (a) increased to 0.76 milliamps/square centimeter at 1.23 volts (relative to the reversible hydrogen electrode). In contrast, UiO-67 coated TiO on FTO₂The photocurrent density generated by the nanorods increased rapidly: at 1.23 volts (relative to the reversible hydrogen electrode), 2.3 milliamps/square centimeter was reached, which is pure TiO₂3 times of the nano-rod photocurrent density.

In addition, we have calculated the pure TiO produced₂Nanorod and UiO-67 coated TiO₂The solar energy conversion efficiency (η) of the nanorods, the conversion formula is:

η＝I(1.23-V)P_light

wherein V is an applied bias (relative to the reversible hydrogen electrode), I is a photocurrent density under the applied bias, and P_lightFor the incident light intensity (100 mw/cm), electrochemical linear sweep voltammetry was used for the test.

The results of the efficiency of solar energy conversion to hydrogen energy are shown in fig. 13. UiO-67 coated TiO₂The photoelectric conversion efficiency of the nanorods was about 0.08% at 1.23 volts (relative to the reversible hydrogen electrode), and about pure TiO₂4 times of the nano rod.

Using a three-electrode system, on pure TiO₂Nanorod and UiO-67 coated TiO₂And (4) measuring the Faraday efficiency of the nano rods for photoelectrocatalysis water decomposition. Photoelectrocatalytic decomposition of water at 1.50V (relative to standard hydrogen electrode) and collection of the gas produced during the first two hours (gas was taken every 20 minutes with a 1mL injection needle) to produce a gas yield-hour with theoretical and experimental valuesAnd (5) a middle graph.

Gas chromatography model GC 2060, shanghai sharps instruments ltd, experimental parameters:

column temperature: 40 deg.C

A detector: 120 deg.C

Sample injector: 110 deg.C

Pressing the column in front: 0.06MPa

Carrier gas flow 10mL/min

1mL sample introduction

FIG. 14 is a graph of the theoretical amount of gas at 1.50V (relative to a standard hydrogen electrode) versus the measured amount of gas over time. It can be seen from the figure that the actual gas production rate can be well matched with the theoretical value along with the change of time, which indicates that the Faraday efficiency in the process of photoelectrocatalysis water decomposition can almost reach 100%.

Claims

1. A preparation method of a core-shell structure of an ultrathin metal organic framework material UiO-67 coated titanium dioxide nanorod comprises the following steps:

1) pretreating a fluorine-doped tin oxide conductive glass substrate (hereinafter referred to as FTO substrate): cleaning the substrate by ultrasonic bath (ultrapure water, ethanol, acetone and ultrapure water) for 15 minutes in sequence, drying the FTO substrate for 30 minutes at 80 ℃ for later use,

2) preparation of hydrochloric acid solution: dissolving 6mL of concentrated hydrochloric acid in 6mL of deionized water, mixing, stirring for 5 minutes until the concentrated hydrochloric acid is uniformly mixed, wherein the concentration of the hydrochloric acid is 36-38%,

3) preparing a titanium dioxide precursor solution: adding 200 mu L of isobutyl titanate solution into the solution prepared in the step 2), stirring for 3 hours,

4) adding the titanium dioxide precursor solution prepared in the step 3) into a polytetrafluoroethylene lining of a 15 ml high-pressure reaction kettle, putting the FTO substrate pretreated in the step 1) into the inner lining, screwing a kettle cover down with the conductive surface, putting the reaction kettle into an electrothermal blowing dry box at 170 ℃, keeping the temperature for 10 hours,

5) taking out the reaction kettle, cooling to room temperature, taking out the FTO substrate full of white titanium dioxide, repeatedly washing with absolute ethyl alcohol and ultrapure water,

6) putting the FTO substrate prepared in the step 5) into a muffle furnace, raising the temperature of the muffle furnace to 450 ℃ at the heating rate of 3 ℃/min, keeping the temperature for 3 hours, then naturally cooling to room temperature, taking out the product to obtain the FTO substrate for growing rutile phase titanium dioxide nano rods,

7)ZrCl₄preparing a solution: 0.067 to 0.25 mmol of ZrCl₄Ultrasonically dispersing into 10mL of Dimethylformamide (DMF), or ethanol, or oleylamine,

8) preparing a precursor solution of a metal organic framework material UiO-67: 0.087 to 0.35 mmol of 4, 4-biphenyldicarboxylic acid was added to the solution of step 7), stirred for 30 minutes,

9) adding the UiO-67 precursor solution prepared in the step 8) into a polytetrafluoroethylene lining of a 15 ml high-pressure reaction kettle, putting the FTO substrate obtained in the step 6) into the FTO precursor solution, screwing a kettle cover down with the conductive surface facing downwards, putting the reaction kettle into an electrothermal blowing dry box at 120 ℃, keeping for 12-36 hours,

10) and (3) taking out the reaction kettle, cooling to a room temperature state, opening a cover to take out the FTO substrate, washing the substrate with DMF (dimethyl formamide) and absolute ethyl alcohol for three times respectively, and then placing the substrate in an oven at 50 ℃ for 1 hour to obtain a final product of the UiO-67 coated titanium dioxide nanorod.

2. The method according to claim 1, wherein step 7) ZrCl is used₄The molar amount of (c) is preferably 0.125 mmol.

3. The method according to claim 1, wherein the solvent in step 7) is preferably DMF.

4. The method according to claim 1, wherein the molar amount of the 4, 4-biphenyldicarboxylic acid (BPDC) in the step 8) is preferably 0.175 mmol.

5. The method of claim 1, wherein the oven heating time in step 9) is preferably 12 hours.

6. The method of claim 1, comprising the steps of:

1) pretreating the FTO substrate: cleaning the substrate by ultrasonic bath (ultrapure water, ethanol, acetone and ultrapure water) for 15 minutes in sequence, drying the FTO substrate in an oven at 80 ℃ for 30 minutes for later use,

2) preparation of hydrochloric acid solution: dissolving 6mL of concentrated hydrochloric acid in 6mL of deionized water, mixing, stirring for 5 minutes until the concentrated hydrochloric acid and the deionized water are uniformly mixed,

3) preparing a titanium dioxide precursor solution: 200. mu.L of an isobutyl titanate solution was added dropwise to the solution prepared in step 2), stirred for 3 hours,

4) adding 12 ml of the solution obtained in the step 3) into a polytetrafluoroethylene lining of a reaction kettle, immersing the pretreated FTO substrate into the solution, wherein the conductive surface is downward, screwing down a kettle cover, putting the reaction kettle into an electrothermal blowing dry box at 170 ℃, keeping the temperature for 10 hours,

5) taking out the reaction kettle, naturally cooling to room temperature, opening the reaction kettle cover, pouring off supernatant, taking out the FTO substrate, washing off surface precipitates by absolute ethyl alcohol and deionized water,

6) putting the FTO substrate obtained in the step 5) into a muffle furnace, keeping the temperature of the muffle furnace at 450 ℃ at the temperature of 3 ℃/min, naturally cooling to room temperature after keeping for 3 hours, taking out the product to obtain rutile phase titanium dioxide nano-rods,

7)ZrCl₄preparing a precursor solution: 0.125 mmol of ZrCl₄Ultrasonically dispersing the mixture into 10mL of DMF,

8) preparing a precursor solution of a metal organic framework material UiO-67: 0.175 mmol of 4, 4-biphenyldicarboxylic acid (BPDC) was added to the solution of step 7), stirred for 30 minutes,

9) adding the UiO-67 precursor solution prepared in the step 8) into a polytetrafluoroethylene lining of a 15 ml high-pressure reaction kettle, putting the FTO substrate treated in the step 6) into the reaction kettle, screwing a kettle cover down with the conductive surface facing downwards, putting the reaction kettle into an electrothermal blowing dry box at 120 ℃, keeping for 12 hours,

10) and (3) taking out the reaction kettle, cooling to a room temperature state, taking out the FTO substrate, washing the substrate with DMF (dimethyl formamide) and absolute ethyl alcohol for three times respectively, and then placing the substrate in a 50 ℃ oven for 1 hour to obtain the final FTO substrate, wherein the titanium dioxide nano-rods coated with the ultra-thin layer UiO-67 are grown on the FTO substrate.

7. An ultrathin UiO-67 coated titanium dioxide nanorod core-shell structure, which is characterized by being prepared by the preparation method of any one of claims 1 to 6.