阅读说明：本技术 一种基于二氧化钛改性材料的制备方法及其应用 (Preparation method and application of modified material based on titanium dioxide ) 是由 时鹏辉 严瑾 许吉宏 王鹏飞 陆可人 杨玲霞 范金辰 闵宇霖 徐群杰 于 2020-03-30 设计创作，主要内容包括：本发明属于材料技术领域,提供了一种基于二氧化钛改性材料的制备方法及其应用,首先将一定量的硼酸及氯化铑三水合物溶于含有硝酸、醇的水中得到A液；在0℃～4℃条件下,将钛酸异丙酯逐滴加入到乙醇溶液中得到B液；然后将A液缓慢滴加入B液中得到二氧化钛溶胶；再将二氧化钛溶胶在室温下进行老化,经过干燥得到干凝胶；最后将干凝胶研磨成粉末后在空气中煅烧4小时,得到硼铑共掺杂二氧化钛即基于二氧化钛改性材料。将该材料用于光催化产氢,催化产氢效率得到有效提升。本发明采用一锅溶胶凝胶法制备得到硼铑共掺杂二氧化钛,通过调整铑掺杂的比例能够调控二氧化钛的吸收带宽,提高光吸收和载流子分离的效率。(The invention belongs to the technical field of materials, and provides a preparation method and application of a titanium dioxide-based modified material, which comprises the steps of firstly dissolving a certain amount of boric acid and rhodium chloride trihydrate in water containing nitric acid and alcohol to obtain solution A; dropwise adding isopropyl titanate into an ethanol solution at the temperature of 0-4 ℃ to obtain a solution B; slowly dripping the solution A into the solution B to obtain titanium dioxide sol; then, the titanium dioxide sol is aged at room temperature and dried to obtain dry gel; and finally, grinding the dry gel into powder, and calcining the powder in the air for 4 hours to obtain the boron-rhodium co-doped titanium dioxide, namely the titanium dioxide-based modified material. The material is used for photocatalytic hydrogen production, and the catalytic hydrogen production efficiency is effectively improved. According to the invention, the boron-rhodium co-doped titanium dioxide is prepared by adopting a one-pot sol-gel method, the absorption bandwidth of the titanium dioxide can be regulated and controlled by adjusting the doping proportion of rhodium, and the light absorption and carrier separation efficiency is improved.)

1. The preparation method of the modified material based on titanium dioxide is characterized by comprising the following steps:

step 1, dissolving a certain amount of boric acid and rhodium chloride trihydrate into a mixed solution of alcohol and water containing a certain amount of nitric acid, and uniformly mixing to obtain a solution A;

step 2, dropwise adding isopropyl titanate into an ethanol solution at the temperature of 0-4 ℃ to obtain a solution B;

step 3, slowly dripping the solution A into the solution B, continuously stirring in the dripping process, and continuously stirring for a period of time after the dripping is finished to obtain titanium dioxide sol;

step 4, aging the titanium dioxide sol at room temperature, and drying to obtain xerogel;

and 5, grinding the xerogel into powder, and calcining the powder in air for 4 hours to obtain the modified material based on titanium dioxide.

2. The method for preparing the titanium dioxide-based modified material according to claim 1, wherein:

wherein in step 1, the molar ratio of the boric acid to the rhodium chloride trihydrate is 50: 1-5: 1.

3. The method for preparing the titanium dioxide-based modified material according to claim 1, wherein:

wherein the molar ratio of the boric acid to the isopropyl titanate is 5: 1-20: 1.

4. The method for preparing the titanium dioxide-based modified material according to claim 1, wherein:

wherein in step 1, the molar ratio of the nitric acid, the alcohol and the water is 0.1: 1: 1-0.1: 4:1, wherein the alcohol is methanol or ethanol.

5. The method for preparing the titanium dioxide-based modified material according to claim 1, wherein:

wherein, the step 3 is carried out at the temperature of 0-4 ℃.

6. The method for preparing the titanium dioxide-based modified material according to claim 1, wherein:

wherein, in the step 5, the calcining temperature is 400-800 ℃.

7. The method for preparing the titanium dioxide-based modified material according to claim 1, wherein:

wherein in the step 4, the titanium dioxide sol is aged for 12-24 hours at room temperature.

8. The method for preparing the titanium dioxide-based modified material according to claim 1, wherein:

wherein in the step 3, the stirring is continued for 2 to 4 hours after the dropwise addition is finished.

9. The application of the titanium dioxide-based modified material in photocatalytic water splitting hydrogen production is characterized in that the titanium dioxide-based modified material is prepared by the preparation method of the titanium dioxide-based modified material according to any one of claims 1 to 8.

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a preparation method and application of a titanium dioxide-based modified material.

Background

Over the past few decades, the global energy crisis has become more severe and nonrenewable fossil fuel energy sources have resulted in irreversible pollution of the environment. Therefore, development of new clean energy has been proposed. Solar energy is becoming increasingly important as a new clean energy source due to its low cost and renewable nature. The conversion of solar energy into clean chemical fuels has become a recent research hotspot. The traditional photocatalytic water splitting hydrogen production performance is limited by the following three factors: 1) a solar absorption band; 2) carrier separation efficiency and diffusion rate; 3) interfacial reaction and mass transfer rates. It is highly desirable to radically improve the performance of photocatalysts, such as broadening the absorption band of the catalyst, reducing the rate of carrier recombination and increasing the photo-generated charge transport. Oxygen vacancy (V) on semiconductor photocatalysts_O) Defects can effectively improve carrier separation and shorten the distance of carrier migration to the surface. The titanium dioxide has the characteristics of low price, no toxicity and chemical stability, and the wide band gap of the titanium dioxide provides a proper reaction potential for the photocatalytic hydrogen production reaction. But also has the disadvantages of slow charge transfer kinetics and limited light absorption range.

Disclosure of Invention

The invention is made to solve the above problems, and aims to provide a preparation method and application of a modified material based on titanium dioxide, which effectively overcome the defects of titanium dioxide, improve the redox kinetics of titanium dioxide and expand the visible light absorption range of titanium dioxide by co-doping metal ions and non-metal ions.

The invention provides a preparation method of a modified material based on titanium dioxide, which is characterized by comprising the following steps: step 1, dissolving a certain amount of boric acid and rhodium chloride trihydrate into a mixed solution of alcohol and water containing a certain amount of nitric acid, and uniformly mixing to obtain a solution A; step 2, dropwise adding isopropyl titanate into an ethanol solution at the temperature of 0-4 ℃ to obtain a solution B; step 3, slowly dripping the solution A into the solution B, continuously stirring in the dripping process, and continuously stirring for a period of time after the dripping is finished to obtain titanium dioxide sol; step 4, aging the titanium dioxide sol at room temperature, and drying to obtain xerogel; and 5, grinding the dry gel into powder, and calcining the powder in the air for 4 hours to obtain the modified material based on the titanium dioxide.

In the preparation method of the titanium dioxide modified material, the preparation method can also have the following characteristics: wherein in the step 1, the molar ratio of boric acid to rhodium chloride trihydrate is 50: 1-5: 1.

In the preparation method of the titanium dioxide modified material, the preparation method can also have the following characteristics: wherein the molar ratio of boric acid to isopropyl titanate is 5: 1-20: 1.

In the preparation method of the titanium dioxide modified material, the preparation method can also have the following characteristics: wherein, in the step 1, the molar ratio of the nitric acid to the alcohol to the water is 0.1: 1: 1-0.1: 4:1, wherein the alcohol is methanol or ethanol.

In the preparation method of the titanium dioxide modified material, the preparation method can also have the following characteristics: wherein, the step 3 is carried out at the temperature of 0-4 ℃.

In the preparation method of the titanium dioxide modified material, the preparation method can also have the following characteristics: wherein, in the step 5, the calcining temperature is 400-800 ℃.

In the preparation method of the titanium dioxide modified material, the preparation method can also have the following characteristics: wherein in the step 4, the aging time of the titanium dioxide sol is 12-24 h.

In the preparation method of the titanium dioxide modified material, the preparation method can also have the following characteristics: wherein in the step 3, the stirring is continued for 2 to 4 hours after the dropwise addition is finished.

The invention also provides an application of the titanium dioxide-based modified material in hydrogen production by photocatalytic water decomposition, which is characterized in that the titanium dioxide-based modified material is prepared by a preparation method based on the titanium dioxide-based modified material.

Action and Effect of the invention

The invention provides a preparation method based on a titanium dioxide modified material, which comprises the following steps of firstly, slowly dropwise adding isopropyl titanate into an ethanol solution under the condition of vigorous stirring at 0-4 ℃, and hydrolyzing part of the isopropyl titanate to obtain a semitransparent suspension solution, namely a solution B; then slowly dripping the doped element precursor solution (solution A) into solution B under stirring at the temperature of 0-4 ℃, gradually changing the solution B from semitransparent turbid liquid into uniform semitransparent sol solution under the acidic environment provided by boric acid and nitric acid, and further slowly hydrolyzing isopropyl titanate in the process to obtain Ti (OH)₄Polymerizing into micro micelle, and dispersing uniformly to form titanium dioxide sol. In the above operation process, the ambient temperature is always maintained at about 0-4 ℃. The doping element is uniformly inserted into Ti (OH) during the reaction₄In the structure, the co-doped titania sol solution was obtained. The sol was then evaporated at room temperature to form spherical small particles. And finally, annealing the spherical small particles at high temperature to obtain the porous nano boron-rhodium co-doped titanium dioxide, namely the titanium dioxide-based modified material. The material is used for photocatalytic hydrogen production, and the catalytic hydrogen production efficiency is effectively improved.

According to the invention, the boron-rhodium co-doped titanium dioxide is prepared by adopting a one-pot sol-gel method, boron doping enables the titanium dioxide to generate oxygen vacancies with two electrons, rhodium promotes the concentration of the oxygen vacancies to be improved, the energy required by electron transition is reduced due to the generation of defects, and the light absorption range of the titanium dioxide is widened, so that the photocatalytic hydrogen production efficiency of the titanium dioxide is effectively improved. Meanwhile, the absorption bandwidth of titanium dioxide can be regulated and controlled by adjusting the doping proportion of rhodium, and the light absorption and carrier separation efficiency is improved.

Drawings

FIG. 1 is a schematic scanning electron microscope of a titania-based modified material in example 1 of the present invention;

FIG. 2 is a schematic transmission electron microscope of a titania-based modified material in example 1 of the present invention;

FIG. 3 shows modified materials based on titanium dioxide and TiO in examples 1 and 3 and comparative example 2 of the present invention₂(ii) a Raman map of (a);

FIG. 4 is a graph showing diffuse reflectance of ultraviolet light based on a titanium dioxide-modified material in examples 1 to 3 of the present invention;

FIG. 5 is an electron paramagnetic diagram of the titania-based modified material in examples 2 and 4 of the present invention;

FIG. 6 is a graph of transient photocurrent of a modified FTO electrode in test example 2 of the present invention;

FIG. 7 is a graph showing the comparison of hydrogen amounts in photocatalytic decomposition water in application examples 1 to 4 of the present invention.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the preparation method and the application of the titanium dioxide-based modified material of the invention are specifically described below with reference to the embodiment and the accompanying drawings.

Unless otherwise specified, each raw material used in the following examples is a commercially available product, and each apparatus used is a commercially available conventional apparatus.

The invention provides a preparation method of a modified material based on titanium dioxide, which comprises the following steps:

step 1, dissolving a certain amount of boric acid and rhodium chloride trihydrate into a mixed solution of alcohol and water containing a certain amount of nitric acid, and uniformly mixing to obtain solution A. Wherein the molar ratio of boric acid to rhodium chloride trihydrate is 50: 1-5: 1, wherein the molar ratio of nitric acid to alcohol to water is 0.1: 1: 1-0.1: 4:1, wherein the alcohol can be methanol or ethanol. In the embodiment of the invention, ethanol is adopted, and in practical application, methanol can achieve the same technical effect as ethanol.

And 2, dropwise adding isopropyl titanate into the ethanol solution in a dry environment at the temperature of 0-4 ℃ to obtain solution B. Wherein the molar ratio of boric acid to isopropyl titanate is 5: 1-20: 1, and the reaction temperature is controlled to be 0-4 ℃. In this step, the isopropyl titanate is partially hydrolyzed, i.e., the system is slightly cloudy during the addition, but no white precipitate appears.

And 3, slowly dropwise adding the solution A into the solution B, continuously stirring in the dropwise adding process, and continuously stirring for 2-4 h after dropwise adding is finished to obtain the titanium dioxide sol.

And 4, aging the titanium dioxide sol at room temperature for 12-24 h, and drying to obtain xerogel.

And 5, grinding the dry gel into powder, and calcining the powder in the air at 400-800 ℃ for 4 hours to obtain the modified material based on the titanium dioxide.

The prepared modified material based on titanium dioxide is used for photocatalytic decomposition of water, and the specific operation is as follows: first, the material was fed to a reactor for photocatalytic decomposition water containing 10ml of an aqueous solution of methanol (methanol: water: 1: 9). The reactor was sealed and then vented with high purity argon for about 30min to completely remove the residual air from the reactor. Then, the photocatalytic decomposition reaction of water to produce hydrogen is started. The reactor was placed under a 300W xenon lamp equipped with an AM1.5G filter to simulate sunlight. Sampling is carried out once every hour, the content of the hydrogen generated in the reactor is detected by a gas chromatograph, and the photocatalytic performance of each sample is recorded and evaluated.

< example 1>

In this example, a titanium dioxide-based modified material is prepared, and the molar ratio of isopropyl titanate, boric acid and rhodium chloride trihydrate is selected from 500: 50: 1, the specific operation is as follows:

step 1, dissolving boric acid and rhodium chloride trihydrate into a mixed solution of ethanol and water containing a certain amount of nitric acid (the molar ratio of the nitric acid to the ethanol to the water is 0.1: 1: 1), and uniformly mixing to obtain a solution A.

And 2, dropwise adding isopropyl titanate into the ethanol solution in a dry environment at the temperature of 0-4 ℃ to obtain solution B. Controlling the reaction temperature to be 0-4 ℃. In the step, the isopropyl titanate is partially hydrolyzed, namely the system is slightly turbid in the dropping process, but no obvious white precipitate appears, and the finally obtained solution B is a semitransparent suspension.

And 3, slowly dropwise adding the solution A into the solution B, continuously and quickly stirring in the dropwise adding process, and continuously stirring for 2 hours after dropwise adding is finished to obtain the titanium dioxide sol.

And 4, aging the titanium dioxide sol for 24 hours at room temperature, and then drying in a vacuum oven to obtain xerogel.

And 5, fully grinding the xerogel in a mortar, and calcining the obtained powder in air at 500 ℃ for 4 hours to obtain a modified material based on titanium dioxide, wherein the mark is as follows: rh_0.1/B-TiO₂。

< example 2>

In this example, a titanium dioxide-based modified material is prepared, and the molar ratio of isopropyl titanate, boric acid and rhodium chloride trihydrate is selected from 500: 50: 5, the specific operation is as follows:

step 1, dissolving boric acid and rhodium chloride trihydrate into a mixed solution of ethanol and water containing a certain amount of nitric acid (the molar ratio of the nitric acid to the ethanol to the water is 0.1: 2: 1), and uniformly mixing to obtain a solution A.

And 2, dropwise adding isopropyl titanate into the ethanol solution in a dry environment at the temperature of 0-4 ℃ to obtain solution B. Controlling the reaction temperature to be 0-4 ℃. In the step, the isopropyl titanate is partially hydrolyzed, namely the system is slightly turbid in the dropping process, but no obvious white precipitate appears, and the finally obtained solution B is a semitransparent suspension.

And 3, slowly dropwise adding the solution A into the solution B, continuously and quickly stirring in the dropwise adding process, and continuously stirring for 4 hours after dropwise adding is finished to obtain the titanium dioxide sol.

And 4, aging the titanium dioxide sol for 24 hours at room temperature, and then drying in a vacuum oven to obtain xerogel.

And 5, fully grinding the xerogel in a mortar, and calcining the obtained powder in air at 500 ℃ for 4 hours to obtain a modified material based on titanium dioxide, wherein the mark is as follows: rh_0.5/B-TiO₂。

< example 3>

In this embodiment, a titanium dioxide modified material is prepared, and the molar ratio of isopropyl titanate, boric acid and rhodium chloride trihydrate is selected from 500: 50: the remaining operations were the same as in example 2 to obtain a titanium dioxide-modified material, which was labeled as: rh₁/B-TiO₂。

< comparative example 1>

In this example, a titanium dioxide modified material control sample is prepared, boric acid is not added, and the molar ratio of isopropyl titanate to rhodium chloride trihydrate is selected from 500: the remaining operations are the same as in example 2, obtaining a modified material based on titanium dioxide, marked: Rh-TiO₂。

< comparative example 2>

In this example, a titanium dioxide modified material control sample is prepared without adding rhodium chloride trihydrate, and the molar ratio of isopropyl titanate to boric acid is 500: 50, the remaining operations are the same as in example 2, obtaining a modified material based on titanium dioxide, marked: B-TiO₂。

< test example >

Scanning electron microscope detection and transmission electron microscope detection are carried out on the titanium dioxide-based modified material prepared in example 1, and the detection results are shown in fig. 1 and fig. 2.

Fig. 1 is a schematic scanning electron microscope of a titania-based modified material in example 1 of the present invention, and fig. 2 is a schematic transmission electron microscope of a titania-based modified material in example 1 of the present invention.

As shown in fig. 1, it is apparent that the prepared catalyst material is spherical particles having a particle diameter of about 100nm and has a uniform particle size. The transmission electron microscope in fig. 2 shows clear lattice stripes, and the measurement shows that the lattice spacing corresponds to the crystal plane 101 and the crystal plane 103 of the titanium dioxide respectively, and the crystal lattice conforms to the typical anatase titanium dioxide, so that the prepared material is confirmed to be the titanium dioxide material.

Modified materials based on titanium dioxide and TiO prepared in examples 1 and 3 and comparative example 2₂Raman detection was performed, and the detection results are shown in FIG. 3. Wherein, TiO₂Commercially available analytically pure titanium dioxide, type P25(Aladdin, AR).

FIG. 3 shows modified materials based on titanium dioxide and TiO in examples 1 and 3 and comparative example 2 of the present invention₂Raman map of (a).

FIG. 3 shows titanium dioxide at 100cm^-1To 800cm^-1Raman spectra within the range. Wherein is located at 135cm^-1、382cm^-1、506cm^-1And 629cm^-1The four-position raman peak can be defined as the anatase titania band. As is evident from FIG. 3, the rhodium-doped material exhibited a weaker Raman peak and was positively shifted by 3cm relative to the pure titanium dioxide and boron-doped materials^-1And shows obvious defect characteristics. This phenomenon demonstrates that the separation and migration of carriers are increased inside the material, thereby improving the photocatalytic activity.

Modified materials based on titanium dioxide prepared in examples 1 to 3 and TiO₂Ultraviolet diffuse reflection detection is carried out, and the detection result is shown in figure 4. Wherein, TiO₂Is commercially available pure titanium dioxide, model P25(Aladdin, AR).

FIG. 4 is a graph showing the diffuse reflection of ultraviolet light of titanium dioxide-based modified materials prepared in examples 1 to 3 of the present invention.

As shown in FIG. 4, pure TiO was measured by UV-Vis diffuse reflectance spectroscopy₂Has a narrow light absorption band with an edge of about 387nm, and Rhx/B-TiO₂The absorption range of (A) is significantly increased, and a slight enhancement in the visible light region is observed. When the doping amount of Rh was increased to 0.5% (i.e., x ═ 0.5), two absorption peaks occurred at 430nm and 540nm, respectively, in the visible light region of 400nm to 600 nm. The absorption at 430nm can be attributed to the electron excitation from the impurity level to the conduction band, while 540nm is attributed to the electron transition from the valence band to the impurity level. Rhx/B-TiO₂Showing the presence of two absorption edges indicating a local state between the conduction band and the valence band. Enhanced absorption can be attributed toDue to the synergistic effect of boron and rhodium, the doping of boron and rhodium can indeed widen the absorption band of the material, shift towards the visible light direction, and improve the utilization efficiency of sunlight.

The titania-based modified materials prepared in example 2 and comparative example 2 were subjected to the examination of oxygen vacancies, and the examination results are shown in FIG. 5.

FIG. 5 is an Electron Paramagnetic (EPR) diagram of titania-based modified materials prepared in example 2 of the present invention and comparative example 2.

As shown in fig. 5, the EPR spectrogram can visually represent oxygen vacancy defects, and the oxygen vacancy concentrations of the boron mono-doped titanium dioxide and the boron rhodium co-doped titanium dioxide obtained according to the change of the peak intensity are obviously changed, wherein the boron rhodium co-doped titanium dioxide enables the defect concentration to be improved.

< test example 2>

Preparation of modified FTO (fluorine-doped SnO) by the application example₂Transparent conductive glass) electrode, and modifying materials of P25 and Rhx/B-TiO₂(x ═ 0, 0.1, 0.5, and 1) as samples, the specific experimental procedures were as follows:

adding 1ml of α -terpineol and 1mg of ethylcellulose to the sample, then adding 0.5 ml of ethanol, stirring until the liquid becomes a homogeneous suspension, finally, applying a certain amount of the suspension on the conductive surface of a clean FTO glass having an area of about 1cm × 1cm, and then drying in an oven for 2h to obtain a film of uniform thickness, performing photoelectrochemical measurements using a CHI660E electrochemical workstation in a standard three-electrode system using synthetic material modified FTO, Ag/AgCl electrodes, Pt wire as working electrode, counter electrode and reference electrode, respectively, 0.5M Na₂SO₄The transient photocurrent response was measured in the electrolyte. As shown in fig. 6.

As can be seen from FIG. 6, this control has a certain effect on photocurrent response, in which the current density is maximized when the doping amount is 5 wt%, and Rh is obtained_0.5/B-TiO₂The photo-generated electron separation efficiency is the best.

< application example 1>

The materials obtained in the above embodiments are used in the present application example to evaluate the photocatalytic hydrogen production performance, and the specific experimental process is as follows:

the material was added to a photocatalytic decomposition water hydrogenation reactor containing 10ml of aqueous methanol (methanol: water: 1: 9). The reactor was sealed and then vented with high purity argon for about 30min to completely remove the residual air from the reactor. Then the photocatalytic decomposition water hydrogen production reaction is started. The reactor was placed under a 300W xenon lamp equipped with an AM1.5G filter to simulate sunlight. Sampling is carried out once every hour, the content of the hydrogen generated in the reactor is detected by a gas chromatograph, and the photocatalytic performance of each sample is recorded and evaluated. The test results are shown in fig. 7.

As can be seen from FIG. 7, it was found that Rh prepared in example 2 was produced by comparing the photocatalytic hydrogen production amounts of the materials having different Rh doping amounts_0.5/B-TiO₂Has the largest hydrogen production amount, and the average hydrogen production amount per hour is 17.6mmol g^-1·h^-1The material is proved to have the best photocatalytic performance, which shows that the control has a certain effect on the photocatalytic hydrogen production performance, and further the best ion doping amount is obtained as Rh_0.5/B-TiO₂。

Referring to fig. 5, it can be seen that doping with boron and rhodium causes different levels of defects, and that further doping with rhodium further increases the oxygen vacancy concentration of the boron-single-doped material. In conjunction with the transient photocurrent of FIG. 6, Rh can be derived_0.5/B-TiO₂The photocurrent response is best and the current density is maximum. This result corresponds to the amount of hydrogen produced by photocatalytic decomposition of the material, and it can be seen from fig. 7 that the efficiency of hydrogen production by photocatalytic decomposition of the co-doped titanium dioxide material is higher and the performance is best at a rhodium doping amount of 5 wt%.