阅读说明：本技术 还原态Si掺杂二氧化钛纳米管光阳极及其制备方法 (Reduced Si-doped titanium dioxide nanotube photoanode and preparation method thereof ) 是由 董振标 蔡义强 于 2020-11-30 设计创作，主要内容包括：本发明公开了一种还原态Si掺杂二氧化钛纳米管光阳极及其的制备方法,该制备方法为Ti-Si合金经过阳极氧化法以及热处理退火得到晶态化Si掺杂二氧化钛纳米管,然后再通过电化学还原方法得到还原态Si掺杂二氧化钛纳米管光阳极；其中,得到的还原态Si掺杂二氧化钛纳米管光阳极为Si和Ti~(3+)/氧空位共掺杂的二氧化钛纳米管。本发明获得的Si和Ti~(3+)/氧空位共掺杂的二氧化钛纳米管作为电极稳定性好、光电催化性能高、具有可见光光催化活性,且制备过程中原料无毒、制备条件便捷可控。(The invention discloses a reduced Si-doped titanium dioxide nanotube photoanode and a preparation method thereof, wherein the preparation method comprises the steps of obtaining a crystallized Si-doped titanium dioxide nanotube by performing anodic oxidation and thermal treatment annealing on Ti-Si alloy, and then obtaining the reduced Si-doped titanium dioxide nanotube photoanode by an electrochemical reduction method; wherein the photo-anode of the obtained reduced Si-doped titanium dioxide nanotube is Si and Ti 3+ And/or oxygen vacancy co-doped titanium dioxide nanotubes. Si and Ti obtained by the present invention 3+ The/oxygen vacancy codoped titanium dioxide nanotube has good stability as an electrode, high photoelectrocatalysis performance and visible light photocatalysis activity, and the raw materials are nontoxic in the preparation process,The preparation conditions are convenient and controllable.)

1. A preparation method of a reduction state Si doped titanium dioxide nanotube photo-anode is characterized in that a Ti-Si alloy is subjected to anodic oxidation and thermal treatment annealing to obtain a crystallized Si doped titanium dioxide nanotube, and then is subjected to electrochemical reduction to obtain a reduction state Si doped titanium dioxide nanotube photo-anode;

wherein the obtained reduced Si-doped titanium dioxide nanotube lightThe anode is Si and Ti³⁺And/or oxygen vacancy co-doped titanium dioxide nanotubes.

2. The method for preparing the reduced Si-doped titanium dioxide nanotube photoanode according to claim 1, wherein the electrochemical reduction method comprises: in the range of 0.4-0.6M Na₂SO₄Electrochemically reducing the crystallized Si-doped titanium dioxide nanotubes in the solution at a reduction voltage of 3-5V for 5-20 min.

3. The method for preparing the reduced Si-doped titanium dioxide nanotube photoanode according to claim 1, wherein the anodic oxidation method comprises: placing Ti-Si alloy in 0.4 wt.% NH₄F and 2 vol.% H₂In the electrolytic bath of the ethylene glycol mixed solution of O, the anodic oxidation pulse voltage is 30V, and the anodic oxidation time is 1 h.

4. The method for preparing the reduced Si-doped titanium dioxide nanotube photoanode according to claim 1 or 3, wherein the Ti-Si alloy is prepared by vacuum arc melting.

5. The method for preparing the reduced Si-doped titanium dioxide nanotube photoanode according to claim 1, wherein the heat treatment annealing specifically comprises: heating the anode oxidized Ti-Si alloy in a heating furnace to 500 ℃, then preserving heat for 2h, and then cooling in the furnace.

6. A reduced Si-doped titanium dioxide nanotube photoanode prepared by the method of preparing the reduced Si-doped titanium dioxide nanotube photoanode according to any one of claims 1 to 5, wherein the reduced Si-doped titanium dioxide nanotube photoanode is Si and Ti³⁺And/or oxygen vacancy co-doped titanium dioxide nanotubes.

Technical Field

The invention belongs to the field of titanium dioxide nanotube photoelectrocatalysis, and particularly relates to a reduction-state Si-doped titanium dioxide nanotube photoanode and a preparation method thereof.

Background

The hydrogen energy is used as clean, efficient and pollution-free energy and plays an important role in the development and progress of the human society. Nowadays, the hydrogen production mode still takes fossil energy as the main energy, and the hydrogen production mode does not meet the requirements of the current sustainable development concept. In 1972, Japanese scientists Fujisima and Honda discovered that water could be decomposed to generate hydrogen gas under light conditions using a single-crystal titanium oxide semiconductor as an electrode. Meanwhile, titanium oxide has the characteristics of low price, no toxicity, stable chemical property, energy band structure matched with the redox potential of water and the like, and has attracted extensive attention of scientific researchers. However, the main problems of titanium oxide in the photolysis of water for hydrogen production are: (1) the forbidden band width is large, and only partial energy of sunlight ultraviolet light can be absorbed, the energy only accounts for 5% of the full-spectrum energy of the sun, and the utilization rate of the sunlight is low. (2) The photoproduction electron-hole pair is easy to recombine in the separation process, and the quantum yield is low. The efficiency of hydrogen production by photolysis of water is low due to the comprehensive factors.

The design and element doping of the one-dimensional titanium oxide nanotube are effective ways for improving the hydrogen production characteristic of photolysis of water. The one-dimensional titanium oxide nanotube has a higher specific surface area, which is beneficial to enlarging the light absorption area. Meanwhile, the separation of photo-generated electron-hole pairs is promoted to a certain extent, the directional transmission characteristic of photoelectrons is improved, and the service life of carriers is further prolonged. In addition, Si element is one of ideal doping elements because of the abundant content and low price in the earth crust. Experiments and theoretical calculation researches show that the valence band width of titanium oxide can be obviously widened by doping Si, so that separation and transmission of photo-generated electron-hole pairs are facilitated, and the hydrogen production characteristic by photolysis of water is improved. In recent years, researchers have found that Ti³⁺Oxygen vacancy autodoping is also an important method for improving the photocatalytic characteristics of titanium oxide. Optically speaking, Ti³⁺The oxygen vacancy self-doping can introduce impurity energy level at the tail of a conduction band, effectively reduce band gap and promote visible light absorption; from the electrochemical perspective, the introduced oxygen vacancy can be used as an electron shallow potential capture well to effectively inhibit the recombination of a photo-generated electron-hole pair, so that the density of a photo-generated carrier is improved. To date, researchers have predominantly passed through H₂Reduction, NaBH₄And N₂H₄Introducing Ti into the nano titanium oxide by methods such as chemical reduction of reducing agent, metal reduction, hydrogen plasma, high-energy particle bombardment and the like³⁺Oxygen vacancies to improve its photocatalytic properties. However, the above methods have problems, respectively: h₂The reduction requires high temperature condition and consumes more hydrogenThe total coefficient is low; the stability of a chemical reducing agent reduction system is poor; the metal reduction needs to be carried out in a high-temperature low-oxygen environment for a long time; the hydrogen plasma and high energy particle bombardment require special instrumentation and are relatively costly.

Disclosure of Invention

The invention aims to solve the technical problem of providing a reduction state Si-doped titanium dioxide nanotube photo-anode and a preparation method thereof, and Si and Ti obtained by the photo-anode³⁺The/oxygen vacancy co-doped titanium dioxide nanotube has good stability as an electrode, high photoelectrocatalysis performance and visible light photocatalysis activity, and the raw materials are nontoxic in the preparation process, and the preparation conditions are convenient and controllable.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a preparation method of a reduction state Si doped titanium dioxide nanotube photo-anode comprises the steps of carrying out anodic oxidation and heat treatment annealing on Ti-Si alloy to obtain a crystallized Si doped titanium dioxide nanotube, and then carrying out electrochemical reduction to obtain a reduction state Si doped titanium dioxide nanotube photo-anode;

wherein the photo-anode of the obtained reduced Si-doped titanium dioxide nanotube is Si and Ti³⁺And/or oxygen vacancy co-doped titanium dioxide nanotubes.

Specifically, the electrochemical reduction method specifically comprises the following steps: in the range of 0.4-0.6M Na₂SO₄Electrochemically reducing the crystallized Si-doped titanium dioxide nanotubes in the solution at a reduction voltage of 3-5V for 5-20 min.

Specifically, the anodic oxidation method specifically comprises: placing Ti-Si alloy in 0.4 wt.% NH₄F and 2 vol.% H₂In the electrolytic bath of the ethylene glycol mixed solution of O, the anodic oxidation pulse voltage is 30V, and the anodic oxidation time is 1 h.

Preferably, the Ti-Si alloy is produced by vacuum arc melting.

Specifically, the heat treatment annealing specifically comprises: heating the anode oxidized Ti-Si alloy in a heating furnace to 500 ℃, then preserving heat for 2h, and then cooling in the furnace.

The invention also provides a reduced Si doping method according to the aboveThe reduction state Si doped titanium dioxide nanotube photo-anode prepared by the preparation method of the hetero titanium dioxide nanotube photo-anode is Si and Ti³⁺And/or oxygen vacancy co-doped titanium dioxide nanotubes.

Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects:

si and Ti provided by the invention³⁺The/oxygen vacancy co-doped titanium dioxide nanotube can better exert Si and Ti³⁺The synergistic advantage of oxygen vacancy and the advantage of large specific surface area of the one-dimensional titanium dioxide nanotube effectively improve the light absorption characteristic and the separation and transmission efficiency of the photo-generated electron-hole pair. In the preparation process, Ti-Si alloy is oxidized by anode, then heat treatment annealing is carried out to obtain crystalline Si doped titanium dioxide nano-tube, and Si and Ti can be obtained by electrochemical reduction³⁺/oxygen vacancy co-doped titanium dioxide nanotubes. Thus obtaining Ti³⁺Compared with the existing preparation method, the oxygen vacancy is simple, the preparation process is safe, simple and feasible, the operation is controllable, and the prepared photo-anode has better stability and good photoelectrocatalysis performance. The material is an environment-friendly photo-anode material with visible light photoelectrocatalysis performance, which is cheap, pollution-free and easy for industrial application.

Drawings

FIG. 1 is a surface topography of a crystalline Si-doped titanium dioxide nanotube of example 2 of the present invention;

FIG. 2 is a surface topography of electrochemically reduced crystalline Si-doped titanium dioxide nanotubes of example 2;

FIG. 3 is an energy spectrum and corresponding chemical composition of the crystalline Si-doped titanium dioxide nanotube of example 2 of the present invention;

FIG. 4 is an energy spectrum and corresponding chemical compositions of the crystalline Si-doped titanium dioxide nanotubes electrochemically reduced in example 2 of the present invention;

FIG. 5 is XPS spectra of Si-doped titanium dioxide nanotubes in example 2 of the present invention in a reduced state and Si 2p spectra of Si-doped titanium dioxide nanotubes in comparative example 2;

FIG. 6 is an XPS spectrum of O1s spectra for Si-doped titanium dioxide nanotubes in the reduced state of example 2, undoped titanium dioxide nanotubes of comparative example 1, Si-doped titanium dioxide nanotubes of comparative example 2, and reduced silicon dioxide nanotubes of comparative example 3 in accordance with the present invention;

FIG. 7 is UV-visible diffuse reflectance absorption spectra of Si-doped titanium dioxide nanotubes of example 2, undoped titanium dioxide nanotubes of comparative example 1, and Si-doped titanium dioxide nanotubes of comparative example 2 in accordance with the present invention;

fig. 8 is a photocurrent stability test of the photo-anode of the reduced Si-doped titanium dioxide nanotube of example 2 of the present invention.

Detailed Description

The invention provides a reduced Si-doped titanium dioxide nanotube photoanode and a preparation method thereof, which are further described in detail with reference to the accompanying drawings and specific examples. The advantages and features of the present invention will become more apparent from the following description.

The invention provides a preparation method of a reduction state Si doped titanium dioxide nanotube photo-anode, wherein a Ti-Si alloy is subjected to anodic oxidation and heat treatment annealing to obtain a crystallized Si doped titanium dioxide nanotube, and then is subjected to electrochemical reduction to obtain a reduction state Si doped titanium dioxide nanotube photo-anode;

specifically, the anodic oxidation method specifically comprises: placing Ti-Si alloy in 0.4 wt.% NH₄F and 2 vol.% H₂In an electrolytic bath of the ethylene glycol mixed solution of O, the anodic oxidation pulse voltage is 30V, and the anodic oxidation time is 1 h; then putting the mixture into a heating furnace, heating the mixture to 500 ℃ along with the furnace, preserving the heat for 2 hours, and cooling the mixture along with the furnace;

and finally, electrochemical reduction: in the range of 0.4-0.6M Na₂SO₄Electrochemically reducing the crystallized Si-doped titanium dioxide nanotubes in the solution at a reduction voltage of 3-5V for 5-20 min.

Wherein the photo-anode of the obtained reduced Si-doped titanium dioxide nanotube is Si and Ti³⁺And/or oxygen vacancy co-doped titanium dioxide nanotubes.

Preferably, the Ti-Si alloy is produced by vacuum arc melting.

Example 1

Sequentially grinding and polishing Ti-Si alloy sheets with the size of 10mm multiplied by 20mm multiplied by 1mm by using 400#, 800# and 1500# alumina water sand paper, and sequentially soaking and ultrasonically cleaning for 5 minutes by using acetone, absolute ethyl alcohol and deionized water; 0.4 wt.% NH in the electrolyte₄F and 2 vol.% H₂In an electrolytic bath of ethylene glycol mixed solution of O, the temperature is 25 ℃, the anodic oxidation pulse voltage is 30V, the anodic oxidation time is 1 hour, and Si-doped titanium dioxide nanotubes grow on the surface of the Ti-Si alloy sheet. Washing Si-doped titanium oxide nanotube with deionized water for 5min to remove organic impurities on the surface, and then washing with N₂Drying by air flow; then heat-treating at 500 deg.C for 2 hr, cooling with furnace to obtain crystallized Si-doped titanium dioxide nanotube photoanode (crystallized Ti-Si-O nanotube photoanode); then put in 0.5M Na₂SO₄In the solution, Si and Ti are obtained under the conditions of reduction voltage of 4V and reduction time of 5min³⁺The/oxygen vacancy codoped reduction state titanium dioxide nanotube photo-anode. The crystal structure is anatase crystal structure, and the photocurrent density is 1.44mA/cm²。

Example 2

The same anodization and heat treatment process as in example 1 was used, followed by 0.5M Na₂SO₄In the solution, Si and Ti are obtained under the conditions of reduction voltage of 4V and reduction time of 10min³⁺The photo-anode of the/oxygen vacancy co-doped reduction state Ti-Si-O nanotube has the photo-current density of 1.61mA/cm²。

Example 3

The same anodization and heat treatment process as in example 1 was used, followed by 0.5M Na₂SO₄In the solution, Si and Ti are obtained under the conditions of reduction voltage of 4V and reduction time of 20min³⁺The photo-anode of the/oxygen vacancy co-doped reduction state Ti-Si-O nanotube has the photo-current density of 1.37mA/cm²。

Example 4

The same anodization and heat treatment process as in example 1 was used, followed by 0.5M Na₂SO₄In the solution, under the conditions of 3V of reduction voltage and 10min of reduction time,to obtain Si and Ti³⁺The photo-anode of the/oxygen vacancy co-doped reduction state Ti-Si-O nanotube has the photo-current density of 1.21mA/cm²。

Example 5

The same anodization and heat treatment process as in example 1 was used, followed by 0.5M Na₂SO₄In the solution, Si and Ti are obtained under the conditions that the reduction voltage is 5V and the reduction time is 10min³⁺The photo-anode of the/oxygen vacancy co-doped reduction state Ti-Si-O nanotube has the photo-current density of 1.15mA/cm²。

Comparative example 1

After a pure titanium sheet with the size of 10mm multiplied by 20mm multiplied by 1mm is sequentially polished by 400#, 800# and 1500# alumina water sand paper, acetone, absolute ethyl alcohol and deionized water are sequentially used for soaking and ultrasonic cleaning for 5 minutes; 0.4 wt.% NH in the electrolyte₄F and 2 vol.% H₂In an electrolytic bath of ethylene glycol mixed solution of O, at the temperature of 25 ℃, the anodic oxidation pulse voltage is 30V, the anodic oxidation time is 1 hour, and the undoped titanium oxide nano-tube grows on the surface of the pure titanium sheet. Washing the un-doped titanium oxide nanotube with deionized water for 5min to remove organic impurities on the surface, and then using N₂And (5) drying by air flow. And then heat treatment is carried out at 500 ℃ for 2 hours, and the undoped titanium oxide nanotube photo-anode is obtained after furnace cooling. The crystal structure is anatase crystal structure, and the photocurrent density is 0.30mA/cm²。

Comparative example 2

The same anodization process and thermal treatment annealing process as in example 1 were used to obtain crystalline Si-doped titanium dioxide nanotubes (crystallized Ti-Si-O nanotubes).

Comparative example 3

The same anodic oxidation process as the example is adopted, the undoped titanium dioxide nanotube grows on the surface of the pure titanium substrate, the undoped titanium dioxide nanotube is subjected to heat treatment at 500 ℃ and heat preservation for 2 hours, and the crystallized undoped titanium dioxide nanotube is obtained after furnace cooling. Then put in 0.5M Na₂SO₄In the solution, under the conditions of reduction voltage of 4V and reduction time of 10min, the reduced TiO with self-doped oxygen vacancy is obtained₂Nanotube and method of manufacturing the samePhoto-anode with photocurrent density of 0.93mA/cm²。

FIG. 1 is a surface topography of a crystallized Ti-Si-O nanotube (also an unreduced Si-doped titania nanotube) in comparative example 2, FIG. 2 is a surface topography of a reduced Ti-Si-O nanotube of example 2, FIG. 3 is an energy spectrum and a chemical composition of a crystallized Ti-Si-O nanotube (also an unreduced Si-doped titania nanotube) in comparative example 2, and FIG. 4 is an energy spectrum and a chemical composition of a reduced Ti-Si-O nanotube of example 2, as can be observed from a comparison of FIGS. 1 and 2: the surface appearance of the Ti-Si-O nanotube is not changed by electrochemical reduction, and the comparison of the surface in the figures 3 and 4 shows that the oxygen content in the reduced Ti-Si-O nanotube is obviously lower than that of the unreduced Ti-Si-O nanotube, which indicates that the Ti-Si-O nanotube is introduced with Ti³⁺Oxygen vacancy.

FIG. 5 is an XPS spectrum of the substances obtained in example 2 and comparative examples 1, 2 and 3, and it can be found that: compared with the undoped titanium oxide nanotube, the combination energy of the Si doping and the reduction treatment Si doping is changed, and SiO is not found₂And the like. Meanwhile, an obvious oxygen vacancy peak (531.6eV) appears after reduction treatment, which indicates that the reduction state Si-doped titanium oxide nanotube photo-anode is successfully prepared.

FIG. 6 is a graph showing the light absorption measurements of the photoanodes obtained in example 2 and comparative examples 1, 2 and 3, and it can be seen that the absorption edge of the Ti-Si-O nanotube photoanode prepared by the electrochemical reduction method is red-shifted from the undoped 388nm to 407nm compared to the undoped titanium oxide nanotube photoanode, and silicon and Ti are co-doped compared to the titanium oxide nanotube photoanode doped with only one of comparative examples 2 and 3³⁺The absorption edge of the/oxygen vacancy titanium dioxide nanotube is also red-shifted. The forbidden band width is reduced, the separation and transmission of the photoproduction electron-hole pairs are facilitated, and the photoelectrocatalysis characteristic is improved to a certain extent.

FIG. 7 is a photocurrent stability test of a reduced Ti-Si-O photoanode. The fact that the photocurrent density of the reduction state Ti-Si-O nanotube photo-anode is not obviously attenuated after being continuously illuminated for nearly 3 hours can be found, which indicates that the photocurrent stability is better.

Table 1 shows the results of examples 1 to 5 and comparative examples 1 to 3For the hydrogen production performance of the photo-anode by photolysis of water, Si and Ti are doped in the table³⁺The photocurrent density and photoelectric conversion efficiency of the reduction state Ti-Si-O photo anode of the oxygen vacancy are both larger than those of undoped titanium dioxide nanotubes, silicon dioxide nanotubes doped with silicon only and Ti doped with silicon only³⁺Oxygen vacancy-containing titanium dioxide nanotubes.

TABLE 1 photolytic hydrogen production performance of Ti-Si-O nanotube photoanode under different reduction processes

In conclusion, the method for preparing reduced Ti-Si-O successfully prepares Si and Ti³⁺Oxygen vacancy co-doped titanium dioxide nanotube, and Si and Ti obtained by using the same³⁺The/oxygen vacancy co-doped titanium dioxide nanotube can better exert Si and Ti³⁺The synergistic advantage of oxygen vacancy and the advantage of large specific surface area of the one-dimensional titanium dioxide nanotube effectively improve the light absorption characteristic and the separation and transmission efficiency of the photo-generated electron-hole pair.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, it is still within the scope of the present invention if they fall within the scope of the claims of the present invention and their equivalents.