阅读说明：本技术 一种温度调控亚氧化钛歧化分解转化率的方法 (Method for regulating disproportionation, decomposition and conversion rate of titanium suboxide by temperature ) 是由 黄富强 黄建涛 徐吉健 赵伟 刘战强 于 2019-04-02 设计创作，主要内容包括：本发明涉及一种温度调控亚氧化钛歧化分解转化率的方法,将亚氧化钛和卤化铵混合后进行热处理,通过调节热处理的温度300～700℃,以实现亚氧化钛的歧化分解转化率的调控；所述亚氧化钛的化学式为Ti<Sub><I>n</I></Sub>O<Sub>2<I>n</I>-1</Sub>,<I>n</I>≥2。(The invention relates to a method for regulating and controlling the disproportionation, decomposition and conversion rate of titanium suboxide by temperature, wherein the titanium suboxide and ammonium halide are mixed and then subjected to heat treatment, and the regulation and control of the disproportionation, decomposition and conversion rate of the titanium suboxide are realized by regulating the temperature of the heat treatment to be 300-700 ℃; the titanium suboxide has a chemical formula of Ti n O n 2‑1 ， n ≥2。)

1. A method for regulating and controlling disproportionation, decomposition and conversion rate of titanium suboxide by temperature is characterized in that the titanium suboxide and ammonium halide are mixed and thenPerforming heat treatment, namely adjusting the temperature of the heat treatment to 300-700 ℃ to realize the regulation and control of the disproportionation decomposition conversion rate of the titanium suboxide; the titanium suboxide has a chemical formula of Ti _n O _n2-1，n≥2。

2. The method for preparing the composite electrode is characterized in that titanium oxide is pressed into the electrode, then the electrode is mixed with ammonium halide for heat treatment, the temperature of the heat treatment is adjusted to be 300-700 ℃, the composite electrodes with different disproportionation degrees are obtained, and the proportion of product phases changes along with the temperature; the titanium suboxide has a chemical formula of Ti _n O _n2-1，n≥2。

3. The method of claim 2, wherein the electrode is in the shape of a cylinder, a wafer, or a cube.

4. The method according to any one of claims 1 to 3, wherein the titanium suboxide is selected from Ti₂O₃、Ti₃O₅And Ti₄O₇At least one of them.

5. The method according to any one of claims 1 to 4, characterized in that titanium dioxide is reduced with a reducing agent to produce the titanium suboxide; according to the chemical formula of the titanium suboxide to be prepared, a reducing agent with the molar excess of 2-10 mol% and titanium dioxide are mixed, the mixture is placed in a vacuum container, and then the temperature is kept at 800-1100 ℃ for 4-10 hours, so that the titanium suboxide is obtained.

6. The method of any one of claims 1-5, wherein the reducing agent is titanium powder, magnesium powder, iron powder, aluminum powder, C, H₂At least one of (1).

7. The method of any one of claims 1-6, wherein the ammonium halide is selected from at least one of ammonium fluoride, ammonium chloride, ammonium bromide, and ammonium iodide.

8. The process according to any one of claims 1 to 7, wherein the molar ratio between the ammonium halide and the titanium suboxide is optionally (0.1 to 1): 1, preferably (0.5 to 1): 1 complete disproportionation ratio for temperature regulation.

9. The method according to any one of claims 1 to 8, wherein the atmosphere of the heat treatment is a vacuum atmosphere.

10. The method according to any one of claims 1 to 9, wherein the heat treatment time is 0.5 to 8 hours.

Technical Field

The invention relates to a method for controlling the disproportionation, decomposition and conversion rate of titanium suboxide by controlling temperature, belonging to the field of synthesis and preparation. The invention also relates to a method for realizing partial conversion of the titanium suboxide electrode by controlling the heat treatment temperature so as to obtain the composite electrode with the inner core and reserved surface layer disproportionation. The black titanium oxide grown in situ can be applied to the fields of photoelectrocatalysis and the like.

Background

Titanium element contained in earth crustThe quantity ranks tenth, and the main existing forms are ilmenite and rutile, which are widely distributed in the earth crust and rock circles. Titanium is very active at high temperatures and is easily combined with oxygen, nitrogen, carbon and other elements. Titanium is element No. 22 of the periodic Table of the elements, and the outermost electron arrangement is 3d²4s²The compounds thus formed are predominantly +2, +3 and +4 valent. Of these, titanium is a compound formed with oxygen, most commonly titanium dioxide (TiO)₂) That is, the valence of the titanium element is + 4; there are, of course, also titanium monoxide (TiO) having a valence of +2 and titanium trioxide (Ti) having a valence of +3₂O₃). In addition, there are a series of non-stoichiometric titanium oxide compounds, such as Ti with an average valence between +3 and +4₃O₅And with Ti₄O₇A phase of magneli, and Ti having an average valence between 0 and +2₆O、Ti₃O、Ti₂O, and the like.

The titanium suboxide as referred to herein is a series of titanium oxy compounds having valence states between +3 and +4, and having a uniform chemical formula Ti_nO_2n-1. Titanium dioxide is an active electrode material with very good blackness, can protect two poles of a battery, and can also be used as a bipolar battery material and an LED black matrix material. A common titanium suboxide is Ti₂O₃，Ti₃O₅And with Ti₄O₇For the representative magneli phase, the oxygen-titanium atomic ratio of the material has a change rule of 1.5-O/Ti < 2. Unlike the black titanium oxide in the defect state, the titanium suboxides have respective crystal structures due to the redistribution of Ti-O elements and can exist stably under a certain chemical ratio. Therefore, the Ti-O ratio can be designed to obtain corresponding pure substances.

It is noted that the chemical formula of these low-valence titanium oxides corresponds to the general formula Ti_nO_2n-1Mathematically, it can be regarded as TiO and TiO₂Combinations of (a) and (b). But from the XRD pattern, the two phases do not show a complex line, but rather correspond to separate lines. Thus, structurally, titanium suboxide is independent and has a corresponding space group. At the same time, XPS valenceThe results of the analysis also confirmed that Ti₃O₅、Ti₄O₇Isotitania in which the valence of titanium is +3 to +4, and which does not contain +2, should be Ti in the valence state₂O₃With TiO₂Combinations of (a) and (b).

Pure titanyl compound, although the average valence is not an integer, is a non-stoichiometric compound, but the structure thereof can be kept stable in a vacuum environment. Therefore, it can be synthesized by designing different Ti-O ratios, such as the permanganate type metal oxide Ti (Chinese patent application No. 201710300837.1, Chinese patent publication No. CN 107416896A) and the reaction temperature is 400-1100 ℃.

The conductivity of black titanium oxide is improved relative to rutile and anatase phases, but it still falls within the semiconductor category. In the aspects of electrocatalysis and photoelectrochemistry, the black titanium oxide with the property of a semiconductor is not beneficial to the transfer of electrons. To improve the conductivity of such materials, carbon materials such as carbon black or acetylene black are added to assist the electron transfer.

Disclosure of Invention

In the present invention, it was found for the first time that the introduction of a certain ammonium halide atmosphere in a vacuum environment or an inert atmosphere causes the structural destruction of the titanium suboxide which is originally stable. Specifically, ammonium halide decomposed hydrogen halide and NH₃Under the atmosphere, the independent crystal structure of the material is changed and converted into TiO and TiO₂Two phases constitute a disproportionation product of core-shell structure. The disproportionation product was black in color and had conductivity comparable to that of metal. For example, titanium suboxide can be disproportionately decomposed into TiO and TiO in a specific ratio by mixing ammonium halide in a specific ratio and heat treating in a closed vacuum tube₂Two phases of (a). In other words, the + 3-valent titanyl compound undergoes disproportionation in the atmosphere generated by decomposition of ammonium halide to produce + 2-and + 4-valent titanyl compounds. Such as pure + 3-valent Ti₂O₃The disproportionation product is TiO and TiO with the mass ratio of 1:1₂. Other titanium dioxides having an average valence between +3 and +4 also have identical experimental results. Further, the low-valent titanium oxide itself has good conductivity and is close to metal, and the conductivity of the black titanium oxide can be improved by partially disproportionating this Ti-O based compound without introducing other impurity elements.

The centering reaction in chemistry shows that different compounds generate oxidation-reduction reaction, and the valence is close to the middle. Meanwhile, according to experiments, pure-phase TiO and TiO are also verified₂After mixing, the reaction occurs. That is, TiO has sufficient reducing ability to convert TiO into TiO₂And (5) reducing the price. However, in the ammonium halide-assisted disproportionation reaction of titanium monoxide, an abnormal result occurs, and the intermediate valence state is dispersed to both sides. This is due to the fact that the atmosphere created by the ammonium halide suppresses the neutralization reaction while forming a specific core-shell structure. The resulting disproportionation product is composed of conductive phase TiO and black TiO₂The structure has potential application in the fields of photoelectrocatalysis and the like.

Titanium suboxide stable at normal temperature and high temperature in vacuum or inert atmosphere is put in ammonium halide atmosphere and can be spontaneously diverged into TiO and TiO₂A two-phase structure. The progress of the disproportionation reaction can be regulated by adjusting the amount of ammonium halide to be incorporated. Although, changing the amount of ammonium halide incorporated is one way to control the conversion rate of disproportionation decomposition. For closed vessels, ammonium halide forms HCl and NH at high temperatures₃Thus, with the risk of overpressure bursting of the closed container, disproportionation products are not available. Therefore, when designing the amount of ammonium halide to be added to the closed vessel, the maximum addition value of ammonium halide is always determined by preliminary experiments to ensure the safety of experiments and production. For small containers, the amount of ammonium halide added per se is small, and the precision control of the amount of ammonium halide is relatively strict to achieve careful control. At the same time, the requirements for the heating device and the vacuum device are adjusted accordingly for containers of different sizes. Therefore, a safer and more reasonable method for controlling the disproportionation, decomposition and conversion rate of the titanium suboxide is urgently needed.

Relative to the adjustment of the mixing amount, the invention provides a method for adjusting the disproportionation, decomposition and conversion rate of the titanium suboxide by the temperature which is easier to adjust for the first time, and the titanium suboxide is subjected toMixing the titanium suboxide with ammonium halide, and then carrying out heat treatment, wherein the temperature of the heat treatment is adjusted to 300-700 ℃ so as to realize the regulation and control of the disproportionation, decomposition and conversion rate of the titanium suboxide; the titanium suboxide has a chemical formula of Ti_nO_2n-1And n is more than or equal to 2. When the disproportionation reaction of titanium suboxide is complete, black titanium dioxide loaded with conductive titanium monoxide in a specific proportion is generated, and the conductive capability of the titanium dioxide semiconductor is improved. The obtained disproportionation conversion rate is different due to different heat preservation temperatures. When the reaction temperature is lower than 600 ℃, titanium suboxide partially remains, and when the reaction temperature is higher than 600 ℃, disproportionation is complete. The experimental results are suitable for powder and also suitable for flaky blocks.

The invention also provides a method for preparing the composite electrode, which is characterized in that titanium dioxide is pressed into the electrode, then the electrode is mixed with sufficient ammonium halide (more than 50 mol%) and then is subjected to heat treatment, and the electrode slice is subjected to disproportionation reaction in different degrees by adjusting the heat treatment temperature to be 300-700 ℃; the titanium suboxide has a chemical formula of Ti_nO_2n-1，n≥2。

Furthermore, when titanium dioxide powder is pre-pressed into an electrode, the thickness of the surface disproportionation layer can be controlled by controlling the reaction temperature under the condition that the ammonium halide doping amount is certain (more than 50 mol%), so that the composite electrode (the structure is shown in figure 11) with the inner core retaining surface layer disproportionation is prepared, and the composite electrode can be applied to the fields of photoelectrocatalysis and the like.

The shape of the electrode is selected according to requirements, and the electrode can be cylindrical, circular or cubic. The shape of the pressed electrode can be cylindrical, round, cubic and the like, but the electrode is ensured not to collapse in the heating process.

Preferably, the titanium suboxide is selected from Ti₂O₃、Ti₃O₅And Ti₄O₇At least one of them.

Titanium dioxide is reduced by a reducing agent to prepare the titanium protoxide, preferably by metallic Ti reduction, without subsequent washing and drying. According to the chemical formula of the titanium suboxide to be prepared, mixing a reducing agent and titanium dioxide weighed according to the molar ratio, placing the mixture in a vacuum container, and then preserving the heat at 800-1100 DEG CObtaining the titanium dioxide after 4-10 hours; preferably, the reducing agent is in excess of 2-10 mol% to ensure the purity of the product. Alternatively, pure titanium oxide can be synthesized by weighing 1 part of the reducing agent in an appropriate excess and 1 part of titanium dioxide. Pure titanium sesquioxide can be synthesized by weighing 1 part of reducing agent in a suitable excess and 3 parts of titanium dioxide. Pure titanium pentoxide can be synthesized by weighing 1 part of a reducing agent in an appropriate excess amount and 5 parts of titanium dioxide. Pure titanium tetroxide can be synthesized by weighing 1 part of reducing agent in proper excess and 7 parts of titanium dioxide. Alternatively, pure Ti is synthesized₂O₃、Ti₃O₅Is at 800-850 ℃; synthesis of pure Ti₄O₇The temperature of the synthesized pure TiO is 820-880 ℃, and the temperature of the synthesized pure TiO is 1000-1100 ℃. The synthesis temperature can be appropriately lowered and the incubation time can be increased accordingly.

In the preparation of the titanium suboxide, the reducing agent is preferably titanium powder, magnesium powder, iron powder, aluminum powder, C, H₂At least one of (1), the resulting product is guaranteed to be dry; preferably, the adding amount of the reducing agent is 2-10 mol% in excess.

Preferably, the ammonium halide is at least one selected from ammonium fluoride, ammonium chloride, ammonium bromide and ammonium iodide.

Optionally, the molar ratio of the ammonium halide to the titanium monoxide is (0.1-1): 1, preferably the complete disproportionation ratio (0.5-1): 1, regulating and controlling the temperature. When the above ratio is less than 0.5, titanium oxide partially remains; when the above ratio is more than 0.5, the disproportionation is complete.

Preferably, the atmosphere for the disproportionation decomposition heat treatment of titanium suboxide is preferably a vacuum atmosphere, ensuring sealing.

The time for the disproportionation decomposition heat treatment of titanium suboxide is preferably 0.5 to 8 hours (for example, 1 to 8 hours). The heat preservation time adopted at different temperatures is uniform.

The invention realizes the purpose of controlling the disproportionation, decomposition and conversion rate of the titanium suboxide by controlling the temperature.

Drawings

FIG. 1 is Ti₂O₃With 50 mol% NH₄XRD patterns of products obtained by reacting Cl at different temperatures;

FIG. 2 is Ti₂O₃With 50 mol% NH₄The phase content of the obtained product calculated by Cl at different temperatures;

FIG. 3 is Ti₂O₃With 50 mol% NH₄Phase diagram of the product obtained with Cl at different temperatures;

FIG. 4 is Ti₃O₅With 50 mol% NH₄XRD patterns of products obtained by reacting Cl at different temperatures;

FIG. 5 is Ti₃O₅With 50 mol% NH₄Calculated phase content of the product obtained with Cl at different temperatures;

FIG. 6 is Ti₃O₅With 50 mol% NH₄Phase diagram of the product obtained with Cl at different temperatures;

FIG. 7 is Ti₄O₇With 50 mol% NH₄XRD patterns of products obtained by reacting Cl at different temperatures;

FIG. 8 is Ti₄O₇With 50 mol% NH₄Calculated phase content of the product obtained with Cl at different temperatures;

FIG. 9 is Ti₄O₇With 50 mol% NH₄Phase diagram of the product obtained with Cl at different temperatures;

FIG. 10 is a standard curve plotted against Rutile;

FIG. 11 is a structural diagram (a) and a performance diagram (b) of a composite electrode prepared according to the present invention;

FIG. 12 is Ti₄O₇With 50 mol% NH₄Cl selects XRD patterns of the obtained product which reacts for different times when the temperature is raised to 600 ℃ under different temperature raising systems;

FIG. 13 is Ti₃O₅With 50 mol% NH₄XPS plot of the product obtained with Cl at 600 ℃ with (a) as starting Ti₃O₅(ii) is the XPS result of the corresponding disproportionation product T1R 2.

Detailed Description

The present invention is further illustrated by the following examples, which are to be understood as merely illustrative and not restrictive.

In the disclosure, the regulation and control of the disproportionation decomposition conversion rate of the titanium suboxide is realized by regulating the heat treatment temperature. Under the condition of ensuring the safety of the closed container, the doping amount of ammonium halide crystals is small, and the influence of adjustment errors is large.

The method for regulating the disproportionation, decomposition and conversion rate of titanium suboxide by temperature regulation provided by the invention is exemplarily described below.

And (3) preparing titanium dioxide. Reducing titanium dioxide with a reducing agent to produce the titanium suboxide. By mixing a reducing agent (e.g., metallic Ti powder, etc.) with white rutile phase TiO in a specific ratio₂In a closed vacuum container, obtaining chemical formulas of TiO and Ti through high temperature reaction at 800-₂O₃、Ti₃O₅、Ti₄O₇Titanium oxide of (2) as a raw material. Specifically, according to the calculated proportioning, metal titanium powder and titanium dioxide powder with corresponding amount are weighed, evenly mixed in an agate smoke mortar and placed in a glass tube. And (3) adopting a vacuum tube sealing method to manufacture a closed container. And then preserving the heat for 4-10 hours at 800-1100 ℃ in a muffle furnace to obtain an ideal raw material. It should be noted that there are many choices of the reducing agent, such as magnesium powder, iron powder, aluminum powder, C, or a reducing gas (hydrogen gas or the like). In order to reduce the presence of impurities and to avoid washing processes, it is therefore preferred to select commercially available titanium powder and titanium dioxide as raw materials for the synthesis of the raw materials. If by other metals or C, H₂And (3) obtaining the disproportionation product, wherein the subsequent steps can be carried out only by adopting drying means such as cold drying, pumping drying and the like after the subsequent washing is carried out, so as to obtain the disproportionation product. However, the absence or purity of the disproportionation product does not affect the subsequent reaction with ammonium halide crystals. The elimination of the washing process is an important factor in the occurrence of disproportionation decomposition. Because, the previous results showed that H₂The presence of O will oxidize the titanium suboxide to some extent to produce titanium dioxide. According to the calculated ratio of the titanium powder to the titanium dioxide, the ratio of the titanium powder is properly increased (the ratio of the reducing agent to the titanium dioxide is required to be according to a chemical reaction formula, and the proper excess of the reducing agent is 2-10mol percent), and the corresponding pure-phase titanium suboxide can be prepared in a closed container. As one example, the methods of the present disclosure synthesize pure Ti₂O₃And Ti₃O₅Is synthesized pure Ti at 800 DEG C₄O₇Is at 850 ℃ and the pure TiO is at 1100 ℃. The temperature can be properly reduced, and the heat preservation time is correspondingly increased. In addition, in order to shorten the reaction time, improve the purity of the product and control the size of the product, it is necessary to ensure that the reactants are dry and the selected raw materials are micron-nanometer sized.

In an alternative embodiment, a vacuum glass tube is used as the closed container, the vacuum being below 0.1 Pa. A certain amount of titanium powder and titanium dioxide are weighed according to the molar ratio, and in order to ensure the purity of the product, the proportion of the reducing agent titanium powder is properly increased, and the proper excess is 2-10 mol%. Optionally, 1 part of titanium powder and 1 part of titanium dioxide are weighed, and pure titanium oxide can be synthesized; weighing 1 part of titanium powder and 3 parts of titanium dioxide, and synthesizing pure titanium sesquioxide; weighing 1 part of titanium powder and 5 parts of titanium dioxide, and synthesizing pure titanium pentoxide; 1 part of titanium powder and 7 parts of titanium dioxide are weighed to synthesize pure titanium tetroxide.

Titanium oxide and ammonium halide are mixed and then are respectively subjected to heat treatment for a certain time at 300-700 ℃ to obtain products with different disproportionation decomposition rates, so that the decomposition rates can be regulated and controlled through the heat treatment temperature. Wherein the ammonium halide is at least one selected from ammonium fluoride, ammonium chloride, ammonium bromide and ammonium iodide. The molar ratio of the ammonium halide to the titanium monoxide is (0.5-1): 1, complete disproportionation is possible. The atmosphere for the heat treatment may be a vacuum atmosphere, or an inert atmosphere; the inert atmosphere is argon atmosphere. The heat treatment time may be 0.5 to 8 hours. Finally, the product can be washed by deionized water, so that residual ammonium halide in the sample can be removed.

Further preferably, the present invention is carried out by selecting ammonium chloride from ammonium halides. Firstly, hydrofluoric acid generated by ammonium fluoride can seriously corrode the pipe wall at high temperature, and the vacuum degree of the sealed container can be damaged; secondly, because of ammonium bromide and ammonium iodide, the byproducts can have dark elemental bromine and iodine, which causes the indispensable washing step; thirdly, decomposition products of the ammonium chloride are colorless substances, condensed ammonium chloride powder is light and can be effectively removed in a fan mode, and a washing step can be omitted. Ammonium chloride is used as a catalyst for the disproportionation reaction of titanium suboxide, and the ammonium chloride and the titanium suboxide in different proportions are mixed to obtain products with different disproportionation degrees; when the proportion of ammonium chloride is high, the disproportionation reaction can be ensured to be complete. It should be noted that the amount of ammonium chloride needs to be controlled so that the decomposed gas does not burst the closed vessel.

It should be noted that the selected vacuum container (e.g. vacuum tube, etc.) should be able to withstand the temperature range of 400-1100 ℃; the vacuum degree as low as possible is selected, so that the proportion of the reducing agent which is required to be remained by pure titanium oxide can be calculated and obtained conveniently.

In the method, titanium suboxide is pressed into an electrode in a mould, and the composite electrode with the core reserved and the surface layer disproportionated can be obtained by regulating and controlling the temperature of heat treatment.

It should be noted that the rate of temperature increase and the rate of temperature decrease used for the heat treatment do not affect the formation of the disproportionation product. Wherein, the cooling process can adopt quenching, air cooling or furnace cooling, etc. In addition, the present invention supplements the effect of the heating system on the disproportionation process to promote the practical application of the reaction. The result shows that the reaction is not influenced by the speed of the temperature rise; the temperature reduction process, no matter quenching, air cooling or furnace cooling, does not influence the disproportionation reaction.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below. In the following examples, the doping ratio of titanium suboxide to ammonium halide was selected to be 2:1, and corresponding experiments were carried out to plot reaction phase diagrams at different temperatures. I.e. Ti₂O₃、Ti₃O₅And Ti₄O₇Mixing with ammonium halide with the above doping ratio, maintaining at different heat treatment temperatures for the same time, measuring XRD pattern of the product, comparing with standard curve, and calculating titanium suboxide in the productTiO and TiO₂And finishing into a phase diagram.