阅读说明：本技术 碳、氮共掺杂的二氧化钛纳米材料及其制备方法和应用 (Carbon and nitrogen co-doped titanium dioxide nano material and preparation method and application thereof ) 是由 王生杰 刘方园 晏梓竣 张亚楠 修阳 徐鲁艺 于 2019-11-25 设计创作，主要内容包括：本发明提出一种碳、氮共掺杂的二氧化钛纳米材料及其制备方法和应用,属于无机纳米材料技术领域,能够解决现有利用二氧化钛制备NADH的体系中需要电子媒介体的参与、反应体系复杂、成本高等技术问题。该技术方案包括(1)将高分子非离子型表面活性剂溶于溶剂中,加入氨基酸分子混匀后,调节体系pH至2-6,得到溶液A；(2)将二氧化钛前驱体溶于有机溶剂中,得到溶液B；(3)将溶液B于搅拌下逐步滴加到溶液A中,通过加热反应,得到二氧化钛凝胶；(4)将所得二氧化钛凝胶于60-120℃下干燥后,煅烧,得到碳、氮共掺杂的二氧化钛纳米材料。本发明所得到的光催化材料可有效应用于NADH的再生中。(The invention provides a carbon and nitrogen co-doped titanium dioxide nano material as well as a preparation method and application thereof, belongs to the technical field of inorganic nano materials, and can solve the technical problems that an electron mediator is required to participate in the conventional system for preparing NADH by utilizing titanium dioxide, the reaction system is complex, the cost is high and the like. Dissolving a high-molecular nonionic surfactant in a solvent, adding amino acid molecules, uniformly mixing, and adjusting the pH value of a system to 2-6 to obtain a solution A; (2) dissolving a titanium dioxide precursor in an organic solvent to obtain a solution B; (3) dropwise adding the solution B into the solution A gradually under stirring, and heating for reaction to obtain titanium dioxide gel; (4) and drying the obtained titanium dioxide gel at 60-120 ℃, and calcining to obtain the carbon and nitrogen co-doped titanium dioxide nano material. The photocatalytic material obtained by the invention can be effectively applied to the regeneration of NADH.)

1. The preparation method of the carbon and nitrogen co-doped titanium dioxide nano material is characterized by comprising the following steps:

dissolving a high-molecular nonionic surfactant in a solvent, adding amino acid molecules, uniformly mixing, and adjusting the pH of a system to 2-6 to obtain a solution A;

dissolving a titanium dioxide precursor in an organic solvent to obtain a solution B;

dropwise adding the solution B into the solution A gradually under stirring, and heating for reaction to obtain titanium dioxide gel;

and drying the obtained titanium dioxide gel at 60-120 ℃, and calcining to obtain the carbon and nitrogen co-doped titanium dioxide nano material.

2. The method according to claim 1, wherein the molar ratio of the nonionic surfactant, the amino acid molecule and the titanium dioxide precursor is (0.5-5): 0.2-1): 1.

3. The method according to claim 1, wherein the nonionic polymer surfactant is at least one selected from the group consisting of polyoxyethylene polyoxypropylene block copolymers F68, P123, P105 and F127, and has a concentration of 0.2 to 2mol/L, preferably 0.2 to 1mol/L, and more preferably 1 mol/L.

4. The method according to claim 1, wherein the amino acid molecule is at least one selected from the group consisting of alanine, glycine, leucine, and isoleucine at a concentration of 0.1 to 1mol/L, preferably 0.1 to 0.5mol/L, and more preferably 0.5 mol/L.

5. The method according to claim 1, wherein the solvent is a mixture of ethanol and water in a volume ratio of (0.5-2): 1, the organic solvent is selected from at least one of methanol, ethanol, isopropanol and acetone; the titanium dioxide precursor is at least one of ethyl titanate, isopropyl titanate and n-butyl titanate, and the concentration of the titanium dioxide precursor is 0.5-5 mol/L.

6. The method according to claim 1, wherein the volume ratio of the solution A to the solution B is (2-6): 1.

7. the method according to claim 1, wherein the heating temperature is 30 to 70 ℃ and the heating time is 12 to 36 hours; the calcination temperature is 300-600 ℃, and the calcination time is 2-6 hours.

8. The carbon and nitrogen co-doped titanium dioxide nano material prepared by the preparation method according to any one of claims 1 to 7.

9. The carbon and nitrogen co-doped titanium dioxide nanomaterial of claim 8, as an application of a photocatalytic material in a reduction type nicotinamide adenine dinucleotide NADH regeneration method.

10. The use according to claim 9, wherein the conversion of NADH regeneration of reduced nicotinamide adenine dinucleotide is above 70%.

Technical Field

The invention belongs to the technical field of inorganic nano materials, and particularly relates to a carbon and nitrogen co-doped titanium dioxide nano material as well as a preparation method and application thereof.

Background

NADH plays a very important auxiliary role in a biochemical synthesis system, and statistics show that more than 400 enzymatic reactions require the participation of NADH. NADH is directly involved in the enzymatic reaction as a reducing agent. However, NADH is expensive and is generally much more expensive than the product obtained by the enzymatic reaction. Therefore, it is necessary to regenerate and recycle the coenzyme.

At present, methods for regenerating NADH mainly include photochemical methods, electrochemical methods and enzymatic methods. Regeneration of coenzymes by photochemical methods is an important part of coenzyme regeneration research. In recent years, photochemical methods have received increasing attention due to their efficient use of inexpensive, clean solar energy, and much research effort has been devoted to establishing efficient NADH regeneration systems (see Shi Q. et al, J. Mol. catalysis: B enzyme catalysis, 2006,43, 44-48; Jiang Z. et al, research in Industrial and engineering chemistry, 2005,44, 4165-.

Among the numerous photocatalysts, titanium dioxide (TiO)₂) The photocatalyst has the advantages of stable chemical property, no toxicity, light corrosion resistance, low cost and the like, and has wide application prospect in the fields of photoelectric conversion and photocatalysis. However, TiO₂The forbidden band width of the photocatalyst is large (3.0-3.2eV), the photocatalyst can only be excited by ultraviolet light with the wavelength of less than 375nm, and the photoproduction electrons and holes are easy to recombine, so that the further application of the photocatalyst in the field of photocatalysis is limited.

To strengthen TiO₂Visible light absorption and enhanced TiO₂The photocatalytic efficiency can be improved by reducing the band gap width of the titanium dioxide by adopting an ion doping method and reducing the recombination rate of photo-generated electrons and holes. Reported by previous investigatorsIn the system for preparing NADH by utilizing titanium dioxide (Jiang Z et al, research on industrial and engineering chemistry, 2005,44, 4165-4170; Wu Y et al, ACS catalysis, 2018,8,5664-5674), an electronic medium is required to participate, so that the whole reaction system is complex and the cost is greatly improved.

Disclosure of Invention

The invention provides a carbon and nitrogen co-doped titanium dioxide nano material and a preparation method and application thereof, the preparation method does not need to introduce an expensive electronic medium, the method is simple and environment-friendly, and the obtained nano material can be used as a photocatalyst for photochemical conversion reaction, so that NADH can have more than 70% of conversion efficiency.

In order to achieve the aim, the invention provides a preparation method of a carbon and nitrogen co-doped titanium dioxide nano material, which comprises the following steps:

dissolving a high-molecular nonionic surfactant in a solvent, adding amino acid molecules, uniformly mixing, and adjusting the pH of a system to 2-6 to obtain a solution A;

dissolving a titanium dioxide precursor in an organic solvent to obtain a solution B;

dropwise adding the solution B into the solution A gradually under stirring, and heating for reaction to obtain titanium dioxide gel;

and drying the obtained titanium dioxide gel at 60-120 ℃, and calcining to obtain the carbon and nitrogen co-doped titanium dioxide nano material.

Preferably, the molar ratio of the added high molecular nonionic surfactant, the amino acid molecules and the titanium dioxide precursor is (0.5-5): 0.2-1): 1.

Preferably, the polymeric nonionic surfactant is at least one selected from the group consisting of polyoxyethylene polyoxypropylene block copolymers F68, P123, P105 and F127, and has a concentration of 0.2 to 2mol/L, preferably 0.2 to 1mol/L, and more preferably 1 mol/L.

Preferably, the amino acid molecule is at least one selected from the group consisting of alanine, glycine, leucine and isoleucine at a concentration of 0.1 to 1mol/L, preferably 0.1 to 0.5mol/L, and more preferably 0.5 mol/L.

Preferably, the solvent is a mixture of ethanol and water, and the volume ratio of the mixture is (0.5-2): 1, the organic solvent is selected from at least one of methanol, ethanol, isopropanol and acetone; the titanium dioxide precursor is at least one of ethyl titanate, isopropyl titanate and n-butyl titanate, and the concentration of the titanium dioxide precursor is 0.5-5 mol/L.

Preferably, the volume ratio of the solution A to the solution B is (2-6): 1.

preferably, the heating temperature is 30-70 ℃, and the heating time is 12-36 hours; the calcination temperature is 300-600 ℃, and the calcination time is 2-6 hours.

The invention provides a carbon and nitrogen co-doped titanium dioxide nano material prepared by the preparation method according to any one technical scheme.

The invention provides an application of the carbon and nitrogen co-doped titanium dioxide nano material as a photocatalytic material in a reduction type nicotinamide adenine dinucleotide NADH regeneration method according to the technical scheme.

Preferably, the conversion rate of NADH regeneration of reduced nicotinamide adenine dinucleotide is more than 70%.

Compared with the prior art, the invention has the advantages and positive effects that:

1. the carbon and nitrogen co-doped titanium dioxide nano material is prepared by the hydrolysis polycondensation reaction of the titanium dioxide precursor regulated and controlled by organic molecules by utilizing the principle of organic-inorganic interface action, the absorption of the carbon and nitrogen co-doped titanium dioxide nano material in a visible light area is greatly enhanced, and when the carbon and nitrogen co-doped titanium dioxide nano material is used as a photocatalyst for photochemical conversion reaction, an expensive electronic mediator is not required to be introduced, so that NADH can have the conversion efficiency of more than 70 percent;

2. compared with the prior art, the preparation method provided by the invention is simple, environment-friendly, low in price and convenient for further industrial generation and commercial popularization.

Drawings

Fig. 1 is a schematic view of a carbon and nitrogen co-doped titanium dioxide nano photocatalytic material provided by an embodiment of the present invention;

fig. 2A is an X-ray photoelectron spectrum (XPS) of the carbon and nitrogen co-doped titanium dioxide nano photocatalytic material provided by the embodiment of the present invention;

fig. 2B is a C1s spectrum in X-ray photoelectron spectroscopy (XPS) of the carbon and nitrogen co-doped titanium dioxide nano photocatalytic material provided by the embodiment of the present invention;

fig. 2C is a graph of N1s in X-ray photoelectron spectroscopy (XPS) of the carbon and nitrogen co-doped titanium dioxide nano photocatalytic material provided by the embodiment of the present invention;

fig. 3 is a diffuse reflection ultraviolet-visible spectrum of the carbon and nitrogen co-doped titanium dioxide nano photocatalytic material and the commercial titanium dioxide P25 provided by the embodiment of the present invention;

fig. 4 is an ultraviolet-visible absorption spectrum of a carbon and nitrogen co-doped titanium dioxide nano photocatalytic material and commercial titanium dioxide P25 when they are photocatalysts and react for 2 hours in the process of catalyzing the regeneration of NADH according to the embodiment of the present invention;

FIG. 5A is a standard curve of absorbance in the UV-VIS spectrum corresponding to different concentrations of NADH aqueous solutions;

fig. 5B is a graph showing the relationship between the conversion yield of NADH and the irradiation time when the carbon and nitrogen co-doped titanium dioxide nano photocatalytic material and the commercial titanium dioxide P25 provided in the embodiment of the present invention are photocatalysts.

Fig. 6 is a NADH conversion curve of the carbon and nitrogen co-doped titanium dioxide nano material prepared by different amino acid dosages as the catalyst according to the embodiment of the present invention.

Fig. 7 is a NADH conversion curve of the carbon and nitrogen co-doped titanium dioxide nanomaterial prepared by using different amounts of the polymeric nonionic surfactant (F127) as the catalyst according to the embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention provides a preparation method of a carbon and nitrogen co-doped titanium dioxide nano material, which comprises the following steps:

dissolving a high-molecular nonionic surfactant in a solvent, adding amino acid molecules, uniformly mixing, and adjusting the pH of a system to 2-6 to obtain a solution A;

dissolving a titanium dioxide precursor in an organic solvent to obtain a solution B;

dropwise adding the solution B into the solution A gradually under stirring, and heating for reaction to obtain titanium dioxide gel;

and drying the obtained titanium dioxide gel at 60-120 ℃, and calcining to obtain the carbon and nitrogen co-doped titanium dioxide nano material.

The principle of the method disclosed in the above embodiment is that a precursor of titanium is added to a solution containing water, a high molecular nonionic surfactant and an amino acid, and a hydrolytic polycondensation reaction is performed to obtain a target product. The advantages of this reaction are: based on a gel sol method, the generation of titanium dioxide and the doping of carbon and nitrogen elements are simultaneously realized through the interface interaction under the regulation and control of an organic matrix, the reaction condition is mild, and the structure of a product is easy to control.

In a preferred embodiment, the high molecular nonionic surfactant is at least one selected from polyoxyethylene polyoxypropylene block copolymers F68, P123, P105 and F127, and the concentration of the high molecular nonionic surfactant is 0.2-2 mol/L.

It should be noted that, in the above method, the high molecular nonionic surfactant plays a role of providing a template for regulating and controlling the polycondensation reaction of the titanium dioxide precursor and the doping of the nonionic element; on the other hand, the mesoporous structure is provided, organic components are removed after calcination, the position occupied by the original high-molecular nonionic surfactant is a hole structure, and the specific surface area and the catalytic activity of the synthesized carbon and nitrogen co-doped titanium dioxide nano material are increased. Therefore, the concentration of the high molecular nonionic surfactant is very critical, and affects the titanium dioxide polycondensation reaction process guided by the high molecular nonionic surfactant on the one hand, and affects the mesoporous structure and catalytic activity of the final product on the other hand, and therefore, the concentration of the high molecular nonionic surfactant needs to be set within the range, and both the concentration of the high molecular nonionic surfactant is less than 0.2mol/L and more than 2mol/L, which affect the titanium dioxide polycondensation reaction process and the mesoporous structure and catalytic activity of the final product. In a further preferred embodiment, the concentration of the polymeric nonionic surfactant is 0.2 to 1mol/L, more preferably 1mol/L, within this range, the ability to catalyze the regeneration of NADH is gradually increased with the increase of the concentration of the polymeric nonionic surfactant, and when it is more than 1M, the effect is reduced with the increase of the concentration of the polymeric nonionic surfactant.

In a preferred embodiment, the amino acid molecule is selected from at least one of alanine, glycine, leucine and isoleucine at a concentration of 0.1-1 mol/L. It can be understood that amino acid molecules all contain carbon and oxygen elements, and have potential as dopants, but whether the desired catalytic effect can be achieved after doping is influenced by many factors, for example, the nature of the amino acid molecule itself affects the interaction with the template and the titanium dioxide precursor, and affects the doping effect. Some other elements also contain elements such as S and the like, and the structure and the properties of the final doped product can be influenced. This example exemplifies the above amino acid molecules as a dopant based on the doping effect, and sets the concentration thereof within the above range, because the doping concentration less than 0.1mol/L or more than 1mol/L leads to a decrease in the catalytic performance of the sample. In a further preferred embodiment, the amino acid molecule concentration is 0.1 to 0.5mol/L, more preferably 0.5mol/L, within this range, the ability to catalyze the regeneration of NADH is gradually increased with the increase of the amount of alanine, and the effect is decreased with the increase of the amount of alanine when it is more than 0.5M.

In a preferred embodiment, the solvent is a mixture of ethanol and water, and the volume ratio of the mixture is (0.5-2): 1, the organic solvent is at least one selected from methanol, ethanol, isopropanol and acetone. It will be appreciated that the titanium dioxide precursor is formed into titanium dioxide by a hydrolytic polycondensation reaction, and therefore water is a necessary reactant. Because the reaction rate of some titanium dioxide precursors in pure water is too fast to control, the method of mixing solvents is adopted to reduce the rate of hydrolytic polycondensation reaction. Ethanol is a commonly used solvent, and has good solubility with both water and titanium dioxide precursors. But not limited to ethanol, other solvents such as methanol, isopropanol, acetone, etc. may be used, and those skilled in the art may select them according to their actual conditions to achieve their purpose.

In a preferred embodiment, the molar ratio of the added high molecular nonionic surfactant, the amino acid molecules and the titanium dioxide precursor is (0.5-5): 0.2-1): 1. As mentioned above, the carbon and nitrogen co-doped titanium dioxide nanomaterial prepared by the above preparation method has multiple dimensions, such as the selected high molecular nonionic surfactant, amino acid molecules and titanium dioxide precursor, and the concentration setting and the proportion relationship of the three components are critical to the final target product. In this embodiment, the molar ratio of the three components is also limited to the above range, and the ratio of the three components may be selected from 0.5:0.2:1, 0.5:0.5:1, 0.5:0.8:1, 0.5:1:1, 1:0.2:1, 1:0.5:1, 1:0.6:1, 1:1:1, 2:0.2:1, 2:0.4:1, 2:0.7:1, 2:1:1, 3:0.2:1, 3:0.5:1, 3:0.9:1, 3:1:1, 4:0.2:1, 4:0.4:1, 4:0.6:1, 4:0.8:1, 4:1: 1:1, 5:0.2:1, 5:0.5:1, 5:0.8:1, 5:1, and the like. In a further preferred embodiment, the titanium dioxide precursor is at least one selected from the group consisting of ethyl titanate, isopropyl titanate and n-butyl titanate, and the concentration thereof is 0.5 to 5 mol/L. For example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5mol/L or any value within the above range.

In a preferred embodiment, the volume ratio of solution a to solution B is (2-6): 1. as mentioned above, the solution a contains the high molecular nonionic surfactant and the amino acid, which are used as the template agent and the doping agent respectively to regulate the polycondensation reaction and the final doping structure of the titanium dioxide precursor in the solution B, so that the ratio of the solution a to the solution B affects the hydrolytic polycondensation process of the titanium dioxide precursor, and affects the product structure such as doping amount, doping sites, doping structure, pore structure, specific surface area, etc., and affects the final catalytic activity. Thus, the ratio of this embodiment is set to the above ratio, and may be, for example, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, or a ratio within the above range.

In a preferred embodiment, the heating temperature is 30-70 ℃ and the heating time is 12-36 hours; the calcination temperature is 300-600 ℃, and the calcination time is 2-6 hours. In this embodiment, the reaction parameters in the heating reaction and the calcining reaction can be selected by those skilled in the art according to actual requirements, for example, the heating temperature can be 35, 40, 45, 50, 55, 60, 65 ℃ or any value in the above range, the time can be 15, 18, 20, 22, 25, 28, 30, 32 hours or any value in the above range, the calcining temperature can be 350, 380, 400, 420, 450, 460, 500, 530, 550 or any value in the above range, and the calcining time can be 3, 3.5, 4, 4.5, 5, 5.5 hours or any value in the above range.

The embodiment of the invention provides a carbon and nitrogen co-doped titanium dioxide nano material prepared by the preparation method according to any one of the embodiments, as shown in fig. 1. The doped titanium dioxide nano material provided by the invention has the advantages that the co-doping of carbon and nitrogen changes the energy band structure, the responsiveness to visible light is improved, and the utilization efficiency of solar energy is higher; on the other hand, the introduction of the mesoporous structure improves the specific surface area of the invented material, and can increase the contact chance of the active site and the reactant, which has an important effect on the improvement of the catalytic activity of the material.

The embodiment of the invention provides an application of the carbon and nitrogen co-doped titanium dioxide nano material as a photocatalytic material in a NADH regeneration method of reduced nicotinamide adenine dinucleotide. In a preferred embodiment, the conversion rate of NADH regeneration of reduced nicotinamide adenine dinucleotide is more than 70%.

In order to more clearly and specifically describe the carbon and nitrogen co-doped titanium dioxide nanomaterial provided by the embodiment of the invention, and the preparation method and application thereof, the following description is given with reference to specific embodiments.