Preparation method of nitrogen-doped titanium dioxide and carbon hollow sphere heterojunction photocatalyst and application thereof

Abstract

This invention discloses a method for preparing a nitrogen-doped titanium dioxide and carbon hollow sphere heterojunction photocatalyst, comprising the following steps: 1) preparing a carbon hollow sphere core-shell structure sample based on melamine-formaldehyde nanospheres; 2) preparing a TiO2@carbon core-shell structure sample using the carbon hollow sphere core-shell structure and tetrabutyl titanate as the reaction system; 3) using a one-step method to simultaneously dope nitrogen into the TiO2@carbon core-shell structure to form an N-TiO2@N-doped carbon hollow sphere heterojunction. This invention provides a method for preparing a nitrogen-doped titanium dioxide@carbon hollow sphere heterojunction photocatalyst and its application. This method achieves uniform nitrogen doping and effective composite of TiO2 and carbon hollow spheres through specific steps, and the prepared photocatalyst exhibits excellent photocatalytic performance under both visible and ultraviolet light.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst material preparation technology, and in particular to a method for preparing a heterojunction photocatalyst that is simultaneously doped with nitrogen-doped titanium dioxide and carbon hollow spheres, and its application. Background Technology

[0002] With the increasing severity of climate change and the energy crisis, finding sustainable, clean, and efficient ways to utilize energy has become a core task of scientific research and technological development. Carbon dioxide (CO2), as a major component of greenhouse gases, has led to a series of serious problems such as global warming and sea-level rise due to its massive emissions. Therefore, reducing CO2 emissions and exploring ways to utilize its resources has become an important task for researchers worldwide.

[0003] Solar-driven semiconductor photocatalytic reduction of CO2 is a promising environmentally friendly technology. Under sunlight, using semiconductor materials as catalysts, CO2 is converted into chemical fuels (CO, methane, methanol, etc.), which can not only solve the energy crisis but also achieve carbon peaking and carbon neutrality, forming a green, low-carbon, and sustainable development system. The basic principle of photocatalytic CO2 reduction involves multiple steps, including light absorption, electron excitation, charge separation and migration, and surface catalytic reactions. Under illumination, the photocatalyst absorbs photons and generates photogenerated electrons and holes. Photogenerated electrons have strong reducing properties and can react with CO2 molecules adsorbed on the catalyst surface to generate hydrocarbons and other samples. Simultaneously, photogenerated holes may participate in the oxidation of water to generate oxygen. By rationally designing the structure and composition of the photocatalyst, its optical, electronic, and surface properties can be controlled, thereby improving the activity and selectivity of photocatalytic CO2 reduction.

[0004] Currently, various high-efficiency semiconductor-based photocatalytic systems have been used for carbon dioxide reduction. Among the many photocatalysts, titanium dioxide is widely used in the field of photocatalysis due to its high photocatalytic activity, good chemical stability, safety and non-toxicity, ease of production, and lack of secondary pollution. However, there are still some factors restricting the practical application of TiO2 materials in current research: (1) The recombination efficiency of photogenerated carriers is too high. Electrons and holes generated by TiO2 under photoexcitation recombine rapidly, resulting in a significant reduction in the number of effective electrons actually participating in the photocatalysis or photoelectric conversion process, thereby reducing the quantum efficiency, that is, the efficiency of converting light energy into chemical energy or electrical energy is not high. (2) The spectral response range is limited. TiO2 mainly absorbs light energy in the ultraviolet band, while ultraviolet light accounts for a relatively small proportion in the solar spectrum and has a certain impact on the human body and the environment. Therefore, TiO2 cannot efficiently utilize the abundant visible light resources, which limits its potential in the field of solar energy conversion. In order to overcome this defect, researchers have tried to modify TiO2 by doping with non-metallic elements (such as nitrogen) to expand its spectral response range and improve its photocatalytic performance. In addition, combining TiO2 with other materials (such as carbon materials) to form heterojunctions can also significantly improve the separation efficiency of photogenerated electron-hole pairs, thereby enhancing photocatalytic activity.

[0005] In summary, it is of great significance to develop a heterojunction photocatalyst with high photocatalytic efficiency that can be applied to the photocatalytic reduction of CO2. Summary of the Invention

[0006] In view of this, the present invention provides a method for preparing a heterojunction photocatalyst simultaneously doped with nitrogen-doped titanium dioxide and carbon hollow spheres and its application, so as to provide a catalyst for significantly improving the separation efficiency of photogenerated electron-hole pairs and enhancing photocatalytic activity.

[0007] The technical solution provided by this invention is specifically a method for preparing a heterojunction photocatalyst that is simultaneously doped with nitrogen-doped titanium dioxide and carbon hollow spheres, comprising the following steps:

[0008] 1) Preparation of melamine-formaldehyde nanospheres with core-shell structure;

[0009] The preparation method of the melamine-formaldehyde nanospheres is as follows: formaldehyde, water and NaOH solution are mixed evenly, melamine is added and stirred at 100°C, then the prepared F127 solution is added, stirred at room temperature, and then transferred to a reaction vessel for reaction at 100°C to obtain melamine-formaldehyde nanospheres.

[0010] The melamine-formaldehyde nanospheres were added to a mixed solution of water and ethanol and ultrasonically dispersed evenly. Hexadecyltrimethylammonium bromide, resorcinol and ammonia were added to the ultrasonically dispersed mixed solution. After stirring at 35°C, formaldehyde was added and stirring was continued. The mixture was then cooled to room temperature, allowed to stand, washed with water and dried to obtain melamine-formaldehyde nanospheres with a core-shell structure.

[0011] 2) Using melamine-formaldehyde nanospheres with core-shell structure and tetrabutyl titanate as the reaction system, TiO2@carbon core-shell structure samples were prepared;

[0012] 3) Using a one-step method, N is simultaneously doped into the TiO2@carbon core-shell structure sample to form a heterojunction.

[0013] Preferably, the preparation of TiO2@carbon core-shell structured samples using melamine-formaldehyde nanospheres with core-shell structures and tetrabutyl titanate as the reaction system includes:

[0014] Melamine-formaldehyde nanospheres with a core-shell structure were mixed with anhydrous ethanol and sonicated to make them uniform. Then tetrabutyl titanate was added to the uniformly mixed system and stirred.

[0015] Add the mixed solution of hydrochloric acid, anhydrous ethanol and water dropwise to the stirred solution system, stir at room temperature and let stand for 12-24 hours, then dry at 60-100℃.

[0016] Preferably, the mass of the TiO2@carbon core-shell structure sample is 0.1-0.6g; the amount of anhydrous ethanol is 5-10ml; the ultrasonic time is 20-40 minutes; and the amount of tetrabutyl titanate is 2.5-5ml.

[0017] The volumes of each component in the mixed solution of hydrochloric acid, anhydrous ethanol, and water are 2.5 ml, 1 ml-4 ml, and 2-5 ml, respectively.

[0018] Preferably, the step of simultaneously doping N into the TiO2@carbon core-shell structured sample using a one-step method includes:

[0019] The TiO2@carbon core-shell structure sample was placed in a tube furnace and heated to 150℃ for 40-60 minutes at a rate of 10-15℃ / min in a nitrogen atmosphere. Then, it was calcined to 400℃ for 240-360 minutes at a rate of 1℃ / min to obtain a heterojunction photocatalyst of nitrogen-doped titanium dioxide@carbon hollow spheres.

[0020] The present invention also provides the application of the nitrogen-doped titanium dioxide and carbon hollow sphere heterojunction photocatalyst prepared by the above preparation method, characterized in that the catalyst is used for photocatalytic reduction of CO2.

[0021] This invention provides a method for preparing a heterojunction photocatalyst simultaneously doped with nitrogen-doped titanium dioxide and carbon hollow spheres, and its application. This method achieves uniform doping of nitrogen and effective composite of TiO2 and carbon hollow spheres through specific steps. The prepared photocatalyst exhibits excellent photocatalytic performance under both visible and ultraviolet light.

[0022] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the disclosure of the present invention. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The XRD pattern of the nitrogen-doped titanium dioxide@carbon hollow sphere heterojunction photocatalyst prepared in Example 4 of this invention;

[0026] Figure 2 The TEM image is of the catalyst prepared in Example 4 of this invention;

[0027] Figure 3 The N element distribution diagram of the catalyst prepared in Example 4 of this invention;

[0028] Figure 4 The adsorption equilibrium isotherm diagram of the catalyst prepared in Example 4 of this invention;

[0029] Figure 5 The image shows the photocatalytic reduction yield of CO2 in the ultraviolet-visible region of the catalyst prepared in Example 4 of this invention. Detailed Implementation

[0030] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of methods consistent with some aspects of the invention as detailed in the appended claims.

[0031] To overcome the limitations of existing technologies that prevent TiO2 from efficiently utilizing abundant visible light resources, thus restricting its potential in solar energy conversion, this embodiment provides a method for preparing a nitrogen-doped titanium dioxide@carbon hollow sphere heterojunction photocatalyst, characterized by the following steps:

[0032] 1) Preparation of carbon hollow sphere core-shell structure samples based on melamine-formaldehyde nanospheres;

[0033] 2) TiO2@carbon core-shell structure samples were prepared using carbon hollow sphere core-shell structure and tetrabutyl titanate as the reaction system;

[0034] 3) A one-step method is used to simultaneously dope N into TiO2@carbon core-shell structure to form a heterojunction.

[0035] Specifically, it includes the following steps:

[0036] 1. Preparation of carbon hollow sphere core-shell structure:

[0037] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0038] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0039] 2. Preparation of TiO2@carbon core-shell structure:

[0040] Mix a certain amount of the core-shell structure with anhydrous ethanol and sonicate to make it uniform. Add tetrabutyl titanate to the above system and stir for 30-60 minutes. Then, add a mixed solution of hydrochloric acid, anhydrous ethanol and water dropwise to the above solution. Stir at room temperature for 6-12 hours, let stand for 12-24 hours, and dry at 60-100℃.

[0041] In step 2, the mass of a certain amount of core-shell structure is 0.1-0.6g; the amount of anhydrous ethanol is 5-10ml; the ultrasonic time is 20-40 minutes; the volumes of each component in the mixed solution of hydrochloric acid, ethanol and water are 2.5ml, 1ml-4ml and 2-5ml respectively; and the amount of tetrabutyl titanate is 2.5-5ml.

[0042] Preferably, in step 2, the mass of the core-shell structure is 0.4 g, the amount of anhydrous ethanol is 10 ml, the sonication time is 20 minutes, the amount of tetrabutyl titanate is 4 ml, the stirring time is 60 minutes, and the amounts of each component in the mixed solution of hydrochloric acid, anhydrous ethanol, and water are 2.5 ml, 2.5 ml, and 2 ml, respectively. The stirring time is 12 hours, the mixture is allowed to stand for 24 hours, and then dried at 80°C. In step 3, the first heating rate is 15°C / min, and the calcination is carried out at 150°C for 60 minutes. The second calcination temperature is 400°C, and the calcination time is 300 minutes.

[0043] Among them, the selected core-shell structure with a mass of 0.4g, which is the optimal ratio with titanium dioxide nanoparticles, exhibits the best photocatalytic activity; the selected amount of anhydrous ethanol is 10ml, which has the best dispersion effect of the core-shell structure in the system; the ultrasonic time of 20 minutes is the shortest time to obtain the best dispersion effect; and the catalyst with the highest activity is calcined at 400℃.

[0044] 3. One-step formation of heterojunctions between N-doped carbon hollow spheres and TiO2: The above samples were placed in a tube furnace and calcined at 150℃ for 40-60 minutes under a nitrogen atmosphere at a rate of 10-15℃ / min, followed by calcination at 400℃ for 240-360 minutes at a rate of 1℃ / min to obtain the target product. The phase composition of the product was analyzed using X-ray powder diffraction and transmission electron microscopy; light absorption was analyzed using ultraviolet-visible diffuse reflectance spectroscopy; and the pore distribution and specific surface area of ​​the product were analyzed using N2 adsorption.

[0045] In the above preparation method, during high-temperature calcination, the central melamine-formaldehyde nanospheres decompose into nitrogen-rich gas. As this gas escapes, nitrogen is simultaneously doped into the carbon hollow spheres formed by the carbonization of resorcinol-formaldehyde resin and into TiO2. At high temperature, TiO2 and the carbon hollow spheres combine to form a heterostructure. The hollow structure of the material, the small size effect of the titanium dioxide nanoparticles, the doping of nitrogen, and the heterojunction structure result in a photocatalytic material with a large specific surface area, good absorption of visible light, and high visible light photocatalytic efficiency, making it applicable to energy and environmental fields such as photocatalytic reduction of CO2.

[0046] The specific operating steps for the photocatalytic degradation of organic pollutants in this implementation scheme are as follows: Mix 10 mg of catalyst with 30 mg of ruthenium bipyridine, 4 ml of N,N-dimethylacetamide, 1 ml of water, and 1 ml of triethanolamine, and stir for 30 minutes under dark vacuum conditions. Turn on the light source and filter out ultraviolet light with a 420 nm filter, stir under illumination, and automatically inject the chromatogram every 60 minutes to measure the CO peak area and calculate the CO yield.

[0047] The present invention will be further explained and illustrated below with reference to specific embodiments, but this is not intended to limit the scope of protection of the present invention.

[0048] Example 1

[0049] 1. Preparation of carbon hollow sphere core-shell structure:

[0050] Synthesis of melamine-formaldehyde nanospheres:

[0051] After mixing 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100°C for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6 hours. Then transfer to a reaction vessel and react at 100°C for 24 hours.

[0052] Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of hexadecyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol and 0.05 ml of ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml of formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0053] 2. Preparation of TiO2 and carbon core-shell structure: Mix 0.1g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0054] 3. One-step formation of N-doped carbon hollow spheres@TiO2 heterojunction: The above sample was placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it was calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0055] Example 2

[0056] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0057] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0058] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.2g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0059] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0060] Example 3

[0061] 1. Formation of the core-shell structure of carbon hollow spheres:

[0062] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0063] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0064] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.3g core-shell structure with 10ml anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours and let stand for 24 hours. Dry at 80℃. (3) One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: Place the above sample in a tube furnace and heat it to 150℃ at a rate of 15℃ / min for 60 minutes in a nitrogen atmosphere. Then, calcine it to 400℃ at a rate of 1℃ / min for 300 minutes to obtain the target product.

[0065] Example 4

[0066] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0067] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0068] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0069] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0070] The target product was characterized as follows: X-ray powder diffraction and transmission electron microscopy were used for analysis; light absorption was analyzed using ultraviolet-visible diffuse reflectance spectroscopy; and the pore distribution and specific surface area of ​​the product were analyzed using N2 adsorption. Figure 1-5 As shown, Figure 1 The XRD pattern shows that around 20° represents the hollow carbon sphere phase, while the remaining peaks represent the anatase and rutile phases of titanium dioxide. Figure 2 The image shown is a TEM image of the prepared material, where the hollow spheres are N-doped carbon spheres and the surface nanoparticles are N-doped titanium dioxide; as shown... Figure 3 The figure shows the nitrogen element distribution of the prepared material. This figure demonstrates that both the carbon spheres and the surface titanium dioxide nanoparticles contain nitrogen, achieving simultaneous doping. Figure 4 The figure shows the adsorption equilibrium isotherm diagram of the prepared material. It can be seen that the material prepared by the method of this invention has a mesoporous structure and a high specific surface area; for example... Figure 5 The figure shows the photocatalytic reduction CO2 yield of the prepared material in the UV-Vis region. It can be seen from the figure that CO2 has a high conversion rate under simulated sunlight; after 6 hours of irradiation, the CO yield reached 353 μmol g. -1 .

[0071] Example 5

[0072] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0073] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was added and stirring was continued for 6 hours. After cooling to room temperature, the mixture was allowed to stand for 12 hours, then washed with water and dried.

[0074] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.5g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0075] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0076] Example 6

[0077] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0078] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0079] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.6g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0080] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0081] Example 7

[0082] 1. Formation of the core-shell structure of carbon hollow spheres:

[0083] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0084] ② Formation of core-shell structure: 0.4g of nanospheres were added to a mixed solution of 35ml water and 14ml ethanol and ultrasonically dispersed evenly. 1.2g of hexadecyltrimethylammonium bromide (CTAB), 0.2g of resorcinol and 0.05ml of ammonia were added to the mixed solution and stirred at 35℃ for 30 minutes. Then, 0.6ml of formaldehyde was added and stirring was continued for 6 hours. After cooling to room temperature, the mixture was allowed to stand for 12 hours, washed with water and dried.

[0085] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 5ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0086] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0087] Example 8

[0088] 1. Formation of the core-shell structure of carbon hollow spheres:

[0089] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0090] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0091] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 6ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0092] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0093] Example 9

[0094] 1. Formation of the core-shell structure of carbon hollow spheres

[0095] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0096] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0097] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 8ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0098] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0099] Example 10

[0100] 1. Formation of the core-shell structure of carbon hollow spheres

[0101] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0102] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0103] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 10 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0104] One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample was placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere, and then calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0105] Example 11

[0106] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0107] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0108] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 20 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0109] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0110] Example 12

[0111] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0112] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0113] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 3ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0114] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0115] Example 13

[0116] 1. Formation of the core-shell structure of carbon hollow spheres

[0117] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0118] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0119] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4.5ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0120] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0121] Example 14

[0122] 1. Formation of the core-shell structure of carbon hollow spheres:

[0123] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0124] ② Formation of core-shell structure: 0.4 g nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed evenly. 1.2 g cetyltrimethylammonium bromide (CTAB), 0.2 g resorcinol and 0.05 ml ammonia were added to the mixed solution and stirred at 35 °C for 30 minutes. 0.6 ml formaldehyde was then added and stirring was continued for 6 hours. After cooling to room temperature and standing for 12 hours, the mixture was washed with water and dried.

[0125] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 30 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0126] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0127] Example 15

[0128] 1. Formation of the core-shell structure of carbon hollow spheres:

[0129] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0130] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0131] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 40 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0132] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0133] Example 16

[0134] 1. Formation of the core-shell structure of carbon hollow spheres

[0135] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0136] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0137] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 50 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0138] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0139] Example 17

[0140] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0141] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0142] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 1ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0143] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0144] Example 18

[0145] 1. Formation of the core-shell structure of carbon hollow spheres:

[0146] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0147] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0148] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 1.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0149] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0150] Example 19

[0151] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0152] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0153] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0154] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0155] Example 20

[0156] 1. Formation of the core-shell structure of carbon hollow spheres

[0157] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0158] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0159] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 3ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0160] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0161] Example 21

[0162] 1. Formation of the core-shell structure of carbon hollow spheres:

[0163] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0164] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0165] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 3.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0166] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0167] Example 22

[0168] 1. Formation of the core-shell structure of carbon hollow spheres:

[0169] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0170] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0171] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 4ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0172] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0173] Example 23

[0174] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0175] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0176] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 3ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0177] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0178] Example 24

[0179] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0180] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0181] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 4ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0182] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0183] Example 25

[0184] 1. Formation of the core-shell structure of carbon hollow spheres:

[0185] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0186] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0187] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 5ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0188] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0189] Example 26

[0190] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0191] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0192] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 6 hours, let stand for 24 hours, and dry at 80℃.

[0193] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0194] Example 27

[0195] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0196] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0197] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 7 hours, let stand for 24 hours, and dry at 80℃.

[0198] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0199] Example 28

[0200] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0201] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0202] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 9 hours, let stand for 24 hours, and dry at 80℃.

[0203] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0204] Example 29

[0205] Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour, then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours, then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0206] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0207] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 11 hours, let stand for 24 hours, and dry at 80℃.

[0208] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0209] Example 30

[0210] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0211] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0212] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 12 hours, and dry at 80℃.

[0213] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0214] Example 31

[0215] 1. Formation of the core-shell structure of carbon hollow spheres ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0216] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0217] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 16 hours, and dry at 80℃.

[0218] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0219] Example 32

[0220] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0221] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0222] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 20 hours, and dry at 80℃.

[0223] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0224] Example 33

[0225] 1. Formation of the core-shell structure of carbon hollow spheres:

[0226] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0227] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0228] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 60℃.

[0229] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0230] Example 34

[0231] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0232] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0233] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 70℃.

[0234] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0235] Example 35

[0236] 1. Formation of the core-shell structure of carbon hollow spheres: ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0237] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0238] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 90℃.

[0239] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0240] Example 36

[0241] 1. Formation of the core-shell structure of carbon hollow spheres:

[0242] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0243] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0244] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 100℃.

[0245] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0246] Example 37

[0247] 1. Formation of the core-shell structure of carbon hollow spheres:

[0248] ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml formaldehyde, 40 ml water and 0.2 ml 1M NaOH solution evenly, add 5.0 g melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0249] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0250] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0251] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 60 minutes at a rate of 10°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0252] Example 38

[0253] 1. Formation of the core-shell structure of carbon hollow spheres ① Synthesis of melamine-formaldehyde nanospheres: Mix 9 ml of formaldehyde, 40 ml of water and 0.2 ml of 1M NaOH solution evenly, add 5.0 g of melamine and stir at 100℃ for 1 hour. Then add the prepared F127 solution (8 g F127 + 60 ml H2O) and stir at room temperature for 6-10 hours. Then transfer to a reaction vessel and react at 100℃ for 24 hours.

[0254] ② Formation of the core-shell structure: 0.4 g of nanospheres were added to a mixed solution of 35 ml water and 14 ml ethanol and ultrasonically dispersed. 1.2 g of cetyltrimethylammonium bromide (CTAB), 0.2 g of resorcinol, and 0.05 ml of ammonia were added to the mixed solution. The mixture was stirred at 35°C and added dropwise to the above solution. After stirring at room temperature for 12 hours, it was allowed to stand for 24 hours and then dried at 80°C. After 30 minutes, 0.6 ml of formaldehyde was added, and stirring continued for 6 hours. The mixture was then cooled to room temperature, allowed to stand for 12 hours, washed with water, and dried.

[0255] 2. Preparation of TiO2@carbon core-shell structure: Mix 0.4g of core-shell structure with 10ml of anhydrous ethanol and sonicate for 30 minutes to make it uniform. Add 4ml of tetrabutyl titanate to the above system and stir for 60 minutes. Then, add a mixed solution of 2.5ml hydrochloric acid, 2.5ml anhydrous ethanol and 2ml water dropwise to the above solution. Stir at room temperature for 12 hours, let stand for 24 hours, and dry at 80℃.

[0256] 3. One-step method to form a heterojunction between N-doped carbon hollow spheres and TiO2: The above sample is placed in a tube furnace and heated to 150°C for 40 minutes at a rate of 15°C / min in a nitrogen atmosphere. Then, it is calcined to 400°C for 300 minutes at a rate of 1°C / min to obtain the target product.

[0257] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0258] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a heterojunction photocatalyst simultaneously doped with nitrogen-doped titanium dioxide and carbon hollow spheres, characterized in that, Includes the following steps: 1) Preparation of melamine-formaldehyde nanospheres with core-shell structure; The preparation method of the melamine-formaldehyde nanospheres is as follows: formaldehyde, water and NaOH solution are mixed evenly, melamine is added and stirred at 100°C, then the prepared F127 solution is added, stirred at room temperature, and then transferred to a reaction vessel for reaction at 100°C to obtain melamine-formaldehyde nanospheres. The melamine-formaldehyde nanospheres were added to a mixed solution of water and ethanol and ultrasonically dispersed evenly. Hexadecyltrimethylammonium bromide, resorcinol and ammonia were added to the ultrasonically dispersed mixed solution. After stirring at 35°C, formaldehyde was added and stirring was continued. The mixture was then cooled to room temperature, allowed to stand, washed with water and dried to obtain melamine-formaldehyde nanospheres with a core-shell structure. 2) Using melamine-formaldehyde nanospheres with core-shell structure and tetrabutyl titanate as the reaction system, TiO2@carbon core-shell structure samples were prepared; 3) Using a one-step method, N is simultaneously doped into the TiO2@carbon core-shell structure sample to form a heterojunction.

2. The method for preparing a nitrogen-doped titanium dioxide and carbon hollow sphere heterojunction photocatalyst according to claim 1, characterized in that, The preparation of TiO2@carbon core-shell structured samples using melamine-formaldehyde nanospheres with core-shell structures and tetrabutyl titanate as the reaction system includes: Melamine-formaldehyde nanospheres with a core-shell structure were mixed with anhydrous ethanol and sonicated to make them uniform. Then tetrabutyl titanate was added to the uniformly mixed system and stirred. Add the mixed solution of hydrochloric acid, anhydrous ethanol and water dropwise to the stirred solution system, stir at room temperature and let stand for 12-24 hours, then dry at 60-100℃.

3. The method for preparing a nitrogen-doped titanium dioxide and carbon hollow sphere heterojunction photocatalyst according to claim 2, characterized in that, The mass of the TiO2@carbon core-shell structured sample is 0.1-0.6 g; the amount of anhydrous ethanol is 5-10 ml; the ultrasonic time is 20-40 minutes; and the amount of tetrabutyl titanate is 2.5-5 ml. The volumes of each component in the mixed solution of hydrochloric acid, anhydrous ethanol, and water are 2.5 ml, 1 ml-4 ml, and 2-5 ml, respectively.

4. The method for preparing a nitrogen-doped titanium dioxide and carbon hollow sphere heterojunction photocatalyst according to claim 1, characterized in that, The method of simultaneously doping N into the TiO2@carbon core-shell structured sample using a one-step approach includes: The TiO2@carbon core-shell structure sample was placed in a tube furnace and heated to 150℃ for 40-60 minutes at a rate of 10-15℃ / min in a nitrogen atmosphere. Then, it was calcined to 400℃ for 240-360 minutes at a rate of 1℃ / min to obtain a heterojunction photocatalyst of nitrogen-doped titanium dioxide@carbon hollow spheres.

5. The application of the nitrogen-doped titanium dioxide and carbon hollow sphere heterojunction photocatalyst prepared by any one of the preparation methods described in claims 1-4, characterized in that, The catalyst is used for the photocatalytic reduction of CO2.

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