Gaseous deposition-based nano-zinc oxide / graphene composite photocatalyst and method

Abstract

The application discloses a preparation method of a nano zinc oxide / graphene composite photocatalyst based on vapor deposition, and particularly relates to the following steps: S1, preparation of a precursor solution; S2, placing the precursor solution obtained in the step S1 into a thermostat for heat treatment; S3, soaking and washing the wet gel obtained in the step S2 with distilled water; S4, placing the wet gel after soaking and washing into a freeze dryer for rapid freezing and vacuum drying; S5, preparation of a zinc hydroxide aqueous solution; S6, vacuum filtration of the zinc hydroxide aqueous solution; S7, heat treatment of the zinc hydroxide powder obtained in the step S6 to obtain zinc oxide powder; S8, crushing the graphene aerogel obtained in the step S4; and S9, preparation of the nano zinc oxide / graphene composite photocatalyst. The photocatalyst prepared by the method has greatly improved degradation efficiency of organic dyes compared with nano zinc oxide. The application also discloses the nano zinc oxide / graphene composite photocatalyst based on vapor deposition.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation and structure regulation of photocatalysts, and particularly relates to a nano zinc oxide / graphene composite photocatalyst based on vapor deposition and a preparation method of the nano zinc oxide / graphene composite photocatalyst based on vapor deposition. BACKGROUND

[0002] Water is an essential survival resource for human beings. In recent years, water pollution has become increasingly serious, causing great harm to human health and the entire ecological system, and posing a serious threat to the sustainable development of human society. Compared with inorganic pollutants, organic pollutants are more polluting and more difficult to treat. Traditional methods for treating organic pollutants include extraction, adsorption and concentration, but they have problems such as high energy consumption and secondary pollution. Photocatalysts can catalyze the photolysis of various organic and some inorganic substances adsorbed on their surfaces, and are particularly suitable for removing pollutants and microorganisms in air and water.

[0003] Nano zinc oxide is a zinc oxide material with special physical and chemical properties. Compared with traditional zinc oxide materials, nano zinc oxide has a larger specific surface area, higher reaction activity and better photoelectric performance. Therefore, nano zinc oxide is widely used in the fields of catalysts, bactericides, UV filters, etc. However, nano zinc oxide still has problems such as low visible light utilization rate and poor electrical conductivity, which limit its development in the field of photocatalysis.

[0004] Graphene aerogel is a new type of porous material. Due to its extremely high specific surface area, excellent electrical conductivity and good mechanical properties, it has wide application prospects in the fields of environmental governance, catalysts, electrochemical energy storage, etc. Therefore, the combination of graphene aerogel and nano zinc oxide to obtain nano zinc oxide / graphene composite material can effectively improve the electron transfer ability of the zinc oxide surface in the photocatalytic process, enhance its electrical conductivity, thereby inhibiting the recombination of photo-generated electron-hole pairs and improving the photocatalytic efficiency of zinc oxide.

[0005] In the currently reported methods for preparing nano zinc oxide / graphene composite materials ofIn the case, the raw materials are usually completely mixed to make them polymerize to obtain a composite photocatalyst, and the sol-gel method and one-pot method are mainly used. However, the uniformity of the sample obtained by the former is often difficult to control; although the latter can start from relatively simple and easily obtained raw materials, it does not separate intermediates, and directly obtains complex molecules, but the stability of the substance synthesized by this method is not enough. For example, Jia et al. (New Chemical Materials: 1-9 [2023-06-19].) prepared a reduced graphene oxide (rGO) / ZnO nanocomposite with visible light activity by one-pot method. In a disclosed preparation method of a graphite-like phase carbon nitride / graphene / oxidized graphene composite aerogel (National Invention Patent Publication No.: CN113617351A), a graphite-like phase carbon nitride / graphene / oxidized graphene composite aerogel was prepared. In a disclosed zinc oxide aerogel and a preparation method thereof (National Invention Patent Publication No.: CN107973939A), the skeleton of the aerogel is natural cellulose, which is nanocellulose prepared from paper pulp by an oxidation system, and the surface of the aerogel is flaky nanometer zinc oxide grown in situ by low-temperature water bath reaction. In a disclosed recyclable zinc oxide / graphene aerogel photocatalyst and a preparation method thereof (National Invention Patent Publication No.: CN106732514A), a zinc oxide / graphene aerogel photocatalyst is prepared by one-pot method, which has the characteristics of high degradation efficiency of organic pollutants under natural sunlight irradiation, simple preparation process and repeated use. Although the composite photocatalyst in the above scheme has certain photocatalytic ability, the nanometer zinc oxide / graphene composite material prepared by the above method often has poor sample uniformity, long degradation time and low degradation rate of organic dyes, and the light source is difficult to obtain in the degradation reaction of organic dyes. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of a nanometer zinc oxide / graphene composite photocatalyst based on vapor deposition, which greatly improves the degradation efficiency of organic dyes compared with nanometer zinc oxide.

[0007] The second purpose of the present application is to provide a nanometer zinc oxide / graphene composite photocatalyst based on vapor deposition, which greatly improves the degradation efficiency of organic dyes compared with nanometer zinc oxide.

[0008] The first technical solution adopted by the present application is a preparation method of a nanometer zinc oxide / graphene composite photocatalyst based on vapor deposition, which specifically includes the following steps:

[0009] Step 1, preparation of a precursor solution;

[0010] Step 2, the precursor solution obtained in step 1 is placed in a thermostat for heat treatment to accelerate the gelation of the precursor solution and obtain a wet gel;

[0011] Step 3, the wet gel obtained in step 2 is soaked and washed with distilled water;

[0012] Step 4, the wet gel after soaking and washing is placed in a freeze dryer for rapid freezing and vacuum drying to obtain a graphene aerogel;

[0013] Step 5, a zinc hydroxide aqueous solution is prepared;

[0014] Step 6, the zinc hydroxide aqueous solution obtained in step 5 is vacuum filtered to obtain a zinc hydroxide powder;

[0015] Step 7, the zinc hydroxide powder obtained in step 6 is heat treated to obtain a zinc oxide powder;

[0016] Step 8, the graphene aerogel obtained in step 4 is crushed;

[0017] Step 9, a nano-zinc oxide / graphene composite photocatalyst is prepared.

[0018] The application is also characterized in that,

[0019] Step 1 specifically comprises: mixing an industrial graphene oxide aqueous solution and a vitamin C aqueous solution, placing the mixture in an ultrasonic oscillator to mix and react the mixture sufficiently, and obtaining a precursor solution;

[0020] In step 1, the concentration of the vitamin C aqueous solution is 100 mg / mL, and the concentration of the industrial graphene oxide aqueous solution is 2 mg / mL.

[0021] In step 1, the volume ratio of the industrial graphene oxide aqueous solution to the vitamin C aqueous solution is 3:1.2 to 3:2.4.

[0022] In step 2, when the thermostat is selected for heat treatment, the heat treatment temperature is 30℃ to 100℃, and the heat treatment time is 3h to 5h.

[0023] In step 3, after the solution in the container containing the wet gel is poured out, distilled water is poured into the container to soak the wet gel for one day, the water is changed every day, and the soaking and washing process is repeated three times to remove the residual vitamin C solution in the gel.

[0024] In step 4, the rapid freezing time is 1h to 3h, and after the sample is completely frozen, vacuum drying is started, and the vacuum drying time is 22h to 30h.

[0025] The step 5 is specifically: after mixing the zinc acetate dihydrate and distilled water uniformly at room temperature and normal pressure, the zinc acetate dihydrate solution is obtained, the sodium hydroxide solution is added into the zinc acetate dihydrate solution in four equal portions, and the alkali is allowed to react with the zinc acetate dihydrate solution under continuous stirring at room temperature, so that the zinc hydroxide aqueous solution is obtained;

[0026] In the step 5, the concentration of the zinc acetate dihydrate solution is 118 mg / mL.

[0027] In the step 5, the concentration of the sodium hydroxide solution is 40 mg / mL.

[0028] In the step 5, the volume ratio of the zinc acetate dihydrate solution to the sodium hydroxide solution is 1:2, the sodium hydroxide solution is added in each time interval of 1 min, and the amount of the sodium hydroxide solution added in each time is 5-10 mL, and the dropping speed is 5-10 drops per second.

[0029] In the step 6, the vacuum filtration time is 1-3 h.

[0030] In the step 7, the heat treatment temperature is 145-200 DEG C, and the heat treatment time is 1-3 h.

[0031] The step 9 is specifically: the crushed graphene aerogel obtained in the step 8 is placed at one end of the crucible, the nano zinc oxide obtained in the step 7 is placed at the other end of the crucible, the lid of the crucible is covered, the crucible is placed into the tube furnace, and the activated carbon is placed at both ends of the crucible for protection, high-temperature calcination is carried out under the protection of nitrogen atmosphere, and the nano zinc oxide / graphene composite photocatalyst is obtained.

[0032] In the step 9, the mass ratio of the activated carbon, the graphene aerogel and the zinc oxide is 2-10:0.02-0.1:0.02-0.1.

[0033] In the step 9, the tube furnace is heated from room temperature, and after 30-60 min, the temperature reaches 145-200 DEG C, and the temperature is maintained at 145-200 DEG C for 30-60 min, then the temperature is heated to 650-850 DEG C after 60-120 min, and the temperature is maintained at 650-850 DEG C for 30-60 min, and then the sample is naturally cooled to room temperature.

[0034] The second technical scheme adopted by the application is the nano zinc oxide / graphene composite photocatalyst based on vapor deposition, which is prepared by the above method.

[0035] The beneficial effects of the application are:

[0036] (1) The method is simple in process and easy to operate, and the prepared nano zinc oxide / graphene composite photocatalyst is superior to nano zinc oxide in terms of photocatalytic efficiency and cycle stability. The preparation method of the nano zinc oxide / graphene composite photocatalyst effectively solves the problems of nano zinc oxide, such as poor dispersibility, poor conductivity, low solar utilization rate and serious photo corrosion. In addition, the band gap of the nano zinc oxide is effectively adjusted by the method, the light absorption capacity of the nano zinc oxide in the visible light region is enhanced, the visible light utilization rate of the nano zinc oxide is improved, and efficient removal of water organic pollutants under visible light conditions is realized. The excellent photocatalytic performance of the nano zinc oxide is combined with the chemical adsorption performance of the graphene aerogel, the degradation efficiency of the organic dye by the photocatalytic material is greatly improved, and an environmentally friendly and efficient material for degrading organic sewage is obtained.

[0037] (2) The method of the present application is used for compounding nano zinc oxide and graphene aerogel to obtain a nano zinc oxide / graphene composite photocatalyst, thereby improving the efficiency of the nano zinc oxide in photocatalytic degradation of organic dyes. The prepared nano zinc oxide / graphene composite photocatalyst has high photocatalytic performance, and under visible light conditions, the removal rate of rhodamine B dye can reach 90-91.4% after 30 min of irradiation, which is 3.74-3.79 times that of nano zinc oxide under the same conditions; the photocatalytic reaction kinetic constant is 0.085-0.1 min -1 , which is 9-10 times that of nano zinc oxide under the same conditions. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a flowchart of the preparation method of the present application.

[0039] Figure 2 is an experimental effect diagram of the photocatalytic degradation of rhodamine B by the nano zinc oxide / graphene composite photocatalyst prepared in Example 1;

[0040] Figure 3 is an experimental effect diagram of the photocatalytic degradation of rhodamine B by the nano zinc oxide / graphene composite photocatalyst prepared in Example 2;

[0041] Figure 4 is an experimental effect diagram of the photocatalytic degradation of rhodamine B by the nano zinc oxide / graphene composite photocatalyst prepared in Example 3;

[0042] Figure 5 is a rhodamine B degradation curve of intrinsic nano zinc oxide, the nano zinc oxide / graphene composite photocatalyst prepared in Example 1, the nano zinc oxide / graphene composite photocatalyst prepared in Example 2, and the nano zinc oxide / graphene composite photocatalyst prepared in Example 3.

[0043] Figure 6is the reaction kinetics curve of intrinsic nano-zinc oxide, the nano-zinc oxide / graphene composite photocatalyst prepared in Example 1, the nano-zinc oxide / graphene composite photocatalyst prepared in Example 2, and the nano-zinc oxide / graphene composite photocatalyst prepared in Example 3.

[0044] Figure 7 is the reaction kinetics constant histogram of intrinsic nano-zinc oxide, the nano-zinc oxide / graphene composite photocatalyst prepared in Example 1, the nano-zinc oxide / graphene composite photocatalyst prepared in Example 2, and the nano-zinc oxide / graphene composite photocatalyst prepared in Example 3.

[0045] Figure 8 is the SEM image of the nano-zinc oxide / graphene composite photocatalyst prepared in Example 1 of the present application (the scale is 10 μm);

[0046] Figure 9 is the SEM image of the nano-zinc oxide / graphene composite photocatalyst prepared in Example 1 of the present application (the scale is 1 μm);

[0047] Figure 10 is the SEM image of the nano-zinc oxide / graphene composite photocatalyst prepared in Example 2 of the present application (the scale is 10 μm);

[0048] Figure 11 is the SEM image of the nano-zinc oxide / graphene composite photocatalyst prepared in Example 2 of the present application (the scale is 1 μm).

[0049] Figure 12 is the SEM image of the nano-zinc oxide / graphene composite photocatalyst prepared in Example 3 of the present application (the scale is 10 μm);

[0050] Figure 13 is the SEM image of the nano-zinc oxide / graphene composite photocatalyst prepared in Example 3 of the present application (the scale is 1 μm).

[0051] Figure 14 is the TEM image of the nano-zinc oxide / graphene composite photocatalyst prepared in Example 3 of the present application (the scale is 1 μm);

[0052] Figure 15 is the TEM image of the nano-zinc oxide / graphene composite photocatalyst prepared in Example 3 of the present application (the scale is 50 nm, Figure 14 in the enlarged view at A);

[0053] Figure 16 is the TEM image of the nano-zinc oxide / graphene composite photocatalyst prepared in Example 3 of the present application (the scale is 5 nm, Figure 15 in the enlarged view at B). DETAILED DESCRIPTION

[0054] The application will be described in detail below in conjunction with the drawings and specific embodiments.

[0055] The application provides a preparation method of a nano zinc oxide / graphene composite photocatalyst based on vapor deposition, as shown in the following steps. Figure 1

[0056] Step 1, preparation of a precursor solution;

[0057] Step 1 specifically comprises the following steps: mixing an industrial graphene oxide aqueous solution and a vitamin C aqueous solution, and placing them in an ultrasonic oscillator to fully mix and react them, so as to obtain a precursor solution;

[0058] In step 1, the concentration of the vitamin C aqueous solution is 100 mg / mL, and the concentration of the industrial graphene oxide aqueous solution is 2 mg / mL.

[0059] In step 1, the volume ratio of the industrial graphene oxide aqueous solution (industrial-grade graphene oxide with a purity of 95%, a sheet diameter of 10-50 μm, and an oxygen content of >42%) to the vitamin C aqueous solution is 3:1.2-3:2.4.

[0060] Step 2, placing the precursor solution obtained in step 1 in a thermostat for heat treatment to accelerate the gelation thereof, so as to obtain a wet gel;

[0061] In step 2, when the thermostat is selected for heat treatment, the heat treatment temperature is 30-100℃, and the heat treatment time is 3-5 h.

[0062] Step 3, soaking and washing the wet gel obtained in step 2 with distilled water;

[0063] In step 3, after the solution in the container containing the wet gel is poured out, distilled water is poured into the container for soaking for one day, the water is changed every day, and the operation is repeated three times to remove the residual vitamin C solution in the gel.

[0064] Step 4, placing the wet gel after soaking and washing in a freeze-drying machine for rapid freezing and vacuum drying, so as to obtain a graphene aerogel;

[0065] In step 4, the rapid freezing time is 1-3 h, and after the sample is completely frozen, vacuum drying is started, and the vacuum drying time is 22-30 h.

[0066] Step 5, preparation of a zinc hydroxide aqueous solution;

[0067] ​Step 5 is specifically: after mixing zinc acetate dihydrate and distilled water uniformly at room temperature and normal pressure, a zinc acetate dihydrate solution is obtained; sodium hydroxide solution is added into the zinc acetate dihydrate solution in four equal portions, and the base is allowed to react with the zinc acetate dihydrate solution under continuous stirring at room temperature, so as to obtain a zinc hydroxide aqueous solution;

[0068] In step 5, the concentration of the zinc acetate dihydrate solution is 118 mg / mL;

[0069] In step 5, the concentration of the sodium hydroxide solution is 40 mg / mL;

[0070] In step 5, the volume ratio of the zinc acetate dihydrate solution to the sodium hydroxide solution is 1:2, and the sodium hydroxide solution is added in each time interval of 1 min, 5-10 mL each time, and 5-10 drops per second.

[0071] Step 6: the zinc hydroxide aqueous solution obtained in step 5 is vacuum filtered to obtain a zinc hydroxide powder;

[0072] In step 6, the vacuum filtration time is 1-3 h.

[0073] Step 7: the zinc hydroxide powder obtained in step 6 is subjected to heat treatment to obtain a zinc oxide powder;

[0074] In step 7, the heat treatment temperature is 145-200℃, and the heat treatment time is 1-3 h.

[0075] Step 8: the graphene aerogel obtained in step 4 is crushed;

[0076] Step 9: a nano-zinc oxide / graphene composite photocatalyst is prepared.

[0077] Step 9 is specifically: the crushed graphene aerogel obtained in step 8 is placed at one end of a crucible, the nano-zinc oxide obtained in step 7 is placed at the other end of the crucible, the lid of the crucible is covered, the crucible is placed into a tube furnace, and activated carbon is placed at both ends of the crucible for protection, high-temperature calcination is carried out under nitrogen atmosphere protection, and a nano-zinc oxide / graphene composite photocatalyst is obtained;

[0078] In step 9, the mass ratio of the activated carbon, the graphene aerogel and the nano-zinc oxide is 2-10:0.02-0.1:0.02-0.1.

[0079] In step 9, the tube furnace is heated from room temperature, reaches 145-200℃ after 30-60 min, is maintained at 145-200℃ for 30-60 min, is then heated to 650-850℃ after another 60-120 min, is kept at 650-850℃ for 30-60 min, and then is naturally cooled down to room temperature, after which the sample is taken out.

[0080] The application also provides a nano zinc oxide / graphene composite photocatalyst based on vapor deposition, which is prepared by the above method.

[0081] Example 1

[0082] First, 3 mL of industrial-grade graphene oxide aqueous solution with a concentration of 2 mg / mL was placed in a reaction bottle, and then 0.12 mL of vitamin C aqueous solution with a concentration of 100 mg / mL was added, and the mixture was shaken to make the graphene oxide solution and the vitamin C solution fully react, thereby obtaining a precursor solution.

[0083] Second, the precursor solution was placed in a thermostat and heat-treated at 90°C for 3 h to obtain a graphene hydrogel.

[0084] Third, after the solution in the container with the wet gel was poured out, it was soaked in distilled water for one day, and the water was changed every day, and this process was repeated three times to remove the residual vitamin C solution in the gel.

[0085] Fourth, after the soaking and washing were completed, all the solution in the wet gel was poured out, and the obtained wet gel was placed in a vacuum drying machine and frozen for 3 h, and then vacuumizing was started after the sample was completely frozen, and the vacuumizing time was 22 h, thereby obtaining a graphene aerogel.

[0086] Fifth, after zinc acetate dihydrate and distilled water were uniformly mixed at room temperature and under normal pressure, the sodium hydroxide solution was added to the zinc acetate dihydrate solution in four equal portions, with an interval of 1 min each time, 5 mL each time, and 5 drops per second, and the base and the zinc acetate dihydrate solution were fully reacted under continuous stirring at room temperature to obtain a zinc hydroxide aqueous solution. Then, the obtained zinc hydroxide aqueous solution was vacuum filtered for 1 h to obtain a zinc hydroxide powder. Finally, the zinc hydroxide powder was heat-treated at a temperature of 150°C for 2 h to obtain a nano zinc oxide powder.

[0087] Sixth, the obtained graphene aerogel was crushed in a mortar, and 20 mg of the crushed graphene aerogel was weighed and placed at one end of a crucible, and 20 mg of the nano zinc oxide powder was placed at the other end of the crucible, and the lid of the crucible was covered. A total of 4.216 g of heat-treated activated carbon was placed at both ends of the crucible containing the reaction sample, and the reaction sample and the activated carbon were sent into a tube furnace together for high-temperature calcination under the protection of a nitrogen atmosphere. When the tube furnace was selected for high-temperature calcination, the heating started from room temperature, and reached 145°C after 30 min, and then stayed at 145°C for 30 min, and then reached 850°C after 71 min of heating, and stayed at 850°C for 60 min, and then naturally cooled down to room temperature.

[0088] After the high-temperature calcination was completed, a nano zinc oxide / graphene composite photocatalyst was obtained.

[0089] The prepared nanometer zinc oxide / graphene composite photocatalyst photocatalytic degradation of rhodamine B experimental results as shown in Figure 2 It has high photocatalytic efficiency. Under visible light conditions, the removal rate of rhodamine B dye can reach 90.0% after 30 min of light irradiation, which is 3.74 times the photocatalytic degradation efficiency of nanometer zinc oxide under the same conditions. From Figures 8-9 It can be seen that the nanometer zinc oxide / graphene composite photocatalyst has a uniform sheet structure, but a small amount of clusters appear, and the nanometer zinc oxide particles attached to the surface of graphene are less.

[0090] From Figure 5 It can be seen that due to the adsorption of graphene, the adsorption rate and degradation rate of nanometer zinc oxide / graphene composite photocatalyst to rhodamine B are significantly improved compared with nanometer zinc oxide.

[0091] From Figures 6-7 It can be seen that the photocatalytic reaction rate of nanometer zinc oxide / graphene composite photocatalyst is significantly improved compared with nanometer zinc oxide, and the photocatalytic reaction kinetic constant of nanometer zinc oxide / graphene composite photocatalyst is 0.086 min -1 , which is 9 times that of nanometer zinc oxide under the same conditions.

[0092] Example 2

[0093] First, 3mL of industrial-grade graphene oxide aqueous solution with a concentration of 2mg / mL was placed in a reaction bottle, and then 0.12mL of vitamin C aqueous solution with a concentration of 100mg / mL was added. Shake to mix evenly, so that the graphene oxide solution and vitamin C solution react fully, i.e. to obtain the precursor solution.

[0094] Secondly, the precursor solution was placed in a thermostat and heat treated at 90℃ for 3h to accelerate the gelation of graphene.

[0095] Third, after the gelation was completed, the solution in the wet gel was poured out and soaked in distilled water for one day, and the operation was repeated the next day and the day after tomorrow.

[0096] Fourth, after the soaking and washing were completed, all the aqueous solution in the wet gel was poured out, and the obtained wet gel was placed in a vacuum drying machine and frozen for 3h. After the sample was completely frozen, vacuum was started, and the vacuum time was 22h. The graphene aerogel was obtained.

[0097] Fifth, after the zinc acetate dihydrate and distilled water are mixed uniformly at room temperature and normal pressure, the sodium hydroxide solution is added to the zinc acetate dihydrate solution in four equal portions, with an interval of 1 min each time, 10 mL each time, 10 drops per second, and continuous stirring at room temperature, so that the base and the zinc acetate dihydrate solution are fully reacted to obtain a zinc hydroxide aqueous solution. The obtained zinc hydroxide aqueous solution is then vacuum filtered, and the vacuum filtration time is 2 h to obtain a zinc hydroxide powder. Finally, the zinc hydroxide powder is subjected to heat treatment, and the heat treatment temperature is 460°C, and the heat treatment time is 2 h to obtain a nano-zinc oxide powder.

[0098] Sixth, the obtained graphene aerogel is put into a mortar and crushed, and after crushing, 25 mg is weighed and placed at one end of a crucible, and 20 mg of nano-zinc oxide powder is placed at the other end of the crucible, and the cover of the crucible is covered. Six grams of activated carbon subjected to heat treatment are placed at both ends of the crucible containing the reaction sample, and the reaction sample and the activated carbon are sent into a tube furnace together for high-temperature calcination under the protection of a nitrogen atmosphere. When the tube furnace is selected for high-temperature calcination, heating starts from room temperature, and after 30 min, 145°C is reached, and after staying at 145°C for 30 min, heating is continued for 71 min to reach 850°C, and stays at 850°C for 60 min, and then naturally cools down to room temperature.

[0099] After high-temperature calcination is completed, a nano-zinc oxide / graphene composite photocatalyst is obtained.

[0100] The experimental effect diagram of the prepared nano-zinc oxide / graphene composite photocatalyst for photocatalytic degradation of rhodamine B is shown in Figure 3 , which has a high photocatalytic efficiency. Under visible light conditions, the removal rate of rhodamine B dye can reach 91.0% after 30 min of illumination, and the degradation efficiency is 3.78 times that of nano-zinc oxide under the same conditions. From Figures 10-11 , it can be seen that the nano-zinc oxide / graphene composite photocatalyst has a uniform sheet structure, basically overcoming the problem of easy agglomeration of nano-zinc oxide, and the nano-zinc oxide particles are attached to the surface of graphene.

[0101] From Figure 5 , it can be seen that due to the adsorption of graphene, the adsorption rate and degradation rate of the nano-zinc oxide / graphene composite photocatalyst for rhodamine B are significantly improved compared with nano-zinc oxide.

[0102] From Figures 6-7 , it can be seen that the photocatalytic reaction rate of the nano-zinc oxide / graphene composite photocatalyst is significantly improved compared with nano-zinc oxide, and the photocatalytic reaction kinetic constant of the nano-zinc oxide / graphene composite photocatalyst is 0.1 min -1 , which is 10 times that of nano-zinc oxide under the same conditions.

[0103] Example 3

[0104] First, 3mL of industrial-grade graphene oxide aqueous solution with a concentration of 2mg / mL was placed in a reaction bottle, then 0.12mL of vitamin C aqueous solution with a concentration of 100mg / mL was added, and the mixture was shaken to make the graphene oxide solution and the vitamin C solution fully react, thereby obtaining a precursor solution.

[0105] Secondly, the precursor solution was placed in an incubator and heat-treated at 90℃ for 3h to accelerate the formation of graphene gel.

[0106] Thirdly, after the gel was completed, the solution in the wet gel was poured out and soaked in distilled water for washing for one day, and the operation was repeated the next day and the day after.

[0107] Fourthly, after the soaking and washing were completed, all the aqueous solution in the wet gel was poured out, and the obtained wet gel was placed in a vacuum drying machine and frozen for 3h, and then vacuumizing was started after the sample was completely frozen, and the vacuumizing time was 22h, thereby obtaining graphene aerogel.

[0108] Fifthly, after the zinc acetate dihydrate and distilled water were uniformly mixed at room temperature and under normal pressure, the sodium hydroxide solution was added to the zinc acetate dihydrate solution in four equal portions, with an interval of 1min each time, 7mL each time, and 7 drops per second, and the alkali and the zinc acetate dihydrate solution were fully reacted under continuous stirring at room temperature, thereby obtaining a zinc hydroxide aqueous solution. Then, the obtained zinc hydroxide aqueous solution was vacuum filtered for 3h, thereby obtaining zinc hydroxide powder. Finally, the zinc hydroxide powder was heat-treated at a temperature of 200℃ for 3h, thereby obtaining nano-zinc oxide powder.

[0109] Sixthly, the obtained graphene aerogel was crushed in a mortar, 25mg of which was weighed and placed at one end of a crucible, and 20mg of nano-zinc oxide powder was placed at the other end of the crucible, and the lid of the crucible was covered. Six grams of activated carbon heat-treated at both ends of the crucible containing the reaction sample were placed, and the reaction sample and the activated carbon were sent into a tube furnace together for high-temperature calcination under the protection of a nitrogen atmosphere. When the tube furnace was selected for high-temperature calcination, the heating started from room temperature, and reached 145℃ after 30min, and stayed at 145℃ for 30min, and then reached 850℃ after 71min of heating, and stayed at 850℃ for 60min, and then naturally cooled down to room temperature.

[0110] After high-temperature calcination, the nano-zinc oxide / graphene composite photocatalyst was obtained.

[0111] The experimental effect diagram of the prepared nano-zinc oxide / graphene composite photocatalyst photocatalytic degradation of rhodamine B is as follows: Figure 4As shown, it has higher photocatalytic efficiency, and the removal rate of Rhodamine B dye can reach 91.4% after 30 min of light irradiation under visible light conditions, which is 3.79 times the degradation efficiency of nano zinc oxide under the same conditions. From Figures 12-13 It can be seen that the nano zinc oxide / graphene composite photocatalyst has a relatively flat sheet structure, and the overall morphology is dense and uniform. The problem of easy agglomeration of nano zinc oxide is solved, and the nano zinc oxide particles are evenly attached to the surface of graphene.

[0112] The TEM image of the prepared nano zinc oxide / graphene composite photocatalyst is shown in Figures 14-16 From left to right, it is the macrograph, the local enlarged view and the high-resolution view. From the figure, it can be observed that at the edge of the graphene nanosheet, the black nano zinc oxide particles are evenly dispersed on the graphene nanosheet. In the high-resolution view, clear lattice fringes can be observed, which proves that the nano zinc oxide particles have good crystallinity.

[0113] From Figure 5 It can be seen that due to the adsorption of graphene, the adsorption rate and degradation rate of the nano zinc oxide / graphene composite photocatalyst prepared in Examples 1-3 to Rhodamine B are significantly improved compared with nano zinc oxide.

[0114] From Figures 6-7 It can be seen that the photocatalytic reaction rate of the nano zinc oxide / graphene composite photocatalyst prepared in Examples 1-3 is significantly improved compared with nano zinc oxide, and the photocatalytic reaction kinetic constant of the nano zinc oxide / graphene composite photocatalyst is 0.085 min -1 , which is 9 times that of nano zinc oxide under the same conditions.

[0115] Example 4

[0116] First, 3 mL of industrial-grade graphene oxide aqueous solution with a concentration of 2 mg / mL was placed in a reaction bottle, and then 0.12 mL of vitamin C aqueous solution with a concentration of 100 mg / mL was added, and the mixture was shaken to make the graphene oxide solution and the vitamin C solution react fully, thereby obtaining a precursor solution.

[0117] Secondly, the precursor solution was placed in a constant temperature oven and heat-treated at 90°C for 3h to accelerate the gelation of graphene.

[0118] Thirdly, after the gelation was completed, the solution in the wet gel was poured out and soaked in distilled water for one day, and the operation was repeated on the second and third days.

[0119] Fourthly, after the soaking and washing were completed, all the aqueous solution in the wet gel was poured out, and the obtained wet gel was placed in a vacuum drying machine and frozen for 3h. After the sample was completely solidified, vacuum was started, and the vacuum time was 22h, thereby obtaining graphene aerogel.

[0120] Fifth, after mixing the zinc acetate dihydrate and distilled water uniformly at room temperature and normal pressure, the sodium hydroxide solution is added into the zinc acetate dihydrate solution in four equal portions, with an interval of 1 min each time, 6 mL each time, 6 drops per second, and continuous stirring at room temperature, so that the base and the zinc acetate dihydrate solution are fully reacted to obtain a zinc hydroxide aqueous solution. Then, the obtained zinc hydroxide aqueous solution is vacuum filtered, and the vacuum filtering time is 1 h to obtain a zinc hydroxide powder. Finally, the zinc hydroxide powder is subjected to heat treatment, and the heat treatment temperature is 145°C, and the heat treatment time is 1 h to obtain a nano-zinc oxide powder.

[0121] Sixth, the obtained graphene aerogel is put into a mortar and crushed, and after crushing, 20 mg is weighed and put into one end of a crucible, and 25 mg of nano-zinc oxide powder is put into the other end of the crucible, and the cover of the crucible is covered. Six grams of activated carbon subjected to heat treatment are placed at both ends of the crucible containing the reaction sample, and the reaction sample and the activated carbon are sent into a tube furnace together for high-temperature calcination under the protection of a nitrogen atmosphere. When the tube furnace is selected for high-temperature calcination, heating starts from room temperature, and after 30 min, 145°C is reached, and after staying at 145°C for 30 min, heating is continued for 71 min to reach 850°C, and at 850°C, it stays for 60 min, and then it is naturally cooled to room temperature.

[0122] After high-temperature calcination is completed, a nano-zinc oxide / graphene composite photocatalyst can be obtained.

[0123] Example 5

[0124] First, 3 mL of an industrial-grade graphene oxide aqueous solution with a concentration of 2 mg / mL is put into a reaction bottle, and then 0.12 mL of a vitamin C aqueous solution with a concentration of 100 mg / mL is added, and the mixture is shaken to mix uniformly, so that the graphene oxide solution and the vitamin C solution are fully reacted to obtain a precursor solution.

[0125] Secondly, the precursor solution is put into a thermostat, and heat treatment is carried out at 90°C for 3 h to accelerate the formation of graphene gel.

[0126] Thirdly, after the gel is completed, the solution in the wet gel is poured out and soaked in distilled water for washing for one day, and the operation is repeated on the second day and the third day.

[0127] Fourthly, after the soaking and washing are completed, all the aqueous solution in the wet gel is poured out, and the obtained wet gel is put into a vacuum drying machine and frozen for 3 h, and after the sample is completely solidified, vacuum is drawn, and the vacuum drawing time is 22 h to obtain a graphene aerogel.

[0128] Fifth, after mixing the zinc acetate dihydrate and distilled water uniformly at room temperature and normal pressure, the sodium hydroxide solution is added into the zinc acetate dihydrate solution in four equal portions, with an interval of 1 min each time, 8 mL each time, 8 drops per second, and continuously stirred at room temperature, so that the base and the zinc acetate dihydrate solution are fully reacted to obtain a zinc hydroxide aqueous solution. Then the obtained zinc hydroxide aqueous solution is vacuum filtered, and the vacuum filtering time is 1 h to obtain a zinc hydroxide powder. Finally, the zinc hydroxide powder is heat treated to obtain a nano-zinc oxide powder.

[0129] Sixth, the obtained graphene aerogel is put into a mortar and crushed, and after crushing, 20 mg is weighed and put into one end of a crucible, and 30 mg of nano-zinc oxide powder is put into the other end of the crucible, and the cover of the crucible is covered. A total of 5.405 g of activated carbon heat treated is placed at both ends of the crucible containing the reaction sample, and the reaction sample and the activated carbon are sent into a tube furnace together for high-temperature calcination under the protection of a nitrogen atmosphere. When the tube furnace is selected for high-temperature calcination, heating starts from room temperature, and after 40 min, 180°C is reached, and after staying at 180°C for 40 min, heating is continued for another 30 min to reach 800°C, and after staying at 800°C for 40 min, it is naturally cooled to room temperature.

[0130] After high-temperature calcination is completed, a nano-zinc oxide / graphene composite photocatalyst can be obtained.

[0131] Example 6

[0132] First, 3 mL of an industrial-grade graphene oxide aqueous solution with a concentration of 2 mg / mL is put into a reaction bottle, and then 0.12 mL of a vitamin C aqueous solution with a concentration of 100 mg / mL is added, and the mixture is shaken to mix uniformly, so that the graphene oxide solution and the vitamin C solution are fully reacted to obtain a precursor solution.

[0133] Secondly, the precursor solution is put into a thermostat and heat treated at 90°C for 3 h to accelerate the formation of graphene gel.

[0134] Third, after the gel is completed, the solution in the wet gel is poured out and soaked in distilled water for washing for one day, and the operation is repeated on the second and third days.

[0135] Fourth, after the soaking and washing are completed, all the aqueous solution in the wet gel is poured out, and the obtained wet gel is put into a vacuum drying machine and frozen for 3 h, and after the sample is completely solidified, vacuum is started, and the vacuum time is 22 h to obtain a graphene aerogel.

[0136] Fifth, after mixing the zinc acetate dihydrate and distilled water uniformly at room temperature and normal pressure, the sodium hydroxide solution is added into the zinc acetate dihydrate solution in 4 equal portions, 8 mL each time, 8 drops each second, continuously stirring at room temperature, so that the base and zinc acetate dihydrate solution are fully reacted to obtain the zinc hydroxide aqueous solution. Then the obtained zinc hydroxide aqueous solution is vacuum filtered, the vacuum filtering time is 1 h, to obtain the zinc hydroxide powder. Finally, the zinc hydroxide powder is heat treated, the heat treatment temperature is: 200℃; the heat treatment time is: 1 h, to obtain the nano zinc oxide powder.

[0137] Sixth, the obtained graphene aerogel is put into a mortar and crushed, 30 mg of the crushed graphene aerogel is weighed and put into one end of the crucible, 20 mg of the nano zinc oxide powder is put into the other end of the crucible, and the cover of the crucible is covered. 6.324 g of the heat treated activated carbon is placed at both ends of the crucible containing the reaction sample, and the reaction sample and the activated carbon are sent into the tube furnace together for high temperature calcination under the protection of nitrogen atmosphere. When the tube furnace is selected for high temperature calcination, heating starts from room temperature, reaches 200℃ after 60 min, stays at 200℃ for 60 min, then reaches 650℃ after 60 min of heating, stays at 650℃ for 30 min, and then naturally cools down to room temperature.

[0138] After the high temperature calcination is completed, the nano zinc oxide / graphene composite photocatalyst can be obtained.

Claims

1. A method for preparing a nano-zinc oxide / graphene composite photocatalyst based on vapor deposition, characterized in that, Specifically comprising the following steps: Step 1, preparation of a precursor solution; Step 2, the precursor solution obtained in step 1 is placed in an incubator for heat treatment to obtain a wet gel; Step 3, the wet gel obtained in step 2 is soaked and washed with distilled water; Step 4, the wet gel after soaking and washing is placed in a freeze dryer for rapid freezing and vacuum drying to obtain a graphene aerogel; Step 5, preparation of a zinc hydroxide aqueous solution; Step 6, vacuum filtration of the zinc hydroxide aqueous solution obtained in step 5 to obtain zinc hydroxide powder; Step 7, heat treatment of the zinc hydroxide powder obtained in step 6 to obtain nano-zinc oxide powder; Step 8, crushing of the graphene aerogel obtained in step 4; Step 9, preparation of a nano-zinc oxide / graphene composite photocatalyst; Step 9 is specifically: the crushed graphene aerogel obtained in step 8 is placed at one end of a crucible, nano-zinc oxide obtained in step 7 is placed at the other end of the crucible, the cover of the crucible is covered, the crucible is placed in a tube furnace, and activated carbon is placed at both ends of the crucible for protection, high-temperature calcination is carried out under nitrogen atmosphere protection to obtain a nano-zinc oxide / graphene composite photocatalyst; In step 9, the mass ratio of activated carbon, graphene aerogel and nano-zinc oxide is 2-10:0.02-0.1:0.02-0.1; In step 9, the tube furnace is heated from room temperature, reaches 145-200 DEG C after 30-60 min, maintains at 145-200 DEG C for 30-60 min, then is heated to 650-850 DEG C after 60-120 min, stays at 650-850 DEG C for 30-60 min, and then naturally cools down, and the sample is taken out after cooling to room temperature.

2. The method for preparing a vapor-deposition-based nano-zinc oxide / graphene composite photocatalyst according to claim 1, characterized in that, Step 1 is specifically: mixing an industrial graphene oxide aqueous solution and a vitamin C aqueous solution, placing them in an ultrasonic oscillator to fully mix and react to obtain a precursor solution; In step 1, the concentration of the vitamin C aqueous solution is 100 mg / mL, and the concentration of the industrial graphene oxide aqueous solution is 2 mg / mL; In step 1, the volume ratio of the industrial graphene oxide aqueous solution to the vitamin C aqueous solution is 3:1.2-3:2.

4.

3. The method for preparing a vapor-deposition-based nano-zinc oxide / graphene composite photocatalyst according to claim 1, characterized in that, In step 2, when the incubator is selected for heat treatment, the heat treatment temperature is 30-100 DEG C, and the heat treatment time is 3-5 h.

4. The method for preparing a vapor-deposition-based nano-zinc oxide / graphene composite photocatalyst according to claim 1, characterized in that, In step 3, after the solution in the container containing the wet gel is poured out, distilled water is poured in for soaking for one day, the water is changed every day, and the process is repeated three times to remove the residual vitamin C solution in the gel. 5.The method for preparing a vapor-deposition-based nano-zinc oxide / graphene composite photocatalyst according to claim 1, characterized in that, In step 4, the rapid freezing time is 1-3 h, the sample is completely solidified, vacuum is drawn, and the vacuum drying time is 22-30 h.

6. The method for preparing a vapor-deposition-based nano-zinc oxide / graphene composite photocatalyst according to claim 1, characterized in that, Step 5 is specifically: mixing zinc acetate dihydrate and distilled water at room temperature and under normal pressure to obtain a zinc acetate dihydrate solution, adding sodium hydroxide solution in four equal portions into the zinc acetate dihydrate solution, continuously stirring at room temperature, and allowing the alkali and zinc acetate dihydrate solution to fully react to obtain a zinc hydroxide aqueous solution; In step 5, the concentration of the zinc acetate dihydrate solution is 118 mg / mL. In step 5, the concentration of the sodium hydroxide solution is 40 mg / mL; In step 5, the volume ratio of the zinc acetate dihydrate solution to the sodium hydroxide solution is 1:2, and the sodium hydroxide solution is added in 5-10 mL each time with an interval of 1 min, and 5-10 drops per second. 7.The method for preparing a vapor-deposition-based nano-zinc oxide / graphene composite photocatalyst according to claim 1, characterized in that, In step 6, the vacuum filtration time is 1-3 h.

8. The method for preparing a vapor-deposition-based nano-zinc oxide / graphene composite photocatalyst according to claim 1, characterized in that, In step 7, the heat treatment temperature is 145-200 ℃, and the heat treatment time is 1-3 h.

9. A nano zinc oxide / graphene composite photocatalyst based on vapor deposition, characterized in that, Prepared by the method of any one of claims 1-8.

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