Photo-thermal conversion film with heterostructure light trapping enhancement and preparation method thereof

文档序号：203715 发布日期：2021-11-05 浏览：6次中文

阅读说明：本技术 具有异质结构陷光增强的光热转换膜及其制备方法 (Photo-thermal conversion film with heterostructure light trapping enhancement and preparation method thereof ) 是由金梦甜王华平蔡一啸陈烨张冬陈仕艳于 2021-07-27 设计创作，主要内容包括：本发明涉及一种具有异质结构陷光增强的光热转换膜及其制备方法,制备方法为：首先向培养皿中加入含有CNT的营养液和木醋杆菌原菌液进行静态培养,得到CNT-BC水凝胶,然后向底部填充满CNT-BC水凝胶的培养皿中加入含有GO的营养液和木醋杆菌原菌液进行静态培养,在CNT-BC水凝胶的上方形成GO-BC水凝胶,得到CNT-GO-BC水凝胶,最后对CNT-GO-BC水凝胶中的GO进行还原,得到具有异质结构陷光增强的光热转换膜；最终制得的光热转换膜为具有复合层结构的CNT-rGO-BC水凝胶,由上层的CNT-BC水凝胶和下层的rGO-BC水凝胶组成,且两者之间通过BC纳米纤维连接。本发明的光热转换膜对近红外光吸收高且光热性能好,能有效的将太阳光的光能转换为热能。(The invention relates to a photo-thermal conversion film with heterostructure light trapping enhancement and a preparation method thereof, wherein the preparation method comprises the following steps: firstly, adding a nutrient solution containing CNT and a acetobacter xylinum raw bacterium solution into a culture dish for static culture to obtain CNT-BC hydrogel, then adding a nutrient solution containing GO and the acetobacter xylinum raw bacterium solution into the culture dish filled with the CNT-BC hydrogel at the bottom for static culture to form GO-BC hydrogel above the CNT-BC hydrogel to obtain CNT-GO-BC hydrogel, and finally reducing GO in the CNT-GO-BC hydrogel to obtain a photo-thermal conversion film with heterostructure light trapping enhancement; the finally prepared photo-thermal conversion film is CNT-rGO-BC hydrogel with a composite layer structure, and consists of CNT-BC hydrogel on the upper layer and rGO-BC hydrogel on the lower layer, and the CNT-BC hydrogel and the rGO-BC hydrogel are connected through BC nano fibers. The photo-thermal conversion film has high near infrared light absorption and good photo-thermal performance, and can effectively convert the light energy of sunlight into heat energy.)

1. The photo-thermal conversion film with the heterostructure light trapping enhancement is characterized in that the film is a CNT-rGO-BC hydrogel with a composite layer structure, and consists of an upper CNT-BC hydrogel and a lower rGO-BC hydrogel; the CNT-BC hydrogel consists of BC hydrogel and CNT distributed in the BC hydrogel, and the rGO-BC hydrogel consists of BC hydrogel and rGO distributed in the BC hydrogel; the CNT-BC hydrogel is connected with the rGO-BC hydrogel through BC nano-fibers.

2. The film of claim 1, wherein the average diameter of the fibers in the CNT-BC hydrogel or the rGO-BC hydrogel is 20-30 nm.

3. The film of claim 1, wherein the thickness ratio of the CNT-BC hydrogel to the rGO-BC hydrogel is 3:1.

4. The film of claim 3, wherein the CNT-BC hydrogel comprises 11-12 wt% of CNTs, the CNTs having an average diameter of 5-15 nm and an average length of 0.5-2 μm; the content of the rGO in the rGO-BC hydrogel is 11-12 wt%, the average sheet diameter of the rGO is 0.5-5 mu m, and the average thickness of the rGO is 1-3 nm.

5. The film of claim 1, wherein the film has a thickness of 1.5-2.5 mm and a light absorption of 93-95.5%; the porosity of the CNT-BC hydrogel is 95-98%, and the porosity of the rGO-BC hydrogel is 83-86%.

6. The method for preparing the photothermal conversion film with heterostructure light trapping enhancement as claimed in any one of claims 1 to 5, wherein a nutrient solution containing CNT and Acetobacter xylinum stock solution are added into a culture dish for static culture to obtain CNT-BC hydrogel, then the nutrient solution containing GO and the Acetobacter xylinum stock solution are added into the culture dish filled with the CNT-BC hydrogel at the bottom for static culture, GO-BC hydrogel is formed above the CNT-BC hydrogel to obtain CNT-GO-BC hydrogel, and finally GO in the CNT-GO-BC hydrogel is reduced to obtain the photothermal conversion film with heterostructure light trapping enhancement.

7. The method according to claim 6, characterized by the following specific steps:

(1) preparing CNT-BC hydrogel;

(1.1) respectively preparing a CNT aqueous dispersion and an HS nutrient solution;

(1.2) adding the CNT aqueous dispersion into the HS nutrient solution in a culture dish, sterilizing the mixed solution, and then carrying out aseptic cooling;

(1.3) adding the acetobacter xylinum original bacterial liquid into the cooled mixed liquid for inoculation, and performing static culture to obtain CNT-BC hydrogel;

(2) preparing CNT-GO-BC hydrogel;

(2.1) respectively preparing GO water dispersion and HS nutrient solution;

(2.2) supplementing and adding HS nutrient solution into a culture dish in which the CNT-BC hydrogel is positioned, adding GO water dispersion into the HS nutrient solution, sterilizing the mixed solution, and then carrying out aseptic cooling;

(2.3) adding the acetobacter xylinum raw bacterium liquid into the cooled mixed liquid for inoculation, and performing static culture to obtain CNT-GO-BC hydrogel;

(3) post-treatment;

(4) reduction;

mixing and reacting the CNT-GO-BC hydrogel after post-treatment with an ascorbic acid solution, and washing and purifying with deionized water to prepare the photo-thermal conversion film with heterostructure light trapping enhancement.

8. The method of claim 7, wherein in the step (1.1), the CNT aqueous dispersion is obtained by adding CNT powder into deionized water and performing ultrasonic dispersion uniformly, and the concentration of the CNT aqueous dispersion is 5-8 mg/mL;

in the step (2.1), the GO water dispersion is obtained by adding GO powder into deionized water and performing ultrasonic dispersion uniformly, wherein the concentration of the GO water dispersion is 5-8 mg/mL;

in the step (1.1) and the step (2.1), the HS nutrient solution is prepared from 40-60 g/L glucose, 3-8 g/L yeast extract, 3-8 g/L peptone and 1-4 g/L Na₂HPO₄、0.5～2g/L KH₂PO₄0.5-2 g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, uniformly stirring, sterilizing at a high temperature of 110-130 ℃ and under a pressure of 0.1-0.3 MPa for 30-50 min by using an autoclave, and carrying out aseptic cooling to 20-28 ℃ to obtain an HS nutrient solution;

in the step (1.3) and the step (2.3), the concentration of the acetobacter xylinum stock solution is 3.5 × 10⁵～4×10⁵cfu/mL。

9. The method of claim 7, wherein in the steps (1.2) to (1.3), the volume ratio of the Acetobacter xylinum stock solution, the CNT aqueous dispersion and the HS nutrient solution is 0.7-0.85: 0.6-2.3: 3-4.5;

in the steps (2.2) to (2.3), the volume ratio of the acetobacter xylinum raw bacterium liquid to the GO water dispersion to the HS nutrient solution is 0.7-0.85: 0.6-2.3: 3-4.5;

in the steps (1.3) and (2.3), the temperature of static culture is 28-30 ℃, and the time is 7-14 days.

10. The method of claim 7, wherein in the step (4), the concentration of the ascorbic acid solution is 3-10 wt%, the mass ratio of GO in the post-treated CNT-GO-BC hydrogel to the ascorbic acid solution is 1:15, the reaction temperature is 60-80 ℃, and the reaction time is 6-8 h.

Technical Field

The invention belongs to the technical field of photo-thermal conversion materials, and relates to a photo-thermal conversion film with heterostructure light trapping enhancement and a preparation method thereof.

Background

Excessive consumption of chemical energy sources such as coal, petroleum and natural gas is not favorable for sustainable development and is also a main cause of environmental pollution. The total consumption of traditional energy accounts for more than 80% of the total consumption of the whole world, so that clean energy is urgently needed to replace fossil energy, and the problems of environmental pollution and climate change are relieved. Among all renewable energy sources, solar energy has the characteristics of inexhaustibility, stable output and the like, is most hopeful to be applied in industry on a large scale, and can solve a plurality of challenges facing the society.

China has very rich solar energy resources, and the total solar energy radiation amount of rich areas such as Tibet and Qinghai every year is 8400MJ/am²The total radiation amount of deficient areas such as Sichuan and Guizhou can reach 3400MJ/am². The photoelectric effect and the photothermal effect are the main ways of solar energy utilization so far, wherein the photothermal effect refers to the way of converting solar energy into heat energy by using a light absorption material, and is a way of wider application and higher energy utilization rate (up to more than 90%). However, solar thermal energy conversion has problems: 1) the storage is difficult due to low efficiency in application; 2) the required optical equipment is high in cost and is not fully utilized; 3) the traditional photo-thermal generator device is huge, the system is complex, and the small-scale portable requirement cannot be met. Therefore, it is current to find a way to better develop and utilize solar photo-thermal conversionTasks and goals.

Solar water evaporation is to convert solar energy into heat energy to the maximum extent, and heat the water body by the converted heat energy to generate steam. There are three main routes of water evaporation at this stage: 1) the solar absorber is arranged at the bottom of a bulk phase (bulk), and the bottom absorbing material converts absorbed solar energy into heat energy so as to heat the whole bulk phase water; 2) the solar absorber evaporates water dispersed in the bulk phase in the form of nanofluid, and the uniformly dispersed nanofluid converts sunlight into heat energy to heat the whole bulk phase water; 3) the solar absorber is positioned at the gas-liquid interface where the converted heat is converted to water for heating the gas-liquid interface. The third mode is an emerging technology in recent years, the evaporation system has higher steam generation efficiency and thermal response speed, the system structure is simple, and a feasible scheme can be provided for the efficient portable solar photo-thermal evaporation system.

Conventional solar evaporation disperses a photothermal conversion material in water for bulk heating, and in order to minimize heat loss associated with bulk heating, interfacial solar evaporation by a method of floating the photothermal conversion material at an air-water interface has been proposed and widely verified in the past few years. As one of key components of a solar interface seawater evaporator, a photothermal conversion material is crucial and directly converts light into heat, so that the evaporation of water is promoted.

The literature (Scalable, Flexible, Durable, and Salt-Tolerant CuS/background Cellulose Gel Membranes for Efficient Solar Evaporation, ACS Sustainable chem. Eng.2020,8, 9017-; patent CN201911391562.2 discloses a membrane material for desalination of seawater by solar interface evaporation and a preparation method thereof, wherein a PAA nanofiber membrane is prepared by adopting an electrostatic spinning technology, and is imidized by heating and pressurizing to obtain a PI nanofiber membrane, and finally the surface of the PI membrane is ablated by adopting a laser ablation technology to form porous and fluffy graphene fibers on the surface of the PI membrane; patent No. cn201911007671.x discloses a photothermal conversion film, a method for preparing the same, and a double-layer evaporation structure for solar vapor generation, which utilize CuO @ CF and CuO/Ag @ CF as photothermal conversion films. However, the photothermal conversion films disclosed in these prior arts all have problems of low light capturing efficiency and light utilization efficiency, which in turn results in low evaporation rate of the solar interface seawater evaporator made therefrom.

Therefore, a photo-thermal conversion film with heterostructure light trapping enhancement and a method for preparing the same are needed to solve the above problems.

Disclosure of Invention

The present invention is directed to solving the above-mentioned problems of the prior art and to providing a photothermal conversion film with heterostructure light trapping enhancement and a method for making the same.

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

the photo-thermal conversion film with the heterostructure light trapping enhancement is a CNT (carbon nano tube) -rGO (reduced graphene oxide) -BC (bacterial cellulose) hydrogel with a composite layer structure, and consists of an upper CNT-BC hydrogel and a lower rGO-BC hydrogel; the CNT-BC hydrogel consists of BC hydrogel and CNT distributed in the BC hydrogel, and the rGO-BC hydrogel consists of BC hydrogel and rGO distributed in the BC hydrogel; the CNT-BC hydrogel and the rGO-BC hydrogel are connected through naturally formed BC nano-fibers (the CNT-BC hydrogel and the rGO-BC hydrogel are in direct transition and substantially belong to the same network).

As a preferred technical scheme:

the average diameter of the fiber in the CNT-BC hydrogel or the rGO-BC hydrogel is 20-30 nm.

The photo-thermal conversion film with heterostructure light trapping enhancement has the thickness ratio of the CNT-BC hydrogel to the rGO-BC hydrogel of 3: 1; the CNT-BC hydrogel contains 11-12 wt% of CNTs, the CNTs have an average diameter of 5-15 nm, and the CNTs have an average length of 0.5-2 μm; the content of the rGO in the rGO-BC hydrogel is 11-12 wt%, the average sheet diameter of the rGO is 0.5-5 mu m, and the average thickness of the rGO is 1-3 nm.

The thickness of the photo-thermal conversion film with the heterostructure light trapping enhancement is 1.5-2.5 mm, and the light absorption rate is 93-95.5%; the porosity of the CNT-BC hydrogel is 95-98%, and the porosity of the rGO-BC hydrogel is 83-86%.

The invention also provides a method for preparing the photo-thermal conversion film with heterostructure light trapping enhancement, which comprises the steps of firstly adding nutrient solution containing CNT and acetobacter xylinum stock solution into a culture dish for static culture to obtain CNT-BC hydrogel, then adding nutrient solution containing GO (graphene oxide) and acetobacter xylinum stock solution into the culture dish filled with the CNT-BC hydrogel at the bottom for static culture, forming GO-BC hydrogel above the CNT-BC hydrogel to obtain CNT-GO-BC hydrogel, and finally reducing GO in the CNT-GO-BC hydrogel to obtain the photo-thermal conversion film with heterostructure light trapping enhancement.

The growth rule of acetobacter xylinum is from bottom to top, so the CNT-BC hydrogel is filled in the bottom of a culture dish firstly, then nutrient solution containing GO and acetobacter xylinum stock solution are added into the culture dish, the GO-BC hydrogel is formed above the CNT-BC hydrogel, the CNT-GO-BC hydrogel and the GO in the CNT-GO-BC hydrogel are reduced to obtain the photo-thermal conversion film with heterostructure light trapping enhancement.

The integrated double-layer composite membrane is prepared by a bottom-up biological assembly method in consideration of the growth rule of acetobacter xylinum, because the acetobacter xylinum is aerobic bacteria, a certain amount of oxygen is dissolved in culture liquid at the beginning stage of culture, and the oxygen on a gas-liquid interface is sufficient, so that the acetobacter xylinum in and on the surface of the liquid at the stage can normally grow, reproduce and metabolize, and a certain amount of BC fibers can be generated at two parts; if GO-BC hydrogel is prepared firstly, GO is assembled and fixed in the initially formed cellulose gel in the process to form GO-BC hydrogel, then CNT-BC hydrogel is prepared, along with the lapse of time, when the dissolved oxygen in the liquid is gradually reduced or even exhausted, the BC growth rate of a gas-liquid interface is far greater than the BC growth rate in the liquid, CNT is fixed in CNT-BC composite gel and gradually moves down to the lower part of the liquid, and meanwhile, a white pure BC layer grows above the composite hydrogel and influences the use of the membrane.

According to the invention, by adopting an in-situ culture method, a heterojunction double-layer structure which is closely connected in structure and cannot be mechanically stripped can be obtained through BC in-situ culture, and the high surface area with a large number of hydroxyl groups on the surface of BC provides a plurality of active sites for loading a photo-thermal conversion material, so that good photo-thermal conversion performance is obtained, and efficient solar interface evaporation is realized. Compared with only one material cultured in situ, light reaches the lower layer of rGO-BC hydrogel through the gaps of the upper layer of CNT-BC hydrogel (the cylindrical single CNT have very many gaps), and is reflected back to the upper layer of CNT-BC hydrogel to achieve secondary reflection or aggregate scattering in the rGO-BC hydrogel, so that the capture rate of the light is high.

As a preferred technical scheme:

the method comprises the following specific steps:

(1) preparing CNT-BC hydrogel;

(1.1) respectively preparing a CNT aqueous dispersion and an HS nutrient solution;

(1.2) adding the CNT aqueous dispersion into the HS nutrient solution in a culture dish, sterilizing the mixed solution, and then carrying out aseptic cooling;

(1.3) adding the acetobacter xylinum original bacterial liquid into the cooled mixed liquid for inoculation, and performing static culture to obtain CNT-BC hydrogel;

(2) preparing CNT-GO-BC hydrogel;

(2.1) respectively preparing GO water dispersion and HS nutrient solution;

(2.3) adding the acetobacter xylinum raw bacterium liquid into the cooled mixed liquid for inoculation, and performing static culture to obtain CNT-GO-BC hydrogel;

(3) post-treatment (sequentially carrying out deionized water washing, alkaline boiling of a NaOH solution with the concentration of 1 wt% for 30min, washing with deionized water to be neutral, and washing with deionized water for 6-12 h);

(4) reduction;

According to the method, in the step (1.1), the CNT aqueous dispersion is obtained by adding CNT powder into deionized water and performing ultrasonic dispersion uniformly, and the concentration of the CNT aqueous dispersion is 5-8 mg/mL;

in the step (1.3) and the step (2.3), the concentration of the acetobacter xylinum stock solution is 3.5 × 10⁵～4×10⁵cfu/mL。

In the method, in the steps (1.2) to (1.3), the volume ratio of the acetobacter xylinum raw bacterium solution to the CNT aqueous dispersion to the HS nutrient solution is 0.7-0.85: 0.6-2.3: 3-4.5;

in the steps (2.2) to (2.3), the volume ratio of the acetobacter xylinum raw bacterium liquid to the GO water dispersion to the HS nutrient solution is 0.7-0.85: 0.6-2.3: 3-4.5;

the volume ratio of the acetobacter aceti stock solution, the CNT aqueous dispersion (GO aqueous dispersion) and the HS nutrient solution is set as follows: in the process of growth of the bacterial cellulose, growing CNT and GO lamella are continuously captured by growing BC nano fibers, and finally the CNT is combined with the BC nano fibers and uniformly dispersed in a BC three-dimensional nano network;

in the steps (1.3) and (2.3), the temperature of static culture is 28-30 ℃, and the time is 7-14 days.

According to the method, in the step (4), the concentration of the ascorbic acid solution is 3-10 wt%, the mass ratio of GO in the CNT-GO-BC hydrogel subjected to post-treatment to the ascorbic acid solution is 1:15, the reaction temperature is 60-80 ℃, and the reaction time is 6-8 h.

The present invention has significant differences from the schemes of the literature (Scalable, Flexible, Durable, and Salt-Tolerat CuS/Bacterial cell Membranes for effective interface Solar evaluation, ACS Sustainable chem. Eng.2020,8, 9017-:

(1) the photothermal conversion material of this document uses only copper sulfide, while the present invention uses a nanocomposite of one-dimensional carbon nanotubes and two-dimensional graphene;

(2) this document is completely different from the present invention in the membrane structure configuration (surface, internal, cross-sectional structure);

(3) the preparation process of the film disclosed by the document is complex, a two-step method (soaking and heating) is required for preparing the photothermal conversion film, and CuS is not uniform; in the document, bacterial cellulose is soaked in a functional solution to obtain bacterial cellulose with copper ions, the bacterial cellulose is disordered, a regular three-dimensional structure is formed by in-situ culture, and the bacterial cellulose is used as a framework structure to support the whole photothermal layer; different from the suction filtration method or the soaking method of the document, the invention can obtain a heterojunction double-layer structure which is closely connected in structure and can not be mechanically stripped through in-situ culture of the bacterial cellulose, and the high surface area with a large number of hydroxyl groups on the surface of the bacterial cellulose provides a plurality of active sites for loading a photo-thermal conversion material, thereby obtaining good photo-thermal conversion and realizing efficient solar interface evaporation;

(4) the material surface photothermal conversion principle (light absorption enhancement mechanism) of the document is also essentially different from the invention;

according to the invention, CNT, GO and BC are used as raw materials, and a vertical gradient photo-thermal conversion film with heterostructure light trapping enhancement is constructed by a biological culture method. Because the light trapping structure with the micro-nano size is formed, the incident light path can be enhanced through multiple refraction and scattering in the film, so that the light absorption is effectively enhanced, and the evaporation rate and the conversion efficiency are improved. Specifically, when incident light irradiates, the upper layer heterostructure refracts or scatters light to the lower layer, then the lower layer further refracts and scatters light, a part of the light penetrates through the gaps of the CNT-BC hydrogel (wherein cylindrical CNTs have a large number of pores) of the upper layer to reach the rGO-BC hydrogel (wherein the rGO sheet has a higher specific surface area and a wrinkled surface) of the lower layer, the light path is reflected back to the CNT-BC hydrogel of the upper layer to achieve secondary reflection or scattering in the rGO-BC hydrogel, the light is divergent, the sunlight can be regarded as rays emitted from one point, when the sunlight which is diffused by the light-heat conversion film irradiates, refracts and reflects on the film, the irregular light path process enables the light-heat layer to have multiple possibilities for receiving the sunlight, and through the light propagation process, the original light path is increased, further improving the light capture efficiency and light utilization rate. The evaporation rate of the seawater evaporator on the solar interface is improved by utilizing the high-efficiency capture of light by the vertical heterostructure and combining the strong water-guiding and heat-insulating effect of BC.

Has the advantages that:

(1) the invention constructs the vertical gradient carbon nano tube/graphene oxide/bacterial cellulose heterostructure photo-thermal conversion film by a biological culture method, and the method is simple, simple and convenient to operate and easy for large-scale production;

(2) the prepared photo-thermal conversion film shows a good light trapping effect, reduces the energy loss of sunlight due to reflection, improves the light absorption efficiency of materials, and enables the constructed solar seawater desalination evaporator to have a high evaporation rate;

(3) the prepared photo-thermal conversion film has the characteristics of high near infrared light absorption and good photo-thermal performance, and can effectively convert the light energy of sunlight into heat energy and promote a new application scene of cellulose materials.

Drawings

Fig. 1 is a schematic diagram of light absorption of the photothermal conversion films of example 1, comparative example 1, and comparative example 2;

FIG. 2 is an electron microscope structure diagram of the photothermal conversion film with heterostructure light trapping enhancement prepared in example 1, wherein the left figure is a micro-topography diagram of the photothermal conversion film CNT-rGO-BC prepared in example 1, the middle figure is a micro-topography diagram of the upper layer CNT-BC of the photothermal conversion film prepared in example 1, and the right figure is a micro-topography diagram of the lower layer rGO-BC of the photothermal conversion film prepared in example 1;

FIG. 3 is an infrared test spectrum of a photothermal conversion film with heterostructure light trapping enhancement made in example 1;

fig. 4 is a graph showing the evaporation performance of seawater of the photo-thermal conversion film with heterostructure light trapping enhancement prepared in example 1.

Detailed Description

The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

In the following embodiments, a seawater evaporation performance test is performed on the photothermal conversion film with heterostructure light trapping enhancement, and the method for measuring the evaporation rate is as follows: a solar steam generation experiment was performed using a solar simulator (CEL-HXF300, AM 1.5); the intensity of the solar simulator was adjusted using an optical densitometer (CEL-NP2000) to a solar intensity of 1kWm^-2(ii) a Round toolA photothermal conversion film (the size: the diameter is equal to 4.4cm, and the thickness is shown in specific examples) with heterostructure light trapping enhancement is placed on a circular BC pure film (the size: the diameter is equal to the photothermal conversion film, and the thickness is equal to 2mm), a circular polystyrene foam (the size: the diameter is equal to the photothermal conversion film, and the thickness is equal to 0.8cm) is placed under the BC pure film, an evaporation device consisting of the photothermal film, the BC pure film and the polystyrene foam is floated on water in a beaker, the mass change of the water is recorded in real time under the sun irradiation or dark condition by using an electronic mass balance, the precision is 0.001g, and the whole experimental process is carried out under the environmental condition and the room temperature (the temperature is 25 ℃ and the humidity is 60%);

the evaporation rate is calculated as:

wherein v represents the evaporation rate; m represents the difference between the evaporation quality in sunlight and the evaporation quality in darkness; s represents the surface area of the photothermal film; t represents time.

Example 1

The preparation method of the photo-thermal conversion film with the heterostructure light trapping enhancement comprises the following specific steps:

(1) preparing CNT-BC hydrogel;

(1.1) respectively preparing a CNT aqueous dispersion and an HS nutrient solution;

the CNT aqueous dispersion is obtained by adding CNT powder into deionized water and performing ultrasonic dispersion uniformly, wherein the concentration of the CNT aqueous dispersion is 5 mg/mL;

the HS nutrient solution is composed of 40g/L glucose, 3g/L yeast extract, 3g/L peptone and 1g/L Na₂HPO₄、0.5g/L KH₂PO₄0.5g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 110 deg.C under 0.3MPa for 30min with an autoclave, and cooling to 28 deg.C under aseptic condition to obtain HS nutrient solution;

(1.2) adding the CNT aqueous dispersion into the HS nutrient solution in a culture dish, sterilizing the mixed solution, and then carrying out aseptic cooling;

(1.3) the concentration is 3.5X 10⁵Adding cfu/mL of acetobacter xylinum original bacterial liquid into the cooled mixed liquid for inoculation, and performing static culture (the temperature of the static culture is 30 ℃ and the time is 14 days) to obtain CNT-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the CNT aqueous dispersion to the HS nutrient solution is 0.72:2.27: 3.01;

(2) preparing CNT-GO-BC hydrogel;

(2.1) respectively preparing GO water dispersion and HS nutrient solution;

the GO water dispersion is obtained by adding GO powder into deionized water, summarizing and uniformly dispersing by ultrasonic waves, wherein the concentration of the GO water dispersion is 5 mg/mL;

(2.2) supplementing and adding HS nutrient solution into a culture dish filled with CNT-BC hydrogel at the bottom, adding GO water dispersion into the HS nutrient solution, sterilizing the mixed solution for 30min, and cooling to 28 ℃ in a sterile manner;

(2.3) the concentration was adjusted to 3.5X 10⁵Adding cfu/mL of acetobacter xylinum stock solution into the cooled mixed solution for inoculation, performing static culture (the temperature of the static culture is 30 ℃ and the time is 14 days), and forming GO-BC hydrogel above the CNT-BC hydrogel to obtain the CNT-GO-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the GO water dispersion to the HS nutrient solution is 0.7:1.51: 3.79;

(4) reduction;

mixing and reacting the CNT-GO-BC hydrogel after post-treatment with the ascorbic acid solution with the concentration of 3 wt% in a mass ratio of 1:15 (the reaction temperature is 60 ℃, and the reaction time is 8h), and washing and purifying with deionized water to obtain the photo-thermal conversion film with heterostructure light trapping enhancement.

The prepared photo-thermal conversion film with heterostructure light trapping enhancement has the light absorption rate of 93.4%, as shown in fig. 2, the photo-thermal conversion film with heterostructure light trapping enhancement is a CNT-rGO-BC hydrogel with a composite layer structure, and consists of a CNT-BC hydrogel with the porosity of 95.2% in the upper layer (the average diameter of the fibers in the CNT-BC hydrogel is 22nm) and a rGO-BC hydrogel with the porosity of 83.5% in the lower layer (the average diameter of the fibers in the rGO-BC hydrogel is 22 nm); the CNT-BC hydrogel consists of BC hydrogel and CNT distributed in the BC hydrogel, and the rGO-BC hydrogel consists of BC hydrogel and rGO distributed in the BC hydrogel; the CNT-BC hydrogel is connected with the rGO-BC hydrogel through a naturally formed BC nanofiber; the thickness of the photo-thermal conversion film with heterostructure light trapping enhancement is 1.5mm, and the thickness ratio of the CNT-BC hydrogel to the rGO-BC hydrogel is 3: 1; the average diameter of CNT in the CNT-BC hydrogel is 5nm, and the average length of CNT is 0.5 μm; the average sheet diameter of rGO in the rGO-BC hydrogel is 0.5 mu m, and the average thickness of the rGO is 1 nm.

FIG. 3 is an infrared test spectrum of a photothermal conversion film with heterostructure light trapping enhancement prepared in example 1, showing characteristic absorptions of BC and CNT, rGO, indicating coexistence of CNT, rGO and BC and significant red shift of O-H stretching vibration peak (1630 cm)^-1) And blue shift of C-O-C stretching vibration peak (1110 cm)^-1) The bonding force BC between them and CNT, rGO in the photo-thermal conversion film are proved.

The seawater evaporation performance of the photothermal conversion film with heterostructure light trapping enhancement prepared in example 1 is shown in the graph of FIG. 4, and the evaporation rate is 1.73kgm^-2h^-1。

Comparative example 1

A method for producing a photothermal conversion film, which is substantially the same as that of example 1, is different only in that the step ofStep (2) and step (4), and the amount of each substance was controlled so that the thickness of the CNT-BC hydrogel was 1.5mm, and the evaporation rate was found to be 1.33kgm by the test in the same manner as in example 1^-2h^-1。

Comparative example 2

A photothermal conversion film was prepared in substantially the same manner as in example 1, except that the step (1) was omitted, and the amounts of the respective substances were controlled so that the thickness of the rGO-BC hydrogel was 1.5mm, and the evaporation rate was found to be 1.41kgm by the same test as in example 1^-2h^-1。

Comparing example 1, comparative example 1, and comparative example 2, it can be seen that the evaporation rate of example 1 is much higher than that of comparative example 1 and comparative example 2.

Fig. 1 shows a schematic diagram of light absorption of the photothermal conversion film of example 1, comparative example 1, and comparative example 2, and it can be seen from the diagram that the two-layer cultivation can reduce the light reflectivity and improve the photothermal performance compared with the single-layer cultivation of one material, because the light reaches the underlying rGO-BC hydrogel (the rGO sheet has a higher specific surface area and a wrinkled surface) through the gaps of the CNT-BC hydrogel of the upper layer (there are very many gaps between the cylindrical single CNTs), and then is reflected back to the CNT-BC hydrogel of the upper layer to achieve secondary reflection or collective scattering in the rGO-BC hydrogel, and the light capture rate is high.

Example 2

The preparation method of the photo-thermal conversion film with the heterostructure light trapping enhancement comprises the following specific steps:

(1) preparing CNT-BC hydrogel;

(1.1) respectively preparing a CNT aqueous dispersion and an HS nutrient solution;

the CNT aqueous dispersion is obtained by adding CNT powder into deionized water and performing ultrasonic dispersion uniformly, wherein the concentration of the CNT aqueous dispersion is 5.5 mg/mL;

the HS nutrient solution is prepared from 50g/L glucose, 5g/L yeast extract, 5g/L peptone and 2g/L Na₂HPO₄、1g/L KH₂PO₄1g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 115 deg.C under 0.25MPa for 35min with an autoclave, and cooling to 26 deg.C under aseptic condition to obtain HS nutrient solution;

(1.2) adding the CNT aqueous dispersion into the HS nutrient solution in a culture dish, sterilizing the mixed solution, and then carrying out aseptic cooling;

(1.3) the concentration was adjusted to 3.6X 10⁵Adding cfu/mL of acetobacter xylinum original bacterial liquid into the cooled mixed liquid for inoculation, and performing static culture (the temperature of the static culture is 29 ℃ and the time is 12 days) to obtain CNT-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the CNT aqueous dispersion to the HS nutrient solution is 0.78:1.43: 3.79;

(2) preparing CNT-GO-BC hydrogel;

(2.1) respectively preparing GO water dispersion and HS nutrient solution;

(2.3) the concentration was adjusted to 3.6X 10⁵Adding cfu/mL of acetobacter xylinum stock solution into the cooled mixed solution for inoculation, performing static culture (the temperature of the static culture is 29 ℃, the time is 12 days), and forming GO-BC water above the CNT-BC hydrogelGelling to obtain CNT-GO-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the GO water dispersion to the HS nutrient solution is 0.78:1.43: 3.79;

(4) reduction;

mixing and reacting the CNT-GO-BC hydrogel after post-treatment with a mass ratio of 1:15 with an ascorbic acid solution with a concentration of 4 wt% (reaction temperature is 65 ℃, reaction time is 7h), and washing and purifying with deionized water to obtain the photo-thermal conversion film with heterostructure light trapping enhancement.

The prepared photo-thermal conversion film with the heterostructure light trapping enhancement has the light absorption rate of 94.8%, the photo-thermal conversion film with the heterostructure light trapping enhancement is a CNT-rGO-BC hydrogel with a composite layer structure, and the photo-thermal conversion film consists of a CNT-BC hydrogel with the porosity of 95.9% at the upper layer (the average diameter of fibers in the CNT-BC hydrogel is 20nm) and an rGO-BC hydrogel with the porosity of 85.1% at the lower layer (the average diameter of fibers in the rGO-BC hydrogel is 24 nm); the CNT-BC hydrogel consists of BC hydrogel and CNT distributed in the BC hydrogel, and the rGO-BC hydrogel consists of BC hydrogel and rGO distributed in the BC hydrogel; the CNT-BC hydrogel is connected with the rGO-BC hydrogel through a naturally formed BC nanofiber; the thickness of the photo-thermal conversion film with heterostructure light trapping enhancement is 1.8mm, and the thickness ratio of the CNT-BC hydrogel to the rGO-BC hydrogel is 3: 1; the average diameter of the CNT in the CNT-BC hydrogel is 7nm, and the average length of the CNT is 0.7 mu m; the average sheet diameter of rGO in the rGO-BC hydrogel is 1 mu m, and the average thickness of the rGO is 1.3 nm.

The seawater evaporation performance of the photo-thermal conversion film with the heterostructure light trapping enhancement is tested, and the evaporation rate is measured to be 1.68kgm^-2h^-1。

Example 3

The preparation method of the photo-thermal conversion film with the heterostructure light trapping enhancement comprises the following specific steps:

(1) preparing CNT-BC hydrogel;

(1.1) respectively preparing a CNT aqueous dispersion and an HS nutrient solution;

the CNT aqueous dispersion is obtained by adding CNT powder into deionized water and performing ultrasonic dispersion uniformly, wherein the concentration of the CNT aqueous dispersion is 6 mg/mL;

the HS nutrient solution is composed of 60g/L glucose, 8g/L yeast extract, 8g/L peptone and 4g/L Na₂HPO₄、2g/L KH₂PO₄2g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 120 deg.C under 0.2MPa for 40min with an autoclave, and cooling to 24 deg.C under aseptic condition to obtain HS nutrient solution;

(1.2) adding the CNT aqueous dispersion into the HS nutrient solution in a culture dish, sterilizing the mixed solution, and then carrying out aseptic cooling;

(1.3) the concentration is 3.7X 10⁵Adding cfu/mL of acetobacter xylinum original bacterial liquid into the cooled mixed liquid for inoculation, and performing static culture (the temperature of the static culture is 28 ℃ and the time is 10 days) to obtain CNT-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the CNT aqueous dispersion to the HS nutrient solution is 0.8:1: 4.2;

(2) preparing CNT-GO-BC hydrogel;

(2.1) respectively preparing GO water dispersion and HS nutrient solution;

(2.3) the concentration was adjusted to 3.7X 10⁵Adding cfu/mL of acetobacter xylinum stock solution into the cooled mixed solution for inoculation, performing static culture (the temperature of the static culture is 28 ℃, and the time is 10 days), and forming GO-BC hydrogel above the CNT-BC hydrogel to obtain the CNT-GO-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the GO water dispersion to the HS nutrient solution is 0.72:2.27: 3.01;

(4) reduction;

mixing and reacting the CNT-GO-BC hydrogel after post-treatment with the ascorbic acid solution with the concentration of 5 wt% according to the mass ratio of 1:15 (the reaction temperature is 70 ℃, and the reaction time is 6h), and washing and purifying with deionized water to obtain the photo-thermal conversion film with heterostructure light trapping enhancement.

The prepared photo-thermal conversion film with the heterostructure light trapping enhancement has the light absorption rate of 93.5%, the photo-thermal conversion film with the heterostructure light trapping enhancement is a CNT-rGO-BC hydrogel with a composite layer structure, and the photo-thermal conversion film consists of a CNT-BC hydrogel with the porosity of 96.4% at the upper layer (the average diameter of fibers in the CNT-BC hydrogel is 25nm) and a rGO-BC hydrogel with the porosity of 84.8% at the lower layer (the average diameter of fibers in the rGO-BC hydrogel is 25 nm); the CNT-BC hydrogel consists of BC hydrogel and CNT distributed in the BC hydrogel, and the rGO-BC hydrogel consists of BC hydrogel and rGO distributed in the BC hydrogel; the CNT-BC hydrogel is connected with the rGO-BC hydrogel through a naturally formed BC nanofiber; the thickness of the photo-thermal conversion film with heterostructure light trapping enhancement is 2mm, and the thickness ratio of the CNT-BC hydrogel to the rGO-BC hydrogel is 3: 1; the average diameter of CNT in the CNT-BC hydrogel is 9nm, and the average length of CNT is 1 μm; the average sheet diameter of rGO in the rGO-BC hydrogel is 1.5 mu m, and the average thickness of the rGO is 1.6 nm.

The seawater evaporation performance of the photo-thermal conversion film with the heterostructure light trapping enhancement is tested, and the evaporation rate is 1.60kgm^-2h^-1。

Example 4

The preparation method of the photo-thermal conversion film with the heterostructure light trapping enhancement comprises the following specific steps:

(1) preparing CNT-BC hydrogel;

(1.1) respectively preparing a CNT aqueous dispersion and an HS nutrient solution;

the CNT aqueous dispersion is obtained by adding CNT powder into deionized water and performing ultrasonic dispersion uniformly, and the concentration of the CNT aqueous dispersion is 6.5 mg/mL;

the HS nutrient solution is composed of 40g/L glucose, 3g/L yeast extract, 3g/L peptone and 1g/L Na₂HPO₄、0.5g/L KH₂PO₄0.5g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 125 deg.C under 0.15MPa for 45min with autoclave, and cooling to 22 deg.C under aseptic condition to obtain HS nutrient solution;

(1.2) adding the CNT aqueous dispersion into the HS nutrient solution in a culture dish, sterilizing the mixed solution, and then carrying out aseptic cooling;

(1.3) the concentration is 3.8X 10⁵Adding cfu/mL of acetobacter xylinum original bacterial liquid into the cooled mixed liquid for inoculation, and performing static culture (the temperature of the static culture is 30 ℃ and the time is 8 days) to obtain CNT-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the CNT aqueous dispersion to the HS nutrient solution is 0.85:0.65: 4.5;

(2) preparing CNT-GO-BC hydrogel;

(2.1) respectively preparing GO water dispersion and HS nutrient solution;

the HS nutrient solution is prepared from 40g/L glucose and 3g/L yeastMother extract, 3g/L peptone, 1g/L Na₂HPO₄、0.5g/L KH₂PO₄0.5g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 125 deg.C under 0.15MPa for 45min with autoclave, and cooling to 22 deg.C under aseptic condition to obtain HS nutrient solution;

(2.3) the concentration was adjusted to 3.8X 10⁵Adding cfu/mL of acetobacter xylinum stock solution into the cooled mixed solution for inoculation, performing static culture (the temperature of the static culture is 30 ℃ and the time is 8 days), and forming GO-BC hydrogel above the CNT-BC hydrogel to obtain the CNT-GO-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the GO water dispersion to the HS nutrient solution is 0.82:0.96: 4.22;

(4) reduction;

mixing and reacting the CNT-GO-BC hydrogel after post-treatment with the ascorbic acid solution with the concentration of 6 wt% in a mass ratio of 1:15 (the reaction temperature is 75 ℃, and the reaction time is 8h), and washing and purifying with deionized water to obtain the photo-thermal conversion film with heterostructure light trapping enhancement.

The prepared photo-thermal conversion film with the heterostructure light trapping enhancement has the light absorption rate of 94.2 percent, is a CNT-rGO-BC hydrogel with a composite layer structure, and consists of a CNT-BC hydrogel with the porosity of 97.1 percent at the upper layer (the average diameter of fibers in the CNT-BC hydrogel is 30nm) and a rGO-BC hydrogel with the porosity of 86 percent at the lower layer (the average diameter of fibers in the rGO-BC hydrogel is 28 nm); the CNT-BC hydrogel consists of BC hydrogel and CNT distributed in the BC hydrogel, and the rGO-BC hydrogel consists of BC hydrogel and rGO distributed in the BC hydrogel; the CNT-BC hydrogel is connected with the rGO-BC hydrogel through a naturally formed BC nanofiber; the thickness of the photo-thermal conversion film with heterostructure light trapping enhancement is 2mm, and the thickness ratio of the CNT-BC hydrogel to the rGO-BC hydrogel is 3: 1; the average diameter of CNT in the CNT-BC hydrogel is 11nm, and the average length of CNT is 1.3 μm; the average sheet diameter of rGO in the rGO-BC hydrogel is 2 mu m, and the average thickness of the rGO is 2 nm.

The seawater evaporation performance of the photo-thermal conversion film with the heterostructure light trapping enhancement is tested, and the evaporation rate is 1.62kgm^-2h^-1。

Example 5

The preparation method of the photo-thermal conversion film with the heterostructure light trapping enhancement comprises the following specific steps:

(1) preparing CNT-BC hydrogel;

(1.1) respectively preparing a CNT aqueous dispersion and an HS nutrient solution;

the CNT aqueous dispersion is obtained by adding CNT powder into deionized water and performing ultrasonic dispersion uniformly, wherein the concentration of the CNT aqueous dispersion is 7 mg/mL;

the HS nutrient solution is prepared from 50g/L glucose, 5g/L yeast extract, 5g/L peptone and 2g/L Na₂HPO₄、1g/L KH₂PO₄1g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 130 deg.C under 0.1MPa for 50min with an autoclave, and cooling to 20 deg.C under aseptic condition to obtain HS nutrient solution;

(1.2) adding the CNT aqueous dispersion into the HS nutrient solution in a culture dish, sterilizing the mixed solution, and then carrying out aseptic cooling;

(1.3) the concentration was adjusted to 3.9X 10⁵Adding cfu/mL of acetobacter xylinum stock solution into the cooled mixed solution for inoculation, and performing static culture (the temperature of the static culture is 29 ℃ and the time is 7 days) to obtain the CNT-BC hydrogelGluing; the volume ratio of the acetobacter xylinum raw bacterium liquid to the CNT aqueous dispersion to the HS nutrient solution is 0.78:2.1: 3.12;

(2) preparing CNT-GO-BC hydrogel;

(2.1) respectively preparing GO water dispersion and HS nutrient solution;

the GO water dispersion is obtained by adding GO powder into deionized water, summarizing and ultrasonically dispersing uniformly, and the concentration of the GO water dispersion is 7 mg/mL;

the HS nutrient solution is prepared from 50g/L glucose, 5g/L yeast extract, 5g/L peptone and 2g/L Na₂HPO₄、1g/L KH₂PO₄1g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 130 deg.C under 0.1MPa for 50min with an autoclave, and cooling to 20 deg.C under aseptic condition to obtain HS nutrient solution;

(2.3) the concentration was adjusted to 3.9X 10⁵Adding cfu/mL of acetobacter xylinum stock solution into the cooled mixed solution for inoculation, performing static culture (the temperature of the static culture is 29 ℃ and the time is 7 days), and forming GO-BC hydrogel above the CNT-BC hydrogel to obtain the CNT-GO-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the GO water dispersion to the HS nutrient solution is 0.78:2.1: 3.12;

(4) reduction;

mixing and reacting the CNT-GO-BC hydrogel after post-treatment with an ascorbic acid solution with the concentration of 7 wt% in a mass ratio of 1:15 (the reaction temperature is 80 ℃, and the reaction time is 7h), and washing and purifying with deionized water to obtain the photo-thermal conversion film with heterostructure light trapping enhancement.

The prepared photo-thermal conversion film with the heterostructure light trapping enhancement has the light absorption rate of 95.5%, the photo-thermal conversion film with the heterostructure light trapping enhancement is a CNT-rGO-BC hydrogel with a composite layer structure, and the photo-thermal conversion film consists of a CNT-BC hydrogel with the porosity of 97.8% at the upper layer (the average diameter of fibers in the CNT-BC hydrogel is 28nm) and a rGO-BC hydrogel with the porosity of 84.2% at the lower layer (the average diameter of fibers in the rGO-BC hydrogel is 30 nm); the CNT-BC hydrogel consists of BC hydrogel and CNT distributed in the BC hydrogel, and the rGO-BC hydrogel consists of BC hydrogel and rGO distributed in the BC hydrogel; the CNT-BC hydrogel is connected with the rGO-BC hydrogel through a naturally formed BC nanofiber; the thickness of the photo-thermal conversion film with heterostructure light trapping enhancement is 2.2mm, and the thickness ratio of the CNT-BC hydrogel to the rGO-BC hydrogel is 3: 1; the average diameter of the CNT in the CNT-BC hydrogel is 13nm, and the average length of the CNT is 1.6 mu m; the average sheet diameter of rGO in the rGO-BC hydrogel is 3 mu m, and the average thickness of the rGO is 2.3 nm.

The seawater evaporation performance of the photo-thermal conversion film with the heterostructure light trapping enhancement is tested, and the evaporation rate is 1.70kgm^-2h^-1。

Example 6

The preparation method of the photo-thermal conversion film with the heterostructure light trapping enhancement comprises the following specific steps:

(1) preparing CNT-BC hydrogel;

(1.1) respectively preparing a CNT aqueous dispersion and an HS nutrient solution;

the CNT aqueous dispersion is obtained by adding CNT powder into deionized water and performing ultrasonic dispersion uniformly, and the concentration of the CNT aqueous dispersion is 7.5 mg/mL;

the HS nutrient solution is composed of 60g/L glucose, 8g/L yeast extract, 8g/L peptone and 4g/L Na₂HPO₄、2g/L KH₂PO₄2g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, and making into strip at 125 deg.C and 0.15MPaSterilizing the mixture for 45min at high temperature by using an autoclave under the condition of parts, and carrying out aseptic cooling to 22 ℃ to obtain HS nutrient solution;

(1.2) adding the CNT aqueous dispersion into the HS nutrient solution in a culture dish, sterilizing the mixed solution, and then carrying out aseptic cooling;

(1.3) the concentration is 4X 10⁵Adding cfu/mL of acetobacter xylinum original bacterial liquid into the cooled mixed liquid for inoculation, and performing static culture (the temperature of the static culture is 28 ℃ and the time is 12 days) to obtain CNT-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the CNT aqueous dispersion to the HS nutrient solution is 0.81:1.78: 3.41;

(2) preparing CNT-GO-BC hydrogel;

(2.1) respectively preparing GO water dispersion and HS nutrient solution;

the HS nutrient solution is composed of 60g/L glucose, 8g/L yeast extract, 8g/L peptone and 4g/L Na₂HPO₄、2g/L KH₂PO₄2g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 125 deg.C under 0.15MPa for 45min with autoclave, and cooling to 22 deg.C under aseptic condition to obtain HS nutrient solution;

(2.3) the concentration was adjusted to 4X 10⁵Adding cfu/mL of acetobacter xylinum stock solution into the cooled mixed solution for inoculation, performing static culture (the temperature of the static culture is 28 ℃, and the time is 12 days), and forming GO-BC hydrogel above the CNT-BC hydrogel to obtain the CNT-GO-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the GO water dispersion to the HS nutrient solution is 0.73:1.19: 4.08;

(4) reduction;

mixing and reacting the CNT-GO-BC hydrogel after post-treatment with an ascorbic acid solution with the concentration of 8 wt% in a mass ratio of 1:15 (the reaction temperature is 75 ℃, and the reaction time is 6h), and washing and purifying with deionized water to obtain the photo-thermal conversion film with heterostructure light trapping enhancement.

The prepared photo-thermal conversion film with the heterostructure light trapping enhancement has the light absorption rate of 94.8%, the photo-thermal conversion film with the heterostructure light trapping enhancement is a CNT-rGO-BC hydrogel with a composite layer structure, and the photo-thermal conversion film consists of a CNT-BC hydrogel with the porosity of 96.5% at the upper layer (the average diameter of fibers in the CNT-BC hydrogel is 24nm) and an rGO-BC hydrogel with the porosity of 85.7% at the lower layer (the average diameter of fibers in the rGO-BC hydrogel is 26 nm); the CNT-BC hydrogel consists of BC hydrogel and CNT distributed in the BC hydrogel, and the rGO-BC hydrogel consists of BC hydrogel and rGO distributed in the BC hydrogel; the CNT-BC hydrogel is connected with the rGO-BC hydrogel through a naturally formed BC nanofiber; the thickness of the photo-thermal conversion film with heterostructure light trapping enhancement is 2.4mm, and the thickness ratio of the CNT-BC hydrogel to the rGO-BC hydrogel is 3: 1; the average diameter of CNT in the CNT-BC hydrogel is 14nm, and the average length of CNT is 1.9 μm; the average sheet diameter of rGO in the rGO-BC hydrogel is 4 mu m, and the average thickness of the rGO is 2.7 nm.

The seawater evaporation performance of the photo-thermal conversion film with the heterostructure light trapping enhancement is tested, and the evaporation rate is 1.65kgm^-2h^-1。

Example 7

The preparation method of the photo-thermal conversion film with the heterostructure light trapping enhancement comprises the following specific steps:

(1) preparing CNT-BC hydrogel;

(1.1) respectively preparing a CNT aqueous dispersion and an HS nutrient solution;

the CNT aqueous dispersion is obtained by adding CNT powder into deionized water and performing ultrasonic dispersion uniformly, wherein the concentration of the CNT aqueous dispersion is 8 mg/mL;

the HS nutrient solution is composed of 40g/L glucose, 3g/L yeast extract, 3g/L peptone and 1g/L Na₂HPO₄、0.5g/L KH₂PO₄0.5g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 130 deg.C under 0.1MPa for 50min with an autoclave, and cooling to 20 deg.C under aseptic condition to obtain HS nutrient solution;

(1.2) adding the CNT aqueous dispersion into the HS nutrient solution in a culture dish, sterilizing the mixed solution, and then carrying out aseptic cooling;

(1.3) the concentration is 4X 10⁵Adding cfu/mL of acetobacter xylinum original bacterial liquid into the cooled mixed liquid for inoculation, and performing static culture (the temperature of the static culture is 30 ℃ and the time is 10 days) to obtain CNT-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the CNT aqueous dispersion to the HS nutrient solution is 0.83:1.82: 3.35;

(2) preparing CNT-GO-BC hydrogel;

(2.1) respectively preparing GO water dispersion and HS nutrient solution;

the GO water dispersion is obtained by adding GO powder into deionized water, summarizing and ultrasonically dispersing uniformly, wherein the concentration of the GO water dispersion is 8 mg/mL;

the HS nutrient solution is composed of 40g/L glucose, 3g/L yeast extract, 3g/L peptone and 1g/L Na₂HPO₄、0.5g/L KH₂PO₄0.5g/L citric acid and the balance of ultrapure water; the preparation process of the HS nutrient solution comprises the following steps: proportionally mixing glucose, yeast extract, peptone and Na₂HPO₄、KH₂PO₄Adding citric acid into ultrapure water, stirring, sterilizing at 130 deg.C under 0.1MPa for 50min with an autoclave, and cooling to 20 deg.C under aseptic condition to obtain HS nutrient solution;

(2.3) the concentration was adjusted to 4X 10⁵Adding cfu/mL of acetobacter xylinum stock solution into the cooled mixed solution for inoculation, performing static culture (the temperature of the static culture is 30 ℃ and the time is 10 days), and forming GO-BC hydrogel above the CNT-BC hydrogel to obtain the CNT-GO-BC hydrogel; the volume ratio of the acetobacter xylinum raw bacterium liquid to the GO water dispersion to the HS nutrient solution is 0.75:1.21: 4.04;

(4) reduction;

mixing and reacting the CNT-GO-BC hydrogel after post-treatment with the weight ratio of 1:15 with an ascorbic acid solution with the concentration of 10 wt% (the reaction temperature is 80 ℃, and the reaction time is 8h), and washing and purifying with deionized water to obtain the photo-thermal conversion film with heterostructure light trapping enhancement.

The prepared photo-thermal conversion film with the heterostructure light trapping enhancement has the light absorption rate of 95.1 percent, is a CNT-rGO-BC hydrogel with a composite layer structure, and consists of a CNT-BC hydrogel with the porosity of 97.5 percent at the upper layer (the average diameter of fibers in the CNT-BC hydrogel is 25nm) and a rGO-BC hydrogel with the porosity of 84.7 percent at the lower layer (the average diameter of fibers in the rGO-BC hydrogel is 22 nm); the CNT-BC hydrogel consists of BC hydrogel and CNT distributed in the BC hydrogel, and the rGO-BC hydrogel consists of BC hydrogel and rGO distributed in the BC hydrogel; the CNT-BC hydrogel is connected with the rGO-BC hydrogel through a naturally formed BC nanofiber; the thickness of the photo-thermal conversion film with heterostructure light trapping enhancement is 2.5mm, and the thickness ratio of the CNT-BC hydrogel to the rGO-BC hydrogel is 3: 1; the average diameter of the CNT in the CNT-BC hydrogel is 15nm, and the average length of the CNT is 2 mu m; the average sheet diameter of the rGO in the rGO-BC hydrogel is 5 mu m, and the average thickness of the rGO is 3 nm.

The seawater evaporation performance of the photo-thermal conversion film with the heterostructure light trapping enhancement is tested, and the evaporation rate is measured to be 1.69kgm^-2h^-1。

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