Application of cellulose / graphene oxide composite membrane in osmotic power generation

Abstract

The application discloses application of a cellulose / graphene oxide composite membrane in osmotic power generation. The cellulose / graphene oxide composite membrane is used as a diaphragm material, and chemical energy is converted into electric energy by using salt difference or acid difference of an electrolyte. The graphene oxide nanosheet with a two-dimensional sheet structure is filled into soft cellulose, so that a stable frame structure is formed, the interface connection between the graphene oxide nanosheets is greatly improved, the cellulose cation selectivity is enhanced, the interlayer space for fast ion transmission is expanded, and ion transmission of surface charge regulation is facilitated.

Description

Technical Field

[0001] This invention relates to the field of membrane technology. More specifically, it relates to the application of a cellulose / graphene oxide composite membrane in osmotic power generation. Background Technology

[0002] Energy is fundamental to human survival in today's society. However, most of the energy used globally currently comes from traditional fossil fuels such as oil, coal, and natural gas. The ever-increasing consumption of fossil fuels is facing the risk of depletion. While new renewable energy sources such as wind, hydro, nuclear, solar, and geothermal energy are clean and renewable, their practical applications are affected by geographical and climatic factors, and their power generation is intermittent and unstable—issues that are difficult to overcome. H + It has more than Na + Higher permeability energy, as a novel renewable energy source, produces no waste, emits no carbon dioxide, and is not limited by weather or location. Its principle is to generate electricity by exploiting the potential difference between solutions of different concentrations. In recent years, researchers have turned their attention to salinity gradient energy within permeability energy. Salinity gradient energy, a potentially huge and untapped clean energy source existing between seawater and river water, can be utilized by adding high-performance membrane materials (such as nanoscale monopore and porous materials) to improve ion transport and facilitate the capture of blue energy from the ion gradient. Patent CN103615363A discloses a salinity gradient energy power generation device and method. This device uses multiple permeable membrane elements connected in parallel to separate the high-concentration side and low-concentration layer of seawater, then converts the osmotic pressure difference into hydrostatic pressure on the high-concentration side to drive the generator. However, the harvesting of permeability energy from industrial wastewater has been largely neglected. Industrial wastewater is often acidic and rich in H₂. + The transfer number of , its mobility is greater than that of Na + The permeation energy of industrial wastewater is on the order of magnitude larger. If this energy could be fully utilized, it would undoubtedly have a significant impact on energy replenishment. However, on the one hand, current membrane materials suffer from poor acid resistance, easily altered spatial structures, and easily damaged ion transport nanochannels, resulting in low stability. For example, two-dimensional layered graphene oxide can be used as a nanolaminated membrane. Graphene oxide nanosheets, due to their large slip length, enable rapid diffusion of water molecules. However, the swelling of current graphene oxide membranes limits their porosity control, greatly hindering their ion transport behavior and ultimately leading to irreversible degradation. On the other hand, membrane materials exhibit low output performance when using acid gradients for permeation power generation. Therefore, researching a membrane material with good mechanical stability, acid resistance, and high ion transport efficiency for application in the field of permeation power generation is particularly important for better utilization of permeation energy. Summary of the Invention

[0003] To address the aforementioned shortcomings, the present invention aims to provide an application of a cellulose / graphene oxide composite membrane in osmotic power generation. The stable framework structure formed by the cellulose / graphene oxide composite membrane enables the construction of nanochannels with high surface charge, achieving surface charge-regulated ion transport, which is beneficial for further improving energy conversion capacity and acid resistance.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This invention provides an application of a cellulose / graphene oxide composite membrane in osmotic power generation, using the cellulose / graphene oxide composite membrane as the membrane material, and utilizing the salt difference or acid difference of the electrolyte to convert chemical energy into electrical energy.

[0006] This application uses soft lignocellulose (CNFs) as a substrate and incorporates two-dimensional sheet-like graphene oxide (GOMs) into the lignocellulose tissue to form a stable framework structure. This greatly improves the interfacial connections between graphene oxides, expands the interlayer space for rapid ion transport, and is beneficial for ion transport regulated by surface charge.

[0007] According to the inventors' research, composite membranes prepared by mixing one-dimensional and two-dimensional sheet materials can be applied to permeation power generation technology. The one-dimensional materials include nanowires (such as cellulose), carbon nanotubes, and nanospheres, while the two-dimensional sheet materials include MXene (such as graphene oxide), MoS2, and WS2. However, the inventors have selected a composite membrane material combination exhibiting a more pronounced synergistic relationship: cellulose and graphene oxide. This synergistic relationship is manifested in two ways: firstly, cellulose possesses a cross-linked network structure rich in surface and space charges, which endows the composite membrane with good cation selectivity and provides binding sites for various functional groups of graphene oxide; secondly, the van der Waals forces and hydrogen bonds between cellulose and graphene oxide result in a relatively stable structure, which helps prevent changes in the interlayer space caused by the swelling of graphene oxide.

[0008] In this field, two-dimensional sheet materials such as graphene oxide are often used as the main material, combined with other materials in composite design. This application, however, uses cellulose as the main material, doped with a small amount of graphene oxide. Its advantage lies in the abundant surface and spacing charges of the cross-linked network formed by CNFs, providing various functional groups for bonding with GOMs. Compared with traditional GOM membranes with unstable interlayer spacing, the introduction of CNFs, a natural biomaterial with stable interlayer spacing, forms strong hydrogen bond interactions with GOMs, exhibiting controllable ion transport. Furthermore, this composite membrane has a high proportion of natural biomaterial CNFs, which can resist the erosion of acidic solutions and shows potential for energy conversion under extreme conditions. This special structure formed by the combination of raw materials endows it with excellent chemical elasticity, rapid selective ion transport capability, and acid resistance, which is beneficial for further enhancing energy conversion characteristics. In reverse osmosis power generation applications, based on the principle of reverse osmosis, cations can pass through the composite membrane, while anions are blocked in concentrated salt or acid solutions. This forms a directional movement of charges, generating current and realizing the conversion of salt gradient energy and acid gradient energy into electrical energy.

[0009] Furthermore, the cellulose / graphene oxide composite membrane is a uniform and transparent film with a two-dimensional sheet structure, a thickness of 4–6 μm, and a single-layer spacing of 0.9–1.2 nm, which is much larger than the 0.72 nm spacing of GOMs. Due to the abundant CNFs between GOMs, the CNFs with a large surface charge impart a space charge effect between the GOM nanofilms, greatly increasing the surface charge of the composite membrane and enabling efficient and rapid ion transmembrane transport and enhanced cation selectivity.

[0010] Furthermore, the cellulose / graphene oxide composite membrane is made by doping cellulose with 1-20 wt% graphene oxide dispersion. Within this range, the interlayer gap between cellulose nanofibers is increased due to the intercalation of graphene oxide, which helps to increase the ion flow along the two-dimensional nanochannels. If the doping amount of graphene oxide dispersion is less than 1 wt%, it cannot support the interlayer structure of cellulose and it is difficult to form a stable framework structure. When the doping amount of graphene oxide dispersion is greater than 20 wt%, the excessive graphene oxide will lead to weakened interlayer strength and poor ion selectivity, which is detrimental to the conversion of permeation energy. For example, the doping amount of the graphene oxide dispersion can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, or any range formed by any two of these values. In one specific embodiment, the doping amount of the graphene oxide dispersion is 10 wt%, achieving maximum ion selectivity and ion flux. The graphene oxide dispersion has a concentration of 2 mg / mL.

[0011] Furthermore, when utilizing the salinity gradient of the electrolyte for osmotic power generation, an Ag / AgCl electrode is used to apply the transmembrane potential. The concentration gradient between the concentrated and dilute salt solutions is 5-500 times, with an external load resistor of 0-1000KΩ. The electrode material can also be a titanium-based iridium-coated electrode or a titanium-based ruthenium-coated electrode; the concentration gradient between the concentrated and dilute salt solutions can also be 50, 100, 150, 200, 250, 300, 350, 400, 450 times, or any range thereof. In practical applications, the sodium chloride concentration in artificial seawater is 0.5M, and the sodium chloride concentration in river water is 0.01M. The naturally formed salinity gradient system has a concentration gradient of 50 times, which is the longest investigated and studied concentration gradient in this field. In the salinity gradient system, the external load resistor is preferably 20KΩ.

[0012] Regarding the selection of the external resistor, the resistance can be 0, i.e., to obtain the short-circuit current. Other possible resistance values ​​include 100Ω, 300Ω, 500Ω, 1000Ω, 3000Ω, 5000Ω, 7000Ω, 10000Ω, 13000Ω, 17000Ω, 20000Ω, 23000Ω, 27000Ω, 30000Ω, 33000Ω, 37000Ω, 40000Ω, 50000Ω, 60000Ω, 70000Ω, 80000Ω, 100000Ω, 150000Ω, 220000Ω, 500000Ω, and 1000000Ω. Experiments have shown that in the salt gradient system, the resistance value corresponding to the optimal power density is basically consistent at 20KΩ for different salt systems and concentration gradients. However, this is different for the acid gradient system; the resistance value varies depending on the acid system and concentration gradient. Different concentration gradients affect the resistance value corresponding to the optimal power density. For hydrochloric acid solutions, the resistance value corresponding to the optimal power density is 1000 Ω at a concentration gradient of 5 times and 10 times, 3000 Ω at a concentration gradient of 50 times and 100 times, 5000 Ω at a concentration gradient of 500 times, and 13 kΩ at a concentration gradient of 1000 times. For other acid systems, when the concentration gradient is 1000 times, the resistance value corresponding to the optimal power density is 27 kΩ in sulfuric acid, 17 kΩ in oxalic acid, 40 kΩ in phosphoric acid, 150 kΩ in formic acid, and 220 kΩ in acetic acid.

[0013] Furthermore, the concentration of the concentrated salt solution is 0.5M, and the concentration of the dilute salt solution is 0.001-0.1M. Preferably, the concentration of the dilute salt solution can also be within the range formed by any two values, such as 0.005M, 0.01M, 0.02M, 0.05M, and 0.08M, and the salt solution is selected from lithium chloride solution, sodium chloride solution, potassium chloride solution, magnesium chloride solution, or calcium chloride solution; preferably, the type of salt in the concentrated salt solution and the dilute salt solution is the same.

[0014] In one specific embodiment, the electrolyte is replaced with an acid solution. This serves two purposes: firstly, to verify the acid resistance of the composite membrane, and secondly, to utilize the acid gradient for permeation power generation. An Ag / AgCl electrode is selected, with a concentration gradient of 5-1000 times between the concentrated and dilute acid solutions, and an external load resistor of 0-1000KΩ is connected. Similarly, the electrode material can also be a titanium-based iridium-coated electrode or a titanium-based ruthenium-coated electrode; the concentration gradient between the concentrated and dilute acid solutions can also be 10 times, 50 times, 100 times, 150 times, 200 times, 250 times, 300 times, 350 times, 400 times, 450 times, 500 times, 550 times, 600 times, 650 times, 700 times, 750 times, 800 times, 850 times, 900 times, 950 times, etc., or any range thereof.

[0015] Furthermore, the concentration of the concentrated acid solution is 0.5M, and the concentration of the dilute acid solution is 0.5-100mM. The acid solution can be selected from completely ionized acids or incompletely ionized acids, such as hydrochloric acid solution, sulfuric acid solution, oxalic acid solution, phosphoric acid solution, formic acid solution, or acetic acid solution, etc.; preferably, the concentrated acid solution and the dilute acid solution are of the same type of acid.

[0016] Furthermore, the cellulose / graphene oxide composite membrane is prepared by the following method:

[0017] Cellulose is dissolved in water, then mixed with graphene oxide dispersion in a certain proportion, sonicated for 15-30 minutes, filtered through a PC filter membrane, dried, and then peeled off from the PC filter membrane to obtain the final product.

[0018] Furthermore, the cellulose is doped with 1-20 wt% of graphene oxide dispersion.

[0019] The beneficial effects of this invention are as follows:

[0020] This invention discloses the application of a cellulose / graphene oxide composite membrane in osmotic power generation. The invention uses a self-made cellulose / graphene oxide composite membrane as the membrane material, utilizing the salt or acid gradient of the electrolyte to convert chemical energy into electrical energy. By doping graphene oxide nanosheets with a two-dimensional layered structure into soft cellulose, a stable framework structure is formed. This not only greatly improves the interfacial bonding between the graphene oxide nanosheets and enhances the cation selectivity of cellulose, but also expands the interlayer space for rapid ion transport, which is beneficial for surface charge-controlled ion transport. When the doping amount of graphene oxide dispersion is 10 wt%, the load resistance is 20 kΩ, and the concentration gradient between the concentrated and dilute sodium chloride solution is 50 times, the output power density reaches 5.26 W / m³. -2 When potassium chloride solution is used instead, the output power density can reach 6.07 W / m³. -2When using an acid gradient system, with a concentration gradient of 100 times between the concentrated and dilute hydrochloric acid solutions, the load resistance is 3000Ω, and the output power density reaches 67.08W / m². -2 All far exceed 5W M -2 The level of the commodity film. Attached Figure Description

[0021] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0022] Figure 1 The XRD patterns of the samples prepared in Examples 1-7 of this invention are shown.

[0023] Among them, (a) is the XRD pattern of Example 3, Example 6 and Example 7, and (b) is the XRD pattern of Example 1-6.

[0024] Figure 2 A schematic diagram of the permeable energy power generation device used in the energy conversion test of this invention is shown;

[0025] Figure 3 The diagram shows the salinity gradient power generation performance of the cellulose / graphene oxide composite membrane prepared in Example 3 of this invention.

[0026] Figure 4 This diagram shows a comparison of output power densities with different graphene oxide doping levels in Example 10 of the present invention.

[0027] Figure 5 This diagram shows a comparison of output power density under different types of chloride electrolyte environments in Example 11 of the present invention.

[0028] Figure 6 This diagram shows a comparison of output power densities under different acid concentration gradients in Example 13 of the present invention.

[0029] Figure 7 The stability test diagram of the cellulose / graphene oxide composite membrane of Example 3 of the present invention is shown.

[0030] Figure 8 The image shown is an electron microscope image obtained after a stability test in Embodiment 3 of the present invention.

[0031] Figure 9 The illustration shows a comparison of physical images of film materials with different doping amounts in Embodiment 16 of the present invention. Detailed Implementation

[0032] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further explains the invention. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0033] This invention provides a membrane material that can be prepared on a large scale, is low in cost, has a simple process, and has good acid resistance. A cellulose / graphene oxide composite membrane is prepared by doping 1-20 wt% graphene oxide dispersion with cellulose as the main body. The cellulose / graphene oxide composite membrane is then used in a salt gradient / acid gradient system for performance testing.

[0034] Example 1

[0035] Preparation of cellulose / graphene oxide composite films with a doping concentration of 1 wt% graphene oxide dispersion:

[0036] Cellulose nanofibers were dissolved in deionized water, and 1 wt% graphene oxide dispersion was added. The mixture was stirred and stirred. The solution was sonicated for 20 minutes to form a homogeneous suspension. Then, vacuum-assisted filtration was performed through a PC membrane (47 mm diameter, 0.2 μm pore size) for 12 hours. After air drying, the filtered membrane was removed from the PC membrane to obtain a cellulose / graphene oxide composite membrane with a doping concentration of 1 wt%. Its XRD pattern is shown below. Figure 1 The interlayer spacing is approximately 0.9 nm.

[0037] Example 2

[0038] Preparation of cellulose / graphene oxide composite films with a doping concentration of 5 wt% graphene oxide dispersion:

[0039] Cellulose nanofibers were dissolved in deionized water, and 5 wt% graphene oxide dispersion was added. The mixture was stirred and stirred. The solution was sonicated for 20 minutes to form a homogeneous suspension. Then, vacuum-assisted filtration was performed through a PC membrane (47 mm diameter, 0.2 μm pore size) for 12 hours. After air drying, the filtered membrane was removed from the PC membrane to obtain a cellulose / graphene oxide composite membrane with a doping concentration of 5 wt%. Its XRD pattern is shown in [reference needed]. Figure 1 The interlayer spacing is approximately 1.0 nm.

[0040] Example 3

[0041] Preparation of cellulose / graphene oxide composite films with a doping concentration of 10 wt% graphene oxide dispersion:

[0042] Cellulose nanofibers were dissolved in deionized water, and 10 wt% graphene oxide dispersion was added. The mixture was stirred and stirred. The solution was sonicated for 20 minutes to form a homogeneous suspension. Then, vacuum-assisted filtration was performed through a PC membrane (47 mm diameter, 0.2 μm pore size) for 12 hours. After air drying, the filtered membrane was removed from the PC membrane to obtain a cellulose / graphene oxide composite membrane with a doping concentration of 10 wt%. Its XRD pattern is shown in [reference needed]. Figure 1 The interlayer spacing is approximately 1.2 nm.

[0043] Example 4

[0044] Preparation of cellulose / graphene oxide composite films with a doping concentration of 15 wt% graphene oxide dispersion:

[0045] Cellulose nanofibers were dissolved in deionized water, and 15 wt% graphene oxide dispersion was added. The mixture was stirred and stirred. The solution was sonicated for 20 minutes to form a homogeneous suspension. Then, vacuum-assisted filtration was performed through a PC membrane (47 mm diameter, 0.2 μm pore size) for 12 hours. After air drying, the filtered membrane was removed from the PC membrane to obtain a cellulose / graphene oxide composite membrane with a doping concentration of 15 wt%. Its XRD pattern is shown below. Figure 1 The interlayer spacing is approximately 1.1 nm.

[0046] Example 5

[0047] Preparation of cellulose / graphene oxide composite films with a doping concentration of 20 wt% graphene oxide dispersion:

[0048] Cellulose nanofibers were dissolved in deionized water, and 20 wt% graphene oxide dispersion was added. The mixture was stirred and stirred. The solution was sonicated for 20 minutes to form a homogeneous suspension. Then, vacuum-assisted filtration was performed through a PC membrane (47 mm diameter, 0.2 μm pore size) for 12 hours. After air drying, the filtered membrane was removed from the PC membrane to obtain a cellulose / graphene oxide composite membrane with a doping concentration of 5 wt%. Its XRD pattern is shown below. Figure 1 The interlayer spacing is approximately 1.0 nm.

[0049] Example 6

[0050] Preparation of pure cellulose membranes:

[0051] Cellulose nanofibers were dissolved in deionized water and sonicated for 20 minutes. Then, the solution was vacuum-assisted filtration through a PC filter membrane (47 mm in diameter, 0.2 μm in pore size) for 12 hours. After air drying, the filtered membrane was removed from the PC filter membrane to obtain the cellulose membrane.

[0052] Example 7

[0053] Preparation of pure graphene oxide films:

[0054] One part of graphene oxide dispersion was mixed with one part of deionized water, stirred thoroughly, and sonicated for 20 minutes. Then, it was vacuum-assisted filtered through a PC filter membrane (47 mm in diameter, 0.2 μm in pore size) for 12 hours. After air drying, the filtered membrane was removed from the PC filter membrane to obtain a graphene oxide membrane with an interlayer spacing of 0.72 nm.

[0055] Example 8

[0056] Test methods for converting salinity gradient energy into electrical energy:

[0057] like Figure 2 As shown, the device for converting salinity gradient energy into electrical energy is a closed system. The container on the right contains a concentrated salt solution, while the container on the left contains a dilute salt solution. Unless otherwise specified, the salt types in the concentrated and dilute solutions are consistent throughout the following examples. Each container has a recess for injecting the solution and inserting an Ag / AgCl electrode. The diaphragm material prepared in Examples 1-7 is installed between the two containers and secured with screws. The two solutions are connected in a circuit via an external ammeter and a load resistor to perform salinity gradient energy conversion tests.

[0058] Example 9

[0059] This embodiment is a test of converting salinity gradient energy into electrical energy under different concentration gradient conditions.

[0060] The composite membrane prepared in Example 3 was used as the diaphragm material. The installation method was the same as in Example 8. Sodium chloride solution was selected as the salt solution. First, it was necessary to determine the optimal external resistance value of the composite membrane under the salinity gradient system. The resistance value in the range of 0.1-100KΩ was tested at concentration gradients of 5, 50, and 500 times between the concentrated and dilute solutions. The results are shown in […]. Figure 3 It was found that when the external resistor value was 20KΩ in the salinity gradient system, the power density remained at a high level under different concentration gradients. Therefore, the final value of the external resistor was determined to be 20KΩ. Table 1 shows the test data results under different concentration gradients. As shown in Table 1, the obtained power density increased synchronously with the concentration gradient. When the concentration gradient reached 50 times, it was already higher than the commercial benchmark (5W M). -2 If the concentration is further increased, the power density will not change significantly.

[0061] Table 1 Summary of test data under different concentration gradients

[0062] Concentration gradient 5 times 50 times 500 times <![CDATA[Power density (W m -2 )]]> 2.1 5.26 5.69

[0063] Example 10

[0064] This embodiment examines the effect of graphene oxide dispersions with different doping amounts on the output power density of the composite membrane.

[0065] The composite membranes prepared in Examples 1-6 were selected as the membrane material. The installation method was the same as in Example 8. Sodium chloride solution was selected as the salt solution. The external load resistance was controlled at 20 kΩ. The concentration gradient between the concentrated and dilute solutions was 50 times. The results are shown in Table 2 and 3. Figure 4 Table 2 shows that the power density of the composite film doped with graphene oxide is higher than that of the undoped film. The power density first increases and then decreases with the increase of the doping amount of graphene oxide dispersion, reaching the maximum at a doping amount of 10 wt%. This is because graphene oxide increases the interlayer gap of cellulose, which helps to increase the ion flow along the two-dimensional nanochannel. However, when the doping amount is greater than 10 wt%, graphene oxide begins to affect the interlayer strength and the ion selectivity, which is not conducive to the conversion of permeation energy.

[0066] Table 2 Summary of test data for graphene oxide dispersions with different doping concentrations

[0067] Test sample Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 <![CDATA[Power density (W m -2 )]]> 3.32 4.31 5.26 4.57 3.86 2.71

[0068] Example 11

[0069] This embodiment examines the output power density of the composite membrane in different types of chloride salt solutions.

[0070] The composite membrane prepared in Example 3 was selected as the membrane material. The installation method was the same as in Example 8. Lithium chloride, sodium chloride, potassium chloride, magnesium chloride, and calcium chloride were selected as electrolyte solutions. The external load resistance was controlled at 20 kΩ, and the concentration gradient between the concentrated and dilute solutions was 50 times. The results are shown in Table 3 and [Table data missing]. Figure 5 The results showed that the power density was highest at 6.07 W / m³ when the salt solution was potassium chloride. -2 This is because the difference in output power density is related to the diffusion coefficient. The order of ion diffusion coefficients is K. + >Na + >Li + >Ca 2+ >Mg 2+ K + The diffusion coefficient is the highest, and the order of the hydration radii of the five cations is K. + <Na + <Li + <Ca 2+ <Mg 2+ A smaller hydration radius also leads to a faster transport rate.

[0071] Table 3 Summary of test data for composite membranes in different types of chloride salt solutions

[0072] Salt solution system Lithium chloride Sodium chloride Potassium chloride Magnesium chloride Calcium chloride <![CDATA[Power density (W m -2 )]]> 3.4 5.26 6.07 1.84 2.02

[0073] Example 12

[0074] Test methods for converting acid gradient energy into electrical energy:

[0075] Similarly, as follows Figure 2 The apparatus shown has a concentrated acid solution in the right container and a dilute acid solution in the left container. Unless otherwise specified, the salt types in both solutions are the same. Each container has a recess for injecting the solution and inserting an Ag / AgCl electrode. The diaphragm material prepared in Examples 1-7 is installed between the two containers and secured with screws. The two solutions are connected in a circuit via an external ammeter and a load resistor for acid-base energy conversion testing.

[0076] Example 13

[0077] This embodiment examines the output power of the composite membrane under different acid concentration gradients.

[0078] The composite membrane prepared in Example 3 was selected as the membrane material, and the installation method was the same as in Example 12. Hydrochloric acid solution was chosen as the acid solution. The inventors discovered that the acid system differs from the salt system in that the optimal power density corresponds to different resistance values ​​for different concentration gradients and acid systems. Figure 6 The table shows the resistance values ​​corresponding to the optimal power density of the hydrochloric acid system under different concentration gradients. It was found that in the hydrochloric acid system, when the concentration gradient between concentrated and dilute acid was 5 times and 10 times, the resistance value corresponding to the optimal power density was 1000 Ω; when the concentration gradient was 50 times and 100 times, the resistance value was 3000 Ω; when the concentration gradient was 500 times, the resistance value was 5000 Ω; and when the concentration gradient was 1000 times, the resistance value was 13 kΩ. The maximum power density was recorded in Table 4. The results show that when the composite membrane is placed in an acidic solution system, the power density is significantly higher than that in a salinity gradient system. The maximum power density is 67.08 W / m² when the concentration gradient is 100 times. -2 .

[0079] Table 4 Summary of test data for composite membranes under different acid concentration gradients

[0080] Concentration gradient 5 times 10 times 50 times 100 times 500 times 1000 times <![CDATA[Power density (W m -2 )]]> 23.59 38.53 62.50 67.08 64.04 59.32

[0081] Example 14

[0082] This application investigates the output power of the composite membrane in different acids.

[0083] The composite membrane prepared in Example 3 was selected as the membrane material. The installation method was the same as in Example 12. The acid solutions used were hydrochloric acid (external resistance 3000Ω), sulfuric acid (external resistance 27kΩ), oxalic acid (external resistance 17kΩ), phosphoric acid (external resistance 40kΩ), formic acid (external resistance 150kΩ), and acetic acid (external resistance 220kΩ). Tests were conducted with a concentration gradient of 1000 times between concentrated and dilute solutions. The results are shown in Table 5. It was found that the power density was significantly higher when the acid solution system was hydrochloric acid than that of other acid types.

[0084] Table 5 Summary of test data for composite membranes in different acids

[0085] Acid solution system hydrochloric acid sulfuric acid oxalic acid Phosphoric acid Formic acid acetic acid <![CDATA[Power density (W m -2 )]]> 59.32 5.31 1.51 1.58 0.09 0.13

[0086] Example 15

[0087] This embodiment examines the stability test of the composite membrane in an acidic system.

[0088] The composite membrane prepared in Example 3 was selected as the membrane material. The installation method was the same as in Example 12. Hydrochloric acid solution was selected as the acid solution, and the current change was tested for 12 hours. The results are shown in [link to example]. Figure 7 . Figure 7 The curve shows the change of current over time. It indicates that the current output is stable after 12 hours with only slight fluctuations, which shows that the membrane can stably carry out ion transmembrane transport, which is beneficial to promoting the continuous harvest of permeation energy. Figure 8 The images are electron microscope images of the composite membrane after the stability test. It can be seen that the composite membrane was undamaged after the stability test and still has a complete layered structure.

[0089] Example 16

[0090] This embodiment examines the transparency of the samples prepared in Examples 1-7.

[0091] Different samples were placed on a pattern bearing the logo of the Institute of Physics and Chemistry, and the transparency of the different samples was observed. The results are shown in [Figure number missing]. Figure 9 It was found that, except for the pure graphene oxide film, all other films were transparent and uniform, and the transparency gradually decreased with the increase of graphene oxide content.

[0092] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. Use of a cellulose / graphene oxide composite membrane in osmotic power generation, characterized in that, Using a cellulose / graphene oxide composite membrane as the membrane material, chemical energy is converted into electrical energy by utilizing the acid difference of the electrolyte; The cellulose / graphene oxide composite membrane is made by doping cellulose with 1-20 wt% graphene oxide dispersion. When using the acid difference of the electrolyte for osmotic power generation, an Ag / AgCl electrode is selected, the concentration gradient between the concentrated acid solution and the dilute acid solution is 5-1000 times, and an external load resistor of 0-1000KΩ is connected. The acid solution is selected from hydrochloric acid solution, sulfuric acid solution, oxalic acid solution, phosphoric acid solution, formic acid solution or acetic acid solution.

2. Use according to claim 1, characterized in that, The cellulose / graphene oxide composite membrane has a two-dimensional sheet structure with a thickness of 4~6μm and a single-layer spacing of 0.9~1.2nm.

3. Use according to claim 1, characterized in that, The doping amount of the graphene oxide dispersion is 5-15 wt%.

4. Use according to claim 1, characterized in that, The doping amount of the graphene oxide dispersion is 5-10 wt%.

5. The use according to claim 1, characterized in that, The doping amount of the graphene oxide dispersion is 10-15 wt%.

6. Use according to claim 1, characterized in that, The concentration of the graphene oxide dispersion is 2 mg / L.

7. Use according to claim 1, characterized in that, The concentration of the concentrated acid solution is 0.5M, and the concentration of the dilute acid solution is 0.5-100mM.

8. The application according to claim 1, characterized in that, The concentrated acid solution and the dilute acid solution contain the same type of acid.

9. The application according to claim 1, characterized in that, The cellulose / graphene oxide composite membrane is prepared by the following method: Cellulose is dissolved in water, then mixed with graphene oxide dispersion in a certain proportion, sonicated for 15-30 minutes, filtered through a PC filter membrane, dried, and then peeled off from the PC filter membrane to obtain the final product.

10. The application according to claim 9, characterized in that, The cellulose is doped with 1-20 wt% of graphene oxide dispersion.

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