Permeation power generation method based on polyelectrolyte modified nano channel

Abstract

The invention discloses a permeation power generation method based on a polyelectrolyte modified nano-channel. The power generation method comprises the following steps: grafting a polyelectrolyte brush layer on the surface of the nano-channel through a covalent bond; injecting electrolyte solutions with different concentrations into the two ends of the nano-channel respectively to form a concentration gradient; applying a temperature gradient opposite to the concentration gradient direction to the two ends of the nano channel, so that the temperature difference between the high-temperature side and the low-temperature side is 40K; regulating and controlling the pH values of the high-concentration electrolyte solution and the low-concentration electrolyte solution, so that the pH values of the solutions on the two sides are both smaller than the equipotential point of the polyelectrolyte brush layer, or the pH values of the solutions on the two sides are both larger than the equipotential point of the polyelectrolyte brush layer; electrodes are arranged on the two sides of the nanometer channel, ion migration is cooperatively driven through concentration gradient, temperature gradient and ion selectivity of the polyelectrolyte brush layer to generate permeation current and permeation voltage, and permeation power generation is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of osmotic power generation, and in particular to an osmotic power generation method based on polyelectrolyte-modified nanochannels. Background Art

[0002] Ion channels in living organisms have the ability to precisely regulate ion transport and energy conversion, a property that plays a key role in life activities. Inspired by this biological mechanism, the study of biomimetic nanochannels has gradually become a hot topic. Due to the existence of nanoscale effects, nanofluid transport exhibits significantly different characteristics from bulk ion transport, which gives it broad application prospects in many fields such as ion rectification, nanosensing, energy conversion, and seawater desalination. The uniqueness of nanofluid transport is mainly related to the double layer within the nanoconfined space. By controlling the ion selectivity of the double layer, ultrafast ion transport and efficient energy conversion can be achieved, and it is regarded as a very promising energy conversion method.

[0003] Currently, research on biomimetic nanochannels is primarily based on two-dimensional materials such as molybdenum disulfide, boron nitride, and graphene oxide, which are stacked or arranged to form nano / subnano channels for ion transport and energy conversion. While structural design techniques such as regulating interlayer spacing and surface functionalization can optimize ion selectivity and transport performance to a certain extent, the physical and chemical properties of the materials themselves limit the potential for enhancing osmotic power generation performance through structural design alone, making it difficult to overcome the bottleneck of the material's intrinsic properties.

[0004] Furthermore, existing nanofluid energy conversion systems are often limited to single-factor regulation in response to external environmental stimuli, such as light, pH, or temperature. However, in complex real-world environments like nuclear waste heat and industrial wastewater, a single stimulus cannot fully adapt to changes in multiple environmental parameters. Therefore, constructing an energy conversion system capable of responding to multiple environmental stimuli has become a pressing technical challenge in this field. Summary of the Invention

[0005] In view of the above-mentioned prior art, the present invention provides an osmotic power generation method based on polyelectrolyte-modified nanochannels, which mainly solves the technical problems existing in the above-mentioned background technology.

[0006] To achieve the above-mentioned purpose, the technical solution of the embodiment of the present invention is implemented as follows: a method for osmotic power generation based on polyelectrolyte-modified nanochannels, the method comprising the following steps:

[0007] Grafting a polyelectrolyte brush layer on the surface of the nanochannel via covalent bonds, wherein the polyelectrolyte brush layer comprises a weak acidic functional group and a weak basic functional group;

[0008] Injecting electrolyte solutions of different concentrations into both ends of the nanochannel to form a concentration gradient, wherein the electrolyte solutions of different concentrations include a high-concentration electrolyte solution and a low-concentration electrolyte solution;

[0009] Applying a temperature gradient opposite to the concentration gradient to both ends of the nanochannel so that the temperature difference between the high-temperature side and the low-temperature side is 40K;

[0010] Regulating the pH values ​​of the high-concentration electrolyte solution and the low-concentration electrolyte solution so that the pH values ​​of the solutions on both sides are lower than the isoelectric point of the polyelectrolyte brush layer, or so that the pH values ​​of the solutions on both sides are higher than the isoelectric point of the polyelectrolyte brush layer;

[0011] Electrodes are set on both sides of the nanochannel, and the concentration gradient, temperature gradient and ion selectivity of the polyelectrolyte brush layer are used to synergistically drive ion migration to generate osmotic current and osmotic voltage, thereby realizing osmotic power generation.

[0012] Preferably, the weakly acidic functional group is a carboxyl group, and the weakly basic functional group is an amino group.

[0013] Preferably, the grafting density of the polyelectrolyte brush layer is 0.05–0.6 chains / nm 2 .

[0014] Preferably, the concentration ratio of the high-concentration electrolyte solution to the low-concentration electrolyte solution satisfies:

[0015]

[0016] Among them, C h represents the concentration of high-concentration electrolyte solution, and Cl represents the concentration of low-concentration electrolyte solution.

[0017] Preferably, the high-concentration electrolyte solution and the low-concentration electrolyte solution are both sodium chloride solutions, wherein the concentration of the high-concentration sodium chloride solution is 0.2 mol / L-0.5 mol / L, and the concentration of the low-concentration sodium chloride solution is 0.01 mol / L-0.02 mol / L.

[0018] Optionally, regulating the pH values ​​in the high-concentration electrolyte solution and the low-concentration electrolyte solution to deviate from the isoelectric point specifically includes: adding an acid-containing additive liquid to both the high-concentration and low-concentration sodium chloride solutions so that the pH values ​​of the solutions on both sides are less than the isoelectric point, or adding an alkali-containing additive liquid to both the high-concentration and low-concentration sodium chloride solutions so that the pH values ​​of the solutions on both sides are greater than the isoelectric point.

[0019] Optionally, when the pH of the solutions on both sides is less than 5.5 and a temperature gradient in a counter-gradient direction is applied, the anion diffusion coefficient increases.

[0020] Optionally, when the pH of the solutions on both sides is greater than 5.5 and a temperature gradient in a counter-gradient direction is applied, the cation diffusion coefficient increases.

[0021] The beneficial effects of the present invention are: through the pH response characteristics of the polyelectrolyte brush layer, dynamic regulation of the ion selectivity of the nanochannel is achieved, and the anion or cation selectivity can be reversibly switched according to the pH environment of the solution, breaking through the limitations of the fixed ion transport type of traditional nanochannels, and providing a flexible regulation mechanism for the directional transport of ions in complex scenarios; utilizing the synergistic effect of the temperature gradient and pH in the anti-gradient direction to enhance the difference in ion diffusion coefficients and the counterion enrichment effect, significantly improving the ion selectivity and diffusion driving force in the osmotic power generation process, breaking through the performance bottleneck under a single environmental stimulus, and constructing an efficient multi-field coupled energy conversion system; through the optimization of the grafting density and concentration gradient design of the polyelectrolyte brush layer, the system is given adaptability to a wide range of pH and concentration conditions, and can adapt to multiple complex environments such as industrial wastewater and nuclear waste heat, broadening the actual application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Description of Figure Numbers:

[0023] Figure 1 Schematic diagram of the polyelectrolyte brush layer grafted onto the surface of the nanochannel in the embodiment of the present application through covalent bonds, wherein Figure 1 (a) is a schematic diagram of osmotic energy conversion and a schematic diagram of polyelectrolyte-modified nanochannels. Figure 1 (b) Schematic diagram of the protonation and deprotonation reactions within the polyelectrolyte brush layer. Figure 1 (c) Schematic diagram of a simplified two-dimensional axisymmetric model.

[0024] Figure 2 Schematic diagram of the temperature difference model and the changes in axial temperature and cation concentration in the embodiment of the present application, wherein: Figure 2 (a) Schematic diagram showing the direction of the temperature gradient and the concentration gradient are consistent. Figure 2 (b) Schematic diagram showing the case where the temperature gradient and concentration gradient are in opposite directions. Figure 2 (c) shows the axial temperature change under different temperature conditions, Figure 2 (d) represents the average volume charge density of the brush layer at different pH values ​​under isothermal conditions;

[0025] Figure 3 Schematic diagram of the axial hydrogen ion concentration distribution in the brush layer and the deprotonation ratio and protonation ratio of the brush layer at pH 4 and 9, where Figure 3 (a) Schematic diagram of the axial hydrogen ion concentration distribution in the brush layer at pH 4, where Figure 3 (b) Schematic diagram showing the deprotonation ratio of the brush layer at pH 4. Figure 3 (c) Schematic diagram showing the protonation ratio of the brush layer at pH 4. Figure 3(d) Schematic diagram showing the axial hydrogen ion concentration distribution in the brush layer when pH is 9. Figure 3 (e) Schematic diagram showing the deprotonation ratio of the brush layer at pH 9. Figure 3 (f) Schematic diagram showing the protonation ratio of the brush layer at pH 9.

[0026] Figure 4 is a schematic diagram of the axial charge density distribution of the brush layer at pH 4 and 9, where Figure 4 (a) is the axial charge density distribution of the brush layer at pH 4. Figure 4 (b) Axial charge density distribution of the brush layer at pH 9.

[0027] Figure 5 Schematic diagram showing the relationship between the ratio of the output current corresponding to the IGD and OGD and the output current under isothermal conditions when pH = 1 and at different temperature differences.

[0028] Figure 6 Schematic diagram showing the relationship between the ratio of the output current corresponding to IGD and OGD and the output current under isothermal conditions when pH = 3 and at different temperature differences.

[0029] Figure 7 Schematic diagram showing the relationship between the ratio of the output current corresponding to IGD and OGD and the output current under isothermal conditions at pH = 5 and different temperature differences.

[0030] Figure 8 Schematic diagram showing the relationship between the output current of IGD and OGD and the current ratio under isothermal conditions at pH = 7 and different temperature differences.

[0031] Figure 9 Schematic diagram showing the relationship between the ratio of the output current corresponding to IGD and OGD and the output current under isothermal conditions at pH = 9 and different temperature differences.

[0032] Figure 10 Schematic diagram showing the relationship between the ratio of the output current corresponding to the IGD and OGD and the output current under isothermal conditions when pH=11 and at different temperature differences.

[0033] Figure 11 Schematic diagram showing the relationship between the ratio of the output current corresponding to the IGD and OGD and the output current under isothermal conditions at pH = 13 and different temperature differences.

[0034] Figure 12 Schematic diagram showing the process of osmotic power generation based on polyelectrolyte-modified nanochannels. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further elaborated in detail below in conjunction with the drawings and specific embodiments of the specification. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the following description, reference is made to "some embodiments", which describes a subset of all possible embodiments, but it should be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0036] In the following description, numerous specific details are provided to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details. In other instances, certain technical features well known in the art are not described to avoid confusion with the present invention.

[0037] It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments proposed herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. And the purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "comprising" and / or "comprising" when used in this specification determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0038] It should also be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "inner," "outer," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0039] In order to fully understand the present invention, a detailed structure will be provided in the following description to illustrate the technical solution proposed by the present invention. Optional embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other implementations.

[0040] Please refer to the attached Figures 1 to 12 The present application provides a method for osmotic power generation based on polyelectrolyte-modified nanochannels, the method comprising the following steps:

[0041] S1. Grafting a polyelectrolyte brush layer onto the surface of the nanochannel via covalent bonds, wherein the polyelectrolyte brush layer comprises a weakly acidic functional group and a weakly basic functional group, wherein the weakly acidic functional group is a carboxyl group and the weakly basic functional group is an amino group, and the grafting density of the polyelectrolyte brush layer is 0.05–0.6 chains / nm 2 ;

[0042] S2. Injecting electrolyte solutions of different concentrations into both ends of the nanochannel to form a concentration gradient, wherein the electrolyte solutions of different concentrations include a high-concentration electrolyte solution and a low-concentration electrolyte solution;

[0043] S3, applying a temperature gradient opposite to the concentration gradient to both ends of the nanochannel, so that the temperature difference between the high-temperature side and the low-temperature side is 40K;

[0044] S4, regulating the pH values ​​of the high-concentration electrolyte solution and the low-concentration electrolyte solution so that the pH values ​​of the solutions on both sides are lower than the isoelectric point of the polyelectrolyte brush layer, or so that the pH values ​​of the solutions on both sides are higher than the isoelectric point of the polyelectrolyte brush layer;

[0045] S5. Electrodes are set on both sides of the nanochannel, and the concentration gradient, temperature gradient and ion selectivity of the polyelectrolyte brush layer are used to synergistically drive ion migration to generate osmotic current and osmotic voltage, thereby realizing osmotic power generation.

[0046] See also Figure 1 In some embodiments, the polyelectrolyte brush layer contains weakly acidic functional groups and weakly basic functional groups, and the polyelectrolyte brush layer containing weakly acidic functional groups and weakly basic functional groups is grafted onto the nanochannel surface through covalent bonds. The grafting density of the polyelectrolyte brush layer on the nanochannel surface is controlled to be 0.05-0.6 chains / nm. 2 To ensure the stable attachment of the brush layer and its ability to respond to external pH stimulation, its protonation and deprotonation reactions will produce a bulk charge density related to the local hydrogen ion concentration. When the pH of the solution changes, the charge properties of the brush layer will be reversed due to the isoelectric point (5.5), that is, it will be positively charged when pH < 5.5 and negatively charged when pH > 5.5, thereby changing the ion selectivity of the nanochannel, that is, the channel will be anion selective when pH < 5.5 and cation selective when pH > 5.5.

[0047] In some embodiments, the concentration ratio of the high-concentration electrolyte solution to the low-concentration electrolyte solution satisfies:

[0048]

[0049] Among them, C h represents the concentration of high-concentration electrolyte solution, and Cl represents the concentration of low-concentration electrolyte solution.

[0050] Furthermore, the high-concentration electrolyte solution and the low-concentration electrolyte solution are both sodium chloride solutions, wherein the concentration of the high-concentration sodium chloride solution is 0.2 mol / L-0.5 mol / L, and the concentration of the low-concentration sodium chloride solution is 0.01 mol / L-0.02 mol / L.

[0051] Furthermore, the pH values ​​in the high-concentration electrolyte solution and the low-concentration electrolyte solution are regulated to deviate from the isoelectric point, specifically including: adding an acid-containing additive liquid to both the high-concentration and low-concentration sodium chloride solutions so that the pH values ​​of the solutions on both sides are less than the isoelectric point, or adding an alkali-containing additive liquid to both the high-concentration and low-concentration sodium chloride solutions so that the pH values ​​of the solutions on both sides are greater than the isoelectric point, and when the pH of the solutions on both sides is less than 5.5 and a temperature gradient in the counter-gradient direction is applied, the anion diffusion coefficient increases, and when the pH of the solutions on both sides is greater than 5.5 and a temperature gradient in the counter-gradient direction is applied, the cation diffusion coefficient increases.

[0052] Specifically, when the pH of the solutions on both sides is less than 5.5, and there is a reverse temperature gradient between the high-concentration electrolyte solution and the low-concentration electrolyte solution, the polyelectrolyte brush layer undergoes a protonation reaction on the high-concentration side, and the amino group is converted into a positively charged ammonium ion, giving the brush layer a positive charge characteristic. The electrostatic attraction significantly reduces the activation energy barrier for chloride ion migration and enhances its migration tendency. The reverse temperature gradient places the high-temperature side at the low-concentration end, and the solution viscosity η decreases exponentially with increasing temperature, directly increasing the anion diffusion coefficient. Its thermophoretic effect generates an additional driving force in the temperature gradient field. The thermal diffusion term is in the same direction as the concentration gradient, so that the chloride ions gain additional kinetic energy when migrating from high concentration (low temperature) to low concentration (high temperature).

[0053] When the pH of the solutions on both sides is less than 5.5, the polyelectrolyte brush layer undergoes deprotonation on the alkaline, low-concentration side, dissociating the carboxyl groups into negatively charged carboxylate ions, giving the brush layer a negative charge. This negative electric field exerts an electrostatic attraction on sodium ions, lowering the activation energy barrier for their migration across the interface and increasing their migration propensity. Simultaneously, the reverse temperature gradient positions the high-temperature side at the low-concentration end. The solution viscosity η is inversely proportional to the temperature T, resulting in a quadratic increase in the ion diffusion coefficient with increasing temperature. When ΔT = 40 K, a temperature increase from 298 K to 338 K decreases the viscosity by 53% and increases the sodium ion diffusion coefficient by 119%. This process is further enhanced by the thermophoretic effect: cations in the temperature gradient field are driven by the Soret force, and the additional thermal diffusion term migrating in the low-concentration (high-temperature) direction aligns with the concentration diffusion direction, producing a synergistic acceleration effect, thereby increasing the cation diffusion coefficient.

[0054] In order to study the performance of osmotic power generation, the performance is evaluated by the ion transfer number:

[0055]

[0056] Where t - and t + are the anion and cation transfer numbers respectively. From this, the diffusion voltage V can be further calculated d , diffusion current I d , the power P generated by osmotic energy conversion and the maximum conversion efficiency η max :

[0057]

[0058] γ cH and γ cL are the ion activity coefficients at the high and low concentration ends, respectively, and S is the ion activity coefficient at either end of the reservoir.

[0059] The ion selectivity of a channel is expressed in terms of the cation transfer number. A cation transfer number of 0.5 indicates that the channel is non-selective. A cation transfer number less than 0.5 indicates that the channel is anion selective, and a cation transfer number greater than 0.5 indicates that the channel is cation selective.

[0060] As the pH increases from 4 to 9, the channel shifts from anion-selective to cation-selective, primarily due to a pH-induced reversal of the brush layer's charge properties. When the pH is below the isoelectric point, the brush layer carries a positive charge, conferring anion selectivity on the channel. When the pH is above the isoelectric point, the channel becomes cation-selective. The lower (higher) the pH, the stronger the channel's anion (cation) selectivity. It's important to note that at pH 6 (above the isoelectric point), the channel's cation transfer number is less than 0.5, indicating anion selectivity. This is primarily due to the low bulk charge density of the brush layer at this point, resulting in lower selectivity. Driven by the concentration gradient, more chloride ions migrate from the high-concentration to the low-concentration side. Because the diffusion coefficient of chloride ions is greater than that of sodium ions, the diffusion of hydrogen and hydroxide ions is negligible. When the concentration gradient is increased 500-fold, the pH at which ion selectivity is absent (t+ = 0.5) shifts from 6.3 to 7.1. Similarly, the pH corresponding to the ionic current minimum shifts, further confirming that excessively low brush layer bulk charge density near the isoelectric point leads to a decrease in ion selectivity, or even a reversal. When it is anion selective, the anti-gradient direction will reduce the cation transfer number, while the same gradient direction will increase the cation transfer number.

[0061] When the channel is cation selective, the opposite is true. Under the conditions of the same gradient direction, ions move from high concentration to low concentration, the diffusion coefficient gradually decreases, and ion movement becomes difficult, resulting in the enrichment of counterions inside the channel. Therefore, when the pH is less than 6.3, the number of cation transfers will increase in the same gradient direction, and the number of cation transfers will decrease when the pH is greater than 6.3. It can also be seen from the net ion concentration (cation concentration minus anion concentration) that when the brush layer carries positive charge (pH = 4), the concentration of cations will decrease in the same gradient direction, while when it carries negative charge (pH = 9), the concentration of cations will increase. When the concentration gradient of the solution changes, the ion selectivity of the channel gradually decreases, and the temperature difference conditions in the opposite gradient direction will increase the ion selectivity. In addition, another common result is that the concentration gradient increases, and the driving force for the movement of ions from high concentration to low concentration increases, resulting in an increase in ion current.

[0062] The calculation formula for diffusion voltage shows that when the solution concentration gradient is constant, the voltage is primarily related to the cation transfer number. The closer the cation transfer number is to 0.5, the lower the ion selectivity, and the lower the voltage. The voltage is calculated as an absolute value here, so it can be seen that with increasing pH, the voltage first decreases and then increases. Temperature conditions in the opposite direction of the gradient increase the voltage, primarily because they enhance ion selectivity. The maximum voltage reaches 104 mV at pH 9. When the solution concentration gradient increases 500-fold, the voltage increase in the opposite direction is even more significant, reaching a maximum of 135 mV. When the concentration gradient changes, the voltage is synergistically affected by the cation transfer number and the concentration gradient. As the concentration gradient increases, the cation transfer number gradually approaches 0.5. Therefore, there is a balance between the voltage drop caused by the cation transfer number and the voltage increase caused by the concentration gradient. This ultimately manifests as an increase and then a decrease in voltage.

[0063] When the pH is near the isoelectric point (5.5), the power generated is close to zero. This is because near the isoelectric point, the bulk charge density of the brush layer is low, resulting in reduced ion selectivity. According to the formula for calculating the power P generated by osmotic energy conversion, the power is affected by both current and voltage. When the pH is below the isoelectric point, an increase in pH leads to a decrease in power, due to a simultaneous decrease in current and voltage. When the pH is above the isoelectric point, an increase in pH leads to an increase in power, due to a simultaneous increase in current and voltage. The power generated in the counter-gradient direction is the highest at different pH values, reaching a maximum of 0.0628 pW. Furthermore, at a 500-fold gradient, the power reaches a maximum of 0.463 pW at pH 9, an increase of approximately 737% compared to a 50-fold salt gradient. Similarly, the counter-gradient direction generates the highest power at different concentrations. At a 1000-fold salt gradient, the power generated in the counter-gradient direction at pH 4 and pH 9 increases by 123% and 116%, respectively, compared to isothermal conditions.

[0064] Similar to the trend of voltage, power and other parameters, the maximum energy conversion efficiency is close to 0 at pH 6. This is because the ion selectivity and voltage of the channel are very small, resulting in low conversion efficiency. When the salt gradient is 500 times, the minimum value shifts to the pH 7 position. According to the diffusion voltage V d , diffusion current I d , the power P generated by osmotic energy conversion and the maximum conversion efficiency η max The calculation formula shows that when the concentration gradient remains constant, the maximum energy conversion efficiency is mainly related to ion selectivity. The maximum energy conversion efficiency at 50- and 500-fold salt gradients can reach 47% and 31%, respectively. When the concentration gradient of the solution is changed, it can be found that the greater the concentration gradient, the lower the energy conversion efficiency, whether at pH 4 or pH 9. This is mainly because the higher the concentration, the lower the ion selectivity of the channel, and the temperature difference in the direction opposite to the gradient produces the highest conversion efficiency. This shows that the opposite gradient direction is more conducive to improving the performance of osmotic power generation, whether under acidic or alkaline conditions.

[0065] Taking pH = 4 as an example, under acidic conditions of pH = 4, the hydrogen ion concentration of the solution is 0.1 mol / m 3 The hydrogen ion concentration in the channel decreases as it approaches the lower-concentration side, remaining below the bulk solution concentration. The hydrogen ion concentration in the in-gradient direction (IGD) is higher than that in the opposite-gradient direction (OGD) at the same location. As ions diffuse from high to low concentration, the diffusion coefficient along the nanochannel axis decreases, leading to ion enrichment (including sodium ions) within the channel. The hydrogen ion concentration in the channel solution domain is greater than that in the brush layer because the positive charge of the brush layer repels cations and the protonation reaction consumes hydrogen ions. The hydrogen ion concentration decreases closer to the channel wall.

[0066] The brush layer carries a positive charge due to the dominant protonation reaction, while the deprotonation reaction is negligible. The uneven distribution of hydrogen ion concentration along the axial direction, with a gradual increase from the low-concentration side to the high-concentration side, leads to a gradual increase in the protonation ratio and a decrease in the deprotonation ratio within the brush layer.

[0067] The axial charge density of the brush layer increases gradually from the low-concentration side to the high-concentration side, increasing by approximately 259%. The radial charge density decreases closer to the channel wall. Near the low-concentration side, the charge density in the same gradient direction (IGD) is greater than that under the warm condition (IT). The difference in trend with the center and high-concentration side is due to the hydrogen ion concentration distribution. Under these conditions, the channel is anion-selective due to the positive charge of the brush layer, with a cation transfer number of 0.4 (less than 0.5). Model calculations show an osmotic voltage of 85mV, a power density of 0.045pW, and a maximum energy conversion efficiency of 38%.

[0068] Taking pH = 9 as an example, under alkaline conditions of pH = 9, the hydrogen ion concentration of the body solution is 10 -6 mol / m 3 The hydrogen ion concentration gradually decreases from the low-concentration side to the high-concentration side, reaching only 19.39% of that on the high-concentration side and exceeding the bulk solution hydrogen ion concentration. The negative charge of the brush layer attracts cations, increasing the hydrogen ion concentration within the brush layer. However, the abundant sodium ions on the high-concentration side repel hydrogen ions, causing the hydrogen ion concentration near the high-concentration side to decrease. The hydrogen ion concentration at different locations in the channel is consistently greater within the brush layer than in the solution domain, with the concentration increasing closer to the channel wall.

[0069] The deprotonation reaction in the brush layer is dominant, and the deprotonation ratio is about 10 at pH = 4. 8 The uneven distribution of hydrogen ion concentration, which gradually decreases from the low-concentration side to the high-concentration side, causes the deprotonation ratio in the brush layer to gradually increase from the low-concentration side to the high-concentration side, while the protonation ratio gradually decreases. From the low-concentration side to the high-concentration side, the protonation ratio decreases by about 27%, while the deprotonation ratio increases by about 193%.

[0070] The brush layer carries a negative charge, and the axial bulk charge density increases gradually from the low-concentration side to the high-concentration side, increasing by approximately 416%. The radial bulk charge density decreases closer to the channel wall. Applying a temperature gradient in the opposite direction of the gradient increases the brush layer bulk charge density, and the trend of bulk charge density at different locations is consistent with the axial direction. Because the brush layer is negatively charged and cation-selective, sodium ions on the high-concentration side repel hydrogen ions, leading to a local increase in pH and a subsequent increase in bulk charge density.

[0071] Under these conditions, the channel exhibits cation selectivity due to the negative charge of the brush layer, with a cation transfer number of 0.65 (greater than 0.5). Model calculations show an osmotic voltage of 135 mV, a power density of 0.463 pW, and a maximum energy conversion efficiency of 31%.

[0072] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. The scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for osmotic power generation based on polyelectrolyte-modified nanochannels, characterized in that: The power generation method comprises the following steps: Grafting a polyelectrolyte brush layer on the surface of the nanochannel via covalent bonds, wherein the polyelectrolyte brush layer comprises a weak acidic functional group and a weak basic functional group; Injecting electrolyte solutions of different concentrations into both ends of the nanochannel to form a concentration gradient, wherein the electrolyte solutions of different concentrations include a high-concentration electrolyte solution and a low-concentration electrolyte solution; Applying a temperature gradient opposite to the concentration gradient to both ends of the nanochannel so that the temperature difference between the high-temperature side and the low-temperature side is 40K; Regulating the pH values ​​of the high-concentration electrolyte solution and the low-concentration electrolyte solution so that the pH values ​​of the solutions on both sides are lower than the isoelectric point of the polyelectrolyte brush layer, or so that the pH values ​​of the solutions on both sides are higher than the isoelectric point of the polyelectrolyte brush layer; Electrodes are set on both sides of the nanochannel, and the concentration gradient, temperature gradient and ion selectivity of the polyelectrolyte brush layer are used to synergistically drive ion migration to generate osmotic current and osmotic voltage, thereby realizing osmotic power generation.

2. The osmotic power generation method based on polyelectrolyte-modified nanochannels according to claim 1, characterized in that: The weakly acidic functional group is a carboxyl group, and the weakly basic functional group is an amino group.

3. The osmotic power generation method based on polyelectrolyte modified nanochannels according to claim 1, characterized in that: The grafting density of the polyelectrolyte brush layer is 0.05–0.6 chains / nm 2 .

4. The osmotic power generation method based on polyelectrolyte modified nanochannels according to claim 1, characterized in that: The concentration ratio of the high-concentration electrolyte solution to the low-concentration electrolyte solution satisfies: Among them, C h represents the concentration of high-concentration electrolyte solution, and Cl represents the concentration of low-concentration electrolyte solution.

5. The osmotic power generation method based on polyelectrolyte-modified nanochannels according to claim 2, characterized in that: The high-concentration electrolyte solution and the low-concentration electrolyte solution are both sodium chloride solutions, wherein the concentration of the high-concentration sodium chloride solution is 0.2 mol / L-0.5 mol / L, and the concentration of the low-concentration sodium chloride solution is 0.01 mol / L-0.02 mol / L.

6. The osmotic power generation method based on polyelectrolyte modified nanochannels according to claim 2, characterized in that: Regulating the pH values ​​of the high-concentration electrolyte solution and the low-concentration electrolyte solution to deviate from the isoelectric point specifically includes: adding an acid-containing additive liquid to both the high-concentration and low-concentration sodium chloride solutions so that the pH values ​​of the solutions on both sides are lower than the isoelectric point, or adding an alkali-containing additive liquid to both the high-concentration and low-concentration sodium chloride solutions so that the pH values ​​of the solutions on both sides are higher than the isoelectric point.

7. The osmotic power generation method based on polyelectrolyte modified nanochannels according to claim 6, characterized in that: When the pH of the solutions on both sides is less than 5.5 and a temperature gradient in the opposite direction is applied, the anion diffusion coefficient increases.

8. The osmotic power generation method based on polyelectrolyte-modified nanochannels according to claim 6, characterized in that: When the pH of the solutions on both sides is greater than 5.5 and a temperature gradient in the opposite direction is applied, the cation diffusion coefficient increases.

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