TW201822452A - Microchannel electric energy conversion model having high electric double layer overlap effect and method thereof have function of improving freedom ion space charge density through ions inside channel - Google Patents

Abstract

A microchannel electric energy conversion model having high electric double layer overlap effect and its method is a technique of converting generated kinetic energy into the maximum electric energy P while using an external pressure gradient to drive an electrolyte flowing in a microchannel at a height h. The salt concentration of the electrolyte is C.sub.salt, and the thickness of the electric double layer in the microchannel is [lambda].sub.D= √ ([epsilon].sub.f RT / 2F.supra.2 C.sub.salt). When (h/2)x(1/[lambda]D)≤1 is satisfied, an ion type buffer solvent is added into the electrolyte having low salt concentration to accomplish a maximum conversion electric energy P.sub.low. Alternatively, the buffer solvent is added into the electrolyte having high salt concentration to accomplish a maximum conversion electric energy P.sub.high, and P.sub.low > P.sub.high-P to accomplish efficacy of simultaneously improving the maximum energy conversion efficiency and the maximum energy output power.

Description

   Micro-channel electric energy conversion model and method with high-electricity double-layer overlap effect   

The invention belongs to the technical field of electric power flow, and particularly relates to a micro-channel electric energy conversion model and method with overlapping effects of high electric double layers (EDLs), so as to achieve the maximum energy conversion efficiency and the maximum energy at the same time. Effect of output power.

In recent decades, nanoenergy conversion devices have received considerable attention due to the advancement of nanotechnology manufacturing technology. In particular, a nanofluidic electric energy conversion device using a combination of nanofluidic devices and electrodynamic phenomena is considered as a potential solution for clean and renewable energy due to its simple structure and has significant research results. After the nanochannel is filled with the electrolyte, the pressure gradient or concentration gradient is used to drive the electrolyte to flow, and then the theory of "flow potential and current" is generated. EDLs will appear on the solid-liquid interface of liquids containing electrolytes or ions in the nano-channels. This interface phenomenon will affect the electrokinetic effects in the micro-channels, and then affect the efficiency of electric energy conversion in the channels.

In other words, in the aqueous environment, the wall of the channel generally has electrostatic charges, and when the liquid contains trace ions, the static charges on the wall will attract counterions in the liquid and repel the same ions (coions), thereby forming EDLs. . At this time, the counter-ion ions are gathered near the wall and the concentration is high; the ions with the same number are far away and the concentration is low, so that the concentration of the counter-ion and the ions of the same number are exponentially decreased and increased, resulting in uneven concentrations of positive and negative ions in EDLs, This results in a free ion space charge density. Therefore, if a pressure gradient is given at both ends of the micro-nano channel to drive the electrolyte, that is, when a liquid containing electrolyte or ions flows along the channel axial direction, the high-contrast counter-ion ions in the EDLs will be formed as the flow direction moves. A flowing current. In addition, when a larger number of counter ions are collected downstream of the channel, the potential potentials upstream and downstream of the channel will be different, and a streaming potential will be generated. This potential will also cause the flow The conduction current in the opposite direction of the current. The movement behavior of the above-mentioned ions with the same ions and counter ions under the action of an applied pressure gradient will affect the flow potential / current behavior of the entire system. When this micro-nano runner electric energy conversion device is connected to an external load, it can The output of electrical energy is the realization of converting mechanical energy into electrical energy.

In addition, according to previous research results, it is known that the energy conversion efficiency and outputtable energy power during the conversion of electric energy are deeply affected by the channel height, the static charge on the channel wall surface, the flow field distribution in the channel, and the pH and concentration of the electrolyte. Parameters, and in order to increase the static charge on the channel wall, surface chemical modification techniques are most commonly used in the past: modified micronano channel walls have electrostatic properties or added water-soluble polymers to use their shear thinning ) Characteristics, thereby improving electric power conversion efficiency or efficiency. However, previous researches have found that when further improving the electric energy output power by adjusting these parameters, it is found that the energy conversion efficiency is relatively low, and vice versa.

Feeling this, how can the static charge on the wall of the channel be stably controlled, and then the maximum electrokinetic power output and maximum conversion efficiency can be greatly increased at the same time, so as to facilitate future applications in electromechanical, biomedical or energy In other fields, this is a subject that the present invention is desperately exploring.

In view of the problems of conventional techniques, the object of the present invention is to provide a microchannel electrodynamic energy conversion model and method with a high-electricity double-layer overlap effect, in which the buffer is used in a low salt concentration environment or a low microchannel height environment. Ions increase the space charge density of free ions in the microchannel while increasing the maximum energy conversion efficiency and the maximum energy output power.

According to the purpose of the present invention, the micro-channel electric energy conversion model with a high-electricity double-layer overlapping effect is a technical framework for generating electric energy by fluid kinetic energy conversion, which includes a micro-channel, an electrolyte, and a buffer solvent, and the micro-channel The channel presents a channel height h . The electrolyte exhibits a salt concentration of C _salt . , Λ _{D is} the thickness of the electric double layer in the microchannel, and ε _{f is} the dielectric constant of the electrolyte, R , T, and F are the general gas constant, the electrolyte temperature, and the Faraday constant, respectively. The electrolyte will achieve a maximum conversion energy P. The buffer solvent is an ionic solvent, which can decompose a buffer anion or a buffer cation, so as to satisfy ( h / 2) × (1 / λ _D ) Under the condition of 1, add the buffer solvent to the electrolyte with a low concentration of salt to achieve a maximum conversion power P _low , or add the buffer solvent to the electrolyte with a high concentration of salt to achieve a maximum conversion power P _high and P _low - P > P _high - P .

In addition, the buffer solvent has the effect of increasing the free ion space charge density in the microchannel to achieve the effect of simultaneously increasing the maximum energy conversion efficiency and the maximum energy output power, and the salt concentration is smaller at a certain height h The more obvious the effect.

The microchannel refers to a narrow channel composed of silicon, alumina, or a polymer film. The buffer solvent is BH or BH ⁺ ionic solvent, and the electrolyte is potassium chloride (KCl), sodium chloride, lithium chloride, or a symmetrical electrolyte.

According to another object of the present invention, the microchannel electric energy conversion method with a high-electricity double-layer overlap effect is a technical framework for generating electric energy by fluid kinetic energy conversion, which includes the following steps: setting a height of a microchannel h ; Obtained from the electrolyte salt concentration C _salt , Λ _{D is} the thickness of the electric double layer in the microchannel, and ε _{f is} the dielectric constant of the electrolyte, and R , T, and F are the general gas constant concentration, electrolyte temperature, and Faraday constant, respectively; Fill the microchannel. At this time, the electrolyte will achieve a maximum conversion energy P ; and satisfy ( h / 2) × (1 / λ _D ) Under the condition of 1, add the buffer solvent to the electrolyte with a low concentration of salt to achieve a maximum conversion power P _low , or add the buffer solvent to the electrolyte with a high concentration of salt to achieve a maximum conversion power P _high and P _low - P > P _high - P , and the buffer solvent is an ionic solvent, which can decompose a buffered anion or a buffered cation.

In addition, the buffer solvent has the effect of increasing the free ion space charge density in the microchannel to achieve the effect of simultaneously increasing the maximum energy conversion efficiency and the maximum energy output power. At a certain level of the height h , the salt concentration increases The smaller the effect, the more obvious.

The microchannel refers to a narrow channel composed of silicon, alumina, or a polymer film. The buffer solvent is BH or BH ⁺ ionic solvent, and the electrolyte is potassium chloride, sodium chloride (KCl), lithium chloride or symmetrical electrolyte.

In summary, the present invention finds that the buffer solution that is commonly added to the electrolyte, in addition to stabilizing the pH of the solution, has a significant overlap effect on EDLs, that is, a lower electrolyte salt concentration environment or a lower channel height, such as h Under the environment of 20nm, the ion system in its channel has the function of increasing the space charge density of free ions, which increases the maximum energy conversion efficiency and the maximum energy output power at the same time by 1 to 26 times. In this way, it is really beneficial to the development of renewable energy applications.

1‧‧‧ Microchannel Electric Energy Conversion Model

10‧‧‧ microchannel

11‧‧‧ Electrolyte

12‧‧‧ buffer ion

Steps S1 ~ S5‧‧‧‧

Figure 1 is a schematic diagram of a model of a preferred embodiment of the present invention.

Fig. 2 is a flowchart of a method according to a preferred embodiment of the present invention.

Fig. 3 is a charge transfer rate diagram of a preferred embodiment of the present invention.

Fig. 4 is a graph showing the experimental results of one of the preferred embodiments of the present invention.

Fig. 5 is a graph showing experimental results of the second preferred embodiment of the present invention.

Fig. 6 is a graph showing experimental results of the third preferred embodiment of the present invention.

Fig. 7 is a graph showing experimental results of the fourth preferred embodiment of the present invention.

In order to make your reviewers understand the content of the present invention clearly, please refer to the following description with drawings.

Please refer to Figs. 1 and 2 which are model diagrams and method flowcharts of the preferred embodiment of the present invention, respectively. As shown in the figure, the microchannel electric energy conversion model 1 with a high-electricity double-layer overlapping effect is a technical framework for generating electric energy by fluid kinetic energy conversion, which includes a microchannel 10, an electrolyte 11 and a buffer solvent (Figure (Not shown), and the microchannel 10 refers to an electrostatic channel on the wall surface under the condition of an aqueous solution, such as a narrow rectangular channel or a narrow cylindrical channel composed of silicon, alumina, or a polymer film. The electrolytic solution 11 may use various salts, such as potassium chloride (KC1), sodium chloride, lithium chloride, or a symmetrical electrolyte, and the buffer solvent is an ionic solvent. For example, BH or BH + ionic solvent is used. buffer or buffering anion decomposition cation, in which case a known ion buffer 12, and ^{BH → B - + H +,} BH + → B + + H +. The solvent electrolyte 11 and the buffer 10 is filled with the microchannel, such that the full H ^+, K ⁺ (or Na ^+, Li ^+), Cl 10 within the microchannel ^-, OH ^- ions and other B ^- or would BH ⁺ ions of the buffer 12, and the electric energy conversion microchannel method of constructing a model comprising at least the following steps.

In step S1, the height h of the microchannel 10 is set, and in step S2, the salt concentration C _{salt of} the electrolyte is determined to obtain , Λ _{D is} the thickness of the electric double layer in the microchannel 10, and ε _{f is} the dielectric constant of the electrolytic solution 11, R , T, and F are the general gas constant concentration, the electrolytic solution temperature, and the Faraday constant, respectively.

Next, in step S3, the microchannel is filled with the electrolytic solution. At this time, the electrolytic solution 11 will achieve a maximum conversion energy P.

Satisfy ( h / 2) × (1 / λ _D ) Under the condition of 1, in step S4, the buffer solvent is added to the electrolyte solution 11 having a low salt concentration to achieve a maximum conversion electric energy P _low , or the buffer solvent is added to the electrolyte solution 11 having a high salt concentration and A maximum conversion power P _{high is} achieved. In this way, the result of P _low - P > P _high - P can be obtained in step S5. As shown in the research results of FIG. 3 (A), when the salt concentration of the electrolytic solution 11 is 0.01 mM, the flow velocity distribution u _{p , z in} the microchannel 10 with the buffer solvent added does not change, but free ions The space charge density p _e is greatly increased and is significantly higher than the microchannel 10 without the buffer solvent added. In contrast, when the salt concentration of the electrolyte 11 is 100 mM, the free ion space charge density ρ _{e in} the microchannel 10 to which the buffer solvent is added is shown in the research result of FIG. 3 (B), which is no different from the addition of The microchannel 10 of the buffer solvent, and those skilled in the art should know that both the flow velocity distribution and the number of free ions with moving force in the microchannel 10 can affect the energy conversion efficiency and energy output power that can be obtained by the model.

For example, the height of the microchannel 10 is h = 20nm, and the buffer solvent is studied by HEPES. As shown in FIG. 4, the salt concentration of the electrolyte 11 is less than 1mM, regardless of the pH value of 6.5, 7.5, or 8.5. The maximum energy output power P _low and the maximum energy conversion efficiency η _low obtained by the model with a certain concentration, such as 5 mM of the buffer ion 12 are significantly improved, which exceeds that of the model without the buffer ion 12 added. The maximum energy output power P and maximum energy conversion efficiency η that can be obtained are about 1 to 26 times. Moreover, it is clear from the research results that when the salt concentration of the electrolyte 11 is greater than 1 mM, the maximum energy output power P _high and the maximum energy conversion efficiency η _high obtained by the model with the buffer ion 12 added are the same as those without the buffer added. There was not much difference or even worse in the ion 12.

Furthermore, the pH value of the electrolyte 11 is fixed at 7.5, and the buffer solvent is researched using HEPES. As shown in FIG. 5, when the height h of the microchannel 10 is less than 50nm, a certain concentration is added, such as 5mM. Both the maximum energy output power P _low and the maximum energy conversion efficiency η _low obtained by the model of the buffer ion 12 are significantly improved, and exceed the maximum energy output power P and the maximum energy that can be obtained by those who do not add the buffer ion 12. Conversion efficiency η ; conversely, when the height h of the microchannel 10 is greater than 50nm, taking h = 100nm as an example, because the electric double-layer overlap effect is not obvious, there is a maximum energy output power P _low obtained by the model with the buffer ion 12 added And the maximum energy conversion efficiency η _low are both significantly smaller than the maximum energy output power P and the maximum energy conversion efficiency η that can be obtained by those who do not add the buffer ion 12.

To further verify, the electrolyte solution 11 with a salt concentration of 0.1 mM and 10 mM and a pH of 7.5 was studied. As shown in FIG. 6, when the salt concentration of the electrolyte 11 is 0.1 mM, the height h of the microchannel 10 must be less than about 35 nm, and a certain concentration is added, for example, the maximum energy output obtained by the model of the buffer ion 12 at 5 mM. The power and the maximum energy conversion efficiency can exceed the maximum energy output power and the maximum energy conversion efficiency that can be obtained by those who have not been added. In contrast, when the salt concentration of the electrolytic solution 11 is 10 mM, the maximum energy output power and the maximum energy conversion efficiency that the microchannel electric energy conversion model 1 can obtain are not much different, even if the buffer ion 12 is added or not. The model with the added buffer ion 12 may perform even worse. In this way, it is known that the anion or cation decomposed by the buffer solvent can only improve the space charge of free ions in the microchannel 10 under the conditions of a lower salt concentration environment or a lower microchannel height environment, that is, under the condition that the EDLs in the model are seriously overlapped The effect of density, thereby achieving the effect of simultaneously increasing the maximum energy conversion efficiency and the maximum energy output power of electric energy.

In other words, in the case where the height of the microchannel 10 is h = 20nm and the pH value of the electrolyte 11 is fixed at 7.5, and the buffer solvent is studied using the HEPES model, as shown in FIG. 7, when the salt of the electrolyte 11 is When the concentration is small, such as 0.1 mM and 0.01 mM, the electric double-layer overlap effect in the microchannel 10 will be more obvious. At this time, if the concentration C _{Buff of} the buffer solvent increases, it can be easily found that a certain concentration of the Both the maximum energy output power P _low and the maximum energy conversion efficiency η _low obtained by the model of the buffer ion 12 are significantly improved at the same time. In addition, when the concentration of the buffer solvent is increased to about 4 mM, the above-mentioned effects of increasing the maximum energy output power P _low and the maximum energy conversion efficiency η _low will reach the extreme and it will be difficult to make a significant breakthrough. This buffer solvent was used as the reason for the study. Conversely, when the salt concentration of the electrolyte 11 is large, such as 1 mM, the electric double-layer overlap effect in the microchannel 10 is not obvious. At this time, even if the concentration of the buffer solvent increases, the maximum energy output power obtained by the model Both P _low and the maximum energy conversion efficiency η _low have no special changes, and even when the concentration of the buffer solvent is too high, both of them decrease sharply.

The above descriptions are merely exemplary preferred embodiments, but not limiting. Any equivalent modification or change made without departing from the spirit and scope of the present invention shall be included in the scope of the attached patent application.

Claims (10)

A microchannel electric energy conversion model with a high-electricity double-layer overlapping effect is a technical framework for generating electric energy by using fluid kinetic energy conversion, which includes: a microchannel, which represents a channel height h ; an electrolyte, which is filled with electricity The microchannel is obtained with a salt concentration C _salt , Λ _{D is} the thickness of the electric double layer in the microchannel, and ε _{f is} the dielectric constant of the electrolyte, R , T, and F are the general gas constant, the electrolyte temperature, and the Faraday constant, respectively. At this time, the electrolyte A maximum conversion energy P will be realized; and a buffer solvent, which is an ionic solvent, can decompose a buffer anion or a buffer cation to satisfy ( h / 2) × (1 / λ _D ) Under the condition of 1, add the buffer solvent to the electrolyte with a low concentration of salt to achieve a maximum conversion power P _low , or add the buffer solvent to the electrolyte with a high concentration of salt to achieve a maximum conversion power P _high and P _low - P > P _high - P . As described in item 1 of the scope of the patent application, a microchannel electrodynamic energy conversion model with a high-electricity double-layer overlap effect, wherein the buffer solvent has the effect of increasing the space charge density of free ions in the microchannel to achieve the maximum energy increase at the same time. energy conversion efficiency and the maximum output power efficacy, and to some extent on the height h of the more obvious the effect is smaller salt concentration.     As described in item 2 of the scope of the patent application, a microchannel electrodynamic energy conversion model with a high-electricity double-layer overlap effect, wherein the microchannel refers to a narrow channel composed of silicon, alumina, or a polymer film.     As described in item 3 of the scope of the patent application, a micro-channel electrodynamic energy conversion model with a high-electricity double-layer overlap effect, wherein the buffer solvent is a BH or BH ⁺ ionic solvent.     As described in item 4 of the scope of the patent application, a microchannel electrodynamic energy conversion model with a high-electricity double-layer overlap effect, wherein the electrolyte is potassium chloride (KCl), sodium chloride, lithium chloride, or a symmetrical electrolyte.     A microchannel electric energy conversion method with a high-electricity double-layer overlap effect is a technical framework for generating electric energy by fluid kinetic energy conversion, which includes the following steps: setting a height of a microchannel h ; determining a salt concentration C _{salt of} an electrolyte And get , Λ _{D is} the thickness of the electric double layer in the microchannel, and ε _{f is} the dielectric constant of the electrolyte, and R , T, and F are the general gas constant concentration, electrolyte temperature, and Faraday constant, respectively; Fill the microchannel. At this time, the electrolyte will achieve a maximum conversion energy P ; and satisfy ( h / 2) × (1 / λ _D ) Under the condition of 1, add the buffer solvent to the electrolyte with a low concentration of salt to achieve a maximum conversion power P _low , or add the buffer solvent to the electrolyte with a high concentration of salt to achieve a maximum conversion power P _high and P _low - P > P _high - P , and the buffer solvent is an ionic solvent, which can decompose a buffered anion or a buffered cation. The microchannel electrodynamic energy conversion method with a high-electricity double-layer overlap effect as described in item 6 of the scope of the patent application, wherein the buffer solvent has the effect of increasing the space charge density of free ions in the microchannel to achieve the maximum energy increase at the same time. The efficiency of conversion efficiency and maximum energy output power, and at a certain level of height h , the smaller the salt concentration, the more obvious the effect.     As described in item 7 of the scope of the patent application, a microchannel electrodynamic energy conversion method with a high-electricity double-layer overlap effect, wherein the microchannel refers to a narrow channel composed of silicon, alumina, or a polymer film.     The microchannel electrodynamic energy conversion method with a high-electricity double-layer overlap effect as described in item 8 of the scope of the patent application, wherein the buffer solvent is a BH or BH ⁺ ionic solvent.     The microchannel electrodynamic energy conversion method with high-electricity double-layer overlap effect as described in item 9 of the scope of the patent application, wherein the electrolyte is potassium chloride (KCl), sodium chloride, lithium chloride, or a symmetrical electrolyte.