AEROGEL-BASED FLOATABLE SELF-POWERED WATER-ELECTROLYSIS HYDROGEN GENERATION SYSTEM

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No. 10-2024-0160978 filed on Nov. 13, 2024 and Korean Patent Application No. 10-2025-0149291 filed on Oct. 16, 2025 in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. 119, the contents of which in their entireties are herein incorporated by reference.

BACKGROUND

Field

The present disclosure relates to the field of energy harvesting and hydrogen generation technology, and more particularly, to an aerogel-based floatable self-powered water-electrolysis hydrogen generation system capable of generating power in a self-powered manner using electro-osmosis in an aerogel structure floating on an electrolyte solution (for example, sea) containing ions, and of generating hydrogen using the generated power in a water-electrolysis reaction.

Description of Related Art

Recently, energy harvesting research using water has been actively conducted, and thus, various technologies for producing energy based on various principles such as water flow, water vapor (humidity) gradient, and charge rearrangement according to the migration of water droplets have been developed. These systems are not only eco-friendly because they use abundant and easily accessible resources such as water, but also have great advantages in terms of the ubiquity of energy sources. In particular, the energy harvesting scheme using water or water vapor is excellent in collecting energy that can be obtained in the natural environment by utilizing the principle of generating electrical output according to physical change.

Power generation systems based on water or water vapor are not only environmentally friendly, but also have great advantages over other energy sources in terms of energy source abundance and accessibility. Places where water can be used as an energy source can also contribute to solving the problem of ubiquity of energy sources because there are few geographical restrictions. However, there are several limitations to the current level of water-based energy harvesting technology. Typically, the amount of power generation is low, the output may be unstable, and extreme driving environments (Relative Humidity>90%) are often required. These technical limitations require improvement to a more stable and high power generation system.

The hydrogen generation system is a scheme of obtaining hydrogen by decomposing water, and may be implemented using light or electricity. A system using light may generate hydrogen with high efficiency through a photocatalytic reaction, but in this case, there is a disadvantage that the reaction is possible only when light is present during the day. Therefore, there is a disadvantage of being limited by time because it cannot be driven at night. On the other hand, the electrolysis scheme may operate without time constraints, but high current is required to stably generate hydrogen. Thus, it is highly dependent on external power. For this reason, the hydrogen generation system using electricity has high energy efficiency, but there is a limitation in that the cost burden of continuous electricity supply is large.

Therefore, in order to overcome the limitations of the conventional technology, the present disclosure intends to implement a hydrogen generation system that does not require time constraints and does not require external power.

SUMMARY

A purpose of the present disclosure is to provide a self-powered hydrogen generation system in which a floatable electro-osmotic ionovoltaic generator based on aerogel is applied to generate power using an electroosmotic phenomenon without receiving external power, and a water-electrolysis reaction is driven using the generated power.

Specifically, a purpose of the present disclosure is to provide a self-powered hydrogen generation system in which selective separation of ions and formation of an electric double layer (EDL) are induced in an electrolyte via a nanometer-sized pore network formed inside the aerogel, and thus, a stable and continuous potential difference is generated, thereby overcoming low output and instability problems of the conventional water-based energy harvesting technology.

In addition, a purpose of the present disclosure is to provide a self-powered hydrogen generation system in which the aerogel is carbonized to improve electrical conductivity, and the surface of the aerogel is subjected to fluorine-rich surface functionalization (FOTS treatment) to generate a local electric field, such that cations is attracted in a specific direction, and as a result, the formation of the electric double layer and the electo-osmosis phenomenon are maximized, thereby securing significantly improved power output compared to the conventional simple moisture-based power generation technology.

The purposes of the present disclosure are not limited to the above-mentioned purposes, and other purposes and advantages of the present disclosure that are not mentioned may be understood based on the following descriptions, and will be more clearly understood based on the embodiment of the present disclosure. In addition, it will be readily appreciated that the purposes and advantages of the present disclosure may be realized by means recited in the claims and combinations thereof.

One aspect of the present disclosure provides an aerogel-based floatable self-powered water-electrolysis hydrogen generation system comprising: an aerogel-based electric generator including an aerogel, an upper electrode disposed on top of the aerogel, and a lower electrode disposed under the aerogel; and a hydrogen generation apparatus electrically connected to the aerogel-based electric generator, wherein the aerogel has a porous structure including pores of a nanometer size, wherein while the aerogel-based electric generator is floating on an electrolyte solution containing ions, the aerogel induces separation between cations and anions through the pores and thus an electrical potential difference generation, such that the aerogel-based electric generator generates electricity using electroosmosis without receiving external power, wherein the hydrogen generation apparatus is configured to generate hydrogen via water-electrolysis using the electricity generated from the aerogel-based electric generator.

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, each of the pores of the aerogel has a size of 2 nm to 50 nm, and the pores are connected to each other to form a network structure.

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, an electric double layer (EDL) is formed by negative charges on a surface of the aerogel, and the electroosmosis phenomenon is generated by a zeta potential (ζ potential) of the formed electric double layer.

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, the aerogel is a resorcinol formaldehyde aerogel (RF aerogel).

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, the aerogel includes an aerogel carbonized to maximize the formation of the electric double layer.

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, an upper surface of the aerogel is fluorine-rich surface-functionalized using fluoroalkylsilane (FOTS) to generate a local electric field, such that the ions migrate in the pores in an upward direction under the local electric field.

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, the aerogel initially includes hydrophilic functional groups; however, these groups are decomposed and removed during the carbonization process. As a result, the aerogel surface becomes hydrophobic to ensure floatability, while the carbonization imparts electrical conductivity, allowing the locally generated electric field induced by fluorine functionalization to effectively influence the entire aerogel structure.

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, the surface of the aerogel is surface-treated with a fluorine group or a halogen group.

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, a salt is contained in the electrolyte solution, such that a cation concentration in the electrolyte solution increases and thus an output of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system is improved.

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, the aerogel-based electric generator includes a plurality of aerogel-based electric generators connected to each other.

In one embodiment of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system, the electricity generated from the aerogel-based electric generator is supplied to the hydrogen generation apparatus via an external circuit.

In the aerogel-based floatable self-powered water-electrolysis hydrogen generation system according to the present disclosure, the aerogel is carbonized to secure electrical conductivity, and a local electric field is generated by performing fluorine-rich surface-functionalization (FOTS treatment) on the upper surface thereof, thereby maximizing the formation of the electric double layer (EDL). Thus, the electroosmosis is induced in the pores inside the aerogel, and the continuous migration of cations and hydrated water molecules leads to a stable and high potential difference.

Via such structural surface area optimization, the aerogel-based electric generator of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system of the present disclosure may provide a significantly higher electrical output than the conventional water-based energy harvesting technology, and the generated power may directly drive the water-electrolysis reaction without an external power supply. Therefore, the aerogel-based floatable self-powered water-electrolysis hydrogen generation system of the present disclosure can continuously operate without time constraints, and can continuously and stably generate the hydrogen in an ion-rich electrolyte environment such as the sea. Ultimately, the aerogel-based floatable self-powered water-electrolysis hydrogen generation system of the present disclosure provides an eco-friendly and highly efficient self-powered hydrogen generation without requiring the external power, thereby having the possibility of being utilized as a next-generation clean energy supply technology.

In addition to the above-described effects, the specific effects of the present disclosure will be described together while describing specific matters for implementing the embodiments of the present disclosure below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of an aerogel-based floatable self-powered water-electrolysis hydrogen generation system according to an embodiment of the present disclosure.

FIG. 2 shows an electrical potential map showing the charge distribution of fluoroalkylsilane (FOTS) molecules.

FIG. 3 is a graph showing an output change according to a concentration change of NaCl.

FIGS. 4A to 4E are graphs showing electrical output characteristics of an aerogel-based floatable electroosmotic generator according to the present disclosure.

FIGS. 5A to 5J show surface characteristics and long-term stability of a carbonized RF aerogel (C-RF) and a fluorine surface functionalized carbonized RF aerogel (C-RF w/FOTS) according to the present disclosure.

FIGS. 6A to 6D illustrate an array of FIEGs (Floatable ion-based electric generator), an operation thereof, and output characteristics thereof, and hydrogen generation performance according to the present disclosure.

FIG. 7 is a graph showing a relationship between humidity and conductivity.

DETAILED DESCRIPTIONS

Advantages and features of the present disclosure, and a method of achieving the advantages and features will become apparent with reference to embodiments described later in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments as disclosed under, but may be implemented in various different forms. Thus, these embodiments are set forth only to make the present disclosure complete, and to completely inform the scope of the present disclosure to those of ordinary skill in the technical field to which the present disclosure belongs, and the present disclosure is only defined by the scope of the claims.

Further, descriptions and details of well-known steps and elements are omitted for simplicity of the description. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure. Examples of various embodiments are illustrated and described further below. It will be understood that the description herein is not intended to limit the claims to the specific embodiments described. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the present disclosure as defined by the appended claims.

A shape, a size, a ratio, an angle, a number, etc. disclosed in the drawings for illustrating embodiments of the present disclosure are illustrative, and the present disclosure is not limited thereto.

The terminology used herein is directed to the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular constitutes “a” and “an” are intended to include the plural constitutes as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise”, “comprising”, “include”, and “including” when used in this disclosure, specify the presence of the stated features, integers, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, operations, elements, components, and/or portions thereof.

In addition, it will also be understood that when a first element or layer is referred to as being present “on” a second element or layer, the first element may be disposed directly on the second element or may be disposed indirectly on the second element with a third element or layer being disposed between the first and second elements or layers. It will be understood that when an element or layer is referred to as being “connected to”, or “coupled to” another element or layer, it may be directly connected to, or coupled to the other element or layer, or one or more intervening elements or layers may be present therebetween. In addition, it will also be understood that when an element or layer is referred to as being “between” two elements or layers, it may be the only element or layer between the two elements or layers, or one or more intervening elements or layers may also be present.

When a certain embodiment may be implemented differently, a function or an operation specified in a specific block may occur in a different order from an order specified in a flowchart. For example, two blocks in succession may be actually performed substantially concurrently, or the two blocks may be performed in a reverse order depending on a function or operation involved.

When an embodiment may be implemented differently, functions or operations specified within a specific block may be performed in a different order from an order specified in a flowchart. For example, two consecutive blocks may actually be performed substantially simultaneously, or the blocks may be performed in a reverse order depending on related functions or operations.

The features of the various embodiments of the present disclosure may be partially or entirely combined with each other, and may be technically associated with each other or operate with each other. The embodiments may be implemented independently of each other and may be implemented together in an association relationship.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

As used herein, “embodiments,” “examples,” “aspects, and the like should not be construed such that any aspect or design as described is superior to or advantageous over other aspects or designs.

In interpreting a numerical value, the value is interpreted as including an error range unless there is no separate explicit description thereof.

Further, the term ‘or’ means ‘inclusive or’ rather than ‘exclusive or’. That is, unless otherwise stated or clear from the context, the expression that ‘x uses a or b’ means any one of natural inclusive permutations.

Further, in a specific case, a term may be arbitrarily selected by the applicant, and in this case, the detailed meaning thereof will be described in a corresponding description period. Therefore, the terms used in the description below should be understood based on not simply the name of the terms, but the meaning of the terms and the contents throughout the Detailed Descriptions.

The present disclosure relates to an aerogel-based floatable self-powered water-electrolysis hydrogen generation system. More specifically, the present disclosure provides a power generation principle in which when the aerogel contacts an electrolyte solution, an electric double layer (EDL) is formed through a nanometer-sized porous network structure inside the aerogel, and an electroosmosis phenomenon is induced in the formed electric double layer to generate an electric potential without receiving the external power, and stable and highly efficient hydrogen generation is possible by directly using the generated power in a water-electrolysis reaction.

FIG. 1 shows a schematic diagram of an aerogel-based floatable self-powered water-electrolysis hydrogen generation system according to an embodiment of the present disclosure, and FIG. 2 shows an electrical potential map showing a charge distribution of fluoroalkylsilane (FOTS) molecules.

The present disclosure relates to an aerogel-based floatable self-powered hydrogenation hydrogen generation system comprising: an aerogel-based electric generator including an aerogel, an upper electrode disposed on top of the aerogel, and a lower electrode disposed under the aerogel; and a hydrogen generation apparatus electrically connected to the aerogel-based electric generator.

The aerogel refers to a solid material having excellent properties such as high porosity, large surface area, low density, and thermal insulation. Various materials such as metal, ceramic, and polymer may be prepared in the form of an aerogel, and a representative material group of the aerogel is selected therefrom. In general, the mechanical structure of the aerogel is very suitable such that the aerogel is used as an energy harvesting material, but has a disadvantage in that it is relatively vulnerable to external force or impact. The power generation device proposed in the present disclosure utilizes a low density of the aerogel, floats on water to minimize external impact and enable stable operation of the aerogel-based power generation device.

The aerogel has a porous structure including nanometer-sized pores. The pores of the aerogel have a size of several nanometers to several tens of nanometers, and are connected to each other to form a network structure. The pore size of the aerogel is an important factor that directly affects the occurrence and efficiency of the electroosmotic phenomenon. The electroosmosis phenomenon occurs when the mobile ions migrate under the electric field in the electric double layer (EDL) of the aerogel surface. When the pore size is increased to a predetermined size or larger, the two layers of the EDL do not overlap each other along the pore wall surface, and thus the entirety of the internal fluid is not affected by the electric field. As a result, the electroosmotic flow is not sufficiently generated or the output of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system is rapidly reduced. Therefore, in accordance with the present disclosure, it is essential to maintain a nanometer-sized fine pore structure in order to stably generate the electroosmosis. The pore size is in a range of 2 to 50 nm, preferably, 2 to 20 nm. In general, the higher the electrolyte concentration (e.g., seawater environment), the smaller the thickness of EDL, and thus, the surface of the aerogel that has undergone the carbonization process changes to being hydrophobic such that the EDL tends to be thinner. For this reason, in order for the aerogel-based floatable self-powered water-electrolysis hydrogen generation system of the present disclosure to stably maintain the electroosmosis even in a high ion concentration environment such as seawater, the pore size of the aerogel is preferably limited to a maximum of 50 nm. In order to more stably maintain the electroosmosis, the pore size of the aerogel may be 20 nm smaller. When the pore size is too small, that is, smaller than 2 nm, the pores are closed during the manufacturing process or the migration of the hydrated ions is limited, so that the electroosmosis does not occur. In addition, due to the characteristics of the synthesis and carbonization process of the RF aerogel, it is difficult to reproducibly prepare ultra-fine pores of the size smaller than 2 nm, and it becomes impossible to form a continuous network structure for ion migration. On the other hand, when the pore size exceeds 20 nm and becomes excessively large, the influence of the EDL formed in the aerogel surface does not reach the center of the pore. As a result, the electric field is not uniformly distributed inside the pores, and the electroosmotic flow does not occur in the neutral region other than the EDL region. In addition, as the pores become larger, it becomes more difficult to achieve the selective migration of cations and anions, and the separation between cations and anions is not achieved, thus making it impossible to generate the electrical potential. For this reason, when the pore size exceeds 20 nm, the electroosmotic efficiency is rapidly reduced, and the output voltage and current density are reduced. Therefore, in accordance with the present disclosure, the pore size is preferably set to about 2 to 20 nm.

The network structure in which the pores are connected to each other does not mean that a plurality of pores inside the aerogel are present as separate independent pores, but refers to a state in which the pores are connected to each other to form an effective flow path continuously extending along a thickness direction. This network structure does not mean one straight through channel. A plurality of maze type or branched passages are intertwined with each other such that an entirely continuous percolating cluster is formed so that the ions and water molecules can substantially migrate from the lower surface to the upper surface. In such a network, the electric double layer may be continuously formed along the wall surface of each pore, and the electroosmotic flow continues without interruption when the internal electric field is applied thereto, such that the separation between cations and anions and thus the potential difference generation are realized.

The network structure in which the pores are connected to each other is implemented by a manufacturing process. For example, the gelling and drying conditions and the carbonization conditions of the RF aerogel are adjusted to form open cells of a nanometer scale, and the size of the template, a concentration, and a removal condition are adjusted as necessary to secure continuity between the pores. When a continuous flow path extending in the thickness direction is developed under such process control, a path through which the ions and water molecules substantially migrate from the lower surface to the upper surface of the aerogel in the electrolyte environment is provided, the electric double layer is continuously formed along the path, and the electroosmotic flow is maintained seamlessly under the internal electric field.

In summary, the power generation device of the present disclosure may generate energy by itself without receiving external power using the aerogel floating on the electrolyte solution rich in ions like the sea. In this case, the nanometer-sized porous pores of the aerogel provide a passage through which the ions and water molecules in the electrolyte solution flow, and the electroosmosis phenomenon occurs inside the pores. Thus, the electroosmosis phenomenon occurs when the mobile ions migrate under the electric field in the electric double layer (EDL) formed by negative charges of the surface of the aerogel. Specifically, while the aerogel surface is negatively charged, the negatively charged surface attracts the positive ions (H⁺, Na⁺ and the like) from the surrounding electrolyte solution to form the EDL. Thus, the negative zeta potential may be generated to provide the basis for electroosmosis. In addition, as will be described later, the fluorine group introduced onto the upper surface may induce the local electric field inside the aerogel due to the high electronegativity thereof, and this local electric field attracts the mobile cations present in the EDL inside the pores in a specific direction. While the ions is migrating in the hydrated state, the ions may allow the surrounding water molecules to flow together with the migration thereof and as a result, the forward flow of the ions and water from the lower portion to the upper portion of the aerogel occurs, and in this process, the electrical potential difference is generated between the upper and lower electrodes on top of and under the aerogel.

The representative aerogel in accordance with the present disclosure is resorcinol formaldehyde (RF) aerogel. The RF aerogel is a representative polymer aerogel, and is enriched with —OH (hydroxyl group) as a hydrophilic functional group capable of interacting with water molecules. During operation, cations in the electrolyte are attracted and transported along the aerogel surface through electroosmotic phenomena, thereby generating a potential difference across the aerogel structure.

In the present disclosure, in order to increase the amount of power generation, it is necessary to maximize the formation of the electric double layer, and thus two post-treatments may be applied to the aerogel in order to increase the mobility of ions.

First, conductivity may be increased by carbonizing the aerogel. Compared to the pristine RF aerogel, the carbonized RF aerogel has a higher mobility of ions, thereby forming a conductive path. In addition, the carbonized aerogel has an advantage of being structurally stable because mechanical strength thereof is very good.

Next, in order to maximize the formation of the electric double layer, a surface treatment such that the surface is capable of attracting cations may be performed. The surface treatment may include a surface treatment with a halogen functional group. When the aerogel surface is treated with a material having a high electronegativity such as fluorine which has a strong property of attracting the cations, a greater amount of the cations (H⁺ (proton) or H⁺ in water, and Na⁺ (when ions are dissolved in water)) can be selectively attracted by the surface. In addition, when the fluorine group binds to the surface of the aerogel, the surface exhibits hydrophobicity and thus the aerogel is able to float on the water more stably. Specifically, the upper surface of the aerogel is subject to fluorine-rich surface functionalization using fluoroalkylsilane (FOTS) to generate the local electric field, and thus, the ion migration in an upward direction inside the pores may be induced.

In one example, the aerogel may undergo carbonization to acquire electrical conductivity and a hydrophobic surface that enables floatability on the electrolyte. In this case, the surface of the aerogel may be further treated with a fluorine group or a halogen group, which induces a localized electric field across the conductive aerogel structure. This localized field allows cations in the electrolyte to migrate along the aerogel surface through electroosmotic phenomena, thereby generating a potential difference.

Representative surface modification groups include a fluorine group (—F), a chlorine group (—Cl), and other halogen-based functional groups that can induce localized polarization on the aerogel surface. The aerogel including such surface-modified structures can maintain floatability while facilitating ion migration and potential generation during the self-powered water electrolysis process.

• • 1) Metal oxide-based aerogel (gold, platinum, palladium, titanium dioxide, cobalt, nickel, iron, copper, etc.)
  • 2) Ceramic-based aerogel (silica, zirconia, titania, zirconium oxide, magnesium oxide, aluminum oxide, etc.)
  • 3) polymer-based aerogel (polyvinyl alcohol, polyurethane plate, polyimide, cellulose, chitosan, agarose, etc.)
  • 4) Carbon-based aerogel (carbon nanotube, graphene, activated carbon, carbon fiber, etc.)

The upper electrode and the lower electrode are disposed on top of and under the aerogel, respectively.

The lower electrode of the aerogel-based electric generator disposed under the aerogel is located in the water to allow the H⁺ ions in the water to be introduced into the aerogel, thereby forming an ion concentration gradient. The H⁺ introduced from the water migrates upwards under the concentration gradient, and thus the electrical current is generated in this process.

The upper electrode of the aerogel-based electric generator located on top of the aerogel is exposed to the air. The current flows from the upper electrode through the external circuit to the hydrogen generation apparatus to maintain the balance of charges. The upper electrode together with the lower electrode serves to maintain the ion flow and promote the water-electrolysis reaction.

The H⁺ ions in contact with the lower electrode migrate upwards under the concentration gradient to generate the electrical current. The current provides the electrical energy to sustain the water-electrolysis reaction. In addition, an electrical potential difference is generated between the upper electrode and the lower electrode, so that the current flow is continued, thereby allowing the hydrogen generation reaction to occur in the self-powered manner.

In one example, the salt is contained in the electrolyte solution, such that the cation concentration therein increases, and thus the output of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system may be improved. For example, when the salt such as NaCl is dissolved ion the electrolyte solution, the amount of cations increases, so that the output of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system may be improved compared to a case in which the electrolyte solution is deionized water. FIG. 3 is a graph showing an output change according to a concentration change of NaCl.

In the aerogel-based floatable self-powered water-electrolysis hydrogen generation system of the present disclosure, the aerogel-based electric generator is connected to the hydrogen generation apparatus, such that the power generated from the aerogel-based electric generator is supplied to the hydrogen generation apparatus, so that the apparatus may generate hydrogen in the water-electrolysis manner. That is, the aerogel-based electric generator may be used as an auxiliary power device for the hydrogen generation apparatus. In summary, the current generated in the self-powered manner is supplied to the hydrogen generation apparatus using the water-electrolysis, thereby reducing overall external power consumption and increasing the efficiency of the aerogel-based floatable self-powered water-electrolysis hydrogen generation system. The aerogel-based electric generator as an independent power generation device is present separately from the hydrogen generation apparatus using the water-electrolysis, and acts as an independent auxiliary power device that generates additional power required to promote the water-electrolysis reaction, thereby providing a power saving effect.

A plurality of aerogel-based electric generators acting as the auxiliary power devices may be disposed. The plurality of aerogel-based electric generators may be connected to each other in series or in parallel manner each other.

Hereinafter, the contents of the present disclosure will be additionally described together with a specific Example.

Example 1

In the present disclosure, electric power can be self-generated through an FIEG working mechanism (Electro-osmotic separation between cations and anions). In this case, the electrolyte penetration+EDL formation according to surface charge+internal electric field generation due to FOTS simultaneously acts inside the pores of the aerogel, such that mobile ions migrate along the electric field direction. At this time, the hydrated ions together with the water molecules migrate to form a forward flow, and an electrical potential difference is generated between the upper and lower electrodes under this flow.

The specimen used in the Example was prepared by synthesizing the Resorcinol-Formaldehyde (RF) aerogel and carbonizing the same in the 800 to 1000° C. range to impart electrical conductivity. Thereafter, the upper surface of the carbonized aerogel was treated with fluoroalkylsilane (FOTS) vapor to perform fluorine-rich surface-functionalization. A finally obtained specimen had an average pore size in the range of about 2 to 20 nm, and it was identified via BET analysis and SEM observation that the porous network structure was formed.

The measurement was performed while the specimen was floating on each of the artificial seawater (3.5 wt % NaCl aqueous solution) and natural seawater. The temperature of the electrolyte solution was maintained at 25±2° C., and the pH of the solution was adjusted to about 7.5 to 8.0.

The electrode arrangement was made in such a way that a carbon electrode or an Pt auxiliary electrode was disposed under the aerogel, and a Ag/AgCl reference electrode was disposed on top of the aerogel, and a distance between the electrodes was maintained at about 1 cm. Thus, the aerogel-based electric generator was manufactured.

The electrical output of the aerogel-based electric generator was measured in real time using a potentiometer and an ammeter. In addition, regarding the FEM analysis, the electric potential distribution was calculated using COMSOL Multiphysics. Power density was calculated from the current-voltage curve measured while varying the external load resistance in a range from several kΩ to several MΩ ranges. The long-term stability was evaluated based on a recording result of a voltage change while continuously operating the aerogel-based electric generator for about 6000 seconds (1 hour and 40 minutes) or greater.

FIGS. 4A to 5E are graphs showing electrical output characteristics of the aerogel-based floatable electroosmotic generator according to the present disclosure.

FIG. 4A illustrates an electrical potential distribution (A). This shows a FEM (finite element analysis)-based simulation result that indicates the distribution of the electrical potential generated when the aerogel (FIEG) floats on the seawater. It may be identified that the electrical potential difference is generated between the upper and lower surfaces of the aerogel, and the electric field is stably distributed inside the pores.

FIG. 4B illustrates an in-situ electrical output and an in-situ electrical output. The voltage output result and the current output result measured in the actual seawater environment are shown in FIG. 4B. It is identified based on a periodically repeated signal that the generator stably generates the electrical current, and a stable signal appears like the current output, and it is proved that a stable electrical potential difference is generated even when the generator floats on the seawater

FIG. 4C illustrates a result of the electrical output under light/dark conditions. The output based on the absence or absence of the light (with or without lighting) is shown therein, and the output is maintained in both bright and dark environments, thereby indicating that the power generation principle is not light-dependent and is based on the electroosmosis.

FIG. 4A illustrates an optimal power density. The output characteristics measured while changing the external load condition is shown. The relationship between the current density (mA/cm²) and the output density (mW/cm²) is shown. It is identified that the maximum output density (about 0.3 to 0.4 mW/cm²) is obtained under a specific load condition.

FIG. 4E shows a graph of voltage output stability measured over a long period of time (thousands of seconds or greater). The voltage is kept constant for a long time after the initial stabilization. Thus, it may be identified that the power generator of the present disclosure operates stably even in an actual use environment.

The generator according to the present disclosure may generate the potential difference on its own without relying on an external power source. It has been identified that the output power per unit area of the generator reaches about 0.3 to 0.4 mW/cm². This corresponds to an improved output characteristic of about twice or greater of that of the conventional moisture gradient-based power generation system or a simple humidity-driven power generation device. Thus, the generator according to the present disclosure maintains a constant output even in a floating state for a long time. In addition, the stable potential is maintained in a continuous operation test of 6000 seconds or larger. Thus, it has been proved that the generator of the present disclosure can reliably operate even in a long-term actual use environment.

Example 2

FIG. 5 shows surface characteristics and long-term stability of each of a carbonized RF aerogel (C-RF) and a fluorine surface functionalized carbonized RF aerogel (C-RF w/FOTS) according to the present disclosure.

The Resorcinol-Formaldehyde (RF) aerogel was synthesized, and carbonized in the range of 800 to 1000° C. to impart electrical conductivity. Thus, the specimen (C-RF) was prepared. Some specimens were subjected to fluoroalkylsilane (FOTS) vapor treatment to perform fluorine-rich surface functionalization (C-RF w/FOTS) thereon. About 5 μL of water droplets was dropped onto the surface of the specimen and then the surface was photographed with a high-speed camera and the surface image was analyzed. Thus, a contact angle was measured based on the analysis. The evaluation of the flotation stability on the seawater was performed in a manner of long-term observation while the specimen was maintained at a temperature of 25±2° C. while the specimen was floating on the artificial seawater (3.5 wt % NaCl solution). The stability thereof was identified based on a comparing result of the specimen changes of Day 0 and Day 30.

FIG. 5A shows the water contact angle of the untreated RF aerogel, and indicates that the water droplets are immediately absorbed and the contact angle is not formed because the surface is hydrophilic. FIG. 5B shows the contact angle of the carbonized RF (C-RF), and it may be identified that the water repellency increases according to carbonization treatment, and thus a constant contact angle is formed. FIG. 5C shows a contact angle of the fluorine surface functionalized carbonized RF (C-RF w/FOTS), and it may be identified that superhydrophobicity corresponding to the contact angle of about 150° or greater occurs as the fluorine-rich surface-functionalization is performed on the surface. FIG. 5D is a graph showing the temporal change of the contact angle for each specimen, and it may be identified that the water is rapidly absorbed by the RF over time, whereas the C-RF maintains a constant contact angle over time, and C-RF w/FOTS stably maintains a great contact angle for a long time. FIG. 5E shows a contact angle image measured on the upper surface of C-RF w/FOTS, and indicates that a very great contact angle is formed on the fluorine-rich surface. FIG. 5F shows a lower surface contact angle of the same specimen, and indicates that the lower surface contact angle is smaller than the upper surface contact angle, and thus, the upper and lower asymmetric wettability is realized. FIG. 5G is an image of an untreated RF specimen placed on water, and it may be identified that water is rapidly absorbed thereby and the specimen is submerged therein. FIG. 5H shows an image of the carbonized RF (C-RF) specimen, and it may be identified that water repellency increases, so that it is initially floating on the water, but lacks long-term stability. FIG. 5I is an image showing comparing the changes of Day 0 and Day 30 after the C-RF w/FOTS specimen floats on the artificial seawater with each other, and indicates that the functionalized specimen floats thereon stably for 30 days and no water absorption or structural damage occurs. FIG. 5J is a graph showing the contact angle hysteresis of C-RF w/FOTS, and it may be identified that the difference between advancing and receding contact angles is small, so that the surface exhibits uniform superhydrophobic characteristics.

Example 3

FIG. 6 illustrates an array of FIEGs (Floatable ion-based electric generator), an operation thereof, and output characteristics thereof, and hydrogen generation performance according to the present disclosure.

The RF aerogel was synthesized and carbonized in the range of 800 to 1000° C. to impart electrical conductivity, and the upper surface thereof was subjected to fluorine-rich surface-functionalization using fluoroalkylsilane (FOTS) vapor treatment. The single FIEG device manufactured in this way had a size of 1 cm in width×1 cm in length×several mms in thickness. The FIEG devices as the aerogel-based electrical power generators are arranged in a 3×3 array to manufacture an array of a total of nine devices. The output characteristics of the array were measured in real time while the array was floating on the artificial seawater (3.5 wt % NaCl solution).

FIG. 6A shows a photograph of an array produced by arranging nine FIEG devices, and indicates that each device can be independently driven and the devices are connected to each other in series or in parallel with each other to adjust the output characteristics of the array. A left graph in FIG. 6B is a graph showing output characteristics of the array when the devices are connected to each other in a series manner, and it may be identified that as the number of devices increases, the voltage linearly increases, while the current is maintained at a certain level. In addition, a right graph in FIG. 6B is a graph showing the output characteristics of the array when the devices are connected to each other in a parallel manner, and indicates that as the number of devices increases, the current greatly increases and the voltage remains constant. FIG. 6C is a graph showing the results of hydrogen generation (HER) and oxygen generation (OER) for 24 hours, and indicates that hydrogen and oxygen are stably generated over time, and at the same time, the yield is changed according to the solar intensity. The amount of hydrogen as generated is larger than two times of the amount of oxygen as generated, thus indicating that the electrode reaction is stably progressing. FIG. 6D is a bar graph comparing the amounts of generated hydrogen and oxygen accumulated after a 24 hours reaction with each other, and indicates that the amount of hydrogen as generated is maintained at a higher value than that of the amount of oxygen as generated. This demonstrates that the FIEG-based self-powered water-electrolysis system of the present disclosure can stably produce hydrogen for a long time.

Meanwhile, the aerogel-based floatable self-powered water-electrolysis hydrogen generation system according to the present disclosure exhibits excellent performance in an environment such as a sea with high humidity, and maintains a constant output without being affected by external factors while floating on the water.

If the water evaporation is an important factor in the ion migration in the relationship between the humidity and the output, it may be expected that the output will decrease as the humidity increases. However, the actual experimental results indicate that the humidity and the output tend to be proportional to each other. This indicates that the higher the humidity, the easier the migration of internal ions, and the output increases, thanks to the aerogel containing the moisture. FIG. 7 is a graph showing a relationship between humidity and conductivity. In the conductivity experiment according to humidity change in FIG. 7, the respective electrical conductivities of the aerogel under the conditions of 20% and 90% of relative humidity (RH) were compared with each other. As a result, it was identified that the conductivity of the aerogel was higher under the 90% RH condition. This is because a larger amount of the moisture is absorbed into the aerogel at the high humidity, and the migration path of the ions becomes smoother.

The aerogel-based floatable self-powered hydrogenation hydrogen generation system of the present disclosure has excellent long-term operation capability and may maintain constant output performance for a long time. Due to its stable operation in the high humidity environments, continuous energy harvesting is possible in external environments such as the sea and rivers.

Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, the present disclosure may not be limited to the embodiments and may be implemented in various different forms. Those of ordinary skill in the technical field to which the present disclosure belongs will be able to appreciate that the present disclosure may be implemented in other specific forms without changing the technical idea or essential features of the present disclosure. Therefore, it should be understood that the embodiments as described above are not restrictive but illustrative in all respects.