Ant acid generation device

Abstract

A formic acid generator capable of efficiently irradiating a reaction solution with light and improving the efficiency of formic acid generation is provided. [Solution] The formic acid generator 50 is equipped with a raw material input section 10 into which a solution containing organic substances and metal oxide powder having photocatalytic function are input, an artificial photosynthesis reaction section 20 which irradiates the mixed solution of organic substances and metal oxide powder with sunlight or light to cause a reaction, and a formic acid recovery section 30 which recovers formic acid from the mixed solution after the reaction, wherein the artificial photosynthesis reaction section 20 is a plate-shaped container made of a light-transmitting material, at least the surface onto which light is irradiated, and the container is inclined with respect to the ground surface, and an artificial photosynthesis reaction is carried out by flowing the mixed solution inside the container.

Description

[Technical field]

[0001] The present invention relates to a formic acid generator that generates formic acid from an organic substance by utilizing sunlight. [Background technology]

[0002] The idea of ​​a "hydrogen society" that uses hydrogen as fuel has been proposed for some time, but it is difficult to say that it has become widespread even now due to the difficulty of storing and transporting hydrogen and the energy conversion efficiency. For example, to transport hydrogen, which has a low energy density, as a fuel for automobiles, it is necessary to apply high pressure of several hundred atmospheres. There is a method to make liquid hydrogen, but it is not common because it requires ultra-low temperatures. Therefore, technology is being researched to generate and store formic acid (HCOOH) as an intermediate hydrogen source. Formic acid is an excellent storage material because it is liquid at room temperature and has a high energy density.

[0003] Utilizing sunlight as a natural energy source to produce highly active organic compounds from relatively stable organic substances is an important technology that humanity should acquire now in many fields, from pharmaceutical manufacturing to transportation fuels and power generation, and there is a strong demand for the establishment of such artificial photosynthesis methods and for more efficient yields.

[0004] In light of this situation, there is a need to provide a low-cost means for using solar energy to produce formic acid, which can be converted relatively easily into hydrogen as chemical energy and is a chemical substance useful to mankind.

[0005] The applicants have previously proposed a formic acid generating method and a formic acid generating system, which are described in Patent Document 1. The invention described in Patent Document 1 is a formic acid generating method characterized in that a solution containing an organic substance is mixed with a metal oxide powder having a photocatalytic function to prepare a mixed solution, and formic acid is generated by irradiating the mixed solution with light.

[0006] Even after proposing the invention described in Patent Document 1, the applicants have been working diligently to further improve the amount of formic acid produced. For example, the invention described in Patent Document 1 proposes a light-transmitting tubular or cylindrical member of any shape that is laid on the roof or rooftop of a building and circulates a mixed solution within the member to perform an artificial photosynthesis reaction. However, it was found that the sunlight is almost entirely absorbed near the liquid surface of the solution, and sufficient sunlight does not reach the inside of the solution, so that the formic acid production reaction does not occur sufficiently. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 7076113 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a formic acid generator that can efficiently irradiate a reaction solution with light and improve the efficiency of formic acid production. [Means for solving the problem]

[0009] One aspect of the present invention includes a raw material input section for inputting a solution containing an organic substance and a metal oxide powder having a photocatalytic function, an artificial photosynthesis reaction section for irradiating the mixed solution of the organic substance and the metal oxide powder with sunlight or light to cause a reaction, and a formic acid recovery section for recovering formic acid from the mixed solution after the reaction, wherein the artificial photosynthesis reaction section is a plate-shaped container having at least a surface to be irradiated with light formed of a light-transmitting material, and the container is inclined with respect to the ground surface, A nozzle is provided inside the container located on the upstream side of the incline to spray the mixed solution toward the inside of a light-transmitting member attached to the top surface, and the sprayed mixed solution is configured to flow downstream due to the incline while adhering to the underside of the light-transmitting member due to the surface tension of the member. By The inner surface of the light-transmitting member can always have the solution attached thereto, and the sunlight is not blocked due to the solution attached thereto as the surface of the member dries. Therefore, the liquid surface of the mixed solution absorbs almost all of the sunlight. Artificial photosynthetic reaction Efficiently The formic acid generating apparatus is characterized by carrying out the above-mentioned process.

[0010] According to one aspect of the present invention, by supplying a reaction solution into an inclined plate-like container, the reaction solution can be efficiently irradiated with light while flowing at a moderate speed, resulting in a formic acid generator with improved formic acid production efficiency.

[0012] By doing this, the reaction solution that adheres to the top surface of the container due to surface tension spreads widely and thinly throughout the container, allowing the reaction solution to be efficiently irradiated with light and improving the efficiency of formic acid production.

[0017] In addition, in one aspect of the present invention, the formic acid recovery section may include equipment for recovering and cooling the gas phase of the mixed solution after the reaction, so that formic acid is recovered as a liquid by reflux.

[0018] In this way, it becomes possible to separate formic acid at a high concentration from the mixed solution after the reaction.

[0019] In one aspect of the present invention, the apparatus may further include an air supplying means for supplying air to the mixed solution.

[0020] By appropriately supplying air to the mixed solution by the air supply means, oxygen necessary for the formic acid production reaction is supplied, and the efficiency of formic acid production can be improved.

[0021] In addition, in one aspect of the present invention, a control unit may be provided that can continuously measure the amount of formic acid produced in real time by measuring the electrical conductivity and temperature of the mixed solution and graphing the relationship between the formic acid concentration and the electrical conductivity in advance.

[0022] By providing such a control unit, it becomes possible to remotely operate and control the formic acid production device.

[0023] In one aspect of the present invention, the light-transmitting member is In order to effectively attach the mixed solution to the lower surface of the optically transparent member, It may also be embossed glass.

[0024] In one embodiment of the present invention, the angle that the inclination makes with the horizontal plane may be greater than or equal to 10° and less than or equal to 15°.

[0025] In one embodiment of the present invention, the organic substance may include glucose, and the photocatalytic function may include titanium oxide fine particles. Effect of the Invention

[0026] As described above, according to the present invention, it is possible to provide a formic acid generator that can efficiently irradiate a reaction solution with light and improve the efficiency of formic acid production. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a formic acid generating apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing one embodiment of an artificial photosynthesis reaction unit in a formic acid production device according to one embodiment of the present invention, in which (A) is a front view of the artificial photosynthesis reaction unit, and (B) is a cross-sectional view taken along line AA in (A). [Diagram 3] FIG. 2 is a cross-sectional view showing one mode of supplying a reaction solution in an artificial photosynthesis reaction section of a formic acid production device according to one embodiment of the present invention. [Figure 4] FIG. 11 is a cross-sectional view showing another aspect of the supply of a reaction solution in the artificial photosynthesis reaction section of the formic acid production device according to one embodiment of the present invention. [Diagram 5] FIG. 11 is a cross-sectional view showing another aspect of the supply of a reaction solution in the artificial photosynthesis reaction section of the formic acid production device according to one embodiment of the present invention. [Figure 6] 1 is a graph showing the amount of formic acid produced in an example in which one aspect of the present invention is applied and in a comparative example of the prior art. [Figure 7] 1 is a graph showing the amount of formic acid produced in an example when one embodiment of the present invention is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below do not unduly limit the content of the present invention described in the claims, and all of the configurations described in the embodiments are not necessarily essential as the means for solving the problems of the present invention.

[0029] 1 is a schematic diagram showing an example of a formic acid generating apparatus according to an embodiment of the present invention. One aspect of the present invention is a formic acid generating apparatus 50 including a raw material input section 10 for inputting a solution containing an organic substance and a metal oxide powder having a photocatalytic function, an artificial photosynthesis reaction section 20 for irradiating a mixed solution of an organic substance and a metal oxide powder with sunlight or light to cause a reaction, and a formic acid recovery section 30 for recovering formic acid from the mixed solution after the reaction, and the artificial photosynthesis reaction section 20 is a plate-shaped container formed of a light-transmitting material on at least the surface to which light is irradiated, the container is inclined with respect to the ground surface, and the mixed solution is flowed inside the container to perform an artificial photosynthesis reaction.

[0030] The mixed solution is preferably circulated and supplied to the artificial photosynthesis reaction unit 20 via, for example, a pump 45. While the mixed solution is circulated by the pump 45, formic acid is generated in the artificial photosynthesis reaction unit 20, the formic acid is recovered in the formic acid recovery unit 30, and while the reaction solution is appropriately supplied to the raw material input unit 10, formic acid is repeatedly generated by the artificial photosynthesis reaction. Each configuration of the present invention will be described below.

[0031] The raw material input section 10 is a facility for inputting a solution containing an organic substance and a metal oxide powder having a photocatalytic function. The organic substance is not particularly limited as long as it contains carbon atoms. The organic substance is preferably one containing a pigment that plays a role in assisting the photoreaction, but organic substances without a pigment are also applicable. For example, inositol (a type of vitamin B group) and glucose (glucose, the monosaccharide most abundant in nature) have a formic acid production rate ratio equivalent to that of anthocyanin B (a pigment contained in purple cabbage). In addition, disaccharides and polysaccharides such as dextrin, cellobiose, and cellulose, which have a lower formic acid production rate than anthocyanin B, are also applicable to the present invention.

[0032] The organic matter may be plants, fallen leaves, vegetables, fruits, etc. If waste plants such as fallen leaves and waste food such as food waste are used as raw materials for producing formic acid, an environmentally friendly formic acid producing device can be realized.

[0033] The organic substance preferably contains a pigment that plays a role in assisting the photoreaction. The pigment may be a combination of green pigment, gardenia red, and mercurochrome, which can improve the rate of formic acid production. Alternatively, carbon powder may be used instead of the pigment. Activated carbon powder, for example, is used as the carbon powder. Of course, the present invention can be applied to organic substances without pigments.

[0034] The metal oxide powder is not particularly limited as long as it has a photocatalytic function. In particular, it is preferable to use titanium oxide or zinc oxide. These metal oxides are preferably in the form of fine particles in order to increase the contact surface area in the mixed solution. The average particle size of the fine particles is not particularly limited, but is, for example, 20 to 50 nm. In particular, it is preferable that the average particle size of titanium oxide fine particles is about 25 nm. Among titanium oxides, anatase type is preferable because it shows about 10 times higher activity than rutile type.

[0035] The raw material input unit 10 is, for example, a tank-shaped facility that appropriately supplies raw materials to the artificial photosynthesis reaction unit 20. The solution containing the organic substance and the metal oxide powder having a photocatalytic function may be mixed in advance, or may be stored separately and mixed when the raw materials are supplied and supplied onto the path to the artificial photosynthesis reaction unit 20. Alternatively, instead of a tank-shaped facility, the raw materials may be sent from a generation source or production source of the organic substance through piping or the like.

[0036] The artificial photosynthesis reaction unit 20 is a facility that irradiates a mixed solution of an organic substance and a metal oxide powder with sunlight or light to cause a reaction. In one aspect of the present invention, the artificial photosynthesis reaction unit 20 is a plate-shaped container in which at least the surface to be irradiated with light is made of a light-transmitting material, and the container is installed at an angle to the ground surface.

[0037] FIG. 2 is a diagram showing one embodiment of an artificial photosynthesis reaction unit in a formic acid generator according to an embodiment of the present invention, in which FIG. 2(A) is a front view of the artificial photosynthesis reaction unit, and FIG. 2(B) is a cross-sectional view taken along line AA in FIG. 2(A). As an example, the artificial photosynthesis reaction unit 20 can have a plate-like structure in which a light-transmitting member 22 is installed at a certain interval on a panel 21 that serves as the bottom surface, as shown in FIG. 2(B). The bottom panel 21 may or may not have light transmittance, and may be, for example, a concrete panel. On the other hand, it is preferable to use a member such as reinforced glass that has light transmittance for the surface that receives sunlight. The distance between the panel surface 21 and the glass surface 22 may be adjusted by forming a wall surface with a frame material 23 or the like on the edge of the panel, and adjusting the height of the frame material 23.

[0038] In one embodiment of the present invention, a nozzle installation hole 24 and the like are provided near the upstream end of the inclined panel. In one embodiment of the present invention, a reaction solution (mixed solution) is supplied from a nozzle provided in the installation hole 24. In FIG. 2, the nozzle installation hole 24 is only one, but it may be provided in multiple places. Alternatively, a liquid supply pipe may be installed near the upstream end of the inclined panel, and mixed solution injection ports may be provided at multiple places on the liquid supply pipe. In one embodiment of the present invention, a discharge hole (drain hole) 25 for the post-reaction solution is provided near the downstream end of the inclined panel. Therefore, the reaction solution is supplied from a nozzle near the upstream end of the inclined panel, and as it flows along the inclination of the panel, it receives light such as sunlight from the glass surface and undergoes an artificial photosynthetic reaction, and the post-reaction solution is discharged from the discharge hole 25.

[0039] The inventors discovered that in the formic acid production reaction using sunlight, almost all of the sunlight (99% or more) is absorbed at a depth of the liquid surface (about 1 mm) of the mixed solution. In other words, in the method of circulating the sunlight inside a tubular pipe as in Patent Document 1, only the solution near the surface of the tube receives the irradiation energy of the sunlight, and sunlight does not sufficiently reach the solution inside, which is thought to be why the efficiency of formic acid production is insufficient.

[0040] Therefore, in one embodiment of the present invention, by supplying the reaction solution into an inclined plate-like container, the entire reaction solution can be irradiated with sunlight, and a formic acid generating device with improved formic acid generation efficiency can be obtained. The angle of inclination is not particularly limited as long as the mixed solution can flow at an appropriate speed, but as an example, it can be 10 to 15 degrees with respect to the horizontal plane.

[0041] There are several possible modes for the method of supplying the reaction solution in the artificial photosynthesis reaction unit 20. Fig. 3 is a cross-sectional view showing one mode of supplying the reaction solution in the artificial photosynthesis reaction unit of a formic acid production device according to one embodiment of the present invention.

[0042] In one embodiment of the present invention, as shown in FIG. 3, the artificial photosynthesis reaction unit 20 is provided with a nozzle 15 that sprays the mixed solution onto the upper surface inside the container located on the upstream side of the incline, and the sprayed mixed solution 55 can be configured to flow downstream due to the incline while adhering to the inside of the upper surface 22 of the container due to surface tension. In this way, the reaction solution 55 that adheres to the upper surface 22 of the container due to surface tension spreads widely and thinly throughout the entire container, so that the reaction solution 55 can be efficiently irradiated with light, and the formic acid production efficiency can be improved. In addition, the embodiment of FIG. 3 can also prevent the upper surface inside the container from becoming cloudy due to water vapor.

[0043] 3, the nozzle 15 is disposed so that the nozzle orifice faces the upper surface and sprays the solution onto the back surface (the surface facing the inside of the container) of a light-transmitting member (such as glass). The solution-receiving surface of the light-transmitting member 22 may be embossed or otherwise processed so that a large amount of solution can be attached by surface tension.

[0044] FIG. 4 is a cross-sectional view showing another aspect of the supply of the reaction solution in the artificial photosynthesis reaction section of the formic acid generating device according to one embodiment of the present invention. In another aspect of the present invention, as shown in FIG. 4, the artificial photosynthesis reaction section 20 may be configured to include a nozzle 15 for flowing the mixed solution on the bottom surface inside the container located on the upstream side of the incline, and the mixed solution 55 may be configured to flow downstream along the incline on the bottom surface 21 of the container. By flowing the reaction solution from the upstream to the bottom surface, the reaction solution can be spread widely and thinly throughout the entire area, so that the reaction solution can be efficiently irradiated with light, and the formic acid generation efficiency can be improved. In addition, in the aspect of FIG. 4, the liquid delivery pressure of the pump 45 or the like may be relatively small.

[0045] In the case of the embodiment shown in Figure 4, the nozzle outlet only needs to be directed toward the panel on the bottom of the container, and there is no need to spray with any particular force. The mixed solution will slide down the slope of the panel due to gravity, and during this time a photoreaction will occur due to sunlight or other factors.

[0046] 5 is a cross-sectional view showing another aspect of the supply of the reaction solution in the artificial photosynthesis reaction unit of the formic acid generating device according to one embodiment of the present invention. In another aspect of the present invention, as shown in FIG. 5, the artificial photosynthesis reaction unit 20 may be configured to include a nozzle 15 that supplies the mixed solution 55 to the bottom surface inside the container located on the downstream side of the incline, and to send the mixed solution 55 from the downstream side to the upstream side of the incline by the supply pressure of the nozzle 15. In this way, the time for the solution to pass through the container can be relatively long, so that the reaction solution can be efficiently irradiated with light, and the formic acid generation efficiency can be improved.

[0047] In the case of the embodiment shown in Fig. 5, the nozzle 15 has an injection port provided near the downstream end of the inclined panel 21, and a discharge hole 25 provided near the upstream end of the inclined panel 21. The mixed solution supplied from the nozzle 15 flows upstream on the inclined panel 21 due to the supply pressure of the nozzle 15. In the case of the embodiment shown in Fig. 5, if the gap between the panel 21 and the light-transmitting member 22 is made as small as possible to form a sheet-like artificial photosynthesis reaction unit 20, it is more effective because the entire mixed solution 55 can be irradiated with sunlight.

[0048] The specific reaction process in the formic acid generating device according to one embodiment of the present invention is considered to be as follows: First, water is decomposed by the photocatalyst to generate oxygen, hydrogen ions, and electrons, as shown in reaction formula (1). 2H2O→O2+4H + +4e - (1)

[0049] Next, through a photoreaction (artificial photosynthesis) process using photocatalysts, dyes, etc., formic acid is produced from hydrogen ions and electrons, and carbon dioxide or organic substances mixed into the solution (reaction formula (2) or reaction formula (3) below). A notable feature of this reaction is that carbon dioxide is not essential. At this time, the hydrogen ions and electrons produced in reaction formula (1) are consumed. Furthermore, while reaction formula (2) makes it possible to use carbon dioxide present in the atmosphere and / or exhaust gases from other engines, reaction formula (3) has a major feature in that formic acid can also be formed from carbon C in organic substances mixed into the solution. CO2+2H + +2e - →HCOOH ···(2) Organic matter +2H + +2e - →HCOOH (3)

[0050] At this time, among the irradiated light, mainly ultraviolet light acts on the metal oxide as a photocatalyst, and visible light acts on the dye, so that in the formic acid generator according to one embodiment of the present invention, it is believed that the combined action of these two doubles the efficiency of formic acid production. In other words, even in the case of only a metal oxide and a dye, it is believed that the interaction between the metal oxide and the dye makes it possible to directly donate electrons to the formic acid production reaction.

[0051] The formic acid recovery section 30 is a facility for recovering formic acid from the mixed solution after the reaction. The mode of the facility is not particularly limited as long as it can recover formic acid. As an example, the formic acid recovery section 30 may be provided with a facility for recovering and cooling the gas phase of the mixed solution after the reaction, and recover formic acid as a liquid by refluxing. Since the vapor pressure of formic acid is greater than the vapor pressure of water below the boiling point, more formic acid is vaporized than water. Therefore, by recovering and cooling the gas phase of the mixed solution after the reaction, formic acid can be concentrated and recovered. In the formic acid recovery section 30, an aqueous formic acid solution can be obtained by cooling the gas phase containing formic acid with a heat exchanger or the like. The formic acid thus generated can also be stored in, for example, a storage facility.

[0052] In addition, in one aspect of the present invention, it has been confirmed that the production efficiency of formic acid is improved by mixing air into the mixed solution. Therefore, in one aspect of the present invention, it is preferable to further include an air supply means 40 that supplies air to the mixed solution. Examples of the air supply means 40 include a fan that sends air and a gas pump that supplies air. The air supply means 40 may send air directly into the artificial photosynthesis reaction section 20, or may be installed around the raw material input section 10 or the pump to supply air to the mixed solution being sent. The air supply means 40 may, for example, supply air intermittently so as not to affect the formic acid recovery section 30 described above.

[0053] In one embodiment of the present invention, a control unit may be provided that can continuously measure the amount of formic acid produced by the formic acid generator in real time by measuring the electrical conductivity and temperature of the mixed solution and graphing the relationship between the formic acid concentration and the electrical conductivity in advance. This allows the amount of formic acid produced in the formic acid generator to be remotely grasped, and allows remote operation and control.

[0054] The formic acid generating apparatus according to one embodiment of the present invention as described above has the following advantages. 1. By supplying the reaction solution into an inclined plate-like container, the entire reaction solution can be irradiated with sunlight, improving the efficiency of formic acid production. 2. By supplying air from the air supply means, oxygen is supplied during the production of formic acid, and the efficiency of the production of formic acid is further improved. 3. It is possible to recover the generated formic acid and replenish artificial photosynthetic materials, all at specific locations. 4. By simply adding and replenishing all the materials, the artificial photosynthesis device can operate almost indefinitely. EXAMPLES

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0056] Example 1 A formic acid generating device according to the present invention was created in the embodiment shown in Fig. 3, and a mixed solution containing glucose, a dye, and a photocatalyst was circulated. The tempered glass on the side exposed to sunlight was 820 mm x 1620 mm x 3 mm, the mixed solution was 5 to 10 L, and the flow speed was 1 m / s.

[0057] Comparative Example 1 A similar mixed solution was circulated using the method described in Patent Document 1.

[0058] Comparative Example 2 In the method described in Patent Document 1, a similar mixed solution was circulated while mixing air with a stirrer.

[0059] Fig. 6 is a graph showing the amount of formic acid produced in an embodiment in which one aspect of the present invention is applied and in a comparative example of the prior art, and Fig. 7 is a graph showing the amount of formic acid produced in an embodiment in which one aspect of the present invention is applied. As shown in Fig. 6, in the case of Comparative Example 2, the amount of formic acid produced was about 80 mM in 25 days, whereas in the embodiment in which the present invention is applied, the amount of formic acid produced was 370 mM in about 10 days as shown in Figs. 6 and 7. It was found that the formic acid production rate in the embodiment was 10 times or more faster than that in the comparative example.

[0060] In addition, when comparing Comparative Example 2, in which a moderate amount of air was mixed in by stirring, with Comparative Example 1, in which no air was mixed in, Comparative Example 2 produced a greater amount of formic acid, and it was also found that mixing air by stirring is effective in improving the amount of formic acid produced.

[0061] Although each embodiment and each example of the present invention has been described in detail above, it will be easily understood by those skilled in the art that many modifications are possible without substantially departing from the novel features and effects of the present invention. Therefore, all such modifications are intended to be included within the scope of the present invention.

[0062] For example, a term described at least once in the specification or drawings together with a different term having a broader or similar meaning can be replaced with that different term anywhere in the specification or drawings. The configuration of the formic acid generating device is not limited to those described in the embodiments and examples of the present invention, and various modifications are possible. [Explanation of symbols]

[0063] 10 raw material input section, 15 nozzle, 20 artificial photosynthesis reaction section, 21 panel, 22 light-transmitting member, 23 frame material, 24 (nozzle) installation hole, 25 discharge hole, 30 formic acid recovery section, 40 air supply means, 45 pump, 50 formic acid production device, 55 mixed solution (reaction solution)

Claims

1. A raw material input section for inputting a solution containing an organic substance and a metal oxide powder having a photocatalytic function; The mixed solution of the organic substance and the metal oxide powder is irradiated with sunlight or light to cause a reaction. an artificial photosynthetic reaction unit that a formic acid recovery section for recovering formic acid from the mixed solution after the reaction; Equipped with At least the surface of the artificial photosynthesis reaction unit to which light is irradiated is formed of a light-transmitting material. A formic acid generating device comprising: a plate-shaped container that is inclined with respect to the ground surface; a nozzle is provided inside the container located upstream of the inclination, which sprays the mixed solution toward the inner side of the light-transmitting member attached to the top surface; the sprayed mixed solution adheres to the underside of the light-transmitting member due to the surface tension of the member while flowing downstream due to the inclination; thereby enabling the inner surface of the light-transmitting member to constantly adhere to the solution; and no blocking of sunlight due to solution adhesion as the surface of the member dries, thereby efficiently carrying out an artificial photosynthetic reaction on the liquid surface of the mixed solution where almost all of the sunlight is absorbed.

2. The formic acid generating apparatus according to claim 1, characterized in that the formic acid recovery section is provided with equipment for recovering and cooling the gas phase of the mixed solution after the reaction, thereby recovering formic acid as a liquid by refluxing.

3. 2. The formic acid generating apparatus according to claim 1, further comprising an air supplying means for supplying air to the mixed solution.

4. The formic acid generating apparatus according to claim 1, further comprising a control unit capable of continuously measuring the amount of formic acid generated in real time by measuring the electrical conductivity and temperature of the mixed solution and graphing the relationship between the formic acid concentration and the electrical conductivity in advance.

5. 2. The formic acid generating apparatus according to claim 1, wherein the light-transmitting member is embossed glass to effectively allow the mixed solution to adhere to the underside of the light-transmitting member.

6. 2. The formic acid generating apparatus according to claim 1, wherein the angle of the inclination with respect to the horizontal plane is between 10 degrees and 15 degrees.

7. 2. The formic acid generating apparatus according to claim 1, wherein the organic substance includes glucose, and the photocatalytic function includes titanium oxide fine particles.

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