JP6366287B2 - Ammonia generator and ammonia generation method - Google Patents

Description

  The present invention relates to an ammonia generator and an ammonia generation method.

  In recent years, environmental problems and energy problems are becoming apparent on a global scale, and research on the construction of light energy conversion systems such as photocatalysts and solar cells has attracted attention. Among them, ammonia is excellently storable and portable as a hydrogen carrier for fuel cells, and is therefore actively studied as an energy carrier. However, the Harbor Bosch method, which is a conventional ammonia synthesis method, is generally a reaction under extremely severe conditions of 200 atm and 400 ° C., and when ammonia is regarded as an energy carrier, the energy used for production and the obtained ammonia As a balance with chemical energy, it is not profitable.

  As a reaction mechanism that replaces such a conventional thermochemical reaction, a photocatalytic reaction using a semiconductor has been studied, and research on making a photocatalyst visible light has been conducted in order to increase efficiency (for example, Patent Document 1). .

  Further, in Patent Document 2, a metal microstructure is arranged at the center of the surface of a semiconductor substrate containing titanium oxide, a conductive layer is formed on the entire back surface of the semiconductor substrate, and a container in which the semiconductor substrate is accommodated. A photoelectric conversion device having a structure in which an arrangement region of a metal microstructure is filled with an electrolyte solution is disclosed. According to such a photoelectric conversion device, a photocurrent is observed at a plasmon resonance wavelength based on irradiation with visible light and near infrared light.

JP 2012-25985 A International Publication No. 2011/027830

  However, in the ammonia synthesis method described in Patent Document 1, due to the nature of the semiconductor photocatalyst, it is necessary to use short wavelength light having high energy in order to achieve a reduction reaction having a negatively large energy level, such as nitrogen reduction. Because there is a limit to visible light. On the other hand, according to the photoelectric conversion device described in Patent Literature 2, it is possible to generate oxygen or hydrogen peroxide by inducing a redox reaction of water according to visible light and near infrared light irradiation, In that case, it is necessary to connect an electrochemical measurement device to the photoelectric conversion device and apply a voltage from the outside.

  The present invention provides an ammonia generation apparatus and an ammonia generation method capable of efficiently generating ammonia without requiring an external device.

  An ammonia generator according to one embodiment of the present invention includes a base material including a photocatalytic material, a metal body provided on the surface of the base material or inside the base material, and arranged in a plurality of regions, and provided on the base material. And an ammonia generation catalyst. At least a part of the substrate is disposed between the metal body and the ammonia generating catalyst.

  According to such an ammonia generator, water is brought into contact with one surface of the base material on which the metal body is provided, and nitrogen is brought into contact with the other surface of the base material on which the ammonia generating catalyst is provided. In this state, by irradiating the base material with light, water can be oxidized on one surface of the base material to generate oxygen, and nitrogen can be reduced on the other surface of the base material to generate ammonia. In this case, photoelectrolysis of water is efficiently performed in the plasmon resonance wavelength range determined by the microstructure of the metal body, and at the same time, the reduction reaction of nitrogen is also efficiently performed by the ammonia generating catalyst. As a result, ammonia can be efficiently generated without the need for voltage application by an external device.

  In the ammonia generator according to another aspect of the present invention, the photocatalytic material may be a metal oxide. In this case, electrons excited by plasmon resonance absorption can be efficiently transferred to the electron conduction band of the photocatalytic material. As a result, water oxidation reaction and nitrogen reduction reaction can be further activated, and ammonia can be generated more efficiently.

  In the ammonia generator according to still another aspect of the present invention, the metal body may contain a group 11 element. In this case, the plasmon resonance absorptivity with respect to light can be enhanced on one surface of the base on which the metal body is provided. As a result, water oxidation reaction and nitrogen reduction reaction can be generated more efficiently, and ammonia can be generated more efficiently.

  In the ammonia generator according to still another aspect of the present invention, the ammonia generating catalyst may contain a transition metal element. In this case, the reduction reaction of nitrogen can be activated on the other side of the substrate where the ammonia generation catalyst is provided, and ammonia is generated more efficiently without the need for voltage application by an external device. It becomes possible to make it.

  An ammonia generation method according to one embodiment of the present invention includes a base material including a photocatalytic material, a metal body provided on the surface of the base material or inside the base material, and arranged separately in a plurality of regions, and provided on the base material An ammonia generating device provided with at least a part of the base material disposed between the metal body and the ammonia generating catalyst, and holding the ammonia generating catalyst in contact with nitrogen; The substrate is irradiated with light.

  According to such an ammonia generation method, water is brought into contact with one surface of the base material on which the metal body is provided, and nitrogen is brought into contact with the other surface of the base material on which the ammonia generation catalyst is provided. In this state, by irradiating the base material with light, water can be oxidized on one surface of the base material to generate oxygen, and nitrogen can be reduced on the other surface of the base material to generate ammonia. In this case, photoelectrolysis of water is efficiently performed in the plasmon resonance wavelength range determined by the microstructure of the metal body, and at the same time, the reduction reaction of nitrogen is also efficiently performed by the ammonia generating catalyst. As a result, ammonia can be efficiently generated without the need for voltage application by an external device.

  In the ammonia generation method according to another aspect of the present invention, the wavelength of light may be 400 nm or more. In this case, ammonia can be efficiently generated by simply irradiating the substrate with light having a wavelength in the visible light region or near infrared region, such as sunlight, without requiring the application of a voltage by an external device. it can.

  According to the present invention, ammonia can be generated efficiently without the need for an external device.

It is a side view of the ammonia generator which concerns on one Embodiment of this invention. It is sectional drawing which shows the structure of the photocatalyst of FIG. It is a figure which shows an example of the electron micrograph of the surface of the photocatalyst of FIG. It is a graph which shows an example of the size distribution of the metal body shown in FIG. It is a figure which shows an example of the quenching spectrum of the surface of the photocatalyst of FIG. It is a figure which shows an example of the X-ray photoelectron spectroscopy spectrum of the back surface of the photocatalyst of FIG. It is a figure which shows the modification of the photocatalyst of FIG. It is a figure which shows the modification of the photocatalyst of FIG. It is the schematic of the ammonia production | generation apparatus used for the characteristic measurement. It is a figure which shows the relationship between the wavelength of the light in each ammonia concentration, and the light absorbency of a salicylic acid dimer. It is a figure which shows the ammonia production amount with respect to the irradiation time of light. It is a figure which shows the ammonia production amount for every wavelength range of incident light. It is a figure which shows the quantum yield for every wavelength range of incident light.

  Hereinafter, an embodiment of an ammonia generator and an ammonia generation method according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Each drawing is created for explanation, and is drawn so as to particularly emphasize the target portion of the explanation. Therefore, the dimensional ratio of each member in the drawings does not necessarily match the actual one.

  FIG. 1 is a side view of an ammonia generator according to an embodiment of the present invention. This ammonia generator is a photoelectrochemical cell that converts light energy in a wide wavelength range into chemical energy by water oxidation reaction and nitrogen reduction reaction.

  As shown in FIG. 1, the ammonia generator 1 includes a substantially cylindrical sealed container 3 and a photocatalyst 5 accommodated in the sealed container 3. The sealed container 3 has a partition wall 3c in the center of the inside thereof, holds the aqueous solution 7a in the space S1 on one bottom surface 3a side separated by the partition wall 3c, and gas in the space S2 on the other bottom surface 3b side separated by the partition wall 3c. 7b is held. And the photocatalyst 5 is being fixed to the center part of the partition 3c in the airtight container 3 so that the both surfaces 5a and 5b may face the circular bottom surfaces 3a and 3b of the airtight container 3, respectively. As a result, the photocatalyst 5 is held in the sealed container 3 with one surface 5a immersed (contacted) in the aqueous solution 7a and the other surface 5b contacted with the gas 7b. . A window portion 3d made of quartz or the like is provided at the center of the bottom surface 3a of the sealed container 3. The light L irradiated from the outside is configured to be incident on one surface 5a of the photocatalyst 5 by transmitting through the window 3d. Further, a discharge port 3e is provided on the bottom surface 3a side of the side surface of the sealed container 3, so that oxygen generated by the oxidation reaction in the space S1 can be taken out to the outside. An outlet 3f is provided, and ammonia (ammonium salt) generated by the reduction reaction in the space S2 can be taken out to the outside.

  In the space S1 of the ammonia generator 1, a potassium hydroxide (KOH) solution with a concentration of 0.1M and ph 13.0 containing 10% by volume of ethanol is accommodated as the aqueous solution 7a. In the space S2 of the ammonia generator 1, for example, steam saturated nitrogen gas is accommodated as the gas 7b. In addition to the gas 7b, for example, a hydrogen chloride (HCl) solution having a concentration of 0.01 M, ph 2.0, and a capacity of 15 μL is injected into the space S2 of the ammonia generator 1.

  The light L irradiated from the outside is light including a wavelength in the visible light region or near-infrared light region, for example, sunlight. The wavelength of the light L is, for example, 400 nm or more.

  FIG. 2 is a cross-sectional view showing the detailed structure of the photocatalyst 5. FIG. 3 is a diagram showing an example of a scanning electron microscope (SEM) image of the surface of the photocatalyst 5 of FIG. FIG. 4 is a graph showing an example of the size distribution of the metal body shown in FIG. FIG. 5 is a diagram showing an example of the extinction spectrum of the surface 5a of the photocatalyst 5 of FIG. FIG. 6 is a diagram showing an example of an X-ray photoelectron spectroscopy (XPS) spectrum of the surface 5b of the photocatalyst 5 of FIG.

As shown in FIG. 2, the photocatalyst 5 includes a base material 9, a metal body 11, and an ammonia generation catalyst 13. The base material 9 contains a photocatalytic material that is active with respect to ammonia and oxygen generation with respect to irradiation with visible light. The photocatalytic material is, for example, a metal oxide. Examples of such a photocatalytic material include strontium titanate (SrTiO ₃ ) and titanium oxide (TiO ₂ ). As the base material 9, for example, a strontium titanate substrate doped with niobium (Nb) at 0.05 wt% is used. In this case, the surface 9a of the base material 9 is, for example, a (110) surface of strontium titanate. The size of the base material 9 is, for example, 10 mm × 10 mm. The surface 9 a of the base material 9 corresponds to the surface 5 a of the photocatalyst 5, and the back surface 9 b of the base material 9 corresponds to the surface 5 b of the photocatalyst 5.

  The metal bodies 11 are provided so as to be in contact with the base material 9. For example, the metal bodies 11 are arranged in a plurality of regions along the surface 9 a of the base material 9. The metal body 11 contains a group 11 element, for example. Examples of the group 11 element include gold (Au). As shown in FIGS. 3 and 4, the metal body 11 is a substantially circular metal film having a diameter in the range of 10 nm to 100 nm and an average diameter of, for example, 52 nm. As shown in FIG. 5, the photocatalyst 5 has a fine structure (nanostructure) of the metal body 11 on the surface 5a, thereby responding to light having a wavelength in the visible light region or near infrared region (of the metal body 11). Optical antenna effect by plasmon resonance). That is, the fine structure (size and shape) of the metal body 11 is configured to be responsive at wavelengths in the visible light region or near infrared region. Visible light or near-infrared light collected by the optical antenna effect causes charge separation of the metal body 11, and the generated electrons move to the photocatalytic material of the substrate 9, thereby causing ammonia reduction reaction.

  Here, the material of the metal body 11 may be a metal material having plasmon resonance absorptivity for incident light with various wavelengths depending on the size and shape, in addition to gold. Examples of such a metal material include metal materials such as silver, copper, platinum, aluminum, and alloys thereof. The plasmon resonance absorptivity is a property that resonates with incident light and localizes the light to enhance the electric field, thereby causing a phenomenon called so-called localized surface plasmon. By using such a metal material as the material of the metal body 11, the response wavelengths in the visible light region and the near-infrared light region on the surface 5 a of the photocatalyst 5 can be controlled by the size and shape of the metal body 11. .

  The ammonia generating catalyst 13 is provided in contact with the base material 9 and is disposed on the back surface 9b opposite to the front surface 9a of the base material 9, for example. That is, the metal body 11, the base material 9, and the ammonia generation catalyst 13 are arranged in this order, and the metal body 11 and the ammonia generation catalyst 13 are arranged so as to sandwich the base material 9. The ammonia generation catalyst 13 contains a transition metal element, for example. When the ammonia generating catalyst 13 contains ruthenium (Ru) as a transition metal element, an X-ray photoelectron spectrum as shown in FIG. 6 is obtained on the surface 5 b side of the photocatalyst 5.

  Here, the material of the ammonia generation catalyst 13 may be a material that increases the efficiency of ammonia generation in addition to ruthenium. Such an ammonia generating catalyst preferably contains a transition metal element from the viewpoint of nitrogen adsorption, and particularly preferably contains molybdenum, iron, cobalt, rhenium, and zirconium from the viewpoint of nitrogen reducibility.

  Next, an example of a method for producing the photocatalyst 5 will be described. First, the base material 9 is prepared. Then, for example, the metal body 11 is formed to a thickness of about 3 nm on the surface 9a of the base material 9 by sputtering, and then the surface 9a of the base material 9 is heated at a temperature of 800 ° C. under a nitrogen atmosphere for a predetermined time (for example, 1 hour) An annealing treatment is performed to form the metal body 11 separated into a plurality of regions. By such treatment, the metal atoms diffuse on the surface 9a of the substrate 9 as the temperature rises, and the particle size is controlled to some extent in accordance with the film thickness within the range of the surface diffusion length. An island is formed.

  In addition, when gold is used as the material of the metal body 11, the metal body 11 is easy to diffuse the surface 9a of the base material 9, and an island is easily formed. Moreover, an island structure can be easily created by annealing the sputtered metal body 11.

  Subsequently, the ammonia generating catalyst 13 is formed in a thickness of about 3 nm on the back surface 9b of the substrate 9 by, for example, electron beam evaporation. In this way, the photocatalyst 5 is produced.

  Next, an ammonia generation method using the ammonia generator 1 configured as described above will be described in detail. First, the ammonia generator 1 is prepared. And the aqueous solution 7a is inject | poured in space S1 of the airtight container 3 of the ammonia generator 1, and gas 7b is inject | poured in space S2. As a result, the aqueous solution 7a is brought into contact with the surface 5a of the photocatalyst 5 and the aqueous solution 7a and the gas 7b are held in the sealed container 3 in a state where the gas 7b is brought into contact with the surface 5b. Further, an aqueous solution such as a hydrogen chloride solution is injected into the space S2 of the sealed container 3. Then, light L including a wavelength in the visible light region or near-infrared region is incident from the window portion 3 d of the sealed container 3 toward the surface 5 a of the photocatalyst 5.

As a result, the electrons of the metal body 11 are excited by the plasmon enhancement by the metal body 11 on the surface 5a of the photocatalyst 5 (the surface 9a of the base material 9), and the excited electrons move to the electron conduction band of the photocatalytic material of the base material 9. Be made. Due to the movement of the electrons, holes are generated on the surface 5 a side of the photocatalyst 5, and the holes are trapped in the surface level of the photocatalytic material of the substrate 9. And the oxidation reaction of the hydroxide ion and ethanol in the aqueous solution 7a is caused by the hole. This water and ethanol oxidation reaction has the following chemical formula:
4h ⁺ + 4OH ⁻ → O ₂ + 2H ₂ O
2h ⁺ + C ₂ H ₅ OH → CH ₃ CHO + 2H ⁺
By this reaction, oxygen and acetaldehyde are generated in the vicinity of the surface 5a of the photocatalyst 5 in the space S1, and oxygen is discharged from the discharge port 3e.

Further, the electrons moved to the electron conduction band of the photocatalytic material of the base material 9 reach the ammonia generation catalyst 13. The electrons cause a reduction reaction of nitrogen in the gas 7b on the surface 5b of the photocatalyst 5 (the back surface 9b of the base material 9). This nitrogen reduction reaction has the following chemical formula:
N ₂ + 6H ⁺ + 6e ⁻ → 2NH ₃
In such a reaction, ammonia is generated near the surface 5b of the photocatalyst 5 in the space S2. The produced ammonia is an ammonium salt (ammonium chloride: NH 4 _Cl) in combination with hydrochloric acid in the space S2 and becomes. The ammonium salt is taken out from the outlet 3f and reacted with a strong base such as sodium hydroxide to obtain ammonia.

  According to the ammonia generation apparatus 1 and the ammonia generation method using the ammonia generation apparatus 1 described above, the metal body 11 is in a state where the aqueous solution 7a is in contact with the surface 5a of the photocatalyst 5 and the gas 7b is in contact with the surface 5b. By irradiating the surface 5a of the photocatalyst 5 with light L, the aqueous solution 7a is oxidized on the surface 5a of the photocatalyst 5 to generate oxygen, and the gas 7b is reduced on the surface 5b of the photocatalyst 5 to generate ammonia. Can be made. In this case, the photoelectrolysis of water is efficiently performed in the plasmon resonance wavelength range determined by the fine structure of the metal body 11, and at the same time, the reduction reaction of nitrogen is efficiently performed by the ammonia generation catalyst 13. As a result, ammonia can be generated efficiently without the need to apply a voltage from an external device.

  In the ammonia generator 1, the metal body 11 functions as an optical antenna that can collect incident light of various wavelengths and localize and amplify the light. For example, although strontium titanate alone transmits almost 600 nm light, the fine structure of the metal body 11 is controlled to set the plasmon resonance wavelength of the metal body 11 to a visible light region or a near infrared light region. Thus, the ammonia generation reaction in the wavelength region can be advanced. Furthermore, if the structure of the metal body 11 is controlled so that the plasmon resonance wavelength matches the wavelength band of solar energy, the solar energy can be efficiently converted into chemical energy, and the reaction center wavelength is about 680 nm. It is possible to construct a system that is not inferior to photosynthesis.

  Moreover, in the ammonia generator 1, since the metal oxide is used as the photocatalytic material of the base material 9, the electrons excited by the plasmon resonance absorption can be efficiently transferred to the electron conduction band of the photocatalytic material, The oxidation reaction of the aqueous solution 7a and the reduction reaction of the gas 7b can be further activated. Further, since the metal body 11 formed on the photocatalyst 5 is made of a group 11 element, the surface 9a of the base material 9 can enhance the plasmon resonance absorption with respect to light. For this reason, the oxidation reaction of the aqueous solution 7a and the reduction reaction of the gas 7b can be generated more efficiently. Furthermore, since the ammonia generating catalyst 13 is composed of a transition metal element, the reduction reaction of the gas 7b can be activated on the back surface 9b of the base material 9, and the aqueous solution 7a can be applied without requiring the application of a voltage by an external device. The oxidation reaction and the reduction reaction of the gas 7b can be generated more efficiently. As a result, ammonia can be generated more efficiently.

  In addition, this invention is not limited to the above-mentioned embodiment. For example, the ammonia generator 1 is provided with a window 3d so that the light L is incident on the surface 5a of the photocatalyst 5 through the window 3d, but is opposite to the window 3d of the sealed container 3. A window portion may be provided on the side (for example, the bottom surface 3b), and light may be incident on the surface 5b of the photocatalyst 5 from the outside. According to such a configuration, light transmitted through the ammonia generating catalyst 13 and the base material 9 is irradiated by irradiating the surface 5b of the photocatalyst 5 with light L including a wavelength in the visible light region or near infrared light region from the outside. It can be collected by the metal body 11 to cause charge separation. Furthermore, a window portion may be provided on the opposite side of the window portion 3d of the sealed container 3 in addition to the window portion 3d. In this case, the surface 5a and the surface 5b can be irradiated with visible light or near-infrared light simultaneously, and ammonia can be generated more efficiently.

  Further, in the ammonia generator 1, the metal body 11 is provided on the front surface 9a of the base material 9, and the ammonia generating catalyst 13 is provided on the back surface 9b of the base material 9, but at least a part of the base material 9 is a metal body. 11 and the ammonia generation catalyst 13 may be disposed. That is, the metal body 11, the base material 9, and the ammonia generation catalyst 13 should just be arranged in that order along a certain direction. For example, as shown in FIG. 7A, all the regions of the metal body 11 may be provided inside the base material 9, and as shown in FIG. A part of the region may be provided inside the substrate 9. Moreover, the shape of the base material 9 is not restricted to plate shape, For example, as shown to (a) of FIG. 8, the base material 9 may be provided with the some convex part. The ammonia generator 1 may include two or more base materials 9. For example, as illustrated in FIG. 8B, the base material 9 may be provided between each region of the metal body 11 and the ammonia generation catalyst 13. Further, as shown in FIG. 8C, a base material 91 and a base material 92 connected by the conductor 16 are provided, the metal body 11 is provided on the base material 91, and the ammonia generating catalyst 13 is provided on the base material 92. It may be provided. As the conductor 16, for example, a metal, an electrolyte solution, an ionic solution, a molten salt, or the like is used. Further, the ammonia generating catalyst 13 does not need to be provided on the entire back surface 9b of the base material 9. Even when the photocatalyst 5 as shown in FIGS. 7 and 8 is used, the metal body 11 collects light, and charge separation is caused at the interface between the metal body 11 and the base material 9. Electrons are carried. As a result, ammonia can be generated without requiring application of a voltage by an external device.

(Example)
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

  FIG. 9 is a schematic diagram of an ammonia generator used for measuring the characteristics of the ammonia generator 1. In this characteristic measurement, the photocatalyst 5 of the example and the photocatalyst 105 of the comparative example were prepared. The photocatalyst 5 of the example was produced as follows. A strontium titanate substrate doped with 0.05 wt% niobium was used as the substrate 9. After the metal body 11 made of gold is formed to a thickness of 3 nm on the surface 9a of the base material 9 by sputtering, it is annealed at 800 ° C. for 1 hour in a nitrogen atmosphere, and the back surface of the base material 9 is formed by electron beam evaporation. An ammonia generating catalyst 13 made of ruthenium was formed into a film with a thickness of 3 nm on 9b. This photocatalyst 5 had the characteristics shown in FIGS.

  In the photocatalyst 105 of the comparative example, a strontium titanate substrate doped with 0.05 wt% niobium was used as the base material 9. Only the base material 9 was formed without forming the metal body 11 and the ammonia generating catalyst 13.

  A space S1 of the ammonia generator 1 containing these photocatalysts contains a potassium hydroxide solution having a concentration of 0.1M and ph13.0 containing 10% by volume of ethanol, and a water-saturated nitrogen gas is contained in the space S2. Further, 15 μL of a hydrogen chloride solution having a concentration of 0.01 M and ph 2.0 was injected into the space S2. Then, as shown in FIG. 9, the ammonia generator 1 was irradiated with light having a predetermined wavelength using a light source 20. That is, the light emitted from the 800 W xenon lamp 21 was applied to one surface 5 a of the photocatalyst from the window 3 d of the ammonia generator 1 through the water filter 22, the lens 23 and the optical filter 24. Then, pure water was passed through the ammonia generator 1 after the reaction, and the ammonium salt eluted in the pure water was quantified.

(Quantification of ammonia)
Here, a method for quantifying ammonia will be described. Add 0.08 mL of 50 wt% EDTA · 4Na · 4H ₂ O solution to 0.5 mL of the aqueous solution from which the ammonium salt is eluted. Then, 0.52 mL of a mixed solution of sodium hydroxide having a concentration of 1.25M and sodium hypochlorite containing 0.87 wt% of chlorine element is added, and ammonium is reacted with sodium hydroxide to generate ammonia. Then, ammonia and hypochlorite ions are reacted. This chemical reaction has the following chemical formula:
NH ₄ Cl + NaOH → NH ₃ + NaCl + H ₂ O
NH ₃ + ClO ⁻ → NH ₂ Cl + OH ⁻
A monochloramine is produced by such a reaction. Then, 0.16 mL of a mixed solution of 1.46M sodium salicylate and 0.24M pyrazole is added to react monochloramine, salicylic acid, and hypochlorite ion. This chemical reaction has the following chemical formula:

The salicylic acid dimer is produced by such a reaction.

  FIG. 10 is a diagram showing the relationship between the wavelength of light and the absorbance of salicylic acid dimer at each ammonia concentration. Since salicylic acid dimer reacts quantitatively with ammonia, the absorbance of salicylic acid dimer and the concentration of ammonia are in a proportional relationship. The salicylic acid dimer has a maximum absorbance with respect to light having a wavelength of 650 nm. Therefore, the concentration of ammonia is calculated from the relationship shown in FIG. 10 by irradiating the salicylic acid dimer obtained as described above with light having a wavelength of 650 nm and measuring the absorbance. Calculate the amount of ammonia. The ammonia may be quantified using a method such as gas chromatography, liquid chromatography, or ion chromatography.

(Measurement result)
FIG. 11 is a diagram showing the amount of ammonia produced with respect to the light irradiation time. The photocatalyst 5 of the example and the photocatalyst 105 of the comparative example were continuously irradiated with light having a wavelength of 550 nm to 800 nm, and the change in the amount of ammonia produced with respect to the irradiation time was measured. Moreover, the change of the ammonia production amount with the passage of time in the dark was measured without irradiating the photocatalyst 5 of the example with light. As shown in FIG. 11, when the photocatalyst 105 of the comparative example is irradiated with light having a wavelength of 550 nm to 800 nm and when the photocatalyst 5 of the example is not irradiated with light, ammonia is generated even if time passes. The amount did not increase. On the other hand, when the photocatalyst 5 of the example was irradiated with light having a wavelength of 550 nm to 800 nm, the amount of ammonia generated increased with the lapse of irradiation time. When the photocatalyst 5 of the example was irradiated with light having a wavelength of 550 nm to 800 nm, the relationship between the irradiation time and the amount of ammonia produced was almost proportional, and the ammonia production rate was about 0.231 nmol / hour.

  FIG. 12 is a diagram showing the amount of ammonia generated for each wavelength range of incident light. FIG. 13 is a diagram showing the quantum yield for each wavelength range of incident light. The wavelength range of the light L was changed from 410 nm to 800 nm, 450 nm to 800 nm, 550 nm to 800 nm, 633 nm to 800 nm, and 700 nm to 800 nm, and each of the photocatalysts 5 of Examples was irradiated for 24 hours. Graph R in FIG. 12 shows the amount of ammonia produced when the target wavelength range is irradiated. For example, “410-” in the graph R indicates the amount of ammonia produced when light in the wavelength range of 410 nm to 800 nm is irradiated for 24 hours. Similarly, “450-” in graph R is the amount of ammonia produced when light in the wavelength range of 450 nm to 800 nm is irradiated for 24 hours, and “550-” in graph R is irradiated for light in the wavelength range of 550 nm to 800 nm for 24 hours. Amount of ammonia produced in graph R, “633−” in graph R represents the amount of ammonia produced when light in the wavelength range of 633 nm to 800 nm was irradiated for 24 hours, and “700−” in graph R represents light in the wavelength range of 700 nm to 800 nm. Shows the amount of ammonia produced when irradiated for 24 hours.

  Graph S in FIG. 12 shows the amount of ammonia produced per unit wavelength. For example, “410-” in the graph S indicates an ammonia production amount per unit wavelength from 410 nm to 450 nm, and {(ammonia production amount when light in a wavelength region of 410 nm to 800 nm is irradiated for 24 hours) − (450 nm to 800 nm The amount of ammonia produced when irradiated with light in the wavelength range of 24 hours)} / (450-410). Similarly, “450−” in the graph S indicates an ammonia production amount per unit wavelength of 450 nm to 550 nm, “550−” in the graph S indicates an ammonia generation amount per unit wavelength of 550 nm to 633 nm, and “633” in the graph S. Represents the amount of ammonia produced per unit wavelength from 633 nm to 700 nm, and “700-” in the graph S represents the amount of ammonia produced per unit wavelength from 700 nm to 800 nm.

The quantum yield η _app for each wavelength range of incident light in FIG. 13 is a value calculated by the equation (1) using the amount of ammonia generated per unit wavelength and the number of photons irradiated at each wavelength. The number of photons irradiated in each wavelength range was measured using a multipurpose spectroradiometer (MSR-7000N).

  In FIG. 13, the quenching spectrum (namely, plasmon resonance spectrum) of the surface 5a of the photocatalyst 5 is also shown. As shown in FIG. 13, the apparent quantum yield was found to correspond to the extinction spectrum of the surface 5 a of the photocatalyst 5. From this, it was proved that the plasmon of the metal body 11 (gold plasmon in the example) contributes to charge separation of the base material 9 (strontium titanate in the example). That is, it can be said that gold electrons are excited by plasmon enhancement, the excited electrons move to the electron conduction band of strontium titanate, and nitrogen is reduced on the surface 5b of the photocatalyst 5 to generate ammonia. And even when sunlight was irradiated to the photocatalyst 5, it was shown that ammonia is produced | generated with the quantum yield according to the wavelength contained in sunlight.

  From the above, by setting the plasmon resonance wavelength of the metal body 11 to the visible light region or the near-infrared light region (in the embodiment, near 620 nm), solar light can be used without using an external device (utilizing the pH gradient). It was shown that it is possible to generate ammonia from water, nitrogen and alcohol simply by irradiating.

  DESCRIPTION OF SYMBOLS 1 ... Ammonia generator, 3 ... Sealed container, 5 ... Photocatalyst, 5a ... Surface, 5b ... Surface, 7a ... Aqueous solution, 7b ... Gas, 9 ... Base material, 9a ... Front surface, 9b ... Back surface, 11 ... Metal body, 13 ... ammonia generation catalyst, L ... light, S1 ... space, S2 ... space.

Claims (6)

A substrate having a first substrate and a second substrate comprising a photocatalytic material connected to each other by a conductor;
A metal body having plasmon resonance absorption disposed on the surface of the first base material or inside the first base material and arranged separately in a plurality of regions;
An ammonia generating catalyst provided on the second substrate;
A sealed container containing the substrate, the metal body, and the ammonia generating catalyst;
With
The sealed container is provided on a first window for entering light provided on a first bottom surface facing the surface of the first base material, and on a second bottom surface opposite to the first bottom surface. A second window for allowing the light to enter,
At least a part of the base material is an ammonia generator arranged between the metal body and the ammonia generating catalyst. The ammonia generator according to claim 1 , wherein the photocatalytic material is a metal oxide. The ammonia generator according to claim 1 or 2 , wherein the metal body contains a Group 11 element. The ammonia generating apparatus according to any one of claims 1 to 3 , wherein the ammonia generating catalyst contains a transition metal element. A base material having a first base material and a second base material containing a photocatalyst material connected to each other by a conductor; provided on the surface of the first base material or inside the first base material; A metal body having plasmon resonance absorption disposed, an ammonia generation catalyst provided on the second base material, and a sealed container containing the base material, the metal body, and the ammonia generation catalyst, Preparing an ammonia generator in which at least a part of the base material is disposed between the metal body and the ammonia generating catalyst;
Holding the ammonia generating catalyst in contact with nitrogen;
Irradiating the substrate with light,
The sealed container is provided on a first window provided on a first bottom surface facing the surface of the first base material and on a second bottom surface opposite to the first bottom surface. A second window for making the light incident thereon,
Irradiating the substrate with the light from the first window and the second window;
Ammonia generation method. The ammonia generation method according to claim 5 , wherein the wavelength of the light is 400 nm or more.