Carbon nitride dark photocatalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of non-metallic material preparation, solar energy utilization and green energy production, in particular to a carbon nitride dark photocatalyst as well as a preparation method and application thereof. The preparation method of the carbon nitride dark photocatalyst comprises the following steps: calcining melamine I to obtain common carbon nitride; grinding and uniformly mixing the common carbon nitride and potassium thiocyanate to obtain a precursor mixture; calcining the precursor mixture II to obtain a carbon nitride dark photocatalyst precursor; and adding the carbon nitride dark photocatalyst precursor into water for soaking and stirring, then carrying out solid-liquid separation, and sequentially washing and drying the obtained solid to obtain the carbon nitride dark photocatalyst. The carbon nitride dark photocatalyst can produce hydrogen peroxide in the dark. The limitation that a traditional photocatalyst cannot react under the dark condition is solved, and the photocatalyst can be used as an efficient hydrogen peroxide production catalyst to be applied to clean energy production and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical fields of non-metallic material preparation, solar energy utilization and green energy production, and particularly relates to a carbon nitride photocatalyst with dark-light photocatalytic ability, a preparation method thereof, and an application thereof. Background Art

[0002] Photocatalysis technology shows great potential in the field of green energy production. Especially in the photocatalytic production of hydrogen peroxide from solar energy, it brings new hope for solving energy and environmental problems.

[0003] However, this technology still faces many bottleneck problems. The photocatalytic reaction highly depends on light conditions. Light intensity, wavelength and time all significantly affect the reaction efficiency. When the light is insufficient, the reaction rate drops sharply, seriously affecting practical applications. Existing photocatalytic materials cannot meet the actual application requirements of producing hydrogen peroxide in the dark.

[0004] Therefore, it is necessary to provide a carbon nitride photocatalyst with dark-light photocatalytic ability to solve the application problem of photocatalysis technology when the light is insufficient. Summary of the Invention

[0005] In order to overcome the problem that the reaction rate drops significantly when the light is insufficient in the existing photocatalysis technology, the present invention provides a carbon nitride photocatalyst with dark-light photocatalytic ability, a preparation method thereof, and an application thereof. This method prepares a carbon nitride photocatalyst with dark-light photocatalytic ability through two-step calcination. The operation is simple, and the prepared carbon nitride photocatalyst can produce hydrogen peroxide in the dark.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a preparation method of a carbon nitride photocatalyst, including the following steps:

[0008] Calcine melamine for the first time to obtain ordinary carbon nitride;

[0009] Grind and mix the ordinary carbon nitride with potassium thiocyanate to obtain a precursor mixture;

[0010] Calcine the precursor mixture for the second time to obtain a precursor of the carbon nitride photocatalyst;

[0011] Add the precursor of the carbon nitride photocatalyst into water, soak and stir, then separate the solid from the liquid. The obtained solid is washed and dried in sequence to obtain the carbon nitride photocatalyst.

[0012] Another technical solution of the present invention is a carbon nitride photocatalyst prepared according to the above preparation method.

[0013] The third technical solution of the present invention is the application of the above-mentioned carbon nitride photocatalyst under dim light in the preparation of hydrogen peroxide.

[0014] The fourth technical solution of the present invention is a method for producing hydrogen peroxide under dim light, which includes the following steps:

[0015] Disperse the above-mentioned carbon nitride photocatalyst under dim light in an aqueous methanol solution to obtain a pale yellow suspension;

[0016] Under closed conditions and in a nitrogen atmosphere, irradiate the pale yellow suspension with a xenon lamp. After the pale yellow suspension turns into a blue suspension, transfer the blue suspension to a light-shielded condition (dim light condition) for the hydrogen peroxide production reaction.

[0017] The present invention discloses the following technical effects:

[0018] (1) The preparation method of the present invention is simple. Through a two-step calcination method, without using any solvents, a carbon nitride photocatalyst material with dim light catalytic ability can be obtained. Its preparation process is simple, the operation is convenient, and the cost is relatively low.

[0019] (2) The carbon nitride photocatalyst under dim light prepared by the method of the present invention is potassium-doped carbon nitride containing cyano groups. As a strong electron-withdrawing group, the cyano group can break the original charge balance of carbon nitride. The generated potential difference can not only provide power for the transfer of photo-generated carriers, but also enable the photo-generated carriers to move directionally, thereby improving the light capture ability of the catalyst material. In addition, under the synergistic action of potassium ions and cyano groups, electrons can be stored during illumination and released in the dark, thereby producing hydrogen peroxide. Therefore, the carbon nitride photocatalyst under dim light provided by the present invention has the ability to produce hydrogen peroxide in the dark, solves the limitation that traditional photocatalysts cannot react under dark conditions, and can be used as an efficient hydrogen peroxide production catalyst in clean energy production, with good application prospects.

[0020] (3) The present invention also provides a method for producing hydrogen peroxide under dark conditions. The carbon nitride photocatalyst under dim light of the present invention is used for producing hydrogen peroxide under dark conditions after storing electrons through illumination. Utilizing the dim light catalytic ability of the carbon nitride photocatalyst under dim light, the production of hydrogen peroxide under dark conditions is realized, which has high practical value and good application prospects. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1XRD analysis diagrams of the carbon nitride photocatalyst obtained in Example 1 and ordinary carbon nitride obtained in the comparative example;

[0023] Figure 2 FT-IR analysis diagrams of the carbon nitride photocatalyst obtained in Example 1 and ordinary carbon nitride obtained in the comparative example;

[0024] Figure 3 Yield diagrams of hydrogen peroxide production by the carbon nitride photocatalyst obtained in Example 1 and ordinary carbon nitride obtained in the comparative example in the dark;

[0025] Figure 4 Yield diagrams of hydrogen peroxide production by the carbon nitride photocatalysts obtained in Examples 1-3 in the dark, respectively;

[0026] Figure 5 Photo of the carbon nitride photocatalyst obtained in Example 1 changing color after storing electrons under light. Detailed implementation manners

[0027] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0028] In the present invention, the endpoints and any values of the disclosed ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0029] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0030] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the specification of the present invention, which are obvious to those skilled in the art. Other implementation manners obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are only exemplary.

[0031] Regarding the terms "comprising", "including", "having", "containing", etc. used in this text, they are all open-ended terms, meaning including but not limited to.

[0032] In the present invention, the "room temperature" mentioned herein, unless otherwise specified, all represents 20 - 30 °C.

[0033] Different from traditional photocatalytic materials, the dark photocatalytic material not only has high efficient light capture and electron storage capabilities, but also can stably release electrons in the dark environment to maintain the activity of the reaction.

[0034] In the selection and application of materials, as an emerging semiconductor photocatalyst, non-metal carbon nitride has a band gap of about 2.70 eV, can absorb visible light, has excellent light, heat and chemical stability, and is environmentally friendly. More importantly, the carbon and nitrogen atoms in carbon nitride are bonded by covalent bonds, and the bond energy has a certain range, which is relatively stable and can be broken and reorganized through chemical reactions such as pyrolysis and hydrolysis under certain conditions, providing a basis for the preparation of carbon nitride dark photocatalyst. Therefore, obtaining a carbon nitride dark photocatalyst with dark photocatalytic ability is expected to solve the application problem of photocatalytic technology under insufficient light, and provide a new technical path for realizing all-weather green energy production.

[0035] The first aspect of the present invention provides a preparation method of a carbon nitride dark photocatalyst, comprising the following steps:

[0036] Calcine melamine I to obtain ordinary carbon nitride;

[0037] Grind and mix the ordinary carbon nitride with potassium thiocyanate to obtain a precursor mixture;

[0038] Calcine the precursor mixture II to obtain a carbon nitride dark photocatalyst precursor;

[0039] Add the carbon nitride dark photocatalyst precursor to water, soak and stir, then perform solid-liquid separation, and wash and dry the obtained solid in sequence to obtain the carbon nitride dark photocatalyst.

[0040] In a preferred embodiment of the present invention, the calcination I is specifically: heating to 500 - 600 °C at a rate of 5 - 10 °C / min and calcining for 1 - 3 h.

[0041] The present invention has found through experiments that only the carbon nitride prepared by calcining melamine I can be used to prepare a carbon nitride dark photocatalyst with dark photocatalytic ability, and the carbon nitride obtained through the purchase route cannot obtain a carbon nitride dark photocatalyst with dark photocatalytic ability by using the method of the present invention.

[0042] In a preferred embodiment of the present invention, the mass ratio of the ordinary carbon nitride to potassium thiocyanate is greater than or equal to 1:3; more preferably, it is 1:(0.5 - 3); specifically, it can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, or any value between the aforementioned two values.

[0043] In a preferred embodiment of the present invention, the second calcination is a two-step calcination, specifically: under oxygen-free conditions, first heat at a rate of 5 - 20 °C / min (specifically, it can be 5 °C / min, 10 °C / min, 15 °C / min, 20 °C / min, or any value between the aforementioned two values) to 300 - 500 °C (specifically, it can be 300 °C, 350 °C, 400 °C, 450 °C, 500 °C, or any value between the aforementioned two values) and calcine for 0.5 - 1.5 h (specifically, it can be 0.5 h, 1 h, 1.5 h, or any value between the aforementioned two values) (the first step), and then heat at a rate of 5 - 20 °C / min (specifically, it can be 5 °C / min, 10 °C / min, 15 °C / min, 20 °C / min, or any value between the aforementioned two values) to 400 - 600 °C (specifically, it can be 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, or any value between the aforementioned two values) and calcine for 15 - 60 min (specifically, it can be 15 min, 30 min, 45 min, 60 min, or any value between the aforementioned two values) (the second step). Among them, the second calcination temperature is higher than the first calcination temperature.

[0044] The oxygen-free conditions can be achieved by introducing an inert gas into the reaction vessel, and the inert gas can be a gas that does not react with oxygen at high temperatures, such as argon, nitrogen, helium, etc. Preferably, the inert gas is argon or nitrogen.

[0045] By combining the methods of grinding and mixing and two-step calcination, enabling the cyano group and potassium ions to enter the carbon nitride simultaneously can effectively improve the light capture ability of the carbon nitride photocatalyst in the dark and realize the ability to store electrons under light irradiation.

[0046] In the present invention, the grinding can be mechanical grinding or manual grinding, and the grinding time can be determined by those skilled in the art according to the actual situation. Preferably, the grinding conditions include: the time is 5 - 15 min, which can make the ordinary carbon nitride and the potassium thiocyanate mix evenly.

[0047] In a preferred embodiment of the present invention, the time for soaking and stirring is 1 - 3 h. The purpose of soaking and stirring is to remove the residual metal salt (potassium thiocyanate).

[0048] The present invention does not particularly limit the stirring rate, and the stirring rate commonly used by those skilled in the art can be adopted.

[0049] In the second aspect of the present invention, a carbon nitride photocatalyst for dim light is provided, which is prepared by the above-mentioned preparation method.

[0050] In the third aspect of the present invention, the above-mentioned carbon nitride photocatalyst for dim light is provided for use in the preparation of hydrogen peroxide.

[0051] In the fourth aspect of the present invention, a method for producing hydrogen peroxide under dim light is provided, wherein the carbon nitride photocatalyst for dim light is used as a catalyst for producing hydrogen peroxide; the application process is as follows: under the conditions of light irradiation and oxygen isolation, first make the mixed solution containing the carbon nitride photocatalyst for dim light change in color, place the mixed solution with color change under dark conditions, and then produce hydrogen peroxide under the synergistic action of oxygen. Specifically, it includes the following steps:

[0052] Disperse the above-mentioned carbon nitride photocatalyst for dim light in an aqueous methanol solution to obtain a pale yellow suspension;

[0053] Irradiate the pale yellow suspension with a xenon lamp under closed conditions and an inert atmosphere. Wait until the pale yellow suspension turns into a blue suspension, and transfer the blue suspension to a light-shielded condition (dim light condition) for the hydrogen peroxide production reaction.

[0054] The carbon nitride photocatalyst for dim light provided by the present invention can store electrons under light irradiation and release electrons in the dark, thereby realizing the production of hydrogen peroxide in the dark.

[0055] In a preferred embodiment of the present invention, the volume ratio of methanol to water in the aqueous methanol solution is 1:(5 - 15), specifically it can be 1:5, 1:10, 1:15, or any value between the aforementioned two values;

[0056] In a preferred embodiment of the present invention, the concentration of the carbon nitride photocatalyst for dim light in the aqueous methanol solution is 0.18 - 0.75 mg / mL, specifically it can be 0.18 mg / mL, 0.32 mg / mL, 0.45 mg / mL, or any value between the aforementioned two values.

[0057] In a preferred embodiment of the present invention, the irradiation time of the xenon lamp is 0.5 - 1.5 h, specifically it can be 0.5 h, 1 h, 1.5 h, or any value between the aforementioned two values.

[0058] The carbon nitride photocatalyst for dim light of the present invention is prepared by a simple two-step calcination method. The prepared carbon nitride photocatalyst for dim light will change color significantly under light irradiation, and the carbon nitride photocatalyst for dim light after color change can produce hydrogen peroxide in the dark, solving the limitation that traditional photocatalysts cannot react under dark conditions. It can be used as an efficient hydrogen peroxide production catalyst in clean energy production and has good application prospects.

[0059] The method for producing hydrogen peroxide in the dark provided by the present invention uses the above-mentioned carbon nitride photocatalyst under dim light. After storing electrons through light irradiation, it is used to produce hydrogen peroxide in the dark. Utilizing the photocatalytic ability of the carbon nitride photocatalyst under dim light, hydrogen peroxide production in the dark is achieved, which has high practical value and good application prospects.

[0060] The technical solutions described in the present invention are all conventional solutions in the art unless otherwise specified. The reagents or raw materials used are all purchased from commercial channels or are publicly available unless otherwise specified.

[0061] The technical solutions provided by the present invention will be described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0062] Example 1

[0063] S1. Melamine was calcined at a rate of 10 °C / min from room temperature to 500 °C for 1 h to obtain ordinary carbon nitride.

[0064] S2. 500 mg of the ordinary carbon nitride obtained in step S1 and 1 g of potassium thiocyanate were weighed and ground and mixed evenly to obtain a precursor mixture.

[0065] S3. The precursor mixture obtained in step S2 was heated to 400 °C at a rate of 10 °C / min and calcined for 1 h, and then continued to be heated to 500 °C at a rate of 10 °C / min and calcined for 30 min to obtain a carbon nitride photocatalyst precursor under dim light.

[0066] S4. The carbon nitride photocatalyst precursor obtained in step S3 was soaked in 100 mL of deionized water and stirred for 2 h. After separating the solid in the mixed solution, it was washed with ultrapure water and vacuum dried (temperature 60 °C, time 12 hours) to obtain a carbon nitride photocatalyst under dim light.

[0067] Example 2

[0068] The difference from Example 1 is only that the addition amount of potassium thiocyanate in step S2 is 500 mg; the remaining steps and parameters are the same as those in Example 1.

[0069] Example 3

[0070] The difference from Example 1 is only that the addition amount of potassium thiocyanate in step S2 is 250 mg; the remaining steps and parameters are the same as those in Example 1.

[0071] Comparative Example

[0072] 6 g of melamine was placed in a crucible and calcined at a heating rate of 10 °C / min from room temperature to 500 °C for 2 h. After natural cooling, ordinary carbon nitride was obtained.

[0073] Test Example 1

[0074] The carbon nitride photocatalyst under dim light obtained in Example 1 and the common carbon nitride obtained in the comparative example were respectively subjected to XRD analysis, and the results are as Figure 1 shown. It can be seen from Figure 1 that the common carbon nitride exhibits typical carbon nitride diffraction peaks, while the carbon nitride photocatalyst under dim light obtained in Example 1 exhibits diffraction peaks similar to those of the common carbon nitride, indicating that the overall structure of the carbon nitride has not been changed.

[0075] Test Example 2

[0076] The carbon nitride photocatalyst under dim light obtained in Example 1 and the common carbon nitride obtained in the comparative example were respectively subjected to FT-IR analysis, and the results are as Figure 2 shown. It can be seen from Figure 2 that the common carbon nitride exhibits typical carbon nitride diffraction peaks, while the carbon nitride photocatalyst under dim light obtained in Example 1 exhibits diffraction peaks similar to those of the common carbon nitride, indicating that the overall structure of the carbon nitride has not been changed.

[0077] Test Example 3

[0078] (1) Weigh 50 mg of the carbon nitride photocatalyst under dim light prepared in Example 1 and directly add it to 110 mL of a methanol aqueous solution (the volume ratio of methanol to water in the methanol aqueous solution is 1:10), and then stir and disperse for 10 min (5 - 15 min is acceptable) to obtain a light yellow suspension;

[0079] (2) Add the light yellow suspension obtained in step (2) to a closed reactor, introduce nitrogen at a flow rate of 20 mL / min for 10 min, and then irradiate the light yellow suspension with a xenon lamp for 1 hour, and the light yellow suspension gradually turns into a blue suspension.

[0080] (3) Pour the blue suspension in step (2) into an open reactor, and carry out the hydrogen peroxide production reaction at the 5th minute, 15th minute, 30th minute, and 60th minute under light-shielded conditions.

[0081] In addition, weigh 50 mg of the common carbon nitride obtained in the comparative example, repeat the above steps, and obtain the hydrogen peroxide production yields of Example 1 and the comparative example in the dark, and the results are as Figure 3 shown.

[0082] Figure 3 It is a graph of the hydrogen peroxide production yield measured at the 60th minute in the dark for the carbon nitride photocatalyst under dim light obtained in Example 1 and the common carbon nitride obtained in the comparative example (yield = amount of hydrogen peroxide substance (mmol) / (catalyst mass (g) × reaction time (h))). It can be seen from Figure 3It can be seen that the carbon nitride photocatalyst obtained in Example 1 exhibits better ability to produce hydrogen peroxide in the dark than the ordinary carbon nitride obtained in the comparative example. The hydrogen peroxide production rate of the carbon nitride photocatalyst obtained in Example 1 in the dark is 1.79 mmol g -1 h -1 , while the hydrogen peroxide production rate of the ordinary carbon nitride obtained in the comparative example in the dark is 0.04 mmol g -1 h -1 .

[0083] Test Example 4

[0084] (1) Weigh 50 mg of the carbon nitride photocatalyst prepared in Examples 1-3 and directly add it to 110 mL of methanol aqueous solution (the volume ratio of methanol to water in the methanol aqueous solution is 1:10), and then stir and disperse for 10 min (5-15 min is acceptable) to obtain a pale yellow suspension;

[0085] (2) Add the pale yellow suspension obtained in step (2) to a closed reactor, introduce nitrogen at a flow rate of 20 mL / min (20-50 mL / min is acceptable) for 10 min, and then irradiate the pale yellow suspension with a xenon lamp for 1 hour. The pale yellow suspension gradually turns into a blue suspension.

[0086] (3) Pour the blue suspension in step (2) into an open reactor, and sample for hydrogen peroxide production reaction test at the 5th minute, 15th minute, 30th minute, and 60th minute under light-shielded conditions.

[0087] Figure 4 It is a graph of the hydrogen peroxide production rate measured at the 60th minute in the dark for carbon nitride photocatalysts with different weight ratios of ordinary carbon nitride to potassium thiocyanate. From Figure 4 It can be seen that the carbon nitride photocatalyst obtained in Example 1 exhibits better ability to produce hydrogen peroxide in the dark than the ordinary carbon nitride obtained in the comparative example. The hydrogen peroxide production rate of the carbon nitride photocatalyst obtained in Example 1 in the dark is 1.79 mmol g -1 h -1 , while the hydrogen peroxide production rate of the carbon nitride photocatalyst obtained in Example 2 in the dark is 1.24 mmol g -1 h -1 , and the hydrogen peroxide production rate of the carbon nitride photocatalyst obtained in Example 3 in the dark is 1.1 mmol g -1 h -1 . Obviously, when the weight ratio of ordinary carbon nitride to potassium thiocyanate is 1:2, the carbon nitride photocatalyst obtains the best catalytic effect, indicating that the carbon nitride photocatalyst has the best photocatalytic performance in the dark.

[0088] Figure 5Photographs of the carbon nitride dark-light catalyst before illumination (left figure) and after one hour of illumination (right figure), taken by Figure 5 It can be seen that at the beginning of illumination, the carbon nitride dark-light catalyst is light yellow, and its color turns blue after one hour of illumination.

[0089] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of a carbon nitride photocatalyst for dim light, characterized in that, It includes the following steps: Calcine melamine I to obtain ordinary carbon nitride; Grind and mix the ordinary carbon nitride with potassium thiocyanate to obtain a precursor mixture; Calcine the precursor mixture II to obtain a precursor of carbon nitride photocatalyst for dim light; Add the precursor of carbon nitride photocatalyst for dim light to water, soak and stir, then separate the solid from the liquid, and wash and dry the obtained solid in sequence to obtain the carbon nitride photocatalyst for dim light.

2. The preparation method of the carbon nitride photocatalyst for dim light according to claim 1, characterized in that, The specific operation of the calcination I is: heating up to 500-600 °C at a rate of 5-10 °C / min and calcining for 1-3 h.

3. The preparation method of the carbon nitride photocatalyst for dim light according to claim 1, characterized in that, The mass ratio of the ordinary carbon nitride to potassium thiocyanate is 1∶(0.5-3).

4. The preparation method of the carbon nitride photocatalyst for dim light according to claim 1, characterized in that, The calcination II is a two-step calcination, specifically: first heating up to 300-500 °C at a rate of 5-20 °C / min and calcining for 0.5-1.5 h, and then heating up to 400-600 °C at a rate of 5-20 °C / min and calcining for 15-60 min.

5. The preparation method of the carbon nitride photocatalyst for dim light according to claim 1, characterized in that, The time for soaking and stirring is 1-3 h.

6. The carbon nitride photocatalyst for dim light prepared by the preparation method according to any one of claims 1-5.

7. The application of the carbon nitride photocatalyst for dim light as claimed in claim 6 in the preparation of hydrogen peroxide.

8. A method for producing hydrogen peroxide in dim light, characterized in that, It includes the following steps: Disperse the carbon nitride photocatalyst for dim light as claimed in claim 6 in an aqueous methanol solution to obtain a pale yellow suspension; Under closed conditions and in an inert atmosphere, irradiate the pale yellow suspension with a xenon lamp. After the pale yellow suspension turns into a blue suspension, transfer the blue suspension to a light-shielded condition for the hydrogen peroxide production reaction.

9. The method for producing hydrogen peroxide in dim light according to claim 8, wherein The volume ratio of methanol to water in the aqueous methanol solution is 1∶(5-15).

10. The method for producing hydrogen peroxide in low light according to claim 8, wherein, The concentration of the carbon nitride photocatalyst for dim light in the aqueous methanol solution is 0.18-0.75 mg / mL.

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