High-crystallinity carbon nitride colloid as well as preparation method and application thereof

Abstract

The invention discloses high-crystallinity carbon nitride colloid as well as a preparation method and application thereof. The preparation method comprises the following steps: uniformly mixing guanidine hydrochloride and potassium thiocyanate in an air-containing closed environment, calcining at 520-575 DEG C, and adding water to disperse. The specific raw materials guanidine hydrochloride and potassium thiocyanate are adopted, the product prepared through a specific process has high crystallinity, hydrophilicity and stability and further has excellent photocatalytic performance, and especially in catalysis of hydrogen production through water decomposition, the average hydrogen production activity within 5 h reaches up to 235.4 micromol.h <-1 > (17.1 times of that of bulk phase carbon nitride).

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalysis, and particularly relates to a high-crystallinity carbon nitride colloid and a preparation method and application thereof. BACKGROUND

[0002] As a kind of polymer semiconductor material constructed by different valence states of nitrogen and carbon atoms, bulk carbon nitride has attracted much attention in the field of photocatalytic materials due to its special electronic-optical structure, high chemical stability and band gap width conducive to visible light absorption. However, the traditional bulk carbon nitride is prone to aggregation in water and has low crystallinity, resulting in serious recombination of photo-generated carriers and limited photocatalytic activity. To solve this problem, researchers disperse it in a liquid medium to form a colloid, which inhibits aggregation through steric hindrance effect and builds a quasi-homogeneous photocatalytic system.

[0003] At present, the mainstream method for preparing carbon nitride colloid is to treat bulk carbon nitride with strong acid or strong base. However, the carbon nitride colloid prepared by this method often introduces too many defect sites and has poor crystallinity, which greatly reduces its photocatalytic activity.

[0004] Therefore, it has become an urgent problem in the field to develop a preparation method for carbon nitride colloid with high crystallinity. SUMMARY

[0005] The present application aims to provide a preparation method for carbon nitride colloid with high crystallinity. The carbon nitride colloid with high crystallinity prepared by the method using specific raw material guanidine hydrochloride and potassium thiocyanate not only can maintain high dispersion in aqueous solution for a long time and is not prone to aggregation, but also has high crystallinity and exhibits excellent photocatalytic performance.

[0006] The first object of the present application is to provide a preparation method for carbon nitride colloid with high crystallinity.

[0007] The second object of the present application is to provide carbon nitride colloid with high crystallinity prepared by the method.

[0008] The third object of the present application is to provide the application of the carbon nitride colloid with high crystallinity as and / or in the preparation of photocatalysts.

[0009] The fourth object of the present application is to provide the application of the carbon nitride colloid with high crystallinity as and / or in the preparation of photocatalysts for decomposing water to produce hydrogen.

[0010] The fifth object of the present application is to provide a photocatalyst.

[0011] The sixth object of the present application is to provide a method for decomposing water to produce hydrogen.

[0012] The above objects of the present application are achieved by the following technical solutions: This invention provides a method for preparing highly crystalline carbon nitride colloid, specifically: in a closed environment containing air, guanidine hydrochloride and potassium thiocyanate are mixed, calcined at 520-575 °C, and then dispersed with water to obtain the colloid.

[0013] The term "closed environment containing air" means that calcination utilizes only the air already present in the closed environment, without introducing any new air. For example, guanidine hydrochloride and potassium thiocyanate are added to a container and mixed thoroughly. The container is then sealed (preserving the original air, without vacuuming or other operations), and calcination is carried out without adding any new gas during the calcination process.

[0014] Preferably, the molar ratio of guanidine hydrochloride to potassium thiocyanate is (0.8-1.2):(1.3-1.7).

[0015] Furthermore, the molar ratio of guanidine hydrochloride to potassium thiocyanate is 1:1.5.

[0016] Preferably, the calcination temperature is 540–560 °C.

[0017] Furthermore, the calcination temperature is 550 °C.

[0018] Preferably, the calcination time is 2 to 4 hours.

[0019] Furthermore, the calcination time is 3 hours.

[0020] Preferably, the ratio of the calcined product to water is 3-5 g: 30-60 mL.

[0021] Preferably, the dispersion is further cooled beforehand.

[0022] Furthermore, the endpoint of the cooling is 20–30 °C.

[0023] Preferably, the dispersion is achieved by stirring, such as stirring at 300–400 rpm.

[0024] Preferably, after dispersion, post-processing is performed, such as sequential removal of potassium ions and removal of water.

[0025] Furthermore, the method for removing potassium ions is dialysis.

[0026] More preferably, the dialysis is performed using water as the dialysis fluid and a dialysis membrane, such as a 500 Da dialysis membrane.

[0027] Furthermore, the method for removing water is freeze drying.

[0028] More preferably, the freeze-drying temperature is -60 to -50 °C, for example -56 °C.

[0029] Preferably, the sealing is achieved by wrapping the reaction vessel with aluminum foil or graphite paper.

[0030] Furthermore, the sealing is achieved by wrapping the reaction vessel with aluminum foil.

[0031] The highly crystalline carbon nitride colloid prepared by the above method not only maintains high dispersion in aqueous solution for a long time and is not prone to aggregation, but also has high crystallinity and good hydrophilicity, exhibiting excellent photocatalytic performance. Especially in the catalysis of water splitting for hydrogen production, the average hydrogen production activity reaches as high as 235.4 μmol·h⁻¹ within 5 h. -1 (17.1 times that of bulk carbon nitride). Therefore, this invention also protects the highly crystalline carbon nitride colloid prepared by the above method, the use of the highly crystalline carbon nitride colloid as a photocatalyst, the use of the highly crystalline carbon nitride colloid as a photocatalyst for water splitting to produce hydrogen, and photocatalysts containing the highly crystalline carbon nitride colloid, all of which should be within the scope of protection of this invention.

[0032] Based on this, the present invention also provides a method for producing hydrogen by splitting water, specifically: using the highly crystalline carbon nitride colloid or the photocatalyst.

[0033] The present invention has the following beneficial effects: 1. This invention utilizes specific raw materials, guanidine hydrochloride and potassium thiocyanate, and through a specific process, yields a product with high crystallinity, hydrophilicity, and stability, thus exhibiting excellent photocatalytic performance. Particularly in the catalysis of water splitting for hydrogen production, the average hydrogen production activity reaches as high as 235.4 μmol·h⁻¹ within 5 hours. -1 (17.1 times that of bulk carbon nitride).

[0034] 2. The raw materials used in this invention are widely available and inexpensive, and the preparation method is simple, which is conducive to large-scale production. Attached Figure Description

[0035] Figure 1 This is a diagram of the Tyndall effect in Example 2.

[0036] Figure 2 The X-ray diffraction patterns are of the products obtained in Example 2 and Comparative Examples 1-5.

[0037] Figure 3 The fluorescence spectra of the products obtained in Example 2 and Comparative Examples 1-2 are shown.

[0038] Figure 4 The results are Fast Fourier Transform tests of the products obtained in Example 2 and Comparative Example 2.

[0039] Figure 5 The Fourier transform infrared spectra of the products obtained in Example 2 and Comparative Examples 1-2 are shown.

[0040] Figure 6 The particle size distribution of the product obtained in Example 2 is shown.

[0041] Figure 7 The results are the Zeta potential test results of the product obtained in Example 2.

[0042] Figure 8 The images shown are scanning electron microscope (SEM) images of the products obtained in Example 2, Comparative Example 1, and Comparative Example 5. Figure 8 In the image, A is a scanning electron microscope (SEM) image of product CN obtained in Comparative Example 1. Figure 8 B in the image is a scanning electron microscope image of the HCN product obtained in Example 2. Figure 8 C in the image is a scanning electron microscope image of the product obtained in Comparative Example 5.

[0043] Figure 9 Transmission electron microscopy (TEM) images of the products obtained in Example 2 and Comparative Example 2.

[0044] Figure 10 The results are the photocatalytic performance test results of the products obtained in Example 2, Comparative Example 1, and Comparative Example 2. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0046] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0047] Example 1: Preparation of highly crystalline carbon nitride colloids 30 mol of guanidine hydrochloride and 45 mol of potassium thiocyanate were weighed and ground until homogeneous. The homogeneous powder was placed in an alumina crucible, wrapped with aluminum foil, and calcined in an air furnace at 540 °C for 3 h. After natural cooling to room temperature (25 °C), 4 g of sample was taken out and 40 mL of water was added. The mixture was stirred at 300 rpm to disperse the sample, resulting in a highly crystalline carbon nitride colloidal solution. The carbon nitride colloidal solution was dialyzed with water using a dialysis membrane with a molecular cutoff of 500 Da to separate potassium ions. The water was then removed by freeze-drying at -56 °C to obtain the product, highly crystalline carbon nitride colloid, labeled as HCN.

[0048] Example 2 Preparation of highly crystalline carbon nitride colloids 30 mol of guanidine hydrochloride and 45 mol of potassium thiocyanate were weighed and ground until homogeneous. The homogeneous powder was placed in an alumina crucible, wrapped with aluminum foil, and calcined in an air furnace at 550 °C for 3 h. After natural cooling to room temperature (25 °C), 4 g of sample was taken out and 40 mL of water was added. The mixture was stirred at 300 rpm to disperse the sample, resulting in a highly crystalline carbon nitride colloidal solution. The carbon nitride colloidal solution was dialyzed with water using a dialysis membrane with a molecular cutoff of 500 Da to separate potassium ions. The water was then removed by freeze-drying at -56 °C to obtain the product, highly crystalline carbon nitride colloid, labeled as HCN.

[0049] Example 3 Preparation of highly crystalline carbon nitride colloids 30 mol of guanidine hydrochloride and 45 mol of potassium thiocyanate were weighed and ground until homogeneous. The homogeneous powder was placed in an alumina crucible, wrapped with aluminum foil, and calcined in an air furnace at 560 °C for 3 h. After natural cooling to room temperature (25 °C), 4 g of sample was taken out, and 40 mL of water was added and stirred at 300 rpm to disperse the sample, resulting in a highly crystalline carbon nitride colloidal solution. The carbon nitride colloidal solution was dialyzed with water using a dialysis membrane with a molecular cutoff of 500 Da to separate potassium ions. Subsequently, water was removed by freeze-drying at -56 °C to obtain the product, highly crystalline carbon nitride colloid, labeled as HCN.

[0050] Example 4 Preparation of highly crystalline carbon nitride colloids 30 mol of guanidine hydrochloride and 63.75 mol of potassium thiocyanate were weighed and ground until homogeneous. The homogeneous powder was placed in an alumina crucible, wrapped with aluminum foil, and calcined in an air furnace at 520 °C for 4 h. After natural cooling to room temperature (25 °C), 5 g of sample was taken out and 60 mL of water was added. The mixture was stirred at 400 rpm to disperse the sample, resulting in a highly crystalline carbon nitride colloidal solution. The carbon nitride colloidal solution was dialyzed with water using a dialysis membrane with a molecular cutoff of 500 Da to separate potassium ions. The water was then removed by freeze-drying at -56 °C to obtain the product, highly crystalline carbon nitride colloid, labeled as HCN.

[0051] Example 5 Preparation of highly crystalline carbon nitride colloids 30 mol of guanidine hydrochloride and 32.5 mol of potassium thiocyanate were weighed and ground until homogeneous. The homogeneous powder was placed in an alumina crucible, wrapped with aluminum foil, and calcined in an air furnace at 575 °C for 2 h. After natural cooling to room temperature (25 °C), 3 g of sample was taken out, and 30 mL of water was added and stirred at 300 rpm to disperse the sample, resulting in a highly crystalline carbon nitride colloidal solution. The carbon nitride colloidal solution was dialyzed with water using a dialysis membrane with a molecular cutoff of 500 Da to separate potassium ions. Subsequently, water was removed by freeze-drying at -56 °C to obtain the product, highly crystalline carbon nitride colloid, labeled as HCN.

[0052] Comparative Example 1 30 mol of guanidine hydrochloride was weighed and placed in an alumina crucible. The crucible was wrapped with aluminum foil and calcined in an air furnace at 550 °C for 3 h. After naturally cooling to room temperature (25 °C), the sample was taken out and ground to obtain the product, bulk carbon nitride, which was labeled as CN.

[0053] Comparative Example 2 Same as Example 2, except that potassium thiocyanate is replaced with potassium chloride, as follows: 30 mol of guanidine hydrochloride and 45 mol of potassium chloride were weighed and ground to mix evenly. The mixed powder was placed in an alumina crucible, wrapped with aluminum foil, and calcined in an air furnace at 550 °C for 3 h. After natural cooling to room temperature (25 °C), 4 g of sample was taken out, and 40 mL of water was added and stirred at 300 rpm to disperse. The sample was then dialyzed with water using a dialysis membrane with a molecular cutoff of 500 Da to separate potassium chloride. Subsequently, water was removed by freeze drying at -56 °C to obtain the product, low-crystallinity carbon nitride colloid, labeled as LCN.

[0054] Comparative Example 3 Same as Example 2, except that potassium thiocyanate is replaced with sodium thiocyanate, as detailed below: 30 mol of guanidine hydrochloride and 45 mol of sodium thiocyanate were weighed and ground to form a homogeneous mixture. The homogeneous powder was placed in an alumina crucible, wrapped with aluminum foil, and calcined in an air furnace at 550 °C for 3 h. After natural cooling to room temperature (25 °C), 4 g of sample was taken out, and 40 mL of water was added and stirred at 300 rpm to disperse the sample. The sample was then dialyzed with water using a dialysis membrane with a molecular weight cutoff of 500 Da to separate sodium ions. Subsequently, water was removed by freeze-drying at -56 °C to obtain the product.

[0055] Comparative Example 4 Same as Example 2, except that the calcination is carried out in a non-sealed environment, that is, the alumina crucible is not wrapped with aluminum foil, as detailed below: 30 mol of guanidine hydrochloride and 45 mol of potassium thiocyanate were weighed and ground to form a homogeneous mixture. The homogeneous powder was placed in an alumina crucible and calcined in an air furnace at 550 °C for 3 h. After natural cooling to room temperature (25 °C), 4 g of sample was taken out, and 40 mL of water was added and stirred at 300 rpm to disperse the sample. The sample was then dialyzed with water using a dialysis membrane with a molecular cutoff of 500 Da to separate potassium ions. Subsequently, water was removed by freeze drying at -56 °C to obtain the product.

[0056] Comparative Example 5 Same as Example 2, except that the calcination is carried out under an argon atmosphere, as detailed below: 30 mol of guanidine hydrochloride and 45 mol of potassium thiocyanate were weighed and ground to form a homogeneous mixture. The homogeneous powder was placed in a boat of a tube furnace and calcined at 550 °C for 3 h under an argon atmosphere. After natural cooling to room temperature (25 °C), 4 g of sample was taken out, and 40 mL of water was added and stirred at 300 rpm to disperse the sample. The sample was then dialyzed with water using a dialysis membrane with a molecular cutoff of 500 Da to separate potassium ions. Subsequently, water was removed by freeze drying at -56 °C to obtain the product.

[0057] Test Example 1: Tyndall Effect Test Take 4 mg of the products obtained in Examples 1-5 and Comparative Examples 1-5 and disperse them in 20 mL of water to observe whether the Tyndall effect exists.

[0058] It can be seen that the products obtained in Examples 1-5 and Comparative Example 4 all exhibit the Tyndall effect, while the products obtained in Comparative Examples 1-3 and Comparative Example 5 do not exhibit the Tyndall effect. That is, only the products obtained in Examples 1-5 and Comparative Example 4 are colloids (wherein, the Tyndall effect diagram of Example 2 is shown in Figure 1). Figure 1 (As shown). Furthermore, the products obtained in Examples 1-5 are pale yellow in color and generally exhibit good absorption of visible light, making them suitable as catalysts; while the product obtained in Comparative Example 4 is white in color and cannot absorb visible light, making it unsuitable as a catalyst. These results indicate that the products obtained by the present invention using specific raw materials, guanidine hydrochloride and potassium thiocyanate, through a specific process, are colloids suitable as catalysts.

[0059] Test Example 2: X-ray Diffraction Test The products obtained in Examples 1-5 and Comparative Examples 1-5 were tested using an X-ray powder diffractometer D8 (Prouk).

[0060] The X-ray diffraction patterns of the products obtained in Examples 1-5 are similar; therefore, only the X-ray diffraction patterns of the products obtained in Example 2 and Comparative Examples 1-5 are presented. The results are as follows: Figure 2 As shown.

[0061] It is evident that the XRD peak intensities of the products obtained in Examples 1-5 are significantly higher than those in Comparative Examples 1-5, indicating that the products obtained in Examples 1-5 have higher crystallinity. This demonstrates that the products prepared by the present invention using specific raw materials, guanidine hydrochloride and potassium thiocyanate, through a specific process have higher crystallinity and thus exhibit excellent photocatalytic performance.

[0062] Test Example 3: Fluorescence Spectroscopy Test The products obtained in Example 2 and Comparative Examples 1-2 were tested using a fluorescence spectrometer FLS1000 (Eisburg).

[0063] The results are as follows Figure 3 As shown, the fluorescence intensity of the HCN product obtained in Example 2 is significantly lower than that of the products obtained in Comparative Examples 1 and 2, indicating that the product obtained by the present invention using specific raw materials guanidine hydrochloride and potassium thiocyanate through a specific process has high crystallinity and thus excellent photocatalytic performance.

[0064] Test Example 4: Fast Fourier Transform Test The products obtained in Example 2 and Comparative Example 2 were tested using a transmission electron microscope JEOL-2100F / F200 (Japan).

[0065] The results are as follows Figure 4 As shown, the HCN product obtained in Example 1 exhibits a strong iris and numerous small white dots, indicating that its molecular arrangement is highly periodic and has high crystallinity. In contrast, the LCN product obtained in Comparative Example 2 lacks these characteristics, meaning it lacks a periodic lattice. This demonstrates that the product obtained by using specific raw materials, guanidine hydrochloride and potassium thiocyanate, through a specific process, possesses high crystallinity and thus exhibits excellent photocatalytic performance.

[0066] Test Example 5: Fourier Transform Infrared Spectroscopy Test The products obtained in Example 2 and Comparative Examples 1-2 were tested using a Nicolet 6700 Fourier transform infrared spectrometer (USA).

[0067] The results are as follows Figure 5 As shown, the products obtained in Example 2 and Comparative Examples 1-2 have a viscosity of 1200-1700 cm⁻¹. -1 There are obvious vibrational peaks within the range, corresponding to the stretching vibration peaks of the C,N-heterocyclic heptamethazine unit; the CN of the product obtained in Comparative Example 1 has a peak at 3000–3400 cm⁻¹. -1 The broad wavelength range is caused by the stretching mode of the amino group (-NHx), and the intensity of the amino group is weakened in the HCN product obtained in Example 2; compared with the CN product obtained in Comparative Example 1, the HCN product obtained in Example 2 and the LCN product obtained in Comparative Example 2 have a lower wavelength range at 2180 cm⁻¹. -1Strong diffraction peaks (attributed to the strong absorption peaks of the terminal cyano group) appeared at all locations, with a peak at 1130 cm⁻¹. -1 Each also exhibits a small absorption peak (attributed to the -KNC2 asymmetric absorption peak), in the range of 3400–3600 cm⁻¹. -1 The presence of strong diffraction peaks (attributed to stretching vibration peaks of hydroxyl groups) within the range indicates that the product HCN obtained in Example 2 and the product LCN obtained in Comparative Example 2 both contain hydrophilic hydroxyl groups, while the product CN obtained in Comparative Example 1 does not contain hydroxyl groups. This indicates that the product prepared by the present invention using specific raw materials guanidine hydrochloride and potassium thiocyanate through a specific process has high hydrophilicity and thus excellent photocatalytic performance.

[0068] Test Example 6: Particle Size Distribution and Zeta Potential Testing The particle size distribution and zeta potential of the products obtained in Examples 1-5 were determined using a Zetasizer Nano ZS 90 (USA) nanoparticle size potentiometer.

[0069] The results showed that the particle size distribution of the products obtained in Examples 1-5 was very close to the Zeta potential. Therefore, only the results of Example 2 are provided here. Figures 6-7 As shown, where, Figure 6 The particle size distribution of the product obtained in Example 2 is shown below. Figure 7 The zeta potential test results are shown for the product obtained in Example 2. It can be seen that the average particle size of the product obtained in Example 2 is approximately 145 nm, with the particle size mainly concentrated around 100 nm. This indicates that the HCN particle size is moderate and exhibits significant negative charge, demonstrating that the product prepared using specific raw materials, guanidine hydrochloride and potassium thiocyanate, through a specific process is less prone to aggregation and has better stability. This facilitates the provision of more reactive sites, resulting in excellent photocatalytic performance.

[0070] Test Example 7: Scanning Electron Microscopy Observation The products obtained in Example 2, Comparative Example 1, and Comparative Example 5 were observed using a scanning electron microscope JSM-7610F (Japan Electronics Corporation).

[0071] The results are as follows Figure 8 As shown, where, Figure 8 In the image, A is a scanning electron microscope (SEM) image of product CN obtained in Comparative Example 1. Figure 8 B in the image is a scanning electron microscope image of the HCN product obtained in Example 2. Figure 8C in the figure is a scanning electron microscope image of the product obtained in Comparative Example 5. It can be seen that the product HCN obtained in Example 2 is a relatively uniform nanoparticle, while the product CN obtained in Comparative Example 1 has a bulky morphology. The product obtained in Comparative Example 5 has a larger size, indicating that the product obtained by the present invention using specific raw materials guanidine hydrochloride and potassium thiocyanate through a specific process is not prone to agglomeration and has better stability, which is conducive to providing more reactive sites and thus has excellent photocatalytic performance.

[0072] Test Example 8: Observation using transmission electron microscopy The products obtained in Example 2 and Comparative Example 2 were observed using a transmission electron microscope JEOL-2100F / F200 (Japan).

[0073] The results are as follows Figure 9 As shown, the HCN product obtained in Example 2 is in the form of nanoparticles, while the LCN product obtained in Comparative Example 2 is in the form of nanosheets. This indicates that the product obtained by the present invention using specific raw materials, guanidine hydrochloride and potassium thiocyanate, through a specific process is not prone to agglomeration and has better stability, which is beneficial to providing more reactive sites and thus has excellent photocatalytic performance.

[0074] Test Example 9: Photocatalytic Performance Test 40 mg of HCN obtained in Example 2, CN obtained in Comparative Example 1, and LCN obtained in Comparative Example 2 were dispersed in 80 mL of 10% ( v / v In a triethanolamine solution, Pt is then photodeposited onto carbon nitride using chloroplatinic acid in situ, and finally, a visible light (λ>400 nm) catalytic reaction is carried out in an up-illuminated reactor.

[0075] The results are as follows Figure 10 As shown, the average hydrogen production activity of the HCN product obtained in Example 2 within 5 h is 235.4 μmol·h⁻¹. -1 The average hydrogen production activity of CN obtained in Comparative Example 1 is 17.1 times that of LCN obtained in Comparative Example 2, and the average hydrogen production activity of LCN obtained in Comparative Example 2 is 3.5 times that of HCN obtained in Comparative Example 2. This means that the product HCN obtained in Example 2 has a higher efficiency in splitting water to produce hydrogen, indicating that the product obtained by the present invention using specific raw materials guanidine hydrochloride and potassium thiocyanate through a specific process has excellent photocatalytic performance.

[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for producing a high-crystallinity carbon nitride colloid, characterized by, In a closed environment containing air, guanidine hydrochloride and potassium thiocyanate are mixed and calcined at 520-575 ℃, and then dispersed with water to obtain the product.

2. The method of claim 1, wherein, The molar ratio of guanidine hydrochloride to potassium thiocyanate is (0.8-1.2):(1.3-1.7).

3. The method of claim 1, wherein, The calcination temperature is 540-560 ℃.

4. The method of claim 1, wherein, The calcination time is 2-4 h.

5. The method of claim 1, wherein, The ratio of the calcination product to water is 3-5 g:30-60 mL.

6. The high-crystallinity carbon nitride colloidal prepared by the method of any one of claims 1-5.

7. The use of the high-crystallinity carbon nitride colloidal of claim 6 as and / or for preparing a photocatalyst.

8. The use of the high-crystallinity carbon nitride colloidal of claim 6 as and / or for preparing a photocatalyst for decomposing water to produce hydrogen.

9. A photocatalyst characterized by comprising: A photocatalyst containing the high-crystallinity carbon nitride colloidal of claim 6.

10. A method of decomposing water to produce hydrogen, characterized by, The use of the high-crystallinity carbon nitride colloidal of claim 6 or the photocatalyst of claim 9.

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