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US-12617682-B2 - Direct synthesis of improved superhydrophobic carbon nitride co-products, and improved superhydroppbic carbon nitride co-products thereof

US12617682B2US 12617682 B2US12617682 B2US 12617682B2US-12617682-B2

Abstract

The present invention is concerned with a method of direct synthesis of co-products of at a first co-product and a second co-product. The first co-product is superhydrophilic carbon nitride thin film and the second co-product is superhydrophilic carbon nitride powder. The method has a step of using a guanidine carbonate salt as a precursor material. The present invention is also concerned with carbon nitride co-products. The carbon nitride co-products has a first co-product of superhydrophilic carbon nitride thin film and a second co-product of superhydrophilic carbon nitride powder. The superhydrophilic carbon nitride thin film has chemical formula of CN x , wherein x is 0.86-1.04, and the superhydrophilic carbon nitride powder has a chemical formula of g-C 3 N 4 .

Inventors

  • Thuc Hue LY
  • Quoc Huy THI
  • Ping MAN

Assignees

  • CITY UNIVERSITY OF HONG KONG

Dates

Publication Date
20260505
Application Date
20230523

Claims (19)

  1. 1 . A method of direct synthesis of co-products of at least a first co-product and a second co-product, wherein the first co-product is superhydrophilic carbon nitride thin film with a water contact angle of 0-5° and the second co-product is superhydrophilic carbon nitride powder, comprising the steps of: placing a precursor material on one end of a container, wherein the precursor material is a guanidine, placing a glass substrate in the container, wherein the glass substrate is positioned away from the precursor material such that there is a clearance between the precursor material and the glass substrate, placing the container in a furnace and subjecting the precursor material to heating, and allowing the first co-product to form on the glass substrate and the second co-product to form at the other end of the container.
  2. 2 . A method as claimed in claim 1 , wherein the superhydrophilic carbon nitride thin film has a chemical formula of CN x , and the superhydrophilic carbon nitride powder has a chemical formula of g-C 3 N 4 , wherein x is 0.86-1.04.
  3. 3 . A method as claimed in claim 1 , wherein the water contact angle is 4.5°.
  4. 4 . A method as claimed in claim 1 , wherein the superhydrophilic carbon nitride thin film on its surface has an oxygen-carbon ratio of 0.01-0.63.
  5. 5 . A method as claimed in claim 4 , wherein the superhydrophilic carbon nitride thin film on its surface has an oxygen-carbon ratio of 0.63.
  6. 6 . A method as claimed in claim 1 , wherein the guanidine carbonate salt has a chemical formula of NH 2 C(═NH) NH 2 ·½H 2 CO 3 ).
  7. 7 . A method as claimed in claim 1 , comprising a step of subjecting the precursor material in the container to chemical vapor deposition (CVD).
  8. 8 . A method as claimed in claim 1 , comprising the steps of: providing a reaction tube acting as a reaction chamber defining opposite open lateral ends, with one end receiving a flow of gas and the opposite end allowing, after reaction, the flow of gas to exit, wherein the opposite end is filled with a one-way valve for preventing backflow, placing a predetermined amount of the guanidine carbonate salt on the bottom of the reaction tube, providing a growth substrate and putting the growth substrate in the reaction tube such that there is a clearance of 1-5 cm between the growth substrate and the guanidine carbonate salt, subjecting the reaction chamber to heat in a furnace, subjecting the reaction chamber to the flow of gas therethrough and allowing the reaction to take place for a predetermined amount of time at a predetermined temperature, and allowing annealing to complete and collecting the first co-product superhydrophilic carbon nitride thin film on the growth substrate and the second co-product superhydrophilic carbon nitride powder at the opposite end of the reaction tube.
  9. 9 . A method as claimed in claim 8 , wherein the flow of gas is dry and consists of nitrogen, oxygen, argon and carbon dioxide.
  10. 10 . A method as claimed in claim 8 , wherein reaction tube has a diameter tube of 8-15 cm.
  11. 11 . A method as claimed in claim 8 , wherein the amount of guanidine carbonate salt placed in the reaction tube is 0.5 g to 1.5 g.
  12. 12 . A method as claimed in claim 8 , wherein the guanidine carbonate salt is located in the center of the heating zone of the furnace, and the growth substrate is located downstream of the heating zone in the reactive tube.
  13. 13 . A method as claimed in claim 8 , wherein the flow of gas has a rate in the range of 50 sccm to 200 sccm.
  14. 14 . A method as claimed in claim 8 , wherein the reaction takes place with an initial ramping time of 30 to 60 min, following by a subsequent annealing time of 1 to 6 hrs at 450-600° C.
  15. 15 . A combination of a first co-product of superhydrophilic carbon nitride thin film and a second co-product of superhydrophilic carbon nitride powder, wherein the superhydrophilic carbon nitride thin film has chemical formula of CN x , wherein x is 0.86-1.04, and the superhydrophilic carbon nitride powder has a chemical formula of g-C 3 N 4 .
  16. 16 . Carbon nitride co-products as claimed in claim 15 , wherein the superhydrophilic carbon nitride thin film has a water contact angle of 0-5°.
  17. 17 . Carbon nitride co-products as claimed in claim 16 , wherein the water contact angle of 4.5°.
  18. 18 . Carbon nitride co-products as claimed in claim 15 , wherein the superhydrophilic carbon nitride thin film on its surface has an oxygen-carbon ratio of 0.01-0.63.
  19. 19 . Carbon nitride co-products as claimed in claim 18 , wherein oxygen-carbon ratio is 0.63.

Description

FIELD OF THE INVENTION The present invention is concerned with a method of direct synthesis of superhydrophilic carbon nitride co-products, and superhydrophilic carbon nitride co-products thereof. BACKGROUND OF THE INVENTION The following discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge as at the priority date of the application. Carbon nitride (CNx) type materials are can be used as metal-free photocatalysts for water splitting, energy storage and water filtration membranes. Their prolific allotropes with rich surface properties offers a high flexibility in structural and property modification, e.g., bandgap modulations by surface functionalization or carbon/nitrogen (C/N) ratio. However, the rich allotropes make it difficult to directly modify the properties during synthesis process, as a little change may lead to varied and unpredictable products. Meanwhile, the functionalization could be realized by second-time growth or post-treatment to convert the common structure like graphitic carbon nitrides (g-C3N4) to the desired structures, however, with long processing time, high production loss and inevitable hazardous chemical usage. Unfortunately, most of the conventional carbon-based materials such as graphene and its analogous are hydrophobic owing to their large inert surfaces. Doping nitrogen to carbon-based structure or implanting oxygen-based functional groups on surfaces can increase the hydrogen bonding between surface and water molecules. Note that the CNx materials are alternative metal-free photocatalysts with narrow bandgap. Previous literature has reported that contact angle (CA) between water and the ideal condensed g-C3N4 was 53.5°, meanwhile the two-dimensional (2D) CNx thin films prepared by bottom-up growth had water wettability of 60° to 80°. The CNx film could be converted to hydrophobic by increasing surface porosity, resulted from the modification of precursor ratio or the source-substrate distances. However, the superhydrophilic 2D CNx or g-C3N4 membranes have not been acquired yet by direct synthesis. Alternatively, the post-synthesis functionalized CNx surfaces with oxygenated molecules did improve the hydrophilicity, but their CA with water was still over 24°. Moreover, embedding functional groups after synthesis caused unwanted disruptions to the initial lattice structure that significantly reduced their durability. The carbon nitrides can be simply obtained by doping nitrogen into graphite. Besides, thermal polymerization of melamine (C3N3 (NH2)3) or other N-rich compounds like urea (CN2OH4), cyanamide (CN2H2) and its dimer (Dicyandiamide, C2N4H4) can produce the powder of g-C3N4. However, these methods cannot control the surface wettability of products directly but required some complicated post-treatments to functionalize the origin surface. Further, while conventional methodologies may produce carbon nitride membranes, they are not able to achieve this by way of direct synthesis. In fact, while the post-synthesis functionalized CNx surfaces with oxygenated molecules may improve the hydrophilicity but then it undesirably causes unwanted disruptions to the initial lattice structure that significantly reduces their durability. The present invention seeks to provide new synthesis method that can spontaneously yield superhydrophilic surface is essential and pressing, or at least to provide alternatives to the public. SUMMARY OF THE INVENTION According to a first aspect of the present invention, there is provided a method of direct synthesis of co-products of a first co-product and a second co-product, wherein the first co-product is superhydrophilic carbon nitride thin film and the second co-product is superhydrophilic carbon nitride powder, comprising a step of using a guanidine carbonate salt as a precursor material. Preferably, the superhydrophilic carbon nitride thin film may have a chemical formula of CNx, wherein x is 0.86-1.04, and the superhydrophilic carbon nitride powder has a chemical formula of g-C3N4. By direct synthesis, it means there is no intermediate steps. Preferably, the superhydrophilic carbon nitride thin film may have a water contact angle of 0-5°. In an embodiment, the water contact angle may be of 4.5°. Suitably, the superhydrophilic carbon nitride thin film on its surface may have an oxygen-carbon ratio of 0.01-0.63. In an embodiment, the superhydrophilic carbon nitride thin film on its surface may have an oxygen-carbon ratio of 0.63. Advantageously, the guanidine carbonate salt may have a chemical formula of NH2C(═NH) NH2·½H2CO3). In one embodiment, the method may make use of chemical vapor deposition (CVD). In a preferred embodiment, the method may comprise the steps of i) providing a reaction tube acting as a reaction chamber defining op