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Heteroelement-Containing Graphene

Foreign code F210010328
File No. AF39-05WO
Posted date Feb 1, 2021
Country United States of America
Application number 201816650964
Gazette No. 20200346933
Date of filing Sep 28, 2018
Gazette Date Nov 5, 2020
International application number JP2018036399
International publication number WO2019066013
Date of international filing Sep 28, 2018
Date of international publication Apr 4, 2019
Priority data
  • P2017-190683 (Sep 29, 2017) JP
  • 2018JP36399 (Sep 28, 2018) WO
Title Heteroelement-Containing Graphene
Abstract Provided is a highly crystalline heteroelement-containing graphene including carbon (C) and, as a heteroelement (X), at least one element selected from the group consisting of nitrogen (N), phosphorus (P), arsenic (As), sulfur (S), boron (B), and silicon (Si). Also, spots belonging to either the orthorhombic system or the hexagonal system and having the symmetry of a single crystal are observed in the selected area electron diffraction.
Outline of related art and contending technology BACKGROUND ART
Heteroelement-containing graphene in which heterogeneous elements other than carbon are introduced into the carbon six-membered ring structure of graphene has attracted attention. In the heteroelement-containing graphene, for example, when a heterogeneous element such as nitrogen is introduced into the valley portion of the zigzag edge of the graphene, the heterogeneous element acts physically and chemically on the adjacent carbon atoms. It is known that the adjacent carbon atoms develop oxygen reduction properties as a result. Therefore, utilization of heteroelement-containing graphene as a catalyst material has been studied (see, for example, Japanese Patent Laid-Open No. 2013-232409, Japanese Patent Laid-Open No. 2012-153555, and International Publication No. WO 2014/098251).
Japanese Patent Laid-Open No. 2013-232409 discloses an electrode catalyst support in which nitrogen-containing graphite is formed on a surface of a carbon support. The nitrogen-containing graphite of Japanese Patent Laid-Open No. 2013-232409 is formed on a surface of a carbon support which has n electron donor properties. Japanese Patent Laid-Open No. 2013-232409 further discloses that when the crystallinity of the nitrogen-containing graphite is evaluated by the ID/IG value based on the Raman spectrum, the ID/IG value is allowed to be 0.8 to 1.2.
Japanese Patent Laid-Open No. 2012-153555 discloses a heteroatom-containing graphene containing a heteroatom such as nitrogen, which can be synthesized by a solvothermal reaction. In the Examples of Japanese Patent Laid-Open No. 2012-153555, it is described that the heteroatom-containing graphene is doped with nitrogen atoms in a ratio of 14.8 atomic %. However, Japanese Patent Laid-Open No. 2012-153555 does not disclose anything about the crystallinity of the heteroatom-containing graphene.
International Publication No. WO 2014/098251 discloses graphite-like carbon nitride (g-C3N4) having a stoichiometric ratio. The graphite-like carbon nitride disclosed in International Publication No. WO 2014/098251 has a structure in which melon ((C6N9H3)X), which has a triangular crystal structure in which three 6-membered rings formed by nitrogen and carbon and sharing C—N bonds with each other, is polymerized through nitrogen atoms at its apexes.
In Japanese Patent Laid-Open No. 2014-100617, the present inventors provide a method for producing a heteroatom-containing carbon catalyst containing a large amount of nitrogen of 10 atomic % or more as a heterogeneous element. According to these methods, heteroatom-containing graphene containing no support can be produced.
Furthermore, Japanese Patent Laid-Open No. 2016-209798 discloses that a redox-active carbon catalyst is formed on an electrode.
In the heteroatom-containing graphene obtained in Japanese Patent Laid-Open No. 2012-153555 and Japanese Patent Laid-Open No. 2014-1006174, actually, the doping position of the heteroatoms on the graphene sheet tends to be biased toward the sheet edge (edge). Also, there is a problem in that even when the doping inside (in-plane) of the graphene sheet is allowed to be performed, the bonding angle between carbon and heteroatoms is disordered as the amount of nitrogen to be doped increases, so that the flatness of the graphene sheet is unable to be maintained. In other words, the graphene sheet doped with nitrogen atoms is not returned to the flat shape staying curved at the atomic level, so that a nitrogen-containing carbon catalyst having good crystallinity in terms of crystallography cannot be obtained. In view of the above problems, an object of the present invention is to provide a transparent and highly crystalline heteroelement-containing graphene that maintains the flatness of a graphene sheet even when the amount of nitrogen to be doped is increased.
Scope of claims [claim1]
1. A heteroelement-containing graphene comprising carbon (C) and, as a heteroelement (X), at least one element selected from the group consisting of nitrogen (N), phosphorus (P), arsenic (As), sulfur (S), boron (B), and silicon (Si), wherein spots belonging to either an orthorhombic system or a hexagonal system and having a symmetry of a single crystal are observed in selected area electron diffraction.

[claim2]
2. The heteroelement-containing graphene according to claim 1,
wherein the spots form an electron diffraction image belonging to the orthorhombic system with an incident direction of [101], the spots including an array of reciprocal lattice points 11-1, -111, -202, 1-1-1, 20-2, and -1-11.

[claim3]
3. The heteroelement-containing graphene according to claim 1, wherein a half width of a diffraction peak from (002) planes is 3 degrees or less in X-ray diffraction.

[claim4]
4. The heteroelement-containing graphene according to claim 3, wherein a ratio (I(101)/I(002)) of a diffraction peak intensity I(101) from (101) planes to a diffraction peak intensity I(002) from (002) planes is 0.1 or more in X-ray diffraction.

[claim5]
5. The heteroelement-containing graphene according to claim 3, wherein an interplanar spacing between the (002) planes is 3.5 Å or less in X-ray diffraction.

[claim6]
6. The heteroelement-containing graphene according to claim 1, wherein an atomic ratio (X/C) of the heteroelement (X) to carbon (C), calculated based on X-ray photoelectron spectroscopy, is 0.1 or more.

[claim7]
7. The heteroelement-containing graphene according to claim 1, wherein a possibility of a chemical bonding state of nitrogen doped to a basal plane being a chemical bonding state of cationic nitrogen can be indicated based on X-ray photoelectron spectroscopy, and it is determined by Hall effect measurement that a carrier type of the heteroelement-containing graphene is p-type.

[claim8]
8. The heteroelement-containing graphene according to claim 1, wherein a ratio (I(D)/I(G)) of an intensity I(D) of a D band seen in the vicinity of 1350 cm-1 to an intensity I(G) of a G band appearing in the vicinity of 1580 cm-1 is 1 or less and a half width of the G band is 50 cm-1 or less in Raman spectroscopic analysis with an excitation wavelength of 532 nm.

[claim9]
9. The heteroelement-containing graphene according to claim 1, wherein a ratio (I(2D)/I(G)) of an intensity I(2D) of a 2D band seen in the vicinity of 2700 cm-1 to the intensity I(G) of the G band is 0.5 or more in the Raman spectroscopic analysis.

[claim10]
10. The heteroelement-containing graphene according to claim 1, wherein a half width of the 2D band seen in the vicinity of 2700 cm-1 is 80 cm-1 or less in the Raman spectroscopic analysis.

[claim11]
11. The heteroelement-containing graphene according to claim 1, which does not include a base material that supports the heteroelement-containing graphene.

[claim12]
12. The heteroelement-containing graphene according to claim 1, comprising a graphene sheet configured such that atoms of the carbon (C) are chemically bonded to atoms of the heteroelement (X) and atoms of the carbon (C) are principally sp2-bonded to each other,
wherein the graphene sheet has a single-layer structure formed by one layer or a stacked structure of two or more and five or less layers.

[claim13]
13. The heteroelement-containing graphene according to claim 1, which is a powder having an average particle size of 1 nm or more and 10 μm or less.

[claim14]
14. A method for producing a heteroelement-containing graphene comprising carbon (C) and, as a heteroelement (X), at least one element selected from the group consisting of nitrogen (N), phosphorus (P), arsenic (As), sulfur (S), boron (B), and silicon (Si), wherein spots belonging to either an orthorhombic system or a hexagonal system and having a symmetry of a single crystal are observed in selected area electron diffraction, the method comprising:
dissolving a hetero 5-membered ring compound having, at least partially, a 5-membered ring structure in a polar aprotic solvent to prepare a raw material-containing liquid, wherein the 5-membered ring is formed by carbon (C) and the heteroelement (X), which is at least one selected from the group consisting of nitrogen (N), phosphorus (P), arsenic (As), sulfur (S), boron (B), and silicon (Si); and
generating plasma in the raw material-containing liquid to polymerize the hetero 5-membered ring compound, thereby obtaining the heteroelement-containing graphene.

[claim15]
15. The heteroelement-containing graphene according to claim 2, wherein a half width of a diffraction peak from (002) planes is 3 degrees or less in X-ray diffraction.

[claim16]
16. The heteroelement-containing graphene according to claim 4, wherein an interplanar spacing between the (002) planes is 3.5 Å or less in X-ray diffraction.
  • Inventor, and Inventor/Applicant
  • SAITO NAGAHIRO
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
IPC(International Patent Classification)
Reference ( R and D project ) CREST Establishment of molecular technology towards the Creation of New Functions AREA
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