Method of manufacturing nanoporous graphene membrane

1. A method of manufacturing a porous graphene membrane, comprising:

a first step of oxidizing a surface of multilayer graphene, wherein the multilayer graphene is placed under an environment with oxygen-based radicals for oxidation of the surface of multilayer graphene, and the surface of multilayer graphene is oxidized in a randomly dispersed form by lowering an oxidation amount so as not to completely oxidize the entire surface;

a second step of reducing the oxidized surface of the multilayer graphene to carry out reductive etching of oxidized carbon atoms in a randomly dispersed form; and

a third step of repeatedly performing a series of the first and the second steps at least twice until nanopores having diameter of 0.4 to 100 nm are formed in the multilayer graphene, wherein the number of repetitions is adjusted until nanopores penetrating the multilayer graphene are formed.

2. The method of claim 1 , wherein the multilayer graphene consists of 10 layers or less.

3. The method of claim 1 , wherein the multilayer graphene has a polycrystalline form.

4. The method of claim 1 , wherein the oxygen-based radical is at least any one selected from the group consisting of an O radical, an O 2 radical, an O 3 radical (ozone), a OH radical, and a combination thereof.

5. The method of claim 1 , wherein the nanopores penetrating the multilayer graphene have an average diameter of less than 10 nm when viewed in a direction perpendicular to a graphene face.

6. The method of claim 1 , wherein, in the third step, the number of repetitions is adjusted to a time point at which the nanopores are formed in a first layer of the multilayer graphene and the nanopores are not formed in a second layer of the multilayer graphene.

7. The method of claim 1 , further comprising:

a process of passivating a broken binding part of edge carbon atoms, which is formed by the reductive etching of the second step, if returning from the second step to the first step for a repeated process of the third step.

8. The method of claim 1 , wherein, in the first and second steps, oxidative and reductive etching processes are carried out on only a surface multilayer graphene.

9. The method of claim 1 , wherein, in the first and second steps, oxidative and reductive etching processes are carried out on both surfaces of multilayer graphene.

10. The method of claim 1 , further comprising:

a step of clustering epoxy functional groups or hydroxyl functional groups formed by oxidation on a graphene surface through an annealing process between the first step and the second step.

11. The method of claim 1 , wherein processes of the first step to the third step are carried out after preliminarily attaching the multilayer graphene on a perforated support.

12. The method of claim 1 , further comprising:

a step of removing oxidation-related chemical functional groups remaining on a graphene surface after finally obtaining a nanoporous multilayer graphene membrane.

13. The method of claim 1 , wherein, in the second step, multilayer graphene is heated by microwaves for reductive etching.

14. The method of claim 13 , wherein an average particle size of the multilayer graphene to be heated by microwaves is 0.5 mm or more when the multilayer graphene has a polycrystalline form.

15. The method of claim 1 , wherein, in the second step, laser irradiation is applied to the surface of multilayer graphene for reductive etching.

16. The method of claim 15 , wherein the laser used for irradiation is pulsed laser.