Graphene networks and methods for synthesis and use of the same
View Patent ↗The present development is a novel graphene foam with highly enriched incommensurately-stacked layers. The graphene foam is intended to be applied as active electrodes in rechargeable batteries. A 93% incommensurate graphene foam demonstrated a reversible specific capacity of 1540 mAh g -1 with a 75% coulombic efficiency, and an 86% incommensurate sample achieves above 99% coulombic efficiency exhibiting 930 mAh g -1 specific capacity.
1 . A method for preparing a multilayer graphene network comprising:
(a) providing a reaction chamber;
(b) adding nickel metal particles having non-uniform particle sizes of from about 1 µm to about 200 µm to the reaction chamber, wherein the nickel particles are selected so as to produce a curved catalyst template;
(c) pressurizing the reaction chamber to a pressure of from about 40 mTorr to about 150 mTorr;
(d) heating the pressurized reaction chamber according to a predetermined program to form the curved metal catalyst template from the metal particles;
(e) feeding a hydrocarbon source into the reaction chamber;
(f) allowing the hydrocarbon source to deposit on the metal catalyst template to form a graphene-metal template, wherein the graphene forms as a plurality of graphene sheets arranged in a three-dimensional (3D) network having an incommensurate stacking structure;
(g) allowing the reaction chamber and the graphene-metal template to cool to a predetermined temperature while maintaining a pressure of from about 40 mTorr to about 150 mTorr;
(h) removing the metal from the graphene-metal template to obtain a graphene network with incommensurate stacking; and
(i) collecting the graphene network,
wherein a carrier gas selected from Ar, He, H 2 , N 2 , and mixtures thereof flows through the reaction chamber while the metal template is formed or while the graphene-metal template is formed or while the metal template and the graphene-metal template are formed.
2 . The method of claim 1 wherein the metal particles are non-uniform nickel particles having a particle size of from about 1 µm to about 40 µm.
3 . The method of claim 1 wherein the step of forming the metal catalyst template is performed at a temperature of from about 1000° C. to about 1050° C.
4 . The method of claim 1 wherein the hydrocarbon source is applied at a rate of from about 1 sccm to about 20 sccm.
5 . The method of claim 4 wherein the hydrocarbon source is CH 4 .
6 . The method of claim 1 wherein the hydrocarbon source is applied at a temperature of from about 1025° C. to about 1050° C.
7 . The method of claim 1 wherein the metal is removed from the graphene-metal template by etching.
8 . A method for preparing a multilayer graphene network comprising:
(a) providing a reaction chamber;
(b) adding metal particles having non-uniform particle sizes of from about 1 µm to about 200 µm to the reaction chamber;
(c) allowing a carrier gas to flow through the reaction chamber at a rate of from about 10 sccm to about 1000 sccm and make contact with the metal particles;
(d) pressurizing the reaction chamber to a pressure of from about 45 mTorr to about 55 mTorr while the carrier gas is flowing through the chamber;
(e) heating the pressurized reaction chamber a temperature of from about 1025° C. to about 1050° C. to form a curved metal catalyst template from the metal particles;
(f) feeding a hydrocarbon source into the pressurized reaction chamber while continuing the carrier gas flow;
(g) allowing the hydrocarbon source to deposit on the metal catalyst template to form a graphene-metal template, wherein the graphene forms as a plurality of graphene sheets arranged in a three-dimensional (3D) network having an incommensurate stacking structure;
(h) allowing the reaction chamber and the graphene-metal template to cool to a final temperature of about 25° C. at a cooling rate of 100° C./min while continuing the carrier gas flow and while holding the reaction chamber pressure at 45 mTorr to 55 mTorr;
(i) removing the metal from the graphene-metal template to obtain a graphene network with incommensurate stacking;
(j) washing the graphene network;
(k) drying the graphene network by covering the graphene network with high purity liquid CO 2 at a pressure of 800 psi (±5%) and heating the reaction chamber to about 40° C. while increasing the pressure to about 1200 psi, and then allowing the chamber to cool to about 25° C. and allowing the pressure to drop to about 400 psi; and
(l) collecting the graphene network.
9 . The method of claim 8 wherein the metal particles are nickel particles have a particle size of from about 1 µm to about 40 µm.
10 . The method of claim 9 wherein the reaction chamber with the nickel particles is heated to 600° C. at a 50° C./min heating rate, and then the chamber is heated to 1000° C. at a 70° C./min heating rate and held at 1000° C. for 10 minutes, and then the chamber is heated at a rate of 70° C./min until the chamber reaches a temperature of from about 1025° C. to about 1050° C.
11 . The method of claim 8 wherein the hydrocarbon source is CH 4 .
12 . The method of claim 8 wherein the carrier gas is a mixture of Ar/H 2 at a ratio of 3:2 and wherein the carrier gas has a flow rate of from about 20 sccm to about 150 sccm.
13 . The method of claim 8 wherein the etching is accomplished by using hydrochloric acid or nitric acid or ferric chloride or a combination thereof.
14 . The method of claim 8 wherein the graphene network is washed with de-ionized water and then with pure ethylene alcohol and then the graphene network is placed in a chamber and covered with ethylene alcohol and cooled to slightly below 20° C.