Carbon Surface Modifications
Electrode material typically is made from treated carbons. The number of functional groups residing on the treated carbon is reduced before the treated carbon is integrated into an electrochemical double layer capacitor. In one implementation, the number of functional groups on a given treated carbon is reduced by over 80%.
1 . A method of making treated carbon, the method comprising:
providing a carbon sample;
flowing a reactant gas over the carbon sample;
heating the carbon sample to at least 300° C.; and
targeting the carbon sample with microwave energy at or about ambient pressure or greater.
2 . The method of claim 1 , wherein the reactant gas comprises hydrogen and nitrogen.
3 . The method of claim 2 , wherein the percentage of hydrogen in the reactant gas is between 1% and 20%.
4 . The method of claim 3 , wherein the percentage of hydrogen in the reactant gas is between 3% and 10%.
5 . The method of claim 4 , wherein the percentage of hydrogen in the reactant gas is between 4% and 8%.
6 . The method of claim 2 , wherein the reactant gas further comprises at least one of the group consisting of methane, ammonia, and syngas.
7 . The method of claim 1 , wherein the reactant gas is provided in a continuous flow stream.
8 . The method of claim 1 , wherein the carbon sample is heated to at least 500° C.
9 . The method of claim 8 , wherein the carbon sample is heated to at least 600° C.
10 . The method of claim 1 , wherein the exposing step lasts for less than 30 minutes.
11 . The method of claim 1 , wherein the exposing step lasts for less than about 5 minutes.
12 . The method of claim 1 , wherein the microwave energy is supplied at a frequency of at least 0.3 GHz, with frequencies centered around about 0.915, 2.45, 5.80 or 22.0 GHz.
13 . The method of claim 1 , where the carbon sample is degassed before the flowing, heating and exposing steps.
14 . The method of claim 13 , wherein the degassing step is performed at between about 80 and 200° C.
15 . The method of claim 14 , wherein the degassing step is performed at between about 100 and 150° C.
16 . The method of claim 13 , where the degassing step is performed in a nitrogen gas environment.
17 . The method of claim 13 , where the degassing step is performed at about 28 inches Hg vacuum.
18 . The method of claim 1 , further comprising flowing non-reactive gas along with the reactant gas over the carbon sample.
19 . A system for modifying carbon material at or about ambient pressure or greater, comprising:
a reaction chamber;
a heating element configured to heat the chamber to more than 300° C.;
a gas inlet configured to receive a gas flow and direct the gas flow to the chamber; and
a microwave source.
20 . An electrochemical double layer capacitor comprising:
a first electrode;
a second electrode;
a porous separator disposed between the first and second electrode;
a container; and
an electrolyte,
wherein the first and second electrode comprise treated carbon formed by providing a carbon sample; flowing a reactant gas over the carbon sample; heating the carbon sample to at least 300° C.; and targeting the carbon sample with microwave energy at or about ambient pressure or greater.
21 . A treated carbon with reduced oxygen-containing functional groups formed by:
providing a carbon sample;
flowing a reactant gas over the sample;
heating the carbon sample to at least 300° C.; and
targeting the carbon sample with microwave energy at or about ambient pressure or greater.
22 . The treated carbon of claim 21 , wherein the functional groups are reduced by more than 50%.
23 . The treated carbon of claim 22 , wherein the functional groups are reduced by more than 80%.
24 . A method of making treated carbon, the method comprising:
providing a carbon sample;
flowing a reactant gas comprising N 2 and 5-10% H 2 over the carbon sample;
heating the carbon sample to at least about 600° C.; and
targeting the carbon sample with microwave energy at or about ambient pressure or greater.
25 . The method of claim 24 , where the carbon sample is degassed in an N 2 environment at 100-150° C. before the flowing, heating and exposing steps.