TDA has recently invented methods for making porous carbons for use as electrodes in liquid-phase electrochemical applications such as ultracapacitors and capacitive deionization. To perform well in liquid-phase applications, carbons need to have pores large enough to allow the liquid to penetrate the interior of the carbon, yet small enough to maintain high surface areas. Unfortunately, high surface area porous carbons made from woods and coal typically have a high proportion of micropores which are so small that they cannot be easily reached by the liquid, and only a fraction of the surface of the carbon is effectively utilized.
To address this problem TDA has developed methods to produce inexpensive carbons with bi-modal pore size distributions, providing a combination of micropores and mesopores. The larger mesopores create channels to allow the liquid easy access to the high surface area micropores. By controlling the formulation and processing conditions, the pore volumes can be controlled for the micropores and mesopores, the pore diameter of the mesopores can be adjusted from 2-50 nm and the BET surface can tuned from 400 to 2700 m2/g. The table below shows examples of TDA’s porous carbons.
|
Mesopore Size (nm) |
Total Pore Volume (cm3/g) |
Mesopore Volume (cm3/g) |
Total Surface Area (m2/g) |
|
12 |
0.90 |
0.73 |
674 |
|
18 |
1.52 |
1.23 |
920 |
|
28 |
1.11 |
0.95 |
583 |
|
<3 |
0.53 |
0.13 |
965 |
|
<3 |
1.00 |
0.51 |
1814 |
|
<3 |
1.41 |
1.21 |
2475 |
These carbons are very inexpensive because they are made from very low-cost precursors using conventional processing methods. Our basic method was developed over the last eight years using DOE and NSF SBIR funding. We have two issued patents related to this work and three more pending (U.S. Patent 6,297,293, 6,737,445).
This work was supported by the National Science Foundation and the Department of Energy.