Ethanol-based synthesis of hierarchically porous carbon using nanocrystalline beta zeolite template for high-rate electrical double layer capacitor

A porous carbon with a mesopore–micropore hierarchy has been synthesized using ethanol as a carbon source within a beta zeolite template, which possesses mesopores and micropores in a hierarchical manner. Various compounds have been evaluated as the carbon source in the carbon synthesis. The result indicates that ethanol vapor is suitable for the hierarchical carbon synthesis, as compared with propylene or acetylene gas. The advantage of ethanol is attributed to the formation of water from the ethanol decomposition during carbonization process. The water seems to assist in delaying the deposition of carbons at the exterior (or the mesopore walls). The resultant carbon after removal of the template is composed of regular micropores of 1-nm diameter and irregular mesopores of 10–30 nm arranged in a hierarchical manner. The hierarchical carbon exhibits a very high electrical double-layer capacitance both at low and high discharge current densities in galvanostatic measurements, as compared to solely microporous or solely mesoporous carbons. The high performance is attributed to facile transport of electrolytes in the hierarchically porous structure.