Correlation of Double‐Layer Capacitance with the Pore Structure of Sol‐Gel Derived Carbon Xerogels

Nine different sol-gel derived carbon xerogels were prepared with different pore structures by varying the carbonization temperature (in flowing N2) and activation time (in 5% CO2 in N2). For each of these carbon xerogels, mesopore and micropore size distributions and cumulative surface areas were extracted from a density functional theory analysis. Increasing the carbonization temperature caused a decrease in the number of micropores in the 6 Å range but had little effect on the mesopore size distribution and thus mesopore cumulative surface area. Increasing the CO2 activation time caused an increase in the number of both micro- and mesopores where pores in the 6 Å width range eventually became pores in the 12 Å width range. The electrochemical double-layer capacitance (DLC) of the carbon xerogels was found to correlate well with changes in the pore structure, and it was determined that pores less than about 8 Å in width did not contribute to the DLC.