Impact of pore size characteristics on the electrosorption capacity of carbon xerogel electrodes for capacitive deionization

Conductive, monolithic carbon xerogel electrodes have been synthesized using a flexible carbon support and a resorcinol-formaldehyde (RF) polycondensation reaction with RF precursor weight percentages of 37, 40, 45, and 50 to tailor pore size distributions for electrosorption. Increased RF weight percentages produced carbon electrodes with pore volumes greater than 0.4 cm³/g. External pore size examined by SEM was shown to decrease with increasing RF weight percent from >300 nm to <50 nm for 37 wt% RF and 50 wt% RF, respectively. Carbon electrodes were used in a capacitive deionization cell demonstrating electrosorption capacities between 2.8-3.5 mg NaCl/g carbon using an applied potential of 1.2 V. Surface utilization of the carbon for electrosorption was found to decrease with increasing RF wt% corresponding with decreasing of the external pore size from macroporous to mesoporous. A mixture of macroporous and mesoporous content is preferred for fast time scale applications such as capacitive deionization.