Enhanced salt-adsorption capacity of ambient pressure dried carbon aerogel activated by CO2 for capacitive deionization application

Carbon aerogels (CAs) were prepared by polycondensation of resorcinol and formaldehyde using ambient drying technique and were further activated by CO2. These were investigated for capacitive deionization (CDI) application. The gel parameters were optimized to obtain mesoporous CA with pore size distribution in 8-10 nm. The CA was further subjected to CO2 activation at 950 degrees C for different time durations and its effect on surface properties was studied. The surface area of the activated CA increased from 698 to 2057 m(2)/g with corresponding increase in mesopore area from 289 to 644 m(2)/g. The pore volume also increased from 0.79 to 1.72 cm(3)/g. Cyclic voltammetry was performed on the test electrodes and specific capacitance values of 108 F/g was measured at scan rate of 10 mV/s in 1 M NaCl. Electrodes of size 200 x 200 mm were synthesized with an active material loading of ~15 mg/cm(2) and their CDI performance was evaluated in batch mode experiment. Salt-adsorption capacity as high as 8.4 mg/g for CO2 activated CA was achieved for the starting electrolyte concentration of 500 mg/L, whereas the adsorption capacity for the CA without activation was 4.1 mg/g. The results suggest that CO2 activated CA is a good choice for CDI application.