Effects of acid treatment on the improvement of specific capacitance and deionization efficiency of porous carbon electrodes

Abstract

We report the effect of acid treatment on porous carbon materials on their double layer capacitance and electrosorption of ions in capacitive deionization systems. The as-received activated carbon cloth (ACC) had the capacitance value of 210F/g and was markedly (∼175%) improved when treated with acid solution. Surface functional groups such as hydroxyl, quinines, lactones and ethers on carbon after modification were increased by 40% and 29% with HNO3 and H2SO4 respectively. In capacitive deionization test of NaCl solution, the ACC treated with HNO3 had more than two times removal efficiency when charged with a 1.5 V current than the untreated one. This is attributed to activation and changes of surface functional groups when charged with a current. © IWA Publishing 2009.