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The effect of physical adsorption on the capacitance of activated carbon electrodes

Tolman, Nathan L., Mukai, Jason M., Wang, Shuqing, Zito, Alessandra, Luo, Tianyi, Liu, Haitao
Carbon 2019 v.150 pp. 334-339
acetone, activated carbon, adsorption, capacitance, carbon electrodes, chloroform, cleaning, electrolytes, ethanol, research and development, solvents, toluene, vapors, volatile organic compounds
This work reports the effect of physisorption of organic compounds on the double layer capacitance of activated carbon electrodes. Exposure of activated carbon electrodes to toluene or chloroform vapor for less than 10 minutes resulted in a capacitance loss of 77% and 84%, respectively. Even adsorbates, such as acetone and ethanol, miscible with the aqueous Li2SO4 electrolyte caused 20–30% losses in capacitance. It was also found that there was an adsorbate size dependence: above a certain threshold, a larger adsorbate could have more than twice the impact on capacitance than a slightly smaller one. The results were consistent with the hypothesis that volatile organic contaminants (VOC) block access of the aqueous electrolyte to the carbon electrode surface. Porous activated carbon is currently the material of choice for supercapacitor electrodes in both research laboratories and commercial supercapacitor applications. These facilities also often house and use many volatile organic solvents either for research and development or simply for cleaning purposes. Because of this, our work has significant implications to the research and development of carbon-based supercapacitors.