Novel defluorination assisted physical activation of fluorinated biochar for CO2 adsorption and supercapacitors.

The low-temperature CO2 activation of biochar, assisted by fluorination-defluorination reactions, is reported for the first time. Coconut shell-based biochar was fluorinated at room temperature for 15, 30, 60 min and subsequently activated with CO2 gas to produce activated carbon. The resulting activated carbon had 2.06 times larger specific surface area than the activated carbon obtained from pristine biochar under the same activation conditions. Moreover, the fluorination pretreatment promoted carbon gasification and pore development under CO2 at lower treatment temperatures than those required for pristine biochar. The defluorination-assisted CO2 activation mechanisms are proposed based on analytical results and the reaction mechanism between CO2 gas and fluorine radicals. Moreover, the applicability of the resulting activated carbon in CO2 adsorption and supercapacitors was evaluated. The performance of the activated carbon sample in these applications was affected by its distinctive pore structure. This study provides a novel method for the physical activation of carbon materials.