Effects of Activation with CO2/KOH on the Pore Structures of Coffee Grounds-derived Carbon

In this study, coffee grounds were carbonized through activation with carbon dioxide (hereinafter referred to as CO2) or potassium hydroxide (hereinafter referred to as KOH), and the effects of the respective activation conditions on the pore structures of the carbon obtained were investigated. The specific surface area of the sample carbonized in a CO2 stream at 850˚C was 752 m2/g and that of the sample impregnated with KOH and carbonized was 2549 m2/g when the concentration of KOH was 4.5 M. In the sample carbonized in a CO2 stream, the pores formed were 0.8, 1, and 3.1 nm in size, which were enlarged with the increase in treatment temperature and started to include numerous mesopores. In the sample impregnated with KOH and carbonized, the pores formed were 0.7 nm and 1 to 1.1 nm in size, which were slightly enlarged with the increase in concentration of KOH. It was confirmed that for coffee grounds, activation with KOH had an effect of increasing specific surface area and that CO2 activation had an effect of increasing pore size.