Pore structure and the properties of electric double layer capacitor electrode of bamboo-derived activated carbon prepared by superheated steam

Bamboo-derived activated carbon prepared by superheated steam (BAC) exhibited performance for utilization as an electric double layer capacitor (EDLC) electrode. Pore structure and EDLC performances were investigated by comparison with phenol resin-derived activated carbon (MSP-20), which is commercially available and often used for the purpose. The nitrogen adsorption isotherm showed that BAC had a large BET-specific surface area of 1268g/m(2) with a developed pore structure, especially of the mesopore, in comparison with MSP-20. It is considered that inherent ash in bamboo promoted activation, in addition to physical activation by superheated steam. Capacitance per electrode volume (C-V) was 52F/cm(3) with BAC. Because the density of BAC is high (0.78g/cm(3)) compared with that of MSP-20 (0.58g/cm(3)), sufficient C-V for usage was obtained, although the capacitance per electrode mass (C-M) at 5mA/cm(2) itself of BAC (67F/g) was lower than that of MSP-20 (126F/g). With IR drop, the resistance value of BAC (9.7 ) was lower than that of MSP-20 (10.5 ). Especially, the diffusion resistance of BAC disclosed to be smaller than that of MSP-20. These results indicated that BAC produced by steam activation is a promising material with a pore structure suitable for ion transfer in EDLC.