(A) study on fractal characteristics and kinetics of double-layer charging/discharging of porous carbon electrodes

Abstract

The present work involves an investigation of fractal characteristics and kinetics of double-layer charging/discharging of porous carbon electrodes. Chapter III involves the effect of pore structures on fractal characteristics of meso/macroporous carbons using the $N_2$ gas adsorption method. For this purpose, the pore structures of the carbon specimens were controlled by varying the molar silica/furfuryl alcohol $(SiO_2/C_5H_6O_2)$ ratio and the pH of initial solution mixture. From the analysis of pore size distribution (PSD) curves constructed from the $N_2$ gas adsorption isotherms, it was found that the carbon specimens are composed of meso/macropores with different average pore diameters $d_{ave}$ and standard deviations of the PSD. The surface fractal dimensions $d_{F,surf}$ of the carbon specimens were determined from the linear relationship between ln $V/V_{mono}$ and lnln $(p^o/p)$ based upon the multilayer gas adsorption theory. The carbon specimen with the larger values of $\sigma$ and macroporosity gave the lower value of $d_{F,surf}$ than that specimen with the smaller values of those. It is confirmed that as the silica-templated pores being comprised by the carbon specimen agglomerate, the irregularity of that pore surface decreases, thus causing the decrease in $d_{F,surf}$. In chapter IV, the geometric and structural properties of pore surfaces of microporous carbon specimens were investigated using high resolution transmission electron microscopy (HRTEM) and $N_2$ gas adsorption method based upon the fractal theory. The carbon powder specimens with various pore structures were prepared by reactivation of commercially as-activated carbon powder at 1273 K in an atmosphere of a $CO_2/CO$ gas mixture for different activation times. The values of $d_{F,surf}$ were evaluated from the image analysis of the HRTEM images using perimeter-area method. In addition, the pore fractal dimensions $d_{F,pore}$ were determined from the analyses of $N_2$ g...