Preparation Of Ordered Porous Carbons And Their Electrochemical Capacitive Performance And CO₂ Adsorption Performance

Hard-templating method is considered as a unique and versatile approach for preparation of the porous carbons with controlled pore texture. Among the templates used, the zeolites have attracted particular interests due to their unique pore structure. In this dissertation, series of ordered porous carbons were prepared by PFA-impregnation method (one-step method) and impregnation-chemical vapor deposition method (two-step method) using zeolite NaY or HY zeolites as templates. The effect of effective pore size (due to different cations of zeolite Y) on the pore structure of the resulted carbons, and their electrochemical capacitive performances and CO2 absorption behavior are investigated for the first time.The pore structure and morphology of the carbon materials were systemically analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy, transmission electron microscopy and N2 adsorption measurements. The carbons prepared by the two-step method are proved to be typical microporous carbon materials and had a large BET surface area and narrow pore size distribution. The highest BET surface and pore volume of the carbon materials can reach 2207 m2/g and 1.4 cm3/g, respectively. The replication of zeolite regularity strongly depends on the effective pore size of zeolites for the carbon materials prepared by the two-step method. The larger the effective channel size is, the easier the acetonitrile deposits into the channels of the zeolites during the CVD process. Therefore, the carbon templated by zeolite HY with larger effective pore size well replicates the structure of zeolite, and have a higher pore regularity and surface area. XPS test confirms that the carbon materials possess abundant nitrogen-containing groups due to the CVD of acetonitrile. The N1s signal indicates that the main forms of nitrogen were pyridinic and quaternary groups.The electrochemical performances of the carbon materials were investigated in both KOH and H2SO4 electrolyte. Electrochemical tests in KOH electrolyte demonstrate that the carbons prepared by the two-step method present a higher capacitance than that prepared by the one-step method due to their evident pseudo-capacitance derived from the nitrogen-containing groups. Besides, more obvious pseudo-capacitance are observed in H2SO4 electrolyte than in KOH electrolyte. A high gravimetric capacitance of up to 312 F/g and a high energy density of 15.6 Wh/kg are obtained for the HY8 carbon in H2SO4 electrolyte. The capacitance retention ratio increases with the increasing of mesoporosity and preparation temperature. In addition, the HY8 carbon also shows an acceptable cycle life with relatively high capacitance at 1.2 V after 4000 cycles, about 87% of initial discharge capacitance.CO2 absorption tests demonstrate that carbon materials prepared by two-step method show preferable CO2 adsorption performance due to their more nitrogen-containing groups. The CO2 adsorbed capacity is determined by the amount of pyridinic functional groups on the carbon surface. The NaY5 carbon prepared at 500℃exhibits the highest CO2 adsorbed capacity per surface area (135μg/m2).