Abstract
Activated carbons with large mesopore volumes were prepared from waste coffee grounds by chemical activation with ZnCl(2). These carbons exhibited excellent electrochemical double-layer capacitance of up to 368 F g(-1) in 1 M H(2)SO(4). The effect of carbonization temperature and ZnCl(2) ratio on carbon pore development and consequently electrochemical double-layer capacitance in 1 M H(2)SO(4) is discussed. Cyclic voltammetry, electrochemical impedance spectroscopy, and galvanic charge-discharge cycles were used to Study the effects of mesopores oil capacitance at fast charge rates. Activated carbons with greater mesopore content retained higher specific capacitance at fast charge-discharge rates as the mesopores acts as channels or reservoirs for electrolyte transport. An improved model for evaluation of contributions to capacitance from micropore surfaces and mesopore surfaces is proposed. Using this model, the contribution of the mesopores to double-layer capacitance was determined to be 17 mu F cm(-2). The contribution of micropores to capacitance decreased at fast discharge rates and was found to be dependent on the number of mesopores, which influence the transport of ions through the carbon pore network