Improvement of Mesoporosity on Supercapacitive Performance of Activated Carbons Derived From Coffee Grounds

摘要

Activated carbons with different porosities derived from coffee,which prepared by the potassium hydroxide(KOH) activation method,are used as electrode for supercapacitors.The prepared materials indicated a well-designed porous structure that provides countless adsorption sites,leading to high supercapacitor performance.Mesopores allow rapid diffusion of electrolyte ions,while micropores usually provide abundant adsorption sites for ions.Therefore,appropriate control over pore-size distributions is a key factor for good electrochemical performance.The porosity and surface structure of activated coffee grounds(ACGs) are highly dependent on both the activation temperature and KOH/carbonized materials weight ratio.The ACGs were characterized using N2 adsorption at 77 K.The specific surface area increased from 1.75 to 3065 m/g.Cyclic voltammetry and galvanostatic charge-discharge tests were employed in the evaluation of the electrochemical behavior of each sample.The ACG materials have a high specific capacitance of 127.8 F/g and cycle stability after 2500 cycles.