Fabrication of Supercapacitors using Carbon Microspheres Synthesized from Resorcinol-Formaldehyde Resin

A versatile procedure is investigated for the synthesis of carbon microspheres from resorcinol-formaldehyde (RF) resin and various catalysts, such as boric acid (H3BO3), hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), ammonia (NH3 center dot H2O), and sodium hydroxide (NaOH). Among the catalysts investigated in this work, ammonia is the most efficient for precisely controlling the size and morphology of the RF-resin microspheres. Furthermore, the carbon microspheres (CRF-6) derived from the RF-6 resin microspheres that were synthesized by using the ammonia catalyst result in a high surface area: S-BET of 473 m(2)g(-1) and V-total of 0.287 cm(3)g(-1). As a supercapacitor electrode material, they present a low resistance value (R) of 0.5 Omega in 6 mol L-1 KOH electrolyte. The maximum specific capacitance of the electrode measured by using cyclic voltammetry reaches 175.9 Fg(-1) at a scan rate of 1 mVs(-1) and 139.5 Fg(-1) at a current density of 1 Ag-1 from galvanostatic charge-discharge measurements. The specific capacitance only decays 5.6% after 500 cycles, which indicates that the sample possesses excellent cycle durability. The present study shows that the carbon microspheres synthesized using RF resin are electrically conductive materials with reduced mass-transport resistance and improved supercapacitor performance reliability.