Efficient Charge Storage in Hierarchically Porous Carbon Foams for Supercapacitor Applications

Abstract

Compositionally controlled hierarchically porous monolithic carbon foams synthesized via silica hard templating technique are used as electrodes for symmetrical supercapacitors. Fifteen carbon monoliths are prepared by controlling net quantity of modified silica particles per gram of oily phase, the quantity of oil phase (vol%), and the resin concentration (wt%), exhibiting Brunauer–Emmett–Teller (BET) surface area ranging from 700 to 900 m2 g−1 are chosen to study the profound effect of the influence of pore size and its distribution on their capacitive performance in an aqueous electrolyte using cyclic voltammetry (CV), galvanostatic charge/discharge, and impedance spectroscopy techniques. The typical rectangular shape CV profile illustrates the capacitive properties of these carbon foams. It is found that mesopores facilitate the diffusion of electrolyte ions (aqueous potassium hydroxide (KOH)) deep into the micropores by providing transmission line‐like pathways. In contrast, micropores enrich the density of charge separation that determines the magnitude of charge storage across electric double layers leading to high capacitance, 122 F g−1 for hierarchically porous carbon foam, namely 8/70C60. The coin type (form factor CR2032) symmetrical supercapacitor is fabricated using the best performing carbon (8/70C60), yielding high capacitance retention of 98.2% for 20 000 cycles and achieving a good power density of 76.8 kW kg−1.