Efficient Activation Engineering from the Inside Out toward Hierarchically Porous Carbon Framework as Electrode Materials for Supercapacitors

Over the past decades, the KOH-involved activation has been established to obtain porous carbons for supercapacitors. However, from the perspective of economic efficiency and practicability, it is significant yet urgent to explore a simple way to minimize the use of corrosive KOH for efficient fabrication of supercapacitive carbons without sacrificing electrochemical properties. Herein, we first develop a simple yet efficient activation strategy from the inside out, where the KOH activator (∼40 wt %) is uniformly located in poly(vinyl alcohol) (PVA) hydrogel as the precursor, to fabricate a three-dimensional hierarchically porous carbon framework (denoted as PC-K). Compared with the porous carbon obtained by physically mixing KOH and PVA, the PC-K with hydrophilic surface is endowed with an even larger specific surface area, a higher pore volume, and higher-content mesopores, ensuring abundant active sites and rapid ion/electron transport. Such attractive merits result in encouraging electrochemical capacitances of the PC-K electrode with a loading of 5 mg cm–2 both in symmetric devices and three-electrode systems with 6 M KOH and 1 M H2SO4 as aqueous electrolytes, which is particularly better than other carbons synthesized with more KOH addition. More significantly, the contribution here provides a guiding methodology for the feasible commercial synthesis of advanced porous carbons toward next-generation supercapacitors.