High-performance activated carbons for supercapacitor: Effects of porous structures, heteroatom doping, and morphology

In this work, we prepare a series of activated carbons (ACs) of different morphologies, porous structures, and oxygen contents from glucose with hydrothermal synthesis (HTS) followed by a one-step (H₂O-steam or KOH) or two-step (H₂O-steam-KOH or KOH-H₂O-steam) activation. The largest surface area of the prepared ACs is more than 3400 m²/g, and the corresponding mesopore volume is 1.21 cm³/g. The fraction of oxygen in the ACs varies in a range of 3.94 to 9.9 at%. The electrochemical performance of the symmetric supercapacitor cells (SCs) made from the as-prepared ACs is characterized in different aqueous electrolytes. The optimum capacitance of the SCs is 421 F/g at 0.5 A/g and 304 F/g at 10 A/g. The oxygen-enriched functional groups have limited contribution to the energy storage for the SCs with neutral electrolyte and profound effects on the increase of the energy storage for the SCs with strong acidic and alkaline electrolytes. The processing routes developed in this work likely open an avenue to tailor the structures and oxygen-enriched functional groups of ACs.