Superhydrophilicity and ultrahigh-rate supercapacitor performances enabled by mesoporous carbon doped with conjugated hydroxyl

Abstract

The use of carbon-based nanostructures as electrode for supercapacitor usually suffers from poor rate capability mainly due to their inherent hydrophobic character that leads to large diffusion resistance for aqueous electrolyte. It is envisaged that the construction of hydrophilic carbon by introducing electrochemically active groups can increase the capacitance and rate capability of a supercapacitor. Herein, by a simple approach of adopting CaCO3 as template, we fabricated a mesoporous carbon with worm-like mesoporosity, open-access morphology, and excellent hydrophilicity. The carbon material is enriched with electrochemically active oxygen groups (8.8 atom%) in the forms of conjugated carbonyl (-C=O) and hydroxyl (-C-OH). The hydroxyl on the surface could react with alkaline electrolyte forming hydroxy negative ions that enhance the surface polarity and hydrophilicity of carbon. Due to synergistic effect of these favorable factors, the derived mesoporous carbon (CaCs) materials demonstrate superior supercapacitor performances including large capacitance of 305 F/g, ultrahigh rate capability of 75.7% at current density of 1.0 to 100 A/g, large specific energy of 27.1 Wh/kg@1000 W/kg (maintaining 19.1 Wh/kg@18,800 W/kg), displaying great potential as electrode in the fields of electrochemical energy storage.