Three-dimensional honeycomb-like hierarchically structured carbon for high-performance supercapacitors derived from high-ash-content sewage sludge

Abstract

In this work, we demonstrate for the first time that three-dimensional honeycomb-like hierarchically structured carbon (HSC) can be prepared by using high-ash-content sewage sludge as a carbon precursor. The fly-silicon process plays a crucial role in the formation of honeycomb-like hierarchical structures. The as-resulted HSC exhibits novel honeycomb-like frameworks, high specific surface area (2839 m² g⁻¹), large pore volume (2.65 cm³ g⁻¹), interconnected hierarchical porosity, and excellent electrochemical performance. The high specific capacitance of 379 F g⁻¹ as well as excellent rate capability and outstanding cycling stability (over 90% capacitance retention after 20 000 cycles even at a high current density of 20 A g⁻¹), makes it suitable for high-performance supercapacitor electrode materials. The assembled HSC//HSC symmetric supercapacitor presents enhanced supercapacitive behavior with a high energy density of 30.5 W h kg⁻¹ in aqueous solution. This strategy provides an effective method to develop high-performance electrode materials derived from other high-ash-content biomass wastes for supercapacitors.