Rapid conversion of biomass to hierarchical porous carbons via one-step microwave carbonization/activation for long cycle-stable supercapacitor and zinc-ion capacitor

Biomass derived carbons as electrode materials for supercapacitors have drawn great attention owing to their low cost, high specific areas and abundant surface functional groups, but most of their preparation processes are time-consuming and power-wasting. In this work, we report a rapid and energy-saving strategy for preparing hierarchical porous carbons derived from loofah sponges for supercapacitors via one-step microwave carbonization/activation. Utilizing KOH as the microwave absorption medium and activator, the microwave carbonization/activation process can be completed within 6-10 min. The resulting loofah sponges derived porous carbons demonstrate a high specific capacitance of 294 F g(-1) at 0.5 A g(-1) and an outstanding retention rate of 74.8 % at 20 A g(-1) in three-electrode setup for supercapacitor. The fabricated zinc-ion capacitor based on the as-prepared carbon materials displays a comparable energy density of 62.3 Wh center dot kg(-1) at the power density of 160 W kg(-1). Notably, a remarkable long-term cyclic stability by retaining of 93.6 % of its initial capacitance is acquired after 30,000 cycles. Our research not only fabricates sustainable electrode materials for supercapacitors and zinc-ion capacitors but also provides a fast and energy efficient route for producing biomass derived carbon materials with high capacitive performances for commercial applications.