Apple residues derived porous carbon nanosheets synthesized with FeCl3 assisted hydrothermal carbonization for supercapacitors with high rate performance

Biomass carbon materials with high rate capacity have great potential to boost supercapacitors with cost effective, fast charging–discharging performance and high safety requirements, yet currently suffers from a lack of targeted preparation methods. Here we propose a facile FeCl3 assisted hydrothermal carbonization strategy to prepare ultra-high rate biomass carbon from apple residues (ARs). In the preparation process, ARs were first hydrothermally carbonized into a porous precursor which embedded by Fe species, and then synchronously graphitized and activated to form biocarbon with a large special surface area (2159.3 m2 g−1) and high degree of graphitization. The material exhibited a considerable specific capacitance of 297.5 F g−1 at 0.5 A g−1 and outstanding capacitance retention of 85.7% at 10 A g−1 in 6 M KOH, and moreover, achieved an energy density of 16.2 Wh kg−1 with the power density of 350.3 W kg−1. After 8000 cycles, an initial capacitance of 95.2% was maintained. Our findings provide a new idea for boosting the rate capacity of carbon-based electrode materials.