2D porous carbon nanosheets derived from turnip: Preparation, characterization and its electrochemical performance

Biomass-based porous carbon materials have appeal due to their low cost, abundance and sustainability. In this report, a novel kind of heteroatom (N, S) co-doped 2D porous activated carbon using turnip as biomass has been prepared with subsequent non-toxic dual activators. At optimized activation temperature, the activated carbon from turnip-derived using KCl/NaCl (ACTKNa) as activators shows excellent surface area of 1938 m2·g−1 with micro-mesopores distributions. Importantly, ACTKNa as electrode materials for supercapacitors exhibits a superb capacitance value of 570 F·g−1 (0.5 A·g−1) and retains high stability. Interestingly, a symmetric ACTKNa//ACTKNa device can work in the potential window (0–1.5 V) under neutral Na2SO4 solution. Among them, the symmetric device delivers specific energy value 47.5 Wh·kg−1 at specific power of 372 W·kg−1 with outstanding rate capability of 86 % after 20,000 cycles. This work opens the way to enhance the specific energy value by increasing the potential window using neutral electrolyte.