Combustion conversion of wood to N, O co-doped 2D carbon nanosheets for zinc-ion hybrid supercapacitors

Low-cost, high-performance, and long-life cathode materials are highly desired for zinc ion hybrid supercapacitors (ZHSs). Here, an N, O co-doped two-dimensional (2D) carbon nanosheet material is successfully fabricated via a one-step combustion conversion of wood for the excellent usage as the cathode material in zinc-ion hybrid supercapacitors. This novel combustion conversion synthesis with Zn(NO3)2·6H2O as oxidizer and urea as fuel can easily achieve the carbonization, pore-forming, and heteroatom doping within a one-step process. More interestingly, the resulting N, O co-doped porous carbon owns relatively uniform 2D sheet structure and very high specific surface area (1248 m2 g−1), which can not only provide short electric/ionic transfer path plus optimized wettability and conductivity for high power output, but also offer abundant interfacial active sites as well as improved ion adsorption capacity for high energy storage. Benefiting from these advantages, the ZHS based on this N, O co-doped 2D carbon nanosheets exhibits a superior specific capacity of 111.0 mAh g−1 at 0.1 A g−1, high rate capability of 57.6% capacity retention at a 30-fold higher current, and attractive energy density of 109.5 Wh kg−1 at 225 W kg−1. More gratifyingly, it displays ultralong cycling life with 92.7% capacity reservation after 50,000 charge and discharge cycles. Moreover, a quasi-solid ZHS with N, O co-doped 2D carbon nanosheets coated on the carbon cloth as the cathode also displays satisfactory specific capacity (34.6 mAh g−1), impressive energy density (27.7 Wh kg−1), and nice flexibility.