Hierarchically porous carbon nanosheets derived from Bougainvillea petals with "pores-on-surface" structure for ultrahigh performance Zinc-ions hybrid capacitors

Due to the outstanding electrochemical performance, high safety coefficient, controllable reaction system and low production cost, Zinc-ion hybrid capacitors (ZIHCs) is considered as a new generation of promising energy storage technology, which even seem as a suitable choice for Medical application. However, to produce ideal carbon-base cathode material with low cost and high electrochemical performance still face challenge. Here, we report a ZIHCs' cathode based on Bougainvillea petal-derived porous carbon nanosheets (Carbonized Bougainvillea activated at 850 degrees C, CB-3-850). CB-3-850 derived from Bougainvillea petals exhibit extremely an ultrahigh discharge capacity of 239.1 mAh g(-1) at 0.5 A g(-1) (from 0 V to 1.8 V) and an excellent electrochemical stability at 20 A g(-1) (90 %, 10,000 cycles). In addition, ultrahigh energy density (213.4 Wh kg(-1)) and high power density (14.8 kW kg(-1)) are realized in CB-3-850. Special "pores-on-surface" structure and ultrathin nanosheet-like morphology of CB-3-850 not only provide a high specific surface area that for more Zn2+ and SO42+ absorbed on its surface but also enable ions across the one nanosheet directly to reach other carbon-sheets units, which realize a fast kinetic process of ions storage and higher capacity. The excellent performance of the Zinc-ion capacitor can be also attributed to N and O doping that strongly interacted with Zn2+ during the charge/discharge process. Finally, natural Bougainvillea petal just contains simple non-metal elements like C, N and O, exhibit high biocompatibility.