▎ 摘　　要

A facile method for the preparation of oxygen and nitrogen self-doped biochar is developed in this work through the application of one-step chemical activation by using pre-oxidized camellia combing graphene oxide. The extracted results revealed that the obtained biochar had a micropores structure while the nitrogen, oxygen heteroatoms were successfully homogeneously introduced into the carbon frameworks. The specific surface area of the GC-700-4 was about 1343 cm(2) g(-1) with oxygen and nitrogen contents of nearly 15.6 at.% and 2.4 at.%, respectively. When used as an electrode for supercapacitors, the GC-700-4 compound shows the highest area-specific capacitance of 2,206 mF cm(-2) at 1 mA cm(-2), and capacitance retention of about 97.4% after 5000 cycles. Moreover, the proposed symmetric supercapacitor device was fabricated based on GC-700-4, which exhibits a high gravimetric capacitance value of 236.5 F g(-1) and capacity retention of 94.2% after the enforcement of 10,000 cycles at 20 A g(-1), as well as an excellent rate capability. These results confirm that graphene wrapped in biochar can change its morphology, and improve its conductivity and electrochemical performance, while graphene wrapped on the surface of biochar is only beneficial to improve the cycle stability of capacitors.