KOH assistance with graphene oxide induced synthesis of porous carbon nanosheets for supercapacitor and zinc ion hybrid capacitor

Abstract

Porous carbon nanosheets have emerged as promising candidates for electrode materials in energy storage systems. Herein, graphene oxide induced strategy was developed to prepare porous carbon nanosheets derived from starch with potassium hydroxide (KOH) assistance. The surface of graphene oxide contains abundant carboxyl groups that form hydrogen bonds with starch, tightly binding them together. Upon dissolving in water, KOH releases a significant amount of heat, promoting starch gelatinization on the surface of oxidized graphene. The layered structure of oxidized graphene induces the formation of porous carbon nanosheets with KOH assistance during the carbonization process. The obtained samples consist of numerous of carbon nanosheets that create a three-dimensional (3D) interconnected macroporous network. Benefiting from the high specific surface area, interconnected porous carbon nanosheets structure, and rich oxygen functional groups, the GPC-700 electrode demonstrates an impressive specific capacitance of 431.8 F g−1 at 0.5 A g−1, coupled with a good rate characteristic (293.3 F g−1 at 20 A g−1) and excellent electrochemical durability (10,000 cycles, 95.5 % retention). More importantly, the fabricated Zn//ZnSO4//GPC-700 zinc ion hybrid capacitor exhibits a high energy density of 123.1 Wh kg−1 and superior cycle life. This work provides new ideas and feasible methods for preparing biomass-based porous carbon nanosheets as electrode materials for energy storage devices.