With the increasing attention to energy and environmental issues, the high value-added utilization of biomass and pitch to functional carbon materials has become an important topic in science and technology. In this work, the soft-hard heterostructure porous carbon (NRP-HPC) is prepared by bio-template method, in which biomass and pitch are used as hard carbon and soft carbon precursors, respectively. The prepared NRP-HPC-4 shows high specific surface area (2293 m2 g-1 ), suitable pore size distribution, good conductivity (0.25 Ω cm-1 ), and strong wettability. The synergistic effect of soft carbon and hard carbon ensures the composite material exhibiting excellent electrochemical performance for high mass loading (12.0 mg cm-2 ) aqueous supercapacitor, i.e., high specific capacitance (304.69 F g-1 at 0.1 A g-1 ), high area capacitance (3.67 F cm-2 at 0.1 A g-1 ), high volumetric specific capacitance (202.74 F cm-3 at 0.1 A g-1 ), low open-circuit voltage attenuation rate (21.04 mV h-1 ), good voltage retention (79.12%), and excellent cyclic stability (92.04% capacitance retention and 100% coulombic efficiency after 20 000 cycles). The composite technology of soft carbon and hard carbon not only ensures the prepared porous carbon electrode materials with enhanced electrochemical performance, but also realizes the high value-added coupling utilization of biomass and pitch.
Keywords: aqueous supercapacitors; heterostructure porous carbon materials; high mass-loading electrodes; self-discharge.
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