Nano-casting synthesis of nanoporous carbons from biomass tar as sustainable electrode material for high-performance supercapacitor

Abstract

Asphalt and coal tar, etc., as byproducts from fossil refinery featured with polycyclic carbon, are hot precursors for diverse advanced carbon functional materials. Herein, their bio-counterpart, namely biomass tar (BT), a notorious byproduct from biomass pyrolysis/gasification was successfully converted into O, N-co-doped carbon with interconnected porous structure via nano-casting with ZnO nano-rods. The optimal product obtained at 700 °C with mass ratio of 1:2:2 for biomass tar, nano-ZnO and KOH delivered specific capacitance up to 295F/g and 204F/g at current densities of 1 A/g and 20 A/g, respectively, and the specific capacitance was maintained at 86.3 % after 10,000 cycles of charging-discharging at 20 A/g. In the two-electrode system, a single electrode made of BTC-1Z-2K-700 still has a specific capacitance of 295.2 F/g at 0.2 A/g. Symmetrical supercapacitor device assembled with 1 M Na2SO4 as the electrolyte achieves the energy density of 27.19 Wh/kg at the power density of 640 W/kg. The impressive charge storage capacity and rating performance were attributed to its hierarchical porosity, large interface and low electric resistance. This work provides a novel out path for biomass tar valorization, as well as a sustainable and cost-effective candidate for electrode material for high-performance supercapacitor.