Biomass derived hierarchical porous carbon for supercapacitor application and dilute stream CO2 capture

High surface area porous carbons derived from sustainable biomass wastes are excellent functional materials for energy storage and gas sorption applications. Tasmanian Blue Gum (TBG) tree bark is selected as the raw material for preparing activated porous carbon (AC), using a simple KOH activation and carbonization method. The as-prepared AC-TBG sample possesses a hierarchically connected mesoporous structure having a surface area of 971 m2 g−1 with an average pore size of 2.2 nm. AC-TBG exhibits high electrochemical storage capacity as fabricated symmetric supercapacitor, with excellent specific capacitances of 212 F g−1 at 1 A g−1 current density retaining 90% of its capacitance after 5000 cycles. An outstanding maximum power density of 4.9 kW kg−1 was obtained for the EDLC in 1 M KOH at a maximum energy density of 18.84 Wh kg−1, which is among the highest values reported in this class of materials. Furthermore, exploiting the multiscale porosity and oxygen/hydroxyl functionalities on the surface, AC-TBG was deployed for CO2 capture from concentrated source as well as dilute 4% CO2 simulated flue stream. AC-TBG showed an excellent uptake of 4.5 mmol/g of CO2 at 1 bar and 0 °C for pure CO2 and a working capacity of 1.6 mmol/g at 40 °C in 4% CO2. This work provides a simple, and feasible strategy for converting sustainable waste biomass to value-added activated carbon with potential applications in high-performance energy storage and greenhouse gas capture.