Functionalized Nanoporous Biocarbon with High Specific Surface Area Derived from Waste Hardwood Chips for CO₂ Capture and Supercapacitors

Waste biomass has aroused increasing interest in the production of low-cost materials for CO₂ adsorption and supercapacitors. One of the primary facets in this regard is to develop nanoporous carbons with controlled porosity and high surface area. Herein, waste wood chips are used to synthesize nanoporous biocarbons via a solid-state KOH-based chemical activation. The synthesized materials presented high surface area (3686.10 m² g^-1), large pore volume (1.88 cm³ g^-1), and tunable pore sizes. As a porous solid adsorbent, the optimized material adsorbs 5.59 mmoles of CO₂ per gram at 0 °C/1 bar, which is elevated to 37.47 mmoles g^-1 at 0 °C/30 bar along with a good CO₂/N₂ selectivity within a range ≈25-35 and also displays high recyclability of >99%. Electrochemically, in a three-electrode setup, a high specific capacitance of 261.5 F g^-1/0.5 A g^-1 is observed. For a two-electrode setup, a reasonable specific capacitance of 91.67 F g^-1/0.5 A g^-1, energy and power densities (18.33 Wh kg^-1 and 2274.94 kW kg^-1), and 87.5% capacity retention after 10 000 cycles are obtained. A low-cost and noncomplicated synthesis and high performance of materials for CO₂ adsorption and supercapacitors make a strong case for their high promise in these fields.