Controllable synthesis of bifunctional porous carbon for efficient gas-mixture separation and high-performance supercapacitor

It is notably challenging to fabricate controllable heteroatom-doped porous carbons for both highly effective mixed-gas separation and supercapacitor electrodes. In this work, novel algae-derived nitrogen-containing porous carbons were prepared as bifunctional materials. The pore structure of obtained carbons could be easily tailored by altering activation temperature or porogen/biomass ratio. The as-prepared porous carbon has a very high specific surface area of 1538.7 m² g⁻¹ and a large pore volume of 0.99 cm³ g⁻¹ with a high N content of 2.77 wt%. As a solid-state adsorbent, the algae-derived carbon has an excellent CO₂ adsorption capacity of 5.7 and 3.9 mmol g⁻¹ at 273 and 298 K, respectively. The extraordinarily high CO₂/N₂, CO₂/CH₄, and CH₄/N₂ selectivity are demonstrated by the ideal adsorption solution theory (IAST) calculation and dynamic adsorption breakthrough experiments. As an electroactive material, the porous carbon exhibits outstanding capacitive performance in 6 M KOH aqueous electrolyte, with the specific capacitance of 287.7 and 190.0 F g⁻¹ at 0.2 A g⁻¹ in a three- and two-electrode system, respectively. Furthermore, the obtained carbon shows outstanding rate capability of 79.3% at 10 A g⁻¹ and unprecedented cycling stability with 98% capacitance retention at 10 A g⁻¹ after 8000 cycles as coin cell. This report introduces a biomass-derived and low-cost pathway to design porous carbon materials for efficient solid adsorbents and supercapacitive electrode materials.