Nanoporous activated biocarbons with high surface areas from alligator weed and their excellent performance for CO₂ capture at both low and high pressures

We report on the preparation of highly efficient nanoporous activated biocarbons (NABs) from alligator weed with high surface areas, pore volumes, tunable microporosity and oxygen functional groups for carbon dioxide adsorption. Alligator weed is converted into a non-porous carbon at 600 °C, which is then activated using potassium hydroxide at 800 °C through liquid state chemical activation. The simple synthesis provides easy control over experimental conditions which are carefully manipulated to yield the optimized material with a high specific surface area (3106 m² g⁻¹) and a high pore volume (1.62 cm³ g⁻¹). It is also demonstrated that the microporosity and surface oxygen functional groups can be controlled with a simple adjustment of the amount of potassium hydroxide. Owing to the excellent textural features, the optimized material adsorbed a high amount of carbon dioxide at 0 °C (30.4 mmol g⁻¹), 10 °C (27.7 mmol g⁻¹) and 25 °C (23.3 mmol g⁻¹) at a high pressure of 30 bar, which is much higher than that of activated carbon, ordered nanoporous carbon and mesoporous silicas. It also shows a low value of isosteric heat of adsorption (~22 kJ mol⁻¹) that indicates physical adsorption. The material with high microporosity shows impressive carbon dioxide adsorption capacity of 6.4 mmol g⁻¹ at 0 °C and low pressure of 1 bar. The high and low pressure carbon dioxide adsorption values indicate that the materials are promising adsorbents for carbon dioxide and the physical adsorption implies an easier regeneration. These findings suggest that biomass alligator weed can be utilized for devising advanced nanomaterials with high porosity for carbon capture.