Sustainable and hierarchical porous Enteromorpha prolifera based carbon for CO₂ capture

Nitrogen-containing porous carbon was synthesized from an ocean pollutant, Enteromorpha prolifera, via hydrothermal carbonization and potassium hydroxide activation. Carbons contained as much as 2.6% nitrogen in their as-prepared state. Physical and chemical properties were characterized by XRD, N₂ sorption, FTIR, SEM, TEM, and elemental analysis. The carbon exhibited a hierarchical structure with interconnected microporosity, mesoporosity and macroporosity. Inorganic minerals in the carbon matrix contributed to the development of mesoporosity and macroporosity, functioning as an in situ hard template. The carbon manifested high CO₂ capacity and facile regeneration at room temperature. The CO₂ sorption performance was investigated in the range of 0-75°C. The dynamic uptake of CO₂ is 61.4mg/g and 105mg/g at 25°C and 0°C, respectively, using 15% CO₂ (v/v) in N₂. Meanwhile, regeneration under Ar at 25°C recovered 89% of the carbon's initial uptake after eight cycles. A piecewise model was employed to analyze the CO₂ adsorption kinetics; the Avrami model fit well with a correlation coefficient (R²) of 0.98 and 0.99 at 0°C and 25°C, respectively.