Preparation of N-doped activated carbons with high CO2 capture performance from microalgae (Chlorococcum sp.)
Abstract
N-Doped activated carbons with high CO2 adsorption capacity have been prepared from sugar-rich microalgae (Chlorococcum sp.) feedstock via simple hydrothermal carbonization coupled with KOH activation or NH3 modification. The KOH activated carbons exhibit higher CO2 capture performance compared with the ones treated by NH3. The nitrogen-enriched hydro-char derived from microalgae was activated with KOH at 700 °C to improve the textural characteristics (surface area, pores size, and total pore volume), and the resulting carbon showed a highly ordered structure with a surface area of 1745 m2 g−1, and narrow pore size distribution with the maxima peak located in the micropore range (<1.0 nm). The activated carbon exhibited CO2 uptakes of 4.03 and 6.68 mmol g−1 at 25 °C and 0 °C, respectively. Further XPS analysis revealed the effective pyridonic-nitrogen species (up to 58.32%) on the carbon surface favored a higher CO2 capture capacity. The N-doped activated carbons displayed rapid adsorption kinetics with ultrahigh selectivity for CO2 over N2 (up to 11 at 25 °C), and no obvious decrease in the CO2 uptake capacity was observed even after seven cycles, which may be due to the dominant physisorption between CO2 and the surface of carbon.
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