Facile synthesis of macroalgae-derived graphene adsorbents for efficient CO2 capture

Abstract

Graphene, emerging as one of the most promising class of adsorptive separation carbon material for its high specific surface area and strong surface chemical activity. Biomass especially sustainable biomass as graphene sources shows great potential at large scales under energy shortage era. In this paper, a kind of subtropical macroalgae (Sargassum Horneri, S.H.) was selected as the precursor, and a facile synthesis method based on KOH activation was used to prepare graphene. A continuous monitoring on the formation of graphene and a systematic investigation into biomass precursor were performed, paying special attention to parameters including activation temperature, the alkali and carbon ratio, the corresponding pore structure, and surface chemistry variation. Moreover, the CO2 adsorption properties of porous graphene were tested. The results showed that, S.H. is a kind of ideal graphene precursor. The optimum preparation of porous graphene by KOH activation was the carbonization temperature of 400 °C, the alkali carbon ratio of 4:1 and the activation temperature of 850 °C. The porous graphene displayed high specific surface area (∼1411 m2/g), pore volume (∼1.16 cm3/g), and abundant microporous and mesoporous structures. The as-prepared porous graphene exhibited good CO2 uptake capacity as 2.78 mmol/g at 30 °C and 1 bar. The CO2 adsorption rate equations of the graphene were consistent with the intraparticle diffusion model, indicating that the CO2 adsorption was mainly controlled by the pore structure, and additionally influenced by the chemical functional groups especially N on the surface.