Optimizing the micro/mesoporous structure of hierarchical graphene aerogel for CO2 capture by controlling the oxygen functional groups of graphene oxide

Background

Graphene aerogels as solid porous adsorbents are great candidates for CO₂ adsorption based on their tunable hierarchical pore structure and oxygenated groups on graphene oxide can control the self-assembly and pore structure of graphene aerogels.

Methods

Modified Hummer's method was used to synthesize graphene oxides by using various levels of H₂SO₄, KMnO_4, and H₂O₂ and 3D graphene aerogels were synthesized via the hydrothermal and freeze-drying method. FTIR, RAMAN, XRD, FE-SEM, and BET analysis were used for characterizations.

Significance findings

The effect of graphite oxidation conditions on the hierarchical porous structure of graphene aerogel for CO₂ adsorption was investigated. The graphene aerogel with the high meso and micro surface areas and the highest S_m/S_T value (micro surface area/total micro and meso surface area) of 33 % and also, the adequate macropores was achieved using high dosage of H₂SO₄ in the graphene oxidation process led to the highest CO₂ adsorption capacity of 1.72 mmol/g. increasing the H₂O₂ dosages increased the macropores in the aerogel structure and improved the value of S_m/S_T leading to an increase in the CO₂ adsorption capacity. The high content of KMnO₄ led to low S_m/S_T value and fewer macropores and decreased the CO₂ adsorption capacity (1.04 mmol/g).