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

Abstract

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).