Exploring kinetic and thermodynamic insights of graphene related two dimensional materials for carbon dioxide adsorption

Abstract

Graphene related two dimensional materials (GR2Ms) are promising adsorbents for CO2 capture. However, the CO2 adsorption kinetics and mechanisms on these materials remain insufficiently explored and understudied. Recognizing the pivotal role of adsorption kinetics in assessing the practical applicability, this study comprehensively evaluates the CO2 adsorption kinetics, underlying mechanisms, and thermodynamic properties via gravimetric analysis in three distinct well-characterized graphene materials (few layer graphene-FLG, graphene oxide-GO, reduced graphene oxide-rGO) across temperatures from 25 to 75 °C under atmospheric pressure. Results reveal that Avrami’s fractional model offers the most accurate fit for CO2 adsorption kinetics among the three examined models (pseudo-first, pseudo-second, and Avrami’s fractional order). The interplay between the physico-structural-chemical properties of GR2Ms and the CO2 adsorption kinetics discloses that the morphology, crystallite size, specific surface area and porosity of GR2Ms greatly influence the CO2 adsorption rate as evidenced by the largest rate constant, kA value of rGO at 25 to 75 °C under atmospheric pressure. Analysis of activation parameters including activation energy, enthalpy of activation, entropy of activation, and free energy of activation derived from Eyring, Arrhenius, and Gibbs equations indicates a greater favorability of CO2 adsorption on GR2Ms at lower temperatures. Moreover, investigation into the underlying interaction mechanisms between CO2 molecules and GR2Ms, using rate-limiting kinetic models (Boyd’s film diffusion model, interparticle diffusion model, and intraparticle diffusion model), confirms that both film diffusion resistance and intraparticle diffusion resistance predominantly govern the CO2 adsorption rate.