CO2 diffusion in graphene oxide and reduced graphene oxide foils and its comparison with N2 and Ar

Measurements of the carbon dioxide (CO 2 ) diffusion in graphene oxide (GO) and reduced graphene oxide (rGO) vs. temperature have been performed using uniform GO thin foils with15 μm thickness. Regarding rGO, its foils have been obtained by submitting GO at a temperature of 130 °C in vacuum for 30 min. The CO 2 diffusion has been controlled by the gas pressure gradient applied to two faces of the thin foils versus the time and the temperature. The calculated CO 2 coefficient diffusions have been compared with those relative to the nitrogen (N 2 ) and argon (Ar) gases obtained in previous measurements. The deduced diffusion coefficients are different for the three investigated gases, but remain of the order of 10 –3 cm 2 /s. At room temperature in GO the minimum value is obtained for nitrogen, while the highest one for Ar. Indeed, at 100 °C in rGO the minimum value is deduced for nitrogen and the maximum one for the carbon dioxide. The different diffusion coefficients can be attributed not only to the different size, shape and atomic mass of the investigated gases, but also to the inner lattice structure of the GO and rGO foils. GO contains water and oxygen functional groups which obstacle the diffusion process. rGO is poorer of oxygen functional groups and of water, partially enhancing the diffusion, but it has a high compactness and density which may reduce the total diffusivity. The obtained results, their correlation with the inner structure of the graphene sheets and the comparison between measurements and the literature data are presented and discussed.