Nitrogen diffusion in graphene oxide and reduced graphene oxide foils

Measurements of nitrogen diffusion coefficient in graphene oxide (GO) and reduced graphene oxide (rGO) have been performed at different temperatures ranging between 21◦C and 101◦C. GO and rGO foils have been prepared as thin foils with 15 μm in thickness, total surface of about 5 cm^2 and active diffusion surface of about 20 mm^2. The rGO foils have been obtained by thermal annealing at 170◦C for 30 min in air. The measured room temperature diffusion coefficients, of 3.43 × 10^(− 4) cm^2/s for GO and 5.1 × 10^(− 4) cm^2/s for rGO, and, at 101◦C, of 5.22 × 10^(− 4) cm^2/s for GO and 10.7 × 10^(− 4) cm^2/s for rGO, have been obtained with a simple experimental set-up measuring the gas pressure gradient applied to the two faces of the thin foils versus the time. The rGO foils show a significant increasing of the diffusion coefficients with respect to the pristine GO due to the removing of water and some functional oxygen groups which determines the aperture of nanochannels through which the N2 gas diffuses. The thermal activation energy of nitrogen diffusion is evaluated for the two investigated materials. The experimental apparatus to measure the diffusion coefficients, the obtained results, their correlation with the graphene sheets structure and the comparison with the literature data are presented and discussed.