Effect of the incorporation of GO on the adsorption performance of hydrogen on ZIF-8 composites for on board applications: By DFT calculations and experiments

Enhancing the storage capacity of hydrogen on MOFs and making it suitable for the marine environment are crucial to its onboard application as a hydrogen storage medium. Development of the storage medium was based on the density of hydrogen contained within the storage system equipped on a typical fuel cell powered ship. The researches conducted include density functional theory (DFT) calculations and experiments, which were directed to evaluate the effect of incorporating graphene oxide (GO) on enhancing the storage performance of hydrogen on ZIF-8. DFT calculations were performed to determine adsorption energies between the GO@ZIF-8 composites and hydrogen molecules, the reduced density gradient (RDG) scatter plot and isosurface map analysis were then employed to define the interaction mechanism between the GO and ZIF-8 as well as the GO@ZIF-8 composites and hydrogen molecules. Precipitation was employed at ambient temperature to synthesize the ZIF-8 sample and GO@ZIF-8 composites, which were performed the tests further for analyzing adsorption equilibrium as well as the performances of cycling and hydro-stability. Results show that the interaction between the GO and ZIF-8 as well as the GO@ZIF-8 composites and hydrogen molecules can be ascribed to the van der Waals force, and the interaction can be enhanced by incorporating a suitable amount of GO. Within the range 0–8 wt% amount of GO incorporated, the sample added by 2 wt% GO (GO-2@ZIF-8) had a more preferable structure for hydrogen adsorption, and the isosteric heat of hydrogen adsorption on this sample is larger than that on the ZIF-8. It also shows that the incorporation brought about the enhancement on the cycling performance at 77.15 K within 0–5 MPa as well as on the hydro-stability of the sample. It suggests that the composite prepared by incorporating ZIF-8 with GO is a promising medium for on board hydrogen storage.