Ammonia gas adsorption study on graphene oxide based sensing device under different humidity conditions

Herein, we investigated ammonia (NH3) sensitivity of graphene oxide (GO) based sensing device through experimental and theoretical techniques. The Modified Hummer’s method was employed for the preparation of GO. The physical and chemical properties of GO were studied by using XRD, SEM/TEM, FT-IR, Raman, TGA/DSC. The BET surface area of GO sheets was found to be 37.24 m2/g. The GO sensing device was exposed to various ammonia concentrations ranging from 100 to 400 ppm. We have found the ammonia gas sensitivity of the GO has increased from 45 to 58% when the ammonia concentration was increased from 100 to 400 ppm. The ammonia sensitivity measurements were carried out under different humidity conditions and the sensitivity of GO was found to increase from 36 to 68% when the humidity level was increased from 11% to 75%. The interaction energy for the adsorption of NH3 by different functional groups (such as OH, -O-, COOH) on GO was calculated by using density functional theory. The interaction energy of carboxyl and hydroxyl groups found to be 46 kJ/mol and 37 kJ/mol respectively. The computation results were revealed that the hydroxyl and carboxyl groups are energetically more favorable for the adsorption of NH3 than the epoxy group on GO

Excellent Catalytic Effects of Graphene Nanofibers on Hydrogen Release of Sodium alanate

One of the most technically challenging barriers to the widespread commercialization of hydrogen-fueled devices and vehicles remains hydrogen storage. More environmentally friendly and effective nonmetal catalysts are required to improve hydrogen sorption. In this paper, through a combination of experiment and theory, we evaluate and explore the catalytic effects of layered graphene nanofibers toward hydrogen release of light metal hydrides such as sodium alanate. Graphene nanofibers, especially the helical kind, are found to considerably improve hydrogen release from NaAlH₄, which is of significance for the further enhancement of this practical material for environmentally friendly and effective hydrogen storage applications. Using density functional theory, we find that carbon sheet edges, regardless of whether they are of zigzag or armchair type, can weaken Al–H bonds in sodium alanate, which is believed to be due to a combination of NaAlH₄ destabilization and dissociation product stabilization. The helical form of graphene nanofibers, with larger surface area and curved configuration, appears to benefit the functionalization of carbon sheet edges. We believe that our combined experimental and theoretical study will stimulate more explorations of other microporous or mesoporous nanomaterials with an abundance of exposed carbon edges in the application of practical complex light metal hydride systems