Effects of gaseous environments on physicochemical properties of thermally exfoliated graphene oxides for hydrogen storage: a comparative study

Abstract

The present study compared the effect of different gaseous environments on physicochemical properties and subsequent hydrogen storage ability of thermally exfoliated graphene oxide (EGO). The reducing, inert or oxidizing environments were generated using hydrogen, argon or air as the carrier gas, respectively. The structure of thermally exfoliated graphene oxide depended on the type of gaseous environment. The EGO prepared in presence of Air showed the fluffiest layered structure having highest surface area. The surface area order was EGO(Air) (268 m 2 /g) > EGO(H 2 ) (248 m 2 /g) > EGO(Ar) (155 m 2 /g). The average pore sizes of EGO(Air) and EGO(H 2 ) were 2.9 and 2.8 nm, with pore volumes of 1.2 and 1.6 cm 3 /g, respectively. The average pore size for EGO(Ar) was highest at 4.1 nm, associated with presence of larger void space and lowest total pore volume of 1.0 cm 3 /g. Thus, presence of oxidative or reducing atmosphere seemed to be more conducive to exfoliation of layers by gradual removal of functional groups. The inert atmosphere of argon caused severe thermal separation of layers and functional groups, adversely affecting the layered structure as observed. The EGO(Air) also showed highest O/C ratio suggesting presence of significant amount of oxygen-containing functional groups on the surface. The hydrogen uptake order at 77 K and 30 bar was: EGO (Air) 3.34 wt.% > EGO (H 2 ) 3.12 wt.% > EGO (Ar) 2.2 wt.%. The highest uptake of EGO(Air) might have resulted from highest surface area, highest O/C ratio and presence of considerable pore volume.

Augmenting the performance of thermally deoxygenated graphite oxide supercapacitor electrodes using 6 M KOH electrolyte with K3Fe(CN)6 redox additive

“…The separation between layers is evident for TDGO300 and TDGO400, resulting in a large surface area. 26…”

Research on Three-Dimensional Porous Composite Nano-Assembled α-MnO2/Reduced Graphene Oxides and Their Super-Capacitive Performance

“…After hydrothermal recombination, the content of C−OH and C−O−C in the composite were significantly decreased, and the characteristic peak of O−C=O disappeared, indicating that most of the GO had been reduced and a small amount of C-OH and C−O−C remained on the surface. In Figure 7 c, 641.9 eV± corresponds to the electron binding energy of Mn2p 3/2 , and 653.5 eV± corresponds to the electron binding energy of Mn2p 1/2 [ 43 ], indicating the presence of Mn in the three-dimensional composite sample in two valence states: Mn 4+ (641.9 eV) and Mn 3+ (653.5 eV).…”

Recent Progress Using Solid-State Materials for Hydrogen Storage: A Short Review

“…Graphitic carbons, which are sp 2 hybridized and have a sheet-like structure, interact using van der Waals forces. Singh et al synthesized exfoliated graphite oxide (EGO) with a thermal exfoliation method under various gas conditions [130]. Air-exfoliated EGO represents a specific surface area of 268 m 2 g −1 , average pore size of 2.9 nm, and total pore volumes of 1.2 cm 3 g. The maximum hydrogen uptake of EGOs was 3.34 wt% at 77K and 30 bar.…”

“…(a) Preparation process of thermally exfoliated graphene oxide (EGO) under various gas conditions, (b) N2 adsorption-desorption isotherms, (c) pore size distributions, (d) hydrogen uptakes at 77 K and 30 bar, and (e) cycle stability for hydrogen uptake under 5 cycles. Reproduced from ref [130]…”