Nanoporous spongy graphene: Potential applications for hydrogen adsorption and selective gas separation

Abstract

In the present work, a nanoporous (pore width 0.7nm) graphene-based sponge-like material with large surface area ( 350m2/g) was synthesized by wet chemical reduction of graphene oxide in combination with freeze-drying. Surface morphology and elemental composition were studied by scanning and transmission electron microscopy combined with energy dispersive X-ray spectroscopy. Surface chemistry was qualitatively examined by Fourier-transform infrared spectroscopy, while the respective structure was investigated by X-ray diffraction analysis. Textural properties, including Brunauer–Emmet–Teller (BET) surface area, micropore volume and surface area as well as pore size distribution, were deduced from nitrogen gas adsorption/desorption data obtained at 77K and up to 1bar. Potential use of the spongy graphene for gas storage and separation applications was preliminarily assessed by low-pressure (0–1bar) H2, CO2 and CH4 sorption measurements at different temperatures (77, 273 and 298K). The adsorption capacities for each gas were evaluated up to 1bar, the isosteric enthalpies of adsorption for CO2 (28–33kJ/mol) and CH4 (30–38kJ/mol) were calculated using the Clausius–Clapeyron equation, while the CO2/CH4 gas selectivity (up to 95:1) was estimated using the Ideal Adsorbed Solution Theory (IAST).

•Nanoporous sponge produced by chemical reduction of graphene oxide and freeze-drying•Characterization performed using SEM, EDS, TEM, FT-IR, BET and XRD methods•Gas storage performance evaluated towards H2, CO2 and CH4 adsorption up to 1bar•CO2 over CH4 gas selectivity estimated between 45 and 95 at 273K using the IAST model