CO2 and H2 adsorption on 3D nitrogen-doped porous graphene: Experimental and theoretical studies

Abstract

Carbon dioxide (CO2) and hydrogen (H2) adsorptions were investigated on 3D nitrogen-doped porous graphene (GO-PAA) produced by chemical activation of graphene oxide impregnated with polyallylamine (PAA). GO-PAA characterizations by Raman and X-ray photoelectron spectroscopies, thermogravimetric analysis, N2 adsorption-desorption isotherms, scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed that GO-PAA shows excellent thermal stability, decomposing at temperatures higher than 450 °C, specific surface area of 1155 m2 g−1, with pyrrolic, pyridinic and graphitic nitrogen atoms homogeneously dispersed throughout its 3D porous structure. The mesoporous nature of GO-PAA and the nitrogen doping level of 7.5 wt% resulted in remarkable H2 (1.3 wt%) and CO2 (20 mmol g−1) adsorption capacities at room temperature (RT, 25 °C) under high-pressure regime (40 bar). This H2 adsorption capacity at RT is among the highest values reported in the open literature. The role of the nitrogen atoms on the gas adsorption properties was investigated by combining experimental data, such as isosteric heat and Diffuse Reflectance Infrared Fourier Transform spectroscopy, with theoretical calculations using Density-Functional Theory. Inclusion of nitrogen atoms in the graphene structure reduces the energies of the Frontier Molecular Orbitals, facilitating polarization and increasing the interaction energy.