Experimental and simulation study of the effect of surface functional groups decoration on CH_4 and H_2 storage capacity of microporous carbons

摘要

The incorporation of heteroatoms (i.e. N, O, S, F) into the microporous carbon framework is proposed to affect the interactions between adsorbates and adsorbents and improve the efficiency of gas storage. We demonstrate a facile synthesis of coal-derived activated carbons (ACs) modified with oxygen and nitrogen-containing groups for CH4 and H-2 storage application. The functionalised ACs showed to have a high surface area of 1617-1924 m(2)/g, and pore volume of 0.85-0.92 cm(3)/g. The AC samples prepared by pre-oxidation followed by amination possess comparatively high CH4 adsorption capacity of 13.8 to 14.2 mmol/g at 298 K and 40 bar. However, the pristine AC and the oxidised AC showed the maximum H-2 adsorption capacity with 0.6 mmol/g and 0.44 mmol/g, respectively, at 20 bar and 298 K. Density functional theory (DFT) calculations were performed to study the adsorption of CH4 and H-2 on the ACs with/without the surface functional groups. In agreement with the experimental results, the computational analysis showed an increase in the gas-solid interaction after surface modification. Finally, a well-known method of Grand Canonical Monte Carlo (GCMC) was used to simulate the studied gas adsorption systems and calculate the adsorption isotherms of CH4 and H-2 on different ACs.