Storage properties of 6,6,12-graphyne methane: a Monte Carlo and first-principles study

Abstract

The CH₄ adsorption performance of the Sc-modified 6,6,12-graphyne (Sc@6,6,12-GY) system has been investigated based on giant canonical Monte Carlo (GCMC) simulations and first-principles study. According to the GCMC simulation, the CH₄ adsorption amount of Sc-modified 6,6,12-GY can reach 72.21 wt% at 233 K and 40 bar. The first-principles study reveals that the binding energy is maximum (−5.181 eV) when the Sc atom is modified in the central hole site of the rhombic acetylene ring of 6,6,12-GY, which exceeds the cohesive energy of the Sc atom (−3.9 eV). The Sc@6,6,12-GY can adsorb 42 CH₄ molecules with an average adsorption energy of −0.178 eV and an adsorption capacity of 72.13 wt%, which exceeds the U.S. Department of Energy standard (50 wt%) and corroborates with the results obtained from the GCMC, verifying the accuracy of the results. The Sc atoms modulate the electronic structure of 6,6,12-graphene, and the Sc-modified 6,6,12-GY system is found to have good CH₄ storage properties as a high-capacity CH₄ storage material by analyzing the partial state of the density, charge transfer situation and charge differential density map of the substrate system.