Atomic-level mechanisms of methane absorption in silica-based porous materials with non-uniform faults: Enhancing adsorption via surface faults

Abstract

Natural gas is a promising clean energy source, but its storage and transport remain challenging. This work demonstrates that a novel silica-based porous structure with non-uniform faults can significantly enhance methane absorption, as revealed through large-time molecular dynamics (MD) simulations of 1500 ns. Silica nanoparticles with random faults were constructed under methane conditions (5 atm), and a validated method was developed to identify absorbed methane molecules, showing good agreement with experimental data. Our findings reveal that optimizing fault density results in a 111 % increase in methane absorption compared to fault-free structures. Absorbed methane molecules form three layers: an absorption layer, a Knudsen layer, and a bulk layer. Faults enhance solid–gas interactions in the absorption layer and gas–gas interactions in the Knudsen layer. However, increasing temperature significantly reduces methane absorption, for which we propose a temperature-absorption relationship. These insights provide a foundation for designing nanostructures optimized for methane storage and selective absorption applications.