Molecular insights into hydrogen adsorption on F-functionalized MXenes: a combined GCMC and molecular dynamics study

Abstract

Context

The increasing demand for sustainable energy carriers highlights the need for safe and efficient hydrogen storage materials. MXenes, owing to their layered structure and tunable surface chemistry, have emerged as promising candidates for solid-state hydrogen storage. In this study, hydrogen adsorption on Ti–C–based MXenes is systematically investigated with particular emphasis on the role of fluorine surface termination. The results show that pristine Ti–C MXene exhibits limited hydrogen uptake, whereas fluorine termination significantly enhances adsorption performance. Aluminum atoms, inherently present in the MXene-based structures considered, mainly contribute to the structural stability of the layered framework. A mixed Ti–C–Al–F configuration shows good agreement with available experimental data, particularly at higher pressures. Structural and dynamical analyses reveal pronounced H₂–F interactions and reduced hydrogen mobility near the MXene surface, while the calculated heats of adsorption indicate a physisorption-dominated mechanism favorable for reversible hydrogen storage. These findings provide a unified molecular-level understanding that links adsorption thermodynamics and diffusion behavior in MXene-based hydrogen storage systems.

Methods

Hydrogen adsorption was studied using a combined Grand Canonical Monte Carlo and molecular dynamics simulation approach implemented in the Materials Studio 2017 software package. GCMC simulations were used to generate adsorption isotherms at 298 K and pressures up to 35 bar, while molecular dynamics simulations were performed to analyze adsorption sites, diffusion behavior, and host–guest interactions. Interatomic interactions were described using classical force-field methods, with the Universal Force Field applied to MXene atoms and a rigid molecular model used for hydrogen.