Theoretical modelling of adsorption of hydrogen onto graphene, MOFs and other carbon-based substrates

Abstract

Adsorption of molecular hydrogen () onto graphene and other carbon-based substrates is currently a research area of interest, where molecular-based approaches are required to describe thermodynamic properties of this and other related systems. We present a semiclassical theoretical framework to model adsorption isotherms of quantum fluids such as , based on the statistical associating fluid theory for chain molecules interacting with potentials of variable range for classical and quantum bulk fluids (SAFT-VRQ), and its extension to describe adsorbed systems (SAFT-VR-2D). Although the application of the theory relies on the determination of eight molecular parameters, seven of them can be obtained from bulk thermodynamic properties, the ratio of the critical temperatures of the adsorbed and bulk phases, and theoretical estimations about the range of the surface-particles potential and the energy depth of the particle–particle potential of the adsorbed fluid. The energy depth of the surface-particle potential, ε_w, is the free molecular parameter that can be obtained by fitting to experimental data of adsorption isotherms. Results obtained for ε_w according to this procedure are consistent with experimental values of the isosteric heat and the prediction of adsorption isotherms is in very good agreement with the experimental data.

Keywords:

• adsorption isotherms
• quantum fluids
• semiclassical methods

Acknowledgements

We acknowledge Carlos Avendaño (University of Manchester), José Torres Arenas and Ramón Castañeda-Priego comments and suggestions in relation to the work presented here.

Additional information

Funding

This work is supported by PROMEP, Universidad de Guanajuato, Convocatoria Institucional 2013 [grant number 307]; CONACYT, V.M. Trejos PhD scholarship.