Mechanisms of adsorbing hydrogen gas on metal decorated graphene

Abstract

Hydrogen is a key player in global strategies to reduce greenhouse gas emissions. In order to make hydrogen a widely-used fuel, we require more efficient methods of storing it than the current standard of pressurized cylinders. An alternative method is to adsorb H${}_2$ in a material and avoid the use of high pressures. Among many potential materials, layered materials such as graphene present a practical advantage as they are lightweight. However, graphene and other 2D materials typically bind H${}_2$ too weakly to store it at the typical operating conditions of a hydrogen fuel cell. Modifying the material, for example by decorating graphene with adatoms, can strengthen the adsorption energy of H${}_2$ molecules, but the underlying mechanisms are still not well understood. In this work, we systematically screen alkali and alkaline earth metal decorated graphene sheets for the adsorption of hydrogen gas from first principles, and focus on the mechanisms of binding. We show that there are three mechanisms of adsorption on metal decorated graphene and each leads to distinctly different hydrogen adsorption structures. The three mechanisms can be described as weak van der Waals physisorption, metal adatom facilitated polarization, and Kubas adsorption. Among these mechanisms, we find that Kubas adsorption is easily perturbed by an external electric field, providing a way to tune H${}_2$ adsorption.

References in corpus (7)

• CP2K: An Electronic Structure and Molecular Dynamics Software Package -- Quickstep: Efficient and Accurate Electronic Structure Calculations
• Perspective: Advances and challenges in treating van der Waals dispersion forces in density functional theory
• Hydrogen storage of calcium atoms adsorbed on graphene: First-principles plane wave calculations
• The role of van der Waals forces in water adsorption on metals
• Effects of van der Waals Interactions in the Adsorption of Isooctane and Ethanol on Fe(100) Surfaces
• Spatially resolving density-dependent screening around a single charged atom in graphene
• Quantum Monte Carlo Calculations of Dihydrogen Binding Energetics on Ca Cations: an Assessment of Errors in Density Functionals for Weakly Bonded Systems

Cited by in corpus (3)

• Unravelling H${}_2$ chemisorption and physisorption on metal decorated graphene using quantum Monte Carlo
• Platinum-Decorated Graphene: Experimental Insight into Growth Mechanisms and Hydrogen Adsorption Properties
• Cooperative CO${}_2$ capture via oxalate formation on metal-decorated graphene