%0 Journal Article
%@ 2475-9953
%A Al-Hamdani, Yasmine S
%A Zen, Andrea
%A Michaelides, Angelos
%A Alfè, Dario
%D 2023
%F discovery:10167826
%I American Physical Society (APS)
%J Physical Review Materials
%N 3
%T Mechanisms of adsorbing hydrogen gas on metal decorated graphene
%U https://discovery.ucl.ac.uk/id/eprint/10167826/
%V 7
%X 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 H2 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 H2 too weakly to store it at the typical operating  conditions of a hydrogen fuel cell, meaning that high pressure would still be required. Modifying the material,  for example by decorating graphene with adatoms, can strengthen the adsorption energy of H2 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 static thermodynamic 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 H2 adsorption. This work is foundational and builds our understanding of  H2 adsorption under idealized conditions.
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