Density functional theory study of a graphene sheet modified with titanium in contact with different adsorbates

The present work is based on the theoretical study of the behavior of a graphene sheet decorated with titanium, in contact with different molecules. When the substrate is exposed only to hydrogen molecules, it is found to store up to four molecules per adatom, as already seen in the literature for single wall carbon nanotubes. Thus, titanium decoration is seen to considerably improve the hydrogen storage capacity of these carbon systems. However, it is found that low quantities of oxygen present in the gas phase should yield the oxidation of the titanium atoms, even when hydrogen is stored in the system. It is concluded that if the experimental system is exposed to air, titanium atoms on these surfaces are expected to oxidize to titanium dioxide, showing oxygen molecules to be very reactive species. Other chemicals present in air such as nitrogen or water molecules could also be chemisorbed onto the titanium adatom, but are less competitive with hydrogen.