Easy hydrogenation and dehydrogenation of a hybrid graphene and hexagonal boron nitride monolayer on platinum

Abstract

Understanding the fundamental steps of adsorption and controlled release of hydrogen in two-dimensional (2D) materials is of relevance for applications in nanoelectronics requiring tuning the physical properties or functionalization of the material, hydrogen storage and environmental sensors. Most applications demand that hydrogen adsorption and desorption can be controlled at room temperature. Here we report an element-specific study on the hydrogenation and dehydrogenation, in a low coverage regime, of a quasi-free standing 2D heterostructure (h-BNG) in the form of coexisting lateral domains of isostructural hexagonal boron nitride (h-BN) and graphene (Gr) on Pt(111). At very low hydrogen coverage a selective and partial hydrogenation of the Gr domains is observed in h-BNG. At the same time no changes are detected in the h-BN domains, indicating a preferential hydrogenation of Gr rather than h-BN domains. At higher coverage, hydrogenation of both Gr and h-BN domains is detected. A thermally facile hydrogen release from h-BN domains near room temperature is observed. Furthermore, the hybrid h-BNG 2D heterostructure enables also a much easier H2 thermal release from Gr domains when compared with a full Gr monolayer grown on the same Pt(111) substrate. These results suggest that the presence of coexisting hydrogenated h-BN domains could destabilize C–H bonds in Gr.

Tracking Interfacial Changes of Graphene/Ge(110) During In-Vacuum Annealing

“…This red component is well fitted by a Doniach-Sunjic lineshape with the same asymmetry and width as the main peak, suggesting that its origin can be related to a portion of C atoms in the graphene layer rather than to a different chemical bonding. For example, the appearance of low-binding energy components has been observed for C atoms in graphene "lifted up" by gas molecules underneath, such as CO, O, H [34,35], or for C atoms in the graphene layer being subjected to modified core hole screening [36].…”

Boron nitride-graphene in-plane hexagonal heterostructure in oxygen environment

“…Several h-BNG samples were prepared using this procedure, all displaying identical core level line shapes and similar stoichiometry with Gr domains with predominant coverage (71±4%) and the remaining part composed of h-BN complementary domains, both up to hundreds of nanometers size/lateral dimension [11]. The growth was performed in an ultra-high vacuum (UHV) chamber connected to the synchrotronradiation photoemission measurement chamber of the CNR-IOM beamline BACH [12] at the synchrotron light source Elettra in Trieste.…”

“…2 which can be attributed to either Pt-O adsorption [31], or to the formation of Pt-C bonds [32]. Considering that O 1s peak related to oxygen chemisorbed on Pt is missing, this Pt 4f component may be associated with Pt-C bonds due to an increased hybridization between Pt and the overlayer, as it was observed after hydrogenation of graphene [32] or h-BNG [11]. (f-g) XPS data collected after subsequent and repeated growth-etching cycles.…”

“…The decrease of C appears to be linked with the increase of the B-O components in O 1s and B 1s. The 284.2 eV component can be assigned to sp 3 /undercoordinated carbon atoms bound to Pt [11]. Importantly, according to theoretical calculations, O 2 can dissociate at the B-C bridge site and lead to the stretching and eventual breaking of the B-C bonds with a relatively low activation energy [9].…”

“…1 (b)], which is not present at lower temperatures and doses. This additional oxygen component has the BE of oxygen chemisorbed on Pt(111) [31] and the Pt 4f component at 71.3 eV is generally associated with the formation of bonds between Pt and chemisorbed oxygen [31] or the 2D overlayer [11]. Therefore, the downshift of the h-BNG core levels can be associated with oxygen intercalation between Gr in h-BNG and Pt, and the O/Pt component with oxygen chemisorbed on platinum and intercalated under Gr.…”