Easy Hydrogenation and dehydrogenation of a hybrid graphene and hexagonal boron nitride monolayer

Insights into the mechanism of hydrogenation and dehydrogenation of a quasi-free standing Gr-h-BN monolayer are achieved by temperature-programmed photoemission. 
2D Materials (2021)
DOI: https://doi.org/10.1088/2053-1583/abda10
Adsorption and controlled release of hydrogen in 2D materials are at the base of many applications in energy storage, sensing and logic-devices. Among 2D materials, graphene (Gr) shows remarkable properties both for the hydrogen storage and release. However, the very strong C–H bond in hydrogenated Gr hinders practical applications.

At  the BACH beamline of IOM-CNR we address experimentally the impact of hydrogenation on a 2D heterostructure where Gr is laterally merged to isostructural h-BN in a single layer (h-BNG) on a  Pt(111) substrate and we demonstrate how different can be the reactivity of 2D materials when combined in lateral heterostructures. H-BNG can be grown via a simple single precursor route which is easily adaptable to industrial processes aiming at engineering the band gap of Gr. In h-BNG the behavior of Gr and h-BN towards hydrogenation can be compared in identical conditions and environment. Using high-resolution synchrotron radiation x-ray photoemission spectroscopy (XPS), temperature-programmed XPS and near-edge x-ray absorption fine structure spectroscopy (NEXAFS) we have investigated the room temperature hydrogenation and the hydrogen thermal release in the h-BNG single-layer on Pt(111) after exposure to atomic and molecular hydrogen. This element-specific, surface science approach yields several insights. 

In particular, we find that it is possible to hydrogenate the h-BNG single-layer on Pt(111) and that only Gr domains get hydrogenated at very low coverages. 
We have also observed that hydrogen is released more easily and near room temperature from h-BN domains than from Gr domains in h-BNG.
Finally we have compared the behavior of this mixed h-BNG in-plane heterostructure with a single layer Gr on Pt(111) exposed to H in the same conditions. We have found that the release of H2 from hydrogenated h-BNG on Pt(111) occurs at considerably  lower temperature compared with pure graphene. Since most applications require safety and full and facile control over reversible storage at or near room temperature, this findings may have implications in the exploitation of this class of lateral heterostructures. Applications  in nanoelectronic sensing and logic devices  requiring tuning the physical properties or functionalization of the material can be foreseen. This opens also perspectives in the use of this material for hydrogen storage due to its analogy with Gr, but its lower hydrogen release temperature. 

We acknowledge support from MUR (Eurofel project, FOE progetti internazionali).

Easy Hydrogenation and dehydrogenation of a hybrid graphene and hexagonal boron nitride monolayer on platinum 
Igor Píš, S. Nappini, Mohammad Panahi, Abdullah Kahraman, Elena Magnano, Sarp Kaya, and Federica Bondino*
2D Materials, https://doi.org/10.1088/2053-1583/abda10 (just accepted January 2021)

*Corresponding author

Last Updated on Thursday, 14 January 2021 19:52