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Together with borazine, ammonia borane is a prominent precursor molecule for the formation of hexagonal boron nitride, which is of high interest as a 2D-material and graphene analog. Ammonia borane is also a possible solid hydrogen carrier for renewable energies with high storage density. Using X-ray photoelectron spectroscopy and temperature-programmed desorption, we investigated low-temperature adsorption and dehydrogenation during heating of borazine and ammonia borane on Ni(111) to form h-BN. For borazine, we observe the formation of disordered boron nitride above 300 K, which starts to form hexagonal boron nitride above 600 K. Ammonia borane shows multiple dehydrogenation steps at the boron and nitrogen atoms up to 300 K. This results in various BHxNHy species, including borazine-like intermediates, before the formation of disordered boron nitride and finally hexagonal boron nitride, analogous to the borazine decomposition. [ABSTRACT FROM AUTHOR]

We present detailed studies on the covalent adsorption of molecular oxygen and atomic hydrogen on the hexagonal boron nitride (h‐BN) nanomesh on Rh(111). The functionalization of this two‐dimensional (2D) material was investigated under ultra‐high vacuum conditions using synchrotron radiation‐based in situ high‐resolution X‐ray photoelectron spectroscopy, temperature‐programmed X‐ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. We are able to provide a deep insight into the adsorption behavior and thermal stability of oxygen and hydrogen on h‐BN/Rh(111). Oxygen functionalization was achieved via a supersonic molecular beam while hydrogen functionalization was realized using an atomic hydrogen source. Adsorption of the respective species was observed to occur selectively in the pores of h‐BN leading to spatially defined modification of the 2D layer. The adsorption of the observed molecular oxygen species was found to be an activated process that requires high‐energy oxygen molecules. Upon heating to 700 K, oxygen functionalization was observed to be almost reversible except for small amounts of boron oxides evolving due to the reaction of oxygen with the 2D material. Hydrogen functionalization of h‐BN/Rh(111) was fully reversed upon heating to about 640 K. [ABSTRACT FROM AUTHOR]

The interaction of single‐layer hexagonal boron nitride (h‐BN) on Ni(111) with molecular oxygen from a supersonic molecular beam led to a covalently bonded molecular oxygen species, which was identified as being between a superoxide and a peroxide. This is a rare example of an activated adsorption process leading to a molecular adsorbate. The amount of oxygen functionalization depended on the kinetic energy of the molecular beam. For a kinetic energy of 0.7 eV, an oxygen coverage of 0.4 ML was found. Near‐edge X‐ray adsorption fine structure (NEXAFS) spectroscopy revealed a stronger bond of h‐BN to the Ni(111) substrate in the presence of the covalently bound oxygen species. Oxygen adsorption also led to a shift of the valence bands to lower binding energies. Subsequent temperature‐programmed X‐ray photoelectron spectroscopy revealed that the oxygen boron bonds are stable up to approximately 580 K, when desorption, and simultaneously, etching of h‐BN set in. The experimental results were substantiated by density functional theory calculations, which provided insight to the adsorption geometry, the adsorption energy and the reaction pathway. [ABSTRACT FROM AUTHOR]

2D materials, covalent functionalization, hexagonal boron nitride nanomesh, high-resolution photoemission spectroscopy, spatially defined chemical modification Keywords: 2D materials; covalent functionalization; hexagonal boron nitride nanomesh; high-resolution photoemission spectroscopy; spatially defined chemical modification EN 2D materials covalent functionalization hexagonal boron nitride nanomesh high-resolution photoemission spectroscopy spatially defined chemical modification 13095 13095 1 09/17/21 20210915 NES 210915 B By using an atomic hydrogen source b and a supersonic molecular beam of oxygen, the hexagonal boron nitride nanomesh on Rh(111) was covalently functionalized with molecular oxygen and atomic hydrogen. Cover Feature: Selective Oxygen and Hydrogen Functionalization of the h-BN/Rh(111) Nanomesh (Chem. Eur. J. 52/2021). [Extracted from the article]