Probing the chemical reactivity of the B2O3 -I (1 0 1) Surface: Interaction with H2O and H2S

Diboron trioxide is of interest because of its unique unreactive functionality properties. In this work we have studied – via computational first-principle techniques - the adsorption and dissociation mechanisms of two hydrogen chalcogenides, namely water (H2O) and hydrogen sulfide (H2S) molecules, over the B2O3 -I (1 0 1) surface. We show that the water molecules undergo dissociative adsorption over diboron via an activation energy of 39 kJ/mol. Furthermore, desorption of both molecularly adsorbed and dissociated structures of water molecules from the B2O3 -I (1 0 1) surface requires activation energies of 124–127 kJ/mol. Our investigation on the other hydrogen-chalcogenide compound, i.e. H2S, reveals that diboron trioxide attracts H2S molecules and forms molecular adsorption via sp3 hybridisation between the lone pair electron of the H2S and the empty p orbital of the Bsurf atom without encountering an activation barrier. However, the energy barrier required to dissociate H2S over the B2O3 -I (1 0 1) surface appears exceedingly high at 310 kJ/mol. The present insight resolves the two different behaviours of B2O3 concerning hydrogen chalcogenides reported in the literature. While acting as a water scavenger to generate dissociated radicals, it exhibits an inhibitor characteristic towards the dissociation of H2S molecules, representing an ideal reactor wall coating for desired pure gas phase reactions.