Chemisorption of Hydroxide on 2D Materials from DFT Calculations: Graphene versus Hexagonal Boron Nitride (original) (raw)

2016, The Journal of Physical Chemistry Letters

Recent nanofluidic measurements revealed strongly different surface charge measurements for boron-nitride and graphitic nanotubes when in contact with saline and alkaline water. 1,2 These observations contrast with the similar reactivity of a graphene layer and its boron nitride counterpart, using Density Functional Theory (DFT) framework, for intact and dissociative adsorption of gaseous water molecules. Here, we investigate, by DFT in implicit water, single and multiple adsorption of anionic hydroxide on single layers. A differential adsorption strength is found in vacuum for the first ionic adsorption on the two materials-chemisorbed on BN while physisorbed on graphene. The effect of implicit solvation reduces all adsorption values resulting in a favorable (non-favorable) adsorption on BN (graphene). We also calculate a pK a 6 for BN in water, in good agreement with experiments. Comparatively, the unfavorable results for graphene in water echoes the weaker surface charge measurements, but points to an alternative scenario.