Delimiting the boron influence on the adsorptive properties of water and ○OH radicals on H-terminated Boron Doped Diamond catalysts: A Density Functional Theory analysis

Motivated for the success of Boron Doped Diamond (BDD) in electrocatalysis, where water and hydroxyl radical interactions play an overriding role on surface reactivity, this study presents a Density Functional Theory (DFT) analysis intended to correlate its structure and reactivity. H-terminated periodic surfaces (supercells 5 x 5) with atomic composition of one boron per 150 C atoms are used for these purposes, and where B position was varied in different layers. Analyses of total density of states (TDOS), localization of occupied and unoccupied states near the Fermi level and adsorption energies show that the effect of B doping on surface reactivity decreases as a function of its vertical distance from the BDD surface, and it is restricted to the first three surface layers. The adsorption free energy calculated for a water molecule corroborates the hydrophobic nature of these surfaces, becoming more repulsive as B is located within the first three surface layers. In contrast, the free energy computed for hydroxyl radical is always exergonic. Hydrogen abstraction by hydroxyl radical is an energy enabled process for all surface hydrogens, regardless if they are bonded to C or B atoms, becoming more energetic when hydrogemis directly bonded to B or its nearest neighbor carbon, while other abstractions present very similar adsorption energies than in the absence of boron. (C) 2016 Elsevier B.V. All rights reserved.