First-principles based microkinetic modeling of borohydride oxidation on a Au(1 1 1) electrode

Borohydride oxidation electrokinetics over the Au(1 1 1) surface are simulated using first-principles determined elementary rate constants and a microkinetic model. A method to approximate the potential dependent elementary step activation barriers based on density functional theory calculations is developed and applied to the minimum energy path for borohydride oxidation. Activation barriers of the equivalent non-electrochemical reactions are calculated and made potential dependent using the Butler-Volmer equation. The kinetic controlled region of the borohydride oxidation reaction linear sweep voltammogram over the Au(1 1 1) surface is simulated. The simulation results suggest that B-H bond containing species are stable surface intermediates at potentials where an oxidation current is observed. The predicted rate is most sensitive to the symmetry factor and the BH₂OH dissociation barrier. Surface-enhanced Raman spectroscopy confirms the presence of BH₃ as a stable intermediate.