Density functional theory applied to electrocatalysis

Abstract

Abstract A combination of density functional theory (DFT) and thermodynamic considerations is used to evaluate the electrochemical ( a , T , Δϕ) phase diagram for Pt(111) in contact with an aqueous electrolyte, which is then compared with experimental data. After specifying the electrode potential region at which no surface oxidation or oxide formation occurs, DFT calculations on the reaction of H 2 + 1/2O 2 → H 2 O over a Pt catalyst via direct oxygen reduction are discussed. Within these studies we first examine the binding characteristics and energetics for each likely intermediate chemisorbed on the Pt(111) surface, modeled by a 35‐atom cluster: O, H, O 2 , H 2 , OH, OOH, H 2 O 2 , and H 2 O. Then, the pathways for the dissociation processes of the various intermediates were calculated. Using binding energies and dissociation barriers, two main reaction mechanisms could be distinguished: O 2 dissociation and OOH/H 2 O 2 formation. While the latter one is the only mechanism to be expected when neglecting the surrounding water, both pathways have almost comparable reaction barriers when taking water into account.