Thin Film Electrodes and Electrochemical Reactions at Three-Phase Boundary in Alkaline Media: A DFT Approach
To determine the effectiveness of these electrodes, density functional theory (DFT) is employed. Before work was done to model the interphases, extensive work was done examining various moiré patterns for various oxidation states of transition metal films, with a focus on FeOxHy films. In this work, the stability of a variety of transition metal (hydr)oxide thin films on Pt and Au are first examined for stability for their future prospects of viable catalysts for fuel cell applications. In addition, phase diagrams are constructed to determine the state of the film at a given voltage, something crucial for designing optimal catalysts. A DFT + U scheme is employed to model the thin films, where U values are fitted by correcting the formation energies.
While the oxidation state and strain of the film are predicted from the full film phase diagrams, the nature of the interphase needed to be determined. The focus , hydrogen evolution and CO oxidation at these interphases with each reaction occurring at a different equilibrium potentials. This knowledge necessitated the creation of phase diagrams for the interfaces, to identify the most stable oxidation state the edge may take. With these phase diagrams, the thermodynamics and kinetics for the two reactions could be calculated with DFT along with nudged elastic band (NEB) calculations to calculate the activation barriers. These results are then compared with those on a clean Pt surface.
 R. Subbaraman, D. Tripkovic, K. Chang, D. Strmcnik, A. P. Paulikas, P. Hirunsit, M. Chan, J. Greeley, V. Stamenkovic, N. M. Markovic. Nature Materials. 11, 550 (2012)