title: Energetics and Solvation Effects at the Photoanode/Catalyst Interface: Ohmic Contact versus Schottky Barrier.
abstract: The design of optimal interfaces between photoelectrodes and catalysts is a key challenge in building photoelectrochemical cells to split water. Iridium dioxide (IrO2) is an efficient catalyst for oxygen evolution, stable in acidic conditions, and hence a good candidate to be interfaced with photoanodes. Using first-principles quantum mechanical calculations, we investigated the structural and electronic properties of tungsten trioxide (WO3) surfaces interfaced with an IrO2 thin film. We built a microscopic model of the interface that exhibits a formation energy lower than the surface energy of the most stable IrO2 surface, in spite of a large lattice mismatch, and has no impurity states pinning the Fermi level. We found that, upon full coverage of WO3 by IrO2, the two oxides form undesirable Ohmic contacts. However, our calculations predicted that if both oxides are partially exposed to water solvent, the relative position of the absorber conduction band and the catalyst Fermi level favors charge transfer to the catalyst and hence water splitting. We propose that, for oxide photoelectrodes interfaced with IrO2, it is advantageous to form rough interfaces with the catalyst, e.g., by depositing nanoparticles, instead of sharp interfaces with thin films.
authors: †Joint Center for Artificial Photosynthesis, California Institute of Technology and Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors: Yuan
authors: Y
authors: Ping
authors: †Joint Center for Artificial Photosynthesis, California Institute of Technology and Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.|‡Materials and Process Simulation Center, California Institute of Technology, Pasadena, California 91125, United States.
authors: William A
authors: WA
authors: Goddard
authors: §Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States.|∥Argonne National Laboratory, Lemont, Illinois 60439, United States.
authors: Giulia A
authors: GA
authors: Galli