Electronic Structure of IrO_2: The Role of the Metal d Orbitals
IrO_2 is one of the most active catalysts for the oxygen evolution reaction (OER) and remains the only known stable OER catalyst in acidic conditions. As a first step in understanding the mechanism for OER we carried out detailed Density Functional Theory (DFT) studies of the electronic structure of IrO_2. We compared the electronic states and magnetic properties of IrO_2 using several density functionals. We found that DFT with hybrid functionals (B3PW and PBE0) leads to a weak ferromagnetic coupling, although IrO_2 has often been reported as nonmagnetic. We also found a magnetic ground state for RuO_2, whose electronic structure is similar to that of IrO_2. Ru–Ru antiferromagnetic interaction has been observed experimentally in nanoparticle RuO_2. Further low temperature measurements are necessary to confirm whether a weak magnetism may occur below 20 K in IrO_2. We also found that PBE leads to a better agreement with the experimental XPS spectra, compared with hybrid functionals and PBE+U.
© 2015 American Chemical Society. ACS AuthorChoice - This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Received: January 27, 2015; Revised: April 22, 2015; Published: April 23, 2015. We thank Robert J. Nielsen, Mu-Jeng Cheng, and Ravishankar Sundararaman for useful discussions. This material is based on work performed at the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993.
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