Electronic Structure of IrO2: 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.