First principles evaluation of the OER properties of TM−X (TM = Cr, Mn, Fe, Mo, Ru, W and Os, and X = F and S) doped IrO2 (110) surface

Using first-principles calculations, we investigated the energetics and structural properties of cation substitutional doping (TM = Cr, Mn, Fe, Mo, Ru, W, Os), anion substitutional doping (F and S), as well as a cation-anion dopant complexes (TM-X) incorporated in an IrO2 (110) surface slab. All the defect configurations resulting from substitutional doping and their complexes were found to be energetically favorable. Also, the various dopant atoms resulted in low lattice distortion on the IrO2 surface, with changes in the bond lengths. All the oxygen evolution reaction (OER) intermediate species (O, OH and OOH) were found to adsorb favorable on the various considered surface configurations. Considering the changes in bond lengths of the OH and OOH intermediate species, we found that the OOH adsorbate species disintegrated on the OsIr and WIr + FO configurations in the IrO2 surface slab to O and OH species. This implies that those configurations are unsuitable for the OER reaction. We found that the presence of the Mo, Os and W dopant atoms resulted in higher over-potential (ηOER) compared with the pristine IrO2. The electrochemical-step symmetry index (ESSI) versus ηOER showed that the MnIr + So, FeIr + Fo, CrIr + So and So dopant configurations resulted in the most improved OER activity. Thus, the consideration of the bond dissociation and free energies, the ηOER, and ESSI versus the ηOER provides significant insight towards assessing catalytic materials for the OER.