Computational study of bulk and surface properties on ruthenium oxide (RuO₂)

Materials Modelling Centre, School of Physical and Mineral Sciences, University of Limpopo, Private Bag x1106, Sovenga 0727, South Africa.

Abstract

Metal oxides are widely used in lithium-air batteries to improve the formation of stable discharge products and improve lifespan and electrochemical performance. Despite the intense studies on metal oxides catalysts, ruthenium oxide attracted the most attention since it doesn’t only catalyse the redox processes but reduces the over-potential and stabilizes the Li cyclability. Hence, in this work we discuss the bulk and low Miler index surfaces of RuO₂ using the first principle density functional theory calculations. It was found that the lattice parameters are in good agreement with the reported results, with less than 1.4% difference. Furthermore, RuO₂ was also found to be mechanically stable with all positive independent elastic constants (C_ij) obeying the mechanical stability criteria and a positive tetragonal shear modulus (C’> 0). The bulk to shear ratio indicates that the structure is ductile. The density of states shows a slight pseudo gap for RuO₂ at the Fermi energy, which suggests that the structure is stable. Finally, low Miller index surfaces (i.e. (110), (010), (001), (111), and (101)) were modelled using METADISE code, and the most stable facet was in agreement with the reported literature.