A computational view on the thermochemical and electrochemical stability of ruthenium oxides

Abstract

Ruthenium oxides (RuO_x) display suitable activities for a number of electrocatalytic reactions, such as chlorine evolution and oxygen evolution. However, their corrosion resistance still ought to be enhanced and the instabilities are often attributed to the transformation of one Ru oxide into another. Density functional theory (DFT) calculations can help understand and improve the thermochemical and electrochemical stability of RuO_x. However, in this work, we show that a wide variety of exchange-correlation functionals are visibly inaccurate for the thermochemistry of gas-phase and solid-state RuO_x. The inaccuracies can be systematically mitigated, as they grow alongside the number of oxygen atoms in the compounds because of the repulsive interactions among Ru–O bonds. Furthermore, Pourbaix diagrams, which are electrochemical phase diagrams outlining the conditions of electrode stability, are shown to be significantly affected by these inaccuracies. Seamlessly, our simple correction scheme brings computational Pourbaix diagrams close to experimental results, giving confidence in the predictiveness of future stability studies.