Solvated ions as defects in liquid water: A first-principles perspective

Understanding the electronic properties of solvated ions is crucial in order to control and engineer aqueous electrolytes for a wide variety of emerging energy and environmental technologies, including photocatalytic water splitting. In this talk, we present a strategy to evaluate electronic energy levels of simple solvated ions in aqueous solutions, using a combination of first-principles molecular dynamics simulations and many-body perturbation theory within the GW approximation. We considered CO$_3^{2-}$, HCO$_3^{-}$, NO$_3^{-}$, NO$_2^{-}$ ions and we show that by analogy to defects in semiconductors, these solvated ions may be classified as deep or shallow defects in liquid water. In particular CO$_3^{2-}$ and NO$_2^{-}$ ions behave as shallow defects, while HCO$_3^{-}$ and NO$_3^{-}$ as deep ones. We also show that the inclusion of many-body corrections constitutes significant improvement over conventional density functional theory calculations, yielding satisfactory agreement with photoemission experiments.