Oxidation of Hydrated Hydrogen Sulfide

Sarah Floris

Abstract

Non-renewable energy resources are becoming depleted, and storing solar energy in the chemical bonds of molecules is an attractive alternative. The splitting of water into hydrogen and oxygen is one potentially viable option; however, many mechanistic details remain unknown. Motivated by the known similar oxidation of hydrogen sulfide (H₂S) in hydrothermal vents, this study investigates the oxidation mechanisms in mixed hydrogen sulfide/water model complexes. Quantum structures, properties, spectroscopic signatures, and relative energies are presented for the oxidized hydrogen sulfide dimer, [(H₂S)(H₂S)]⁺, and the mixed dimer, [(H₂S)(H₂O)]⁺, using computational quantum chemistry techniques. High-level coupled-cluster approaches are used to provide benchmark references and appropriate density functionals for faster simulations. The mixed dimer is found to exhibit traits intermediate to the limiting regimes of oxidized water (a proton-transferred, ion-radical complex, 𝐻₃𝑂⁺⋯𝑂𝐻) and oxidized hydrogen sulfide (a hemi-bonded complex, 𝐻₂𝑆)₂⁺). These results provide fundamental properties which begin to depict the environment and unique chemistry surrounding hydrothermal vents.