Sulfide and\nHydrogen Bond Networks in the Electric\nDouble Layer: Key Factors for Titanium Passivation Film Stability

Hydrogen sulfide (H<sub>2</sub>S), carbonyl sulfide (COS),\nand\ndimethyl sulfide (DMS) are the primary sulfur compounds found in seawater,\nwhich cause pitting corrosion on the oxide passivation film of titanium,\nknown as “the marine metals”. In this study, density\nfunctional theory (DFT) was used to analyze the adsorption and surface\nelectronic properties of these three small molecules on the anatase\nTiO<sub>2</sub>(101) surface. The analysis was conducted through adsorption\nenergy, work function, Mulliken charge population, and density of\nstates (DOS). The hydrogen bond network structure of the electric\ndouble layer (EDL) was studied for these small-molecule systems using\nab initio molecular dynamics (AIMD). The optimal adsorption configurations\nfor H<sub>2</sub>S, COS, and DMS on the anatase TiO<sub>2</sub>(101)\nsurface are 2O<sub>b</sub>-vertical, O-down-vertical, and O<sub>b</sub>-parallel, with adsorption energies of −1.32, −0.67,\nand −1.86 eV, respectively. The surface charge transfer was\nalso investigated. Through comparative AIMD simulations of three different\naqueous solutions on the TiO<sub>2</sub>(101) surface, we observed\nthat COS exerts a more pronounced influence on the electrical double\nlayer within 3.00 Å of the TiO<sub>2</sub>(101) surface. Specifically,\nthe hydrogen atoms of water tend to aggregate toward the O<sub>b</sub> atoms, forming hydrogen bonds, which significantly impacts the corrosion\nresistance of the TiO<sub>2</sub> surface.