Unraveling Surface Chemistry of SnO2 Through Formation of Charged Oxygen Species and Oxygen Vacancies

The ability of SnO₂ surfaces to adsorb and activate oxygen species is essential for designing high-performance gas sensors and catalytic materials. In this study, density functional theory (DFT) calculations are employed to unravel the mechanisms governing oxygen adsorption on SnO₂ (110) surfaces under varying surface conditions, including reduced, defective, and stoichiometric configurations. Our findings indicate various forms of charged oxygen species on the surface. The study reveals the presence of $O_2^{2-}$, $O_2^{-}$, and $O^{2-}$ on the reduced surface and $O_2^{2-}$, $O^{-}$, and $O^{2-}$ on the defective and the oxidized surfaces. These charged species are directly linked to the reactivity and sensitivity of SnO₂-based materials, as they interact with oxygen vacancies to stabilize adsorption configurations and influence electronic states within the band gap. PDOS analyses highlight the electronic interactions between adsorbed oxygen species and surface tin atoms, revealing the formation of hybridized orbitals that contribute to defect states near the Fermi level. These states play an important role in determining the surface reactivity and electronic properties of the material. The interplay between oxygen adsorption and vacancy-induced charge redistribution provides critical insights into the mechanisms driving surface reactivity and performance. By providing a detailed understanding of the electronic and energetic properties of adsorbed oxygen species, this work establishes a theoretical framework for the design and optimization of metal oxide-based materials. The findings are particularly valuable for tailoring the properties of SnO₂, In₂O3, and ZnO for applications in gas sensing, catalysis, and related technologies.