Small hydrocarbon adsorbates on SnO2(1 1 0) surfaces: Density functional theory study

Adsorption of three small hydrocarbons molecules (acetylene, ethylene and ethane) on two SnO2(1 1 0) surfaces is studied by employing density functional theory calculations, slab model and linear combination of atomic orbitals (LCAO) approach. Acetylene and ethylene adsorb preferentially on top of a 5-fold tin atom, while ethane aligns itself with the rows of bridging oxygens and settles between two surface tin atoms. Adsorption energies and changes occurring in the structural characteristics and electronic structure of both the hydrocarbons and SnO2 surface indicate chemisorption of unsaturated hydrocarbons and physisorption of ethane on reduced surfaces. In all cases of chemisorption there are two contributing mechanisms: charge transfer creating ionic bonding (down-shift of levels) and covalent bonding (broadening of levels).