| Abstract
| - Density functional theory (DFT) calculations are performed to study the ethanol adsorption on Rh(111) surfaces.Various adsorption modes, including monomer, dimer, and one-dimensional (1D) chain, are investigated andanalyzed in details from energetic, geometrical, vibrational, and electronic points of view, which lead tovaluable insights into alcohol molecules adsorption on metal surfaces. It is found that ethanol moleculesprefer to adsorb at atop sites and bind to the surfaces through the oxygen atom, independent of the coverageand adsorption modes. The adsorption is exothermic, and the average adsorption energy is −0.5 eV permolecule. Adsorbed ethanol molecules are energetically favorable to agglomerate to dimer and chain byformation of the hydrogen bond. The ethanol adsorption induces significant red shift of the hydroxyl stretchingvibration (ν(OH)). It is found that the red shifts are very sensitive to the coverage and adsorption modes.Depending on the nature of the H-bond, be it H-acceptor or H-donor sharing, there is a distinct pair of ν(OH)vibration, which can be seen as the fingerprint of the existence of hydroxyl-contained molecules and theformation of the H-bond. Our results show that the interaction between adsorbate and substrate and theH-bonding between adsorbed ethanol molecules can result in the overall red shift of ν(OH) to the magnitudeof 769 cm-1.
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