To investigate solvent effects, CO and H-2 adsorption on Cu2O (1 1 1) surface in vacuum, liquid paraffin, methanol and water are studied by using density functional theory (DFT) combined with the conductor-like solvent model (COSMO). When H-2 and CO adsorb on Cu-cus of Cu2O (1 1 1) surface, solvent effects can improve CO and H-2 activation. The H-H bond increases with dielectric constant increasing as H-2 adsorption on O-suf of Cu2O (1 1 1) surface, and the H-H bond breaks in methanol and water. It is also found that both the structural parameters and Mulliken charges are very sensitive to the COSMO solvent model. In summary, the solvent effects have obvious influence on the clean surface of Cu2O ( 1 1 1) and the adsorptive behavior. (C) 2009 Elsevier B. V. All rights reserved.