A computational study on water adsorption on Cu2O(1 1 1) surfaces: The effects of coverage and oxygen defect

Abstract The interaction of water with solid surfaces plays an important role in many chemical reactions. The present work investigates water adsorption on the clean and defective Cu 2 O(1 1 1) surfaces using spin-polarized density functional theory. The results show that at low water coverage, only molecular H 2 O chemisorption is preferred on clean Cu 2 O(1 1 1) surface, and the water adsorption results in surface reconstruction. Up to 1 monolayer (ML), the adsorbed H 2 O molecules interact with the coordinatively unsaturated Cu atoms as well as the coordinatively unsaturated surface oxygen atoms via H-bonding. Up to 2 ML, the adsorbed H 2 O molecules interact with the coordinatively unsaturated surface oxygen atoms and the first layer adsorbed H 2 O molecules via H-bonding. Ordered surface layer structures are observed at 1 and 2 ML H 2 O adsorption. In contrast to the clean surface, the defect surface with oxygen vacancy favors dissociative H 2 O adsorption with the dissociated OH group bridging the surface Cu atoms and the H atom on the coordinatively saturated third layer O atom. The adsorption mechanisms are analyzed on the basis of the total density of states. It is found that wet electron states on the clean and H 2 O adsorbed Cu 2 O(1 1 1) surfaces might be important for their photocatalytic properties. Water adsorption on Cu 2 O surface is stronger than on MgO, Fe 3 O 4 , Fe 2 O 3 and CeO 2 , while weaker than on Al 2 O 3 . The different H 2 O adsorption mechanisms on different metal oxides may benefit for new H 2 O-splitting metal oxides catalyst designing.