J. Phys. Chem. C 2008, 112, 8301–8303
8301
Electronic Structure of Monomeric Water Adsorption on Ni{111}: Beyond the General Model Jibiao Li,† Shenglong Zhu,† Ying Li,† Emeka E. Oguzie,‡ and Fuhui Wang*,† State Key Laboratory for Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, 62 Wencui Rd., Shenyang 111116, China, and Electrochemistry and Materials Science Research Laboratory, Department of Chemistry, Federal UniVersity of Technology Owerri, PMB 1526, Owerri, Nigeria ReceiVed: December 25, 2007; ReVised Manuscript ReceiVed: March 25, 2008
The adsorption of an H2O molecule on Ni{111} has been investigated by density functional theory (DFT) calculations. In addition to the consensus between previously reported experimental data and our DFT results arrived at via the surface relaxation pattern, the electron work function and energy levels of a free H2O, as well as the adsorption energy, we have further presented a previously unrecognized electronic picture for the stable on-top adsorption, by analysis of projected density of states. We have provided clear evidence that the Ni 3p orbitals (pz and py), specifically the hybrid orbitals: 3pz -2pz, 3py-2pz, 3pz -2py, and 3py-2py, play crucial roles in the water bonding at the surface. Our results thus offer a new and inclusive understanding of the electronic nature, which is beyond the conventional model of 3a1-3pz and 3a1-3py interactions. Introduction decades,1,2
water adsorption on During the last several metals has been widely investigated owing to its relevance in surface processes such as electrolysis, heterogeneous catalysis, and metal corrosion. Driven by recent advances in fuel cell technology, for instance, adsorption of water on welldefined transition metal surfaces (e.g., Pt,3 Ru,4 and Pd5), particularly on Ni{111}, has provided some useful insight in understanding water-metal interactions. H2O adsorption on nickel surfaces (including water clusters, 6–8 water multilayers,9 and H2O/Ni{111} interfaces10,11) has been investigated using various experimental techniques including infrared reflection adsorption spectroscopy (IRAS), thermal desorption spectroscopy (TDS), low-energy electron diffraction (LEED), Auger electron spectroscopy (AES). By means of IRAS, Nakamura and Ito7 observed on-top adsorption of water monomers on Ni{111} at a low coverage (
