Abhijit A. Phatak1, Kendall T. Thomson2, W. Nicholas Delgass2, Fabio H. Ribeiro2, and William F. Schneider1. (1) Department of Chemical and Biomolecular Engineering, University of Notre Dame, 182 Fitzpatrick Hall, Notre Dame, IN 46556, (2) School of Chemical Engineering, Purdue University, Forney Hall of Chemical Engineering, 480 Stadium Mall Drive, West Lafayette, IN 47907
We report a periodic self-consistent density functional theory investigation of the adsorption and dissociation of water on (111) surface of Cu, Au, Pt, Pd and Ni. We determined the binding energies, preferred adsorption sites and configurations, and vibrational frequencies for H2O and its dissociation products (OH, H, and O) on these metals. We also examined the thermochemistry and calculated activation energy barriers for steps in the sequential two-step water dissociation. We find that both the dissociation steps are endothermic on Au(111), Pt(111) and Pd(111). Furthermore, first H abstraction from adsorbed H2O is exothermic on Cu(111) and Ni(111). Subsequent OH dissociation is endothermic on Cu(111) and slightly exothermic on Ni(111). Among the metals studied, Cu(111) provides an optimum pathway for H2O dissociation. Using a simple Langmuir equilibrium model, we show that, under typical low temperature water-gas shift conditions, surface coverage of OH is several orders of magnitude higher than that of O.