AVS 61st International Symposium & Exhibition
    Surface Science Wednesday Sessions
       Session SS+AS-WeM

Paper SS+AS-WeM13
Dimerization Induced Deprotonation of Water on RuO2(110)

Wednesday, November 12, 2014, 12:00 pm, Room 312

Session: Atomistic Modeling of Surface Phenomena
Presenter: Zdenek Dohnalek, Pacific Northwest National Laboratory
Authors: R. Mu, Pacific Northwest National Laboratory
D.C. Cantu, Pacific Northwest National Laboratory
V.-A. Glezakou, Pacific Northwest National Laboratory
Z. Wang, Pacific Northwest National Laboratory
I. Lyubinetsky, Pacific Northwest National Laboratory
R. Rousseau, Pacific Northwest National Laboratory
Z. Dohnalek, Pacific Northwest National Laboratory
Correspondent: Click to Email
RuO2 has proven to be indispensable as a co-catalyst in numerous systems designed for photocatalytic water splitting. Here we present a first mechanistic study of water adsorption, dissociation, and diffusion on the most stable RuO2 surface, rutile RuO2(110). Variable temperature scanning tunneling microscopy (STM) and ab initio molecular dynamics based density functional theory calculations (DFT) are employed to follow the behavior of small water clusters. We show that water monomers adsorb molecularly on Ru sites, become mobile above 240 K, and diffuse along the Ru rows. The monomers readily pair up and form dimers that are immobile below 273 K. Finally, the dimers deprotonate and form Ru-bound H2O-OH and bridging OH species. This is in a sharp contrast with the molecular binding of water dimers observed on isostructural TiO2(110). The onset for diffusion of H2O-OH pairs on RuO2(110) is observed at ~273 K, indicating a significantly higher diffusion barrier than that for water monomers. The experimentally determined diffusion barriers are in agreement with those obtained from the DFT calculations. The diffusion of H2O-OH pairs is found to proceed via a rollover mechanism, with a water molecule moving over OH, followed by hydrogen transfer from H2O to OH. At high water coverages, water dimers are found to be the building blocks of longer water chains on Ru rows. The observed behavior of water monomers and dimers is compared and contrasted with that previously reported on isostructural rutile TiO2(110).