Photoemission studies of water dissociation on rutile TiO2 (1Â 1Â 0): Aspects on experimental procedures and the influence of steps

The composition of the first water layer on the stoichiometric rutile TiO2 (1 1 0) surface was studied with the use of synchrotron radiation photoelectron spectroscopy. The same H2O-OH balance was reached using different preparation procedures and there was no difference between H2O and D2O. On this basis, we rule out the possibility that the partially dissociated layer is an artifact caused by photon irradiation during measurements. Pre-deposition of Au at room temperature, primarily decorating step edges [e.g. S.A. Tenney et al. J. Phys. Chem. C 115 (2011) 11112] decreases the water uptake but does not change the relative amount that dissociates. This implies that the observed H2O-OH balance is not controlled by dissociation at steps and subsequent out-diffusion of hydrogens on the terraces. That is, the formation of a partially dissociated water layer is an inherent property of stoichiometric terraces.