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Ch. Rameshan, M. Ling Ng, A. Shavorskiy, J. Newberg, H. Bluhm:
"Water adsorption on polycrystalline vanadium from ultra-high vacuum to ambient relative humidity";
Surface Science, 641 (2015), 141 - 147.

We have studied the reaction of water vapor with a polycrystalline vanadium surface using ambient pressure
X-ray photoelectron spectroscopy (AP-XPS) which allows the investigation of the chemical composition of the
vanadium/water vapor interface at p(H2O) in the Torr range. Water dissociation on the vanadium surface was
studied under isobaric conditions at p(H2O) ranging from 0.01 to 0.50 Torr and temperatures from 625 K to
260 K, i.e. up to a relative humidity (RH) of ~15%. Water vapor exposure leads to oxidation and hydroxylation
of the vanadium foil already at a pressure of 1 × 10−6 Torr at 300 K (RH ~ 4 × 10−6%). The vanadium oxide
layer on the surface has a stoichiometry of V2O3. Initial adsorption of molecular water on the surface is observed
at RH N 0.001%. Above a RH of 0.5% the amount of adsorbedwater increases markedly. Experiments at increasing
temperatures show that the water adsorption process is reversible. Depth profile measurements show a thickness
for the vanadium oxide layer of 3-5 mono layers (ML) and for vanadium hydroxide of 1-1.5 ML over the
whole RH range in the isobar experiments. The thickness of the adsorbed water layer was found to be in the
sub-ML range for the investigated RH's.

Hydroxylation, Ambient pressure photoelectron spectroscopy, Water adsorption, Vanadium, In-situ spectroscopy

http://dx.doi.org/10.1016/j.susc.2015.06.004