CO adsorption on (100) and (211) tungsten single-crystal surfaces: Changes in work function

The adsorption of CO on two large single crystals of tungsten exposing (100) and (211) surfaces has been studied by measuring changes in the work function [Formula: see text] at 300 °K and above, where some CO remained adsorbed. The results for the two surfaces were quite different.CO adsorbed on the clean W(100) surface at room temperature as β-CO causing [Formula: see text] to increase by 0.48 V. As β adsorption saturated, α-CO adsorption began and caused [Formula: see text] to decrease. The major effect of heating was desorption.CO adsorbed on the clean W(211) surface with a sticking probability near unity and increased [Formula: see text] by 0.68 V. Heating the crystal to temperatures below 1100 °K produced large irreversible changes in [Formula: see text]. These irreversible changes are attributed to the formation and dissociation on the surface of complexes consisting of two CO molecules.