Tcq. Noakes et al., Pd/Cu alloys as hydrodechlorination catalysts: a medium-energy ion scattering study of surface composition under exposure to chlorinated hydrocarbons, SURF INT AN, 30(1), 2000, pp. 81-84
Medium-energy ion scattering (MEIS) is a surface analytical technique with
the unique ability to provide layer-by-layer compositional information for
crystalline materials such as the bimetallic PdCu alloy investigated here.
MEIS has been used to study the segregation effects induced by the adsorpti
on of trichloroethene onto a Pd0.5Cu0.5(110) single crystal; this system is
a model for industrially important hydrodechlorination catalysts. The PdCu
(110) clean surface is shown to be slightly Pd-rich under the preparation
conditions used, with oscillatory composition going into the bulk. Adsorpti
on of trichloroethene caused Cu enrichment of the first atomic layer, altho
ugh this is seen to decrease with higher temperature annealing, Comparable
experiments using ethene indicate that adsorbed carbon and hydrocarbon spec
ies can give rise to considerable Pd segregation. The chemistry of trichlor
oethene adsorption on PdCu(110) is such that considerable residual carbon a
nd hydrocarbons may be present and, because this induces an opposing effect
, it is probable that the effect of adsorbed Cl on Cu segregation is larger
than that observed directly, Copyright (C) 2000 John Wiley & Sons, Ltd.