ADSORPTION OF NO ON PD(110)

The adsorption of NO on Pd(110) has been studied by RAIRS, TDS and LEED between 180 and 360 K. The vibrational data show complex temperature and coverage dependencies which can only be rationalised by invoking an adsorbate-induced (1 x 3) reconstruction (possibly missing row) which occurs for coverages greater than 0.5 ML at T > 260 K. The formation of this reconstruction is kinetically hindered at 180 K and the system follows a different path in which adsorption occurs on the unreconstructed surface until the highest coverages when a displacive reconstruction of the surface occurs, apparently to facilitate dimer formation. The presence of surface reconstructions coupled with the ambiguity associated with correlating NO stretching frequencies to particular adsorption sites makes the analysis of this system particularly difficult. However, this work supports our earlier work on CO adsorption and clearly emphasises the vulnerability of the Pd(110) surface to adsorbate-induced reconstruction. This behaviour contrasts with that observed on other fcc {110} surfaces where adsorbates are implicated in lifting reconstructions.