CARBON-MONOXIDE ADSORPTION ON THE (111) AND (110) FACES OF A PT50NI50 SINGLE-CRYSTAL ALLOY

TDS and DELTAphi measurements have been used to study the adsorption of CO at 300 and 120 K on these surfaces in order to probe their chemical and electronic properties. Previous works have shown that the surface composition of this alloy depends on the orientation: strong first layer enrichment in Pt on the (111) face, in Ni on the (110) face. CO is more strongly adsorbed on the (110) than on the (111) surface. However, the initial adsorption kinetics is similar on both surfaces (s0 almost-equal-to 0.6). Upon CO adsorption, DELTAphi only decreases on the Pt-rich (111) face compared to a large increase on the Ni-rich (110) face. The results are discussed in relation with CO adsorption on the respective pure metals: Pt(11) and Ni(110).