CO and O2 adsorption on the Re/Pt(111) surface studied by photoemission and thermal desorption.

Abstract

Re, mostly in the submonolayer regime, has been grown on a Pt(111) surface. The adsorption of O2 and CO on this system has been studied by high resolution photoelectron spectroscopy and temperature programmed desorption. For low Re coverages O2 adsorption results in the formation of surface oxides, mostly with ReO stoichiometry. For increasing Re coverages the preference changes towards lower oxidation states (possibly ReO1/3 and ReO2/3). On surface alloys, created by annealing Re films above 1000K, the Re photoemission signal is unaffected by O2 adsorption. CO adsorbed on Re islands on Pt(111) desorbs at ∼100K higher temperature compared with CO/Re(0001). On Re–Pt(111) surface alloys the desorption temperature is lowered with increasing Re concentration, by up to ∼100K compared with CO/Pt(111). We suggest an explanation for this in terms of altered 5d→2π∗ back donation.