Impact of the Reconstruction of Gold Particles on the Heats of Adsorption of Linear CO Species Adsorbed on the Au Sites of a 1% Au/Al2O3 Catalyst

Abstract

The adsorption of CO at 300 K on a reduced (H2, 713 K) 1% Au/Al2O3 solid leads to the formation of a linear CO species adsorbed on the Au particles (denoted L1) characterized by an IR band at 2098 cm−1 that slightly shifts to higher wavenumbers with the decrease in the coverage. For adsorption pressures Pa > 5 kPa, it is shown that there is a progressive reconstruction of the Au surface with the increase in the duration of the adsorption ta leading to the disappearance of the Au sites associated with the L1 CO species and to the formation of new Au sites forming a linear CO species (denoted L2) characterized by an IR band at 2070 cm−1. The heats of adsorption of the two adsorbed species are determined as the function of their respective coverages by using the adsorption equilibrium infrared spectroscopy procedure previously developed. It is shown that they linearly decrease with the increase in their coverages from 62 to 43 kJ/mol for the L1 and from 100 to 50 kJ/mol for the L2 CO species at coverages 0 a...