Adsorption and desorption of thermally generated hydrogen atoms on Au(111) and Ag/Au(111)

Abstract

To explore the possibility of employing thermally generated H atoms to determine the chemical composition of a metallic surface, we investigated the adsorption and desorption of H atoms generated with a thermal cracker on surfaces Au(111) and Ag/Au(111). Angle-resolved photoemission spectra showed that the noble-metallic surfaces deteriorated upon exposure to a flux of H atoms at ~ 100 K. Upon subsequent annealing, the order of the surfaces was mostly recovered when H atoms on the surfaces desorbed, but the recovery was incomplete even with annealing at a temperature much higher than that at which H atoms desorb. X-ray photoemission spectra showed that O-containing contaminants existed on the surfaces after the H dosing. The evolution of O 1s during annealing indicated that the O-containing contaminants were H 2 O and its moieties generated during thermal cracking; the disturbances of the surfaces remaining above the desorption temperature of H atoms were likely caused by chemisorbed O. Our results show that it is possible to employ thermally generated H atoms to determine the chemical composition of a metallic surface, but a small proportion of H 2 O in a H 2 gas line might be unavoidable; precautions against possible O contamination are required when a thermal cracker is employed. • The noble-metallic surfaces dosed with thermally generated H atoms are studied. • The order of the H-dosed surfaces is not fully recovered after H atoms desorb. • O-containing contaminants are detected on the H-dosed surfaces. • The contaminants are water and its moieties generated with thermal cracking. • Precautions against O contamination are required when a thermal cracker is employed.