Molecular beam study of the adsorption and desorption of hydrogen sulfide on Au{100}

The adsorption and desorption of hydrogen sulfide on clean reconstructed Au{100}-(5×20) and sulfided gold, denoted by Au{100}-(1×1)-SH, has been studied with a combination of temperature programmed desorption (TPD), low energy electron diffraction (LEED), Auger electron spectroscopy (AES), and molecular beam (MB) methods. Precursor-mediated adsorption kinetics were observed for the adsorption of H2S on the Au{100}-(5×20) between 80 and 100 K. The H2S adsorbs reversibly into a weakly bound physisorbed state, which desorbs at ∼107 K. At 110 K reversible Langmuir adsorption into the precursor state was observed for H2S on the Au{100}-(5×20). The Au{100}-(1×1)-SH was prepared by electron irradiation of H2S adsorbed on the Au{100}-(5×20) substrate. In sharp contrast with the precursor adsorption kinetics observed on the clean Au{100}-(5×20) surface, the adsorption kinetics for H2S on the Au{100}-(1×1)-SH exhibited Langmuir adsorption kinetics at 80 K. The TPD of H2S from Au{100}-(1×1)-SH and H2S adsorbed on Au{100}-(1×1)-SH showed additional features at higher temperatures which were associated with the disproportionation of chemisorbed HS(ad). Finally, we have identified a new sulfided gold surface, denoted Au{100}-(2×2)-S which was prepared by annealing the Au{100}-(1×1)-SH to remove adsorbed hydrogen.