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

摘要

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 H_2S on the Au{100)-(5 * 20) between 80 and 100 K. The H_2S adsorbs reversibly into a weakly bound physisorbed state, which desorbs at approx 107 K. At 110 K reversible Langmuir adsorption into the precursor state was observed for H_2S on the Au{100}-(5 * 20). The Au{100}-(1 * 1)-SH was prepared by electron irradiation of H_2S 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 H_2S from Au{100}-(1 * 1)-SH and H_2S 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.