Interaction of H 2S with the Ru(001) surface

Abstract

The interaction of sulfur and H 2S with Ru(001) was studied between 350 and 1500 K with LEED, UPS, AES and Thermal Desorption Spectroscopy. Exposure to H 2S at 350 K results first in the formation of a (2 × 2) LEED pattern followed by a (√3 × √3) R30°. Further exposure results in a diffuse c(4 × 2) pattern which sharpens upon heating to 500 K. Quantitative AES indicates that these structures correspond to 1 4 , 1 3 , 1 2 sulfur atom per surface Ru atom, respectively. UPS indicates that H 2S dissociates upon adsorption at 350 K over the entire coverage range. Work function and Thermal Desorption Measurements show that below 1 3 (S/Ru) at 350 K only sulfur is adsorbed, indicating that hydrogen from H 2S recombines and desorbs during the adsorption of sulfur. At higher sulfur coverages hydrogen remains trapped on the surface, but UPS measurements show that the H 2S is dissociated. AES and Thermal Desorption Measurements yield an initial heat of desorption for sulfur of 105 kcal/mole. At coverages approaching saturation, the heat of desorption decreases rapidly to 50 kcal/mole.