THE ADSORPTION OF HYDROGEN-SULFIDE ON CLEAN AND SULFIDED AU(110)

The adsorption of H2S on clean and partially sulfided Au(110) surface has been investigated via temperature-programmed desorption. H2S adsorbs with unit sticking probability on the clean surface at 105 K up to completion of the monolayer. Adsorption is almost entirely molecular: when a monolayer of H2S is adsorbed onto a clean Au(110) surface in the absence of incident electrons only about 2% of a monolayer of sulfur remains after desorption of H2S. H2S desorbs from molecular adsorption states at 130 K, 155 K, 180-200 K and 220 K. Adsorbed H2S is extremely sensitive to electron irradiation and decomposes to adsorbed SH groups and adsorbed hydrogen. Recombinative desorption of H-2 occurs at about 215 K, while the adsorbed SH groups disproportionate above about 270 K to form gaseous H2S and adsorbed sulfur. On partially sulfided surfaces H2S still adsorbs with unit sticking probability. Adsorbed H2S reacts with adsorbed sulfur to form adsorbed SH groups which again disproportionate above 270 K.