Hydrogen adsorption on sulfur and nitrogen covered Ru(001) surfaces

Abstract

Hydrogen adsorption on nitrogen- and sulfur-modified Ru(001) surfaces was investigated using X-ray and ultra-violet photoelectron spectroscopies (XPS and UPS), low-energy electron diffraction (LEED) and thermal desorption spectroscopy (TDS). On a S-covered Ru(001), two thermal desorption peaks of hydrogen at 135 and 265 K were clearly observed at sulfur coverages > 0.1, at which p(2 × 2)-S islands start to form. The intensities of these two peaks increase with θS up to 0.21, and then decrease rapidly at higher sulfur coverages. At θS = 0.33, corresponding to a complete ( 3 × 3)R30° LEED pattern, hydrogen adsorption was fully suppressed. Compared with hydrogen desorption from H2S decomposition on Ru(001), it was concluded that the hydrogen desorption peak at 135 K is correlated with the formation of p(2 × 2)-S unit cells. Our experiments further demonstrate that preadsorbed N-atoms also inhibit the adsorption of hydrogen with each N-adatom blocking four hydrogen adsorption sites. © 1994.