HYDROGEN ADSORPTION AND THE TRANSFORMATION OF THE PT(100) SURFACE-STRUCTURE

The adsorption of hydrogen on a Pt(100) single crystal face was studied at temperatures down to 160 K by line of sight desorption mass spectrometry and LEED. The surface concentrations were calibrated by a procedure based on the dissociative adsorption of hydrogen chloride. Adsorption and desorption were studied on the reconstructed Pt(100)-hex-rot structure, on the (1 x 1)-like termed structure formed on adsorbing hydrogen, and under the conditions of the simultaneously occurring substrate structure transformation. The hex-rot/(1 x 1)-like structure transformation resembles a first-order phase transition which starts at a minimal concentration near 2.8 x 10(14) H atoms/cm2. Binding energies of adsorbed hydrogen atoms differ distinctly for both substrate structures. Adsorption isotherms are reported for the reconstructed hex-rot surface in a limited range of pressures and temperatures.