CHEMISORPTION OF HYDROGEN ON RHENIUM

Using ultra-high vacuum techniques, the sticking probability for chemisorption of hydrogen on a polycrystalline rhenium wire has been measured as a function of surface coverage in the temperature range 296-460°K. At 296°K the initial sticking probability was 0·24, with saturation at about 6×1014 atoms/cm2, these values decreasing with increasing temperature. Slow desorption experiments revealed two binding states. The high-temperature state was found to obey second-order desorption kinetics with a heat of desorption of 30·5±1 kcal mole -1 and a second-order rate constant of (7·5±3) ×10-4 cm2 per atom per second.