DISSOCIATIVE ADSORPTION OF HYDROGEN ON CU(100) AT LOW-TEMPERATURES

The thermal dissociative sticking coefficient of H-2 and D2 on Cu(100) was determined by the use of TPD after exposure to H-2/D2 pressures of 2 x 10(-3) to 5 bar in the temperature range of 218-258 K. The activation energy is determined to 48 and 56 kJ mol-1 for H-2 and D2, respectively. An isotope effect in absolute magnitude was observed. It is found that vibrational energy plays an important role in overcoming the barrier to dissociation. By exposing the crystal at temperatures of 450-600 K, it was found by TPD that hydrogen diffuses into the bulk.