Role of O-H bonding in catalytic activity of Nb_2O_5 during the course of dehydrogenation of MgH_2

摘要

The hydrogen desorption reaction of MgH_2, MgH_2 → Mg + H_2, is accelerated by the addition of metal oxide catalysts (e.g., Nb_2O_5). From our theoretical calculation of electronic structure, it was predicted that the catalytic activities of metal oxides are related closely to the O-H interaction operating at the interface between oxide catalyst and MgH_2. In this study, the O-H vibration on the Nb_2O_5-catalyzed MgH_2 was investigated experimentally using FTIR spectroscopy. The broad absorption band due to the O-H stretching mode was observed in the region of 2,800-3,600 cm~(-1) in the FTIR spectra of the specimens when hydrogen desorption reaction was in progress. The absorbance of the band decreased monotonously with decreasing hydrogen content in the specimen during the course of dehydrogenation of MgH_2. This experimental result was in agreement with our prediction for the existence of O-H interaction in the hydrogen desorption process.