HYDROGEN SPECIES AND ANIONIC VACANCIES ON HETEROPOLYCOMPOUNDS CATALYTIC HYDROGEN RESERVOIRS

A dynamic method of titration is used to provide evidence for reactive hydrogen (H) present in different heteropolycompounds (HPC), This me thod of titration involves hydrogenation of 2-methylbuta-1,3-diene (is oprene) under helium flow in the absence of gaseous hydrogen and permi ts to reveal and titrate reactive hydrogen species (H) that a solid i s able to store, The heteropolycompounds are catalytic hydrogen reserv oirs with marked diffusion properties for hydrogen species (H, OH-). The hydrogen reservoir capacity depends on the pretreatment temperatur e under H-2, which has been shown to correspond to the creation of ani onic vacancies in the solid by the loss of H2O. In the conditions in w hich the incorporation of hydrogen in the solids occurs, in-situ X-ray diffraction analysis under H-2 show shifts, depending on the treatmen t temperature and corresponding to a lattice expansion attributed main ly to the insertion of hydrogen species of hydridic nature in the anio nic vacancies. (C) 1998 Academic Press.