LOW TEMPERATURE HYDROGEN RELEASE FROM BORONTETRAHYDRIDE-SODALITE AND ITS RELOADING: OBSERVATIONS IN IN-SITU AND EX-SITU TIR EXPERIMENTS

摘要

Temperature dependent infrared (TIR) absorption experiments were used to investigate the mechanism of hydrogen release from borontetrahydride sodalite, Na_9[AlSiO_4]6(BH_4)_2. The release of hydrogen is observed for temperatures between 150 and 450°C as indicated in situ by nitrate reduction. The hydrogen production follows the reaction BH_4~+ + 2 H_2O => BO_2~- + 4H_2 via consecutive intra cage reaction steps. Water molecules are injected from x-ray amorphous hydrosodalite species which are formed simultaneously with the borontetrahydride sodalite during synthesis. The hydrosodalite type species become reloaded with water under normal ambient conditions, which is used to proceed the hydrogen release. A first step for the reloading of hydrogen becomes obvious, too, when the reacted pellets where reheated under hydrogen flowing atmosphere.