Boron K-edge NEXAFS Study Of Novel Hydrogen Storage Materials

JOSE MARTIN RAMALLO LOPEZ; FÉLIX GREGORIO REQUEJO; KARINA SUÁREZ ALCÁNTARA; IVAN SALDAN; JOSÉ M. BELLOSTA VON COLBE; MARTIN DORNHEIM; TORBEN R. JENSEN; BO RICHTER; LINE H. RUDE; JOSÉ AVILA; MARÍA CARMEN ASENSIO

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Workshop; Soleil Users Meeting 10; 2010

Soleil Synchrotron

In this work we present the first NEXAFS results obtained at the Antares beamline of the SOLEIL synchrotron for Light Metal Hydrides characterization. We have successfully established a protocol to transfer the samples from a dry box to the beamline chamber without taking contact with air. We have studied by NEXAFS spectroscopy at the Boron-K edge reactive hydride composites (RHCs) based on calcium and lithium: mixtures of, for instance, Ca(BH4)2 and MgF2, ball milled and subjected to several cycles of hydrogenation-dehydrogenation to obtain a partial substitution of the hydrogen by fluorine atoms, thereby changing the thermodynamics of the compounds. We show here that boron K-NEXAFS is a suitable probe to follow the structural changes produced in the materials by the absorption and desorption of hydrogen. We discuss the effect of the fluorine substitution on the electronic structure seen on NEXAFS spectra. We could also determine the different stability of each composite from their different NEXAFS spectra variation with time taken in UHV conditions.