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Title: Dynamic in-situ X-ray Diffraction of Catalyzed Alanates

The discovery that hydrogen can be reversible absorbed and desorbed from NaAlH{sub 4} by the addition of catalysts has created an entirely new prospect for lightweight hydrogen storage. NaAlH{sub 4} releases hydrogen through the following set of decomposition reactions: NaAlH{sub 4} {r_arrow} 1/3({alpha}-Na{sub 3}AlH{sub 6}) + 2/3Al + H{sub 2} {r_arrow} NaH + Al + 3/2H{sub 2}. These decomposition reactions as well as the reverse recombination reactions were directly observed using time-resolved in-situ x-ray powder diffraction. These measurements were performed under conditions similar to those found in PEM fuel cell operations (hydrogen absorption: 50--70 C, 10--15 bar Hz, hydrogen resorption: 80--110 C, 5--100 mbar H{sub 2}). Catalyst doping was found to dramatically improve kinetics under these conditions. In this study, the alanate was doped with a catalyst by dry ball-milling NaAlH{sub 4} with 2 mol.% solid TiCl{sub 3}. X-ray diffraction clearly showed that TiCl{sub 3} reacts with NaAlH{sub 4} to form NaCl during the doping process. Partial desorption of NaAlH{sub 4} was even observed to occur during the catalyst doping process.
Authors:
; ;
Publication Date:
OSTI Identifier:
769323
Report Number(s):
SAND2000-8899C
TRN: AH200105%%247
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Conference title not supplied, Conference location not supplied, Conference dates not supplied; Other Information: PBD: 1 Nov 2000
Research Org:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org:
US Department of Energy (US)
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 30 DIRECT ENERGY CONVERSION; ABSORPTION; CATALYSTS; DESORPTION; DIFFRACTION; FUEL CELLS; HYDROGEN; HYDROGEN STORAGE; KINETICS; RECOMBINATION; X-RAY DIFFRACTION