Synthesis and Characterization of Metal Hydride/Carbon Aerogel Composites for Hydrogen Storage

Table 1

Fine structural parameters Pd/Ti atoms in Pd/Ti powder standards, 5 wt% Pd-doped carbon aerogels with or without hydrogen reduction, and 20 mol% Ti-NaAlH₄ metal hydride composites analyzed by using EXAFS.

Samples	Shell	CN^a (±0.05)	𝑅^b (±0.02 Å)	σ ^2 (Å^2)^c
Pd species
Pd powder standard	Pd–Pd	9.59	2.74	0.0056
Fresh 5 wt% Pd-doped CAs^d	Pd–O	6.18	2.12	0.0061
H2 reduced 5 wt% Pd-doped CAs^e	Pd–Pd	9.23	2.73	0.0073
Ti species
Metallic Ti standard	Ti–Ti	1.78	2.93	0.0044
TiO standard	Ti–O	2.14	2.53	0.0083
Ti2O3 standard	Ti–O	3.02	2.12	0.0023
Rutile-typed TiO2 standard	Ti–O	4.11	1.94	0.0015
Anatase-typed TiO2 standard	Ti–O	4.15	1.93	0.0026
Ball-milled 20 mol% Ti-NaAlH4	Ti–O	4.07	1.95	0.0048
H2-adsorbed 20 mol% Ti-NaAlH4	Ti–Ti	1.83	2.81	0.0051

aCN denotes “coordination number”;
bR denotes “bond distance”;
cσ denotes “Debye-Waller factor”;
dFresh 5 wt% Pd-doped carbon aroegel samples denote the as-synthesized materials that were oxidized and converted into PdO species instantly in the synthetic processes;
e5 wt% Pd-doped carbon aroegel samples were reduced at 453 K under flowing hydrogen gas for six hours.