Characterization and Hydrogen Storage of Surface-Modified Multiwalled Carbon Nanotubes for Fuel Cell Application

Table 2

Fine structural parameters of Ni, Co, Pd or PdCl₂ powder standard, catalyst precursor residues, and non-surface- or surface-modified 5 wt% MWCNTs with hydrogen reduction analyzed using EXAFS technique.

Samples	Shell	CN^a (±0.05)	𝑅^b (±0.05 Å)	𝜎^2 (Å^2)^c
Nickel powder standard	Ni–Ni	3.01	2.43	0.0087
Catalyst precursor residue (Ni)	Ni–Ni	2.92	2.48	0.0058
Cobalt powder standard	Co–Co	6.02	2.45	0.0046
Catalyst precursor residue (Co)	Co–Co	5.96	2.49	0.0067
Pd powder standard	Pd–Pd	9.21	2.76	0.0058
PdCl2 powder standard	Pd–Cl	2.13	2.25	0.0042
NHR 5 wt% Pd-doped MWCNTs^d	Pd–Pd	8.98	2.80	0.0112
HR 5 wt% Pd-doped MWCNTs^e	Pd–Pd	9.08	2.78	0.0093

^aCN denotes “coordination number”;
^bR denotes “bond distance”;
^cσ denotes “Debye-Waller factor”;
^dNHR 5 wt% Pd-doped MWCNTs denotes “as-synthesized non-surface-modified 5 wt% multiwalled carbon nanotubes reduced at 453 K under flowing hydrogen gas for 6 h”;
^eHR 5 wt% Pd-doped MWCNTs denotes “as-synthesized surface-modified 5 wt% multiwalled carbon nanotubes reduced at 453 K under flowing hydrogen gas for 6 h”.