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

Table 3

Specific BET surface area and total pore volumes of nonsurface- or surface-modified MWCNTs and 5 wt% Pd-doped MWCNTs using H₂SO₄/HNO₃ (ratio = 3) reflux for 1 h at 393 K.

Samples	BET surface area (m^2 g^−1)	Total pore volume  (cm^3 g^−1)
Non-surface-modified MWCNTs	79.4	0.18
Surface-modified MWCNTs	114.2	0.32
NHR 5 wt% Pd-doped MWCNTs^a	89.4	0.24
HR 5 wt% Pd-doped MWCNTs^b	128.6	0.38

^aNHR 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”.
^bHR 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”.