Biomedical Engineering Reference
In-Depth Information
Regarding porous adsorbents, hydrogen adsorbed increases
with decreasing temperature and increasing pressure. With
increasing pressure, hydrogen adsorption increases linearly up to
a certain pressure, but at higher pressures the increase becomes
gradual and eventually levels off at very high pressures. On the one
hand, more efforts should be focused on improving thermodynamics,
i.e., increasing the adsorption enthalpy rather than merely increasing
pore volume. On the other hand, excess capacity means tighter
packing of hydrogen molecules and implies increased interaction
energy [18]. Regardless of the micropore volume being calculated
by different approaches, there is a linear relationship between the
micropore volume and hydrogen storage capacity of a CA [49].
Further work should be done to form relatively strong hydrogen
adsorbing centers, e.g., incorporating reactive sites into the carbon-
based nanoporous structures by doping nanoscaled metal particles
(as catalysts) or polymerizing unsaturated functionalized complexes
to modify the carbon surface. Thus, high surface area materials with
a large pore volume, hosting polarizing sites/reactive sites to achieve
high hydrogen storage density for adsorbed hydrogen molecules,
can present a promising approach toward more favorable working
conditions.
The experimental results and some of the theoretical predictions
indicate that CAs are promising candidates for hydrogen storage.
However, further efforts have to be made to verify and reproduce
the hydrogen storage capacity in CAs, to correlate the surface area
and pore volume with hydrogen uptake, to elucidate the hydrogen
adsorption/desorption mechanisms, and finally to clarify the
feasibility of CAs as a practical onboard hydrogen storage material.
Acknowledgement
We acknowledge the financial support of the CSIRO Energy
Transformed Flagship National Hydrogen Material Alliance
(NHMA), and the Australian Research Council for ARC Discovery
grant DP0877155, REIF grant R00107962 2001 and LEIF grant
LE0775551, which enabled the SAXS and XRD studies to be
undertaken. We thank the Australian Institute of Nuclear Science
and Engineering (AINSE) for a grant to conduct the NMR experiment,
and also thank the Australian Synchrotron for the FT-IR analysis. The
authors also thank S.B. Wang (Chemical Engineering, Curtin) and
