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Hydrogen adsorption on functionalized nanoporous activated carbons.
X B Zhao1, B Xiao, A J Fletcher
1Northern Carbon Research Laboratories, School of Natural Sciences, Bedson Building, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, UK.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Hydrogen storage in porous carbons is temperature-dependent, with optimal adsorption occurring at low temperatures. Functional groups slightly hinder hydrogen uptake, impacting energy applications.
Area of Science:
- Materials Science
- Physical Chemistry
- Chemical Engineering
Background:
- Hydrogen adsorption on carbon materials is crucial for energy storage applications.
- Understanding the influence of carbon properties on hydrogen uptake is vital.
Purpose of the Study:
- To systematically investigate the impact of functional groups and porous structure on hydrogen adsorption in porous carbons.
- To determine the thermodynamic properties of hydrogen adsorption and their relation to storage limitations.
Main Methods:
- Preparation of porous carbons with varying nitrogen and oxygen functional groups.
- Characterization of porous structures using nitrogen and carbon dioxide adsorption.
- Measurement of hydrogen adsorption isotherms at 77 K and 100 kPa.
- Determination of adsorption enthalpies using virial and van't Hoff equations.
Main Results:
- Hydrogen adsorption isotherms were Type I (IUPAC classification).
- Adsorption is highly temperature-dependent, with minimal uptake above 195 K.
- Isosteric enthalpies of adsorption ranged from 3.9-5.2 kJ mol⁻¹.
- Maximum hydrogen uptake correlated with micropore volume.
Conclusions:
- Porous carbon structure, particularly micropore volume, is key for hydrogen adsorption capacity.
- Functional groups have a minor negative effect on hydrogen adsorption.
- Thermodynamics indicate significant temperature limitations for practical hydrogen storage.