Journal
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
Volume 33, Issue 21, Pages 6195-6200Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.ijhydene.2008.08.019
Keywords
NaAlH4; Hydrogen desorption; TiO2; HfCl4; Co-dopant
Categories
Funding
- Petroleum and Petrochemical College (PPC)
- Research Unit for Petrochemical and Environment Catalysts
- Ratchadapisek Somphot Endowment
- National Science and Technology Development Agency
- Petroleum and Petrochemical Technology Consortium
- Chulalongkorn University
- UOP LLC
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The segregation of bulk Al after the hydrogen desorption may be one of many reasons why there is the incomplete hydrogen re-absorption and the need for higher desorption temperature in subsequent desorption of HfCl4- and TiO2-doped NaAlH4. In this work, we attempted to improve hydrogen storage capacity of 4 mol% HfCl4- and 4 mol% TiO2-doped NaAlH4 by adding a co-dopant (graphite, activated carbon, and MCM-41) using ball milling technique. it was found that the co-dopants significantly affect the hydrogen desorption/re-absorption of the hydride. Results show that the hydrogen re-absorption capacity of HfCl4- and TiO2-doped NaAlH4 added with the co-dopants increases 10-50% as compared with that without a co-dopant, and graphite seems to be the best co-dopant. Moreover, the hydrogen desorption temperature in the subsequent cycle of co-dopant doped samples decreases about 10-15 degrees C compared to the sample without a co-dopant. It could be explained that high porosity and large surface area of the co-dopants would decrease the segregation of bulk Al after the desorption and improve hydrogen diffusion in/out bulk of desorbed/re-absorbed samples. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
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