Res. Chem. Intermed.
, Vol. 32, No. 5–6, pp. 431–436 (2006)
Also available online - www.vsppub.com
Systematic investigation of hydrogen storage properties in
-H (R = rare earth) systems
and NOBUHIRO KURIYAMA
Research Institute for Ubiquitous Energy Devices, National Institute of Advanced Industrial
Science and Technology (AIST), Ikeda, Osaka 563-8577, Japan
New Energy and Industrial Technology Development Organization, Kawasaki, Kanagawa
Received 22 November 2004; accepted 24 November 2004
Abstract—We investigated hydrogen storage properties in RNi
-H (R = rare earth) systems.
Pressure–composition isotherms showed that a single pressure plateau separates into two plateaus
(lower and higher plateau) as the atomic number of R element in RNi
-H systems increases, indicating
the presence of two hydrides. In higher-number RNi
-H systems, both plateaus disappear, while
another pressure plateau related to a novel hydride appears at low hydrogen content. The decrease of
the unit cell volume due to the lanthanide contraction leads to the instability of hydrogen, suggesting
an increase in both the lower and higher plateau pressures.
Keywords: Hydrogen storage; rare earth-Ni
-H systems; pressure–composition isotherm.
is one of the most representative hydrogen storage materials because of its
promising hydrogen storage properties at moderate conditions . In a LaNi
system, the pressure–composition (P–C) isotherm shows a single pressure plateau
corresponding to the phase transition between LaNi
solid solution and LaNi
hydride. This is attractive for electrochemical hydrogen storage in rechargeable
metal hydride electrodes .
With respect to other rare earth-based binary RNi
(R = rare earth) alloys, the P–C
isotherms in PrNi
-H and NdNi
-H systems have been shown to have two pressure
plateaus [3, 4]. No P–C isotherms in other RNi
-H systems having a high pressure
plateau have been clariﬁed yet. Indeed, most of the hydrogen storage properties
reported until now have been focused on the lighter rare-earth-based RNi
order to remain within a plateau pressure of 5 MPa.
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