Journal of Power Sources 195 (2010) 3887–3892
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Journal of Power Sources
journal homepage: www.elsevier.com/locate/jpowsour
Novel fabrication of solid-state NaBH
4
/Ru-based catalyst composites for
hydrogen evolution using a high-energy ball-milling process
Cheng-Hong Liu
a
, Bing-Hung Chen
a,∗
, Chan-Li Hsueh
b
, Jie-Ren Ku
b
, Fanghei Tsau
b
a
Department of Chemical Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan
b
New Energy Technology Division, Energy and Environment Research Laboratories, Industrial Technology Research Institute (ITRI), Hsinchu 31040, Taiwan
article info
Article history:
Received 30 September 2009
Received in revised form 4 December 2009
Accepted 17 December 2009
Available online 11 January 2010
Keywords:
Hydrogen generation
Solid-state
Gravimetric hydrogen storage capacity
Catalyst
Sodium borohydride
Hydrated metaborate
abstract
Solid-state NaBH
4
/Ru-based catalyst composites have been fabricated for hydrogen generation through a
high-energy ball-milling process, providing uniform dispersion of resin-supported Ru
3+
catalysts among
pulverized NaBH
4
(SBH) particles, so as to increase the contacts of SBH with active catalytic sites. Conse-
quently, the gravimetric hydrogen storage capacity as high as 7.3wt% could be achieved by utilizing water
as a limiting reagent to overcome the issue of deactivated catalysts whose active sites are often blocked
by precipitates caused by limited NaBO
2
solubility occurring in conventional aqueous SBH systems for
hydrogen productions. Products of hydrolyzed SBH that greatly influence the gravimetric H
2
storage
capacity are found to be most likely NaBO
2
·2H
2
O and NaBO
2
·4H
2
O from SBH/H
2
O reacting systems with
initial weight ratios, SBH/H
2
O = 1/2 and 1/10, respectively, according to the TGA and XRD analyses.
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
To overcome severe problems of global warming and climate
change owing to the excess emission of carbon dioxide resulted
from the combustion of fossil fuels, the development of clean and
renewable energies is of urgent necessity. Among various potential
candidates of green energies, hydrogen is likely one of the promis-
ing alternatives due to the fact that the environmentally benign
product, water, was the main product generated through the reac-
tion with oxygen via a device like proton exchange membrane fuel
cells (PEMFCs) to emit the energy. In addition, almost 80% of the
theoretical power efficiency can be obtained from PEMFCs, which
are generally higher than that from conventional internal com-
bustion engines using fossil fuels as the power source. So far, the
most common industrial process to produce hydrogen is the steam
reforming reaction of hydrocarbon compounds such as natural gas,
methanol and ethanol [1–3]. However, the inevitable presence of
impurities, such as carbon monoxide (CO), contained conjointly in
produced hydrogen via the reforming process dramatically poison
noble metal catalysts used in PEMFCs leading to deactivation of the
fuel cells.
∗
Corresponding author. Tel.: +886 6 275 7575x62695; fax: +886 6 234 4496.
E-mail addresses: bhchen@alumni.rice.edu, bkchen@mail.ncku.edu.tw
(B.-H. Chen).
Recently, several alternative hydrogen storage technologies
have been continuously investigated. These include high-pressure
tanks, metal hydrides, liquefied hydrogen and chemical hydrides
(e.g., KBH
4
, NaBH
4
, and LiH). Among various hydrogen stor-
age methods mentioned above, chemical hydrides have appealed
to most attention because of their higher purity of pro-
duced hydrogen, less energy-loss, more cost-effective and lower
operation-pressure at ambient conditions. Among these chemical
hydrides, sodium borohydride (SBH)—NaBH
4
, is one of the promis-
ing H
2
storage materials, of which H
2
can be easily released through
the hydrolysis reaction in the presence of proper catalysts [4] as
shown in Eq. (1):
NaBH
4
+ 2H
2
O
catalyst
−→ NaBO
2
+ 4H
2
+ 217 kJ (1)
In addition, NaBH
4
can be stably stocked under alkaline environ-
ment [5]. Furthermore, a higher hydrogen content (i.e. 10.8 wt%)
could be obtained theoretically, which could possibly meet the
set 2010 goal of 6 wt% for on-board automotive hydrogen stor-
age declared by the USA Department of Energy (US DOE) [6]. The
reaction rate, namely the rate of hydrogen evolution via NaBH
4
hydrolysis, can be easily regulated through different ways such
as addition of catalysts and introduction of water to the reacting
systems. Various types of catalysts with enhanced performance on
NaBH
4
hydrolysis reaction have been widely investigated in recent
years; among which, supported precious metals such as ruthenium
(Ru) and platinum (Pt) were found to be quite effective [7,8].Inour
previous study, satisfactory performance from polymer supported
0378-7753/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jpowsour.2009.12.087