Transcript 2008 - NanoCOFC

Questions and Answers on NANOCOFC
 Progressing with the NANOCOFC project,
new Science and Technology are under
establishment. Accompanying with the
project frequently Questions database is
needed. The NANOCOFC project website
http://www.ket.kth.se/nanocofc/
opens a special window for
Continuous Q & A on concerned
Subjects.
Why, What and How?
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NANOCOFC?
NANOCOFC science?
NANOCOFC Technology?
Importance and significance?
Problems can solved?
To be continued…..
Answers
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The challenges facing the Solid Oxide Fuel Cells (SOFCs) are critical where the materials
cause the key issue. An electrolyte conductivity of 0.1 S/cm is a basic requirement for
high performance. The current SOFC materials based on single-phase material (SPM),
e.g. YSZ (yttrium stabilized zirconia) and SDC (samarium doped ceria) cannot meet this
demand below 600ºC due to its structural limits. Designing and development of functional
materials at low enough temperature to be technical useful is a critical challenge. A new
approach is proposed of designing and developing superionic conduction/tor (SIC) for
low temperature SOFCs by constructing interfaces that may act as “SIC highways” in a
two-phase material (TPMs). The concept is to develop nanocomposite TPMs with
interfacial SIC and dual H+/O2- conductors instead of SPMs and bulk oxygen ion
conduction in SOFCs. It can enhance and improve greatly material conductivity, electrode
dynamics and FC performances at 300-600ºC.
NANOCOFC is currently ongoing EC FP6 SSA project Acronym. Two-fold meanings: i)
from scientific perspective: Multi-functional nanocomposites for advanced fuel cell
technology; ii) from cooperation it means EU-China and EU-Turkey cooperation.
The NANOCOFC approaches are significantly different from conventional approaches
with unique advantages. The long term innovations concern: i) multifunctional
nanocomposites in TPMs to replace the conventional SOFC SPMs; ii) interfaces
determined SIC to replace the bulk oxygen ion conduction mechanism; iii) dual proton
and oxygen ion conduction to enhance the power output compared to current FC singleion process; iv) new generation technology for advanced 300-600°C SOFCs.
Multi-solutions to realize the current fuel cell
technology and commercialization challenges
Such as:
 i) NANOCOFC approach has succeeded in developing and synthesizing new
SOFC electrolyte materials which are able to provide the oxygen and proton
conductivity of 0.1 S/cm at 300C same as YSZ at 1000C. This opens and
guarantees excellent 300-600 C SOFC technology.
 ii) sealing materials is a crucial challenge and barrier to hind the SOFC
technology to commercialization. The NANOCOFC approach can provide
technology and possibility for LTSOFCs operated below 500C. The operation
below 500C can avoid sealing material problem by using the existing hi-T
plastic type materials as the sealing materials, compared to the PEMFC using
the rubber for the sealing.
 iii) Latest developments on extremely low cost electrolyte material, industrial
grade rare-earth mixed carbonates used successfully in LTSOFCs, explored by
a granted Swedish patent (Bin Zhu) and ongoing publication (B. Zhu, X.R. Liu,
Z.G. Zhu, R. Ljungberg, Solid oxide fuel cell (SOFC) using industrial grade
mixed rare-earth oxide electrolytes) on Int. J of Hydrogen Energy (the paper is
also downloaded on NANOCOFC website http://www.ket.kth.se/nanocofc/) has
released a great opportunity to manufacture LTSOFC in extremely costeffective level that no any other exiting fuel cell technology can be competed.
NANOCOFC Science pieces
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Interfaces: as pointed out by Schober: “Obviously, the present results present no proof of superionic
transitions occurring in the interfacial regions or phases, but they are a strong indication of such
events. Proof can only be obtained from scattering or diffraction experiments. These may be trivial, as
the boundary phase volume presumably is small”. We have recently made successes by employing
high resolution TEM equipment to directly determined the interfaces in KTH (P1) two joint partners
from Bin Zhu and Prof. Muhammed, and also KTH/Oxford Univ. the later was reported at SOFC
workshop and NANOCOFC 3rd meeting in Nidge, 1, Nov. 2007. Based on these new discoveries and
experimental evidences,
Bulk and Interfacial mechanism Oxygen ionic conduction has been known more than 100 years and
studies of doping and the vacancy mechanism for oxygen ion transport, i.e., bulk effects; the O2conduction by cation doping with lower valence ions compared to the host cation, so called aliovalent
doping, in order to create oxygen vacancies and thus increase the number of charge carriers in the
crystal, e.g. by yttrium doping in YSZ or samarium doping of ceria (SDC). Such bulk mechanism can
not create high conductivity at low temperature because the mobility of the O2- via vacancies is
thermally activated and requires a high temperature. On the other hand, the interfacial mechanism
creates ionic high ways and superionic conductions by the interfaces between the constituent phases.
Recent theoretical work in a joint effort between KTH and Chalmers Univ. of Tech. Prof. Mellander
(associated partner to the NANOCOFC) revealed the interfacial superionic conduction activation
energy below 0.2 eV, well qualified by the superionic conduction (B. Zhu, S. Li, B.-E. Melander,
Theoretical approach on ceria-based two-phase electrolytes for low temperature (300-600ºC) SOFCs",
Electrochem. Commun. 10 (2008) 302), also KTH first successfully synthesised the sueprionic
conducting materials based on ceria-carbonate two-phase nanocomposites with an ionic conductivity
of 0.1 S/cm at 300C being comparable with that of the YSZ at 1000C.