ceramic nanocomposites in solid oxide fuel cells (sofc)
DESCRIPTION
Ceramic nanocomposites in solid oxide fuel cells (SOFC) like YSZ, CeO2 (ceria)-SDC used as electrolytes, anodes and cathodes.TRANSCRIPT
Ceramic nanocomposites in solid oxide fuel cells
Term paper presentation for the course of
Composite Materials
Metallurgical and Materials Engineering
IIT Kharagpur
SOLID OXIDE FUEL CELLS
• Electrolyte is in solid state• Anode reaction:
H2 + O2- H2O + 2e-
• Cathode reaction:
1/2 O2+ 2e-O2-
overall reaction:H2 + 1/2 O2 H2O
Advantages:• High energy efficiency and low
emission• No need for precious metal• High tolerance to impurities
SOFC COMPONENTS
Challenges:•High temperature: YSZ based SOFC has an operating temperature of 1000C•Utilization of H2: High production cost
LOWERING OPERATION TEMPERATURE: COMPOSITE ELECTROLYTES
A composite electrolyte is a multiphase membrane made of two or more components to achieve an enhancement of the overall ionic conductivity
conductivities of SDC–(Li 0.435 Na 0.315 K
0.25 )2 CO3 composite
electrolytes
(□) SDC (samarium doped ceria)(○) SDC–10 wt.% carbonate(Δ) SDC–30 wt.% carbonate(∇) SDC–50 wt.% carbonate
LTSOFC (300-600C) can be achieved with nanocomposite materials
SDC-Na2Co3 ELECTROLYTE
• core–shell nanocomposite material prepared by coprecipitation
• SDC core and amorphous Na2CO3 shell in nanoscale
• applied as electrolyte in low-temperature SOFC
• Peaks observed for CeO2• Peaks absent for Na2CO3
Faceted irregular shaped particles <100nm
SDC-Na2Co3 ELECTROLYTE
(a): TEM imageuniform Na2CO3 thin layer of 4–6 nm
(b): HRTEM imageCore and shell interface.
Na2CO3 layer (4–6 nm)
SDC-Na2Co3 ELECTROLYTE
SDC-Na2Co3 ELECTROLYTE
• H+conductivity is 1–2 orders of magnitude higher than the O2− conductivity.
• Amorphous nature of Na2CO3 provides disorder at high temperature facilitating higher charge transfer.
simultaneous H+ and O2− conduction @ 300 oC
DUAL ION CONDUCTION
• The interface supplies high conductive path for proton
• Oxygen ions transported through SDC grain interiors.
MULTI-ION FLOW
NANOCOMPOSITE ELECTRODES
Function of anode :
1.Catalyse electrochemical oxidation of fuel
2.transfer the released charges to a current collector.
These electrode reactions can only occur at the oxide-ion conductor/electronic conductor/gas three-phase boundary (TPB)
CuZn-NSDC ANODE
• fine particle size distribution (50–100 nm)
• adequate porosity• well-connected Cu
and Zn.• Enhanced
electronic conductivity.
• SDC-Na2CO3 as main oxygen ion conductor.
CuZn-NSDC ANODE
Hexagonal Zn (10 nm)
Hexagonal Zn atoms mixed with 5 nm Cu particles.
Interconnected anode structure enhances diffusion.
CONCLUSIONS
• Use of SOFCS at low temperatures is possible with nanocomposite materials which provide higher conduction.
• for commercialization of this environment friendly technology, development of cheaper materials for electrolyte and electrode is imperative.
• Use of crude hydrocarbon fuel is possible with SDC-carbonate.
REFERENCES
• Rizwan Raza , Xiaodi Wang, Ying Ma, Bin Zhu, A nanostructure anode (Cu0.2Zn0.8) for low-temperature solid oxide fuel cell at 400–600 °C, Journal of Power Sources,Volume 195, Issue 24, 15 December 2010, Pages 8067–8070
• Xiaodi Wanga, Ying Maa, Shanghua Li a, Abdel-Hady Kashyoutb, Bin Zhuc, Mamoun Muhammeda, Ceria-based nanocomposite with simultaneous proton and oxygen ion conductivity for low-temperature solid oxide fuel cells, Journal of Power Sources 196 (2011) 2754–2758
• Xiaodi Wang, Ying Mab, Rizwan Raza, Mamoun Muhammed, Bin Zhu, Novel core–shell SDC/amorphous Na2CO3 nanocomposite electrolyte for low-temperature SOFCs, Electrochemistry Communications 10 (2008) 1617–1620
• Yicheng Zhao, Chun Xia, Lijun Jia, Zhiming Wang, Hongjiao Li, Jinshuai Yu, Yongdan Li*, Recent progress on solid oxide fuel cell: Lowering temperature and utilizing non-hydrogen fuels, international journal of hydrogen energy xxx (2013) 1-20