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