High Temperature Electrolysis Coupled to Nuclear Energy for Fuels - - PowerPoint PPT Presentation

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High Temperature Electrolysis Coupled to Nuclear Energy for Fuels Production and Load Following

Bilge Yildiz, Mujid Kazimi, Charles Forsberg Massachusetts Institute of Technology Department of Nuclear Science and Engineering

Tsinghua-Cambridge-MIT Low Carbon Energy University Alliance Video Conference January 13, 2010

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Electricity and hydrogen / syn-gas co-generation

• Hydrogen, syn-gas and electricity co-

generation using non-CO2 resources; promising route to decrease CO2-emissions, and enable large-scale energy storage.

• Large incentive for a reversible high-

temperature electrolysis-fuel cell (HTE-FC).

• GWs of gas turbines operate at few hundred

hours per year to meet peak electricity demand (very expensive gas turbine).

• HTE-FC may be much more economic than

HTE because of load following capability. Nuclear Energy

• CO2-free
• Efficient and cost-

competitive

• Size/location to address

the industry needs Heat and electricity Electrolysis and Fuel cell processes: H2O(g) ½ O2(g) + H2(g) Co-electrolysis: H2O(g) + CO2(g) O2(g) + H2(g) + CO(g)

Stoots et al.,

• J. Fuel Cell Sci.
• Tech. 2009

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Research approach in Laboratory for Electrochemical Interfaces ( lead by Prof. Bilge Yildiz, http://web.mit.edu/yildizgroup )

Cathode Electrolyte O-

O2, H2, H2S…

e-

Surface electronic structure spatially resolved: Scanning Tunneling Microscopy/Spectroscopy (STM/STS) Surface chemical and electronic structure, laterally averaged; X-ray and Electron spectroscopies GOAL: Understand the electronic and chemical behavior on oxide surfaces for energy applications: fuel cells, corrosion.

Isolate key parameters and unit processes using model systems in reaching to surface structure and chemistry in harsh environments.

Electronic structure, cation-

• xygen bonding, reaction

and transport kinetics First principles-based and atomistic simulations

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STM / STS set-up and experiment conditions

Gas doser;

• xyge,

hydrogen

Surface cleaning conditions T = 500 oC PO2 = 10-5 mbar t = 20-30 min Measurement conditions (example for SOFC application) T = 23 – 580 oC Psurface ~ 10-3 mbar. (Tested up to 20 mbar, 500oC.)

STM /nc‐AFM Omicron VT‐25

XPS

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Example: Effect of strain in oxygen conductivity in Y2O3 stabilized ZrO2 (Electrolyte for SOFC/SOEC)

The maximum relative enhancement in oxygen diffusivity (Do/Do

0):

6.8 × 103 times at 4% strain at 400 K.

Decrease at higher strains; Local relaxations, O‐C bond strengths. Oxygen plane Oxygen‐Cation (O‐C) bonding plane 400 K 600 K 800 K 1000 K critical strain

106 105 104 103 102 101 100

Increase up to a critical strain (fastest strain); Migration space, O‐C bond weakening.

0.02 0.04 0.06 0.08

DO/DO Tensile strain

Cation (Zr,Y) Vacancy

Decrease at higher strains; Local relaxations, O‐C bond strengths. Oxygen plane Oxygen‐Cation (O‐C) bonding plane 400 K 600 K 800 K 1000 K critical strain

106 105 104 103 102 101 100

Increase up to a critical strain (fastest strain); Migration space, O‐C bond weakening.

0.02 0.04 0.06 0.08

DO/DO Tensile strain

Cation (Zr,Y) Vacancy

Kushima A, Yildiz B: Oxygen ion diffusivity in strained yttria stabilized zirconia: where is the fastest strain? Journal of Materials Chemistry 2010, 20(23): 4809-4819.

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Example: In situ characterization of surface chemistry and electronic structure reactivity

La0.7Sr0.7MnO3 (LSM) oxygen electrode for SOFC/SOEC

(A) Polycrystalline La0.7Sr0.7MnO3 (LSM) thin film surface. (B) Step height-resolution (3.9±0.2 Å) on the epixatial (100) LSM surface, at 580oC, 10-3mbar. (C) PO2-dependence of the electron tunneling at 500 oC, on (B).

• 2
• 1

1 2

• 0.6
• 0.3

0.0 0.3 0.6

RT, 10‐10mbar 500°C, 10‐3mbar 500°C, 10‐10mbar

Tunneling Current (nA)

Bias Voltage (V)

200x200nm2

B

C

Tunneling at 2 V, 1 nA

A

800x800nm2

Katsiev K, Yildiz B, Balasubramaniam K, Salvador PA: Electron tunneling characteristics on La0.7Sr0.3MnO3 thin-film surfaces at high temperature. Appl Phys Lett 2009, 95(9), 2009

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⎯

1 2 3 4

20.0 µm

Example: Degradation of HTE materials

SSZ Anode + Bond Layer

200μm 10 μm

Bond Layer Anode

• Cr poisoning
• Cation / phase separation

Good adhesion Mn, from the IC coating Small amount of Cr Poor adhesion

Cr

O= e-

SSZ LSC Co Sr Anode

Sharma VI, Yildiz B: Degradation Mechanism in La0.8Sr0.2CoO3 as Contact Layer on the Solid Oxide Electrolysis Cell Anode, Journal of The Electrochemical Society, 157, B441-B448, 2010

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Potential project objective in this program

To identify electrode compositions that are active and durable in reversible operation of solid oxide fuel cell (SOFC) / electrolysis cell (SOEC) Synthesize thin model films, Electrochemical performance characterization Correlation of electrochemical performance (activity AND durability) to surface chemistry and electronic structure.

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University of Cambridge Atomistic Simulation Group

Background

Expertise: applied materials modeling using both classical MD and DFT Member: UK consortium on first principles calculations (UKCP) User/developer: CASTEP DFT code Energy‐related industrial collaborations: Pilkington Glass, Philips Electronics, Osram Semiconductors, Fiat, Bekaert Coatings Former MIT researcher & visiting professor

• Current Energy‐Related Projects
• Fast ion conduction

in doped nanoscale zirconia

• Carbon capture in

metal‐organic framework compounds

• Doping mechanisms in oxide materials for

solar cells, sensors and displays Department of Materials Science and Metallurgy Group Leader Dr Paul Bristowe

STO‐YSZ interface Znbpetpa unit cell