Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid...

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Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner 1 , Andrea Ambrosini 1 , Michael Hibbs 1 , Kirsten M. Norman 1 , Cy H. Fujimoto 1 , Christopher J. Cornelius 1 , Milton E. Vernon 2 , Fred Gelbard 2 Paul Pickard 2 , 1 06338 Fuels and Energy Transitions 2 06771 Advanced Nuclear Concepts Sandia National Laboratory Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000. This presentation does not contain any proprietary, confidential, or otherwise restricted information Project ID # PDP32

Transcript of Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid...

Page 1: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Membrane Development for Hybrid Sulfur Electrolysis and

Oxygen SeparationMichael A. Hickner1, Andrea Ambrosini1, Michael Hibbs1,

Kirsten M. Norman1, Cy H. Fujimoto1, Christopher J. Cornelius1, Milton E. Vernon2, Fred Gelbard2 Paul Pickard2,

1 06338 Fuels and Energy Transitions2 06771 Advanced Nuclear Concepts

Sandia National Laboratory

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy’s National Nuclear Security Administration

under contract DE-AC04-94AL85000.

This presentation does not contain any proprietary, confidential, or otherwise restricted information

Project ID #PDP32

Page 2: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Sulfur Based Thermochemical CyclesFor Nuclear Hydrogen Production

(Albert C. Marshall SAND2002-0513 February 2002 An Assessment of Reactor Types for Thermochemical Hydrogen Production)

The Sulfur based cycles –- Sulfur-Iodine - Hybrid Sulfur

are the focus of the current NHI research program.

These cycles are the most technically developed of the more that 200 cycles reviewed and have the potential for high efficiencies.

The Nuclear Hydrogen Initiative is investigating thermochemicalcycles as one of the promising method for hydrogen production using Generation IV reactors.

Page 3: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Sulfur-Iodine versus Hybrid Sulfur Cycle

Hybrid-Sulfur (thermal and electrochemical reactors)advantages disadvantages- fewer reactions - electrochemical reactor cost- no HI or I2 - electricity needed (efficiency??)

Page 4: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

SNL Membrane Approach for Efficiency and Process Improvements

Develop new high-temperature (120-150°C) proton exchange membranes with high conductivity and low SO2crossover for efficient electrolysis

Sandia-synthesized polymer membranes have shown promise in high temperature electrochemical processes, e.g. fuel cells.

Sulfonated membranes with high temperature capability are being tested under a variety of conditions in an SO2electrolysis cell. Conditions of the process unit are being optimized and efficiency/lifetime is being measured.

Synthesize new oxygen anion conducting ceramic membranes for high temperature oxygen separation.

Sandia has proven capability in novel ceramic materials and a wide-ranging program in membrane separations.

Oxygen anion conducting ceramics are being tested for their stability in the high temperature reactor environment and their separation characteristics.

High temperature thermal reactor Proton exchange membrane electrochemical reactor

Page 5: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Ceramic Oxygen Separation Membranes

Characteristics:•Dense Ceramic Membrane– separates via ion conduction, not size exclusion• Self-supporting• Mixed ionic-electronic conductor– ionic component allows for conduction of oxide anion while electronic component eliminates the need for an applied potential

High pO2(sweep side)

Low pO2(feed side)Membrane

O2-

e-

O2H2SO4, O2

H2O, SO2

Page 6: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Perovskite ABO3

• Stable at high temperatures

• Amenable to doping and substitution by a variety of cations on both the A- and B-sites

• Can stabilize oxygen nonstoichiometries

• Mixed ionic-electronic conductivities

• Known membrane materials

Page 7: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Nitrate synthesis: • Nitrates of starting materials dissolved in DI H2O• Citric acid added• Sol’n heated at 90 ºC to evaporate H2O• Resulting gels dried overnight then self-ignited at 400 ºC• Powder ground up in mortar and pestle• Sintered at 1250 ºC for 24 hr

Characterization:• Powder x-ray diffraction (PXRD)• Thermogravimetric analysis (TGA)• Four-probe conductivity• Scanning electron microscopy/electron dispersive spectroscopy• Permeation measurements

Synthesis and Characterization

Page 8: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

PXRD of La0.1Sr0.9Co0.7Mn0.3O3-δ

Space group Pm-3mSpace group Pm-3m

Rf = 4.78Chi2 = 4.44

Page 9: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

TGA Cycle of La0.1Sr0.9Co0.7Mn0.3O3-δ

• The first part of the graph shows the weight change as the temperature is cycled between 50-850 °C, under a constant flow of O2 gas. This describes an easily reversible temperature-swing adsorption/desorption of oxygen. • The second part of the graph illustrates the reversible weight change as a function of oxygen partial pressure, by cycling the gas between O2 and Ar at a constant temperature of 850 °C. This implies that the material can transport oxygen across a membrane by pressure differential. • X-ray diffraction of the material after TGA cycles shows little/no change in structure which illustrates the stability of the structure.

-0.9399% (-0.5692mg)

-0.9574% (-0.5798mg)

0.9484% (0.5743mg)

-0.06516% (-0.03946mg)

0.8816% (0.5339mg)

0.9010% (0.5456mg)

0

200

400

600

800

1000

Tem

pera

ture

(°C

)

98.0

98.5

99.0

99.5

100.0

100.5

Wei

ght (

%)

0 200 400 600 800 1000 1200 1400

Time (min) Universal V2.5H TA Instruments

Temperature cycle 50 – 850 ºC under flowing O2

Pressure cycle between Ar and O2 at 850 ºC

Ar Ar Ar

O2 O2 O2

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Four-Probe Conductivity of LSCM

• Conductivity is several orders of magnitude better than YSZ • Conductivity ↑ as temperature ↑ and pO2 ↑• Large magnitude implies electronic conductivity contribution• Ionic contribution between 0.2 – 0.4 S/cm at 850 °C

0.001

0.01

0.1

1

10

100

1000

400 500 600 700 800 900 1000Temperature (C)

Log

Con

duct

ivity

(S/c

m)

LSCM1973LSCM1991YSZLSCF2882

vs. Temperature (in air)

0.001

0.01

0.1

1

10

100

1000

1.0E-05 1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00

Log pO2 (atm)Lo

g C

ondu

ctiv

ity (S

/cm

)

LSCM1973LSCM1991YSZLSCF2882

vs. pO2 (at 900 °C)

Garino, SNL

Page 11: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Oxygen Permeation Unit

Constructed of Inconel 600 Ni alloyConstructed of Inconel 600 Ni alloy

membranemembrane

Mass flow controller (air)

Mass flow controller (air)

thermocouplethermocouple

to µGCto µGC

Page 12: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Permeation Unit - Design

air

air outto micro GC

He O2

thermocouple tube furnace

Cu O-ring seal

¾ ″½ ″

⅛ ″⅛ ″

membrane

Page 13: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Permeation of LSCM Membranes

0.000

0.200

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0.600

0.800

1.000

1.200

1.400

1.600

780 800 820 840 860 880 900 920 940 960

Temperature (C)

Oxy

gen

Perm

eatio

n (m

l/min

.cm

2 )

LSCM1973LSCM1982LSCM1991

Eltron Research Inc.

Page 14: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Mini H2SO4 Decomposition Reactor

F. Gelbard, SNL

Goal: To test the stability of the membrane under “reactor” conditions

Page 15: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

10 20 30 40 50 60Two-Theta (deg)

0

500

1000

1500

Inte

nsity

(Cou

nts)

[AA2-58-2_postSO2.RAW] LSCM1982 post-H2SO4 decomp, 3h/850C 89-5717> (La0.6Sr0.4)CoO3 - Lanthanum Strontium Cobalt Oxide74-2035> Celestine - SrSO4

34-0328> SrS2 - Strontium Sulfide

Post-H2SO4 Decomposition

• Microscopy of cross-section reveals corrosion layer of approx. 5 µm • XRD (above) shows formation of SrSO4 and possibly SrS• Not yet known if corrosion caused by exposure to H2SO4, SO2, or both• Membrane can be regenerated by heating to 1300 °C under O2

Page 16: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Summary• The La0.1Sr0.9Co1-yMnyO3-δ (LSCM) family shows promise for use as

ceramic high-temperature oxygen separation membranes• The materials are robust under varying pO2 and show reversible oxygen

sorption properties at 850 ºC• Permeation measurements show the membranes are oxygen permeable• Preliminary stability tests show at least some corrosion occurs upon

exposure to the H2SO4 decomposition stream at 850 ºC

Ongoing Work• Ongoing high temperature permeation studies (SNL)• Continued structural elucidation• Determine extent of corrosion during H2SO4 decomposition and possible

mitigation steps• Continue membrane development (density, processing, scale-up)• Testing on actual decomposition reactor

Page 17: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

High Temperature Polymeric Proton Conducting MembranesSulfonated Diels-Alder Poly(phenylene) - SDAPP

nSO3H

HO3S• Thermal Stability• Good Chemical Stability• Chemical Diversity• Compositional Control• Ion Conductivity• Morphology

Polyphenylenes are a chemically, thermally, and mechanically stable backbone upon which to build a library of membranes (with both cation and anion fixed sites) for application to a large array of membrane-based processes such as fuel cells, water desalination, electrodialysis, etc.

Fujimoto, C.H, Hickner, M.A., Cornelius, C.J., Loy, D.A. Macromolecules 2005, 38(12), 5010-5016.

Page 18: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Electrolyzer Schematic

SO2 H2O

flow field flow fieldMEMBRANE

H+

H2H2O

H2O

Membrane Electrode Assembly Membrane Electrode Assembly –– MEAMEAMembraneMembraneCatalyst layersCatalyst layersGas diffusion layersGas diffusion layers

e-

SOSO22 + 2 H+ 2 H22O O + electric power+ electric power →→ HH22SOSO44 + H+ H22 + heat+ heatMembrane is critical for:• low SO2 crossover• efficient water transport• high temperature operationSNL Membrane PerformanceTarget: 0.5 mA/cm2 at 0.6V

Page 19: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

0.0

0.5

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1.5

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2.5

3.0

3.5

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5.0

4400 4650 4900 5150 5400 5650 5900 6150

Time (s)

Tota

l Cur

rent

(A)

100°C110°C

120°C3.5A

4.0A4.3A

Total cell current at 0.7 V cell potential of SDAPP 2.2 meq/g electrolysis cell with time at 100°C, 110°C, and 120°C cell temperature.

Cell Conditions:

Increased Temperature Promotes Better PerformanceHigh Temperature Enabled by SNL membranes

• 10 cm2 cell

• SDAPP 2.2 meq/g membrane batch

• 2 mg Pt/cm2 Pt Black anode and cathode

• Dry SO2 gas anode, 100 sccmconstant SO2 flow rate with 15 psig backpressure

• Preheated liquid water cathode, 3 mL/min constant H2O flow rate with 15 psig backpressure

Page 20: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Performance increase of SNLMembrane Electrolysis Cell at 0.7 V

0

50

100

150

200

250

300

350

400

450

500

80 90 100 110 120 130

Temperature (°C)

Cur

rent

Den

sity

@ 0

.7V

(mA

/cm

2 )

Current density at 0.7 V cell potential of SDAPP 2.2 meq/gelectrolysis cell as a function of temperature

Page 21: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Galvanostatic Performance of SNL Membrane at 120°C

0

0.1

0.2

0.3

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0.9

9150 9250 9350 9450 9550 9650 9750 9850

Time (s)

Cel

l Pot

entia

l @ 5

00 m

A/c

m2 (V

)

target0.6V

Cell potential at 500 mA/cm2 and 120°C for SNL SDAPP 2.2 meq/g electrolysis cell.

The average potential of the electrolysis cell for 10 minutes is 0.75 V. The previous best performance of this membrane was 0.83 V at 500 mA/cm2 and 80°C as measured by University of South Carolina.

Page 22: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Performance and Lifetime of SNL (4-141-D) Membranes

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3

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6

0 5 10 15 20

Time (Hours)To

tal C

urre

nt (A

)

Higher current densities are achieved at elevated temperatures with 0.4 mA/cm2 at 120°C. Extended stable performance for 16 hours at 0.8V and120°C is also demonstrated. The SDAAP 2.2 meq/g (4-141-D batch) electrolysis cell was tested with 100 sccm dry SO2 and and 6.4 ml/min H2O(l)flow rates and 15 psig backpressure.

0

0.1

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80 90 100 110 120 130

0.8 V0.7 V

Temperature (oC)

Cur

rent

Den

sity

(A/c

m2 )

Page 23: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Decreased SO2 Crossover Using SNL Membranes –less process loss, higher efficiency

SO2 crossover - process loss- parasitic H2 consumption- elemental sulfur buildup on the

cathode, block reaction sites

SO2 flux to cathode is lower for Sandia membranes even though SNL membranes are thinner.

Steady-state SO2 flux for Sandia membrane SDAAP 2.2 meq/g (4-141-D) and Nafion 212 (Lynntech MEA).

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

50 70 90 110 130

Temperature (C)

Sandia SDAAP 2.2

Lynntech (N212)

Flux

mol

es S

O2*

cm-2

*s-1

)

60 μm thick

90 μm thick

Page 24: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Potential H2 Losses from SO2 Crossover

Hydrogen consumption at cell cathode from SO2 Crossover:SO2 + 2 H2 → S(solid) + 2 H2O

Temperature Crossover FluxTheoretical Maximum

H2 ConsumptionCell Hydrogen

Production

Theoretical Maximum %H2

Loss

C μmol SO2/cm2*s μmol H2/cm2*s μmol H2/cm2*s %

90 0.397 0.794 1.68 47.1

100 0.322 0.644 1.81 35.5

110 0.272 0.544 2.02 26.9

120 0.176 0.352 2.10 16.8

More efficient hydrogen production is achieved at 120°C cell operating temperature.

The number noted above are the maximum amount of H2 lost. In reality, ~ 5% penalty is observed due to counter water flux at high currents.

Page 25: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Summary• SNL membranes have shown promise in SO2 electrolyzer tests.• High temperature, up to 120°C, and long run-time performance has been

demonstrated with SNL membranes.• SNL membranes have approximately 50% less SO2 permeability than

Nafion membranes.• Batch-to-batch repeatability needs improvement.

Ongoing Work• Repeated scaled-up synthesis of the polymer.• Large film casting.• Higher temperature variants of SNL polymers being tested.• Additional SO2 crossover measurements.

Page 26: Membrane Development for Hybrid Sulfur Electrolysis and ... · Membrane Development for Hybrid Sulfur Electrolysis and Oxygen Separation Michael A. Hickner1, Andrea Ambrosini1, ...

Acknowledgements

Our project partners at:Savannah River National Laboratory – William Summers,

David Hobbs, Hector Colon-MercadoUniversity of South Carolina – John Weidner, John Staser

Dr. Richard Mackay (Eltron Research, Inc)Dr. Margaret Welk (Permeation measurements)Mr. Gary Jones (Permeation unit construction)

Prof. Alexandra Navrotsky & Dr. R.G. Iyer(UC Davis, Calorimetry)

Dr. Bonnie McKenzie (SEM)