UF-DOE HiTEC

Hydrogen Production with Mixed Protonic-ElectronicConducting Perovskite Membranes

Eric D. WachsmanUF-DOE High Temperature Electrochemistry Center

Department of Materials Science and EngineeringUniversity of Florida

Gainesville, FL 32611ewach@mse.ufl.edu

UF-DOE HiTEC

UF-DOE HiTEC

Outline

• Introduction• Fundamentals and Materials Development• Membrane Reactor Fabrication and Results• Recent Membrane Materials Advances• Conclusions

UF-DOE HiTEC

Ni-SrCeO3 porous tubular support•Support for hydrogen membrane•Ni catalyzes endothermic steam reforming orwater gas-shift reaction

SrCe1-xEuxO3-δ dense hydrogen membrane•Mixed proton-electron conductor•~10 µm dense layer

Oxygen transport membrane•Exothermic oxidation of hydrocarbon feed gas

Concept - Autothermal Catalytic Membrane Reactorfor Production of Pure H2

CO2

Ultimately can produce pure H2 from anyhydrocarbon feed stock:

• Natural gas• Coal based syn gas• Biomass

UF-DOE HiTEC

Cost of Hydrogen Production from Natural Gas*

3.25 H2/CH4

CH4 ~ 0.20C$/m3

~$0.15/m3 H2

~0.015 ¢/liter H2

CH4 + 0.375 O2 + 1.25 H2O = CO2 + 3.25 H2

* Assumes 100% conversion and selectivity,air and water are free, and ignores capital cost

UF-DOE HiTEC

DOE’s Future Gen

• Hydrogen and electricity co-generation from coal• Zero emissions and CO2 capture

“Hydrogen Production from Fossil Fuels with Proton and Oxygen-Ion Transport Membranes,”E. D. Wachsman and M. C. Williams, Interface, Volume 13, No.3, Fall 2004

UF-DOE HiTEC

Outline

• Introduction• Fundamentals and Materials Development• Membrane Reactor Fabrication and Results• Recent Membrane Materials Advances• Conclusions

UF-DOE HiTEC

OXIDE-ION CONDUCTING MIEC’s

• Ionic and electronic conductivity results in O2 permeationlimited by oxide-ion conductivity σVo••

σi and σe of La0.8Sr0.2Co0.8Fe0.2O3-dTeraoka, et al (1998)

JO2 of La0.6Sr0.4Co0.8B0.2O3-dTeraoka, et al (1998)

Hydrocarbon Feed

O2 Permeation Membrane

O2, N2h•

Vo••

O2

Partially Oxidized Hydrocarbon Effluent

CnHm

CO, H2N2

UF-DOE HiTEC

OXIDE-ION vs. PROTONIC CONDUCTION

• Oxygen ions jump from a filled (OOx) to a vacant (VO

••) site• H-bonded protons form an OH group (OHO

•)• Protons move around OO

x and jump to neighboring OOx

VO••

OOx

MMx

OHO•

UF-DOE HiTEC

Partially Oxidized Hydrocarbon Feed

H2 Permeation Membrane

H2e’

OHo•

H2

CO, H2, CH4

CO, C2+

Hydrogen Depleted Effluent

SrCeO3-δ layer

Ni-GDC porous support

PROTONIC vs. OXIDE-ION CONDUCTORS

• Protonic conductors have comparable ionic conductivity butnegligible electronic conductivity

• H2 flux limited by electronic conductivity (σe’)

σi and σe of La0.8Sr0.2Co0.8Fe0.2O3-dTeraoka, et al (1998)Iwahara, et al.

UF-DOE HiTEC

• Add electronic conductivity by doping Ce sitewith multivalent cation (M3+/2+) that can bereduced to 2+– MCe” = MCe

’ + e’ (n-type conduction)

• Match ionic radii for– Phase stability– Proton conductivity– > Eu3+/2+

Eu3+

Conductivity of BaCe1-xMxO3-d as a function rM ,Iwahara et al (1993)

Adding Electronic Conductivity to a Proton Conductor

E. D. Wachsman and N. Jiang, October 2, 2001, U.S. Patent No. 6,296,687.

UF-DOE HiTEC

H2 Flux Relationship

Proton flux across calculated using Wagner equation:• Assumes that bulk diffusion is rate limiting step• σt is the total conductivity

– σi = zi q ui [i], (i = OHO•, VO

••, e’)

• Transference number, ti = σi / σt

– High flux requires both high protonic and high electronic conductivity

• F is Faraday’s constant• L is the membrane thickness• Integrate both O2 and H2 potential gradients

!! ++"= •••••••

//

2

/

22

/

//

2

/

22

ln)(2

ln4[1

22

H

HOO

O

OOOO

P

PHeVOHt

P

POVOHtOH

PdtttF

RTPdtt

F

RT

LJ ##

UF-DOE HiTEC

Complex Defect EquilibriaCharge

neutrality n p ][ !!

OV ][ !

OOH ][ /

CeEu ][ //

CeEu

][2!!

= OVn 6

1

3

1

2}2{

"

ORPK

6

1

3

1 2

}2{

O

R

i P

K

K

6

1

3

1

2)

4(

"

OR PK

2

1

12

1

6

13

22}

4{

OHOWR PPKK "

6

1

3

1 2

}2{

][O

RA

ti P

KK

EuK

tCeEuEu ][][ //

=

][][ // !!= OCeVEu

AKp <<

4

1

2

1

2}][

{"

O

t

R PEu

K 4

1

2

12

2}][

{O

R

ti PK

EuK

tEu][

2

1

2

1

2}{

OHtWPEuK

4

1

2

1

2

32

2}][

{O

RA

ti PKK

EuK

tCeEuEu ][][

//=

][][ // !!= OCeVEu

AKp >>

6

1

3

1

2}][

{"

O

tA

Ri PEuK

KK 6

1

3

12

2}][

{O

R

tAi PK

EuKK 6

1

3

2

2}][

{"

O

Ri

tAR

PKK

EuKK

2

1

12

1

3

1

2

1

22}

][{}{

OHO

Ri

tARW PP

KK

EuKKK

"

][][][///CetCe EuEuEu "= 6

1

3

2

2}][

{"

O

Ri

tAR

PKK

EuKK

][2][ / !!= OCeVEu

4

1

2

1

2}][

2{

"

O

t

R PEu

K 4

1

2

12

2}

2

][{

O

R

ti PK

EuK

2

][ tEu 2

1

2

1

2}

2{

OHtW P

EuK

tCeEuEu ][][ /

= 4

1

2

1

2

2

2}][2

{"

O

i

tRA PK

EuKK

][ != OOHn

4

1

8

1

4

1

22}{

OHORWPPKK

"

4

1

8

1

4

14

22}{

"

OHO

RW

i PPKK

K 2

1

4

1

2

1

22}{

""

OHO

W

R PPK

K

4

1

8

1

4

1

22}{

OHORWPPKK

"

4

1

8

1

4

1

44

4

22}

][{

""

OHO

iA

tRWPP

KK

EuKK

tCeEuEu ][][ /

=

][][ / != OCeOHEu

2

1

4

1

2

1

2 22}

][{

OHO

t

RW PPEu

KK " 2

1

4

1

2

122

22}

][{

"

OHO

RW

it PPKK

KEu 1

2

2

][ "OH

W

t PK

Eu

tEu ][

tEu][ 2

1

4

1

2

1

2

2

22}{

OHO

i

RWA PPK

KKK "

][][2 // != OCeOHEu

AKp <<

2

1

4

1

2

1

2 22}][4

{OHO

t

RW PPEu

KK " 2

1

4

1

2

122

22}

][4{

"

OHO

RW

it PPKK

KEu 1

2

2

][ "OH

W

t PK

Eu

tEu][2 2

1

4

1

2

1

2

24

22}

][4{

"

OHO

ARW

it PPKKK

KEu

tEu][

][][2 // != OCeOHEu

AKp >>

4

1

8

1

4

1

22

2

22}

][4{

OHO

tA

iRW PPEuK

KKK " 4

1

8

1

4

1222

22}

][4{

"

OHO

RW

tiA PPKK

EuKK

2

1

4

1

2

122

22}

][4{

""

OHO

W

tRA PPK

EuKK

4

1

8

1

4

1

22

22}][4{

OHOtRWA PPEuKKK"

][][][//Cett EuEuEu "=

4

1

8

1

4

1

2

22

22}

4

][{

OHO

i

tWRA PPK

EuKKK "

pEuCe

=][ /

t

i

Eu

K

][

tEu ][

2

1

2

2

2}

][{

"

O

i

Rt PK

KEu 2

1

4

1

2

2

22}][

{ OHO

i

tWR PPK

EuKK "

tEu][

AK

Charge Neutrality

]2[••

=O

Vn

][]//

[••

=O

VCe

Eu

][OH•

=O

n

]2[]/

[••

=O

VCe

Eu

AKp <<

AKp <<

AKp >>

AKp >>

][]//

[••

=O

VCe

Eu

][OH]/

[•

=OCe

Eu

][OH]//

2[•

=OCe

Eu

][OH]//

2[•

=OCe

Eu

pCeEu =]/

[

UF-DOE HiTEC

Modeling Defect Equilibria and Transport -effect of PH2, PO2, PH2O

S. J. Song, E. D. Wachsman, S. E. Dorris, and U. Balachandran, Solid State Ionics, 149,

1-10 (2002).

UF-DOE HiTEC

Modeling Defect Equilibria and Transport

σi = zi q ui [i]

UF-DOE HiTEC

Selection of Dopant - Conductivity as a Function of PO2

BaCe0.85Gd0.15O2.93• Negligible n-type electronic

conductivity except at veryhigh temperature >1000°C

n-type p-type

N. Bonanos (1992)

-1.8

-1.75

-1.7

-1.65

-1.6

-30 -25 -20 -15 -10 -5 0 5

700°C

600°C

log

! (S/cm)

log Po2

log σ

(S/c

m)

BaCe0.85Eu0.15O2.93• Significant n-type electronic

conductivity at much lowertemperature and higher PO2

J. Rhodes and E.D. Wachsman (2001).

UF-DOE HiTEC

• At high temperature (>750°C) permeation is bulk transport controlled– Flux is linear with 1/L

• At lower temperature permeation is surface kinetic controlled

0

0.001

0.002

0.003

0.004

0.005

0.006

600 650 700 750 800 850 900

100% H2 0.75 mm

90% H2 1.00 mm

90% H2 2.00 mm

HY

DR

OG

EN

FL

UX

(cc/c

m 2-m

in)

TEMPERATURE (oC)

0

0.001

0.002

0.003

0.004

0.005

0.006

0.4 0.6 0.8 1 1.2 1.4

HY

DR

OG

EN

FLU

X (

cc/c

m 2

-min

)

1/THICKNESS (mm)

850oC

800oC

750oC

Flux ~ 1/membrane thickness (L)

!! ++"= •••••••

//

2

/

22

/

//

2

/

22

ln)(2

ln4[1

22

H

HOO

O

OOOO

P

PHeVOHt

P

POVOHtOH

PdtttF

RTPdtt

F

RT

LJ ##

H2 Flux Relationship

UF-DOE HiTEC

Outline

• Introduction• Fundamentals and Materials Development• Membrane Reactor Fabrication and Results• Recent Membrane Materials Advances• Conclusions

UF-DOE HiTEC

Slurry coating for membrane thin filmCo-firing support and membrane thin filmSintered hydrogen membrane cell

Hydrogen Membrane Cell Fabrication

UF-DOE HiTEC

Fabrication of Membrane Reactor

UF-DOE HiTEC

Hydrogen Membrane Evaluation

All tubes are continuously leak checked by Ar tracer in feed gas

UF-DOE HiTEC

Hydrogen Permeation and Leak Testing

• Confirms membranes are leak free • Capable of producing 100% purity H2

UF-DOE HiTECHydrogen flux ~ PH2 1/4

Hydrogen Permeation

UF-DOE HiTEC

Activation energy of ~0.9 eV indicates flux limited by σe− σOH• activation energy ~ 0.5 eV

Hydrogen Permeation

0.9240.890.930.960.970.86Activation energy,E (eV)

average value10.600.350.200.075PH2 (atm)

UF-DOE HiTEC

H2 -3% H2O balance Ar / SrCe0.9Eu0.1O3 /He

Hydrogen Permeation

Membrane tubes produce7 cc/min of pure H2

UF-DOE HiTEC

H2 balance He / SrCe0.95Tm0.05O3 / 20% O2 balance He[1] S. Cheng, V. K. Gupta, and J. Y. S. Lin, Solid State Ionics 176 (2005) 2653.

4% H2 -3% H2O balance He / Ni-BaCe0.8Y0.2O3 / N2 with 100ppm H2[2] C. Zuo, T. H. Lee, S.-J. Song, L. Chen, S. E. Dorris, U. Balachandran, and M. Liu, Electrochem. Solid-State Lett., 8 (2005) J35

H2 -3% H2O balance Ar / SrCe0.9Eu0.1O3 /He

Hydrogen Permeation

Area normalized membraneflux comparable to best inliterature.

However…

UF-DOE HiTEC

Pure H2 produced directly by internal steam reforming CH4• H2 flux even higher than from comparable H2 feed

Hydrogen Production

CH4/H2O ~ 2

UF-DOE HiTEC• 3% CO and H2O balance He• Solid lines are H2O/CO=1, dashed lines are H2O/CO≈2

0

20

40

60

80

100

0

0.1

0.2

0.3

0.4

0.5

0.6

650 700 750 800 850 900 950

Temperature (oC)

Con

vers

ion

(%)

Hydrogen production and

Permeation Flux (cc/m

in)

H2 Permeation

Without H2 permeation

Thermodynamic calculation

With H2 permeation

Hydrogen Production

Water gas shift reaction: CO + H2O -> CO2 + H2

UF-DOE HiTEC

Outline

• Introduction• Fundamentals and Materials Development• Membrane Reactor Fabrication and Results• Recent Membrane Materials Advances• Conclusions

UF-DOE HiTEC

-4

-3.6

-3.2

-2.8

-2.4

5 10 15 20

Doping concentration of Eu on SrCeO3 (mol %)

900oC

800oC

700oC

600oC

0.49 eV

0.52 eV

0.87 eV

10 mol%

15 mol%

20 mol%

Activation Energy

Total conductivity maximum at ~10% Eu

Conductivity of Eu-doped SrCeO3

Log

σPr

oton

(Scm

-1)

UF-DOE HiTEC

-4.5

-4

-3.5

-3

-2.5

-2

10 15 20

900oC

800oC

700oC

600oC

Doping concentration of Eu (mol %)

-4.5

-4

-3.5

-3

-2.5

-2

10 15 20

Doping concentration of Eu (mol %)

900oC

800oC

700oC

600oC

Proton Conductivity Electron Conductivity

Proton vs. Electron ConductivityL

og σ

Prot

on (S

cm-1

)

Log

σE

lect

ron (

Scm

-1)

Increasing Eu concentration:• Decreases σOH•• Increases σe’

UF-DOE HiTEC

0

0.2

0.4

0.6

0.8

1

600 700 800 900

Temperature (oC)

Proton [Eu10]

Proton [Eu15]

Proton [Eu20]

Electron [Eu10]

Electron [Eu15]

Electron [Eu20]

Increased Electronic Transference NumberTr

ansf

eren

ce n

umbe

r

!

tOH

O

• ="

OHO

•

"OH

O

• +" # e

t # e =

" # e

"OH

O

• +" # e

H2 flux limited by electronic conductivity

UF-DOE HiTEC

Conclusions• High temperature protonic conductors offer tremendous potential for

H2 production

• Adding electronic conductivity significantly increases H2 flux

• Demonstrated H2 permeation flux of ~10 cc/min– H2 flux is proportional to [PH2]1/4

– H2 flux is limited by electronic conduction

• Demonstrated pure H2 production from internal steam reformed CH4

• Demonstrated pure H2 production from water-gas-shift reaction– Increased H2 production of membrane reactor - La Chatlier

• Increasing Eu-dopant concentration will significantly increase H2permeation and production– Demonstrated >10X increase in te

– Should result in 6 liter/hr H2 production per tube

UF-DOE HiTEC

NASA Contract NAG3-2930DOE HiTEC Contract DE-AC05-76RL01830

Heesung YoonTakeun OhJianlin Li

Sun Ju SongJamie Rhodes

Acknowledgements

UF-DOE HiTEC

Hydrogen Production, Transport, and Storage 2

Abstracts should be submitted via the ECS website by January 3, 2007.

Comments and inquiries about the symposium may be sent to the organizers:E. D. Wachsman, University of Florida, ewach@mse.ufl.eduM. C. Williams, NETL, mark.williams@netl.doe.govM. Heben, NREL, Michael_heben@nrel.govA. Manivannan, NETL, manivana@netl.doe.govB. P. Maupin, U.S. Department of Energy, paul.maupin@science.doe.govC. V. Ramani, Illinois Institute of Technology, ramani@iit.edu

Symposium B4The Electrochemical Society

Chicago, May 6-11, 2007