ECP Transport Characterization

Comparison of basic architectural requirements

Roadmap for ECP Modules

Electrochemical CO2 Pump

A proof-of-concept for automotive hydroxide exchange

membrane fuel cell (HEMFC) systems, enabled by a

novel electrochemical CO2 pump (ECP) for CO2

mitigation.

End of project deliverable, 1 kW system meeting:

Project Vision

CO2-mitigated HEMFC system

ECP Performance

Hollow fiber ECP

Directions for Future Research

Advanced Alkaline Membrane H2/Air Fuel Cell System

with Novel Technique for Air CO2 RemovalBrian P. Setzler, Lin Shi, Stephanie Matz, Catherine Weiss, Santiago Rojas-Carbonell, Teng Wang, Yun Zhao,

Yushan Yan (co-PI), and Shimshon Gottesfeld (PI)

Chemical & Biomolecular Engineering, University of Delaware, Newark, DE 19716

CO2-free HEMFC performance

CO2-containinggas stream

CO2-freegas stream𝐶𝑂2 + 𝑂𝐻− → 𝐻𝐶𝑂3

−

𝑂2 + 2𝐻2𝑂 + 4𝑒− → 4𝑂𝐻−

Internal /Externale- path

𝑂𝐻−

𝐻𝐶𝑂3−

𝐶𝑂2

𝐻𝐶𝑂3− +𝐻+ → 𝐶𝑂2 +𝐻2𝑂

𝐻2 → 2𝐻+ + 2𝑒−

𝐻+𝐻𝐶𝑂3

−

𝐶𝑂2

H2 purge CO2-rich purge

𝑂2

𝐻2

Cathode

Membrane

Anode

ElectrocatalystIonomerPore

HydrogenTank

AirIntake

(400 ppmCO2)

AirFilter

AirCompressor

MembraneHumidifier

ECP

CO2

ECPExhaust

Fuel Cell

H2O

H2 Blower

AirExhaust

20 mA/cm2

1.5 A/cm2Purge Valve

≈2% of H2 Supply

CO2-free AirPurge H2, N2

Anode reactions (pH=7-8)𝐻2 → 2𝐻+ + 2𝑒−

𝐻2 + 𝐶𝑂32− → 𝐶𝑂2 + 𝐻2𝑂 + 2𝑒−

Cathode reactions (pH=12-14)𝑂2 + 2𝐻2𝑂 + 4𝑒− → 4𝑂𝐻−

𝑂2 + 2𝐶𝑂2 + 4𝑒− → 2𝐶𝑂32−

CO2

O2

CO32-HCO3

-

OH-H2

CO2

H2O

H+

e-

MembraneCathode

Anode

Air CO2-free air

H2

CO

2-r

ich

H

2

(Plastic) housing(Epoxy) sealing plug

Individual hollow fiber (diameter greatly exaggerated)

0

1

2

3

4

5

6

7

8

9

10

0 20 40 60

Gas

Ph

ase

Tran

spo

rt R

esis

tan

ce (

s/m

)

ECP module pressure drop (kPa)

Correlations from: G. Srivathsan, Modeling of Fluid Flow in Spiral

Wound Reverse Osmosis Membranes, thesis, UNIVERSITY OF

MINNESOTA (2013).

1 mm thickness

0.2 mm

Mass transport /

pressure drop tradeoff

ECP for 100 kW HEMFC, 2:1 L:D spiral

wound module

<10 s/m at <20 kPa is easily achievable

(Sterlitech Corporation)

Fuel cell• >1 A/cm2

• >1 W/cm2 heat• <0.03 Ohm-cm2 e-

• Flow field land and GDL increase gas phase RMT

ECP requirements• ≤0.05 A/cm2

• ≤0.06 W/cm2 heat• ~2 Ohm-cm2 e-

• Can use convection-inducing mesh spacer to create flow channels

• Can eliminate GDL• Ultra-low gas RMT

Catalyst layer

CO2CO2 CO2

CO2 Transport Resistances

1. Diffusion in feed channel

2. Diffusion in GDL & CL

3. Diffusion in ionomer film

4. Reaction with hydroxide

AirChannel

Catalyst-

coated

membrane

CO2

Catalyst-

coated

membrane

H2Channel

12

CO22

3 4

CO2

OH- CO32-

3 4

Catalyst /

Support

Ionomer

Pore

CathodeMem

bra

ne

Descriptor Quantitative Target

Ambient Air 400 ppm CO2

Low PGM stack ≤0.125 mgPGM cm-2

High performance 0.65 V @ 1.5 A cm-2

Durable stack400 h @ 80 °C

(≤10% loss)

Compact ECP : FC volume ≤0.3 : 1

Efficient ≤2% system H2 to ECP

Low Cost ≤$2 kW-1 for ECP

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00.2

0.4

0.6

0.8

1.0

Ce

ll V

olta

ge

(V

)

Current Density (A/cm2)

Anode Loading

0.6 mgPGM PtRu/C

0.3 mgPGM PtRu/C

0.65 V target1.76 A/cm2

1.14 W/cm2

2.09 A/cm2

1.36 W/cm2

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00.2

0.4

0.6

0.8

1.0

Ce

ll V

olta

ge

(V

)

Current Density (A/cm2)

95 °C

80 °C

0.65 V target

1.76 A/cm2

1.14 W/cm2

1.21 A/cm2

0.79 W/cm2

CO2 effect in HEMFCs

HEM: PAP-TP-85, 5 µm

Anode: Pt/C (0.4 mgPt/cm2)

Cathode: Pt/C (0.4 mgPt/cm2)

Ionomer: PAP-BP-60

Flow: 600 sccm H2 (100% RH)

600 sccm O2 or 2000 sccm air (100% RH)

BP: 100 / 100 kPag

0 500 1000 1500 2000 25000.0

0.2

0.4

0.6

0.8

1.0

Current density / mA cm2

Vo

lta

ge

/ V

O2

Air, CO2-free

Air, 350 ppm CO2

at 95 oC and 100 kPag

0 500 1000 1500 2000 25000

50

100

150

Current density / mA cm2

AS

R /

mc

m2

80 mΩ cm2

100 mΩ cm2120 mΩ cm2

Key electrochemical CO2 pump (ECP) attributes

• Continuous – no sorption or regeneration

• Electrochemically pumped –concentrates sub-ppm to %

• Compact – optimized for CO2 mass transport,

• Efficient – Powered by ≤2% of system H2 in anode purge

• Low Cost – Low-cost ECP MEA and module architectures

0.001

0.01

0.1

1

10

100

1000

10000

100000

1000000

0

0.2

0.4

0.6

0.8

1

7 8 9 10 11 12 13 14

pp

m C

O2

at

1 b

ar

Site

exc

han

ge o

f an

ion

s

pH

CarbonateBicarbonate Hydroxide

Gaseous CO2

(right)

T = 95 °C Anode Outlet

Cathode Inlet

Cathode pHAnode pH

50% H2 Utilization

98% H2 Utilization

0 5 10 15 20 25 30

0.0

0.2

0.4

0.6

0.8

1.0

1.2

CO3

2-

HCO3

-

An. Ca.

An

ion

Site

Exch

ang

e

x-coordinate, µm

Membrane

OH-

0 5 10 15 20 25 30-100

-10

-1

0

1

10

100

10 mA/cm2

0 mA/cm2

An. Ca.

CO

2 r

ea

ctio

n r

ate

, m

ol/m

3s

x-coordinate, µm

Membrane

20 mA/cm2

1-D MEA model

Simulating local conditions at 99.9% removal

70 °C | Anode: 100,000 ppm CO2 | 0.4 ppm CO2

Concentration profiles at 20 mA/cm2 CO2 capture / release rate

CO

2cap

ture

CO

2release

0

50

100

150

200

250

1 10 100

Ma

ss T

ran

sp

ort

Re

sis

tan

ce

(s/m

)

Outlet CO2 Concentration (ppm)

70 °C

60 °C

50 °C

10 mA/cm2

1

10

100

1000

0 5 10

CO

2o

utle

t co

nce

ntr

atio

n (

pp

m)

Inverse flow rate (1000/sccm)

70 °C

60 °C

50 °C

10 mA/cm2

CO2-free air

Air

CO2-rich H2

H2

(Insulating) cylindrical housing

Inner tube

𝑅𝑀 =1

𝑘𝑀=

𝐴

𝑣𝑎𝑖𝑟ln

𝑥𝐶𝑂2𝑖𝑛

𝑥𝐶𝑂2𝑜𝑢𝑡

−1 𝐴 cell area (m2)

𝑣𝑎𝑖𝑟 volume flowrate of air (m3/s)

𝑥𝐶𝑂2 mole fraction of CO2 in air

𝑅𝑀 CO2 mass transport

resistance (s/m)

𝑘𝑀 CO2 mass transport

coefficient (m/s)

1%

10%

100%

0 2 4 6 8

CO

2re

mai

nin

g in

ou

tlet

Inverse Cathode Flow (1000/sccm)

Triple serpentine -25BA - low ionomer

Triple serpentine -25BA - high ionomer

Interdigitated - 29BC -High ionomer

2% leak-through

90%

92%

94%

96%

98%

100%

0 5 10

CO

2R

emo

val (

%)

Time (h)

0

10

20

30

40

50

60

70

80

0 5 10

Mas

s Tr

ansp

ort

Res

ista

nce

(s/

m)

Time (h)

10

100

1000

0 20 40 60

CO

2outlet

concentr

atio

n (

ppm

)

Anode flow rate (sccm)

Triple Serpentine-Triple Serpentine

Single Serpentine-Triple Serpentine

Single Serpentine-Interdigitated

100% H2 Utilization

MEA Construction

HEM: PAP-TP-85, ~20 µm

Ionomer: PAP-BP-100 or PAP-TP-100*

Anode: 5-40 wt% Pt/C, 0.01-0.1 mgPt/cm2

Anode GDL SGL 29BC

Cathode: Ag, 0.6 mg/cm2 or 40 wt% Pt/C 0.1 mgPt/cm2

Interlayer: Vulcan XC72 + 30-40% ionomer, ca. 1 mg/cm2

Cathode GDL SGL 25BA or SGL 29BC

Testing conditions

Temperature: 60 - 70 °C*

Anode Flow: 7-50 sccm H2 (80-90% RH)

Cathode Flow: 100-1000 sccm air (80-90% RH)

500 sccm air, 80% RH

BP: 0 / 0 kPag

Condition: 1 h hold, average last 30 min

*Bold values apply to top figures

H2 H2 H2

Cathode

AnodeMembrane

Gasket

(Insulating)feed spacer

(Insulating)seed spacer

MembraneCathode

Anode

H2 H2 H2

H2 H2

Air CO2-free

Air CO2-free

CO2-free

No bipolar plate,just another cell

AirCathode

feedchannel

Anodefeed

channel

MEA Construction

HEM: PAP-TP-85, 15 µm

Ionomer: PAP-TP-100

Anode: 75 wt% 2:1 PtRu/C, 0.3-0.6 mgPGM/cm2

Anode GDL SGL 29BC

Cathode: 40 wt% Pt/C 0.4 mgPt/cm2

Cathode GDL SGL 25BA or SGL 29BC

Pretreatment: Soak in 3 M KOH, blot dry (no rinse)

Testing conditions

Temperature: 80-95 °C

Anode Flow: 1000 sccm H2, 75% RH

Cathode Flow: 2000 sccm CO2-free air, 106% RH

BP: 250 / 250 kPag

Condition: 5 s hold, 0.2 A/cm2 step, average

of forward and reverse scans

The information, data, or work presented herein was funded in part by the

Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of

Energy, under Award Number DE-AR0001034. The views and opinions of

authors expressed herein do not necessarily state or reflect those of the

United States Government or any agency thereof.

Acknowledgements

Award Number DE-AR0001034

Presentation Date: 2019.04.30