Application of Anion Exchange Membranes in Microbial Fuel Cells

Richard Burkitt and Eileen Yu

School of Chemical Engineering and Advanced Materials, Merz Court, University of Newcastle, Newcastle upon Tyne, NE1 7RU, United Kingdom

Introduction and Background Microbial Fuel Cell principle Anion exchange membranes in MFC

• Experimental setup Aim Membrane fixation and treatment Model of charge movement in non-precious metal MEA

• Half-Cell MEA Impedance Spectroscopy of MEA – General response Impedance Spectroscopy of MEA – Components of impedance

• Applicability of EIS for prediction of MFC performance Batch MFC tests vs. AC impedance of MEA

Conclusions

Outline

Microbial Fuel Cell (MFC) Principle

Use of wastewater for

Anolyte substrate

1) Organic removal

2) Power or H2 generation

Mixed charge carriers.

Charge Carriers in wastewater

Conc. mg/L Conc. mM/L Total Dissolved Solids 780 n/a

Bicarbonate Alkalinity, as CaC03 240 n/a Na+ 160 6.96 K+ 1.7 0.043

Calcium 76 1.9 Magnesium 33 3.1

Cl- 220 6.2 SO4

2- 88 0.916 Fl- 0.48 0.025

NO3- 24 0.387

NO2- ~2.5 0.054

Phosphorus, as PO4 0.081 0.0026

pH 7.2-7.4 Specific Conductance 2700 μS cm-1

Anion Exchange Materials in MFC

Ionomers;

2011 Watson and Logan Ionomer coatings Radel(Quartenized) vs Nafion. Power

Improvement factor 2.66.

Membranes;

2010 Zhang and Logan, and 2009 Kim and Guwy. International Membranes

CEM vs AEM for power production in MFC. Power Improvement factor 1.44 and

1.22 respectively.

2009 Sleutels and Buisman. Fumasep FKA (CEM) vs FAA (AEM) for H2

production. H2 production Improvement factor 5.25.

2008 Rozendal and Buisman. Charge carrier identification – H+/OH- ≈ Phosphate

2009 Mo and Cao. Tianwei CEM vs AEM, ΩCathode improvement factor 2.27.

2013 Piao and Cheng. Phosphate vs Bicarbonate, interfacial resistance

Anion Exchange Materials in MFC

Introduction and Background Microbial Fuel Cell principle Anion exchange membranes in MFC

• Experimental setup Aim Membrane fixation and treatment Model of charge movement in non-precious metal MEA

• Half-Cell MEA Impedance Spectroscopy of MEA – General response Impedance Spectroscopy of MEA – Components of impedance

• Applicability of EIS for prediction of MFC performance Batch MFC tests vs. AC impedance of MEA

Conclusions

Outline

Aim of study

• To compare the MFC batch performance with performance predicted

from MFC half cell – MFC reactors in artificial wastewater, Impedance Spectroscopy

• To examine the sources of interfacial resistance and examine the influence

of anionic charge carrier – Impedance Spectroscopy

• Test a variety of commercial membranes to produce recommendations for

material selection specific to MFC – Impedance Spectroscopy

• To assess how OH- produced from the oxygen reduction reaction influences

the diffusion boundary – Impedance Spectroscopy

Commercial Membranes

Membrane / Manufacturer Functional X-change group / Solvated ion Backbone

Thickness (wet) / (μm) IEQ / meq/g Reported κ / (Ω cm2)

@ Me+ MolesWorking

pHPrice / ( m-2)

Cation Exchange MaterialF-930 / Fumatech PerFluo-SO3

2- / H+ PTFE-Co-polymer 30 1.11 <0.2 @ 500mM NaCl N/A € 833CMI-7000 / International Membran SO3

2- / Na+ Gel Polystyrene/DVB 450 1.60 <30 @ 500mM NaCl (1-10) $97

Anion Exchange MaterialFTAM-A (PA) / Fumatech NH3

+ / Cl- Polyamide (Nylon) 500-600 1.70 <8 @ 500mM NaCl (5-13) € 333FAA (PEEK) / Fumatech NH3

+ / Cl- PEEK reinforced 130-150 1.43 <2 @ 500mM NaCl (1-14) € 583AMI-7001 / International Membran NH3

+ / Cl- Gel Polystyrene/DVB 450 1.30 <40 @ 500mM NaCl (1-10) $97

Morgane ADP® / Solvay NH3+ / Cl- PTFE - Xlink 150 1.65 1.5-4.5 @ 600mM NaCl (0-10)

QDPSU / made in house Dabco / Cl- Polysulfone 30 N/A N/AFAD-PET / Fumasep 2NH3

+ / Cl- Polyester reinforced 90 1.50 <0.8 @ 500mM NaCl (0-9) € 500FAB / Fumasep 2NH3

+ / Cl- PEEK reinforced 115 1.30 <1 @ 500mM NaCl (0-13) € 583

SeparatorRhinohide / Entek None / Oil content Polyethylene (long) 250ª 0.06 @ 1000mM H2SO4 N/A

MEA assembly

Impedance spectroscopy to evaluate membranes

The discrepancy between the applied signal and the phase-lag and reduction

In amplitude in the obtained current response produces data on the nature of

the impedance. This can be applied to a Membrane Electrode Assembly

100kHz>f>0.05Hz

10mV amplitude

Charge movement in air cathode AEM

Cathode Catalyst

Iron Phthalocyanine

(FePc)

Introduction and Background Microbial Fuel Cell principle Anion exchange membranes in MFC

• Experimental setup Aim Membrane fixation and treatment Model of charge movement in non-precious metal MEA

• Half-Cell MEA Impedance Spectroscopy of MEA – General response Impedance Spectroscopy of MEA – Components of impedance

• Applicability of EIS for prediction of MFC performance Batch MFC tests vs. AC impedance of MEA

Conclusions

Outline

Charge movement in catalyst layer

Z' / Ohm150 200 250 300 350 400

- Z"

(imag

inar

y) /

Ohm

0

50

100

150

200

250

300

0.4V0.24V0.20V-0.2 V

Without O2

WE potential

R2 > 0.9991 at all E

Thin Film Electrode (TFE)

Warburg impedance

at higher frequency;

• Charge Movement

• Capacitive upon charge saturation of entire film, large Z.

100Hz Electrolyte; Phosphate

Z' (real) / Ohm cm2

60 80 100 120

-Z"

(imag

inar

y) /

Ohm

cm

2

0

10

20

30

40SS-Mesh MembranelessETFE-QAmmonium JK80L Surrey

Rm

Warburg controlIon diffusion

Rdl R???

RAC = Rm + Rdl + R??

Key features of MEA response to EIS

E = -0.05V

50mM NaHCO3

F-93

0 / F

umas

ep

CM

I-700

0 / I

M

ADP

/ Mor

gane

FAA

/ Fum

asep

FTAM

-A /

Fum

asep

AMI-7

001

/ IM

QD

PSU

/ In

hou

se

Rm

/ O

hm c

m2

0

20

40

60

80

100

120

140

160

18050mM Na-Phosphate - MEA500mM NaCl - 2 electrode50mM NaCl - MEA50mM NaHCO3 - MEA

Ionic resistance in membrane phase

E = OCP

Similar trend to thickness

But not exactly

F-93

0 / F

umas

ep

CM

I-700

0 / I

M

ADP

/ Mor

gane

FAA

/ Fum

asep

FTAM

-A /

Fum

asep

AMI-7

001

/ IM

QD

PSU

/ In

hou

se

FAB

/ Fu

mas

ep

FAD

-PET

/ Fu

mas

ep

Rm

per

mic

ron

/ Ohm

cm

2

0.0

0.5

1.0

1.5

2.050mM Na-Phosphate - MEA500mM NaCl - 2 electrode50mM NaCl - MEA50mM NaHCO3 - MEA

Ionic resistance in membrane phase

Rm normalised to membrane

Thickness

The graph is not flat for all

membranes.

Rises indicate;

• Constrained flux

• Irreversible adsorption of

anion to fixed charge

Uniformity of membrane response

Z' (real) / Ohm cm260 80 100 120 140 160 180 200

-Z"

(imag

inar

y) /

Ohm

cm

2

0

10

20

30

40

50

Morgane ADPFAA (PEEK)SS-Mesh MembranelessRhinohideFTAM-A (PA)AMI-7001 QDPSUMeshless MebranelessETFE-QAmmoiun JK80L SurreyETFE-TMA CranfieldFAB-FumasepFAD-PET Fumasep

Bi-carbonate solution E = -0.05V

Z' (real) / Ohm cm260 80 100 120 140 160 180 200 220

-Z"

(imag

inar

y) /

Ohm

cm

2

0

10

20

30

40

50

Morgane ADPFAA (PEEK)SS-Mesh MembranelessRhinohideFTAM-A (PA)AMI-7001 QDPSUMeshless MembranelessETFE-QAmm JK80L SurreyETFE-TMA CranfieldFAB-FumasepFAD-PET Fumasep

OCP

E / V (Ag|AgCl)-0.4 -0.2 0.0 0.2 0.4

War

burg

co-

effic

ient

/ O

hm c

m2 s

-0.5

0

2

4

6

8

10

12

Morgane ADP FAA (PEEK) Membranelss SS-Mesh Rhinohide (separator)FTAM-A (PA) AMI-7001 HDPE-TMA Cranfield

Trend for membranes that saturate with OH- over Cl-

Trend for membranes that saturate with Cl- over OH-

Faster diffusion

Unbuffered NaCl electrolyte

Warburg impedance a relatively minor source of impedance in pure electrolytes

– used to harness transference data

Ion specificity – alternate qualitative means of evaluation

E / V (Ag|AgCl)-0.4 -0.2 0.0 0.2 0.4

RA

C /

Ohm

cm

2100

1000

NaClNa-PhosphateNaHCO3

FAA electrode

Total AC impedance (RAC) response

of the MEA is significantly

influenced by anion type.

The electrode performs well in chloride at high overpotential only

Total AC impedance vs. anion

Introduction and Background Microbial Fuel Cell principle Anion exchange membranes in MFC

• Experimental setup Aim Membrane fixation and treatment Model of charge movement in non-precious metal MEA

• Half-Cell MEA Impedance Spectroscopy of MEA – General response Impedance Spectroscopy of MEA – Components of impedance

• Applicability of EIS for prediction of MFC performance Batch MFC tests vs. AC impedance of MEA

Conclusions

Outline

Membrane / Manufacturer Ecat / mV (Ag|AgCl)

Vcell / mV

# of batch cylces

Anion Exchange Material

FTAM-A (PA) / Fumatech -23 289 13 FAA (PEEK) / Fumatech 0 324 18 AMI-7001 / Membranes International -54 309 6 QDPSU / made in house -63 307 13

Separator Rhinohide / Entek -121 257 13

Batch performance of MFC

Medium ; 0.5g/L CH3COONa, 50mM Phosphate, trace nutrients

Peak stabilised Vcell and Ecat over a batch cycle - Ωext = 300Ω

FTAM

-A /

Fum

atec

h

FAA

/ Fum

atec

h

AMI-7

001

/ IM

Rhi

nohi

de /

Ente

k

J cel

l at 3

00 O

hms

/ A m

-2

0.6

0.7

0.8

0.9

AC im

peda

nce

( RA

C) a

t E =

-0.0

5V /

Ohm

cm

2

100

200

300

400

500

600

Current Density (Jcell) at 300 OhmAC impedance in Phosphate at E = -0.05VAC impedance in NaCl at E = -0.05VAC impedance in NaHCO3 at E = -0.05V

Batch performance vs AC impedance from EIS

Steady State Polarisation curves

J / A m-20.0 0.2 0.4 0.6 0.8 1.0 1.2

E cat (

mV

v A

g|A

gCl)

50

100

150

200

250

300

AMI-7001 (AEM) QDPSU (AEM)F-930 (PEM)FTAM-A (AEM)FAA-PEEK (AEM)Rhinohide

Medium ; 0.5g/L CH3COONa, 50mM Phosphate, trace nutrients

AEM for Microbial Fuel Cells

And thank you for listening

From Newcastle MFC group

Group Website http://www.staff.ncl.ac.uk/eileen.yu/