Realizing Enzymatic Biofuel Cells Through NanoThrough Nano ... · Realizing Enzymatic Biofuel Cells...

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http://www.hnei.hawaii.edu Realizing Enzymatic Biofuel Cells Through Nano-Engineering Realizing Enzymatic Biofuel Cells Realizing Enzymatic Biofuel Cells Through Nano Through Nano - - Engineering Engineering Bor Yann Liaw Bor Yann Liaw Electrochemical Power Systems Laboratory Electrochemical Power Systems Laboratory Hawaii Natural Energy Institute Hawaii Natural Energy Institute School of Ocean and Earth Science and Technology School of Ocean and Earth Science and Technology University of Hawaii at Manoa University of Hawaii at Manoa 1680 East 1680 East - - West Road, POST 109, Honolulu, HI 96822 West Road, POST 109, Honolulu, HI 96822 (808) 956 (808) 956 - - 2339, 2339, [email protected] [email protected] The 4 th US-Korea Forum on Nanotechnology, April 26, 2007, Hawaii

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Realizing Enzymatic Biofuel Cells Through Nano-Engineering

Realizing Enzymatic Biofuel Cells Realizing Enzymatic Biofuel Cells Through NanoThrough Nano--Engineering Engineering

Bor Yann LiawBor Yann Liaw

Electrochemical Power Systems LaboratoryElectrochemical Power Systems LaboratoryHawaii Natural Energy InstituteHawaii Natural Energy Institute

School of Ocean and Earth Science and TechnologySchool of Ocean and Earth Science and TechnologyUniversity of Hawaii at ManoaUniversity of Hawaii at Manoa

1680 East1680 East--West Road, POST 109, Honolulu, HI 96822West Road, POST 109, Honolulu, HI 96822(808) 956(808) 956--2339, 2339, [email protected]@hawaii.edu

The 4th US-Korea Forum on Nanotechnology, April 26, 2007, Hawaii

Enzymatic BioelectrocatalysisEnzymatic Bioelectrocatalysis

G.T.R. Palmore, et al. J. Electroanal. Chem. 443 (1998) 155.

Dehydrogenase Enzymes

Cofactor

Mediator

BV: Benzyl Viologen

6

6H+

Ethanol

Acetaldehyde

ADH

NADH

NAD+

H+

Proton ConductiveMembrane

H2O

½ O2

Anode Cathode

2 H+

BV: Benzyl Viologen

Alcohol BioAlcohol Bio--Fuel Cells Fuel Cells

N.L. Akers et al. Electrochim Acta 50 (2005) 2521

2e-

H+

Diaphorase

2 BV+

2 BV2+

G.T.R. Palmore, et al. J. Electroanal. Chem. 443 (1998) 155.

A Working Ethanol BioA Working Ethanol Bio--FC (EBFC)FC (EBFC)

Fuel in

Oxygen in Fuel out

Oxygen out

Cat

hode

con

t.

Ano

de c

ont.

RENaf

ion

112

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 10 20 30 40 50 60 70

Current (µA/cm2)Po

wer

( µW

/cm

2 )

V. Svoboda et al. (2006)

Issues Critical to EBFCIssues Critical to EBFC

Power Density: Achievable power density is still far below theoretical value

Enhance enzyme loadingMinimize conductive loss

Electronic conductive networkProton pathway

Improve charge transfer efficiencyMinimize transfer stepsPromote direct transfer

Facilitate fluid transportPore structure engineering: surface area vs. porosity •dimensionality • directionality • interconnectivity of pores

Life (Stability)Micro chemical environment engineering

In Situ CharacterizationsIn Situ Characterizations

Enzyme loading: spatial distribution and local (meso-scale) chemical environment

Fluorescence imagingTagged enzymes

Fluorescence polarizationReaction kinetics: temporal resolution

Electrochemical imaging ellipsometry + QCMMass transport

In situ characterization of permeability relative to direction of flowPorosity, pore/channel size, accessible surface area

Need for In Situ CharacterizationsNeed for In Situ Characterizations

In today’s nano-material and bioengineering research, control of materials synthesis and process require fast, non-intrusive, in-situ characterization over a large sample area. For enzymatic biofuel cell applications, such in situ, non-intrusive observations are highly desirable. Example:

Imaging ellipsometry + quartz crystal microbalance (QCM) + electrochemical techniques (e.g., CV, EIS), to study nano-materials and their properties:

Microstructure & surface morphologyReaction kinetics

H+

Electrode KineticsElectrode Kinetics

NADH

NAD+

ADH

CH3CH2OH

CH3COH

e-

SKSV

dtdS

M +•

= max

CH3COH oute

-

CH3CH2OH in

Mass Mass TransferTransfer

They must be calculated

independently

e-

Charge TransferCharge Transfer

NADHNADH

Enzyme Enzyme LoadingLoading

Probing Micro EnvironmentsProbing Micro Environments

Fluorescent laser scanning confocal microscope (LSCM)

images of co-immobilized Alexa-labeled dehydrogenase

(green) and TAMRA-labeled lysozyme (red) in (A) Eastman

AQ 55 (B) chitosan. (Scale bars: 50 µm.)

LSCM images of ADH tagged with Alexa-488 entrapped in (A) Eastman AQ 55 polymer matrix: 2-D slice; (B): 3-D reconstruction from 2-D slices; (C): Nafion: 2-D slice. (Scale bars: 50 µm.) A B C

A. Konash et al. J Mat. Chem. 16 (2006) 4107.

Micro and Nano Materials SynthesisMicro and Nano Materials Synthesis

Develop highly porous conductive polymer matrices:

High enzyme loadingEffective mass transportHighly conductive networkFavorable micro environments for immobilization

Polypyrrole (PPy) porous nano-fabrics, V. Svoboda et al. (2006)

1 µm5 µm

10 µm

e-

Macro & Meso Pore Structure Macro & Meso Pore Structure Engineering Engineering

M. Windmeisser et al. (2006)

Correlation of mean pore size dversus freezing duration

0

20

40

60

80

100

120

140

160

180

0 1 2 3 4 5 6 7 8 9 10

Time (h)d

( µm

)

d

d = -125.8*t^-0.6464+171.4

Scaffolds made from 1 wt% chitosan in 0.4 M acetic acid solution frozen under different durations: (a) 2 h, (b) 4 h, (c) 6 h, and (d) 8 h; scale bars = 200 µm.

a b

c d

DET in PQQDET in PQQ--GDHGDH--ChitosanChitosan--CNTCNT

-0.4 -0.2 0.0 0.2 0.4

-0.4

-0.2

0.0

0.2

0.420 mV/s

b

a

i/µA

E/V(vs.Ag/AgCl)

Kinetic curves of CHIT-CNT and PQQ-GDH-bound CHIT-CNT films in 0.1 M PBS with 0.1 M glucose, 0.8 mM PMS and 0.02 mM DCPIP. Insets: (left) linear fit plot and (right) the absorbance spectra of DCPIP at 600 nm with PQQ-GDH-bound CHIT-CNT film with time

500 550 600 650 700 750

0.2

0.4

0.6

0 1 2 3 40.3

0.4

0.5

0.6

0 1 2 3 4

0.2

0.4

0.6

A

λ/nm

A=0.6394-0.1584*t

CHIT-CNTs

CHIT-CNTs-GDH

A

t/min

νDCIP=0.0111 mM/min

CHIT-CNTs-GDH

CHIT-CNTs

At/min

CV of (a) PQQ-bound CHIT/GCE and (b) PQQ-bound CHIT-CNT/GCE in 0.1 M PBS at 20 mV/s

D.M. Sun et al. (2007)

Imaging Ellipsometry (IE)Imaging Ellipsometry (IE)

1) Locate region-of-interest 2) Real-time laser image

observation via CCD camera

3) Measurement of ∆ and Ψ in spatial distribution (600×400 µm)

Live microscopic laser contrast image( 600 × 400 µm )

Polypyrrole DepositionPolypyrrole Deposition

Electrochemical Deposition & ControlFabrication conditions

Imaging EllipsometryFilm thicknessSurface morphology

Nafion0.5 mA/cm2 1 mA/cm2 2 mA/cm2

V. Svoboda et al. (2005)

PolyPoly--MG Modified SurfaceMG Modified Surface

Nafion V. Svoboda et al. J. Electrochem. Soc. 154 (2007) D113.

Electrochemical Deposition & Control

Fabrication conditionsImaging Ellipsometry

Film thicknessSurface morphology

CV deposition of MG on Pt–0.5 V 1.2 V (vs. Ag/AgCl) Scan rate: 50 mV/sec

Thickness = -0.0074 c3 + 0.1969 c2 + 1.0279 c - 0.1632R2 = 0.9998

0

5

10

15

20

25

30

35

40

0 2 4 6 8 10 12 14 16Cycle #

Thic

knes

s (n

m)

0

10

20

30

40

50

60

70

80

Cum

ulat

ive

Cha

rge

MG Layer ThicknessCumulative Charge

(mA

·sec

·cm

-2)

Electrochem. Microgravimetric IEElectrochem. Microgravimetric IE

WE onQCM

crystal

window

QCM crystal holder

window

Com

pens

ator

Pola

rizer

Laser source

ObjectiveAnalyzer

CCD detector

CE withdegassing channel

RE

QCMSolartron SI 1287

EP3 Imaging Ellipsometer

Maxtek

WE onQCM

crystal

window

QCM crystal holder

window

Com

pens

ator

Pola

rizer

Laser source

ObjectiveAnalyzer

CCD detector

CE withdegassing channel

RE

QCMSolartron SI 1287

EP3 Imaging Ellipsometer

Maxtek

QCM

EP3

CV

Current & Mass ChangesCurrent & Mass Changes

1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6-2

-1

0

1

2

3

4

5

6

d(mass)/dV

Current

Mass

Mas

s (µ

gm뷵

-2)

2.3

- d(m

ass)

/ dV

gm뷵

-2ec븉

-1)

Voltage vs. Ag/AgCl (V)

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

-2.5

M2M5 M4

M3

(MM)

1

M1

Cur

rent

den

sity

(mA

m뷵

-2)

Current & Ellipsometric AnglesCurrent & Ellipsometric Angles

1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6

31.0

31.5

32.0

32.5

33.0

33.5

34.0

34.5

P6P2P4

d(Ψ)/dt

P5P3

P2

P1

Ψ

Current

Ψ (d

eg)

Voltage vs. Ag/AgCl (V)

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Cur

rent

den

sity

(mA

m뷵

-2)

- d(Ψ

) / d

V +

3.2

(de

gec븉

-1)

1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6119

120

121

122

123

124

125

126

127

128

129

d(delta)/dV

Current

Delta

∆ (d

eg)

Voltage vs. Ag/AgCl (V)

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

D2D3

D6 D5

D4

D1

Cur

rent

den

sity

(mA

m뷵

-2)

-2

0

2

4

6

8

d(∆

) / d

V (d

egec븉

-1)

Reduction of MG to Reduction of MG to ll--MGMG

In the reduction phase: the mass deposition was driven by adsorption, followed by electrochemical reduction of MG to l-MG

Faraday’s law

)(•

)(

)(•

••

0

tinF

Mdttdm

dttinF

Mm

QnF

Mm

T

=

=

=

Ads

orpt

ion

Red

uctio

n of

MG

Mass & Mass & ∆∆

The progression of ∆ and d(∆)/dt follows mass changes.

Mass, Current, & Mass, Current, & ΨΨ

The progression of Ψ and d(Ψ)/dt reflect both mass and chemical changes in the film.

ConclusionConclusion

Enzymatic bio-fuel cells need delicate optimization of electrode fabrication, which requires pore structure engineering, from macro- to meso-scale.Nano-material synthesis and electrode fabrication require in situ observations and non-intrusive characterizations of the process.Several intriguing in situ characterization techniques were demonstrated of their utility:

Fluorescence and polarizationImaging ellipsometry + QCM + Electrochem. tech.Microporometry

Dynamic transient observations mechanistic details

Thank you for your attention!Thank you for your attention!

AcknowledgementsAcknowledgements

Funding Support:ONR, Hawaii Environmental and Energy Technologies (HEET) initiative (R. Rocheleau, PI)DCI Postdoctoral Fellow Research ProgramAFOSR, MURI Program (P. Atanassov, PI)

Contributors:Faculty: Michael Cooney, David Jameson, Shelley MinteerPostdocs: Wayne Johnston, Forest Quinlan, Vojtech Svoboda, Stacey Konash, Dongmei Sun, Daniel ScottStudents: Chris Rippolz, Mona Windmeisser, Swati Nagpal, Ruey Hwu, Eric Brown