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Electrochemical evaluation of pyrolysed high-aspect ratio 3D electrodes for biofuel cell
applications
Amato, Letizia; Hansen, Rasmus J.; Tenje, Maria; Ortiz, Roberto; Gorton, Lo; Keller, Stephan Sylvest;
Heiskanen, Arto; Boisen, Anja; Emnéus, Jenny
Publication date:
2012
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Publisher's PDF, also known as Version of record
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Citation (APA):
Amato, L., Hansen, R. J., Tenje, M., Ortiz, R., Gorton, L., Keller, S. S., ... Emnéus, J. (2012). Electrochemical
evaluation of pyrolysed high-aspect ratio 3D electrodes for biofuel cell applications. Poster session presented at
63rd Annual Meeting of the International Society of Electrochemistry, Prague, Czech Republic.
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Electrochemical Evaluation
Electrochemical Evaluation
n of Pyrolyzed High Aspect n of Pyrolyzed
High Aspect
Ratio
Ratio 3D Electrodes for B
i 3D
3 Electrodes
l
d for
f Biofuel
Bi f l Cell Applications
C ll Applications
Cell
li i
Letizia Amato1, Rasmus J. Hansen
Letizia Amato
Rasmus J Hansen1, Maria Tenje
Maria Tenje2, Roberto O
Roberto Ortiz
O 3, Lo Gorton
Lo Gorton3, Stephan S. Keller
Stephan S Keller1, Arto Heiskanen
Arto Heiskanen1, Anja Anja
Boisen1, Jen
Jen
nny Emnéus1
nny Emnéus
1 Technical University of Denmark, Department of Micro
Technical University of Denmark Department of Micro‐
and Nanotechnology, Denmark; and Nanot
echnology Denmark; 2 Department of Measurement Technology and Department of Measurement Technology and
Industrial Electrical Engineering, Lund University, Sweden; d
l l
l g
g,
d
y,
d ; 3 3 Center for Molecular Protein Science, Lund University, Sweden
C
f
l l
,
d
y,
d
• One
O way to
t increase
i
th performance
the
f
off a biofuel
bi f l cellll is
i to
t maximize
i i e the
th surface
f
area off the
th anode
d and
d cathode.
th d An
A interdigitated
i t di it t d set‐up
t
allows a serial configuration of alternating anode and cathode and,
and additionally,
additionally could result in faster electron transfer due to the close
proximity of the two half cells. Therefore a further optimization of thee power and energy output is expected.
• Carbon
C b 3D electrodes
l t d can be
b fabricated
f b i t d using
i g a carbon
b MEMS tech
t hnique
h iq in
i a veryy simple
i pl high
high yyield
i ld p
process [[1].
[1]] Carbonizable
C b i bl p
polymers
ly
are widely available and are typically much less expensive than metaals used in thin film metal electrode fabrication.
fabrication Additionally,
Additionally carbon
has a wider electrochemical potential window than gold and platinum
m [2],
[2] which is useful in e.g.
e g biosensor applications.
applications
• In this work,
work we compare the electrochemical performance of planaar interdigitated electrodes (2D IDEs) and the same IDE configuration
with high aspect ratio carbon pillars (3D IDEs), using cyclic voltammetrry and electrochemical impedance spectroscopy.
Both 2D and 3D IDEs were obtained by pyrolysis of lithographically
defined negative photoresist SU
SU‐8.
8. A two
two‐step
step photolithography
process was used
p
d to
t p
pattern
tt
th high
the
high aspect
p t ratio
ti p
pillars
ill on the
th IDEs,
IDE ,
1 4 µm and aspect ratio ~8.
~8
resulting in a diameter of 1.4
(1) Cr/Au alignment marks
(1) Cr/Au alignment marks
SiO2
S
Si
(2) 2D layer: SU8 2005 spin‐coating and masked irradiation (140 mJ/cm
(2)
2D l
SU8 2005 i
ti
d
k d i di ti (140 J/ 2)
((3) 3D layer: SU8 2075 spin‐coating and masked irradiation (150 mJ/cm
)
y
p
g
(
/ 2)
CVs of 1 mM ruthenium (II/III) hexamine
chloride in PBS (pH 7) at different scan
rates on 2D and
d 3D carbon
b
electrodes
l
d
(p
g/ g
(potentials vs. Ag/AgCl
reference
electrode)
electrode).
• Interestingly
Interestingly, the semi‐circle in the Nyquist plots seems to depend
on the bulk properties of pyrolysed carbon, not on the solution
i t i i electroactive
l t
ti behaviour
b h i
th
composition,
p iti , suggesting
gg ti g an intrinsic
off the
material.
material
• The electrodes showed resistance increase due the thin and long
l d off the
leads
h electrode
l
d design.
d g
3D high
hi h aspectt ratio
ti pillars
ill
h
have
i t i i ll hydrophobic
intrinsically
h d h bi
properties due to their geometry.
geometry Furthermore,
Furthermore the surface
chemistry of pyrolysed carbon contributes to the hydrophobicity
off the
h 3D electrodes.
l
d In
I order
d to increase
i
the
h wetting,
i g, the
h carbon
b
surface was electrochemically modified with carboxylic groups by
diazonium salt chemistry.
chemistry The carboxylic acid modification of the
pillars resulted in 60% increase in the peak current indicating that
th wetting
the
tti off the
th pillars
ill was successful.
f l
l p
lp
dy g
((4) Development & critical point drying
)
(5) Pyrolysis at 900
C in N
(5) Pyrolysis at 900°C
in N2 atmosphere
BEFORE PYROLYSIS
Nyquist plots for 2D and 3D carbon
electrodes
l
d
i 1mM
in
1 M ruthenium
h i
(II/III)
hexaammine ((RUT)) and PBS p
pH7. Inset:
zoom‐in
zoom
in of the impedance spectra for IDE.
CVs
CV off 5 mM
M dopamine
d
i in
i PBS
(pH7)) on py
(p
pyrolysed
y
carbon
pillars: carboxylic acid
acid‐modified
modified
(blue) and bare (red) (potentials
vs. Ag/AgCl
A /A Cl RE and
d sweep rate:
t
50 mV/s).
)
AFTER PYROLYSIS
• The resistivity issue related to the patterned 2D structures is
being studied further.
further
• The
Th wetting
i g off the
h 3D electrodes
l
d can be
b increased
i
d by
by carboxylic
b yli
acid modification of the carbon surface.
surface
• This high aspect ratio carbon MEMS electrode will be excellent for
biofuel cells applications and for electrochemical biosensing.
SEM images of interconnected 3D pillars on interdigitated structures before (left) and after
pyrolysis (right).
References
[1] Wang,
Wang C.,
C Jia,
Jia G.,
G Taherabadi,
Taherabadi L.
L H.,
H Madou,
Madou M.
M J.,
J J.
J Microelectromech.
Microelectromech Syst.
Syst 14 (2005) 348.
348
[[2]] R. L. McCreery,
y, in A. Bard Ed.,, Electroanalytical
y
Chemistry,
y, Vol. 7,, Marcel Dekker,, NY,, 1991.