Magnetic%20field%20influences%20on%20electrochemical%20processes

1
Magnetic field influences on electrochemical
processes

• Silvio Köhler, Andreas Bund, Holger H. Kühnlein,
  Adriana Ispas, Waldfried Plieth

SFB 609, C5 Magnetic Field Control of Metal
Deposition
2
Motivation and Aim

• to find out
• How does a magnetic field influence the several
  parts of an electrochemical reaction?
• to describe
• explaining of phenomena and creation of an
  experimental basis for numerical simulations
• to tailor
• combinations of electric and magnetic fields for
  deposition of functionalized layers with defined
  properties and improving the mass transport in
  micro and nano structures, respectively

3
Electrochemical Reactions
Influence on electron transfer kinetics ?
Influence on mass transport MHD effect ? Gradient
effects ?
Influence on surface diffusion/crystallization ?
4
Copper dissolution in microstructures
MHD-effect B ? E Lorentz-Force FL natural
convection Fconv
Magnetic field on
5
Copper dissolution in microstructures
MHD-effect B ?? E Paramagnetic gradient Force
Fgrad
6
Charge transfer reaction
Butler- Volmer- Equation
(i current density i0 exchange current
density ?D overvoltage z number of
electrons ? transfer coefficient F Faradays
constant R universal gas constant T absolute
temperature)
7
Electrochemical Quartz Crystal Microbalance (EQCM)
8
Experimental Technique (EQCM)

• in situ measurements of the mass changes at
  electrode surfaces during electrodeposition
• its functionality is based on the converse
  piezoelectric effect

f
f
R,Layer 1
R,0
w
w
Layer 1
0
f
R,Layer 2
w
Sauerbrey equation
Complex frequency shift
CSB Sauerbrey constant
9
Deposition of Nickel
Galvanostatic deposition
Ni2 2e- ? Ni
2 H 2e- ? H2
Small Current Density (E1) iNi(B)?iNi(B0) iH2(B)gt
iH2(B0) ? Current efficiency decreases High
Current Density (E2) iNi(B)gtiNi(B0) iH2(B)gtiH2(B
0) ? Current efficiency not affected by B
? ? ? Bgt0
?? B0
10
Morphology and Roughness
Atomic Force Microscopy
B 0 mT, i-50 mA cm2 i(H2)-12.9 mA cm-2 Small
damping change
B 740 mT, i-50 mA cm2 i(H2)-7.8 mA cm-2 Large
damping change
Ra mean roughness Lx, Ly dimension of the
surface f(x,y) relative surface to the central
plane
11
Deposition of Polypyrrole (PPy)
MFD-effect at PPyClO4-
orientation-effect at PPyTsO-
12
Ion Exchange
Cyclovoltammetry 10mV/s 5 cycles at B 0T in
monomer free solution

• Exchange of anions
• No visible differences in
• Exchange behavior.

• Exchange of cations
• Exchange suppressed in the case of
• magnetopolymerized Polypyrrole

13
Conclusions

• Influence on mass transport by Lorentz-Force
  (MHD-effect) and paramagnetic-gradient- Force
• No influence on charge transfer kinetic
• Magnetic field induces changes in surface
  roughness (nickel deposition)
• MHD- (PolypyrrolePerchlorate-Anions) and
  orientation effect (Polypyrrolep-toluenesulfonate
  -Anions) at conducting polymers

14
Outlook

• Investigation of mass transport in
  microstructures including diamagnetic ions (Zn2,
  Ag)
• ?model system for numerical simulations
• Deposition of alloys with different magnetic
  properties (NiFe)
• Investigation of the magnetic field influences on
  the conductivity and dopand exchange kinetic of
  conducting polymers (Polypyrrole in combination
  with several anions)

15
Acknowledgements
The authors are grateful to SFB 609 (Institution
of German Research) for the financial support and
Sino-German Scientific Center for the invitation
to the workshop.
Thank you for your attention!