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
TU Dresden Institut für Physikalische Chemie und Elektrochemie

2. TU Dresden Institut für Physikalische Chemie und Elektrochemie
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
TU Dresden Institut für Physikalische Chemie und Elektrochemie

3. Electrochemical Reactions
Influence on electron transfer kinetics ?
Influence on mass transport
MHD effect 
Gradient effects 
Influence on surface diffusion/crystallization ?
TU Dresden Institut für Physikalische Chemie und Elektrochemie

4. Copper dissolution in microstructuresAE Va GE B
VIa
MHD-effect
B  E
Lorentz-Force FL +
natural convection Fconv
unstirred
stirred
Magnetic field on
TU Dresden Institut für Physikalische Chemie und Elektrochemie

5. Copper dissolution in microstructuresAE
IIIa GE B
IVa
MHD-effect
B  E
Paramagnetic
gradient Force Fgrad
unstirred
stirred
TU Dresden Institut für Physikalische Chemie und Elektrochemie

6. Charge transfer reaction
Butler- Volmer- Equation:
(i: current density; i0: exchange current density; D : overvoltage ; z: number of electrons; : transfer coefficient; F: Faraday´s constant; R: universal gas constant; T: absolute temperature)
TU Dresden Institut für Physikalische Chemie und Elektrochemie

7. Electrochemical Quartz Crystal Microbalance (EQCM)
Counter
electrode
Reference
Electrode
Hg/ Hg2Cl2
Cell
Quartz
Potentiostat RE CE WE
Network analyser
Working N S
Computer
TU Dresden Institut für Physikalische Chemie und Elektrochemie

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
quartz
gold electrodes
film
shear motion
Layer 2
9,997
9,998
9,999
10,000 20 40 60 80
100
Quartz with
Rigid Layer
Unloaded
Quartz
Damping Layer
Real Part
of Admittance / mS
f / MHZ f f
R,Layer 1
R,0 w
Layer 1 w f
R,Layer 2 w
Sauerbrey equation:
Complex frequency shift
Mass
Damping
CSB: Sauerbrey constant
TU Dresden Institut für Physikalische Chemie und Elektrochemie

9. Galvanostatic deposition
Deposition of Nickel
Galvanostatic deposition
2 H+ + 2e-  H2
Ni2+ + 2e-  Ni
Small Current Density (E1)
iNi(B)iNi(B=0)
iH2(B)>iH2(B=0)
 Current efficiency decreases
High Current Density (E2)
iNi(B)>iNi(B=0)
 Current efficiency
not affected by B
 B=0
   B>0
TU Dresden Institut für Physikalische Chemie und Elektrochemie

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
TU Dresden Institut für Physikalische Chemie und Elektrochemie

11. Deposition of Polypyrrole (PPy) orientation-effect at
delocalized π-bonds
doping with anions (A-)
Electrical conductivity
A- =
perchlorate ClO4-
A- =
p-toluenesulfonate TsO-
smooth layers
rough layers
MFD-effect
at PPy|ClO4-
orientation-effect at
PPy|TsO-
TU Dresden Institut für Physikalische Chemie und Elektrochemie

12. Cyclovoltammetry 10mV/s 5 cycles at B= 0T in monomer free solution
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
TU Dresden Institut für Physikalische Chemie und Elektrochemie

13. TU Dresden Institut für Physikalische Chemie und Elektrochemie
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- (Polypyrrole|Perchlorate-Anions) and orientation effect (Polypyrrole|p-toluenesulfonate-Anions) at conducting polymers
TU Dresden Institut für Physikalische Chemie und Elektrochemie

14. TU Dresden Institut für Physikalische Chemie und Elektrochemie
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)
TU Dresden Institut für Physikalische Chemie und Elektrochemie

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!
TU Dresden Institut für Physikalische Chemie und Elektrochemie