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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. Motivation and Aim. to find out

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Magnetic field influences on electrochemical processes

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


Motivation and aim
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


Electrochemical reactions
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


Copper dissolution in microstructures

Va

VIa

B

B

RE

RE

AE

GE

GE

AE

unstirred

stirred

Copper dissolution in microstructures

MHD-effect

B  E

Lorentz-Force FL +

natural convection Fconv

Magnetic field on

TU Dresden Institut für Physikalische Chemie und Elektrochemie


Copper dissolution in microstructures1

IIIa

IVa

B

B

RE

RE

GE

GE

AE

AE

unstirred

stirred

Copper dissolution in microstructures

MHD-effect

B  E

Paramagnetic

gradient Force Fgrad

TU Dresden Institut für Physikalische Chemie und Elektrochemie


Magnetic field influences on electrochemical processes

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


Magnetic field influences on electrochemical processes

Reference

Electrode

Hg/ Hg2Cl2

RE

CE

WE

Counter

electrode

Potentiostat

Cell

Computer

N

S

Working

electrode

Quartz

Networkanalyser

Electrochemical Quartz Crystal Microbalance (EQCM)

TU Dresden Institut für Physikalische Chemie und Elektrochemie


Magnetic field influences on electrochemical processes

Quartz with

Unloaded

Rigid Layer

Quartz

100

film

80

60

gold electrodes

Quartz with

of Admittance / mS

Real Part

40

Damping Layer

20

Damping

Mass

Layer 2

0

shear motion

9,997

9,998

9,999

10,000

quartz

f / MHZ

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

Sauerbreyequation:

Complex frequency shift

CSB: Sauerbrey constant

TU Dresden Institut für Physikalische Chemie und Elektrochemie


Magnetic field influences on electrochemical processes

Deposition of Nickel

Galvanostatic deposition

Ni2+ + 2e- Ni

2 H+ + 2e- H2

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)

iH2(B)>iH2(B=0)

 Current efficiency

not affected by B

 B=0

   B>0

TU Dresden Institut für Physikalische Chemie und Elektrochemie


Magnetic field influences on electrochemical processes

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

Ramean roughness

Lx, Ly dimension of the surface

f(x,y) relative surface to the central plane

TU Dresden Institut für Physikalische Chemie und Elektrochemie


Magnetic field influences on electrochemical processes

Deposition of Polypyrrole (PPy)

  • 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


Magnetic field influences on electrochemical processes

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


Conclusions
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


Outlook
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


Acknowledgements
Acknowledgements

The authors are grateful to SFB 609 (Institution of German Research) for the financial supportand Sino-German Scientific Center for the invitation to the workshop.

Thank you for your attention!

TU Dresden Institut für Physikalische Chemie und Elektrochemie