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

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

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 AE 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

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

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

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

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

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

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

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

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

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

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

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