A Temperature and Electrochemical Impedance Spectroscopy Analysis of Nickel Electrocrystallization from a Watts Solution

Impedance Analysis of Electrochemical Systems

Interpretation of impedance spectroscopy data requires both a description of the chemistry and physics that govern the system and an assessment of the error structure of the measurement. The approach presented here includes use of graphical methods to guide model development, use of a measurement model analysis to assess the presence of stochastic and bias errors, and a systematic development of interpretation models in terms of the proposed reaction mechanism and physical description. Application to corrosion, batteries, and biological systems is discussed, and emerging trends in interpretation and implementation of impedance spectroscopy are presented.

Surface Influences on the Electrodiffusive Behavior in Mesoporous Templates

The physicochemical details of the well-established template-assisted electrodeposition process for metal nanowire fabrication are investigated with respect to the physical origination for template geometry limitation. The overall process of metal reduction inside anodized Al2 O3 (AAO) is divided into three parts: i) the electrochemical reduction at the pore bottom, ii) the diffusion of the electrolytic species, and iii) the capacitive interaction between pore surface and electrolyte. The results show that the reduction of Ni is controlled by the degree of electrode recession, i.e., the pore depth. Applying Cottrell's equation to pulsed electrodeposition enables experimental access to diffusion coefficients (DNi2+). This gives a gradient in DNi2+ along with the filling process. The switch-over from crystallization to diffusion control is investigated to depend on temperature and pore length. Additionally, the electrode surface capacitance scales non-linearly with the pore depth. This is deduced as a consequence of electrostatic surface-electrolyte interaction. A minimum in the electrode capacitance at a pore length of 48 μm is identified as the point with maximum thickness of a double-layer-type surface effect to the electrolyte. The results extend the template's role from simply geometrically limiting metal growth and explain occurring process issues when filling especially high-aspect-ratio pores.

Graphical Analysis of Electrochemical Impedance Spectroscopy of Two Consecutive Irreversible Electron Transfers. 1. Theoretical Study of the Anodic Dissolution of Metals

A general function for the faradaic impedance associated to a two consecutive single electron transfer mechanism followed by a irreversible first-order step has been obtained on the basis of formal kinetics. Kinetic parameters associated to this reaction mechanism can be obtained from the different kind of plots of the impedance function: Nyquist, Cole-Cole, and different Bode plots. A strategy for obtaining all parameters is suggested and analyzed on a detailed flowchart.