Localized electrochemical impedance spectroscopy: visualization of spatial distributions of the key parameters describing solid/liquid interfaces.

Acquisition of localized electrochemical impedance spectra as a function of spatial coordinates combined with novel approaches of data analysis brings a key for visualization of two-dimensional distributions of important parameters describing solid/liquid interfaces. They include the capacitance of the electric double layer, the resistance of the interfacial charge transfer, capacitances of adsorption, or other parameters depending on the properties of the system. Additionally, the proposed approach eliminates many common methodological problems of localized electrochemical impedance microscopies related to the frequency dependence of the actual pictures and difficulties with raw data interpretation.

4D shearforce-based constant-distance mode scanning electrochemical microscopy.

4D shearforce-based constant-distance mode scanning electrochemical microscopy (4D SF/CD-SECM) is designed to assess SECM tip currents at several but constant distances to the sample topography at each point of the x,y-scanning grid. The distance dependent signal is achieved by a shearforce interaction between the in-resonance vibrating SECM tip and the sample surface. A 4D SF/CD-SECM measuring cycle at each grid point involves a shearforce controlled SECM tip z-approach to a point of closest distance and subsequent stepwise tip retractions.

Electrocatalytic activity of spots of electrodeposited noble-metal catalysts on carbon nanotubes modified glassy carbon.

A strategy for the screening of the electrocatalytic activity of electrocatalysts for possible application in fuel cells and other devices is presented. In this approach, metal nanoclusters (Pt, Au, Ru, and Rh and their codeposits) were prepared using a capillary-based droplet-cell by pulsed electrodeposition in a diffusion-restricted viscous solution. A glassy carbon surface was modified with carbon nanotubes (CNTs) by electrophoretic accumulation and was used as substrate for metal nanoparticle deposition.

Alternating current techniques in scanning electrochemical microscopy (AC-SECM).

Alternating current scanning electrochemical microscopy (AC-SECM) is a growing branch within the variety of SECM methods. This review covers publications involving AC-SECM from its beginning to date. The findings of several research groups are thematically structured along with the specific experimental procedures.

Frequency-dependent alternating-current scanning electrochemical microscopy (4D AC-SECM) for local visualisation of corrosion sites.

For a better understanding of the initiation of localised corrosion, there is a need for analytical tools that are capable of imaging corrosion pits and precursor sites with high spatial resolution and sensitivity. The lateral electrochemical contrast in alternating-current scanning electrochemical microscopy (AC-SECM) has been found to be highly dependent on the frequency of the applied alternating voltage. In order to be able to obtain data with optimum contrast and high resolution, the AC frequency is swept in a full spectrum at each point in space instead of performing spatially resolved measurements at one fixed perturbation frequency.

Frequency dependence of the electrochemical activity contrast in AC-scanning electrochemical microscopy and atomic force microscopy-AC-scanning electrochemical microscopy imaging.

Alternating current mode scanning electrochemical microscopy (AC-SECM) enables local detection of electrochemical surface activity without any redox mediator present in solution. Z-approach curves toward the substrate result in a negative feedback curve of the ac signal for insulating samples. On conducting samples, however, the shape of the feedback curve was found to be dependent on the ac perturbation frequency.

Redox competition mode of scanning electrochemical microscopy (RC-SECM) for visualisation of local catalytic activity.

In order to locally analyse catalytic activity on modified surfaces a transient redox competition mode of scanning electrochemical microscopy (SECM) has been developed. In a bi-potentiostatic experiment the SECM tip competes with the sample for the very same analyte. This leads to a current decrease at the SECM tip, if it is positioned in close proximity to an active catalyst site on the surface.