No abstract

The reproducible fabrication of nanometre-sized carbon electrodes poses great challenges. Especially, the field of single entity electrochemistry has strict requirements regarding the geometry of these electrochemical probes. Herein, an automated setup for the fabrication of carbon nanoelectrodes based on the pyrolysis of a propane/butane gas mixture within pulled quartz capillaries by means of a moving heating coil is presented. It is shown that mere electrochemical characterisation with conventional redox mediators does not allow for a reliable assessment of the electrode's geometry and quality. Therefore, highthroughput transmission electron microscopy is used in parallel to evaluate and optimise preparation parameters. Control of the latter gives access to three different electrode types: nanopipettes, nanosamplers and nanodisks.

A spectroelectrochemical cell is presented that allows investigations of electrochemical reactions by means of attenuated total reflection infrared (ATR-IR) spectroscopy. The electrode holder for the working (WE), counter and reference electrode as mounted in the IR spectrometer cause the formation of a thin electrolyte layer between the internal reflection element (IRE) and the surface of the WE. The thickness of this thin electrolyte layer (d) was estimated by performing a scanning electrochemical microscopy-(SECM) like approach of a Pt microelectrode (ME), which was leveled with the WE toward the IRE surface. The precise lowering of the ME/WE plane toward the IRE was enabled by a micrometer screw. The approach curve was recorded in negative feedback mode of SECM and revealed the contact point of the ME and WE on the IRE, which was used as reference point to perform the electro-oxidation of ethanol over a drop-casted Pd/NCNT catalyst on the WE at different thin-layer thicknesses by cyclic voltammetry. The reaction products were detected in the liquid electrolyte by IR spectroscopy, and the effect of variations in d on the current densities and IR spectra were analyzed and discussed. The obtained data identify d as an important variable in thin-layer experiments with electrochemical reactions and FTIR readout.

The integration of a scanning Kelvin probe (SKP) and a scanning electrochemical microscope (SECM) into a single SKP-SECM setup, the concept of the proposed system, its technical realization, and first applications are presented and discussed in detail. A preloaded piezo actuator placed in a grounded stainless steel case was used as the driving mechanism for oscillation of a Pt disk electrode as conventionally used in SECM when the system was operated in the SKP mode. Thus, the same tip is recording the contact potential difference (CPD) during SKP scanning and is used as a working electrode for SECM imaging in the redox-competition mode (RC-SECM). The detection of the local CPD is established by amplification of the displacement current at an ultralow noise operational amplifier and its compensation by application of a variable backing potential (V(b)) in the external circuit. The control of the tip-to-sample distance is performed by applying an additional alternating voltage with a much lower frequency than the oscillation frequency of the Kelvin probe. The main advantage of the SKP-SECM system is that it allows constant distance measurements of the CPD in air under ambient conditions and in the redox-competition mode of the SECM in the electrolyte of choice over the same sample area without replacement of the sample or exchange of the working electrode. The performance of the system was evaluated using a test sample made by sputtering thin Pt and W films on an oxidized silicon wafer. The obtained values of the CPD correlate well with known data, and the electrochemical activity for oxygen reduction is as expected higher over Pt than W.