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The electrochemical oxidation and re‐reduction of N′,N′,N,N‐tetrahexylphenylene diamine (THPD) deposited in form of microdroplets on a basal plane pyrolytic graphite or gold electrode is shown to be a chemically reversible process in the presence of aqueous electrolyte media containing NO3−, SCN−, ClO4−, or PF6−. Sharp voltammetric responses with a mid point potential, Emid, characteristic of the type of anion and its concentration are observed. The oxidation product, an ionic liquid, undergoes rapid ion exchange when the anion of the aqueous electrolyte is exchanged with anions of lower Emid replacing anions of higher Emid. Although the effect of the supporting electrolyte cation in the case of the alkali metals K+, Na+, and Li+ is not significant, a considerable change in the voltammetric peak shape and Emid occurs in the presence of protons. This effect, attributed to the protonation of THPD, is also sensitive to the type of anion present with anions of lower Emid causing more facile protonation. After protonation of THPD, oxidation and re‐reduction can be shown to be associated with H+ expulsion and uptake. Deposited onto the rough surface of a gold coated planoconvex quartz crystal oscillator the [THPD+ClO4−]oil deposit can be observed in form of micron‐sized droplets in SEM images. A strong frequency response of the crystal oscillator in an electrochemical quartz crystal microbalance experiment associated with the oxidation and re‐reduction of THPD can be detected but is not related to changes in mass. Rather, this frequency response may be attributed to changes in the viscosity and/or coverage of the oily deposit.

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The effect of high-intensity laser pulses on the reduction of methyl viologen at glassy carbon electrodes in aqueous solution is investigated using laser activation voltammetry (LAV) under both channel flow and no-flow conditions and compared with the effect of conventional variable-temperature voltammetry. The reduction proceeds in two consecutive one-electron steps, and the neutral two-electron-reduction product of methyl viologen is shown by voltammetry and in situ optical microscopy to form two types of deposits, amorphous and crystalline, on the electrode surface. Laser activation voltammetry using a 10 Hz pulsed Nd-YAG 532 nm laser is shown to remove the deposits from the electrode surface at different laser intensities: the amorphous material is more easily ablated than the crystalline deposit. By conventional variable-temperature voltammetry, it is shown that the two stripping peaks disappear as the temperature is increased. However, with conventional heating, the opposite ease of removal is detected compared to the case of laser activation voltammetry: the stripping response associated with the crystalline material disappears at lower temperatures compared to that for the amorphous material. In the presence of high-intensity laser pulses (>0.17 W cm(-2)), glassy carbon surfaces are damaged and the voltammetric characteristics become poor. It is shown that, by the employment of a thin-film boron-doped diamond electrode grown using a chemical vapor deposition procedure on a tungsten substrate, much higher laser intensities can be applied and well-defined LAV signals can be obtained without deactivation of the electrode.

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