Deards, Paul Graham (1999) Novel transparent microelectrodes for photoelectrochemistry. University of Southampton, Doctoral Thesis.
Abstract
Electrochemistry is a proven kinetic tool and should be a popular probe of photochemistry. However, conventional electrodes suffer inherent limitations that restrict the range of photochemical systems open to investigation. This work brings together three technologies - microelectrodes, optically transparent electrode materials, and photolithography - to overcome some of these limitations.
This thesis describes a series of arrays of tin-doped indium oxide (ITO) recessed microsdisc electrodes, fabricated using photolithography. The devices range from a hexagonal array of 96 x 25 μm radius discs to one of 2080 x 5 μm radius discs. Photolithography is also used to fabricate an array of 11 individually addressable ITO microband electrodes of width 25 μm, spaced 55 μm apart. Electrochemistry at both types of device is in accord with theory.
Photoexperiments are reported at both devices using ruthenium (II) photosystems. In continuous irradiation experiments, the microdisc arrays gave a higher photocurrent density than found at conventional electrodes, and the density increased with decreasing electrode radius. In a flash photolysis experiment, the transient response at the microdisc device is much faster than at a conventional electrode because the double layer charging contribution is less significant. Finally, the microband array devices are used to demonstrate 'generator/collector' experiments where photocurrent generation at a single band is affected by electrochemical reactions at flanking bands.
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