Confocal
fluorescence microscopy is a proven technique, which can
image near-electrode pH changes. For a complete understanding of electrode
processes, time-resolved measurements are required, which have not
been achieved previously. Here we present the first measurements of
time-resolved pH profiles with confocal fluorescence microscopy. The
experimental results compare favorably with a one-dimensional reaction–diffusion
model; this holds up to the point where the measurements reveal three-dimensionality
in the pH distribution. Specific factors affecting the pH measurement
such as attenuation of light and the role of dye migration are also
discussed in detail. The method is further applied to reveal the buffer
effects observed in sulfate-containing electrolytes. The work presented
here is paving the way toward the use of confocal fluorescence microscopy
in the measurement of 3D time-resolved pH changes in numerous electrochemical
settings, for example, in the vicinity of bubbles.
The measurement of pH near electrodes is relevant to all electrochemical reactions in aqueous solutions. In this context, confocal fluorescence microscopy is a proven technique, that can image near-electrode pH changes; however time resolved measurements, critical for a complete understanding of electrode processes, are required. In this work, for the first time we measure time resolved pH proles formed near electrodes with confocal uorescence microscopy. Specific factors aecting the pH measurement such as attenuation of light and the role of dye migration are discussed in detail. Using the pH-sensitive dye fluorescein, we measure the proton depletion zone formed due to oxygen reduction on a platinum electrode. Experimental results compare favorably with a onedimensional reaction-diusion model. This holds up to the point where the measurements reveal 3-dimensionality in the pH distribution. The method is further applied to analyse the buer eects observed in sulphate-containing electrolytes. The work presented here is paving the way towards the use of confocal uorescence microscopy in the measurement of 3D time resolved pH changes in numerous electrochemical settings, e.g. in the vicinity of bubbles.
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