Electrochemically Induced pH Change: Time-Resolved Confocal Fluorescence Microscopy Measurements and Comparison with Numerical Model

TL;DR

This paper introduces the first time-resolved confocal fluorescence microscopy measurements of pH changes near electrodes, comparing experimental data with a reaction-diffusion model and exploring three-dimensional effects and buffer influences.

Contribution

It provides the first time-resolved pH profiles using confocal microscopy and compares them with a numerical model, highlighting three-dimensional effects and buffer impacts.

Findings

Experimental pH profiles agree with the model up to 2D effects

Identification of three-dimensional pH distribution effects

Buffer effects in sulfate electrolytes observed

Abstract

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 yet been provided. 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.