Design and testing of a novel miniaturized palladium reference electrode

Introduction

In a typical electrochemical cell, the interesting reactions usually take place at the working electrode. Therefore, electrochemists are usually interested in the current from or the potential over the working electrode. However, potentials are not absolute quantities. They need to be defined versus another, preferably fixed and known, reference potential. In electrical engineering potentials are often defined versus ground. In electrochemical systems this does not apply, and a separate reference electrode is required.

Macro-scale reference electrodes

Two of the frequently used reference electrodes are the Silver/Silverchloride and the saturated calomel electrode. These two types of reference electrodes show excellent behavior in terms of potential stability and ease of use. However, the design of these macro-scale reference electrodes does not lend itself for miniaturization.

So far, a miniaturized reference electrode for Lab-on-Chip systems with the same specifications as the macro-scale equivalents is not available.

Miniaturized (pseudo) reference electrodes

A poor-mans solution is to use a pseudo-reference electrode in Lab-on-Chip systems. This pseudo reference electrode is often sensitive to one or more ions present in solution. A changing concentration of these ions, will change the potential of the reference electrode undesirably. One of the materials that can be used for a pseudo-reference electrode is palladium, which shows sensitivity for changing proton (H⁺) concentrations and is therefore pH sensitive. Palladium can store protons into its crystal lattice, providing a means of keeping a more constant proton concentration at its surface.

Goal of this assignment

Design and testing of a miniaturized reference electrode based on palladium, while minimizing the effects of changing proton concentrations.

Please contact one of the two persons below if you are interested in this assignment.