Comparative study of various metal-based reference electrodes

Abstract

This paper compares materials potentially suitable for preparing solid reference electrodes, which could be used in miniaturized flow electrochemical cells. The tested electrodes are based on Sb, Bi, Pd, Pt, and Ag. The stable potential of the reference electrodes was maintained by the pH of the electrolyte, except for the AgCl electrode, whose potential was given by the concentration of chlorides. The performance of the reference electrodes was evaluated through a series of experiments focusing on potential dependences, long-term and short-term stability, cyclic voltammetry, and flow injection analysis with amperometric detection. Potentiometric experiments showed that Sb-based electrodes had the closest slope to theoretical values with minor changes over five weeks. Theory-consistent results of potential dependence were also observed for AgCl electrodes. The results of the voltammetric and flow amperometric experiment suggest that Sb-based reference electrodes are the most suitable tools for electrochemical measurement. AgCl electrodes are limited by the necessity of maintaining a high chloride concentration. Bi-based and PdH electrodes provide unstable results, the latter particularly due to hydrogen desorption. Although able to provide the stable potential to some extent, Pt electrodes are not suitable as the reference electrodes due to the deformation of mainly hydrodynamic voltammograms.