Development of an enhanced porosity AgAgCl reference electrode with improved stability

Abstract

We have developed a new low-cost method for fabrication of an enhanced porosity ultra-low noise silver-silver chloride (Ag-AgCl) reference electrode with dramatically high stability, useful in precise electrochemical and biomedical measurements. Low noise level and high stability are the most important features when evaluating reference electrode for example when used as a half-cell at electrochemical cells. The noise was measured for bare Ag-AgCl electrode pairs in a saline electrolyte without any junction. The noise spectral density for such measurements increases at low frequencies due to flicker (1/f) noise. Thermal noise from the real part of the electrode impedance is always lower than 1/f noise and is shown as offset voltage in noise spectrum. Electrode noise is highly correlated to its offset voltage. Moreover, the variance of the potential difference in our measurements is correlated to the noise level of electrodes. In this paper, offset voltage spectrum and the variance of data while doing measurements are proposed for identification of noise in our electrodes. The results presented suggest a new low-cost process for fabrication of enhanced porosity reference electrodes with nanovolt noise level at 1 Hz, low enough for electrochemical and biomedical measurements.