Conductivity response of porous electrodes supported on perfluorosulfonic acid membranes to acidic gas mixtures.

Gold or platinum films deposited on a Nafion membrane were used to measure surface conductance of the membrane. Acidic gases such as HCI or SO2, introduced as mixtures with an inert gas, were found to affect the conductance of the membrane surface facing this mixture while the other side of the membrane was constantly supplied with a moist inert gas. The relative conductance (G/Go) is most affected within the 0-0.5 and 3-4.5 vol % ranges both for HCI and SO2. The effect is higher for the Pt-deposited than it is for the gold-deposited membrane: for an HCI concentration of 1.5 vol %, G/Go is 5 for Pt deposited on Nafion while it is only 1.3 for gold deposited on Nafion. This is attributed to different geometries and porosity of the Pt and Au electrodes. No conductance response was observed for CO2 which yields with water a much weaker acid than those formed by HCI and SO2.