A macro three‐electrode cell which employs a thin Nafion ionically conductive film which is contacted by a moist gas is described. In contrast to the modified electrodes concept, the experiments described here were conducted with no contacting electrolyte solution. Also, the Ag wire pseudo reference electrode used in previous studies was replaced by a polymeric
normalNafion‐normalAg/normalAgCl
reference electrode. It enabled the measurement of stable redox potentials for various compounds (+0.27, +0.37, and −0.21V for
K3normalFefalse(CN)6
,
K3Wfalse(CN)8
, and
normalRufalse(NH3)6Cl3
, respectively) and close to those measured for the same compounds when dissolved in aqueous solutions using a conventional
normalAg/normalAgCl
reference electrode (+0.30, +0.34, and −0.23V, respectively). The overpotential for the reduction of
O2
using electropolymerized cobalt tetra(o‐amino‐phenyl)porphyrin was reduced by 280 mV in the present configuration compared to the previous one in which we used polyethylene oxide films and a Ag wire pseudo reference electrode (
E1/2=+0.25 normaland−0.03Vnormalvs.normalAg/normalAgCl
, respectively).
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.
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