Influence of moisture on potentiometric Cl2 gas sensor using a Na+ conducting solid electrolyte

The influence of moisture in a test gas containing Cl-2 was investigated for a Cl-2 gas sensor using a NaCl-RuO2 mixed measuring electrode and a composite Na+ conductor of sodium superionic conductor, 40 wt % (Na2O-Al2O3-4SiO(2)). For dried Cl-2 gas, the electron number (n) for the reaction on the electrodes was 1.86 which was very close to the theoretical value n=2.0. When water vapor was added to the Cl-2 measuring gas, the electromotive force (emf) significantly decreased, since the Cl-2 gas concentration was reduced by the reaction with the H2O gas. Based on the calibration curve observed from the relationship between emf and Cl-2 concentration at 450degreesC under dry conditions, it is suggested that the sensor can determine parts per billion levels of Cl-2 gas under ambient conditions. Experimentally, the observed response time became faster with an increase in the flow rate and mainly depended on the exchange time of the test gas. (C) 2002 The Electrochemical Society.