This study describes the gas-sensing properties of a La2CuO4/yttria-stabilized zirconia (YSZ)/Pt potentiometric sensor and discusses its sensing mechanism in terms of the adsorptive and catalytic behavior of the electrode materials. The sensor is highly sensitive to NO, CO, and NO2, but virtually no response is observed for CO2 and O-2 detection. Optimal NO sensing is obtained at similar to 450 degrees C. Above 500 degrees C, there is an abrupt decrease in sensitivity. Below 400 degrees C, there is a saturation of the response. The sensor is NO selective against O-2, but its sensitivity is affected significantly by CO2 and CO. This selectivity behavior is in good agreement with temperature-programmed desorption results, indicating that the NO response is very likely adsorption-related. For example, the NO chemisorption peak disappears in the presence of CO2, which agrees with the sensor results showing a significant decrease in the NO sensitivity by CO2 addition even though CO2 itself shows no sensor response. (C) 2007 The Electrochemical Society.