Effect of nanocomposite Au–YSZ electrodes on potentiometric sensor response to NOx and CO

The solid-state potentiometric sensor responses of high surface area nanocomposite and low surface area gold sensing electrodes were compared. The composite nature of the high surface area gold and stabilized zirconia electrode preserved average gold particle size of 62 nm after calcination and sintering. The electrochemical sensor response of up to 300 ppm CO, NO2 or NO gas in the presence of 3% O2 (balance N2) was measured. Sensors using the low surface area Au electrodes had a larger sensitivity to all test gases, more than twice the sensitivity to CO and NO2, than the high surface area nanostructured composite electrode. The superior heterogeneous catalytic activity of the nanostructured Au electrode, as determined through temperature programmed reaction, is believed to reduce the charge transfer potentiometric sensitivity to the test gases. In comparison, the low surface area Au sensing electrode did not favor heterogeneous catalysis of CO or NO2 at 500 °C, the temperature of sensor operation.