High-temperature hydrogen sensor based on stabilized zirconia and a metal oxide electrode

A zirconia-based electrochemical device attached with an oxide electrode was developed for the detection of H-2 in air at elevated temperature. Among the oxides tested, ZnO was found to be best suited for the sensing electrode. The device attached with ZnO showed fairly good sensing characteristics to 50-500 ppm H-2 in air at 450-600 degrees C. The 90% response and 90% recovery times to 200 ppm H-2 at 600 degrees C for the ZnO-attached device were 5 s and 10 s, respectively. The EMF value of the device was almost linear with the logarithm of H-2 concentration. It was also observed that the device exhibited excellent selectivity to H-2 in the coexistence of NO, NO2, CH4, CO2 and H2O, as well as a good long-term stability. On the basis of the measurements of anodic and cathodic polarization curves, the sensing mechanism was confirmed to involve a mixed potential at the oxide sensing electrode.