Polytungstate clusters on zirconia as a sensing material for a selective ammonia gas sensor

Tungstated-zirconia has been tested as a functional material for a selective ammonia gas sensor. The sensor has been found to respond consistently and rapidly to changes in concentration of ammonia in the oxygen rich and moist gas mixture at 673 K. The sensor showed negligible cross-sensitivity to propene. CO, and NO. From characterizations of tungstated-zirconia by XRD, Raman, UV-vis, high-resolution TEM, and ammonia-TPD, it was found that subnano-sized polytungstate clusters are uniformly supported on the zirconia surface, and the strong acid sites derived from the polytungstate clusters are suggested to effectively work as selective adsorption sites for ammonia. The fabricated ammonia sensor utilizing tungstated-zirconia is expected to be useful for controlling the injection amount of ammonia in urea-SCR systems. (C) 2006 Elsevier B.V. All rights reserved.