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Indexed by:期刊论文

Date of Publication:2014-03-01

Journal:SENSORS AND ACTUATORS B-CHEMICAL

Included Journals:SCIE、EI、Scopus

Volume:193

Page Number:542-551

ISSN No.:0925-4005

Key Words:Metal-cation interaction; Impedance spectroscopy; Infrared spectroscopy; X-ray photoelectron spectroscopy; Temperature programmed desorption

Abstract:This paper examines the interaction of ammonia with Ag+-exchanged zeolite Y (Ag-Y) over a range of temperatures (250-450 degrees C). Impedance spectroscopy over the range of 0.5-10(7)Hz indicates that the Ag+ motion within the zeolite is facilitated in the presence of ammonia. Infrared spectroscopy and X-ray photoelectron spectroscopy indicate that Ag+-NH3 bonds are being formed. Temperature programmed desorption coupled with impedance spectroscopy show that the NH3 bonding to Ag+ is disrupted around 300 degrees C. However, in the presence of excess NH3, a fraction of the Ag+ NH3 bond survives up to 450 C. Control experiments show that there is no measurable autoreduction of Ag+, and therefore, proton-mediated change of impedance in the presence of NH3 is not considered relevant. The change in mobility of the Ag+ in the presence of NH3 has been exploited to design an impedance-based NH3 sensor at a fixed frequency of 1000 Hz in the temperature range of 275-350 degrees C, with the optimal sensor response at 300 degrees C. No cross-sensitivity was observed for 02, CO, CO2 and propane. Nitric oxide showed minor interference. Water, however, did show an interference with a decrease in baseline impedance with increasing water. Thus, for practical applications of this sensor, the water content in the gas stream will need to be controlled to a constant value. (C) 2013 Elsevier B.V. All rights reserved.