High NH3 selectivity of NiFe2O4 sensing electrode for potentiometric sensor at elevated temperature.

High NH3 selectivity of NiFe2O4 sensing electrode for potentiometric sensor at elevated temperature.
Anal Chim Acta. 2019 Dec 16;1089:165-173
Authors: Yang B, Wang C, Xiao R, Yu H, Huang C, Wang J, Xu J, Liu H, Xia F, Xiao J
Abstract
NiFe2O4 was synthesized using sol-gel method for sensing electrode material of YSZ based ammonia sensor. NiFe2O4-SEs sintered at 1100 °C, 1150 °C and 1200 °C were characterized by XRD, the BET method and ESEM. By testing the NH3 response of different sensors at 650 °C, it was observed that the 1150 °C sintered sensor had the largest response value (-104.3 mV for 320 ppm NH3) and the highest sensitivity (-77.56 mV/decade), which were related to the most TPB sites and the moderate gas phase catalytic reaction. The response values of the sensor varied almost linearly with the logarithm of 20-320 ppm NH3 at 600-750 °C, which was consistent with mixed-potential mechanism testified by polarization and EIS tests. When the oxygen concentration was at 7-10 vol %, its effect on the response value was within 3%. When the water vapor concentration was 3, 6 and 9 vol %, the ammonia response value was 95.1%, 92.9% and 88.7% of the values when there was no water vapor, respectively. The sensor showed very weak cross sensitivities to NOx, but non-negligible SO2 cross sensitivity. It also displayed slight signal drifts in weekly tests in eight weeks, which showed that the sensor attached with ...

Source: Analytica Chimica Acta - October 21, 2019 Category: Chemistry Authors: Yang B, Wang C, Xiao R, Yu H, Huang C, Wang J, Xu J, Liu H, Xia F, Xiao J Tags: Anal Chim Acta Source Type: research