Half-Cell Potential Analysis of an Ammonia Sensor with the Electrochemical Cell Au | YSZ | Au, V2O5-WO3-TiO2

Sensors

Daniela Schönauer-Kamin²  Maximilian Fleischer¹ 

[1] Corporate Technology, Siemens AG, Munich 81739, Germany;Department of Functional Materials, University of Bayreuth, Bayreuth 95440, Germany

关键词: mixed potential;    selective catalytic reduction (SCR);    exhaust gas sensor;    polarization curves;    electrochemical cell;   

DOI  :  10.3390/s130404760

来源: mdpi

【 摘 要 】

Half-cell potentials of the electrochemical cell Au, VWT | YSZ | Au are analyzed in dependence on oxygen and ammonia concentration at 550 °C. One of the gold electrodes is covered with a porous SCR catalyst, vanadia-tungstenia-titania (VWT). The cell is utilized as a potentiometric ammonia gas sensor and provides a semi-logarithmic characteristic curve with a high NH₃ sensitivity and selectivity. The analyses of the Au | YSZ and Au, VWT | YSZ half-cells are conducted to describe the non-equilibrium behavior of the sensor device in light of mixed potential theory. Both electrode potentials provide a dependency on the NH₃ concentration, whereby VWT, Au | YSZ shows a stronger effect which increases with increasing VWT coverage. The potential shifts in the anodic direction confirm the formation of mixed potentials at both electrodes resulting from electrochemical reactions of O₂ and NH₃ at the three-phase boundary. Polarization curves indicate Butler-Volmer-type kinetics. Modified polarization curves of the VWT covered electrode show an enhanced anodic reaction and an almost unaltered cathodic reaction. The NH₃ dependency is dominated by the VWT coverage and it turns out that the catalytic properties of the VWT thick film are responsible for the electrode potential shift.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.