%0 Journal Article
%T Half-Cell Potential Analysis of an Ammonia Sensor with the Electrochemical Cell Au£¿|£¿YSZ£¿|£¿Au, V2O5-WO3-TiO2
%A Daniela Sch£¿nauer-Kamin
%A Maximilian Fleischer
%A Ralf Moos
%J Sensors
%D 2013
%I MDPI AG
%R 10.3390/s130404760
%X Half-cell potentials of the electrochemical cell Au,£¿VWT£¿|£¿YSZ£¿|£¿Au are analyzed in dependence on oxygen and ammonia concentration at 550 ¡ãC. 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 NH 3 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 NH 3 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 O 2 and NH 3 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 NH 3 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
%K mixed potential
%K selective catalytic reduction (SCR)
%K exhaust gas sensor
%K polarization curves
%K electrochemical cell
%U http://www.mdpi.com/1424-8220/13/4/4760