Comparative evaluation of ammonia sensor principles for SCR applications : From laboratory characterization to real exhaust operation

Title data

Wöhrl, Thomas ; Ehlert, Rosa ; Donker, Nils ; Müller, Andreas ; Schönauer-Kamin, Daniela ; Hagen, Gunter ; Moos, Ralf:
Comparative evaluation of ammonia sensor principles for SCR applications : From laboratory characterization to real exhaust operation.
In: Sensors and Actuators B: Chemical. Vol. 467 (2026) . - 140528.
ISSN 0925-4005
DOI: https://doi.org/10.1016/j.snb.2026.140528

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Abstract in another language

Precise detection of ammonia (NH3) in the exhaust gas of SCR systems is crucial for complying with emission limits and for optimizing exhaust gas aftertreatment systems. In this work, two different high temperature sensor principles for detecting NH3 intended for use as slip sensors in SCR systems were investigated. One sensor concept is based on the selective adsorption properties of a zeolite towards NH3, while the other sensor type is based on mixed potential principle. First, a comprehensive pre‑characterization of the sensors was carried out in a laboratory test setup to determine their basic sensitivity to NH3 and various cross‑sensitivities to typical exhaust gas components such as NOx, H2O, CO, and CO2. The sensors were subsequently tested under realistic operating conditions at an engine test bench as NH3 slip sensors. The results of the lab tests could be successfully applied to the measurements during engine operation, thereby enabling continuous monitoring of NH3 slip. Post‑characterization measurements demonstrated that the ammonia sensing properties of both sensor variants remained stable over the measurement duration. Overall, both sensor principles showed promising results with respect to ammonia sensitivity, response time, and aging behavior.