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Detection of the Dynamics of Lambda Probes by Cyclic Voltammetry

Title data

Fischer, Sabine ; Achmann, Sabine ; Schönauer, Daniela ; Moos, Ralf:
Detection of the Dynamics of Lambda Probes by Cyclic Voltammetry.
2011
Event: 9th Asian Conference on Chemical Sensors , 14.-17.11.2011 , Taipei, Taiwan.
(Conference item: Conference , Other Presentation type)

Abstract in another language

BACKGROUND
Short response times of lambda probes are essential for a suitable engine control. By use of cyclic voltammetry, it is possible to detect slow-responding sensors so that this method can serve as a good indicator for sensor self-diagnostics.
METHODS
The cyclic voltammograms are recorded by a Potentiostat (Autolab PGSTAT12) in a voltage range of -2.0 V to 1.5 V with a scan rate of 100 mV / s. To simulate exhaust-like conditions, a heater voltage of 12 V is applied to lambda probes (LSF 4.2) and the temperature of the measurement chamber is set to 200 °C. For this investigation, two good new sensors as well as two aged ones at the limit of response time specification are measured and compared at different synthetic exhausts.
RESULTS
At cathodic range, the slow-responding aged sensors show a constant diffusion limited current at λ > 1 with a saturation current behavior. The current is proportional to O2 content (not shown here). The new ones exhibit pure ohmic behavior in this voltage range, so that the non-conform sensor can be identified. Futhermore, the electrolysis of water is a good criterion for the functionality of the sensor. As shown, well-performing new lambda probes electrolyze water below – 1.2 V and show ohmic behavior at lower voltages. At slowresponding aged sensors, the same diffusion limiting current occurs, provided that water formation requires half oxygen. The limiting current can be interpreted by sintering of the diffusion barrier or Pt-cermet electrode so that the sensor dynamics gets slower.

Further data

Item Type: Conference item (Other)
Refereed: Yes
Institutions of the University: Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Functional Materials > Chair Functional Materials - Univ.-Prof. Dr.-Ing. Ralf Moos
Faculties
Faculties > Faculty of Engineering Science > Chair Functional Materials
Profile Fields > Advanced Fields > Advanced Materials
Research Institutions > Research Centres > Bayreuth Center for Material Science and Engineering - BayMAT
Profile Fields
Profile Fields > Advanced Fields
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 19 May 2015 08:12
Last Modified: 13 Apr 2016 07:16
URI: https://eref.uni-bayreuth.de/id/eprint/13626