Operando Investigations of Rare-Earth Oxycarbonate CO2 Sensors

Suzuki, Takuya; Lauxmann, Frieder; Sackmann, André; Staerz, Anna; Berthold, Christoph; Bârsan, Nicolae

doi:10.3390/proceedings2130801

Cited by 4 publications

(3 citation statements)

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“…The experimental setup and measurement procedure are described in the literature . The operating temperature was 300 °C, which was found to be the optimal one in our previous studies. , …”

Section: Experimental Sectionmentioning

confidence: 99%

“…22 The operating temperature was 300 °C, which was found to be the optimal one in our previous studies. 13,23 AC Impedance Spectroscopy. Operando AC impedance spectroscopy measurements under operating conditions were performed using an electrochemical impedance spectroscopy analyzer (AMETEK Scientific Instruments PARSTAT4000) with the aim to understand the conduction process in the sensing layer and, by that, to allow for the calculation of eΔV s .…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…Many kinds of chemoresistive materials for CO 2 gas sensors have been proposed. − Among them, rare-earth oxycarbonates Ln 2 O 2 CO 3 (Ln = La and Nd) possess the highest sensor signal at a relatively low operating temperature. In our previous studies, − we demonstrated that rare-earth oxycarbonates Ln 2 O 2 CO 3 (Ln = La, Nd, and Sm) and rare-earth oxides Ln 2 O 3 (Ln = Nd, Sm, Gd, Dy, Er, and Yb) synthesized by heat treatment in air from oxalate hydrate or acetate hydrate are sensitive to CO 2 ; among them, hexagonal La 2 O 2 CO 3 shows the best performance in terms of sensitivity, stability, and selectivity. Consequently, this material was chosen for a first comprehensive CO 2 sensing study.…”

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confidence: 99%

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Chemoresistive CO₂ Gas Sensors Based On La₂O₂CO₃: Sensing Mechanism Insights Provided by Operando Characterization

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Our previous studies demonstrated that rare-earth oxycarbonates Ln 2 O 2 CO 3 (Ln = La, Nd, and Sm) and rare-earth oxides Ln 2 O 3 (Ln = Nd, Sm, Gd, Dy, Er, and Yb) are sensitive to CO 2 and that hexagonal La 2 O 2 CO 3 is the best among them in terms of sensitivity, stability, and selectivity. In this study, we have conducted a comprehensive operando characterization on a hexagonal La 2 O 2 CO 3 based sensor for the basic understanding of the sensing mechanism. This was done by performing under actual operating conditions simultaneous DC resistance and work function changes measurements, AC impedance spectroscopy measurements, and simultaneous DC resistance and DRIFT spectroscopy measurements. The results demonstrate that the double Schottky barriers at grain−grain boundaries are dominant contribution to sensor resistance; there is a competitive adsorption between carbonate species and hydroxyl groups, which depends on both CO 2 concentration and humidity and leads to the change in height of the Schottky barriers. Finally, we propose a reaction model stating that there are three types of adsorbates, −CO 3 2− , −OH − , and −O 2− , and the relative concentration of which is controlled by a reaction with ambient humidity and CO 2 . This model is able to consistently explain all our experimental findings.

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“…The experimental setup and measurement procedure are described in the literature . The operating temperature was 300 °C, which was found to be the optimal one in our previous studies. , …”

Section: Experimental Sectionmentioning

confidence: 99%