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Investigation of an Impedimetric LaSrMnO<sub>3</sub>-Au/Y<sub>2</sub>O<sub>3</sub>-ZrO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> Composite NO<sub>x</sub> Sensor
oleh: Nabamita Pal, Gaurab Dutta, Khawlah Kharashi, Erica P. Murray
Format: | Article |
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Diterbitkan: | MDPI AG 2022-02-01 |
Deskripsi
Composite NO<sub>x</sub> sensors were fabricated by combining partially and fully stabilized yttria-doped zirconia with alumina forming a composite electrolyte, Y<sub>2</sub>O<sub>3</sub>-ZrO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub>, and strontium-doped lanthanum manganese oxide mixed with gold to form the composite sensing electrode, La<sub>0.8</sub> Sr<sub>0.2</sub>MnO<sub>3</sub>-Au. A surface chemistry analysis of the composite sensor was conducted to interpret defects and the structural phases present at the Y<sub>2</sub>O<sub>3</sub>-ZrO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> electrolyte, as well as the charge conduction mechanism at the LaSrMnO<sub>3</sub>-Au electrode surface. Based on the surface chemistry analysis, ionic and electronic transport properties, and microstructural features of sensor components, the working principle was described for NO<sub>x</sub> sensing at the composite sensor. The role of the composite materials on the NO<sub>x</sub> sensing response, cross-sensitivity to O<sub>2</sub>, H<sub>2</sub>O, CO, CO<sub>2</sub>, and CH<sub>4</sub>, and the response/recovery rates relative to sensor accuracy were characterized by operating the composite <inline-formula><math display="inline"><semantics><mrow><msub><mrow><mi>NO</mi></mrow><mi mathvariant="normal">x</mi></msub></mrow></semantics></math></inline-formula> sensors via the impedimetric method. The composite sensors were operated at temperatures ranging from 575 to 675 °C in dry and humidified gas environments with NO and NO<sub>2</sub> concentrations varying from 0 to 100 ppm, where the balance gas was N<sub>2</sub>. It was found that the microstructure of the composite NO<sub>x</sub> sensor electrolyte and sensing electrode had a significant effect on interfacial reactions at the triple phase boundary, as well as the density of active sites for oxygen reactions. Overall, the composite NO<sub>x</sub> sensor microstructure enabled a high NO<sub>x</sub> sensing response, along with low cross-sensitivity to O<sub>2</sub>, CO, CO<sub>2</sub>, and CH<sub>4</sub>, and promoted NO detection down to 2 ppm.