“…9. It can be seen that the limiting current and the oxygen concentration display a good linear relationship, which is related to the correlation theory of the Knudsen diffusion 24 .where D K , P , T , F , R , S and L are oxygen diffusion coefficient of Knudsen diffusion, partial pressure difference of diffused gas between electrodes I and II, temperature, Faraday constant, gas constant, total cross-sectional area and length of diffusion path, respectively.Figure 9The relationship between the limiting current and oxygen concentration at 800 °C.…”
(4YSZ)
0.93
(Fe
2
O
3
)
0.07
and 9 mol% Y
2
O
3
stabilized ZrO
2
(9YSZ) were synthesized by co-precipitation method and their crystalline structure, microstructure, electronic conductivity, total conductivity were characterized. A limiting current oxygen sensor was assembled with (4YSZ)
0.93
(Fe
2
O
3
)
0.07
dense diffusion barrier and 9YSZ solid electrolyte by Pt sintered-paste method. Influences of temperature (
T
), oxygen concentration (
x
(O
2
)) and water vapor pressure (
p
(H
2
O)) on sensing characteristics of the limiting current oxygen sensor were investigated. The crystalline structure of (4YSZ)
0.93
(Fe
2
O
3
)
0.07
and 9YSZ belong to cubic structure with
. The total conductivity of (4YSZ)
0.93
(Fe
2
O
3
)
0.07
is higher than that of 9YSZ and the electronic and total conductivities of the samples meet the linear relationship with 1000/
T
. The limiting current oxygen sensor exhibits excellent sensing characteristics under test conditions. The effects of
T
,
x
(O
2
) and
p
(H
2
O) are as follows: Log(
I
L
·
T
) depends linearly on 1000/
T
,
I
L
depends linearly on
x
(O
2
) and
I
L
is not significantly dependent on
p
(H
2
O).
“…9. It can be seen that the limiting current and the oxygen concentration display a good linear relationship, which is related to the correlation theory of the Knudsen diffusion 24 .where D K , P , T , F , R , S and L are oxygen diffusion coefficient of Knudsen diffusion, partial pressure difference of diffused gas between electrodes I and II, temperature, Faraday constant, gas constant, total cross-sectional area and length of diffusion path, respectively.Figure 9The relationship between the limiting current and oxygen concentration at 800 °C.…”
(4YSZ)
0.93
(Fe
2
O
3
)
0.07
and 9 mol% Y
2
O
3
stabilized ZrO
2
(9YSZ) were synthesized by co-precipitation method and their crystalline structure, microstructure, electronic conductivity, total conductivity were characterized. A limiting current oxygen sensor was assembled with (4YSZ)
0.93
(Fe
2
O
3
)
0.07
dense diffusion barrier and 9YSZ solid electrolyte by Pt sintered-paste method. Influences of temperature (
T
), oxygen concentration (
x
(O
2
)) and water vapor pressure (
p
(H
2
O)) on sensing characteristics of the limiting current oxygen sensor were investigated. The crystalline structure of (4YSZ)
0.93
(Fe
2
O
3
)
0.07
and 9YSZ belong to cubic structure with
. The total conductivity of (4YSZ)
0.93
(Fe
2
O
3
)
0.07
is higher than that of 9YSZ and the electronic and total conductivities of the samples meet the linear relationship with 1000/
T
. The limiting current oxygen sensor exhibits excellent sensing characteristics under test conditions. The effects of
T
,
x
(O
2
) and
p
(H
2
O) are as follows: Log(
I
L
·
T
) depends linearly on 1000/
T
,
I
L
depends linearly on
x
(O
2
) and
I
L
is not significantly dependent on
p
(H
2
O).
“…In summary, the sensor with PdOsensing electrode has a relatively high sensitivity to CO (−33.4 mV/decade), which is calculated from the results in Fig. 7, compared to the other reports in literatures [2,[6][7][8]. Although, the selectivity is the major problem that hinder the sensor for the practice, the results of sensor for CO sensing, which is corresponding to the properties of PdO, is focused and analyzed in the paper.…”
Section: Resultsmentioning
confidence: 90%
“…Miura and Yamazoe proposed a pair of CdO and SnO 2 electrodes fabricated on a half open YSZ tube for CO detection at 600°C [1]; the coupled oxide electrode could effectively cancel out the response to other gases, allowing the selective response to CO. Mukundan et al found a higher mixed potential on the Au than Pt as sensing electrode on a Ce 0.8 Gd 0.2 O 1.9 electrolyte [7]; nonetheless, Au suffered stability problems at 600°C. The planar design of potentiometric sensor was introduced with a sandwich structure by Kale et al for CO detection, sensing, and reference electrodes of which were exposed to the tested gas [8]; they found that porous (Ba x La 1-x ) 2 In 2 O 5 ceramic electrolyte coupled with ITO (indium tin oxide) and Pt has better response than the dense one.…”
This study aims to explore the potential merits of palladium oxide sensing electrode. PdO is applied on a solidstate potentiometric sensor on an yttria-stabilized zirconia (YSZ) electrolyte as sensing electrode for the first time. The physical properties, morphology, chemical properties, and sensing performance of synthetic PdO electrode are characterized. An attractive phenomenon is observed that the thicknesses of PdO electrode have a little impact on the sensor response. The sensing mechanism is discussed regarding to the impedance analysis and sensing results of the sensor. We find that the change of electric potential of the sensor in CO environment is irrelevant to mobile oxygen in electrolyte, and the charged intermediate on the PdO is proposed to contribute the sensor signal. In addition, the response of sensor depends logarithmically on the concentrations of CO, and the slope is −33.4 mV/decade.
“…Furthermore, the identical sensing behavior for the sensor comprised of LSCM or Pt electrode confirms our speculation that LSCM indeed demonstrates high reactivity to oxygen and can replace the Pt to be used in the limiting current oxygen sensor. Table 1 summarized the performance of the reported oxygen sensor using various sensing materials [6,7,10,13,22,23]. In summary, the limiting oxygen sensor comprised of LSCM shows comparable sensing behavior with that of these mentioned counterparts, and minor hysteresis is observed for the sensor using LSCM or Pt electrode with the bias voltage that is below 0.5 V (Figure S4).…”
Section: Resultsmentioning
confidence: 95%
“…To date, oxygen sensor applied for monitoring A/F ratio includes, but not limited to, the potentiometric, limiting current, and conductometric oxygen sensors [6,7,8,9]. Among them, limiting current oxygen sensor gains more attention due to their relative stable signal, wider concentration monitoring range, and satisfactory linear relationship between response signal and oxygen concentration [6].…”
Zirconia-based limiting current oxygen sensor gains considerable attention, due to its high-performance in improving the combustion efficiency of fossil fuels and reducing the emission of exhaust gases. Nevertheless, the Pt electrode is frequently used in the oxygen sensor, therefore, it restrains the broader application due to the high cost. Quite recently, La0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) has been reported to be highly active to catalyze oxygen reduction. Herein, with the intention of replacing the frequently used Pt, we studied the practicability of adapting the LSCM to zirconia-based limiting current oxygen sensor. Through comparing the electrocatalytic activity of LSCM and Pt, it is confirmed that LSCM gave analogous oxygen reactivity with that of the Pt. Then, limiting the current oxygen sensors comprised of LSCM or Pt are fabricated and their sensing behavior to oxygen in the range of 2–25% is evaluated. Conclusively, quick response/recovery rate (within 7s), linear relationship, and high selectivity (against 5% CO2 and H2O) in sensing oxygen are observed for the sensors, regardless of the sensing materials (LSCM or Pt) that are used in the sensor. Particularly, identical sensing characteristics are observed for the sensors consisting of LSCM or Pt, indicating the practicability of replacing the Pt electrode by adapting the LSCM electrode to future zirconia-based oxygen sensors.
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