Mixed Potential Type Gas Sensor Research Articles

Artificial olfaction based on tafel curve for quantitative detection of acetone ethanol gas mixture

This work established an artificial olfaction based on a single mixed potential type gas sensor. By identifying the Tafel curve, artificial olfaction can determine the concentration of each component in the acetone and ethanol vapor mixture. To save a long testing circle, a finite element model was built to efficiently output the Tafel curves of the sensor for different concentrations of vapor mixtures. Based on the Tafel curve data obtained from the simulation, different classification algorithms were trained to determine the operating state of the sensor. Among them, eXtreme Gradient Boosting (XGB) had a 99% accuracy in determining whether the sensor is saturated or not. Then three different regression algorithms (XGB, Gradient Boosting Decision Tree (GBDT), and Random Forest (RF)) were trained to identify acetone and ethanol vapor concentrations. The results showed that XGB and GBDT were the most effective in identifying acetone and ethanol vapor. The mean absolute percentage errors for the identified acetone and ethanol in the gas mixture were 11.3% and 23%, respectively. The above results indicated that it was feasible and effective to use Tafel curves to detect VOC gases.

YSZ-Based Mixed Potential Type NH3 Sensor Attached with Ag Doped FeVO4 Sensing Electrode

Introduction In an automobile selective catalytic reduction (SCR) system, the monitoring of NH3 concentration is of vital importance. NH3 detection in such harsh environment of high temperature and humidity is an almost impossible task for most testing methods. Nevertheless, YSZ-based mixed potential type gas sensor is an incomparable choice. Moreover, the development and utilization of sensing electrode materials is an effective method to develop high performance YSZ-based mixed potential type ammonia gas sensor [1]. FeVO4, a n-type semiconductor with direct band gap, is considered as a promising sensing electrode material due to its special three-dimensional layered structure [2]. Ag was reported to have excellent catalytic activity. Through Ag collaborating with the sensing electrode, the response of the NH3 sensor could be enhanced accompanied by the improved sensitivity and detection limit [3]. In this study, we prepared FeVO4 through the sol-gel method. Then, Ag doped FeVO4 in different molar ratio (1.5, 2.5, 3.5 and 4.5 mol.%) was synthesized through the sodium borohydride reduce method and used as sensing electrode material of the YSZ-based mixed potential type NH3 gas sensor. The effects of different molar ratios Ag doped on the NH3 sensing performance were studied. The sensor attached with 3.5 mol.% Ag doped FeVO4 displays high response to target NH3 gas, short response and recovery time, satisfying humidity resistance and good repeatability, indicating its potential for in-situ ammonia monitoring for automotive applications [4]. Method Fabrication and measurement of the gas sensor The sensor was fabricated on a YSZ plate (8 mol. % Y2O3 doped, 2 mm × 2mmsquare, 0.2 mm thickness), provided by Anpeisheng Corp. China. A point-shaped electrode and a narrow stripe-shaped electrode were formed on the two sides using a commercial Pt paste (Sino-platinum Metals Co. Ltd.), and sintered at 1000°C. The sensing material was mixed with a minimum quantity of deionized water and the resultant paste was applied on the point-shaped Pt to form stripe-shaped SE and then sintered at 800 °C for 2 h. The testing method of the sensor was as showed in our previous work [5]. Results and Conclusions A series of sensing tests showed the sensor attached with 3.5 mol.% Ag doped FeVO4-SE had the highest response to NH3, as Fig.1a shows. The reason that the sensor attached with 3.5 mol.% Ag doped FeVO4-SE have the highest sensing performance is due to best electrochemical catalytic activity to NH3 of the sensing electrode materials. The best electrochemical catalytic activity of the material will be proved by the polarization curves and complex impedance test in the future. The NH3 sensing performance of the sensor attached with 3.5 mol.% Ag doped FeVO4 was studied at different operating temperatures and the optimal operating temperature was determined at 550 °C, as Fig.1b shows. The sensor could even detect as low as 200 ppb NH3 with the response of -3.2 mV, as shown in Fig.1 c. Also, the sensor had a good reproducibility as shown in Fig.1 d. Moreover, the sensor displayed good selectivity to NH3 when compared to other interfering gases such as NO2, SO2, C2H2 and CO, as shown in Fig.1 e. For accurate and rapid detection of NH3, the response and recovery time is a vital indicator. In the present research, the typical 90% response time to 50 ppm NH3 of the sensor was less than 3 s as shown in Fig.1 f. In the actual working condition, the exhaust gas is always of high humidity. Therefore, the environmental humidity’s influence on the NH3 sensor was studied and the result in F ig.1g and h showed that the sensor had an acceptable humidity stability. Based on the above results, the sensor we fabricated is prospective in automobile selective catalytic reduction (SCR) exhaust gas treatment system.

Highly selective and stable mixed-potential type gas sensor based on stabilized zirconia and Cd2V2O7 sensing electrode for NH3 detection

In this work, the highly selective and stable mixed potential type stabilized zirconia (YSZ) based gas sensor using Cd2V2O7 sensing electrode (SE) synthesized via simple coprecipitation method was fabricated and developed for effective detection of NH3 at 650 °C. The as-prepared Cd2V2O7 sensing material was characterized by X-ray diffraction (XRD), Raman spectrum, X-ray photoelectron spectroscopy (XPS) and Field-emission scanning electron microscopy (FESEM). The results of gas sensing measurement indicated that the sensor attached with Cd2V2O7- SE displayed the response value of −68 mV and rapid response rate of 5 s to 100 ppm NH3 at 650 °C. The present device also exhibited the low detection limit of 1 ppm and the piecewise sensitivities of −6 and −66 mV/decade to NH3 in the concentration ranges of 1–10 ppm and 10–200 ppm, respectively. Moreover, the fabricated sensor showed good reproducibility, excellent selectivity, stability to oxygen concentration, relative humidity and 30 days continuous aging of high temperature at 650 °C. And the complex impedance and polarization curves were performed to explain the selectivity and verify the sensing mechanism involving mixed potential model.

Ultrafast-response stabilized zirconia-based mixed potential type triethylamine sensor utilizing CoMoO4 sensing electrode

An ultrafast-response yttria stabilized zirconia (YSZ)-based mixed potential type gas sensor utilizing molybdate CoMoO4 sensing electrode was developed to realize the effective detection of triethylamine (TEA) at 600 °C. The gas sensing characteristic of the fabricated sensor was optimized by changing the calcination temperature of CoMoO4 sensing material and results indicated that the device attached with CoMoO4-SE sintered at 1000 °C exhibited the highest response value (−102 mV) to 100 ppm TEA and low detection limit of 100 ppb at 600 °C. Interestingly, the response and recovery times of the present sensor to 100 ppm TEA were 1 s and 10 s, which signified the ultra-fast response rate. The response value of fabricated sensor displayed the piecewise linear function to logarithm of TEA concentrations and the sensitivities were −14 mV/decade (0.1–5 ppm) and −53 mV/decade (5–200 ppm), respectively. More importantly, the present sensor also exhibited good repeatability, selectivity, slight effect of humidity and long-term stability of 20 days, indicating a great candidate for use in detection of TEA. Furthermore, the device based on mixed potential mechanism was proposed and further verified using polarization curve.

CeO2-based mixed potential type acetone sensor using La1-xSrxCoO3 sensing electrode

In this article, CeO2-based mixed potential type gas sensor attached with sensing electrodes (SEs) consisting of perovskite-type La1-xSrxCoO3 (x = 0.1, 0.2, 0.3 and 0.5) composite oxides has been developed for acetone detection. The effect of different Sr2+ doping content in La1-xSrxCoO3 oxide material and calcination temperature on acetone sensing characteristics was investigated. It was seen that the sensor using La0.8Sr0.2CoO3 calcined at 1000 °C as SE gave the largest sensing signal to acetone in the concentration range of 1–50 ppm at 600 °C among these sensors. The response value (ΔV) of the sensor was sectionally linearly changed with the logarithm of acetone concentration within the ranges of 1–5 ppm and 5–50 ppm, and the sensitivities were −26 and −49 mV/decade, respectively. In addition, it is noteworthy that the response of the sensor to 1 ppm acetone was approximately −8.7 mV. The sensor also exhibited consistent response and recovery characteristics in five cycles, indicating the sensing device had good reproducibility. Besides, the sensor exhibited the highest response to 10 and 50 ppm acetone and less effective response to other tested gases, it indicates that the sensor has good selectivity. Furthermore, the long-term stability for the sensor to 20 ppm acetone was good because that only a slight attenuation in the sensing response was observed during 30 days. The sensing characteristics of the sensor attached with La0.8Sr0.2CoO3-SE sintered at 1000 °C to acetone were explained in terms of electrocatalytic activity changes induced by effects of doped Sr divalent cation.

The mixed potential type gas sensor based on stabilized zirconia and molybdate MMoO4 (M: Ni, Co and Zn) sensing electrode aiming at detecting triethylamine

The mixed potential type gas sensors utilizing yttria stabilized zirconia (YSZ) solid electrolyte and molybdates MMoO4 (M: Ni, Co and Zn) sensing electrodes (SEs) were fabricated aiming at detecting triethylamine (TEA) at 600 °C. Results indicated that the device attached with NiMoO4-SE exhibited the highest response value of −71 mV to 50 ppm TEA and low detection limit of 100 ppb at 600 °C. Moreover, the response time of the developed sensor to 50 ppm TEA was 3 s, which signified the fast response rate. The response value of fabricated sensor displayed the piecewise linear relationship to logarithm of TEA concentrations and the sensitivities were −4 mV/decade (0.1–1 ppm) and −37 mV/decade (1–100 ppm), respectively. More importantly, the present sensor also exhibited good repeatability, selectivity, slight effect of humidity and stability of 10 days, indicating a great candidate for use in detection of TEA. Furthermore, the device based on mixed potential mechanism was proposed and further verified using polarization curve.

CeO2-based mixed potential type acetone sensor using MMnO3 (M: Sr, Ca, La and Sm) sensing electrode

The CeO2-based mixed potential type gas sensors attached with MMnO3 (M: Sr, Ca, La and Sm) sensing electrode have been fabricated to detect acetone. All MMnO3 materials were prepared by a simple sol-gel method. The results indicated that the response of the sensor based on SrMnO3 sintered at 1000 °C to 20 ppm acetone was the highest compared with sensors using MMnO3 (M: Ca, La and Sm)-SE, which was −49 mV. The sensor attached with SrMnO3-SE could detect even 1 ppm acetone, and the response value (ΔV) was −3 mV, which was an acceptable value. The ΔV of the sensor was linearly changed with the logarithm of acetone concentration in the range of 1–50 ppm and the sensitivity was −36 mV/decade. Most notably, the typical 90% response and recovery times of the sensor attached with SrMnO3-SE to 20 ppm acetone were only 2 s and 6 s. Moreover, the sensor manifested good repeatability and stability. Besides, the sensing mechanism of the sensor was explained, and polarization curve was measured to further demonstrate the mixed potential mechanism.

Highly sensitive gas sensor based on stabilized zirconia and CdMoO4 sensing electrode for detection of acetone

A highly sensitive mixed potential type gas sensor based on stabilized zirconia (YSZ) and CdMoO4 sensing electrode (SE) was developed and used for detection of acetone at 625°C. By comparing the sensing performance for different devices fabricated, the sensor utilizing CdMoO4-SE exhibited the highest response value (−133.5mV) to 100ppm acetone at 625°C, and even could achieve low detection limit of 500ppb at 625°C. The sensor attached with CdMoO4-SE displayed high sensitivity of −84mV/decade to acetone in the range of 5–300ppm at 625°C. The present device also showed good repeatability, selectivity to certain deleterious gases, moisture resistance and acceptable drifts in 10days measured period at 625°C, demonstrating great potential for practical application in acetone sensing detection. Additionally, the sensor involving mixed potential mechanism was proposed and further clarified by polarization curve.

Improvement of NO2 sensing characteristic for mixed potential type gas sensor based on YSZ and Rh/Co3V2O8 sensing electrode

This work may have potential significance to develop new sensor strategies and enrich the sensing mechanism for enhanced sensing characteristics.

Fabrication of well-ordered porous array mounted with gold nanoparticles and enhanced sensing properties for mixed potential-type zirconia-based NH3 sensor

The nano-bowl shaped structure and gold nanoparticle array were successfully fabricated on the YSZ substrate and examined to improve the sensitivity of mixed potential type NH3 gas sensor. The nano-bowl shaped structure was constructed by solution-dipping template (polystyrene spheres) strategy and gold nanoparticle inlaid in the nanostructure was fabricated by vacuum evaporation plating technology. The present study mainly explored the influence of gold layer’s thickness on the nanostructure. The perfect ordered gold nanoparticle array inlaid in nano-bowl shaped structure was obtained when the evaporated gold film thickness was about 50nm. The mixed potential type gas sensor which based on processed YSZ substrate displayed the improved sensitivity and selectivity to NH3 at elevated temperature. All the enhanced sensing properties might due to the enlarged three phase boundary (TPB) and inlaid gold nanoparticle array.

High performance mixed potential type acetone sensor based on stabilized zirconia and NiNb2O6 sensing electrode

A high performance mixed potential type gas sensor based on stabilized zirconia (YSZ) and NiNb2O6 as sensing electrode was fabricated and used for detection of acetone at 650°C. NiNb2O6 prepared via a facile sol–gel method and sintered at different temperatures was characterized using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The present study mainly focused on the effect of sintering temperature (800°C, 1000°C, 1200°C) of NiNb2O6-SE materials on acetone sensing characteristics at 650°C. Results indicated that the sensor using NiNb2O6-SE sintered at 1000°C exhibited the largest sensitivity to acetone in the concentration range of 5–500ppm at 650°C, which the slope was −79mV/decade. The response for the sensor attached with a NiNb2O6-SE sintered at 1000°C to 100ppm of acetone was approximately −113mV. Moreover, the present sensor could detect even 500ppb acetone with an acceptable response. The present device also displayed fast response and recovery times, good repeatability, slight sensitive effect to humidity, small drifts in 40 days measured periods, and acceptable selectivity at 650°C. Additionally, the mixed potential mechanism was further demonstrated by polarization curve.

Mixed potential type acetone sensor using stabilized zirconia and M3V2O8 (M: Zn, Co and Ni) sensing electrode

A series of mixed potential type gas sensors using stabilized zirconia and M3V2O8 (M: Zn, Co and Ni) sensing electrode were fabricated and applied for detecting acetone at 600°C. Among the sensors utilizing these composite oxides (Zn3V2O8, Co3V2O8 and Ni3V2O8)–SEs prepared via a facile sol–gel method, the sensor attached with Zn3V2O8–SE exhibited the highest response to acetone at 600°C. Therefore, the present study mainly focused on acetone sensing performance for YSZ-based sensor using Zn3V2O8–SE at 600°C. Results showed that the sensor attached with Zn3V2O8–SE could detect even 1ppm acetone with an acceptable response. Moreover, ΔV of the sensor attached with Zn3V2O8–SE exhibited segmentally linear relationship to the logarithm of acetone concentration in the ranges of 1–10ppm and 10–400ppm, which the sensitivities were −16 and −56mV/decade, respectively. The present device also displayed good repeatability, small drifts in 30 days measured period, and the excellent sensitivity and relatively good selectivity in the presence of various interfering gases before and after 30 days high-temperature-aging of 600°C. Additionally, polarization curve was measured to further demonstrate the mixed potential mechanism.

Mixed-potential type NH3 sensor based on stabilized zirconia and Ni3V2O8 sensing electrode

A mixed-potential type gas sensor using stabilized zirconia (YSZ) and a sensing electrode (SE) that consists of the new type composite oxide Ni3V2O8 was developed for ammonia (NH3) detection at elevated temperature, such as 650°C. The Ni3V2O8 materials were synthesized from Ni(NO3)2·6H2O and NH4VO3 through the sol–gel method. Ni3V2O8 sintered at different temperatures was also characterized using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The present study mainly focused on the effect of sintering temperature of SE materials (800°C, 1000°C, 1200°C) on NH3 sensing characteristics. Results showed that the Ni3V2O8 calcined at 1000°C exhibited the largest sensitivity in an NH3 concentration range of 50–500ppm at 650°C. The response for the sensor attached with a Ni3V2O8-SE sintered at 1000°C to 100ppm of NH3 was approximately −62mV. Moreover, ΔV almost varied linearly with the logarithm of NH3 concentration in the range of 50–500ppm, which the slope was −96mV/decade. Furthermore, the present sensor also displayed small drifts over 30 days and cross-sensitivities in the presence of various interfering gases. The high-sensing characteristics of the sensor attached with a Ni3V2O8-SE sintered at 1000°C to NH3 are explained in terms of the micro-structure of the SE and the high electrocatalytic activities induced by the beneficial effect of the interaction between the Ni and V two metal oxides.

A review of mixed-potential type zirconia-based gas sensors

A robust and reliable gas sensing device is considered as a convenient and practical solution for gas concentration monitoring that has become a mandatory requirement in different field of applications. For in situ hazardous gases detection, a mixed-potential type gas sensor has been regarded as a promising solid-state gas sensor. For the past three decades, there has been a significant progress in achieving high performance in mixed-potential type sensors. Therefore, this review is focused on reporting the development of mixed-potential type gas sensors with combined yttria-stabilized zirconia (YSZ) as the base solid electrolyte material and various classes of electrode materials for their potential utilization as a high-performance sensing electrode. The underlying sensing mechanism of a mixed-potential type YSZ-based sensor is elaborated here in detail. Transformation in design and configuration of this type of sensor is also covered in this report. In addition, recent progresses on mixed-potential type gas sensors development for detection of several target gases, such as carbon monoxide, hydrocarbons, nitrogen oxides, hydrogen, and ammonia, are reviewed. Strategies to improve the sensing characteristic, particularly gas sensitivity and selectivity, are also reported. Based on the understanding of the fundamental sensing mechanism and the requirements for high-performance gas sensors, challenges and future trends for this type of gas sensor development are discussed.

Mixed-Potential Type Zirconia-Based NH3 Sensor Using SnO2-Disk Sensing-Electrode Attached with Sputtered Au

The effect of Au sputtered at the interface between the SnO2-disk sensing-electrode (SE) and a porous yttria-stabilized zirconia (YSZ) layer on the sensing characteristics of the mixed-potential type gas sensor was examined. The existence of Au at the SE/YSZ interface gave a significant increase in NH3 sensitivity, while the sensitivities to the other gases examined were largely decreased. This brought about an excellent NH3 selectivity. By evaluating polarization curves, the Au sputtering was confirmed to improve the cataltic activity to the anodic reaction of NH3, while drastically decreased that of C3H6.

Progress in NASICON-based mixed-potential type gas sensors

The mixed-potential type gas sensors combining NASICON with oxide electrodes exhibit high sensing performance to typical pollution gases in the atmospheric environment in the intermediate temperature range, indicating a potential in practical application. This paper describes the state-of-the-art for the sensors based on the NASICON, including the current-type, the equilibrium-potential-type and mixed-potential-type. For improving the performance of sensors based on the NASICON and oxide electrodes, two main approaches have been utilized: the developing of new oxide electrode materials and the design of novel sensor structure for enhancing the sensing performance as well as the sensing mechanism involved in the mixed potential.

Impedance spectroscopy based characterization of an electrochemical propylene sensor

Abstract In this investigation, an electrochemical mixed potential type gas sensor was characterized using impedance spectroscopy. Specifically, the effect of operating temperature (435–610 °C) on sensor response and response time was studied. Propylene was used as the analyte to test the ‘La 0.8 Sr 0.2 CrO 3 /YSZ/Pt’ sensor configuration. Two-electrode AC impedance measurement was performed with a frequency sweep from 13 MHz down to 10 mHz and excitation voltage of 10 mV. For a fixed propylene concentration, the bulk and interfacial resistances was seen to decrease with increase in the sensor operating temperature. An Arrhenius behavior of the bulk and interfacial resistance was observed. The activation energy for O 2 ion conduction and charge transfer was found to be 0.94 eV and 1.54 eV respectively. For a 150 °C rise in operating temperature from 485 to 585 °C, a 26-fold improvement in response rise time was observed while an 82% reduction in sensor response was recorded. It is postulated that the increase in operating temperature results in faster reaction kinetics, faster oxygen reduction and greater heterogeneous catalysis.

Progress in mixed-potential type devices based on solid electrolyte for sensing redox gases

Gas sensors based on solid electrolytes have been explored extensively in recent years, especially from growing concerns to environmental issues. Among the various solid electrolyte sensors, the group of devices based on the mixed-potential gas-sensing principle has been paid special attention due to its attractive performances as well as unique working mechanism. These devices, if designed properly, can exhibit high sensitivity and selectivity to redox gases in oxygen containing atmospheres even at high temperature, showing promise of being applied for combustion exhaust monitoring. This article aims at over-viewing recent progress in the mixed-potential type gas sensors. Particular attention is focused on our original work about the zirconia-based sensors using oxide electrodes for detecting various gases such as H 2, CO and NO x at high temperatures.