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![(a) Schematic representation of a NH3 amperometric sensor. Reproduced with permission from [64]. (b) Current response on the applied voltage for different ammonia concentrations at 400 °C. x is the NH3 concentration in vol.%. (c) The relation between the limiting current and different NH3 concentrations and (d) current-voltage curves for different temperatures for 5 vol.% ammonia. Reproduced with permission from [64].](publication/357224783/figure/fig4/AS:1103500331233288@1640106389680/a-Schematic-representation-of-a-NH3-amperometric-sensor-Reproduced-with-permission.png)
(a) Schematic representation of a NH3 amperometric sensor. Reproduced with permission from [64]. (b) Current response on the applied voltage for different ammonia concentrations at 400 °C. x is the NH3 concentration in vol.%. (c) The relation between the limiting current and different NH3 concentrations and (d) current-voltage curves for different temperatures for 5 vol.% ammonia. Reproduced with permission from [64].
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The rapid development of science, technology, and engineering in the 21st century has offered a remarkable rise in our living standards. However, at the same time, serious environmental issues have emerged, such as acid rain and the greenhouse effect, which are associated with the ever-increasing need for energy consumption, 85% of which comes from...
Contexts in source publication
Context 1
... cells are glued together with the aid of a glass sealant. The configuration of this sensor is depicted in Figure 6a. Catalysts 2021, 11, x FOR PEER REVIEW 20 of 32 Amperometric NH3 Sensors ...
Context 2
... cells are glued together with the aid of a glass sealant. The configuration of this sensor is depicted in Figure 6a. During the experiment, the sensor was placed in the NH3 + N2 gas mixture. ...
Context 3
... a calibration curve (limiting current vs. NH 3 concentration) is obtained for the determination of ammonia in N 2 + NH 3 gas mixtures. Figure 6b shows the sensor's current response for a wide range of N 2 + NH 3 mixtures plotted against the applied voltage. In these curves, three different regions are distinguished. ...
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... already discussed, one of the main advantages of amperometric sensors is the linear relation between the limiting current and the target gas concentration under isothermal conditions. This function should be close to the linear one, according to Equation (35); as observed from Figure 6c, this condition is satisfied for the tested sensor. Thus, it is suitable for the detection of ammonia. ...
Citations
... Electrochemical sensors based on solid-state electrolytes are analytical devices capable of addressing the aforementioned issues since they present advantages like low manufacturing costs [12], high temperature and on-site measurement [13], ease of use [12], stability [13], good signal-to-noise ratio [14], and excellent repeatability and accuracy [15]. ...
... Electrochemical sensors based on solid-state electrolytes are analytical devices capable of addressing the aforementioned issues since they present advantages like low manufacturing costs [12], high temperature and on-site measurement [13], ease of use [12], stability [13], good signal-to-noise ratio [14], and excellent repeatability and accuracy [15]. ...
... Conversely, electrochemical gas sensors are cheap, simple in structure, small, energy-efficient, and stable, and provide a fast response, strong linearity, high sensitivity, and high selectivity; as such, they are widely used for safety monitoring, environmental protection, food safety, and in industry [19,20]. Currently, studies on electrochemical sensors have mainly focused on the structure of the sensor, the material of the working electrode, and the material of the electrolyte [21][22][23][24][25]; however, few studies have been conducted on the engineering applications of electrochemical sensors. In practical engineering applications, the electrochemical sensors that are used to monitor the concentration of pollutants emitted by coal-fired power plants suffer from a low measurement accuracy and short service life. ...
To overcome the limitations of NO2 electrochemical sensors, including their inaccurate measurements and short working life, when used around coal-fired power plants, we investigated the influence of coal-fired fly ash deposition on the measurement error of NO2 electrochemical sensors through experimental tests. The morphological characteristics and pellet diameter distribution of coal-fired fly ash pellets were determined via scanning electron microscopy. The sedimentation velocity of coal-fired fly ash pellets in the air was determined through theoretical calculations of aerodynamics and hydrodynamics. Additionally, the effect of the deposition of coal-fired fly ash on the measurement error of NO2 electrochemical sensors was determined through experimental tests. The test results show that the minimum and maximum measurement errors of the NO2 electrochemical gas sensor were 8.015% and 30.35%, respectively, after a deposition duration of 30 days with 30 mg/m3 coal-fired fly ash. This demonstrates that coal-fired fly ash deposition is the cause of the inaccurate measurements and short working life of these sensors. Coal-fired fly ash causes a decrease in the gas diffusion area of the sensor and the diffusion coefficient, thus increasing the sensor measurement error.
... 9 At elevated temperatures, oxygen ions migrate through as-formed vacancies in solid electrolytes under an electrochemical potential difference, which enables sensor operation. 10,11 Most commercialized zirconia oxygen sensors are designed to measure oxygen concentrations in exhaust gas and combustion environments. However, they are inappropriate for hydrogen atmospheres because of the risk of explosions caused by high heating temperatures and the need for reference oxygen gases or air supply. ...
Potentiometric oxygen sensors with excellent sensitivity in a low oxygen concentration range are designed based on intrinsic logarithmic response characteristics, and an asymmetric electrode structure, differentiated from conventional oxygen sensors with reference oxygen gases or parts exposed to air, is implemented. Electrolytes and electrode materials that formulate oxygen sensor devices are evaluated by comprehensively considering their reactivity to trace oxygen, oxygen ion formation, and ease of movement. The sensor using an yttria-stabilized zirconia bulk ceramic electrolyte measures the oxygen concentration in an oxygen-hydrogen mixture down to 0.5%, with a response time of 7.8 s. The sensor with a Nafion proton conductor film and a polyimide gas separation membrane allows room-temperature sensing and measures the oxygen concentration to a minimum of 2%.
... Solid electrolytes play a predominant role in NH 3 electrochemical sensors as charge transfer media that are not only resistant to high temperatures, but also have good selectivity for quantitative analysis of gases [88,113,114]. As early as 1897, Nernst discovered that ceramics based on mixed oxides could conduct charge at high temperature, creating the Nernst lamp, which was the first application of solid ceramic electrolytes [115]. Wagner [116] made a study and summary of the conduction mechanism of solid electrolytes in 1943. ...
Being widely used as a toxic gas in chemical production, medical applications, agricultural production and automotive industry, ammonia not only poses a great threat to atmospheric pollution when exposed to the atmosphere, but also can cause damage to the life safety of animals or humans. To ensure the safe and accurate use of ammonia in various fields, especially in selective catalytic reduction (SCR) systems for automobiles and boilers, a high-performance ammonia sensor is necessary. Solid-state electrolyte sensors are deemed to be excellent performers for high-temperature environments in automobiles and boilers. We have been looking at how ammonia sensing has evolved over time, and it is clear that mixed potential sensors have a lot to offer high-temperature ammonia detection. In this review, the classification, sensing mechanism, materials and development trends of solid-state ammonia sensors are detailed, and it also discusses the current sensing performance of solid-state ammonia sensors and the way forward for their optimization. Although the performance of present ammonia sensors has been improved by the thorough research of scientists, there remains more room for development in sensitivity, selectivity and response/recovery time. Improving the three-phase boundary, increasing the active sites and reducing the cross-sensitivity will be part of the future development trend of ammonia sensors.
Graphical abstract
... Electrochemical sensors that use a solid-oxide electrolyte can be effectively used for hydrogen detection. Solid-oxide sensors operate at high temperatures (typically, above 450 • C), because the solid-oxide electrolytes demonstrate an appropriate ionic conductivity only at high temperature [7,8]. Electrochemical sensors are usually divided into impedancemetric, potentiometric, and amperometric sensors [7,9,10]. ...
... Solid-oxide sensors operate at high temperatures (typically, above 450 • C), because the solid-oxide electrolytes demonstrate an appropriate ionic conductivity only at high temperature [7,8]. Electrochemical sensors are usually divided into impedancemetric, potentiometric, and amperometric sensors [7,9,10]. The impedancemetric sensors require the use of a high-cost apparatus, namely a high-frequency AC signal source and a frequency response analyzer; in addition, changes in the electrode microstructure and electrical properties during operation influence the sensor response [11]. ...
... However, for the potentiometric sensor operation, it is necessary to supply a reference gas to the reference electrode, and this complicates the design of the sensors; additionally, their performance is sensitive to changing electrode behavior in a way similar to that of the impedancemetric sensors [12][13][14]. Amperometric-type sensors operate in the diffusion-limited mode, when the current is controlled by diffusion and independent of the working electrode potential [7]. Amperometric sensing is a low-cost and simple to use technology, which is widely applied to the measurement of different gas components. ...
Citation: Kalyakin, A.; Volkov, A.; Dunyushkina, L. Solid-Oxide Amperometric Sensor for Hydrogen Detection in Air. ChemEngineering 2023, 7, 45. https://doi.org/10.3390/ chemengineering7030045 Academic Editor: Massimiliano Lo Faro Abstract: An amperometric sensor based on CaZr 0.95 Sc 0.05 O 3−δ (CZS) proton-conducting oxide for the measurement of hydrogen concentration in air was designed and tested. Dense CZS ceramics were fabricated through uniaxial pressing the powder synthesized by the solid-state method and sintering at 1650 • C for 2 h. The conductivity of CZS was shown to increase with increasing air humidity, which indicates the proton type of conductivity. The sensor was made from two CZS plates, one of which had a cavity was drilled to form an inner chamber, that were then pressed against each other and sealed around the perimeter to prevent gas leaking. The inner chamber of the sensor was connected with the outer atmosphere via an alumina ceramic capillary, which acted as a diffusion barrier. The sensor performance was studied in the temperature range of 600-700 • C in the mixtures of air with hydrogen. The sensor signal, or the limiting current, was found to linearly increase with the hydrogen concentration, which simplifies the sensor calibration. The sensor demonstrated a high sensitivity of~60 µA per 1% H 2 at 700 • C, a fast response, high reproducibility, good selectivity, and long-term stability.
... However, a real time monitoring of over-injected and unreacted NH 3 from the SCR system and direct ammonia fuel cells is necessary in order to prevent the escaping NH 3 to be an environmental pollutant. So far, compared with various sensing techniques for gaseous NH 3 , the solid-electrolyte based electrochemical sensor has been promising due to good sensitivity, wide operating temperature, and simple operation process [11,12]. ...
... 6), diffusion based mass transport kinetics and linear approximation of ORR at low overpotentials can be assumed by the following the relationships in Eqs. (11) and (12). ...
Real-time monitoring and quantification of exhaust pollutants is crucial but is troublesome because of extremely harsh thermochemical conditions, and in this regard mixed-potential sensing technology can be a realistic solution. In this study, BiVO4 nanoparticles are decorated onto the preformed porous sensing electrode (SE) backbone by homogeneous infiltration process to improve the sensing performance in mixed-potential sensor. The influence of nanoparticle decoration on phase composition, microstructure and sensing performance are analyzed by physical and electrochemical techniques. Corresponding results indicate that the microstructure tailoring enhances the sensor performance, by extending the triple phase boundary (TPB) and surface area of SE itself. The sensitivity (-119.47 mV/decade) and response time (20 s) of i-BVO SE-based sensor at 600 ℃ are 20 % higher and 8 s faster than bare BiVO4 SE-based sensor (99.24 mV/decade and 28 s). Additionally, the i-BVOǀYSZǀPt cell exhibits good selectivity and cross-sensitivity toward NH3 without any dependency on oxygen partial pressure (pO2). The fabricated sensor is also found stable towards cyclic and long-term operations. Electrochemical Impendence Spectroscopy (EIS) and DC polarization studies were performed to confirm the mixed-potential behavior. Conclusively, the superior sensing performance of i-BVO SE compared to various oxide based SEs highlights its suitability for mixed-potential NH3 sensing.
... To detect a relatively high concentration of the analyzed components, the so-called amperometric-type sensors can be employed. In detail, the ZrO2-based amperometric sensors have recently been used for measuring the contents of O2, H2, CO2 and H2O in inert gases [9][10][11][12][13]. The reading parameter of such sensors is a limiting current, representing an electrical equivalent of the concentration and diffusion parameters of the analyzed gas media. ...
... It is important to note that the flow of the analyzed combustible gas entering the cavity of the electrochemical cell is limited by the diffusion barrier (capillary), which governs the limiting current value. Therefore, the measured limiting current is a function of the concentration of the measured hydrocarbon in the analyzed gaseous medium, temperature and geometrical parameters of the diffusion barrier according to the following equation [13]: ...
Solid-state gas sensors composed of complex oxide electrolytes offer great potential for analyzing various atmospheres at high temperatures. While relatively simple gas mixtures (H2O+N2, O2+N2) have been successfully studied by means of ZrO2-based sensors, the precise detection of more complex compounds represents a challenging task. In this work, we present our findings regarding the analysis of lower alkanes (CH4, C2H6, and C3H8) mixed with nitrogen as an inert gas, utilizing an amperometric ZrO2-based sensor. This sensor, serving as an electrochemical cell with a diffusion barrier, was tested at 500–600 °C to measure the limiting current, which depends on the gas composition and can be further used as a basis for calibration curves. In addition, the diffusion coefficients of the specified gas mixtures were successfully found and compared with references, confirming the applicability of the fabricated sensor for studying diffusion processes in wide concentration and temperature ranges.
... The hydrogen sensors are presented according to their type of operational principle, i.e., potentiometric, amperometric, and combined amperometricpotentiometric. For more details on the fundamental principles of high-temperature gas detection sensors, the readers are referred to a previously reported, more extensive, comprehensive review [10]. ...
... Focusing on hydrogen sensors, the different partial pressures of hydrogen at each compartment correspond to different chemical potentials due to the varying concentrations of the hydrogen ions, thus generating an electromotive force (EMF) in the cell. The EMF is the sensor's open circuit voltage (OCV), meaning the potential difference between SE and RE, and can be calculated by the Nernst equation [10,21]: ...
... Therefore, a potential lying between the equilibrium potentials of the two compartments is formed. In this case, the observed non-Nernstian potential provides information about the hydrogen in a gas mixture [10,21,26]. Generally, mixed potential hydrogen sensors use YSZ as a solid electrolyte and platinum as a reference electrode (RE). ...
Hydrogen sensors, especially those operating at high temperatures, are essential tools for the emerging hydrogen economy. Monitoring hydrogen under process conditions to control the reactions for detecting confined species is crucial to the safe, widespread use and public acceptance of hydrogen as fuel. Hydrogen sensors must have a sensitivity ranging from traces of hydrogen (parts per million (ppm)) up to levels near the lower explosive limit (LEL = 4% H2 in the air) for safety reasons. Furthermore, they need to operate in cryogenic, ambient, and high-temperature
environments. Herein, emphasis is given to hydrogen sensors based on solid oxide electrolytes (operating at high temperatures), in particular oxygen ion and proton conductors. The review is devoted to potentiometric, amperometric, and combined amperometric-potentiometric hydrogen sensors. Experimental results already reported in the international literature are presented and analyzed to reveal the configuration, principle of operation, and the applied solid electrolytes and
electrodes of the high-temperature hydrogen sensors. Additionally, an amperometric sensor able to detect hydrogen and steam in atmospheric air through a two-stage procedure is presented and thoroughly discussed. The discussion reveals that high-temperature hydrogen sensors face different challenges in terms of the electrodes and solid electrolytes to be used, depending on the operating
principle of each sensor type.
... Potentiometric and amperometric solid electrolyte sensors for oxygen control are widely used in energetics, metallurgy and transport [1][2][3][4][5]. The designs of different types of oxygen sensors and their utilized materials are described in previously published works [5][6][7][8][9][10], while the investigations of sensors for humidity determination based on solid electrolytes with oxygen ion [11,12] and proton [13][14][15][16][17] conductivity, as well sensors based on a combination of both types of solid oxide electrolytes [18] have been performed successfully. For instance, the humidity value was determined by analyzing a ratio of the second limiting current to the first one. ...
... It is seen that the limiting current dependence on the steam concentration is weaker (lower slope) than that on the hydrogen concentration. Moreover, as can be seen, at the same time, the experimental data of both dependences are very close to the theoretically-calculated lines according to Equation (10). The measurement of the limiting current dependence in the case of the humidified H2 + air mixture was performed. ...
... Volt-ampere dependences of the sensor in air with different humidity (a); and dependences of the limiting currents on the steam concentration in air (rectangles), hydrogen concentration in dry air (circles) and hydrogen concentration in humid (3.3%) air (triangles) (b). Symbols are the experimental data; straight lines are theoretically calculated according to Equation(10). ...
The present communication describes the results of the performance and the assessment of a sensor based on a solid oxide electrolyte with a composition of 0.9ZrO2 + 0.1Y2O3 (YSZ), equipped with a ceramic diffusion barrier for measuring the water vapor and hydrogen content in air. The possibility of determining the concentration of water vapor and hydrogen in the air is based on the measurement of the limiting current value. For the calculation of the steam and hydrogen concentration in ambient air, analytical expressions were obtained and applied, using the limiting current values measured in air with a standard oxygen concentration of 20.9 vol.% and in the analyzed air. A two-stage method for the determination of the hydrogen and steam amount in ambient air is proposed. It is stated that the sensor operates successfully at the temperature of 700 °C and can be applied for the continuous determination of steam or hydrogen concentrations in air.
... Gorbova et al. reviewed the high-temperature EGSs applications and reported that the potentiometric sensor with an electrolyte [107], generally is a tube covered with two electrodes, in which, one is internal side i.e., reference electrode (RE) and another is external side, i.e., sensing electrode (SE), as shown in Fig. 9a and b. When a potentiometric sensor is in gas, the potential at SE reached equilibrium, which depends on the concentration of the target gas. ...
... Amperometric gas sensors were also reported by Gorbova et al. [107], in which, reactions at the electrodes are driven by an external voltage. Fig. 9c and d presents the schematic mechanism of a typical amperometric sensor, in which, (1) diffusion barrier, (2) solid electrolyte, (3) cathode, (4) anode, and (5) target gas [112]. ...
... As for the future research directions, YSZ is one of the most effective electrolytes employed in many electrochemical sensors for the detection of gasses, such as H 2 , CH 4 , and CO, NO x , NH 3 , and O 2 , and can be withstand temperatures up to 1200 • C [107]. It is potential to detect pyrolysis gases, such as H 2 , CH 4 , and CO with the gas concentration from 0 to 6%, which can be a type of gas sensors potentially applied in pyrolysis and gasification. ...
Pyrolysis is one of the most efficient and sustainable technologies for converting biomass, solid waste into valuable bioenergy products to achieve future-oriented synthetic energy. As the intelligent automation control has been rapidly developing recently, it is desired to control and adjust the operating parameters in each feedstock reaction stage by accurately measuring the temperatures, pressures, and the produced gas quantity and compositions. This study reviews comprehensively pressure and gas sensors that are applied or potentially applied in pyrolysis. It was found that the operating temperature and reactor pressure are critical parameters affecting the yields and quality of pyrolysis products. Gas sensors can be used to detect various gases and vapors, such as methane, hydrogen, carbon monoxide, and dioxide, to estimate the quality, quantity, and compositions of gas products for their further utilizations during the pyrolysis and upgrading. According to the sensing data of the gas products, operating parameters of the pyrolysis and upgrading processes can be adjusted and optimized to enhance the pyrolysis efficiency and quality of synthetic energy products. As for the performances of available gas sensors, many of them can withstand temperatures up to 1000 • C and have advantages of good selectivity and stable for long-time, which can be utilized for pyrolysis and upgrading processes. The authors' group will develop high temperature wireless SAW gas sensor for monitoring the major gases in the reactor during pyrolysis and upgrading processes and enhance the efficiency of syn-gas production and gas quality via sensing.
