Electrochemical Carbon Monoxide Sensor Research Articles

Design of a mining carbon monoxide sensor and analysis of multi-gas cross-interference performance

Abstract A new type of carbon monoxide sensor is designed to address the issue of cross interference of nitrogen oxide gas in the exhaust emissions of underground diesel engine rubber-tired vehicles with electrochemical carbon monoxide sensors, which leads to frequent false alarm accidents. The hardware circuit design of the DC-DC voltage reduction power supply circuit, display circuit, component signal processing circuit, etc. is detailed, At the same time, the sensitive components used in the sensor adopt a special gas filtration membrane design. Six types of gases, including hydrogen sulfide, nitric oxide, nitrogen dioxide, hydrogen, ethylene, and acetylene, were sequentially introduced in the laboratory for experimental analysis of multi-gas cross-interference performance. The experimental results have shown that the new carbon monoxide sensor can filter out nitrogen oxide gas, thereby solving the impact of underground rubber tire vehicle exhaust on the accuracy of carbon monoxide gas detection. It has broad prospects for promotion and application in coal mines underground.

Understanding the effect of temperature and relative humidity on sensor sensitivities in field environments and improving the calibration models of multiple electrochemical carbon monoxide (CO) sensors in a tropical environment

The data quality of low-cost air quality monitoring sensor systems in field environments needs to be improved through calibrations to compare with regulatory data. This research study focused on improving linear regression calibration models of multiple Alphasense CO-B4 sensors compared to the factory calibration, evaluating the sensor sensitivity and calibration model variations in different temperature and relative humidity (RH) ranges, evaluating the unit-to-unit variability of sensor performances and the use of averaged calibration models instead of individual calibration models. In this study, changes were observed in field sensor sensitivities and manufacturer-given sensor sensitivities, and the inclusion of field sensor sensitivities improved the calibration model performances significantly. Sensor calibration models performed best in the temperature range of 20–24 0C and the RH range of 75–90%, with averaged r and RMSE values around 0.98 and 50 ppb. When compared with raw sensor data (RMSE = 172.1 ppb), the averaged RMSE values of the calibrated concentration values were 97.4 ppb or below for different calibration models. Additionally, results clearly illustrated that the use of averaged calibration model was a reliable alternative for individual calibrations. Furthermore, it was observed that the field calibrations significantly reduce the effect of temperature and RH on sensor outputs and improve the factory calibrations.

Evaluation of gas and particle sensors for detecting spacecraft-relevant fire emissions

Fire detection faces challenges of increasing sensitivity, accuracy, and response speed while reducing false alarms. Air quality sensors measure fire emission signatures similar to smoke detectors but are often more sensitive. Recent advancement in air quality sensors provides an opportunity to improve fire detection. This study used low-cost and research-grade gas and particle sensors to detect and characterize emissions from laboratory smoldering and flaming tests of three spacecraft-relevant materials. The electrochemical carbon monoxide (CO) sensor sensitively detected fire emissions in all but a pyrolysis test, whereas the metal oxide volatile organic compound (VOC) sensor with cross sensitivity for CO detected fire emissions in all tested cases. Several low-cost particle sensors, although saturated at high concentrations, detected smoke at low concentrations. A combination of CO/VOC and particle sensors would provide sensitive fire detection distinct from non-combustion nuisance sources. In support of the ongoing Spacecraft Fire Safety Experiments (Saffire), the DustTrak DRX aerosol monitor was evaluated for smoke measurement. It measured particle concentrations over a wide range and its single particle counting provided additional size distribution data similar to that of an optical particle counter. However, the single particle counting accuracy degraded at high concentrations due to coincidence errors.

The Influence of Hydrogen on the Indications of the Electrochemical Carbon Monoxide Sensors

This article examines electrochemical carbon monoxide (CO) sensors used as mobile devices by rescue and firefighting units in Poland. The conducted research indicates that the presence of chlorine (Cl2), ammonia (NH3), hydrogen sulfide (H2S), hydrogen chloride (HCl), hydrogen cyanide (HCN), nitrogen (IV) oxide (NO2), and sulfur (IV) oxide (SO2) in the atmosphere does not affect the functioning of the electrochemical CO sensor. In the case of this sensor, there was a significant cross effect in relation to hydrogen (H2). It was found that the time and manner of using the sensor affects the behavior in relation to H2. Such a relationship was not recorded for CO. Measurements in a mixture of CO and H2 confirm the effect of hydrogen on the changes taking place inside the sensor. Independently of the ratio of H2 to CO, readings of CO were flawed. All analyses showed a significant difference between the electrochemical CO sensor readings and the expected values. Only in experiments with a 1:3 mixture of CO and H2 was the relative error less than 15%. The relative error in the analyzed concentration range for a sensor with an additional compensation electrode ranged from 7% to 38%; for a sensor without this electrode, it ranged from 23% to 55%. It was ascertained that in the cases of measurements for tests carried out at higher concentrations of H2 in relation to CO, a sensor with an additional electrode is significantly better (more accurate) than a sensor without such an electrode. Differences at the significance level p = 0.01 for measurements made in the CO:H2 mixture at a ratio of 1:3 were ascertained.

Highly sensitive amperometric CO sensor using nanocomposite C-loaded PdCl2–CuCl2 as sensing electrode materials

A novel C-loaded PdCl2–CuCl2 electrode material was prepared by the facile method without the use of any additive or organic active agent. It was used to fabricate a solid-state planar electrochemical carbon monoxide sensor. The effect of the working electrode used in amperometric gas sensors on the performance of sensitivity, detection limit was evaluated. The results showed that the sensor has characteristics of a practical-use level: response time, 10s; range, 0–100ppm; sensitivity, 0.35μA/ppm.

Dynamic Calibration of Electrochemical Sensor for Accelerated Analyte Quantification

The conventional sensor calibration aims at mathematically relating the steady-state sensor responses to the target analyte concentrations to realize environment monitoring. However, commonly used chemical sensors usually require a relatively long time (say, minutes) to reach a steady state, and exhibit delayed responses when the analyte concentration changes quickly over time. To reduce the lag time and achieve real-time monitoring, this paper takes a statistical modeling approach. Based on the experimental data collected following the proposed design of experiments strategies, transfer function models are estimated to calibrate the dynamic behavior of a sensor. Such dynamic calibration models enable the use of transient sensor signals (as opposed to the steady-state responses) to track the rapid change in the target analyte concentration. In this paper, the dynamic modeling method is employed to calibrate a high-temperature electrochemical carbon monoxide (CO) sensor, and the empirical results have shown that the proposed method can reduce the time lag of a sensor by an order of magnitude (from minutes to seconds) compared with the steady-state calibration.

Electrospun La0.8Sr0.2MnO3 nanofibers for a high-temperature electrochemical carbon monoxide sensor

Lanthanum strontium manganite (La0.8Sr0.2MnO3, LSM) nanofibers have been synthesized by the electrospinning method. The electrospun nanofibers are intact without morphological and structural changes after annealing at 1050 °C. The LSM nanofibers are employed as the sensing electrode of an electrochemical sensor with yttria-stabilized zirconia (YSZ) electrolyte for carbon monoxide detection at high temperatures over 500 °C. The electrospun nanofibers form a porous network electrode, which provides a continuous pathway for charge transport. In addition, the nanofibers possess a higher specific surface area than conventional micron-sized powders. As a result, the nanofiber electrode exhibits a higher electromotive force and better electro-catalytic activity toward CO oxidation. Therefore, the sensor with the nanofiber electrode shows a higher sensitivity, lower limit of detection and faster response to CO than a sensor with a powder electrode.

Sensitive and Selective Electrochemical Detection of Carbon Monoxide in Saline at a Pt-Ru/Nafion/MnO2-Modified Electrode

We fabricated a sensitive and selective electrochemical carbon monoxide (CO) sensor for physiological conditions based on the Pt-Ru system. At a bare Pt-Ru electrode, a linear amperometric response to CO concentration was obtained in the range of 0.9-9 µM. However, significant current response to model electroactive interferents for physiological conditions, uric acid (UA), ascorbic acid (AA) and hydrogen peroxide (HP), was also recorded at the Pt-Ru electrode. The response to UA and AA was highly suppressed by coating the Pt-Ru electrode surface with a Nafion layer, and the response to HP was almost completely eliminated by the additional coating with a MnO(2)/chitosan layer. Finally, at the Pt-Ru/Nafion/MnO(2) electrode, amperometric CO detection with a sensitivity of 173 nA cm(-2) µM(-1) was obtained in the concentration range of 0.9-9 µM with the UA, AA and HP signal being below 1.7% at the same concentration of CO.

Knowledge-based genetic algorithms data fusion and its application in mine mixed-gas detection

In Considering that the high concentration of mine gas and hydrogen will disturb the output of electrochemical carbon monoxide sensor, this paper integrates gas sensor array with data fusion Algorithm. The output signals of three sensors are trained by BP neural network to get the mathematical model of information fusion for the analysis of mixed gas of methane, hydrogen and carbon monoxide. The experiments show that the information fusion could correct the crossed sensitivity error, and improve the accuracy of carbon monoxide, therefore achieve quantitative analysis mixed gas of coal mine.

Detection of Carbon Monoxide Production as a Result of the Interaction of Five Volatile Anesthetics and Desiccated Sodalime with an Electrochemical Carbon Monoxide Sensor in an Anesthetic Circuit Compared to Gas Chromatography

There is a continuing risk of production of toxic levels of carbon monoxide (CO) as a result of interaction of volatile anesthetics and desiccated strong base carbon dioxide absorbents like soda lime. The aim of this study is to establish the reliability of detection of CO levels by an electrochemical carbon monoxide sensor compared to gas chromatography. Completely desiccated sodalime was conducted through a circle anesthesia system connected to an artificial lung. For different rates of CO production, a low flow anesthesia with a oxygen/nitrous oxide mixture was maintained using five volatile anesthetics. For quantification of CO production, a portable gas chromatograph (GC) was connected to this setup, as well as a Bedfont EC40 electrochemical carbon monoxide sensor (ES) with a claimed reliable sensitivity of 0-200 parts per million (ppm) and a maximum detection range of more than 5500 ppm. To assess the agreement between the GC and ES measurements the intra class correlation coefficient (ICC) and the 95% limits of agreement were calculated. Bland and Altman scatterplots were made to visualize the difference between measurements. For concentrations up to 200 ppm, no significant differences between the GC and ES mean CO measurements were found in the halothane experiments. However CO was not accurately measured at every moment during these experiments by the ES. For concentrations above 200 ppm the results of the two instruments differed significantly. The ES malfunctioned when exposed to sevoflurane and desiccated sodalime. From these data we conclude that the ES can only be used as an indicator of CO production. When this sensor is used with sevoflurane and desiccated sodalime it is not capable of normal operation. The use of a strong base free carbon dioxide absorbent is therefore recommended.

AC impedance characteristics of solid-state planar electrochemical carbon monoxide sensors with Nafion® as solid polymer electrolyte

The AC impedance characteristics of planar solid-state electrochemical carbon monoxide (CO) sensors with Nafion® as the solid polymer electrolyte are reported. For a re-cast Nafion® sensor design, Nyquist plots indicated very high impedances (10 7–10 8 Ω), which slightly decreased with an increase in the working electrode surface area (0.25–0.50 cm 2). Only one enlarged semi-circle was observed, relating to an equivalent circuit with a geometrical capacitance ( C g) in parallel with a bulk resistance ( R b). In contrast, a sensor design using a commercial membrane produced a system with a much lower impedance (<10 3 Ω), with Nyquist plots showing a flattened semi-circle at high frequencies (due to C g and R b in parallel), followed by the start of a large semi-circle (due to the double-layer capacitance, C dl, in parallel with the charge-transfer resistance, R ct) over a lower frequency range. On addition of CO, the second circular arc reduced in size, indicating that the interfacial impedance of the electrochemical system had decreased.

Investigation of a Planar Electrochemical Carbon Monoxide Sensor Using AC Impedance Spectroscopy

A planar solid‐state electrochemical carbon monoxide (CO) sensor has been designed, with screen printed electrodes (platinum as the working and counter electrodes, gold as the reference electrode) and a recast film of a sulfonated styrene/ethylene‐butylene/styrene triblock copolymer as the proton conducting solid polymer electrolyte. AC impedance spectroscopy has been found to be a highly sensitive technique for the quantitative characterization of sensor response. A standard equivalent circuit that included the polymer electrolyte and interfacial impedances was employed to fit the ac impedance spectroscopy data in both clean air and in the presence of CO. Chemisorption of CO onto the catalytic platinum electrode surface resulted in a decrease in charge‐transfer resistance with an increase in gas concentration. This change in interfacial impedance was due to a limited amount of CO oxidation occurring due to the polarizing effect of the 10 mV ac amplitude utilized during the ac impedance spectroscopy scan. The sensors did not respond to an atmosphere containing methane, while hydrogen, which readily adsorbs onto the surface of a platinum catalyst, did perturb the ac impedance from the plot obtained in clean air. © 2000 The Electrochemical Society. All rights reserved.

Electrochemical carbon monoxide sensor with a Nafion ® film

A solid-state planar electrochemical carbon monoxide sensor was built and studied. The sensor features a planar geometry of the electrodes (working, counter, reference), where all three electrodes are located on the same side of a substrate. The electrodes are covered by the CO-semipermeable proton-conducting polymer film. The sensor shows characteristics of a practical-use level: response time, 30 s; range, 0–2000 ppm; sensitivity, 0.04 nA/ppm; life, more than 2 yr. The sensitivity is governed by both the CO permeability of the polymer film and the CO oxidation rate, in other words, by the intermediate kinetic mechanism.

Amperometric Gas Sensor Response Times

This work examines the relative importance of diffusion and the electrical time constant of the working electrode on the response time of amperometric gas sensors. The response curve of an electrochemical carbon monoxide sensor to a 200 ppm CO test gas was measured as a function of the added resistance that is in series with the working electrode to increase the time constant. It has been found that the response time increases with additional resistance. The experimental behavior was compared to the values predicted on the basis of Fick's second law of diffusion and to the values expected on the basis of the electrical properties of the sensor. The behavior of the sensor was explained using an equivalent electrical circuit, describing the time constants of the working electrode. Values obtained from this model were further compared to experimental values obtained from electrochemical impedance spectra. It has been found that the response time of the sensors depends on both the rate of diffusion and the electrical time constants of the working electrode.

The effect of hyperbaric pressure on catalytic and electrochemical gas sensors

Sensors commonly used in workplace multi-gas monitors, and normally operating at atmospheric pressure, have been evaluated under the pressurized (hyperbaric) atmospheres typically found in tunnelling operations, i.e., 1–4.5 bar (100–450 kPa) static pressure and pulses of up to 0.3 bar (30 kPa) above ambient pressure and of less than 30 s duration. Three types of sensor have been tested: catalytic sensors (pellistors) for methane, electrochemical fuel cells for carbon monoxide and electrochemical metal-air batteries for oxygen. All the sensors are affected by pressure to some degree. Pellistors show a positive pressure effect (response increases by up to 50% at 3 bar), while pulses up to 0.3 bar produce transient responses equivalent to 0.2% methane. The electrochemical carbon monoxide sensors are unaffected by pressure in clean air but there is a positive effect in carbon monoxide/air (the sensor reads approximately 11% high at 3 bar). During compression and pulsing in carbon monoxide/air larger effects are observed. The electrochemical oxygen sensor behaves similarly to the carbon monoxide sensor: at 3 bar the sensor reads 12% high, while pulses of the order of 0.1 bar above ambient induce a 25% increase in response. The effects of static hyperbaric pressure can be overcome by recalibration of the sensors at the working pressure. Transient effects on electrochemical sensors can be reduced by careful siting of the sensor away from pressure-pulse sources or possibly by the incorporation of auxiliary diffusion barriers into the sensor. The effects of pressure on the sensor characteristics are compared with theoretical models.

Mechanism of the Sensitivity of the Planar CO Sensor and Its Dependency on Humidity

A planar electrochemical carbon monoxide sensor was fabricated with three electrodes (Pt working, Au reference, and Pt counterelectrode), upon a glass substrate with the electrodes coated with a cast Nafion film. The oxidation current, the impedance between working and counterelectrodes, and the permeability coefficient of a Nafion film were measured from 18 to 83% relative humidity (RH) of air. The observed oxidation current was derived from the measured permeability coefficient. By comparing the observed and calculated currents, the dependency of the oxidation current on RH was shown to be related to the change of the permeability coefficient and the water content of Nafion. The kinetic analysis also showed that the oxidation current was governed by the intermediate kinetic mechanism.

The constant potential amperometrical response of the planar electrochemical carbon monoxide sensor

A planar electrochemical carbon monoxide sensor, which comprised three electrodes (working, counter and reference) on a substrate and a polymer electrolyte layer on them, was built and studied. The working and counter electrodes were made with platinum, while the reference electrode was made with gold. The polymer electrolyte layer was made by casting a copolymer from tetrafluoroethylene and perfluoro-3,6-dioxa-4-methyl-7-octenesulfoxide solution. The response to CO in air was studied by constant potential amperometry. The highest CO oxidation current was observed at 0.4 V versus Au built-in reference and a sensitivity of 0.04 nA /ppm was obtained. However, the proportionality of response was limited up to 700 ppm and the response was dependent on the relative humidity of the air.

Electrochemical characteristics of the planar electrochemical carbon monoxide sensor with a perfluorosulfonate ionomer film

Planar electrochemical CO sensors were fabricated and studied. The sensors comprised three electrodes (working, counter and reference) on a substrate and a solution-cast protonated perfluorosulfonate ionomer film, which covered three electrodes and a substrate. The electrochemical characteristics of the present sensors were studied by cyclic voltammetry. It was confirmed that the present sensor worked electrochemically well and detected CO in air by oxidation current.