A galvanic gas sensor using poly (ethylene oxide) complex of silver trifluoromethane sulphonate electrolyte

Summary A galvanic sensor for monitoring nitrogen dioxide was developed by using a poly(ethylene oxide) complex of silver trifluoromethanesulphonate electrolyte. The sensor, which is expressed as Au/P(EO)_4.5 AgCF₃SO₃/Ag, is a small disk (i.d. 13 mm). The polymeric electrolyte film was made by casting the mixture of acetonitrile solutions of both P(EO) (MW 6×10⁵) and AgCF₃SO₃. The working electrode was made by sputtering of gold in argon. The thicknesses of the desposited gold, polymeric electrolyte film and silver are 25 nm, 30 m and 1 mm, respectively. When the sample gas containing nitrogen dioxide impinges at 20 ml min^–1 on the gold cathode, the current flowing in the external circuit was linearly related to the concentration of nitrogen dioxide from 20 ppb to about 10 ppm. The current efficiency of the cell was 0.051%. The cell's response time was about 2 min for 0.5 ppm of nitrogen dioxide.     

Optimizing zirconia-based solid electrolyte cell operated as oxidizing reactor and chromatographic sensor

A zirconia-based (0.9ZrO₂ · 0.1Y₂O₃) high-temperature electrochemical reactor with three-electrode connection circuit was shown promising if used as a chromatographic sensor for quantitative organic gas detection as well as an organic gas sample preparation device for carbon isotopic analysis. The optimized parameters and working mode of the herein proposed solid electrolyte reactor provided complete organic gas oxidation to stoichiometric oxides without oxygen addition to the carrier gas flow at the temperature of 900 to 950°C. The maximum hydrocarbon gas sample amount was calculated for complete oxidation in the designed reactor. Due to its simple and reliable design, the solid electrolyte reactor can be used instead of a standard oxidizing reactor in an isotopic mass spectrometer.     

Selective oxidation using catalyst electrodes supported on solid electrolyte

The major oxygenated products of the selective oxidation of 1-butene by using a catalyst electrode were maleic anhydride on V₂O₅/YSZ/Ag and butadiene on MoO₃–Bi₂O₃–Ag/YSZ/Ag. Their selectivities were enhanced as compared with the non-electrochemical system.     

Properties of composite solid polymer electrolyte using hyperbranched polymer with ether-linkage

The cross-linked composite solid polymer electrolytes composed of poly(ethylene oxide), lithium salt (LiN(SO₂CF₃)₂), and a hyperbranched polymer whose repeating units were connected by ether-linkage (hyperbranched polymer (HBP)-2) were prepared, and their ionic conductivity, thermal properties, electrochemical stability, mechanical property, and chemical stability were investigated in comparison with the non-cross-linked or cross-linked composite solid polymer electrolytes using hyperbranched polymers whose repeating units were connected by ester-linkage (HBP-1a, 1b). The cross-linked composite solid polymer electrolyte using HBP-2 exhibited higher ionic conductivity than the non-cross-linked and cross-linked composite solid polymer electrolytes using HBP-1a and HBP-1b, respectively. The structure of the hyperbranched polymer did not have a significant effect on the thermal properties and electrochemical stability of the composite solid polymer electrolytes. The tensile strength of the cross-linked composite solid polymer electrolyte using HBP-2 was lower than that of the cross-linked composite solid polymer electrolyte using HBP-1b, but higher than that of the non-cross-linked composite solid polymer electrolyte using HBP-1a. The HBP-2 with ether-linkage showed higher chemical stability against alkaline hydrolysis compared with HBP-1a with ester-linkage.     

Electrode potentials of electrochemical cells with oxide-conducting solid electrolyte in chemically nonequilibrium gas mixtures

A wide range of electrodes for solid oxide electrolyte cells in chemically nonequilibrium gas media simultaneously containing oxygen and combustible gases is systematically studied. The concentration dependences are investigated for the potential response of electrodes made of conducting oxides, noble metals (platinum, gold, silver), and also composite electrodes containing dispersed oxide semiconductor phases, apart from the main conducting material. Besides, dynamic characteristics of these electrodes are investigated. The studies are performed in the temperature range from 450 to 800°C. The content of combustible gases in the mixture was varied from 10 ppm to 2%. The research results are of interest for development of sensors for combustible gases and for studying kinetics and mechanisms of catalytic oxidation reactions.     

Impedance of solid electrolyte systems

The main regularities of studying electrode processes in the systems with solid electrolytes are described using the method of electrochemical impedance with the relationships of Ershler-Randles and Frumkin-Melik-Gaykazyan and analysis of results based on equivalent electric circuits.     

Detection and classification of gaseous sulfur compounds by solid electrolyte cyclic voltammetry of cermet sensor array

Electrochemical sensors composed of a ceramic-metallic (cermet) solid electrolyte are used for the detection of gaseous sulfur compounds SO₂, H₂S, and CS₂ in a study involving 11 toxic industrial chemical (TIC) compounds. The study examines a sensor array containing four cermet sensors varying in electrode-electrolyte composition, designed to offer selectivity for multiple compounds. The sensors are driven by cyclic voltammetry to produce a current-voltage profile for each analyte. Raw voltammograms are processed by background subtraction of clean air, and the four sensor signals are concatenated to form one vector of points. The high-resolution signal is compressed by wavelet transformation and a probabilistic neural network is used for classification. In this study, training data from one sensor array was used to formulate models which were validated with data from a second sensor array. Of the 11 gases studied, 3 that contained sulfur produced the strongest responses and were successfully analyzed when the remaining compounds were treated as interferents. Analytes were measured from 10 to 200% of their threshold-limited value (TLV) according to the 8-h time weighted average (TWA) exposure limits defined by the National Institute of Occupational Safety and Health (NIOSH). True positive classification rates of 93.3, 96.7, and 76.7% for SO₂, H₂S, and CS₂, respectively, were achieved for prediction of one sensor unit when a second sensor was used for modeling. True positive rates of 83.3, 90.0, and 90.0% for SO₂, H₂S, and CS₂, respectively, were achieved for the second sensor unit when the first sensor unit was used for modeling. Most of the misclassifications were for low concentration levels (such 10-25% TLV) in which case the compound was classified as clean air. Between the two sensors, the false positive rates were 2.2% or lower for the three sulfur compounds, 0.9% or lower for the interferents (eight remaining analytes), and 5.8% or lower for clean air. The cermet sensor arrays used in this analysis are rugged, low cost, reusable, and show promise for multiple compound detection at parts-per-million (ppm) levels.     

Solid electrolyte sensor as a detector for gas chromatographic determination of combustible contaminants in air

In this paper, it is demonstrated for the first time that a solid electrolyte sensor based on stabilized cubic zirconium dioxide can be used for the chromatographic detection of combustible gases in air with the use of air as a carrier gas. The current of oxygen ions that passes through the sensor serves as an analytical signal. It is possible to obtain either a positive or negative signal of a combustible gas, depending on the polarity of the potential applied to the sensor and physicochemical processes that occur at the surface of the electrodes. Using the flux of oxygen ions passing from external air into the flow of the carrier gas, combustible contaminants can be detected in the range 0.1–5 vol % by the heat of a catalytic oxidation reaction. With the reverse flux of oxygen ions, the same contaminants can be detected at a level of 0.01–0.1 vol % by means of competitive adsorption.     

On a thermodynamic limitation of the water-gas potentiometry using solid electrolyte cells

Possibilities of the water-gas potentiometry using oxide ion-conducting solid electrolytes may be restricted by side reactions in the gas being analyzed. Changes in electrode potentials caused by simultaneous interfering equilibria in the water gas were investigated over a temperature range 1200 to 400°C for different initial gas compositions. Formation reactions of carbon and methane proved to be the side reactions which can be responsible for potential changes. Limits for the use of the analytical method are shown by graphs with deviations from the ideal values.77th report on oxide ion-conducting solid electrolytes and their possibilities of application; 76. see cfi/Ber. DKG (in press)     

XPS for in situ observation of an Ag electrode on a solid electrolyte used as oxygen sensor

The Ag electrode surface of a solid electrolyte in its working state has been studied by X-ray photoelectron spectroscopy. The nature of the AgO system on the electrode is dependent on the temperature. There are three types of AgO systems at 400°C. Type 1 with an O is binding energy of 532.6 eV only appeared at 325°C. However, when the temperature was raised to 400°C, types II and III (with BEs 531.1 and 529.2 eV) appeared. These O is signals are discussed in detail.     

Fabrication of an ammonia gas sensor using inkjet-printed polyaniline nanoparticles

This work details the fabrication and performance of a sensor for ammonia gas analysis which has been constructed via the inkjet-printed deposition of polyaniline nanoparticle films. The conducting films were assembled on interdigitated electrode arrays and characterised with respect to their layer thickness and thermal properties. The sensor was further combined with heater foils for operation at a range of temperatures. When operated in a conductimetric mode, the sensor was shown to exhibit temperature-dependent analytical performance to ammonia detection. At room temperature, the sensor responded rapidly to ammonia (t₅₀ = 15 s). Sensor recovery time, response linearity and sensitivity were all significantly improved by operating the sensor at temperatures up to 80 °C. The sensor was found to have a stable logarithmic response to ammonia in the range of interest (1-100 ppm). The sensor was also insensitive to moisture in the range from 35 to 98% relative humidity. The response of the sensor to a range of common potential interferents was also studied.     

Cellulose derivatives as solid electrolyte matrixes

Cellulose derivatives like hydroxyethylcellulose (HEC) and carboxymethylcellulose (CMC) were submitted to the graftization reactions. The samples of HEC were grafted with monoisocyanate of poly(propylene oxide) (MPPO) and different diisocyanates of poly(ethylene oxide) (DPEO) and poly(propylene oxide) (DPPO) in the presence of LiClO₄. CMC was grafted with MPPO. These polyssacharides based samples were characterized by IR, NMR and thermal analysis (DSC and TGA). The samples of grafted polyssacharides derivatives showed glass transition temperatures (Tg) of −40°C for HEC/MPPO, −33°C for HEC/DPEO, −10°C for HEC/DPPO and 24�C for CMC/MPPO. The ionic conductivities of all samples were about 10⁻⁷‐10⁻⁶ S/cm at room temperature. The sample of CMC/MPPO presented conductivity value similar to HEC/DPPO but does not exhibit film‐forming characteristic indicating its use as solid polymer electrolytes only in the pellet form.     

Organic/inorganic nanocomposite polymer electrolyte

The organic/inorganic nanocomposites polymer electrolytes were designed and synthesized. The organic/inorganic nanocom-posites membrane materials and their lithium salt complexes have been found thermally stable below 200℃. The conductivity of the organic/inorganic nanocomposites polymer electrolytes prepared at room temperature was at magnitude range of 10-6 S/cm.     

模式识别用于压电晶体传感器阵列定量检测有机蒸汽混合物

本文应用9个压电晶体组成传感器阵列, 每片晶体上分别涂有不同种类的冠醚衍生物, 用它来定量检测二元及三元有机蒸汽混合物, 在数据处理中比较了两种模式识别方法---偏最小二乘法(PLS)和人工神经网络法(ANN), 实验证明, ANN法在预测准确度上明显优于PLS法, 本文还讨论了解决神经网络训练过拟合现象的方法。     

Discrimination of coatings on wooden materials using the gas sensor system

The applicability of sensor system for the discrimination of sources of indoor pollution was investigated. As examples of indoor pollution sources, paint and lacquer coatings were considered. Commercially available preparations: Akrylux, Doamlux, Bejca and White Scandinavian were selected for headspace measurements using TGS sensor array. Following issues were investigated: (1) discrimination between water- and solvent-based coatings, (2) discrimination between one component coatings, and (3) discrimination between one component and two component coatings. Following data analysis methods were used: principal component analysis (PCA), linear discriminant analysis (LDA) and probabilistic neural network (PNN). Results showed that coatings could be discriminated successfully, provided the surface covered was solid wood (0-1.8% error). The interference of fibreboard volatiles in sensor measurements of coatings was most likely encountered. It could have significantly impaired discrimination of coatings on fibreboard (2.8-5.6% error) as compared to wood. Worst results were obtained for the discrimination of coatings on unknown material(12.5-28.7% error).     

Oxygen solid electrolyte coulometry (OSEC)

The development and utilization of solid electrolyte-based coulometric techniques for the investigation of different oxygen exchange processes of solids or liquids, oxygen or hydrogen permeability through membranes, and generation of gas flows with well-defined oxygen concentration is briefly reviewed. The method based on Faraday’s law may be used alternatively or additionally to thermogravimetry, gas chromatography, chemical analysis, spectroscopy, and X-ray or neutron diffractometry in a wide oxygen partial pressure region (10^?20 to 10⁵?Pa) unaffected by temperature. The detection limit of exchanged oxygen is determined by a current- and voltage-measuring technique and is now not lower than 50?ng for devices operating in carrier gas mode.     

Simulation of nonstationary processes in solid electrolyte electrochemical cells for the pulsed mode of gas composition variations

Studying processes that occur in solid electrolyte electrochemical cells when the working electrode is subjected to an impact of the reactive gas medium are of interest for both their practical application and the understanding of mechanisms of these processes. There are grounds to assume that the methods of studying the processes on electrodes by subjecting the latter to chemical pulses provide more information as compared with the conventional methods based on electric perturbations. A computer simulation of nonstationary processes in a solid electrolyte electrochemical cell of the flow-through kind is carried out. The model of these processes takes into account the transport of electrochemically active components in the gas phase, the kinetics and statics of adsorption of these substances on the gas/electrode interface, and the kinetics of electrode reactions including chemical and charge-transfer stages. Time dependences of concentration fields are calculated as well as the integral characteristics of flows, namely, the oxygen flow from the gas phase to the electrode, the oxygen flow from the electrode to the solid electrolyte, and the flow of the electrochemically active component at the cell outlet.     

Lithium transport within the solid electrolyte interphase

A LiClO₄ SEI film grown on copper was examined with time-of-flight secondary ion mass spectrometry. The SEI porosity profile and Li⁺ transport processes within the SEI were studied with isotopically labeled ⁶LiBF₄ electrolyte. An ~ 5 nm porous region, into which electrolytes can easily diffuse, was observed at the electrolyte/SEI interface. Below the porous region, a densely packed layer of Li₂O and/or Li₂CO₃ prevents electrolyte diffusion, but Li⁺ transports through this region via ion exchange.     

Recent advances in nanostructured composite solid electrolyte

Solid-state lithium batteries (SSLBs) potentially offer safer and higher energy density batteries than traditional Li-ion batteries, but many challenges remain in the development of high-performance SSLBs. For example, solid-state electrolytes with high ionic conductivity are still critically needed. Composite solid electrolytes (CSEs), which are constituted of ceramic fillers dispersed in polymer matrices, may potentially combine the advantages of ceramic and polymer electrolytes and thus have been intensively investigated. Recent works have found that the size, geometry, and dispersion of ceramic ?llers strongly influence the conductivity of CSEs. This review aims at giving a summary of the recent progresses in CSE including the developments in materials as well as mechanistic characterizations. We believe the latest scientific insights will help the researchers in the field to better design CSEs toward the development of high-performance SSLBs.