Solvent Evaporation Rate as a Tool for Tuning the Performance of a Solid Polymer Electrolyte Gas Sensor

Solid polymer electrolytes show their potential to partially replace conventional electrolytes in electrochemical devices. The solvent evaporation rate represents one of many options for modifying the electrode-electrolyte interface by affecting the structural and electrical properties of polymer electrolytes used in batteries. This paper evaluates the effect of solvent evaporation during the preparation of solid polymer electrolytes on the overall performance of an amperometric gas sensor. A mixture of the polymer host, solvent and an ionic liquid was thermally treated under different evaporation rates to prepare four polymer electrolytes. A carbon nanotube-based working electrode deposited by spray-coating the polymer electrolyte layer allowed the preparation of the electrode-electrolyte interface with different morphologies, which were then investigated using scanning electron microscopy and Raman spectroscopy. All prepared sensors were exposed to nitrogen dioxide concentration of 0-10 ppm, and the current responses and their fluctuations were analyzed. Electrochemical impedance spectroscopy was used to describe the sensor with an equivalent electric circuit. Experimental results showed that a higher solvent evaporation rate leads to lower sensor sensitivity, affects associated parameters (such as the detection/quantification limit) and increases the limit of the maximum current flowing through the sensor, while the other properties (hysteresis, repeatability, response time, recovery time) change insignificantly

Effect of the Different Crystallinity of Ionic Liquid Based Solid Polymer Electrolyte on the Performance of Amperometric Gas Sensor

Solid polymer electrolytes (SPE) based on ionic liquid, poly-(vinylidene fluoride) and solvent N-methyl-pyrrolidone represent an effective component in electrochemical sensors. The advantage lies in their composition, which offers an opportunity to prepare SPE layers with a different porosity and microstructure. The study shows how the SPEs of different crystallinities affect the performance of an amperometric gas sensor from the point of view of current response (sensitivity), limit of detection and current fluctuations. The morphology of SPE has an impact not only on its conductivity but also on sensor sensitivity due to the morphology of the interface SPE/working electrode (WE)

Solvent Evaporation Rate as a Tool for Tuning the Performance of a Solid Polymer Electrolyte Gas Sensor

Solid polymer electrolytes show their potential to partially replace conventional electrolytes in electrochemical devices. The solvent evaporation rate represents one of many options for modifying the electrode-electrolyte interface by affecting the structural and electrical properties of polymer electrolytes used in batteries. This paper evaluates the effect of solvent evaporation during the preparation of solid polymer electrolytes on the overall performance of an amperometric gas sensor. A mixture of the polymer host, solvent and an ionic liquid was thermally treated under different evaporation rates to prepare four polymer electrolytes. A carbon nanotube-based working electrode deposited by spray-coating the polymer electrolyte layer allowed the preparation of the electrode-electrolyte interface with different morphologies, which were then investigated using scanning electron microscopy and Raman spectroscopy. All prepared sensors were exposed to nitrogen dioxide concentration of 0-10 ppm, and the current responses and their fluctuations were analyzed. Electrochemical impedance spectroscopy was used to describe the sensor with an equivalent electric circuit. Experimental results showed that a higher solvent evaporation rate leads to lower sensor sensitivity, affects associated parameters (such as the detection/quantification limit) and increases the limit of the maximum current flowing through the sensor, while the other properties (hysteresis, repeatability, response time, recovery time) change insignificantly

Electrochemical nitrogen dioxide sensor with solid polymer electrolyte based on ionic liquids

Tato disertační práce se zabývá perspektivními elektrochemickými senzory s polymerním elektrolytem založeným na organických materiálech pro detekci plynných látek. Úvodní část je věnována základním pojmům a vlastnostem senzorů pro detekci par a plynů. Následuje popis a zhodnocení současných principů detekce s ohledem na možnosti využití organických materiálů. Ve druhé části se práce podrobněji zaměřuje na perspektivní oblast elektrochemických senzorů. Pozornost je věnována základnímu rozdělení, elektrodovým topologiím, reakčním mechanismům a vyhodnocovacím obvodům. Teoretická část je zakončena charakterizací základních vlastností organických iontových kapalin nezbytných pro uplatnění v elektrochemických senzorových aplikacích. Experimentální část je věnována návrhu tříelektrodového ampérometrického senzoru s polymerním elektrolytem na bázi organické iontové kapaliny a popisu předpokládaných reakčních mechanismů. V této části jsou rovněž popsány technologické aspekty ovlivňující morfologii a strukturu jednotlivých senzorových vrstev. Hlavní část práce je zaměřena na studium vlivu geometrických parametrů pracovní elektrody na senzorovou odezvu. Výsledkem práce je návrh a realizace nového typu elektrochemického senzoru s polymerním elektrolytem pro detekci oxidu dusičitého.Katedra technologií a měřeníObhájenoThis thesis deals with the construction of electrochemical devices based on organic materials for the detection of gas phase substances. The introductory part is focused on the description of basic terms and sensor properties which are generally used in the field of gas sensors. Subsequently, basic detection principles are described with regard to the potential use of organic materials in particular types of sensors. The middle part is concentrated on my activities in the field of electrochemical sensors. The attention is paid to the description of basic sensor classification, electrode topologies, electronic evaluation circuits and reaction mechanisms. This part of the thesis also includes the description and characterization of properties of organic ionic liquids. The experimental part is dedicated to the design of three-electrode amperometric electrochemical sensor with a new type of polymeric electrolyte based on organic ionic liquid and to the description of reaction mechanisms occurring in the sensor. The main part is concentrated on the study of the influence of the geometry of a working electrode on the properties of the sensor response. Finally, the design and implementation of new type of the electrochemical sensor for nitrogen dioxide detection is presented

The effect of the orientation towards analyte flow on electrochemical sensor performance and current fluctuations

Analyte flow influences the performance of every gas sensor; thus, most of these sensors usually contain a diffusion barrier (layer, cover, inlet) that can prevent the negative impact of a sudden change of direction and/or the rate of analyte flow, as well as various unwanted impacts from the surrounding environment. However, several measurement techniques use the modulation of the flow rate to enhance sensor properties or to extract more information about the chemical processes that occur on a sensitive layer or a working electrode. The paper deals with the experimental study on how the analyte flow rate and the orientation of the electrochemical sensor towards the analyte flow direction influence sensor performance and current fluctuations. Experiments were carried out on a semi-planar, three-electrode topology that enabled a direct exposure of the working (sensing) electrode to the analyte without any artificial diffusion barrier. The sensor was tested within the flow rate range of 0.1–1 L/min and the orientation of the sensor towards the analyte flow direction was gradually set to the four angles 0°, 45°, 90° and 270° in the middle of the test chamber, while the sensor was also investigated in the standard position at the bottom of the chamber

Effect of various flow rate on current fluctuations of amperometric gas sensors

The flow rate of analyte is a key parameter in the measurement system that influences response of gas sensors. The paper focuses on possibility of improved gas detection by modulation of analyte flow rate around amperometric sensors at equilibrium conditions by studying the direct current level and its fluctuations at selected concentration. To independently explore an impact of concentration and flow rate on spectral density of current fluctuations, all measurements were provided out under the same temperature, and each sample sensor was put to the same position at the test chamber to be under same fluidic condition. The experiments were carried out on the fully-printed amperometric NO2 sensor based on a semi-planar three electrode topology. The aims of this experimental study are two-fold: firstly, to show that spectral density of current fluctuations significantly changes in the level and the shape as flow rate increases at constant concentration of detected gas; and secondly, to demonstrate that evaluation of these fluctuations and DC component can be used to compensate the negative effect of flow rate on sensor responses. The spectral density of current fluctuations develops as several mechanisms related to fluctuation phenomena become dominant with increasing flow rate. Thus, signal-to-noise ratio of current response on detected gas decreases as flow rate increases, while the ratio is almost invariant to gas concentration

Preparation of nitrogen dioxide sensor utilizing aerosol Jet Printing technology

An innovative aerosol jet printing (AJP) technology was used for the preparation of an electrochemical amperometric gas sensor for nitrogen dioxide detection. It was demonstrated that this non-contact, direct-write printing process allowed the optimization of the platinum electrode platform on a ceramic substrate and so a significant reduction in the overall sensor dimensions. The detection capability of such a sensor was successfully demonstrated within the range of 0−1000 ppb NO2. Sensor parameters such as sensitivity, response/recovery time, repeatability, hysteresis and limit of detection were determined and their dependence on sensor dimensions was discussed

Surface Analyses of PVDF/NMP/[EMIM][TFSI] Solid Polymer Electrolyte

Thermal treatment conditions of solid polymer polymer electrolyte (SPE) were studied with respect to their impact on the surface morphology, phase composition and chemical composition of an imidazolium ionic-liquid-based SPE, namely PVDF/NMP/[EMIM][TFSI] electrolyte. These investigations were done using scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry as well as X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy. A thoroughly mixed blend of polymer matrix, ionic liquid and solvent was deposited on a ceramic substrate and was kept at a certain temperature for a specific time in order to achieve varying crystallinity. The morphology of all the electrolytes consists of spherulites whose average diameter increases with solvent evaporation rate. Raman mapping shows that these spherulites have a semicrystalline structure and the area between them is an amorphous region. Analysis of FTIR spectra as well as Raman spectroscopy showed that the -phase becomes dominant over other phases, while DSC technique indicated decrease of crystallinity as the solvent evaporation rate increases. XPS and ToF-SIMS indicated that the chemical composition of the surface of the SPE samples with the highest solvent evaporation rate approaches the composition of the ionic liquid

Fully Printed Electrochemical NO2 Sensor

AbstractAn electrochemical amperometric nitrogen dioxide sensor with solid polymer electrolyte has been fabricated on flexible substrate by screen printing technology. The sensor concept is based on semi-planar, three electrode topology that enables to produce low power, high performance, thin and selective device that can be implemented on PET and/or Kapton foil. In addition, it has been demonstrated that the new platform of the electrochemical NO2 sensor can be manufactured without metallic electrodes which is very important from the point of view of environments. The sensor shows linear response in the range of 0-10ppm, fast response/recovery times (70/60 s, respectively) and sensitivity 590 nA/ppm. All sensor layers have been prepared by low cost mass production technology presented by screen printing technique. This approach has allowed to fabricate flexible, extremely low cost electrochemical NO2 sensors for environmental monitoring