Wyniki 1-4 spośród 4 dla zapytania: authorDesc:"Anna Strzelczyk"

Influence of the internal electrolyte composition on amperometric sulphur dioxide sensor properties


  Amperometric sensors due to theirs high sensitivity and good dynamic properties are frequently used in toxic gases concentrations monitoring. Most of them are based on liquid electrolytes. Up to now usage of solid polymer electrolyte (SPE) membrane with layer of porous, metal electrode in construction of such sensors is the most successful approach. Main advantages of this type of sensors are a very high active area of the working electrode (WE) and a short response time. To obtain WE in the form of a porous layer on conductive polymer membrane several kinds of methods, such as chemical deposition, metal vapour deposition, electrochemical deposition or painting can be used [1]. Some work concerning detection of sulphur dioxide with usage SPE electrode have been published so far [2-6]. In these studies different internal electrolytes, such as 1M HClO4 [2], 0.1M HClO 4 [3], 1M H2SO4 [4], 1M NaOH [4], 5M H2SO4 in water [5, 6] and 5M H2SO4 in mixture of water and different organic solutions [5, 6] have been used. Jacquinot at al published studies in which influence of concentration of H2SO4 on SPE sensitivity for SO2, NO and NO2 has been presented [7]. It has been proved that sensitivity of the SPE for SO2 decreases with increase of the internal electrolyte solution concentration. In this work performance of SO2 sensor is investigated. The main goal of this research is to determine the influence of internal electrolyte composition on the sensor properties. Sensor filled with 1M and 5M sulphuric acid has been prepared. Responses of the sensor in the atmosphere containing different concentration of SO2 or different interfering gases have been measured. Experimental Sensor structure is similar to one the described elsewhere [8]. In [8] metal layer on Nafion membrane was deposited by vacuum sublimation. Otherwise then in ear[...]

Electrocatalytic gas sensor with non-triangular excitation


  In recent years, solid state ion conducting materials have been intensively developed. These materials have a relatively high ionic conductivity based on a single predominantly conducting anion or cation species and have negligibly small electronic conductivity. Typically, useful solid electrolytes exhibit ionic conductivities from 10-1 to 10-5 S/cm at room temperature. Solid state electrolytes exhibit a potential for application in a variety of solid state electrochemical devices such as fuel cells, batteries, membranes, pumps and sensors [1]. Gas sensors are one of the most critical and rapidly growing areas in modern solid electrolyte technology. Solid state gas sensors are cost effective, small, rugged and reliable [2, 3]. Usually electrochemical solid state sensors operate in either potentiometric or amperometric mode [4, 5]. A lack of selectivity is sometimes a shortcoming of such sensors. It seems that improvements of selectivity can be obtained in case of the electrocatalytic sensors. Their working principle is based on acquisition of an electric current, while voltage ramp is applied to the sensor. The current-voltage response depends in a unique way on the type and concentration of ambient gas. In case of electrocatalytic gas sensors usually a linearly changing voltage excitation signal of symmetrical triangular shape in range from 5 to -5 V is applied to the sensors terminals [6]. The voltage sweep rate is adjusted to 50 mV/s. This, originated from liquid electrochemistry, method has some shortcomings. In typical conditions, one measuring cycle takes up to 7 min. Stable response is obtained most often after 2 or more cycles, thus extending measuring time even further. Long measuring time can limit application of electrocatalytic sensors in environments with fast gas concentration changes. In th[...]

Electrocatalytic sensor based on Nasicon with auxiliary layer


  In recent years electrochemical gas sensors based on solid state electrolytes have been intensively investigated. They are relatively easy to fabricate, simple in use and quite durable. Nasicon (Na Super Ionic Conductor) is one of the most promising materials, which have been used in construction of gas sensors. Sensors based on Nasicon are used for detecting of different gases including carbon oxides [1, 2], nitrogen oxides [3-6] and sulfur dioxide [7]. Most of these devices operate in potentiometric or amperometric mode. In case of some sensor constructions, besides electrolyte and metal electrodes, additional layers are applied. In some cases such phase is required to obtain sensitivity to specific gas or to shift operating temperature to more preferred one [7]. In other cases sensor properties such as selectivity or stability are improved. Auxiliary phase usually forms extra interface between measured gaseous compound and electrolyte or electrodes. For example, in case of amperometric sensors, it was noticed, that presence of auxiliary layer on surface of sensing electrode can increase the number of reaction sites thus improving sensor sensitivity [5]. Auxiliary layer may also be used to create a diffusion barrier. In case of the potentiometric or amperometric nitrogen oxides sensors based[...]

Investigation of electrocatalytic gas sensor properties in presence of chlorine


  Gas sensors based on solid state electrolytes have many advantages, such as durability, low cost and long-term stability. There is a number of types of solid state gas sensors. The main disadvantage of such sensors is usually lack of selectivity. Electrochemical sensors operating in electrocatalytic mode seem to have improved selectivity due to its particular working mechanism [1]. Operation principle of such sensors is based on the excitation of a galvanic cell with a periodic triangular voltage, while current response is measured. During voltage sweep an oxidation and a reduction of chemical species occurs on electrodes surface. As a result sensor response in a form of an unique voltammetric characteristic is obtained. Shape of that current-voltage (I-V) curve depends on type and composition of gases in the sensor surrounding [2]. Earlier studies indicated that electrocatalytic gas sensors based on Nasicon can be used for NO2 [1, 3, 4], SO2 [1], NH3 [4, 5] and H2S [6] detection. Optimal working temperature was determined for NO2 (175ºC), NH3 (350 C) and H2S (300 C). In this study investigation of electrocatalytic sensors properties in the presence of chlorine are presented. Experimental Nasicon pellets were prepared using the sol-gel method according to procedure [7]. Process of obtaining[...]

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