RU1801204C - Electrochemical transducer of carbon dioxide - Google Patents

Abstract

Usage: instrumentation, namely electrochemical solid-state sensors for the composition of gaseous media. The sensor can be used in agriculture to control the atmospheric composition of greenhouses, greenhouses and vegetable stores to maintain an increased concentration of carbon dioxide (carbon dioxide), as well as in air conditioning control systems and in technological processes. SUMMARY OF THE INVENTION: In an electrochemical sensor consisting of a solid electrolyte with sodium conductivity, a reference electrode and a working electrode, NasLnSUOi2 compounds are used as a solid electrolyte, where Ln is an element from the lanthanide group, and sodium tungsten bronze of the composition Nao is used as a reference electrode. sWOa, and Sn02-SbOa solid solution as a working electrode. 3 ill. The essence of the invention lies in the fact that a complex silicate having the formula Na5LnSi40i2, where Ln is an element from the lanthanide group, is used as a solid sodium-conducting electrolyte in the sensor, moreover, a compound of the composition Nao.sWOa (sodium tungsten bronze) is used as a reference electrode, and a solid solution of tin and antimony oxides Sn02 Sb02 was taken as the working electrode. Thus, the carbon dioxide sensor

Description

kind, according to the invention, is a solid-state electrochemical system

Nao.sWOs Na5LnSi40i2. Sn02-Sb02.

Solid electrolytes of the type NasLnSi40i2 complex silicates are characterized by high conductivity with respect to sodium ions at room temperatures (0.001 S / cm at 25 ° C) and the ability to adsorb carbon dioxide particles, due to the presence of adsorption centers - Ln3 + lanthanide ions, where Ln La, Eu, Sm , Gd, Tb, Dy, Ho, Tb, etc.

Semiconductor solid solutions existing in the composition range from 0.5 to 30 mol% Sb02 also strongly adsorb CO2. Sodium Bronze Nao.sWOa in contact with a sodium conductive solid electrolyte, the potential of which is determined by the exchange of sodium ions and is independent of the composition of the gas phase. Therefore, bronze serves as a stable reference electrode.

Figure 1 shows the proposed sensor, a longitudinal section; Figs. 2 and 3 are diagrams illustrating its operation.

In a cylindrical mold 1 made, for example, of fluoroplastic, a powder layer of sodium tungsten bronze powder 2 of composition No. 0 is pressed sequentially with metal contact 3, solid electrolyte Na5LnSi40i2-4 and solid solution Sn02 Sb02-5 also with metal contact 6 in the form of a wire from stainless steel. When the concentration of carbon dioxide in the air changes, the electric potential difference E between the two electrodes changes (signal). This potential difference linearly depends on the logarithm of the concentration of carbon dioxide, but does not depend on the size of the sensor, the area of contact of the electrodes with the electrolyte or with the gas phase. The value of E is measured with a digital voltmeter, which can be calibrated in units of concentration.

The invention is illustrated by the following examples 1.

Example 1. A Nao.sWOa powder is pressed onto a NasGdSi40i2 solid electrolyte tablet with a pressure of 300 MPa on one side and Sbo, oiSno, 9902 powder on the other. The electrolyte is pressed into the fluoroplastic housing with down conductors from

of stainless steel. Response measurements were carried out in air-carbon dioxide mixtures at a relative humidity of 26% and a temperature of 23 ° C. The dependence of the measured potential difference E on the concentration of carbon dioxide C is expressed by the equation. E 116 + 46 IgC ± 5, mV.

The value of E in air is about 58 mV and depends on the content of carbon dioxide in it. The values of the measured E values calculated by the equation of carbon dioxide concentrations and given concentrations in the gas phase are given in Table 1.

Example 2. The sensor was manufactured as in Example 1, but the NasHoSi40i2 compound was taken as a solid electrolyte, relative humidity of the medium was 47%, and the temperature was 22 ° C. Calibration equation

E 89+ 56 IgC ± 7, mV

The value of E in air is 16 mV. The results of measurements and calculations of the signal are presented in table 2.

Thus, the proposed sensor allows to determine the concentration of carbon dioxide in mixtures with air in the range from 0.1 to 50 vol.% By measuring the potential difference on the electrodes. The steady-state response time is about 20 s, and the relaxation time is no more than 90 s. The relative error in determining the concentration is from 2 to 15%. The sensor maintains calibration for a long time (at least 3 months), and has mechanical and chemical stability in air. The operating temperature of the sensor is close to room temperature.

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Claims (1)

SUMMARY OF THE INVENTION An electrochemical carbon dioxide sensor comprising a sodium-conducting solid electrolyte placed in an insulating housing, a reference electrode and a working electrode, characterized in that, in order to lower the sensor’s operating temperatures, a compound NasLnSi40i2, where Ln is an element, is used as a sodium-conducting solid electrolyte from the group of lanthanides, wherein the reference electrode is made from the compound Mao, and the working electrode is made from solid solution. Table 1 Continuation of the table. 1 table 2 AQ I - L -1 F1: g. 3 Editor Compiled by E. Ukshe Tehred M. Morgenthal 01 4 C ("A TO Proofreader N. Gunko