A device for electrochemical measurement of gas permeability

Abstract

A device for electrochemical measurement gas permeability includes a vessel (1), a working electrode (2) and a pressure chamber (3), where the vessel (1) contains an electrolyte (11), an auxiliary electrode (13) and a bubbler (14) with an inert gas. The working electrode (2) is provided with a catalyst support (21) in the form of a grid on which there is the catalyst layer. The working electrode (2) is further provided with a measured sample, which is located under the catalyst support (21). The pressure chamber (3) is provided with a gas inlet tube (31), where the working electrode (2) is located between the vessel (1) and the pressure chamber (3). The vessel (1), the working electrode (2) and the pressure chamber adhere gas-tight to each other.

Description

[0001] A device for electrochemical measurement of gas permeability

[0002] Field of the Invention

[0003] The present invention relates to the field of devices for the analysis of the physical properties of materials, specifically for the determination of the permeability of various materials, including porous materials, by allowing gases to diffuse through the material and then performing a catalytic redox reaction and measuring electrochemical currents through an electrode to accurately calculate the diffusion rate and permeability of materials.

[0004] Background of the Invention

[0005] The permeability, i.e. the permeability of gases through solids, is one of the key variables monitored in materials produced and used in many industrial areas. For example, in the food and pharmaceutical industries, the oxygen permeability of packaging materials directly influences the shelf life of products; in the construction industry, it is an important property of insulation materials, and in the field of electromobility, the optimal level of permeability of materials used in the production of fuel cells directly influences their efficiency and durability. Therefore, for the development of new materials or efficient final inspection in production, a simple analytical device is required that provides reliable results in the shortest possible time.

[0006] Having regard to the state of the art, devices for measuring gas permeability based on purely physical or physical-chemical principles are known. J. K. Jung et al., Polymer Testing 2021, 93, p. 107016, describes a device in which a column of liquid is forced by gas passing under pressure through a sample of material to be measured, with the movement of the column being monitored by a camera. The disadvantage of this device is the limited accuracy and sensitivity of the measurement due to both the optical reading on the scale of liquid column and the deviation caused by solubility of the gas used in the selected liquid, which is also heavily dependent on the ambient conditions. I. Mamaliga et al., Chemical Engineering and Processing 2004, 43(6), p. 753-763, describes a device that uses a system of electromagnets generating a magnetic field in which the sample is suspended and precision balances that measure the change in mass of the sample due to gas absorption to measure permeability. Such a system is very complicated in design, requires sensitive measuring instruments dependent on frequent calibration, the measurement results are heavily influenced by ambient conditions, and does not allow measurement of gas flow through the sample. S. Tan et al., Journal of Materials Chemistry A 2015, 3, p. 14876-14886 describes a cell with two chambers separated by baffle formed by the sample to be measured, with the inlet chamber receiving gas under known pressure and with known flow rate, and with the outlet chamber where the flow rate of the gas that has passed through the baffle is measured. This value is then used for calculating permeability of the baffle. The disadvantage of this device is the high tightness of the cell necessary to prevent gas leakage around the baffle and distortion of the measurements, which is very difficult to achieve in practice and the measurements are therefore unreliable. Another problem is the sensitivity of the flow measurement, limiting the application of this technique to samples with relatively high permeability. A similar solution is known from R. Blunk et al., Journal of Power Sources 2006, 159, p. 533-542, where the amount of gas that has passed through the baffle is analysed by gas chromatography. Despite good sensitivity of chromatography to gases, this arrangement adds undesirable complexity of the chromatography device to the aforementioned shortcomings.

[0007] Furthermore, with regard to the state of the art, methods for measuring permeation based on electrochemical measurements are known, which provide high measurement reliability and do not require the use of complex measuring instruments, since a potentiostat / galvanostat is sufficient for the measurement. However, as it can be seen from the example of document A. Manhard et al., Journal of Nuclear Medicine 2015, 463, p. 1057-1061, the solutions still reach excessive complexity in the form of the need for specialised electrochemical cells. The solution described in the cited document uses a complex double electrochemical cell where the material sample to be measured is fully immersed in the electrolyte and is not in direct contact with the gas, as a result of which this arrangement does not simulate the working conditions of industrial application of the sample to be measured, and therefore the values obtained are not sufficiently meaningful. In addition, the exchange of samples requires a complete dismantling of the cell, which does not allow rapid serial measurement of multiple samples. A simpler design based on electrochemical measurement is known from document T. Akamatsu et al., Journal of Alloys and Compounds 2005, 393, p. 302-306, where the sample to be measured is placed in a vessel and functionally forms a baffle between the part of the vessel containing the electrolyte and working electrode and the part placed under it, which receives the gas. However, the described solution is only suitable for hydrogen permeation measurements and cannot be used for the analysis of thin or structurally weak layers of material due to the integral function of the sample exposed to the hydrostatic pressure of the electrolyte. Furthermore, the main limitation of this technique is the requirement for catalytic activity of the sample in relation to the permeable gas.

[0008] The object of the present invention is to present a device for measuring the permeability of gases based on electrochemical analysis, which overcomes the shortcomings of the background of the invention by being simple in design, by enabling rapid exchange of samples and thus rapid serial measurement of a large number of samples, and by being versatile in terms of the nature of the material to be measured (for example, it is possible to analyse both electrically conductive and non-conductive materials) and the gas selected.

[0009] Summary of the Invention

[0010] The essence of the invention is a device comprising three main parts, namely a vessel, a working electrode and a pressure chamber. The vessel is filled with electrolyte in which an auxiliary electrode and optionally also a reference electrode are immersed. The reference electrode is required for predictable setting of the working potential of the redox reaction of the gas under study, but an assembly without reference electrode can be used for high-temperature ones. Preferably, a bubbler is connected to the vessel, which supplies inert gas for degassing of the electrolyte. The working electrode includes a support with a catalyst, which increasses rate of electrochemical reaction of the gas passing through the sample into the catalytic layer. The supported catalyst is placed on the sample so that it covers the entire surface of the sample, with the result that all the gas passes only through the sample and reaches the catalytic layer where the electrochemical reaction takes place. The pressure chamber is equipped with inlet and outlet tubes for the inlet and outlet of pressurized gas, with the outlet tube being equipped with a valve and a pressure gauge. The working electrode with the sample is located between the vessel and the pressure chamber, with the three parts adhering gas-tight to each other. The electrolyte can be solutions and melts of acidic, basic, saline, buffered, and ionic liquids with any pH value, thus enabling permeability analysis in environments with a wide range of chemical properties. Depending on the specific environment used, the appropriate catalyst type, reference and auxiliary electrodes can be chosen freely.

[0011] The catalysts typically based on Pt, Pd, Ag, Cu, Co, Fe, Ni, including alloys, can be used as catalysts for electrochemical reactions, with the choice of catalyst depending on the type of gas to be detected. For example, Pt- or Pd-based catalysts are typically used for the detection of O2 and H2, Ag- or Cu-based catalysts are typically used for the detection of CO2, CO typically reacts with Fe- or Co-based catalysts, and Ni- or Pd-based catalysts can be used for CH4.

[0012] The device can be used to measure the permeability of conductive and non-conductive materials, for example polymers or rubbers, metals or metal alloys, ceramic or glass materials and combinations thereof in the form of composite materials.

[0013] Explanation of drawings

[0014] Figure 1 shows a layout diagram of the device according to the invention.

[0015] Example of the invention embodiments

[0016] Example 1

[0017] The device consists of three main parts, namely the vessel 1, the working electrode 2 and the pressure chamber 3. The vessel 1 contains the electrolyte 11, the argent chloride reference electrode 12, the platinum auxiliary electrode 13 and the bubbler 14 with argon. The electrolyte 11 is aqueous sulphuric acid with a concentration of 0.5 mol / L. The working electrode 2 is provided with the catalyst support 21 in the form of a titanium grid, on which is the catalyst in the form of 40% platinum deposited on activated carbon with a total surface area of 140 m2 / g and a platinum surface area of 70 m2 / g at a crystallite size according to X-ray diffraction analysis of 3-4 nm. The working electrode 2 is further provided with a measured sample, which is located under the catalyst support 21. The pressure chamber 3 is provided with the inlet tube 31 and the outlet tube 32 for the inlet and outlet of pressurized gas, which is hydrogen. The outlet tube 32 is equipped with the valve 33 and the digital pressure gauge 34. The working electrode 2 is located between the vessel 1 and the pressure chamber 3, with the three parts adhering gas-tight to each other.

[0018] Example 2

[0019] The device consists of three main parts, namely the vessel 1, the working electrode 2 and the pressure chamber 3. The vessel 1 contains the electrolyte 11, the Hg / HgO reference electrode 12, the carbon auxiliary electrode 13 and the bubbler 14 with argon. The electrolyte 11 is potassium hydroxide with a concentration of 1 mol / L. The working electrode 2 is provided with the catalyst support 21 in the form of a carbon grid, on which is the catalyst in the form of palladium black with a high surface area and a palladium surface area of 40 m2 / g at a crystallite size according to X-ray diffraction analysis of 6-10 nm. The working electrode 2 is further provided with a measured sample, which is located under the catalyst support 21. The pressure chamber 3 is provided with the inlet tube 31 and the outlet tube 32 for the inlet and outlet of pressurized gas, which is oxygen. The outlet tube 32 is equipped with the valve 33 and the digital pressure gauge 34. The working electrode 2 is located between the vessel 1 and the pressure chamber 3, with the three parts adhering gas-tight to each other.

[0020] Industrial applicability

[0021] The device for electrochemical measurement of gas permeability is industrially applicable in the analysis of packaging materials, fuel cell components or membranes for gas separation, materials for gas cylinders and similar gas-tight applications.

Claims

CLAIMS1. A device for electrochemical measurement of gas permeability characterized in that it comprises a vessel (1), a working electrode (2) and a pressure chamber (3), where the vessel (1) contains an electrolyte (11), an auxiliary electrode (13) and a bubbler (14) with an inert gas, furthermore the working electrode (2) is provided with a catalyst support (21) in the form of a grid on which is the catalyst; the working electrode (2) is further provided with a measured sample located under the catalyst support (21); furthermore, the pressure chamber (3) is provided with a gas inlet tube (31), where the working electrode (2) is located between the vessel (1) and the pressure chamber (3), where the vessel (1), the working electrode (2) and the pressure chamber adhere gas-tight to each other.

2. The device according to claim 1, characterized in that the vessel (1) further comprises a reference electrode (12).

3. The device according to claim 1 or 2, characterized in that the pressure chamber (3) is further provided with a gas outlet tube (32), where the outlet tube (32) is equipped with a valve (33) and a pressure gauge (34).

Images