CS201284B1 - Electrochemical power sources - Google Patents

Abstract

The invention relates to electrochemical sources of electric current consisting of a positive oxygen electrode and a negative electrode, which may be a hydrogen or metal electrode, immersed in an alkaline electrolyte. According to the invention, the oxygen electrode is formed by a catalytically active polymer mass formed by the thermal reduction of thermally dissociable oxygen compounds of silver on polyphenylene oxide chains. The source achieves a high specific power of 102 to 103 kW per 1 m2 of the electrode area and can operate in a wide thermal range.

Description

The invention relates to electrochemical sources of electric current in which electric current is generated by the oxidation of metal or hydrogen by oxygen, occurring at electrodes.

These sources of electric current are known and widely used. Their use on a larger scale is hindered mainly by the fact that the main drawback of these sources has not yet been satisfactorily resolved - primarily the low current density and low stability, which can burden known oxygen electrodes, in which a high polarization voltage is very quickly generated, which reduces the efficiency of the electrochemical source.

It has now been found that electrochemical sources of electric current with a higher specific power than the previous ones will be created if a gas diffusion electrode is used as the oxygen electrode, the preparation of which is described in Czechoslovak author's certificates No. 175580 and 175936.

The subject of the invention are electrochemical sources of electric current, formed by a positive oxygen electrode and a negative electrode, which can be a hydrogen electrode or a metal electrode such as zinc, cadmium, iron, sodium, both electrodes immersed in an alkaline electrolyte, the essence of the invention being that the oxygen electrode is formed by a catalytically active polymeric organometallic material formed by the thermal reduction of thermally dissociable oxygen compounds of silver on polyphenylene oxide chains.

The greatest advantage of electrochemical electric current sources is high specific power. 2 3 2 they can achieve power of 10 to 10 kW per 1 m of electrode area during long-term continuous operation. These current sources can operate in a very wide temperature range, in freezing temperatures and at temperatures over 200 °C, when, however, partial degradation of the organometallic polymer material forming the oxygen electrode occurs. The power is limited by the ability to remove heat from the operating current source.

The electrochemical source of electric current according to the invention is a cell, one electrode of which is a hydrogen gas diffusion electrode, realized for example by washing hydrogen through a porous nickel-based material, or a metal electrode, formed by metals and their alloys. As a material for metal electrodes, metals with a negative electrical potential relative to the oxygen electrode are particularly suitable, for example zinc, cadmium, iron, sodium.

The second electrode consists of a catalytically active organometallic polymer mass, formed by the reaction of thermally dissociable oxygen compounds of silver with polyphenylene oxide. The preparation of these electrodes and their properties are described in Czechoslovak patent certificates No. 175580 and 175936.

The electrolyte consists of alkaline solutions, especially concentrated solutions of potassium and sodium hydroxide. The arrangement of electrochemical sources according to the invention is carried out by known methods.

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Pure oxygen or its mixtures with other gases, such as air, can be used to saturate the oxygen electrode with oxygen. The current source is only slightly sensitive to impurities that can reduce the catalytic efficiency of the positive electrode. The optimal working pressure depends on the method of preparation of the electrode mass and the design of the cell; as a rule, it does not have to be higher than 5.10^ Fa.

The invention will be further illustrated by the following examples.

Example 1

An oxygen gas diffusion electrode made by the method described in the Czechoslovak patent 175580 was inserted into the 7N KOH electrolyte. The working pressure of oxygen on the electrode was 3.10^ Pa. A three-layer hydrogen gas diffusion electrode made of a mixture of Raney nickel powder, ammonium sulfite and carbonyl nickel was used as a counter electrode. The electrode operated at a hydrogen pressure of 1.10^ Pa. The system of electrodes forming the electrochemical cell of the electric current operated at a temperature of 338 K. The electric potential of the electrodes, the voltage U and the power P of the cell are given in Table 1. The electrode potentials were measured against the Hg/HgO electrode, which was used as a reference.

The electric current density and specific power are given relative to the geometric area of the oxygen electrode, which was P=6 cm ² . (The geometric area of the hydrogen electrode was 10 cm ² .) The drop in the terminal voltage of the cell is mainly influenced by the change in the electrode potential of the hydrogen electrode, as can be seen from the table.

Example 2 *

An oxygen gas diffusion electrode manufactured in the manner described in the Czechoslovak Patent No. 175580 was inserted into the 7N KOH electrolyte, similarly to example 1. The working oxygen pressure of the electrode was 3.1Ο ⁵ Pa. The geometric area of the oxygen electrode was 6 cm ² . A zinc electrode made of electrolytically pure zinc sheet was used as the counter electrode. This system of electrodes forming an electrochemical cell of electric current operated at a temperature of 338 K. In order for the change in the terminal voltage to be given mainly by the change in the electric potential of the oxygen electrode, the zinc electrode was larger than 78 cm ² . For this reason, the zinc electrode was loaded with a current density of maximum 30 mA/cm ² . The electrolyte was also replaced after a certain period of time. The oxygen electrode was loaded with a maximum electric current density of approximately 400 mA/cm ² . The electrolytic potentials of the electrodes were measured against a nickel electrode, which was used as a reference. The measured values are listed in Table 2.

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Example 3

An electrochemical system of oxygen-zinc electrodes was set up similarly to that shown in Example 2. However, the working temperature of the 7N KOH electrolyte was chosen to be 298 K. The electrical potentials of the electrodes were also measured against a nickel plate as a reference electrode. The measured values are given in Table 3.

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Table 1. Electric potential of electrodes, terminal voltage U and power P of electrochemical cell of electric current hydrogen-oxygen, T 338 K.

electric potential of electrodes (ί- ^Λ ) versus cell voltage (U) current power of the Hg/HgO electrode mV mV

Oxygen hydrogen calculated from electrode potentials measured total I mA specific A/m ² total P mW specific P W/m ² + 120 - 1113 1233 1240 0 0 0 0 + 90 - 1088 1178 1165 120 200 139.80 233 + 65 - 1048 1113 1080 300 500 324.00 540 + 45 - 938 983 940 600 1000 564.00 940 - - 873 - - 720 1200 - - - - - 830 900 1500 747.00 1245

Table 2. Electric potential ψ , voltage U and power P of the electrochemical cell of the oxygen-zinc electric current, T = 338 K.

electric potential voltage of the Slat (U) current power of the Slat electrodes (<? ) against the Ni electrode mV raV

oxygen zinc calculated from electrode potentials measured total I mA specific A/m ² total P^ mW specific P W/m ² - 330 - 1870 1540 1530 0 0 0 0 - 530 - 1830 1300 1320 240 400 316.80 528 - 590 - 1820 1230 1230 360 600 442.80 738 - 630 - 1810 1180 1170 480 800 561.60 936 - 670 - 1790 1120 1170 600 1000 702.00 1170 - 710 - 1780 1070 1070 720 1200 770.40 1284 - 780 - 1780 1000 1020 840 1400 856.80 1428 - 790 - 1780 990 1000 960 1600 960.00 1600 - 820 - 1770 950 950 1080 1800 1026.00 1710 - 870 - 1770 900 910 1200 2000 1092.00 1820

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- 1000 - 1760 760 790 1500 2500 1185.00 1975 - 1050 - 1740 690 690 1800 3000 1242.00 2070 - 1300 - 1730 430 450 2502 4170 1125.90 1876

Table 3. Electric potential of electrodes^ , voltage U and power P of electrochemical cell of electric current oxygen-zinc, T = 298 K.

electric potential cell voltage (U) current article performance electrode ( j) electrode Ni against mV mV oxygen zinc calculated measured total specific total measure from potentials and P P electrode mA A/nP mW W/nT - 410 - 1870 1460 1440 0 0 0 0 - 740 - 1840 1100 1100 240 400 264.00 440 - 860 - 1820 960 980 360 600 352.80 588 - 985 - 1820 835 86 0 480 800 412.80 688 - 1030 - 1800 770 750 600 1000 450.00 750 - 1140 - 1800 660 650 720 1200 468.00 780 - 1220 - 1790 570 570 840 1400 478.80 798 - 1310 - 1780 470 460 960 1600 441.60 736 - 1400 - 1780 380 321 1080 1800 346.68 578 - 1450 - 1775 325 310 1200 2000 372.00 620

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Claims (1)

Electrochemical power sources consisting of a positive oxygen electrode and a negative electrode, which may be a hydrogen or metal electrode such as zinc, cadmium, iron, sodium with both electrodes immersed in an alkaline electrolyte, characterized in that the oxygen electrode is a catalytically active polymeric organometallic mass thermally dissolvable oxygen-containing silver compounds on the polyphenylene oxide chains.