WO2011161375A1 - Electrolysis or reverse electrolysis device comprising an electrolyte consisting of an alkali and an alkaline silicate - Google Patents

Abstract

The invention relates to power conversion and particularly to an electrolysis or reverse electrolysis device comprising an additive in the aqueous electrolyte of the electrochemical cells thereof. The invention relates to an electrolysis or reverse electrolysis device comprising a first electrode (6, 106), a second electrode (7, 107), and an inter-electrode space (11, 111) that includes a functional medium arranged between the first electrode (6, 106) and the second electrode (7, 107), wherein the first electrode (6, 106) is produced from at least one electrically conductive means capable of being at the same electric potential at all locations so as to constitute said first electrode (6, 106). According to the invention, the functional medium is an aqueous electrolyte consisting of water, an alkali, and an alkaline silicate at a concentration of no less than 5 wt % of the aqueous electrolyte so as to obtain a protective effect for the first electrode (6, 106) and second electrode (7, 107) by creating an inorganic conductive passivation layer that mixes the compositional elements of said first (6, 106) and second (7, 107) electrodes and the compositional elements of the alkaline silicate together.

Description

 Electrolysis or reverse electrolysis device comprising an electrolyte composed of an alkaline base and an alkaline silicate

The invention relates to the conversion of energy and more specifically relates to an electrolysis or reverse electrolysis device comprising an additive in the aqueous electrolyte of the electrochemical cells of the latter.

There are known electrolysis or reverse electrolysis devices comprising a first electrode, a second electrode and an inter-electrode space comprising a functional medium such as an electrolyte or a dielectric. The effectiveness of such devices depends in particular on the two parameters that are the efficiency and the cost of the system. Their optimization is most often based on an empirical approach consisting of varying the different parameters defining the system.

The literature (engineering techniques, Encyclopedia of Electrochemistry, Ed. Wiley 2007, Handbook of Electrochemistry, 1 ^st Ed., Cynthia G. Zoski Ed. Elsevier 2007) teaches various optimization strategies and performance of electrolysers reverse electrolysers and all the associated costs. In particular, it is indicated that the parameters of interest are mainly the inter-electrode space, the catalyst and the electrolyte for the aspects related to the increase of the yield, on the one hand, the increase of the surface of electrode and density of electrode surface area for aspects related to investment costs (increase in electrical intensity and therefore the production rate for a given volume), on the other hand. Several solutions have been devised to improve the efficiency of the electrolysis or reverse electrolysis devices.

It is for example known from the state of the art the file "electrolysers of acid membrane water" publications Engineering Techniques (Treaty J4810) which teaches that acid electrolysis has developed using as electrolyte materials solid ion exchangers of the type of perfluorosulfonated membranes from DuPont, known under the trade name Nafion®. Electrochemical cells designed according to this method have interesting yields but the prohibitive cost of these devices, due to the use of ruthenium oxide catalysts, on the one hand, and acid corrosion resistant materials, on the other hand. on the other hand, strike the industrial development of this way, confined today to small capacity equipment. It is also known from WO-A-2008/061975 the possibility of using weak acids in combination with ion exchange membranes of the Nafion® type.

On the other hand, it is known from the file "Hydrogen by Electrolysis of Water" of the publications Techniques de l'Ingénieur (Treaty J6366) that the basic electrolysis is generally carried out from an aqueous solution of potassium hydroxide whose concentration varies according to the operating temperature, is 25% by weight for a temperature of 80 to 90 ° C, 30 to 35% at a temperature of 120 ° C and 40% at a temperature of 160 ° C, these concentrations corresponding to the maximum electrical conductivity of the solution at the temperature considered.

Similarly, the prior art documents US-B-1, 446,736, US-B-1, 547,362, US-B-2,433,871 and US-B-4,247,610 also disclose the realization of conversion systems of the present invention. energy using aqueous alkaline electrolytes, sometimes with additives, to improve their conductivity and therefore, ultimately, their energy efficiency.

Solutions for improving the conductivity of electrolytes nevertheless have the disadvantage of significantly damaging the conductive elements of the electrochemical cell, that is to say the electrodes, which has the immediate effect of limiting the lifetime and efficiency after a certain period of use of these systems.

These phenomena of electrode consumption have guided research on the choice of electrode materials intrinsically resistant to chemical reactions during electrolysis. Indeed, in the context of the operation of electrolysis devices or reverse electrolysis, it is not a matter of consuming the electrodes as in the technical field of generators and accumulators (described below) but on the contrary to be able to guarantee long-lasting operation.

In this respect, electrolysis or reverse electrolysis devices have been developed comprising electrodes made from noble materials (for example pure nickel, platinum, alloys of these elements or plated with these elements), the Oxidoreduction potential ensures the preservation of the electrodes.

Furthermore, EP-A-0 248 433 discloses the use of 0.6% sodium silicate solutions in aqueous solutions of sodium hydroxide to stabilize the production of hydrogen peroxide. US-A-3,932,208 discloses the deposition of soluble silicates in thin layer on the surface of asbestos diaphragms, anode compartment side, as a protective layer. Document US Pat. No. 6,572,756 teaches carrying out an electrochemical reaction for thin-layer deposition of a silicate-based mineral on metal parts allowing the passivation of the part and a better resistance to corrosion. In this case, the electrolyte used is composed of an alkali silicate (preferably sodium) and water as a solvent. The result is to obtain a chemical passivation layer but also a galvanic protection due to the increase in the electrical resistance of the electrode, the mineral layer being very little conductor.

In a similar field, it is known from document KR-A-2004/0094105 an anodizing process for treating magnesium alloy parts to protect them against corrosion. According to this anodizing method, the magnesium alloy part is disposed inside an electrochemical cell and plays the role of an anode. Thus, when a voltage and a current are applied across the electrochemical cell, the deposition of a protective thin layer (anticorrosion) on the anode is observed, this layer being homogeneous, regular and insulating, which allows use the magnesium alloy part for applications where corrosion resistance is required.

US-A-2005/0180094 teaches the addition of silicates as long-term performance stabilizers of capacitors. In this document, two possibilities for using silicates are provided: in the context of a silicate and water mixture, on the one hand, in the context of a mixture of water, silicate, organic solvent and ionogenic solution, of somewhere else.

US Pat. No. 7,691,527 teaches the possibility of adding sodium silicate as a gelling agent to electrolytes comprising metal hydrides for the production of hydrogen.

These latter documents thus teach the use of silicates for their protective properties of electrochemical cell conductive materials in the context of different electrolytic mixtures. The energy conversion systems described above nevertheless have the disadvantage of using electrolytes whose conductivity is not optimum and therefore insufficient for industrial applications and in different uses of electrolysis and reverse electrolysis. In a different technical field from that of the invention, it is known from the state of the art, the documents US-A1-2004/009392, CN-A-1 416 187, US-A-4 147 839, US 2,941,909 which describe energy conversion systems which do not relate to electrolysis or reverse electrolysis devices and whose operating principle is based on the consumption of a sacrificial electrode until it is totally consumed or unusable.

Thus, the document US-A1-2004/009392 describes a hydrogen generator whose operation is based, on the one hand, on the creation of a redox couple between one of the electrodes and the water for the generation hydrogen, allowing the release of hydrogen in parallel with the consumption of the sacrificial electrode and, on the other hand, the release of hydrogen contained in a metal hydride due to the passage of a current in the device, when connected to an external circuit. This document therefore relates to the realization of a means for storing and releasing hydrogen gas different from an electrolyser. In addition, this hydrogen generator aims to voluntarily consume one of the electrodes, called the sacrificial electrode, during the hydrogen release reaction.

Similarly, CN-A-1416187 discloses a lithium battery having a rechargeable electric energy accumulator to be connected to an electrical circuit for migrating the lithium ions from the anode to the cathode and vice versa (cycles loads - discharges). When it is charging, the battery releases lithium ions from the cathode which will attach to the anode, usually graphite. Each set of 6 carbon atoms of the anode can accommodate a lithium ion. During the discharge, the lithium ions go the opposite way and will again attach to the cathode.

Document US Pat. No. 4,147,839 relates to an electrochemical battery capable of generating a current when it is connected to the terminals of an electric circuit and comprising an electrode in the form of a metal powder stirred in an electrolyte, the powder possibly consisting of example of zinc or aluminum. In operation, the battery consumes the electrode in powder form and it is also expected that the system composed of the electrolyte-metal powder mixture is replaced after use in order to continue to operate. It is therefore also a system for storing energy using a sacrificial electrode.

Document US-A-2 941 909 also discloses a current generator which, as before, operates when it is connected to the terminals of an electric circuit and comprises an anode electrode, made of titanium alloys, which is consumed , during the operation of the current generator. In this document, it is intended to use silicate to ensure the stabilization of the output current voltage torque over the lifetime of the battery, until the depletion of the active products due to their consumption. Here again, the redox torque is chosen to allow the consumption of a sacrificial electrode.

The various electrolytes described in these documents are therefore not used in the context of electrolysis devices or reverse electrolysis but are, on the contrary, used in energy conversion systems which involve, by their nature, the total consumption of electricity. a sacrificial electrode. These embodiments are therefore contrary to the desired effects in the context of electrolysis devices or reverse electrolysis for which it is necessary to ensure an optimal life of the electrochemical cell, that is to say the longest possible without consume the electrodes. The problem underlying the invention is to have electrolysis or reverse electrolysis devices comprising a first electrode, a second electrode and an inter-electrode space comprising a functional medium arranged between the first electrode and the second electrode which on the one hand, is optimized to provide high efficiency at a reasonable manufacturing and operating cost on an industrial scale and, on the other hand, enables long-term commercial operation. The object of the invention is, more precisely, to use an electrolytic mixture which makes it possible to optimize the costs of producing the electrolysis or reverse electrolysis devices by eliminating the need to use catalysts or exchange membranes. ions, while guaranteeing a high yield and a long service life to the electrochemical cell. More particularly, the invention aims to significantly increase the conductivity of the electrolyte while ensuring adequate protection of the conductive elements of the electrochemical cell to prevent their structural and functional degradation, see their final destruction during the reaction. electrolytic. The invention aims to provide at least one solution to one of these problems.

On the other hand, according to a more particular problem, it has been demonstrated that an electrolysis or reverse electrolysis device comprising: on the one hand, an elongated electrically conductive means of length L and having a radius of curvature R less than 50 x 10 ^"6 m (50 micrometers) such that the ratio L / R is greater than 3 x 10 ⁶ (three million), secondly, a second electrode and, thirdly, a space electrodes with a thickness of between 1 x 10 ^"9 m and 2 x 10 ^{" 2} m (1 nanometer and 2 cm) makes it possible to significantly increase the field of view at the nanometer to millimeter scale. around the first electrode thus formed or to create complex electrostatic effects.

This effect is here called "corona effect", by analogy with the conventional corona effect known in the case of electrical cables whose diameter is of the order of a few centimeters, under high electrical voltage, of the order of several tens of kilo volts. However, the electrodes thus formed and subjected to this corona effect are rapidly deteriorated to be finally converted into nanometric powders with micrometric metal. It turns out that in the aforementioned embodiments, this corona effect - electrostatic effect due to the increased electric field - is thus greater than the inertia of the material component of the electrodes vis-à-vis the electrolysis.

The invention therefore also aims to provide an electrolysis or reverse electrolysis device having electrodes made so as to make possible the use of this corona effect, without leading to the destruction of the electrodes by their transformation into nanoscale powder. to micrometric.

To do this, the invention relates in a first aspect to an electrolysis or reverse electrolysis device comprising a first electrode, a second electrode and an inter-electrode space comprising a functional medium arranged between the first electrode and the second electrode; wherein the first electrode is made from at least one electrically conductive means adapted to be at all locations at the same electrical potential so as to constitute this first electrode; wherein the functional medium is an aqueous electrolyte composed of water, an alkaline base, and alkali silicate in a concentration of greater than or equal to 5% by mass of the aqueous electrolyte.

This embodiment and, in particular, the combination of alkaline bases and alkali silicates in a concentration greater than or equal to 5% by weight of the aqueous electrolyte makes it possible to obtain, in an unexpected and particularly effective manner, a complex effect of protecting the electrodes. and increasing the conductivity of the device. More particularly, the addition of the alkali silicates makes it possible to stabilize the elements of the electrochemical cell, as much in the cathode compartment as in the anode compartment and for the anode and cathode electrodes. In one embodiment, the alkali silicate has a mass concentration of aqueous electrolyte ranging from 5% to 30%. Beyond this 30% limit, the electrolyte becomes gelatinous, which poses problems for evacuating hydrogen from the device. In one embodiment, the alkaline base is selected from the following elements: sodium hydroxide, lithium hydroxide, and potassium hydroxide.

In one embodiment, the alkali silicate is selected from the following elements: lithium silicate, sodium silicate, and potassium silicate.

According to a first embodiment, the electrically conductive means is elongate and of total length L, with a curved section and a radius of curvature R: R being less than 50 × 10 ^-6 m (50 micrometers), space inter-electrode has a thickness of between 1 x 10 ^"9 m and 2 x ^{10" 2} m (1 nanometer and 2 centimeters), and the ratio L / R is greater than 3 × 10 ^-6 (three million) so that the first electrode provides on the nanometer scale with millimeter a significant increase effect of the electric field seen by the second electrode According to a second embodiment, the ratio L / R is greater than or equal to 2.5 x 10 ⁷ (25 million).

Such first and second embodiments make it possible to take advantage of the aforementioned corona effect while removing the problems of destruction, as a metal powder, of the electrodes constituting the device.

According to one embodiment, the first electrode and / or the second electrode have an area greater than 5 cm ² . Such a surface makes it possible, in fact, to obtain an electrolysis or reverse electrolysis device having an adequate efficiency with regard to the investment costs it represents.

In one embodiment, the electrically conductive means is elongate and of total length L greater than 1 x 10 ³ m (1 kilometer). In one embodiment, the first electrode is made of a first material and the second electrode is made of a second material different from the first material. Indeed, it has been found that the electrolyte according to the invention allows the differential use, between the cathode compartment and the anode compartment, of galvanic pairs of electrode materials, which makes it possible to modulate in an interesting manner the properties of the device. electrolysis or reverse electrolysis.

In one embodiment, the first electrode forms an anode and the second electrode forms a cathode, the anode being made of elements that are more electronegative than the cathode. in order to generate an increase in the intensity of the current flowing through this anode and cathode. The fact of using different materials for the first and second electrodes and, in particular, anode consisting of more electronegative elements than the cathode thus favors the increase of the electrical intensity of the electrochemical cell.

In this case, according to one embodiment, the first material is a stainless steel fabric and the second material is a nickel fabric.

According to an alternative embodiment, the first electrode and the second electrode are made in one and the same first material.

According to one embodiment, the first material is a steel and, if appropriate, the first electrode is formed from a steel wool. Other characteristics and advantages of the invention will emerge clearly from the description which is given hereinafter, by way of indication and in no way limitative, with reference to the appended drawings, in which:

^■ Figure 1 is a perspective diagram of a first possible embodiment of an electrolysis apparatus according to the invention;

^■ Figure 2 is a perspective diagram of a second possible embodiment of an electrolysis apparatus according to the invention, namely a capacitor;

^■ Figure 3 is a diagram showing the resistance of an electrolyser according to the invention and the intensity of the current passing through the electrodes, depending on the potential difference applied between the terminals of the electrolyzer;

^■ figure 4 shows a diagram representing the intensity of the current through the anode and cathode of an electrolytic device according to the invention, depending on the evolution of the temperature;

^■ Figure 5 is a perspective diagram of a fourth possible embodiment of an electrolysis apparatus according to the invention, wherein the anode and cathode are made from different materials;

^■ Figure 6 is a perspective diagram of another electrolysis apparatus according to the invention, the first electrode and the second electrode system having a symmetrical or pseudo-symmetrical structure.

Reference is made to FIG. 1, which illustrates an electrolysis device 1 according to the invention comprising an outer hollow enclosure 3 made using a glass container. The outer hollow enclosure 3 encloses an anode compartment 4 and a compartment cathode 5 respectively comprising an anode nickel fabric 6 and a cathode nickel fabric 7.

These nickel-forming anode 6 and cathode 7 fabrics are composed of nickel wire having a diameter of 55 μηη, a spacing of 80 μηη and a facing surface of 25 cm ² .

However, it would also be possible to use anode compartments 4 and cathodic 5 comprising identical or different steel fabrics, formed based on steel wool for example.

The electrolysis device also comprises a generator 8 which is used to apply a potential difference P, that is to say a voltage, between the anode 6 and the cathode 7.

On the other hand, an inner surface 9 of the anode 6 and an outer surface 10 of the cathode 7 are positioned opposite one another and define between them an interelectrode space January 1 inside which is placed an electrolyte 12.

Comparative experiments were carried out between different types of electrolytes 12.

According to a first variant, the inter-electrode space 1 1 has been filled with an electrolyte 12 made from deionized water. The implementation of the electrolysis device 1 then led to a rapid destruction of the nickel fabrics forming the anode 6 and the cathode 7 in only a few hours, with rapid appearance in the electrolyte of a green oxide compound or nickel hydroxide.

According to a second variant, the inter-electrode space 11 has been filled with an electrolyte 12 consisting of water demineralized water and sodium hydroxide. In the same way as previously, it has been observed a progressive destruction of the nickel fabrics forming the anode 6 and the cathode 7 in a few tens of hours, with rapid appearance in the electrolyte of a green compound of hydroxide nickel.

According to a third variant, the inter-electrode space 11 has been filled with an electrolyte 12 consisting of demineralised water, 20% sodium silicate solution and 20% sodium hydroxide. In this case, no corrosion was observed on the anode 6 and the cathode 7, or degradation of the electrolyte 12 during an operating time of 1000 hours at constant intensity. This third and last variant of electrolyte 12 has thus made it possible to limit the destruction of the electrodes during the electrolysis reaction.

Reference is now made to Figure 2.

This FIG. 2 illustrates an electrolysis device 1 according to the invention similar to that of FIG. 1, comprising an outer hollow enclosure 3 made using a glass container, enclosing an anode compartment 4 and a cathode compartment 5. respectively comprising anode-forming nickel fabric 6 and cathode-nickel fabric 7.

According to this embodiment, the nickel fabrics forming anode 6 and cathode 7 have a surface facing 1 dm ² and a gap of 5 mm.

The electrolysis device also comprises a generator 8 which is used to apply a potential difference P which has been varied between the anode 6 and the cathode 7, and an inter-electrode space 11 filled with an electrolyte 12 composed of water, 20% by weight sodium silicate solution and 20% by weight sodium hydroxide.

A series of experiments were carried out on the basis of this embodiment of the electrolysis device 1 and made it possible to obtain a resistance R of the electrolyser of 20 Ohm at 1, 9 V, of 8 Ohm at 2 V, of 5 Ohm at 2.1V, 2.5 Ohm at 2.3V and 1.5 Ohm at 3V.

The results of these experiments are summarized in the table below

FIG. 3 represents a diagram illustrating the resistance R of the electrolyser and the intensity I of the current across the two electrodes, as a function of the potential difference P applied between the anode 6 and the cathode 7. was carried out with an electrolysis cell intended for the production of hydrogen, composed of a cathode made from a nickel fabric, an anode made of stainless steel fabric, the two electrodes having a surface facing each other. of 14 dm ² and spaced from each other by 5 mm. The electrolyte was composed of 30% hydroxide potassium and 20% potassium silicate in deionized water. The measured efficiency, at ambient temperature and pressure, for a voltage of 1.9 volts under these non-optimal conditions was found to be 88%. This type of device whose manufacturing and operating costs are very low can consider a commercial operation.

According to a third embodiment (not shown) of the electrolysis device according to the invention, the electrolytic device 1 similar to that of FIG. 2 nevertheless has anode compartments 4 and cathode 5 respectively filled with a steel plate having a surface 25 cm ² , forming anode 6, and a steel plate having a surface of 25 cm ² , forming a cathode 7.

The steel used is a galvanized steel consisting of a thin layer of over 93% zinc, 3% iron and 4% oxygen. This electrolytic device 1 has been implemented for a period of 1000 hours. It was observed at the end of this experiment a slight degradation of the anode 6, a blackening of the cathode 7 and the deposition of small black particles at the bottom of the solution, the apparent degradation of the anode being due to stripping the zinc layer by electrolysis (the steel was officially sold as untreated by zinc anodizing).

Chemical analysis of the surface of the anode 6 after 1000 hours of operation of the electrolytic device 1 revealed the presence of a thin layer composed of 87% iron, 1% manganese, 2% silicon, 4 % sodium and 6% oxygen.

The chemical analysis of the surface of the cathode 7 after 1000 hours of operation of the electrolytic device 1 shows the presence of a thin layer composed of 80% iron, 1% manganese, 3% silicon, 6% sodium, 8% oxygen and 2% zinc.

These results are summarized in the table below:

Il découle de ces résultats que la couche de zinc permettant de protéger l'acier a été détruite lors de l'électrolyse du côté anode 6 et en grande partie détruite du côté cathode 7 de sorte qu'il ne subsiste que quelques pour cents de zinc qui ont réagi avec le silicate de sodium et ont donné cette couleur noire à la cathode 7.

It follows from these results that the zinc layer for protecting the steel was destroyed during electrolysis on the anode side 6 and largely destroyed on the cathode side 7 so that only a few percent of zinc remains which reacted with the sodium silicate and gave this black color to the cathode 7.

After removal of the zinc layer, the iron electrodes were stabilized and protected by sodium silicate because of the creation of a conductive and inorganic passivation layer mixing on the one hand the composition elements of the electrode, on the other hand the silicate composition elements.

This is true for both electrodes, anode 6 and cathode 7.

According to a fourth embodiment (not shown) of the electrolysis device according to the invention, the electrolysis device 1 comprises an outer hollow chamber 3, of cylindrical shape, made using a glass container, enclosing a compartment anodic 4 and a cathode compartment 5.

These anode compartments 4 and cathode respectively comprise an anode 6 and a cathode 7 formed from a 316 L stainless steel fabric composed of 36 μm diameter filaments. These 316L stainless steel fabrics have a surface area of 6 cm ² and a gap of 4 cm.

The electrolysis device also comprises a generator 8 which is used to apply a potential difference P of 2.5 V between the anode 6 and the cathode 7 and an interelectrode space 11 filled with an electrolyte 12 composed of 20% by weight potassium hydroxide and 20% by weight potassium silicate in deionized water.

This electrolytic device 1 has been implemented at high temperature. The results of these tests are mentioned in the table below:

Temperature (in ° C) Intensity (in amperes)

 0.08

 25 0.1

 40 0.19

 50 0.24

 70 0.27

80 0.28 When carrying out these tests, no corrosion was observed on the 316L stainless steel electrodes, but only the deposition of a light layer of the passivation layer type.

Moreover, FIG. 4 illustrates a diagram representing the intensity of the current flowing through the anode 6 and the cathode 7 of this electrolytic device 1 as a function of the evolution of the temperature.

This curve forms an optimum around 50 ° C before bending towards 60 ° C. In conventional aqueous electrolysis (KOH), the optimum in intensity depends on the KOH concentration and the operating temperature.

According to other alternative embodiments (not shown) of the electrolysis or reverse electrolysis device according to the invention, the electrolysis device 1 comprises an outer hollow enclosure 3, of cylindrical shape, made with the aid of a glass container, enclosing an anode compartment 4 and a cathode compartment 5, which respectively comprise an anode 6 and a cathode 7.

Thanks to the protective effect of alkali silicates, it is possible to use a larger panel of materials than the conventional nickel anodes of industrial alkaline electrolyses. In particular, it becomes possible to promote the flow of current by varying the ability of certain elements to more easily release an electron.

The electrolysis device also comprises a generator 8 which is used to apply a potential difference P between the anode 6 and the cathode 7 and an inter-electrode space 11 filled with an electrolyte 12.

A first variant is described below.

According to this first variant, the electrolyte 12 is composed of a solution of demineralized water, 10% by weight of sodium hydroxide and 20% by weight of sodium silicate. In addition, a first stainless steel fabric electrode and a second nickel fabric electrode are used, these two electrodes respectively having a facing surface of 10 cm ² and an inter-electrode spacing of 3 cm. In addition, the potential difference between the voltage between the terminals of the anode 6 and the cathode 7 is 2.5 V. According to this first variant, when the first electrode of stainless steel fabric is positioned in the cathode compartment 5 and forms the cathode 7, on the one hand, and the second electrode of nickel fabric is positioned in the anode compartment 4 and form the anode 6, on the other hand, the intensity of the current flowing through the device is 0.17 A.

On the contrary, when the first stainless steel fabric electrode is positioned in the anode compartment 4 and forms the anode 6, on the one hand, and the second nickel fabric electrode is positioned in the cathode compartment 5 and forms the cathode 7, on the other hand, the intensity of the current flowing through the device is 0.37 A.

There is therefore an absolute increase of 1 10% of the intensity obtained according to one or the other of these two embodiments.

A second variant is described below.

According to this second variant, the electrolyte 12 is composed of a solution of demineralised water, 10% by weight of sodium hydroxide and 20% by weight of sodium silicate. In addition, a first stainless steel fabric electrode and a second carbon felt electrode electrode are used, these two electrodes respectively having a facing surface of 10 cm ² and an inter-electrode spacing of 3 cm.

In addition, the potential difference between the voltage between the terminals of the anode 6 and the cathode 7 is 2.5 V. According to this second variant, when the first electrode of stainless steel fabric is positioned in the compartment 5 and forms the cathode 7, on the one hand, and that the second carbon felt electrode is positioned in the anode compartment 4 and forms the anode 6, on the other hand, the intensity of the current flowing through the device is 0.11 A. On the contrary, when the first stainless steel fabric electrode is positioned in the anode compartment 4 and forms the anode 6, on the one hand, and the second carbon felt electrode is positioned in the cathode compartment 5 and forms the cathode 7, on the other hand, the intensity of the current flowing through the device is 0.17 A. This results in an absolute increase of 54% in the intensity obtained according to one either of these two achievements.

A third variant is described below. According to this third variant, the electrolyte 12 is composed of a water solution, 20% by weight of sodium hydroxide and 20% by weight of sodium silicate. In addition, a first 316L stainless steel cloth electrode and a second variable electrode are used, these two electrodes respectively having a facing surface of 6 cm ² and an inter-electrode spacing of 3 cm.

In addition, the potential difference between the voltage between the terminals of the anode 6 and the cathode 7 is 2.5 V.

When the first 316L stainless steel cloth electrode is positioned in the anode compartment 4 and forms the anode 6, on the one hand, and a second nickel cloth electrode is positioned in the cathode compartment 5 and forms the cathode 7, on the other hand, the intensity of the current flowing through the device is 0.17 A.

When the first 316L stainless steel cloth electrode is positioned in the anode compartment 4 and forms the anode 6, on the one hand, and a second nickel cloth electrode - covered this time with a layered deposit Kontakt Chemie colloidal graphite colloidal graphite - is positioned in the cathode compartment 5 and forms the cathode 7, on the other hand, the intensity of the current flowing through the device is 0.24 A.

The results obtained during the realization of these first, second and third variants are summarized in the table below.

Spacing Surfaces

 Electrode Voltage Next Electrolyte Anode Cathode Intensity (in volts) (in cm) (in cm2) (in A)

 10% NaOH -

2.5 3 10 cm2 20% Silicate Na fabric nickel fabric stainless steel 0.17 A

 10% NaOH -

2.5 3 10 cm2 20% Silicate Na fabric stainless steel fabric nickel 0.37 A

 10% NaOH -

2.7 3 10 cm2 20% Silicate Na felt carbon fabric stainless steel 0.1 1 A

 10% NaOH -

2.7 3 10 cm2 20% Silicate Na fabric stainless steel felt carbon 0.17 A

 20% KO H -

2.5 3 6 cm2 20% Silicate K fabric stainless steel fabric nickel 0.17 A

 20% KO H -

2.5 3 6 cm2 20% Silicate K fabric stainless steel fabric nickel graphite 0.24 A According to an advantageous embodiment directly resulting from these embodiments, the first electrode 6, 106 made from the first material forms an anode, the second electrode 7, 107, made from the second material forms a cathode and the first material has a potential of redox lower than the redox potential of the second material. In other words, the first material used to form the anode can be made in a less noble metal than the second material so as to increase the intensity of the electric current likely to flow between the cathode and the anode, within the electrolysis device. . In this way, it is possible to generate, as previously, an increase in the intensity of the electric current likely to flow between the cathode and the anode without risking damaging said cathode and anode since they are protected by the aqueous electrolyte. Reference is now made to FIG. 6, which illustrates another electrolysis device 101, with axis 102 of revolution, according to the invention.

This electrolysis device 101 comprises an outer hollow enclosure 103, here of cylindrical shape. The outer hollow enclosure 103 encloses an anode compartment 104 and a cathode compartment 105. These two compartments 104, 105 are generally cylindrical in shape, coaxial with axis 102. They are placed one inside the other, here the anode compartment 104 surrounding the cathode compartment 105 to the outside.

The anode compartment 104 comprises an anode electrode 106 and the cathode compartment 105 comprises a cathode electrode 107. A potential difference is applied at 108 between the anode 106 and the cathode 107. On the other hand, the inner surface 109 of the anode 106 and the outer surface 1 10 of the cathode 107 are located facing each other and define between them an inter-electrode space 1 1 1. A filter 1 12, placed in the international space 1 1 1 electrodes, separates the anode 106 of the cathode 107 and allows the presence between them of an electrolyte.

According to one possible embodiment, to form respectively the anode 106 and the cathode 107, there is provided a structure consisting of a generally hollow cylinder-shaped filter with pores of 25 x 10 ^-6 m (25 micrometers). and towards the interior of this structure, steel wool having a small radius of curvature R of 9 x 10 ^-6 m (9 micrometers) is moderately packed - with a porosity of greater than 70%, the length L total of each steel wool electrode being ⁴ m (10 km). In the context of tests, it has been used as an electrolyte of city water (tap water), slightly ionized, a passive system consisting of a magnet of cylindrical shape 1 13 such as a magnet NdFeB, placed in the center of the cathode compartment 105 provided for this purpose with a central empty space. However, these tests resulted in the decomposition of the two electrodes into oxide powders or metal hydroxides.

Other tests were then conducted from an elemental electrolyzer, made in a cylindrical geometry, without any separation wall between the anode compartment and the cathode compartment (filter or membrane). The surface facing each electrode was set at 30 cm ² , the voltage was set at 2.5 V, the gap between the electrodes was set at 5 x 10 ^-3 m (5 mm) the electrolyte consisting of 20% by weight sodium silicate and 20% by weight of sodium hydroxide in demineralized water, which made it possible to demonstrate the high conductivity of the electrolyte according to the invention while at the same time guaranteeing the stability of the electrodes, even in the case of steel.

It should be noted that the invention is not limited to the embodiments described and illustrated in this document but extends on the contrary to any other type of electrolysis or reverse electrolysis device for which the use of an aqueous electrolyte is necessary, irrespective of their structural geometry or their operation.

In particular, all the electrolysis and reverse electrolysis devices which comprise an overall structure of the organized or unorganized electrically conductive means of bulk electricity are covered.

Claims

claims 1. Apparatus for electrolysis or reverse electrolysis capable of performing electrolysis or reverse electrolysis and comprising a first electrode (6, 106), a second electrode (7, 107) and an inter-electrode gap (1 1, 1 1 1 ) comprising a functional medium arranged between the first electrode (6, 106) and the second electrode (1 1, 1 1 1);  wherein the first electrode (6, 106) is made from at least one electrically conductive means adapted to be at all locations at the same electrical potential so as to constitute said first electrode (6, 106);  characterized in that the functional medium is an aqueous electrolyte composed of water, an alkaline base, and alkali silicate in a concentration greater than or equal to 5% by mass of the aqueous electrolyte so as to obtain a protective effect of the first (6, 106) and second electrodes (7, 107) by creating a conductive and conductive passivation layer mixing, on the one hand, composition elements of said first (6, 106) and second electrodes (7, 107) and, on the other hand, compositional elements of the alkali silicate. 2. Electrolysis or reverse electrolysis device according to claim 1, wherein the alkali silicate has a mass concentration of aqueous electrolyte ranging from 5% to 30%. 3. Electrolysis or reverse electrolysis device according to claims 1 or 2, wherein the alkaline base is selected from the following elements: sodium hydroxide, lithium hydroxide, and potassium hydroxide. 4. Apparatus for electrolysis or reverse electrolysis according to any one of claims 1 to 3, wherein the alkali silicate is selected from the following elements: lithium silicate, sodium silicate, and potassium silicate. 5. Apparatus for electrolysis or reverse electrolysis according to any one of claims 1 to 4, wherein the first electrode and / or the second electrode have a surface greater than 5 cm ² . 6. Apparatus for electrolysis or reverse electrolysis according to any one of claims 1 to 5, wherein the electrically conductive means is elongated and of total length L, curved section and radius of curvature R: ■ R being less than 50 x 10 ^"6 m (50 micrometers), ^■ the inter-electrode space (1 1, 1 1 1) has a thickness of between 1 x 10 ^"9 m and 2 x ^{10" 2} m (1 nanometer and 2 centimeters), and ^■ the ratio L / R is greater than 3 × 10 ⁶ (three million) so that the first electrode (6, 106) provides the scale of nanometer to millimeter effect a significant increase in the electric field seen by the second electrode (7, 107). The electrolysis or reverse electrolysis device of claim 6, wherein the L / R ratio is greater than or equal to 2.5 x 10 ⁷ (25 million). 8. The electrolysis or reverse electrolysis device according to any one of claims 1 to 7, wherein the electrically conductive means is elongated and of total length L greater than 1 x 10 ³ m (1 kilometer). An electrolysis or reverse electrolysis device according to any one of claims 1 to 8, wherein the first electrode (6, 106) is made of a first material and the second electrode (7, 107) is made in a second material different from the first material. The electrolysis or reverse electrolysis device according to claim 9, wherein the first electrode (6, 106) forms an anode and the second electrode (7, 107) forms a cathode, the anode being composed of elements more electronegative than the cathode so as to generate an increase in the intensity of the current flowing through this anode and cathode. 1 1. An electrolysis or reverse electrolysis device according to any one of claims 1 to 8, wherein the first electrode (6, 106,) and the second electrode (7, 107) are made of one and the same first material. 12. Electrolysis or reverse electrolysis device according to any one of claims 9 to 11, wherein the first material is a steel. 13. The electrolysis or reverse electrolysis device according to claim 12, wherein the first electrode is formed from a steel wool. 14. Electrolysis or reverse electrolysis device according to claim 10, wherein the first material is a stainless steel fabric and the second material is a nickel fabric.