WO2006007863A1

WO2006007863A1 - Electrolysis apparatus with solid electrolyte electrodes

Info

Publication number: WO2006007863A1
Application number: PCT/EP2004/007983
Authority: WO
Inventors: Marco V. Ginatta
Original assignee: Cathingots Limited
Priority date: 2004-07-16
Filing date: 2004-07-16
Publication date: 2006-01-26

Abstract

The apparatus for the production of metals comprising an anodic system of dimensionally stable anodes (18) with their lower portion immersed in a liquid electrolytic bath (14), wherein a solid electrically conductive layer is maintained on the external surface of the anodes (18) by providing cooling on the internal body of the anodes by using manifolds (20, 21) for the intake and exit of the cooling fluid, the cathodic system showing dimensionally stable cathodes with their portion immersed in the liquid electrolyte bath, wherein a solid electrically conductive layer is maintained on the external surface of the cathodes by providing cooling on the internal body of the cathodes (12) by using manifolds for intake and exit of the cooling fluid.

Description

ELECTROLYSIS APPARATUS WITH SOLID ELECTROLYTE ELECTRODES

[001] A solid layer of electrolyte is made to coat the anodes and the cathodes where the skin is maintained in the solid state by cooling the anodes used in the production of aluminium, titanium and other metals.

[002] The present invention relates to the electrochemical gas evolution and metal reduction in electrolytic cells, on non-metal electrode surfaces that are non- consumable and dimensionally stable.

[003] The present invention relates to systems and methods for protecting anodes and cathodes and other electrodes and electrode supports from degradation by molten salts electrolyte baths and from anodic gases generated in the electrolytic cell.

Background of the invention

[004] A number of metals including aluminium, beryllium, chromium, cobalt, lead, lithium, magnesium, nickel, silicon, thorium, titanium, vanadium, zinc, zirconium, rare earths and mishmetal can be produced by electrolytic processes. Each of these electrolytic processes employs the electrodes in a highly corrosive environment. [005] The energy and cost of metals electrolytic production can be significantly reduced with the use of inert, non-consumable and dimensionally stable anodes and cathodes. Replacement of traditional carbon based anodes and cathodes with inert anodes should permit significant benefits because inert anodes produce no CF4 emissions and inert cathodes do not introduce carbon in the electrolyte. [006] The use of a dimensionally stable anode allows efficient cell designs both in the horizontal and vertical configurations, with high productivity and optimal anode- cathode distances, with balanced thermal regimes and consequent energy savings and capital costs.

[007] The most significant challenge to the industrialisation of the inert anode technology is the anode material.

[008] The anode material must satisfy a number of difficult requirements. For example, the material must not react with or dissolve to any significant extent in the electrolyte. It must not react with the anodic gases or corrode in gases-containing atmosphere. It should be thermally stable while immersed in the electrolyte at temperatures above IOOO⁰C. It must be relatively inexpensive and should have good mechanical strength. It must have high electrical conductivity at the electrolytic cell operating temperature, so that the voltage drop at the anode is low. In addition, metals produced with inert anodes should not be contaminated with constituents of the anode material to any appreciable extent.

[009] Although cermet electrodes are capable to operate as anodes in the electrolytic cell, they have at least two serious problems. First they have difficulty in producing metal of sufficient purity to satisfy customer standards, and they are susceptible to cracking during cell start-up when subjected to temperature differentials. In addition, components of the anode support structure assembly are also subject to damage from thermal shock during cell start-up and from corrosion during cell operation.

[010] Accordingly, there still remains a need for a means of protecting cermet electrode and the anode support structure from corrosion and erosion during cell operation.

[011] Meeting the majority of the requirements for successful inert anode material, metals have electrical and thermomechanical performances superior to that of the carbon anode currently in use: very high electronic conductivity combined with excellent thermal shock resistance and mechanical robustness. In addition, metals are easily fabricated and present fewer difficulties in service, connecting to the current busbars is simple.

[012] As mentioned, the chemical and electrochemical performance of the anode depend upon the surface film characteristics. Although the surface film can be prepared on the metal anode before being installed in service into the cell, the start-up operations, the electrolyte composition and the electrolytic reactions will alter the film characteristics.

[013] If the surface film cannot be controlled independently from the electrolytic operation conditions, the anode metal will anodically dissolve in the electrolyte eventually contaminating the metal produced.

[014] Chemical and electrochemical stability are conferred to the inert anode by a surface film that is thick enough to prevent attack of the underlaying material either by the electrolytic bath or by anodic gases and thin enough to allow electronic current to flow with minimal resistance.

[015] The damaging effects of the above operating conditions are intense at the geometrical current densities used in operation, of the order of 1 Amp/cm2, since we have to consider that the effective current densities on the anode material is even higher because only a portion of anode surface is electrochemically working at any time, while the rest being covered thus electrically insulated by bubbles.

[016] Clearly many of the above problems would be mitigated if the electrolytic cell could be operated at lower temperatures.

[017] However, the electrolytic cells for producing metals requires that the process operate at relatively high temperatures, because of chemical and electrochemical constraints. Example of constraints are the requirements of achieving high feed solubility in the electrolyte, for operating with liquid cathodes, and for maintaining optimal species oxidation state and structure in the electrolyte.

[018] D'Astolfo et al. in their US Patent Application N. 20040094409A1 of May 20,

2004, summarize the current status of the search for inert anodes in the aluminium industry, and illustrate the difficulties of trying to keep in operation a pre- manufactured surface layer on the anode only relying on the weak inherent chemical stability of the surface film.

[019] Siljan et al. in their PCT International Paten Application N. WO 2004/018737 of March 04, 2004 illustrate the difficulties of trying to slow the anode material dissolution in operation by slightly lowering the temperature of the anode material, thereby aiming to lowering the solubility of the anode surface compound in the electrolyte.

[020] In conclusion, the only way to have a long lasting inert dimensionally stable anode system is to develop a new kind of working electrode surface that will operate the anodic half-reaction of gas evolution and the cathodic half-reaction of metal reduction on the surface of a physically and chemically stable layer covering the electrode underlaying material.

Statement of the invention

[021] The matter of the invention is defined by the claims which follow.

[022] The school of though regarding the electrode interphases at the base of this work is contained in the M. V. Ginatta Ph.D. Thesis (Ref. 1).

[023] The electrodes object of this invention satisfies all the requirements for an inert, non-consumable and dimensionally stable electrode by having a layer of solidified electrolyte permanently on the surface.

[024] The cooling of the internal part of the electrode to temperatures below the melting point of the electrolyte, produces the solidification of a layer of electrolyte used in the electrolytic cell, on the external surface of the electrode.

[025] The thickness of the solid skin is directly proportional to the intensity of the cooling and can be set at the optimal thickness by monitoring the cell voltage.

[026] At the cooled electrodes operation temperatures the solid electrolyte layer maintains values for electronic conductivity that are sufficient to sustain the electrode half-reaction at high current density. Furthermore the structure of the solid skin created under anodic oxidizing and cathodic reducing conditions is generally full of defects and entraps different kinds of impurities.

[027] One of the objects of the present invention is the electrolytic production of aluminium, titanium and other metals using the electrodes described.

[028] Another object of the present invention is the cooling applied to the inside of the non-consumable anode with the aim of growing a film of solidified electrolyte on the outside that will electrochemically work as the surface of the electrodes of electrolytic cells.

[029] Another object of this invention is that the electrodes used as anodes host the half-reaction of oxygen or chlorine ions oxidation to neutral atoms, and the reaction of formation of oxygen or chlorine molecules from two of the newly formed oxygen or chlorine atoms.

[030] Another object of the present invention is the control of the rate of cooling of the anodes that will determine the thickness of the solidified electrolyte film on the anodes and the electrical contact resistance between the solid skin and the underlaying anode material.

[031] In this invention the solid layer or skin term is used to mean both the solid layer attached to the anode material and the mushy layer between the solid layer and the liquid electrolyte. The nature of this layer on the anodic surfaces object of this invention is different from the paste state of the side ledges because of the action of the anodic gas evolution.

[032] Another object of this invention is the condition of maintaining the electrodes in the electrochemical conditions of functioning as electrodes of the second kind having electronic conductivity.

[033] Another object of this invention is that the electrode electrochemically working interphase does not contain the underlaying electrode metal layer.

[034] Another object of the present invention is the optimum thickness of the solid skin that maintains the underlaying metal dry for the minimum electrode interphase voltage.

[035] Another object of the present invention is that the solid skin thickness on the electrodes is made dynamically stable by controlling the rate of flow of the cooling fluid within the non-consumable electrode.

[036] The material of which the electrodes of the present invention are made can be any metal or alloy since the temperature differential provided by the cooling fluid maintains the metal or alloy in the solid state, and the protection insured by the coverage with solid electrolyte skin will not permit the anodic dissolution of the metal or alloy in the electrolyte, or the chemical attack from the electrolyte.

[037] Another object of this invention is the solid electrolyte skin chemical composition and structure that respond to the local chemistry, electrochemistry and thermomechanical conditions.

[038] Another object of the present invention is the solid skin that is self-repairing in service, and if the film is lost or damaged it quickly reforms.

[039] Another object of the present invention is the feature that should the surface film be attacked by the electrolyte or by the evolving gases, the nature of the dissolution products will be that of the electrolyte itself and thus will not contaminate the metal produced.

[040] Another object of this invention is the fact that the solid layer on the electrode material does not have the chemical tendency of dissolving in to the liquid, because the liquid itself has a chemical composition that is in equilibrium with the chemical composition of the solid.

[041] Another object of this invention is characterized in that the solid layer on the electrodes contain different kinds of impurities in such a way that they contribute to the electrical conductivity of the solid layer.

[042] Another object of this invention is characterized by that the electrodes and the electrolyte are at high temperatures in high radiation intensity environment where photoelectrochemical effects occurs with electron-hole pairs creation, that is the anodic half-reactions are photoassisted on n-type doped anodes for oxidation reactions, and the cathodic half-reactions on p-type doped cathodes for reduction reactions.

[043] Another object of this invention is characterized by that the applied potential on the cell effects the accumulation of charges within the solid layers and gives them the electrical conduction degenerate metallic behaviour.

[044] Another object of the present invention is the cooling fluid circulating within the electrodes that can be any liquid which is stable at the operation temperature; for example any metal or mixtures that is liquid in that range of temperatures as Na and

K, Sn and Pb.

[045] Another object of the present invention is the ancillary heat exchanger system used to cool the anode cooling fluid that can be of any type, that is liquid/air or liquid/liquid.

[046] Another object of this invention is that the solid skin thickness on the electrode materials can be maintained at a value between 0.001 mm to 30.0 mm, with some operative values between 0.01 and 3.0 mm.

[047] Another object of this invention is that the start-up operation of the cell will be simplified since the fluid circulating in the electrodes can be heated to contribute to reaching the operation temperature.

[048] Another object of this invention is that the non-consumable electrodes can be also made of iron and other base metals or alloys whose melting point is higher than

1'000⁰C.

[049] Another object of this invention is that the cooling fluid circulating within the electrodes can be a metal halides and molten salt mixture as for example fluorides and fluoborates.

[050] Another object of this invention is that the cooling can be operated by using an air or gasses flow within the internal portion of the electrodes.

[051] Another object of this invention is that the cooling can be operated by using water in liquid or vapour state.

[052] Another object of this invention is that the non-consumable anodes can be coupled with the drained cathodes in order to further improve the efficiency of the cell.

[053] Another object of this invention is that for the anode material also non-porous carbon materials can be used and the solid skin is firmly attached to the anode surfaces. The anodic gases evolution on the solid skin will not contain CO2 because carbon is not in contact with the electrolyte.

[054] Another important advantage of the anodes object of this invention is their physical design, since we can shape these anodes to any geometrical configuration that will favour anodic gas bubbles release from the anode surfaces.

[055] Another object of this invention is the shape of the anode system which can be that of a solid block externally resembling the carbon anodes, with a internal labyrinths for the flow of the cooling fluid.

[055] Another object of this invention is the provision whereby the thermal regime of the electrolytic cell is not disturbed by the internal cooling of the anode. In fact the usual carbon material anodes are responsible for a large fraction of the total heat loss, since they have a large full cross section of solid thermally conducting carbon materials that extracts heat from the electrolytic cell.

[057] The electrodes object of this invention are provided in their interior of a labyrinth construction of thermally insulating materials in order to extract heat only from the back side of the active electrode surfaces immersed in the electrolyte. [058] A further object of this invention that is important for the energy efficiency of the cell is the fact that the internal electrode cooling improves the electrical conductivity of the underlying electrode material and also because the electrodic material cross section for the conduction of heat is much smaller than that of the usual carbon anodes.

[059] Another object of this invention is that the solid skin on the electrodes are working for an indefinite period of time, certainly as long as the life of the cell. [060] Another object of this invention is that the anode system has the solid layer pre- manufactured outside the electrolytic cell before being immersed in the electrolyte. [061] Another object of this invention is that the anode surfaces are coated with a mixture of metal compounds that will not dissolve into the electrolyte upon being installed into the electrolytic cell, because of the cooling provided to the anodes. [062] Another object of this invention is that by using the described electrolytic apparatus there is no evidence of chemical interaction between the solid electrolyte layer and the underlaying electrode material, which however can be conditioned and finished in order to obtain a good electrical contact between skin and material. [063] Another object of this invention is that in the vertical configuration of the cell the metal reduced on the cathodic solid skin is not entrapped in the surface layer but it freely falls in the drained region of the cell.

Description of the Drawings

[064] The process and apparatus object of the invention will be described with reference to the appended drawings for the case of the aluminium and titanium producing electrolytic cells, wherein:

[065] Figure 1 is a partially sectioned front view of an apparatus for carrying out the process according to the invention. The shape of the anode system can be that of a solid block having features resembling the carbon anodes, with a internal labyrinth for the flow of the cooling fluid.

[066] The apparatus vertical view of figure 1 schematically illustrates the cell container 10, the cathode current busbar 11, the cathode block 12, the liquid metal pad 13, the electrolytic bath 14, the anode/cathode distance 15, the evolving anodic gas bubbles 16, the solid skin 17 adhering to the anodic material surfaces below the electrolyte level, the anode material 18, the anode cooling labyrinth 19, the manifolds system for entering 20 and exiting 21 the cooling fluid, the structure 23 for suspending the anodes, the solidifies electrolyte 24 above the electrolyte level, the crust of the feed 25, the level of the electrolyte 26, the solid ledge 27, the mushy region 28, the graphite blocks 29, the lining 30. The DC power supply, not shown, is connected at the anodic and cathodic current collectors.

[067] In figure 1, the cooling system, is connected to manifolds 20 and 21. The heat exchanger, not shown, can be based on any principle and have any shape. If the cooling fluid used is a liquid, it can be in form of a heat exchanger tube or plate. The anode material can be made of an oxidation resistant metal or alloy in order to directly use air as the cooling medium.

[068] The anode upper portion, above the level of the electrolyte, is coated with a thick layer of solidified electrolyte 24, that is obtained both with the initial procedure by dipping and by condensing electrolyte, and it is maintained during operation up to joining with the feed crust.

[069] In figures 2 are illustrated anodic systems composed of a plurality of anodes made of medium diameter pipes inside which the cooling fluid flows, wherein on the outside of the pipes, protected by the solid skin, the anodic gas evolves, without coalescing in large stationary bubbles underneath the anodes, and the cathodes are made of separate members 31, cooled with the solid layer 32, and the reduced metal drops and particles fall through the cathode members into a collecting region 13. [070] In figures 3 are illustrated anodic systems composed of a plurality of anodes made of small diameter pipes inside which the cooling fluid flows, wherein on the outside and in between the pipes, protected by the solid skin, the anodic gas easily evolves, without coalescing in large stationary bubbles underneath the anodes. [071] This geometrical configuration sustains a larger effective anodic current density by minimizing the anode surface blocked by the stationary bubble, that is not electrochemically working.

[072] In figure 4 there is a partially sectioned view of an apparatus for carrying out the invention for example for the electrolytic production of titanium with a vertically configured cell. It schematically illustrates the cell container 40, the cooling jacket 41, the cylindrical anode material 42, the cathode surface 43, the electrolyte 44, the liquid/solid electrolyte interface 45, the solid layer of electrolyte 46, the solid electrolyte/anode material interface 47, the electrolyte level 48, the solidified electrolyte above the electrolyte level 49, the bubbles of evolving anodic gases 50, and the reduced metal falling to the product collection region 51. [073] In figure 5 there is a partially sectioned view of an apparatus for carrying out the invention for electrolytically produce titanium with a horizontally configured cell. The apparatus vertical view schematically illustrates the cell container 10, the cathode current feeder 11, the cathode bock 12, the liquid metal pad 13, the electrolytic bath 14, the anode/cathode distance 15, the evolving anodic gas bubbles 16, the solid skin 17 adhering to the anodic material surfaces below the electrolyte level, the anode material 18, the anode cooling labyrinth 19, the manifold system for entering 20 and exiting 21 the cooling fluid, the anodic current busbar 22, the structure 23 for suspending the anodes, the solidified electrolyte 24 above the electrolyte level, the level of the electrolyte 25, the solid skin adhering to the cell container wall 26 which is cathodically connected. [074] In figure 6 and 7 are illustrated anodic systems composed of a plurality of anodes made of small and medium diameter pipes inside which the cooling fluid flows, wherein on the outside and in between the pipes, protected by the solid skin, the anodic gas easily evolves, without coalescing in large bubbles that station underneath the anodes.

Description of the Invention

[075] The electrode interphases include at one side the surface of the electronically conductive electrode material and at the other side the ionically conductive electrolyte layer. The energy changes in the anodic electrochemical process, have energy density distribution, at current densities of industrial interest, that cannot be significantly altered by external means. That is the fundamental reason why metal electrodes have difficulties in working as anodes for gas oxidation evolution. [076] One of the novel aspects of this invention is that the metal surface of the electrode material does not participate in the electrode interphase reaction mechanism, since it is replaced by an electric charge conducting solid layer on which the electrode half-reactions occur. That is the electric charge is transferred between the liquid electrolyte and the solid electrolyte layer. The underlaying metal material is only the electronic current conductor and it is not electrochemically working. [077] In the anodic and cathodic systems object of this invention, the usual mushy region between the solid and the liquid electrolyte behaves in a different mode because of the presence of the evolving anodic gas on the anodes and of the metals drops and particles being reduces on the cathodes.

[078] Another novel aspect of this invention is the horizontal configuration of the electrolysis apparatus characterized in that the cathodes are made of separate members and the reduced metal particles and drops fall through the members into a receiving region.

[079] The optimum thermal regime of the electrolytic metal producing cell is also controlled by the set value of the anode/cathode distance (ACD) that is, the thickness of the electrolyte between the cathode and the anodes through which the current passes generating resistance Joule heat. The larger the ACD, the higher the voltage drop of the electrolyte and the larger the resistance heat generated. [080] The rate of cooling of the electrodes determines the thickness of the solid skin adhering to the surface of the electrodes.

[081] The values of electrical resistivity of solid electrolytes at temperatures near their melting points are not very different from the values of electrical resistivity of the same electrolytes in their liquid state. For example the value for CaF2 solid/liquid is approximately 0.25 ohm-cm. Although the band gap of pure solid CaF2 is such that intrinsic electronic conduction is negligible, the operating conditions of the electrolytic cell are at temperatures greater that the transition to extrinsic conduction. Also the solid skin chemical composition, that is the solid in equilibrium with the liquid electrolyte composition, has effects on the electrical conduction of the solid skin. Furthermore, the structure of the solid skin is full of defects as it is continually created and destroyed upon the variation of the solid skin thickness. Certainly the electrical conduction mechanism of the solid skin is different from the electronic conduction in metals. The solid skin resistivity is also a function of the entrapped electrolyte constituents.

[082] At constant electrochemical regime conditions by varying the intensity of cooling of the anodes, the cell voltage changes with the variation of the thickness of the electrodes solid skin and of the electrode mushy region.

[083] The optimum combination of the ACD value and the electrodes skin thickness determines the best operating thermal regime conditions for the electrolytic cell producing metals.

[084] The procedure for cell start up operations with the anodes and cathodes object of this invention, will be easier than that for cermet inert anodes, since not only the anode are resistant to thermal shocks but they can contribute to the supply of thermal energy by circulating a fluid at high temperature within the cooling system of the anodes.

[085] In the case the electrodes system is cooled by air the internal surfaces are made oxidation resistant or are made of oxidation resistant materials.

[086] By operating the electrolytic cell as illustrated in this invention the production of aluminium and its alloys, of titanium and its alloys, and of other metals is obtained.

Example 1

[087] The electrolyte of a typical Hall-Heroult aluminium producing cell, is based on molten cryolite (Na3AlF6) which may contain a variety of additives such as LiF,

CaF2, MgF2 or A1F3, and contains dissolved high purity alumina (A12O3).

[088] The anodes are partially submerged in that highly corrosive electrolyte at the relatively high temperatures near 1'000⁰C needed to achieve a high alumina solubility.

[089] The anodes host the half-reaction of oxygen ion oxidation to neutral atoms, and the reaction of formation of an oxygen molecule from two of the newly formed oxygen atoms.

[090] The effect of the above conditions are intense at the high geometrical current densities used in operation, of the order of 1 Amp/cm2, since the effective current densities on the anode material is even higher because only between 30 and 70% of the anode surface is electrochemically working at any time, while the rest being covered by electrically insulating bubbles.

[091] The cooling fluid is a molten salt mixture 70 mol% NaBF4 and 30 mol% NaF.

[092] The anode material is Stainless steel.

[093] The shape the anodes are in the forms of array of separate pipes in order to favour anodic gas bubble release from the anodic surface. [094] The surface of the anodes has been treated before entering the electrolytic cell by controlled thermal or anodic oxidation.

[095] By installing in the electrolytic cell the anodes with their cooling system as described in this application, heat is extracted from the anodes surfaces and a thin layer of solid electrolyte is formed and maintained on the anode surface which, at the operating temperature is electrically conductive while at the same time is protecting the anode material from corrosion by the electrolyte and from erosion from the anodic gas evolution.

[096] The optimal setting of the anode/cathode distance and of the anode cooling intensity is achieved by monitoring the cell voltage and the electrolyte temperature.

Example 2

[097] The electrodes of a high temperature titanium electrowinning cell are made as described in the present invention for producing titanium and chlorine gas.

[098] By controlling the rate of cooling of the anodes, the cell using CaF2 based electrolyte grows and maintains a solid skin of about 0.5 mm which is electrically conductive and stable at the operation temperature to protect the underlaying anode material while introducing a minimal voltage drop

[099] The shape of the anodes is in the form of a block with sculptured bottom in order to favour chlorine bubble release from the anodic surface, and has an internal labyrinth for the circulation of the anode cooling fluid.

[100] The cooling fluid is a mixture of molten salt 70 mol% NaF and 30 mol%

NaBF4.

[101] The anode material is non-porous graphite and the cathode material is tungsten.

[102] The electrolytic optimal operating conditions are set as illustrated in the

Example 1.

[103] Having described the presently preferred embodiment it is to be understood that the invention may be otherwise embodied within the scope of the appended claims.

Example 3

[104] The electrolytic system as described in examples 1 and 2 characterized in that the electrolytic cell has a vertical geometrical configuration where the electrodes are vertically immersed in the electrolyte. The anodic gas evolves towards the surface of the electrolyte while the cathodic reduced metal drops and particle fall in the bottom of the cell.

Claims

1. An electrolysis apparatus for the production of metals comprising an anodic system of dimensionally stable anodes with their lower portion immersed in a liquid electrolytic bath, wherein a solid electrically conductive layer is maintained on the external surface of the anodes by providing cooling on the internal body of the anodes by using manifolds for the intake and exit of the cooling fluid.

2. An electrolysis apparatus for the production of metals comprising a cathodic system of dimensionally stable cathodes with their portion immersed in a liquid electrolyte bath, wherein a solid electrically conductive layer is maintained on the external surface of the cathodes by providing cooling on the internal body of the cathodes by using manifolds for intake and exit of the cooling fluid.

3. The electrolytic apparatus of claims 1 and 2 wherein the apparatus is an electrolytic cell used for the production of aluminium and aluminium alloys.

4. The electrolytic apparatus of claims 1 and 2 wherein the apparatus is an electrolytic cell used for the production of titanium and titanium alloys.

5. The electrolytic apparatus of claims 1 and 2 wherein the apparatus is an electrolytic cell used for the production of beryllium, chromium, cobalt, lead, lithium, magnesium, nickel, silicon, thorium, vanadium and zinc.

6. The electrolytic apparatus of claims 1 and 2 wherein the anodes and the cathodes are protected by a solid skin of the solidified electrolyte in which they are immersed.

7. The electrolytic apparatus of claims 1 and 2 wherein the anodes and the cathodes are made of metals, alloys, stainless steel, superalloys, carbon and other suitable materials.

8. The electrolytic apparatus of claims 1 and 2 wherein the anodes and the cathodes have their surfaces prepared and conditioned before being installed into the electrolytic cell, also in order to obtain a good electrical contact between the surface layer and the underlaying electrode material.

9. The electrolytic apparatus of claims 1 and 2 wherein the anodes and the cathodes have the solid layer pre-manufactured outside the electrolytic cell before being immersed in the electrolyte.

10. The electrolytic apparatus of claim 1 and 2 wherein the anodes and the cathodes have a solid surface layer that contains different kinds of impurities in order to increase the electrical conductivity of the layers, and to obtain photoassisted oxidation half-reactions on n-type doped the anodic layers and photoassisted reduction half-reactions on p-type doped cathodic layers,

11. The electrolysis apparatus of claim 1 and 2 wherein the applied electric potential on the electrolytic cell effects the accumulation of charges within the solid layers on the electrodes and gives them the electrical conduction degenerate metallic behaviour.

12. The electrolytic apparatus of claim 1 wherein the anode system has any physical design and shape for the anode of any geometrical configuration that favour anodic bubble release from the anode surface.

13. The electrolytic apparatus of claims 1 and 2 wherein the anode system and the cathode system have an internal labyrinth construction made of thermally insulating materials in order to extract heat only from the backside of the electrochemically active anodic and cathodic surfaces immersed in the electrolyte.

14. The electrolytic apparatus of claims 1 and 2 wherein the anodic surface layer and the cathodic surface layer have a thickness of between 0.001 and 30 mm and is controlled by regulating the intensity of the cooling while monitoring the electrochemical parameters of the cell.

15. The electrolytic apparatus of claims 1 and 2 wherein the anode system and the cathode system are protected by a solid layer that will not dissolve into the electrolyte and it is self-repairing in the event it is lost or damaged.

16. The electrolytic apparatus of claim 1 wherein the anode system is protected from corrosion and erosion by the anodic gas and the cell environment by the solid surface layer also on the upper portion above the level of the electrolyte by the condensed layer of the electrolyte vapour.

17. The electrolytic apparatus of claims 1 and 2 wherein the anode system and the cathode system are cooled by liquid metals, alloys, metal halides, molten salts mixtures, air, vapours and suitable gasses.

18. The electrolytic apparatus of claim 1 wherein the anode system comprises an array of separated pipes in such a way that the anodic gases evolve between the pipes.

19. The electrolytic apparatus of claim 2 wherein the cathode system comprises an array of separate members in such a way that the cathodic produced metal drops and particles fall between the cathodic members into a collecting region.

20. The electrolytic apparatus of claim 1 wherein the anode system is coupled with a drained cathode system.

21. The electrolytic apparatus of claims 1 and 2 characterized in that the anodes and the cathodes immersed in the electrolyte have a vertical configuration.