TWI849901B - Composite inert electrode, electrolyzer comprising the same and method of forming the same - Google Patents

Abstract

A composite inert electrode substantially consists of an electrode core and a carbonaceous coating covering the electrode core. The electrode core substantially consists of a ceramic material, and the carbonaceous coating includes a carbon-containing material. The carbonaceous coating is a non-intercalation electrode material and the robust metal is dispersed in the carbon-containing material.

Description

Composite inert electrode, electrolytic cell containing composite inert electrode, and method for forming composite inert electrode

The present invention relates to a composite inert electrode, an electrolytic cell containing the composite inert electrode, and a method for forming the composite inert electrode. In particular, the present invention is directed to a corrosion-resistant composite inert electrode for an electrolytic cell containing a corrosive electrolyte, and a method for forming the corrosion-resistant composite inert electrode.

In the field of chemical engineering, electrolysis is often used to carry out non-spontaneous chemical reactions for manufacturing or refining purposes. Electrolysis is usually carried out in an electrolytic cell, especially one containing a corrosive electrolyte.

However, corrosive electrolytes have the potential to damage the electrodes in the electrolytic cell. For example, during the electrolysis process, the electrode material will continue to wear out. Although the use of corrosion-resistant electrode materials can reduce the wear rate of electrode materials, due to their high prices, if expensive corrosion-resistant electrode materials are used in large quantities, the corresponding increase in manufacturing costs is still a technical problem to be solved.

In the search for other effective solutions, the industry needs a corrosion-resistant electrolytic electrode and its manufacturing method that is simple to manufacture, inexpensive, stable and reliable.

To achieve the above purpose, the inventor of this case has proposed a breakthrough composite inert electrode, an electrolytic cell containing a composite inert electrode, and a method for forming a composite inert electrode after exhaustive research and development. This breakthrough composite inert electrode is conducive to solving the aforementioned technical problems currently faced by the industry.

The present invention first proposes a composite inert electrode. The composite inert electrode is substantially composed of an electrode core and a carbon outer layer covering the electrode core. The electrode core is substantially composed of a ceramic material. The carbon outer layer is a composite material, substantially composed of a carbonaceous material and a corrosion-resistant metal. The carbon outer layer is a non-intercalation electrode material, and the corrosion-resistant metals are dispersed in the carbonaceous material in a manner separated from each other. The carbon outer layer is electrically conductive, and its resistivity is, for example, less than 1X10 ^-3 Ω. m.

The present invention secondly proposes an electrolytic cell. The electrolytic cell comprises an electrolyte and the aforementioned composite inert electrode. The electrolyte comprises at least one of a strong acid, a strong base and a fluoride. The carbon outer layer in the composite inert electrode directly contacts the electrolyte to isolate the electrolyte from contacting the electrode core.

The present invention can also provide a method for forming a composite inert electrode. First, an electrode core is provided. The electrode core is substantially composed of a ceramic material. Second, an electroplating deposition reaction is performed in the presence of a carbon source precursor to form a carbon outer layer covering the electrode core. The carbon outer layer is substantially composed of a carbon-containing material and a corrosion-resistant metal. The carbon outer layer is a non-insertion type electrode material, and the corrosion-resistant metal is dispersed in the carbon-containing material.

The composite inert electrode proposed by the present invention does not require a large amount of expensive corrosion-resistant electrode materials, so the material cost of the composite inert electrode of the present invention can be significantly reduced. The method for forming the composite inert electrode proposed by the present invention can further reduce the manufacturing cost of the composite inert electrode because of its simple manufacturing method. In addition, the carbonaceous outer layer produced by the method for forming the composite inert electrode of the present invention is a non-insertion type electrode material. This non-insertion type electrode material will not undergo an insertion reaction with metals or ions to produce an intercalation compound or an intercalation complex. Therefore, the chemical reaction between the electrode and the electrolyte in the electrolysis reaction can also be simplified. In addition, the carbon outer layer is a composite material, including a carbon-containing material and a corrosion-resistant metal dispersed therein, and the corrosion-resistant metal can also increase the service life of the carbon outer layer. In addition, the electrode core is a ceramic material, which has good support, is not easy to wear, and has low cost. Therefore, the composite inert electrode, electrolytic cell and method of forming the composite inert electrode in this case are nothing less than a comprehensive technical solution that can demonstrate multiple invention advantages.

10: Electroplating tank

11: Plating solution

12: Sacrifice the electrode

13:Carbon source precursor

100: Composite inert electrode

101: Composite inert electrode

110: Electrode core

110A: Surface

111: The first corrosion-resistant metal

112: The second most corrosion-resistant metal

113: The third corrosion-resistant metal

120: Carbon outer layer

121: Carbon-containing materials

123: Alloy

200:Electrolyzer

210:Electrolyte

220: Power structure

FIG1 is a schematic diagram showing the process of forming a composite inert electrode according to an embodiment of the present invention.

Figures 2 to 4 are schematic diagrams showing a method for forming a composite inert electrode according to an embodiment of the present invention.

Figures 3 and 4 are schematic diagrams of an electrodeless electroplating deposition method for forming a composite inert electrode according to an embodiment of the present invention.

Figures 3 and 4 are schematic diagrams of an electrode electroplating deposition method for forming a composite inert electrode according to an embodiment of the present invention.

Figures 5 and 6 are schematic diagrams showing a method for regenerating a composite inert electrode according to an embodiment of the present invention.

Figures 7 to 9 show schematic cross-sectional views of a composite inert electrode according to an embodiment of the present invention.

Figure 10 shows a schematic diagram of the cross-sectional structure of a composite inert electrode used in an electrolytic cell according to an embodiment of the present invention.

In order to enable a person skilled in the art who is familiar with the technical field to which the present invention belongs to further understand the present invention, several preferred embodiments of the present invention are listed below, and the components and intended effects of the present invention are described in detail with the accompanying drawings. Moreover, a person skilled in the art who is familiar with the technical field to which the present invention belongs can also refer to the following embodiments without departing from the spirit of the present invention, and replace, reorganize, and mix the features in several different embodiments to complete other embodiments.

In the following description and patent application, the words "contain" and "include" are open-ended words, and therefore should be interpreted as "contains but is not limited to..." In the following description and patent application, "substantially composed of certain elements" or similar words are semi-closed words, which means that in the combination of elements, components or steps, the elements, components or steps recorded in the description and substantially do not affect the elements, components or steps recorded in the claim are not excluded. For example, but not limited to, impurities, impurities, contaminants, or possible additives and protozoa that are difficult to completely exclude in practice do not exclude the elements, components or steps that are not recorded in the description and substantially do not affect the main technical features of the invention of the patent application.

The terms "approximately", "equal to", "equal to" or "same", "substantially" or "approximately" are generally interpreted as being within a range of plus or minus 20% of a given value, or within a range of plus or minus 10%, plus or minus 5%, plus or minus 3%, plus or minus 2%, plus or minus 1% or plus or minus 0.5% of a given value. In addition, the terms "a given range is from a first value to a second value", "a given range falls within the range from a first value to a second value" indicate that the given range includes the first value, the second value and other values therebetween.

Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. It is understood that these terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with the background or context of the relevant technology and the present invention, and should not be interpreted in an idealized or overly formal manner unless specifically defined in the embodiments of the present invention.

FIG. 1 is a schematic diagram of a process of forming a composite inert electrode according to an embodiment of the present invention. FIG. 2 to FIG. 4 are schematic diagrams of a method of forming a composite inert electrode by electroplating according to an embodiment of the present invention. As shown in FIG. 2 , in the method of forming a composite inert electrode shown in FIG. 2 , an electroplating chamber 10 is first provided. The electroplating chamber 10 contains an electroplating solution 11, which can be used to form a passivation protective layer on the surface of a substrate to protect the substrate inside. Next, a substrate is provided and placed in the electroplating chamber 10. In one embodiment, as shown in FIG. 3 , the substrate can be an electrode core 110 of the composite inert electrode of the present invention. The electrode core 110 is substantially composed of a ceramic material. For example, an electrode core 110 substantially composed of a ceramic material is provided, and the electrode core 110 is placed in the electroplating tank 10.

In one embodiment, the ceramic material refers to a material other than an organic material and a metal material, such as an inorganic non-metallic material. The ceramic material may be a mixture formed by sintering silicon oxide and/or metal oxide, with inorganic nitrides, inorganic borides and inorganic carbides added as needed. According to one embodiment, the Mohs hardness of the ceramic material is higher than 6.5.

As shown in FIG3 , the electroplating solution 11 contains stable ions of the corrosion-resistant metal, such as dissociation ions of the corrosion-resistant metal, so that the corrosion-resistant metal is dissolved in the dissociation ions and exists stably in the electroplating solution 11. The ligands and dissociation ions of various corrosion-resistant metals suitable for electroplating are well known in the art, so they are not described in detail. If necessary, a sacrificial electrode 12 containing the corrosion-resistant metal can be provided in the electroplating solution 11. By providing a sacrificial electrode 12 of corrosion-resistant metal and replacing it with a new sacrificial electrode 12, the sacrificial electrode 12 can continuously provide ions and dissociations of the corrosion-resistant metal in the electroplating solution 11, so that the concentration of ions and dissociations of the corrosion-resistant metal in the electroplating tank 10 can be maintained at a constant concentration. In addition, the carbon source precursor 13 is introduced into the electroplating tank 10 and dispersed in the electroplating solution 11. By continuously adding the carbon source precursor 13, the concentration of the carbon source precursor 13 in the electroplating tank 10 can be maintained at a constant concentration.

Then, please refer to FIG. 4 , in the presence of the carbon source precursor 13, the surface 110A of the electrode core 110 is subjected to a predetermined electroplating deposition reaction. Alternatively, as shown in FIG. 4 , in the presence of the carbon source precursor 13, a suitable voltage is provided to the electrode core 110 and the sacrificial electrode 12 in series, and a predetermined electroplating deposition reaction is performed on the surface 110A of the electrode core 110. The predetermined electroplating deposition reaction can be carried out in the presence of the ions of the corrosion-resistant metal in the electroplating solution 11, so that the reduced carbon source precursor 13 and the first corrosion-resistant metal 111 obtained by the ions of the corrosion-resistant metal directly form a carbon outer layer 120 on the surface 110A of the electrode core 110 that completely covers the electrode core 110, thereby obtaining the composite inert electrode 100 of the present invention and forming a protective effect on the electrode core 110, and there is no need to use an additional binder to assist in forming the carbon outer layer 120 on the surface 110A of the electrode core 110. The thickness of the carbon outer layer 120 can range from a few nanometers to a few micrometers as required. Therefore, compared with the electrode core 110, the thickness of the carbon outer layer 120 is much smaller than the thickness of the electrode core 110. According to one embodiment, the Mohs hardness of the carbon outer layer 120 is smaller than the Mohs hardness of the electrode core 110.

Graphite is an effective inert material, and the graphite material can be a continuous layer that completely covers the electrode core 110. In one embodiment, the carbonaceous outer layer 120 includes a carbonaceous material 121, such as a carbon material. In another embodiment, the carbonaceous outer layer 120 is substantially composed of the carbonaceous material 121 and the first corrosion-resistant metal 111, wherein the carbonaceous outer layer 120 is a non-insertion type electrode material. The carbonaceous outer layer 120 is electrically conductive, and its resistivity is, for example, less than ^1X10-3 Ω.m. Because of the presence of the ions of the corrosion-resistant metal in the electroplating solution 11, the first corrosion-resistant metal 111 is dispersed in the carbonaceous material 121, or the carbonaceous material 121 is dispersed in the first corrosion-resistant metal 111, so that the two together form the carbonaceous outer layer 120. In another embodiment, a portion of the first corrosion-resistant metal 111 and a portion of the carbon-containing material 121 form an alloy 123 .

The carbon-containing material 121 includes, for example, a graphite-based carbon material. The graphite-based carbon material includes, for example, at least one of graphite, graphene, reduced graphene oxide, and graphene oxide. An appropriate carbon source precursor 13, such as at least one of graphite, graphene, reduced graphene oxide, and graphene oxide, can be reduced on the surface 110A of the electrode core 110 under the conditions of an electroplating deposition reaction to form the carbon-containing material 121 that covers the electrode core 110. The electroplating deposition reaction is a non-spontaneous oxidation-reduction reaction in the presence of an externally provided voltage and current. According to one embodiment, the electrode plating solution may include a carbon source precursor (for example), a metal salt (for example, a nickel salt), an additive (for example, boric acid), and/or a dispersant, but is not limited thereto.

In one embodiment, the corrosion-resistant metal may be a passive metal or a corrosion-resistant metal material, such as a group consisting of ruthenium, rhodium, palladium, silver, nimium, iridium, platinum, gold, nickel, tantalum, niobium, zirconium, and titanium, or an alloy thereof, but not limited thereto. The passive metal material or the corrosion-resistant metal material may refer to a metal material or an alloy that is chemically stable to at least one of a strong acid, a strong base, and a halide. Corrosion resistance may refer to a chemically passive metal material whose thickness change value is less than or equal to 1 nanometer (nm) per minute under certain corrosion conditions. The strong acid may be, for example, perchloric acid, chloric acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, or a mixture thereof, but not limited thereto. Strong bases may be, for example, organic quaternary ammonium bases such as sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, or mixtures thereof, but are not limited thereto. Halides may be, for example, fluorides, fluoride salts, hydrogen fluoride, hydrofluoric acid, aqua regia, or mixtures thereof, but are not limited thereto. For example, niobium can resist corrosion by molten alkali, aqua regia, hydrochloric acid, sulfuric acid, nitric acid, or phosphoric acid. Silver, platinum, gold, or nickel (including nickel alloys) can resist corrosion by hydrogen fluoride or hydrofluoric acid.

In one embodiment, the carbonaceous outer layer 120 formed by the electroplating deposition reaction of the present invention can be a passive thin-layer carbonaceous material, and its thickness is, for example, 1 μm to 5 mm, but is not limited thereto. For example, the carbonaceous outer layer 120 can be a non-insertion type thin-layer conductive electrode material. Such passive carbonaceous material is passive to metals or ions, and will not undergo a known insertion reaction with metals or ions to produce a corresponding intercalation compound or intercalation complex. Therefore, the carbon outer layer 120 of the present invention can also simplify the chemical reaction between the electrode and the electrolyte in the electrolysis reaction of the composite inert electrode of the present invention, avoid the electrode core 110 being consumed by the electrolyte, or reduce the rate at which the electrode core 110 is consumed by the electrolyte, which is one of the technical features of the method for forming the composite inert electrode of the present invention. In addition, since the carbon outer layer is a composite material, which includes a carbon-containing material and a corrosion-resistant metal dispersed therein, the carbon outer layer of the present case including the corrosion-resistant metal has a longer service life compared to the carbon outer layer only including the carbon-containing material.

Please refer to Figures 5 and 6, which are schematic diagrams of a method for regenerating a composite inert electrode according to an embodiment of the present invention. The conductive carbon outer layer 120 covering the electrode core 110 may age after use, which may affect the long-term performance of the composite inert electrode 100. The present invention can regenerate an aged composite inert electrode 100 through a simple method. Please refer to Figure 5, first, a composite inert electrode 100 having an aged conductive carbon outer layer 120 is provided. If necessary, a simple method can be used to remove the aged conductive carbon outer layer 120, such as a heating process to oxidize the aged conductive carbon outer layer 120, or a grinding process to grind away the aged conductive carbon outer layer 120, and completely remove the aged conductive carbon outer layer 120, but not limited to this. Compared with nickel metal or other metals that can be used as electrolytic electrodes, ceramic materials are particularly suitable for regenerating the aged composite inert electrode 100 by the method of thermal stripping because of their high heat resistance and mechanical strength.

Afterwards, please refer to FIG. 6 , the aforementioned electrode electroplating deposition method can be used again to regenerate a conductive carbon outer layer 120 on the surface 110A of the electrode core 110 to obtain the regenerated composite inert electrode 101 of the present invention, so that the composite inert electrode 101 provided by the present invention becomes a composite electrode that is easy to regenerate (re-rejuvenate) its corrosion resistance effect and restore its long-term performance. By stripping off the overused and aged conductive carbon outer layer 120 and regenerating a cheap conductive carbon outer layer 120, the maintenance cost of the composite inert electrode 100 provided by the present invention can be reduced.

After the above-mentioned method of forming a composite inert electrode, a composite inert electrode 100 provided by the present invention can be obtained. Please refer to Figures 7 to 9, which show schematic diagrams of the cross-sectional structure of a composite inert electrode 100 of an embodiment of the present invention. A composite inert electrode 100 provided by the present invention is substantially composed of an electrode core 110 and a carbonaceous outer layer 120. The carbonaceous outer layer 120 covers the electrode core 110. In one embodiment, the carbonaceous outer layer 120 is substantially composed of a carbonaceous material 121 and a first corrosion-resistant metal 111, wherein the carbonaceous outer layer 120 is a non-insertion type electrode material, and the first corrosion-resistant metal 111 is dispersed in the carbonaceous material 121 to form the carbonaceous outer layer 120. In another embodiment, part of the first corrosion-resistant metal 111 and part of the carbonaceous material 121 form an alloy 123. In a preferred embodiment, the carbon outer layer 120 directly and completely covers the electrode core 110.

In one embodiment, the electrode core 110 is substantially composed of a ceramic material. Please refer to the above for details of the ceramic material and the corrosion-resistant metal, so it will not be repeated. Depending on the situation, the electrode core 110 can be a single-layer structure, a double-layer structure, or a multi-layer composite structure. FIG. 7 shows a cross-sectional structure schematic diagram of a composite inert electrode 100 of a single-layer electrode core 110 of an embodiment of the present invention. The single-layer electrode core 110 can be substantially composed of a single corrosion-resistant metal, such as substantially composed of nickel, but is not limited thereto.

In another embodiment, the double-layer structured electrode core 110 may be substantially composed of a first corrosion-resistant metal 111 with a smaller outer layer thickness and a second corrosion-resistant metal 112 with a larger inner layer thickness. FIG8 shows a cross-sectional structure diagram of a composite inert electrode 100 of a double-layer structured electrode core 110 of an embodiment of the present invention. The inner layer of the second corrosion-resistant metal 112 may be lower in price than the outer layer of the first corrosion-resistant metal 111, which is beneficial to reduce the raw material cost of the electrode core 110. For example, the double-layer structured electrode core 110 may be substantially composed of an outer layer of gold encapsulating an inner layer of nickel, or substantially composed of an outer layer of silver encapsulating an inner layer of titanium, but is not limited thereto.

In another embodiment, the electrode core 110 of the multi-layer structure may be substantially composed of a first corrosion-resistant metal 111 with a smaller outer layer thickness wrapping a second corrosion-resistant metal 112 in the middle layer, and then the second corrosion-resistant metal 112 in the middle layer wrapping a third corrosion-resistant metal 113 with a larger inner layer thickness, and so on to form a composite electrode core structure of three or more layers. FIG9 shows a cross-sectional structure schematic diagram of a composite inert electrode 100 of an electrode core 110 of a three-layer structure of an embodiment of the present invention. For example, the three-layer structure of the electrode core 110 may be substantially composed of an outer layer of gold wrapped in a middle layer of silver, and then the middle layer of silver wrapped in an inner layer of nickel, which is beneficial for achieving a balance between reducing the raw material cost of the electrode core 110 and extending the service life of the composite inert electrode 100, but is not limited thereto.

In one embodiment, the carbonaceous outer layer 120 includes a carbonaceous material. The carbonaceous material includes at least one of graphene, reduced graphene oxide, and graphene oxide. In another embodiment, the carbonaceous outer layer 120 may further include the aforementioned corrosion-resistant metal. For example, the carbonaceous outer layer 120 may include a mixture or a compound of the aforementioned corrosion-resistant metal and the carbonaceous material. The mixture may be an alloy-like structure or a binary material in which layered graphite is dispersed in the corrosion-resistant metal. The compound may be a compound of a corrosion-resistant metal and carbon. In particular, the carbonaceous outer layer 120 formed by the electrode electroplating deposition method or the electrodeless electroplating deposition method of the present invention may be a passive carbonaceous material. For example, the carbonaceous outer layer 120 may be a non-insertion type electrode material, which is not suitable for use in primary batteries or secondary batteries. This passive carbon-containing material is passive to metals or ions and will not undergo the known insertion reaction with metals or ions to produce corresponding intercalation compounds or intercalation complexes. This is one of the technical features of the composite inert electrode method of the present invention.

Compared with a simple graphite electrode, the composite inert electrode 100 of the present invention still retains the advantages of the electrode core 110 made of metal material. For example, a simple method can be used to remove the used and aged conductive carbon outer layer 120 without damaging the electrode core 110 made of ceramic material. In addition, the composite inert electrode 100 of the present invention can regenerate a conductive carbon outer layer 120 on the surface 110A of the electrode core 110 after removing the used and aged conductive carbon outer layer 120, thereby obtaining the regenerated composite inert electrode 101 of the present invention, making the composite inert electrode 100 provided by the present invention a composite electrode that is easy to regenerate and maintain.

A composite inert electrode 100 provided by the present invention can be used in an electrochemical device, for example, in an electrolytic cell. Please refer to FIG. 10 , which shows a schematic diagram of the cross-sectional structure of an electrolytic cell including a composite inert electrode 100 according to an embodiment of the present invention. The electrolytic cell 200 provided by the present invention comprises an electrolyte 210, a power source structure 220, and at least one composite inert electrode 100 as described above (for example, two composite inert electrodes 100). The electrolyte 210 can be a chemical solution containing at least one electrolyte. The electrolyte 210 can, for example, contain at least one of a strong acid, a strong base, and a fluoride. In one embodiment, the strong acid can be, for example, perchloric acid, chloric acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, or a mixture thereof, but is not limited thereto. The strong base may be, for example, an organic quaternary ammonium base such as sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, or a mixture thereof, but is not limited thereto. The halides may be, for example, fluorides, fluoride salts, hydrogen fluoride, hydrofluoric acid, aqua regia, or a mixture thereof, but is not limited thereto.

The power source structure 220 can provide the composite inert electrode 100 with appropriate voltage and current to perform a predetermined electrolytic reaction. The composite inert electrode 100 will perform a predetermined electrolytic reaction when immersed in the electrolyte 210 under appropriate voltage conditions, current conditions, and temperature conditions. In one embodiment, the carbon outer layer 120 directly contacts the electrolyte 210 to isolate the electrolyte 210 from contacting the electrode core 110 and reduce the possibility of damage to the electrode core 110, and form a protective layer to extend the service life of the composite inert electrode 100. The composite inert electrode 100 is essentially composed of the electrode core 110 and the carbon outer layer 120. Please refer to the above for details of the carbon outer layer 120 and the electrode core 110, so it will not be repeated. In a preferred embodiment, the carbon outer layer 120 can be a non-insertion type electrode material, which is one of the technical features of the electrolytic cell 200 of the present invention.

During the electrolysis process, one (or some) of the composite inert electrodes 100 is configured to receive a positive voltage from the power structure 220, and another (or some) of the composite inert electrodes 100 is configured to receive a negative voltage from the power structure 220. By applying positive voltage and negative voltage to the composite inert electrode 100, respectively, the electrolyte 210 will undergo an electrolysis reaction to generate corrosive gas and/or flammable gas. According to one embodiment, the composite inert electrode 100 as an anode will generate a corrosive gas, such as fluorine-containing nitride, and the composite inert electrode 100 as a cathode will generate a flammable gas, such as hydrogen, but it is not limited thereto.

The above is only the preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the patent application of the present invention shall fall within the scope of the present invention.

10: Electroplating tank

11: Plating solution

13:Carbon source precursor

100: Composite inert electrode

110: Electrode core

110A: Surface

111: The first corrosion-resistant metal

120: Carbon outer layer

121: Carbon-containing materials

123: Alloy

Claims (9)

A composite inert electrode is substantially composed of an electrode core and a carbon outer layer covering the electrode core, wherein: the electrode core is substantially composed of a ceramic material; and the carbon outer layer is substantially composed of a carbon-containing material and a corrosion-resistant metal, wherein the carbon outer layer is a non-intercalation electrode material, and the carbon-containing material includes at least one of carbon, graphene, reduced graphene oxide and graphene oxide, and the corrosion-resistant metal is dispersed in the carbon-containing material. The composite inert electrode as described in item 1 of the patent application, wherein the corrosion-resistant metal is selected from a group consisting of ruthenium metal, rhodium metal, palladium metal, silver metal, nimum metal, iridium metal, platinum metal, gold, nickel metal, tantalum metal, and titanium metal. The composite inert electrode as described in Item 1 of the patent application, wherein the corrosion-resistant metal and the carbon-containing material form an alloy. The composite inert electrode as described in item 1 of the patent application, wherein the carbon outer layer directly and integrally covers the electrode core. The composite inert electrode as described in item 1 of the patent application, wherein the carbon outer layer is a composite layer covering the electrode core. An electrolytic cell comprising: an electrolyte comprising at least one of a strong acid, a strong base and a fluoride; and the composite inert electrode as described in item 1 of the patent application, wherein the carbon outer layer directly contacts the electrolyte to isolate the electrolyte from contacting the electrode core. An electrolytic cell as described in Item 6 of the patent application, wherein the number of the composite inert electrodes is greater than 1, and some of the composite inert electrodes are configured to receive a positive voltage, and the other composite inert electrodes are configured to receive a negative voltage. A method for forming a composite inert electrode comprises: providing an electrode core, wherein the electrode core is substantially composed of a ceramic material; and performing an electroplating deposition reaction in the presence of a carbon source material to form a carbon outer layer covering the electrode core, wherein the carbon outer layer is substantially composed of a carbon-containing material and a corrosion-resistant metal, the carbon outer layer is a non-insertion type electrode material, and the corrosion-resistant metal is dispersed in the carbon-containing material. A method for forming a composite inert electrode as described in claim 8, wherein the Mohs hardness of the ceramic material is higher than the Mohs hardness of the carbonaceous outer layer.

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