Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/02—Hydrogen or oxygen
  • C25B1/04—Hydrogen or oxygen by electrolysis of water
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/052—Electrodes comprising one or more electrocatalytic coatings on a substrate
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/054—Electrodes comprising electrocatalysts supported on a carrier
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
  • C25B11/059—Silicon
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
  • C25B11/061—Metal or alloy
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
  • C25B11/061—Metal or alloy
  • C25B11/063—Valve metal, e.g. titanium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
  • C25B11/065—Carbon
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/10—Process efficiency
  • Y02P20/133—Renewable energy sources, e.g. sunlight

Definitions

• the present invention relates to the field of electrodes suitable for use for electrochemical reduction reactions, in particular for the electrolysis of water in a liquid electrolytic medium in order to produce hydrogen.
• the hydrogen evolution reaction occurs at the cathode and the oxygen evolution reaction (OER) occurs at the anode.
• the overall reaction is:
• Electrolysis of water is an electrolytic process that breaks down water into O2 and H2 gas with the help of an electric current.
• the electrolytic cell consists of two electrodes - usually in inert metal (in the potential and pH zone considered) such as platinum - immersed in an electrolyte (here water itself) and connected to the opposite poles of the source of direct current.
• the electric current dissociates the water molecule (H2O) into hydroxide (HO-) and hydrogen H + ions: in the electrolytic cell, the hydrogen ions accept electrons at the cathode in an oxidation-reduction reaction, forming gaseous hydrogen ( H2), depending on the reduction reaction:
• dichalcogenides such as molybdenum sulphide M0S 2 are very promising materials for the hydrogen evolution reaction (HER) due to their high activity, excellent stability and availability, the molybdenum and sulfur being abundant elements on earth and at low cost.
• Materials based on MOS 2 have a lamellar structure and can be promoted by Ni or Co in order to increase their electrocatalytic activity.
• the active phases can be used in bulk form when the conduction of electrons from the cathode is sufficient or else in the supported state, then bringing into play a support of a different nature. In the latter case, the support must have specific properties:
• Carbon is the most common medium used in this application.
• the challenge lies in the preparation of this sulphide phase on the conductive material.
• a catalyst exhibiting a high catalytic potential is characterized by an associated active phase perfectly dispersed on the surface of the support and exhibiting a high active phase content. It should also be noted that, ideally, the catalyst should have accessibility to the active sites with respect to the reactants, here water, while developing a high active surface area, which can lead to specific constraints in terms of structure and texture, specific to the support constituting said catalysts.
• the usual methods leading to the formation of the active phase of catalytic materials for the electrolysis of water consist of a deposit of precursor (s) comprising at least one metal from group VI B, and optionally at least one metal from group VIII using an impregnation solution, on a support by the technique known as "dry impregnation” or by the technique known as “excess impregnation”, followed by at least one possible heat treatment to evacuate water and a final sulphurization step generating the active phase, as mentioned above.
• the prior art shows that researchers have turned to several methods, including the deposition of Mo precursors in the form of ammonium salts or oxides or heptamolybdate followed by a sulfurization step in the gas phase or in the presence of a chemical reducing agent.
• Kibsgaard et al Engineering the surface structure of MoS2 to preferentiaiiy exposes active edge sites for eiectrocataiysis ", 2012, propose to electrodeposit Mo on an Si support from a solution of peroxopolymolybdate then to carry out a sulfurization step at 200 ° C under a mixture of gases H2S / H2 ratio 10/90. Bonde et al.
• impregnation in a molten medium consists in mixing a porous support with a solid metal salt having a relatively low melting point, in particular lower than its decomposition temperature, then heating the mixture to a temperature higher than the melting temperature of said metal salt in order to melt the salt in the support.
• This technique thus differs from conventional impregnation by several advantages, in particular by simplified preparation. Indeed, it does not require preparation of solution or solvent because the metal precursors are used in the form of solids. Likewise, the catalytic material obtained after heating the solid support / salt mixture does not need additional drying steps. In addition, a major advantage of impregnation in a molten medium is the fact that a catalytic material with a very high metal content can be obtained in a single step.
• this technique has the disadvantage of requiring a metal salt having a relatively low melting point, in particular lower than its decomposition temperature.
• a metal salt having a relatively low melting point in particular lower than its decomposition temperature.
• such salts exist for the metals of group VIII, in particular as a hydrated nitrate salt based on nickel or cobalt, there does not appear to be any Group VIB salts which meet these low melting point criteria. Indeed, salts based on a metal of group VIB tend to decompose before reaching their melting point.
• one of the objectives of the present invention is to provide a process for preparing a catalytic material of an electrode for electrochemical reduction reactions based on a group VIB metal prepared by impregnation in a molten medium.
• the first subject of the present invention is a process for preparing a catalytic material of an electrode for electrochemical reduction reactions, said material comprising an active phase based on at least one metal from group VIB and an electrically conductive support.
• the metal content of group VIB being between 4 and 70% by weight expressed as metal element of group VIB relative to the total weight of the catalytic material
• said process comprising the following steps: a) water is brought into contact with said electrically conductive support so as to obtain a wet electrically conductive support, b) said wet electrically conductive support is brought into contact with at least one hydrated metal acid comprising at least one metal from group VIB, the melting point of which of said acid hydrated metal is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said metallic acid and said electrically conductive support being between 0.1 and 4, c) the solid mixture obtained at the end of step b) is heated with stirring to a temperature between the melting point of said hydrated metal acid and 100 ° C., d)
• the Applicant has developed a new process for preparing a catalytic material making it possible to obtain an electrode which can be used in an electrolytic cell for carrying out an electrochemical reduction reaction, and more particularly which makes it possible to obtain a cathode which can be used in an electrolytic cell. for the production of hydrogen by electrolysis of water.
• the Applicant has in fact observed that the use of hydrated metal acid comprising at least one metal from group VIB and having a melting point of between 20 and 100 ° C makes it possible to introduce a metal from group VIB into an electro-electro support. conductive by impregnation in a molten medium. This makes it possible to obtain a catalytic material having catalytic performance at least as good, or even better, than a catalytic material prepared by impregnation using an impregnation solution, however with a simplified preparation and the possibility of loading more. group VIB metal.
• the hydrated metallic acid which is in powder form, is mixed with the electrically conductive support (step b), then this solid mixture is heated in order to melt the metallic acid in the support, thus making it possible to obtain the material from step c) which is subsequently subjected to a sulfurization step (step d).
• the acid has the peculiarity of only melting in the presence of sufficient partial pressure of water. In other words, it is necessary to keep the molecules of water of crystallization to ensure its fusion.
• the support is first moistened by impregnating with water (step a).
• the preparation process according to the invention thus has the advantages of an impregnation in a molten medium, in particular the absence of any preparation of solution or the use of solvent and the absence of the need for subsequent drying even if a such step is possible.
• the preparation process according to the invention makes it possible to obtain a catalytic material heavily loaded with metal from group VIB having in particular contents of metal from group VIB which are not achievable by impregnation using a solution of 'impregnation.
• the hydrated metal acid is chosen from hydrated phosphomolybdic acid, hydrated silicomolybdic acid, hydrated molybdosilicic acid, hydrated phosphotungstic acid and hydrated silicotungstic acid.
• the electrically conductive support comprises at least one material chosen from carbon structures of the carbon black type, graphite, carbon nanotubes or graphene.
• the electrically conductive support comprises at least one material selected from gold, copper, silver, titanium, silicon.
• step b) further comprises bringing into contact with at least one metal salt comprising at least one metal from group VIII, the melting point of said metal salt of which is between 20 and 100 ° C, to form a solid mixture, the molar ratio (metal of group VIII) / (metal of group VIB) being between 0.1 and 0.8.
• said metal salt is a hydrated nitrate salt or a hydrated sulfate salt.
• said metal salt is chosen from nickel nitrate hexahydrate, cobalt nitrate hexahydrate, iron nitrate nonahydrate, nickel sulfate hexahydrate, cobalt sulfate heptahydrate, iron sulfate heptahydrate, taken alone or as a mixture. .
• step b) further comprises bringing into contact with phosphoric acid, to form a solid mixture, the phosphorus / (metal from group VIB) molar ratio being between 0 , 08 and 1.
• step b) further comprises bringing into contact with an organic compound comprising oxygen and / or nitrogen and / or sulfur, the melting point of said compound of which organic is between 20 and 100 ° C, the organic compound / metal of group VIB molar ratio being between 0.01 and 5.
• the organic compound is chosen from maleic acid, sorbitol, xylitol, g-ketovaleric acid, 5-hydroxymethylfurfural and 1, 3-dimethyl-2-imidazolidinone.
• an impregnation step is carried out using an impregnation solution and in which said support is brought into contact.
• the organic compound is chosen from y-valerolactone, 2-acetylbutyrolactone, triethylene glycol, diethylene glycol, ethylene glycol, ethylenediaminetetra-acetic acid (EDTA), maleic acid, malonic acid, l citric acid, gluconic acid, dimethyl succinate, glucose, fructose, sucrose, sorbitol, xylitol, ⁇ -ketovaleric acid, dimethylformamide, 1-methyl-2-pyrrolidinone, carbonate propylene, 2-methoxyethyl 3-oxobutanoate, bicine, tricine, 2-furaldehyde (also known as furfural), 5- hydroxymethylfurfural (also known as 5- (hydroxymethyl) -2-furaldehyde or 5- HMF), 2-acetylfuran, 5-methyl-2-furaldehyde, ascorbic acid, butyl lactate, ethyl 3-hydroxybutanoate, ethyl
• the sulfurization temperature in step d) is between 350 ° C. and 550 ° C. In one embodiment according to the invention, when the precursor of the catalytic material comprises only a metal from group VI B, the sulfurization temperature in step d) is between 100 ° C and 250 ° C or between 400 ° C. and 600 ° C.
• At least one ionically conductive polymeric binder is dissolved in a solvent or a mixture of solvents
• step 1) at least one catalytic material prepared according to the invention, in powder form, is added to the solution obtained in step 1) to obtain a mixture; steps 1) and 2) being carried out in any order, or simultaneously;
• step 2) the mixture obtained in step 2) is deposited on a metallic or metallic-type conductive support or collector.
• Another object according to the invention relates to an electrolysis device comprising an anode, a cathode, an electrolyte, said device being characterized in that at least one of the anode or of the cathode is an electrode according to the invention. .
• Another object according to the invention relates to the use of the electrolysis device according to the invention in electrochemical reactions.
• group VIII according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUPAC classification.
• BET surface is meant the specific surface determined by nitrogen adsorption in accordance with standard ASTM D 3663-78 established from the BRU N AU ER - EM MET - TELLER method described in the periodical "The journal of the American Chemical Society ", 60, 309 (1938).
• the first subject of the present invention is a process for preparing a catalytic material of an electrode for electrochemical reduction reactions, said material comprising an active phase based on at least one metal from group VIB and an electrically conductive support.
• the metal content of group VIB being between 4 and 70% by weight expressed as metal element of group VIB relative to the total weight of the catalytic material
• said process comprising the following steps: a) water is brought into contact with said electrically conductive support so as to obtain a wet electrically conductive support, b) said wet electrically conductive support is brought into contact with at least one hydrated metal acid comprising at least one metal from group VIB, the melting point of which of said acid hydrated metal is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said metallic acid and said electrically conductive support being between 0.1 and 4, c) the solid mixture obtained at the end of step b) is heated with stirring to a temperature between the melting point of said hydrated metal acid and 100 ° C., d)
• step a) of the preparation process according to the invention water is brought into contact with said electrically conductive support so as to obtain a wet electrically conductive support.
• This step of humidifying the electrically conductive support is necessary in order to be able to melt the hydrated metal acid in step c).
• the acid has the particularity of melting only in the presence of a sufficient partial pressure of water. In other words, it is necessary to keep the water molecules of crystallization of the metallic acid hydrated to ensure its fusion.
• Contacting step a) can be carried out by dry impregnation.
• the water can for example be poured drop by drop onto the support contained in a rotating bezel.
• the quantity of water introduced into the porous support is between 10 and 70%, and preferably between 30 and 50% of its water uptake volume.
• the wet electrically conductive support is allowed to mature. Maturation allows the water to disperse homogeneously within the electrically conductive medium.
• Any maturation step is advantageously carried out at atmospheric pressure, in an atmosphere saturated with water and at a temperature between 17 ° C and 50 ° C, and preferably at room temperature.
• a maturation time of between ten minutes and forty-eight hours, preferably between thirty minutes and fifteen hours and particularly preferably between thirty minutes and six hours, is sufficient.
• step b) of the preparation process according to the invention said wetted electrically conductive support is brought into contact with at least one hydrated metal acid comprising at least one metal from group VI B whose melting point of said hydrated metal acid is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said metallic acid and said electrically conductive support being between 0.1 and 4.
• the hydrated metal acid must have a relatively low melting point, especially lower than its decomposition temperature.
• the melting point of hydrated metal acid is between 20 and 100 ° C, and preferably between 50 and 90 ° C.
• the hydrated metal acid comprises at least one metal from Group VIB.
• the group VIB metal present in the acid is preferably chosen from molybdenum and tungsten.
• the hydrated metal acid can additionally include phosphorus and silicon.
• the metal acid can be an acid of a Keggin type heteropolyanion.
• the mass ratio between said hydrated metal acid and said electrically conductive support is between 0.1 and 4, preferably between 0.5 and 3.
• the hydrated metallic acid is in solid form, that is to say that the bringing into contact between said electrically conductive support and said hydrated metallic acid is carried out at a temperature below the melting temperature of said acid.
• Step b) is preferably carried out at room temperature.
• the contacting of said electrically conductive support and hydrated metal acid can be done by any method known to those skilled in the art.
• the contacting of said electrically conductive support and of said hydrated metallic acid is carried out with contact means chosen from among convective mixers, drum mixers or static mixers.
• Step b) is preferably carried out for a period of between 5 minutes to 12 hours depending on the type of mixer used, preferably between 10 minutes and 4 hours, and even more preferably between 15 minutes and 3 hours.
• step b) consists of bringing said wetted electrically conductive support into contact with at least one hydrated metal acid comprising at least one metal from group VI B, the melting point of said hydrated solid metal acid of which is between 20 and 100 ° C, to form a solid mixture, the mass ratio between said metallic acid and said porous support being between 0.1 and 4.
• step c) the addition of other solid compounds to the catalytic material obtained according to the preparation process of the invention after step c) is not necessary to obtain a catalytic activity close to those of the catalytic materials according to the state of technique (prepared by impregnation using an impregnation solution), it may be advantageous in certain cases to add other solid compounds to the solid mixture obtained in step b).
• Such compounds can in particular be a metal salt comprising at least one metal from group VIII, phosphoric acid or else an organic compound.
• step b) further comprises bringing into contact with at least one metal salt comprising at least one metal from group VIII whose melting point of said metal salt is between 20 and 100 ° C, to form a solid mixture with the electrically conductive support and the hydrated metal acid, the molar ratio (metal of group VI I l) / (metal of group VI B) being between 0.1 and 0.8.
• the metal salt must have a relatively low melting point, especially lower than its decomposition temperature.
• the melting point of the metal salt is between 20 and 100 ° C, and preferably between 40 and 60 ° C.
• the metal salt comprises at least one metal from group VIII.
• the group VIII metal present in the salt is preferably chosen from nickel, cobalt and iron.
• the metal salt is hydrated.
• the metal salt is a hydrated nitrate salt or a hydrated sulfate salt.
• the molar ratio (metal from group VIII) / (metal from group VIB) is generally between 0.1 and 0.8, preferably between 0.15 and 0.6.
• phosphorus has no catalytic character but increases the catalytic activity of the active phase by the formation of heteropolyanions which increases the dispersion of the elements on the surface of the support.
• phosphorus is introduced into the catalytic material along with the hydrated metal acid.
• the P / Mo ratio is 0.08.
• the molar ratio of P / W is 0.08.
• step b) further comprises bringing into contact with phosphoric acid, to form a solid mixture with the electrically conductive support and the hydrated metal acid and optionally the metal salt comprising in addition. minus one metal from group VIII.
• the phosphorus / (metals of group VI B) molar ratio is generally between 0.08 and 1, preferably between 0.1 and 0.9, and very preferably between 0.15 and 0.8.
• step b) further comprises bringing into contact with an organic compound comprising oxygen and / or nitrogen and / or sulfur, the melting point of said organic compound of which is within between 20 and 100 ° C, to form a solid mixture with the electrically conductive support and the hydrated metal acid, and optionally the metal salt comprising at least one metal from group VIII and phosphoric acid.
• the organic compound is chosen from a compound comprising one or more chemical functions chosen from a carboxylic, alcohol, thiol, thioether, sulfone, sulfoxide, ether, aldehyde, ketone, ester, carbonate, amine, nitrile, imide, oxime function, urea and amide or else compounds including a furan ring or also sugars.
• organic compounds comprising oxygen and / or nitrogen and / or sulfur and having a melting point of between 20 and 100 ° C
• the organic compound / group VI B metal molar ratio is between 0.01 and 5 mol / mol, preferably between 0.05 and 3 mol / mol, preferably between 0.05 and 2 mol / mol and very preferably, between 0.1 and 1.5 mol / mol.
• step c) of the preparation process according to the invention the solid mixture obtained at the end of step b) is heated with stirring to a temperature between the melting point of said hydrated metal acid and 100 ° C. .
• Step c) is advantageously carried out at atmospheric pressure.
• Step c) is generally carried out between 5 minutes and 12 hours, preferably between 5 minutes and 4 hours.
• the stirring (mechanical homogenization) of the mixture can be carried out by any method known to those skilled in the art.
• convective mixers, drum mixers or static mixers can be used.
• step c) is carried out by means of a drum mixer whose speed of rotation is between 4 and 70 revolutions / minute, preferably between 10 and 60 revolutions / minute.
• a material is obtained which comprises an electrically conductive support and at least one metal from group VIB in the form of hydrated metal acid.
• the material can be subjected to a drying step at a temperature below 200 ° C, advantageously between 100 ° C and below 200 ° C, preferably between 50 ° C and 180 ° C, more preferably between 70 ° C and 150 ° C, very preferably between 75 ° C and 130 ° C.
• the drying temperature of step is generally higher than the heating temperature of step c). Preferably, the drying temperature of step is at least 10 ° C higher than the heating temperature of step c).
• the drying step is preferably carried out under an inert atmosphere.
• the drying step can be carried out by any technique known to those skilled in the art. It is advantageously carried out at atmospheric pressure or at reduced pressure. Preferably, this step is carried out at atmospheric pressure. It is advantageously carried out in a crossed bed using a hot inert gas. Preferably, when the drying is carried out in a fixed bed, the gas used is an inert gas such as argon or nitrogen. Very preferably, the drying is carried out in a crossed bed in the presence of nitrogen. Preferably, the drying step has a duration of between 5 minutes and 4 hours, preferably between 30 minutes and 4 hours and very preferably between 1 hour and 3 hours.
• a dried material is then obtained, which will be subjected to a sulfurization step d).
• the drying step can in particular be carried out when an organic compound is present.
• the drying is preferably carried out so as to preferably retain at least 30% by weight of the organic compound introduced, preferably this amount is greater than 50% by weight and even more preferably greater than 70% by weight, calculated. based on the carbon remaining on the catalyst.
• the remaining carbon is measured by elemental analysis according to ASTM D5373.
• a calcination step is carried out at a temperature between 200 ° C and 600 ° C, preferably between 250 ° C and 550 ° C, under an inert atmosphere (nitrogen for example).
• the duration of this heat treatment is generally between 0.5 hours and 16 hours, preferably between 1 hour and 5 hours.
• the catalytic material contains no more or very little organic compound when it has been introduced.
• the introduction of the organic compound during its preparation made it possible to increase the dispersion of the active phase, thus leading to a more active catalytic material.
• the catalytic material is preferably not subjected to calcination.
• Impregnation step using an impregnation solution via post-impregnation (optional)
• step c) of the preparation process according to the invention it may be advantageous in certain cases to add to the material obtained according to step c) of the preparation process according to the invention, or to the material obtained after the optional drying step or after the optional drying step.
• calcination of at least one of the additional metal precursors by impregnation using an impregnation solution it is also possible to add phosphorus or an organic compound.
• This conventional impregnation step has the advantage of being able to use metal precursors or organic compounds which are not accessible via the molten medium technique (because in liquid form or having too high a melting point).
• the heating step c), or the optional drying step or the optional calcination step can be followed by an impregnation step using an impregnation solution. and in which said catalyst is brought into contact with an impregnation solution comprising a metal from group VI B and / or a metal from group VIII and / or phosphorus and / or an organic compound comprising oxygen and / or nitrogen and / or sulfur.
• an impregnation solution comprising a metal from group VI B and / or a metal from group VIII and / or phosphorus and / or an organic compound comprising oxygen and / or nitrogen and / or sulfur.
• the metal from group VI B when it is introduced, is preferably chosen from molybdenum and tungsten.
• the metal from group VIII when it is introduced is preferably chosen from cobalt, nickel and a mixture of these two metals.
• the group VI B metal introduced and / or the group VIII metal introduced may or may not be identical to the metals already present in the material from step c).
• the sources of molybdenum use may be made of oxides and hydroxides, molybdic acids and their salts, in particular ammonium salts such as ammonium molybdate, ammonium heptamolybdate, phosphomolybdic acid (H 3 PM0 12 O 40 ), and their salts, and optionally silicomolybdic acid (hUSiMo ⁇ C o) and its salts.
• the sources of molybdenum can also be any heteropolycompound such as Keggin, Lacunar Keggin, substituted Keggin, Dawson, Anderson, Strandberg, for example. Molybdenum trioxide and heteropolycompounds of Keggin, lacunar Keggin, substituted Keggin and Strandberg type are preferably used.
• the tungsten precursors which can be used are also well known to those skilled in the art.
• the sources of tungsten it is possible to use oxides and hydroxides, tungstic acids and their salts, in particular ammonium salts such as ammonium tungstate, ammonium metatungstate, phosphotungstic acid and theirs. salts, and optionally silicotungstic acid (hUSiW ⁇ O ⁇ ) and its salts.
• the sources of tungsten can also be any heteropolycompound such as Keggin, lacunar Keggin, substituted Keggin, Dawson, for example.
• Oxides and ammonium salts such as ammonium metatungstate or heteropolyanions of the Keggin, lacunar Keggin or substituted Keggin type are preferably used.
• the cobalt precursors which can be used are advantageously chosen from oxides, hydroxides, hydroxycarbonates, carbonates and nitrates, for example. Cobalt hydroxide and cobalt carbonate are preferably used.
• the nickel precursors which can be used are advantageously chosen from oxides, hydroxides, hydroxycarbonates, carbonates and nitrates, for example. Nickel hydroxide and nickel hydroxycarbonate are preferably used.
• the molar ratio (metal of group VI I l) / (metal of group VI B) is generally between 0.1 and 0.8, preferably between 0.15 and 0.6.
• Phosphorus can also be added to the impregnation solution.
• the preferred phosphorus precursor is orthophosphoric acid H 3 PO 4 , but its salts and esters such as ammonium phosphates are also suitable.
• the phosphorus can also be introduced at the same time as the metal (s) / metals of group VI B in the form of heteropolyanions of Keggin, lacunar Keggin, substituted Keggin or of the Strandberg type.
• the molar ratio of the phosphorus added per metal from group VI B is between 0.1 and 2.5 mol / mol, preferably between 0.1 and 2.0 mol / mol, and even more preferred between 0.1 and 1.0 mol / mol.
• An organic compound comprising oxygen and / or nitrogen and / or sulfur can also be introduced into the impregnation solution.
• the function of additives or organic compounds is to increase the catalytic activity compared to catalysts without additives.
• Said organic compound is preferably impregnated on said catalyst after solubilization in aqueous or non-aqueous solution.
• the organic compound is chosen from a compound comprising one or more chemical functions chosen from a carboxylic, alcohol, thiol, thioether, sulfone, sulfoxide, ether, aldehyde, ketone, ester, carbonate, amine, nitrile, imide, oxime function, urea and amide or else compounds including a furan ring or also sugars.
• the organic compound containing oxygen can be one or more chosen from compounds comprising one or more chemical functions chosen from a carboxylic, alcohol, ether, aldehyde, ketone, ester or carbonate function or else compounds including a furan ring. or even sugars.
• the organic compound containing oxygen can be one or more chosen from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, a polyethylene glycol (with a molecular weight of between 200 and 1500 g / mol), propylene glycol, 2-butoxyethanol, 2- (2-butoxyethoxy) ethanol, 2- (2-methoxyethoxy) ethanol, triethylene glycoldimethylether, glycerol, acetophenone, 2,4-pentanedione, pentanone, acetic acid, maleic acid, malic acid, malonic acid, oxalic acid, gluconic acid, tartaric acid, citric acid, g-ketovaleric acid, a succinate of C1-C4 dialkyl, and more particularly dimethyl succinate, methyl acetoacetate, ethyl acetoacetate, 2-methoxyethyl 3-oxobutanoate, 2-methacryloyloxyethyl
• the organic compound containing nitrogen can be one or more chosen from compounds comprising one or more chemical functions chosen from an amine or nitrile function.
• the organic compound containing nitrogen can be one or more chosen from the group consisting of ethylenediamine, diethylenetriamine, hexamethylenediamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, acetonitrile , octylamine, guanidine or a carbazole.
• the organic compound containing oxygen and nitrogen can be one or more chosen from compounds comprising one or more chemical functions chosen from a carboxylic acid, alcohol, ether, aldehyde, ketone, ester, carbonate or amine function.
• the organic compound containing oxygen and nitrogen can be one or more selected from the group consisting of 1,2-cyclohexanediaminetetraacetic acid, monoethanolamine (MEA), 1- methyl-2-pyrrolidinone, dimethylformamide, ethylenediaminetetraacetic acid (EDTA), alanine, glycine, nitrilotriacetic acid (NTA), N- (2-hydroxyethyl) ethylenediamine-N, N ', N '-triacetic (HEDTA), diethylenetriaminepentaacetic acid (DTPA), tetramethylurea, glutamic acid, dimethylglyoxime, bicine, tricine, 2-methoxyethyl cyanoacetate, 1-ethyl-2-pyrrolidinone, 1-vinyl-2-pyrrolidinone, 1, 3-dimethyl-2-imidazolidinone, 1- (2-hydroxye
• the organic sulfur-containing compound can be one or more chosen from compounds comprising one or more chemical functions chosen from a thiol, thioether, sulfone or sulfoxide function.
• the organic compound containing sulfur can be one or more chosen from the group consisting of thioglycolic acid, 2,2'-thiodiethanol, 2-hydroxy-4-methylthiobutanoic acid, a sulfonated derivative of a benzothiophene or a sulfoxidized derivative of a benzothiophene, methyl 3- (methylthio) propanoate and ethyl 3- (methylthio) propanoate.
• the organic compound contains oxygen, preferably it is chosen from g-valerolactone, 2-acetylbutyrolactone, triethylene glycol, diethylene glycol, ethylene glycol, ethylenediaminetetra-acetic acid (EDTA), 'maleic acid, malonic acid, citric acid, gluconic acid, dimethyl succinate, glucose, fructose, sucrose, sorbitol, xylitol, g-ketovaleric acid, dimethylformamide, 1-methyl-2-pyrrolidinone, propylene carbonate, 2-methoxyethyl 3-oxobutanoate, bicine, tricine, 2-furaldehyde (also known as furfuraldehyde), 5-hydroxymethylfurfural (also known as name 5- (hydroxymethyl) -2-furaldehyde or 5-HMF), 2-acetylfuran, 5-methyl-2-furaldehyde, ascorbic acid, butyl lactate, ethyl 3-hydroxy
• the molar ratio of the organic compound added per metal from group VI B is between 0.01 and 5 mol / mol, preferably between 0.05 and 3 mol / mol, preferably between 0.05 and 2 mol / mol and very preferably between 0.1 and 1.5 mol / mol.
• the different molar ratios apply for each of the organic compounds present.
• the impregnation step using an impregnation solution and in which said material is brought into contact with an impregnation solution comprising a metal from group VIB and / or a metal from group VIII and / or phosphorus and / or an organic compound comprising oxygen and / or nitrogen and / or sulfur can be produced either by excess impregnation, or by dry impregnation, or by any other means known to those skilled in the art. job.
• Impregnation at equilibrium consists in immersing the support or the material in a volume of solution (often largely) greater than the pore volume of the support or of the material r while maintaining the system under agitation to improve the exchanges between the solution and the support or material. An equilibrium is finally reached after diffusion of the different species in the pores of the support or material. Control of the quantity of elements deposited is ensured by the preliminary measurement of an adsorption isotherm which links the concentration of elements to be deposited contained in the solution to the quantity of elements deposited on the solid in equilibrium with this solution.
• Dry impregnation consists in introducing a volume of impregnation solution equal to the pore volume of the support or of the material. Dry impregnation allows all of the metals and additives contained in the impregnation solution to be deposited on a given support or material.
• any impregnation solution described above can comprise any polar protic solvent known to those skilled in the art.
• a polar protic solvent is used, for example chosen from the group formed by methanol, ethanol and water.
• the impregnation solution comprises a water-ethanol or water-methanol mixture as solvents in order to facilitate the impregnation of the compound containing a metal from group VIB (and optionally the compound containing a metal from group VIII and / or phosphorus and / or organic compound) on the catalyst.
• the solvent used in the impregnation solution consists of water or a water-ethanol or water-methanol mixture.
• the solvent may be absent in the impregnation solution.
• phosphoric acid also acts as a solvent.
• the impregnation step using an impregnation solution can be advantageously carried out by one or more impregnation in excess of solution or preferably by one or more dry impregnation and very preferably by a single impregnation with dryness of said catalyst, using the impregnation solution.
• the impregnation step using an impregnation solution involves several implementation methods. They are distinguished in particular by the time of introduction of the organic compound when it is present and which can be carried out either at the same time as the impregnation of the metal of group VIB (co-impregnation), or after (post-impregnation). , or before (pre-impregnation). In addition, the modes of implementation can be combined. Preferably, a co-impregnation is carried out.
• the impregnated support is allowed to mature. Curing allows the impregnation solution to disperse homogeneously within the support or material.
• Any maturation step described in the present invention is advantageously carried out at atmospheric pressure, in an atmosphere saturated with water and at a temperature between 17 ° C and 50 ° C, and preferably at room temperature.
• a maturation time of between ten minutes and forty-eight hours and preferably between thirty minutes and six hours is sufficient.
• each impregnation step is preferably followed by an intermediate drying step at a temperature below 200 ° C, advantageously between 100 ° C and below 200 ° C, preferably between 50 ° C and 180 ° C, more preferably between 70 ° C and 150 ° C, very preferably between 75 ° C and 130 °.
• a maturation period was observed between the impregnation step and the intermediate drying step.
• a calcination step can be carried out after the drying step, at a temperature between 200 ° C and 600 ° C, preferably between 250 ° C and 550 ° C, under an inert atmosphere ( nitrogen for example).
• Impregnation step using an impregnation solution via pre-impregnation (optional)
• step a) of the process according to the invention it may be advantageous in certain cases to add, before step a) of the process according to the invention, to the electrically conductive support at least one of the metal precursors and / or phosphorus and / or a compound organic by impregnation using an impregnation solution (conventional pre-impregnation).
• This conventional impregnation step has the advantage of being able to use metal precursors or organic compounds which are not accessible via the molten medium technique (because in liquid form or having too high a melting point).
• step a) of bringing the water into contact with the electrically conductive support can be preceded by an impregnation step using an impregnation solution and in which contacting said support with an impregnation solution comprising a metal from group VI B and / or a metal from group VIII and / or phosphorus and / or an organic compound comprising oxygen and / or nitrogen and / or sulfur.
• the pre-impregnation step can be carried out in the same way as the post-impregnation step described above. It generally comprises at least one impregnation step, followed by drying and optionally by calcination as described for the post-impregnation step.
• This pre-impregnation step is particularly advantageous when it is desired to introduce an organic compound having a melting point above 100 ° C.
• organic compounds comprising oxygen and / or nitrogen and / or sulfur and having a melting point higher than 100 ° C
• malonic acid citric acid, acid gluconic, glucose, fructose, 2-methoxyethyl 3-oxobutanoate, 5-methyl-2-furaldehyde.
• the molar ratio of the organic compound added per metal from group VI B present in the material introduced subsequently via the impregnation in a molten medium and optionally supplemented by a pre- or post-impregnation is between 0.01 and 5 mol / mol, preferably between 0.05 and 3 mol / mol, preferably between 0.05 and 2 mol / mol and very preferably between 0.1 and 1.5 mol / mol.
• the different molar ratios apply for each of the organic compounds present.
• the material is preferably not subjected to calcination.
• the sulfurization carried out during step d) is intended to at least partially sulfide the metal from group VIB, and optionally at least partially the metal from group VIII when it is present.
• Step d) of sulfurization can be carried out advantageously using an H2S / H2 or H2S / N2 gas mixture containing at least 5% by volume of h ⁇ S in the mixture or under a stream of pure hhS at a temperature between 100 ° C and 600 ° C. She is usually carried out under a total pressure equal to or greater than 0.1 MPa, generally for at least 2 hours.
• the sulfurization temperature is between 350 ° C and 550 ° C.
• the sulfurization temperature is between 100 ° C and 250 ° C or between 400 ° C and 600 ° C.
• the catalytic material resulting from the preparation process according to the invention comprises at least one electrically conductive support and at least one metal from group VI B in the form of sulphides.
• the support for the catalytic material is a support comprising at least one electrically conductive material.
• the support is made of an electrically conductive material.
• the support for the catalytic material comprises at least one material chosen from carbon structures of the carbon black type, graphite, carbon nanotubes or graphene.
• the support for the catalytic material comprises at least one material selected from gold, copper, silver, titanium, silicon.
• a porous and non-electrically conductive material can be made electrically conductive by depositing an electrically conductive material on the surface thereof; let us cite for example a refractory oxide, such as an alumina, within which graphitic carbon is deposited.
• the support for the catalytic material advantageously has a BET (SS) specific surface area of greater than 75 m 2 / g, preferably greater than 100 m 2 / g, very preferably greater than 130 m 2 / g.
• the electrically conductive support has a water uptake volume or ERV of between 0.2 and 8 cm 3 . g- 1 , preferably between 0.5 and 2 cm 3 . g 1 .
• the retention volume is determined as follows: poured over a known mass of support, placed in a bezel rotated with the aid of a motor, deionized water, drop by drop using a burette graduated, while the support is mixed manually using a spatula. When the support begins to adhere to the wall of the bezel, the drip is stopped and the volume of water used is noted. The volume of water / mass of support ratio is then calculated, the water uptake volume (VRE) being expressed in cm 3 / g.
• VRE water uptake volume
• the activity of the catalytic material in particular for the production of hydrogen by electrolysis of water, is provided by an element of group VI B and optionally by at least one element of group VIII.
• the active phase is chosen from the group formed by combinations of the elements nickel-molybdenum or cobalt-molybdenum or nickel-cobalt-molybdenum or nickel-tungsten or nickel-molybdenum-tungsten.
• the total content of metal from group VI B (introduced by the hydrated metal acid and optionally supplemented by impregnation using an impregnation solution comprising a metal from group VI B in pre- or post-impregnation) present in the catalytic material is between 4 and 70% by weight of the element of the metal of group VI B relative to the weight of the final catalytic material obtained after the last preparation step, ie the sulfurization.
• the total molybdenum (Mo) content is between 4 and 60% by weight of element Mo relative to the weight of the final catalytic material, and preferably between 7 and 50% by weight per relative to the weight of the final catalytic material obtained after the last preparation step, ie sulfurization.
• the total tungsten content (W) is between 7 and 70% by weight of element W relative to the weight of the final catalytic material, and preferably between 12 and 60% by weight per relative to the weight of the final catalytic material obtained after the last preparation step, ie sulfurization.
• the surface density which corresponds to the quantity of molybdenum Mo atoms deposited per surface unit of support will advantageously be between 0.5 and 20 atoms of Mo per square nanometers of support and preferably between 2 and 15 atoms of Mo per nanometers support square.
• the catalytic material comprises at least one metal from group VIII
• the total content of metal from group VIII is advantageously between 0.1 and 15% by weight of group VIII element, preferably between 0.5 and 10% by weight relative to the total weight of the final catalytic material obtained after the last step preparation, ie sulfurization.
• the catalytic material may also have a total phosphorus content (introduced by phosphoric acid by impregnation in a molten medium or by impregnation using an impregnation solution comprising phosphoric acid) present in the catalytic material generally between 0.1 and 20% by weight of P2O5 relative to the total weight of catalyst, preferably between 0.2 and 15% by weight of P2O5, very preferably between 0.3 and 11% by weight of P2O5.
• the phosphorus present in the catalytic material is combined with the metal of group VI B and optionally also with the metal of group VIII in the form of heteropolyanions.
• the phosphorus / (metal of group VIB) molar ratio is generally between 0.08 and 1, preferably between 0.1 and 0.9, and very preferably between 0.15 and 0.8 .
• the phosphorus content in the catalytic material is expressed as oxides after correction for the loss on ignition of the sample of catalytic material at 550 ° C for two hours in a muffle furnace. Loss on ignition is due to loss of moisture. It is determined according to ASTM D7348.
• the catalytic material advantageously has a BET (SS) specific surface area of greater than 75 m 2 / g, preferably greater than 100 m 2 / g, very preferably greater than 130 m 2 / g.
• the catalytic material obtained by the preparation process according to the invention can be used as an electrode catalytic material suitable for use for electrochemical reactions, and in particular for the electrolysis of water in a liquid electrolytic medium.
• the electrode comprises a catalytic material obtained by the preparation process according to the invention and a binder.
• the binder is preferably a polymer binder chosen for its ability to be deposited in the form of a layer of varying thickness and for its capacities for ionic conduction in an aqueous medium and for diffusing dissolved gases.
• the layer of variable thickness advantageously between 1 and 500 ⁇ m, in particular of the order of 10 to 100 ⁇ m, can in particular be a gel or a film.
• the ionically conductive polymer binder is:
• - Polymers stable in aqueous medium which may be perfluorinated, partially fluorinated or non-fluorinated and having cationic groups allowing the conduction of hydroxide anions, said cationic groups being of quaternary ammonium, guanidinium, imidazolium, phosphonium, pyridium or sulphide type;
• polymers which are stable in an aqueous medium which may be perfluorinated, partially fluorinated or non-fluorinated and having anionic groups allowing the conduction of protons; - grafted polybenzimidazole;
• polymers which are stable in an aqueous medium and which have cationic groups allowing the conduction of anions mention may in particular be made of polymer chains of perfluorinated type, for example polytetrafluoroethylene (PTFE), of partially fluorinated type, such as, for example, polyvinylidene fluoride. (PVDF) or of the non-fluorinated type such as polyethylene, which will be grafted with anionic conductive molecular groups.
• PTFE polytetrafluoroethylene
• PVDF polyvinylidene fluoride
• non-fluorinated type such as polyethylene
• polymers which are stable in an aqueous medium and which have anionic groups allowing the conduction of protons one can consider any stable polymer chain in an aqueous medium containing groups such as -SO 3 ⁇ , -COO-, -PO 3 2 ⁇ , -PO 3 H-, -C 6 H 4 O-. Mention may in particular be made of Nafion®, phosphonated sulfonated polybenzimidazole (PBI), sulfonated or phosphonated polyetheretherketone (PEEK).
• PBI phosphonated sulfonated polybenzimidazole
• PEEK sulfonated or phosphonated polyetheretherketone
• any mixture comprising at least two polymers, at least one of which is chosen from the groups of polymers mentioned above, can be used, provided that the final mixture is an ionic conductor in aqueous medium.
• a mixture comprising a stable polymer in an alkaline medium and exhibiting cationic groups allowing the conduction of hydroxide anions with a polyethylene not grafted by anionic conductive molecular groups provided that this final mixture is anionic conductor in the medium. alkaline.
• polybenzimidazole is used in the present invention as a binder. It is inherently not a good ionic conductor, but in an alkaline environment or acid, it turns out to be an excellent polyelectrolyte with respectively very good anionic or cationic conduction properties.
• PBI is a polymer generally used, in grafted form, in the manufacture of proton conductive membranes for fuel cells, in membrane-electrode assemblies and in PEM-type electrolysers, as an alternative to Nafion®.
• the PBI is generally functionalized / grafted, for example by a sulfonation, in order to make it a proton conductor.
• the role of the PBI in this type of system is then different from that which it has in the manufacture of the electrodes according to the present invention where it only serves as a binder and has no direct role in the electrochemical reaction.
• chitosan which can also be used as an anionic or cationic conductive polymer, is a polysaccharide exhibiting ionic conduction properties in a basic medium which are similar to those of PBI (G. Couture, A. Alaaeddine, F. Boschet, B. Ameduri, Progress in Polymer Science 36 (2011) 1521-1557).
• the electrode according to the invention is formulated by a method which further comprises a step of removing the solvent at the same time or after step 3). Removal of the solvent can be carried out by any technique known to those skilled in the art, in particular by evaporation or phase inversion.
• the solvent is an organic or inorganic solvent whose evaporation temperature is lower than the decomposition temperature of the polymer binder used. Mention may be made, as examples, of dimethylsulfoxide (DMSO) or acetic acid. Those skilled in the art are able to choose the organic or inorganic solvent suitable for the polymer or for the mixture of polymer used as binder and capable of being evaporated.
• DMSO dimethylsulfoxide
• acetic acid acetic acid
• the electrode is suitable for being used for the electrolysis of water in an alkaline liquid electrolyte medium and the polymer binder is then an anionic conductor in an alkaline liquid electrolyte medium, in particular a conductor of hydroxides.
• alkaline liquid electrolyte medium means a medium whose pH is greater than 7, advantageously greater than 10.
• the binder is advantageously a conductor of hydroxides in an alkaline medium. It is chemically stable in electrolysis baths and has the capacity to diffuse and / or transport the OH- ions involved in the electrochemical reaction to the surface of the particles, sites of the redox reactions for the production of H2 and O2 gases. Thus, a surface which is not in direct contact with the electrolyte is still involved in the electrolysis reaction, a key point in the efficiency of the system.
• the binder chosen and the shaping of the electrode do not hinder the diffusion of the gases formed and limit their adsorption, thus allowing their evacuation.
• the electrode is suitable for being used for the electrolysis of water in an acidic liquid electrolyte medium and the polymer binder is a cationic conductor in an acidic liquid electrolyte medium, in particular a conductor of protons.
• the term “acidic medium” means a medium whose pH is less than 7, advantageously less than 2.
• the polymer binder / catalytic material mass ratio is between 5/95 and 95/5, preferably between 10/90 and 90/10, and more preferably between 10/90 and 40/60.
• the electrode can be prepared according to techniques well known to those skilled in the art. More particularly, the electrode is formulated by a preparation process comprising the following steps: 1) at least one ionically conductive polymeric binder is dissolved in a solvent or a mixture of solvents;
• step 1) at least one catalytic material prepared according to the invention, in powder form, is added to the solution obtained in step 1) to obtain a mixture; steps 1) and 2) being carried out in any order, or simultaneously;
• step 2) the mixture obtained in step 2) is deposited on a metallic or metallic-type conductive support or collector.
• the term “powder of catalytic material” means a powder consisting of particles of micron, submicron or nanometric size.
• the powders can be prepared by techniques known to those skilled in the art.
• the term “metal-type support or collector” is understood to mean any conductive material having the same conduction properties as metals, for example graphite or certain conductive polymers such as polyaniline and polythiophene.
• This support can have any shape allowing the deposition of the mixture obtained (between the binder and the catalytic material) by a method chosen from the group comprising in particular dipping, printing, induction, pressing, coating , spinning deposition (or “spin-coating” according to the English terminology), filtration, vacuum deposition, spray deposition, casting, extrusion or rolling.
• Said support or said collector may be solid or perforated.
• a support there may be mentioned a grid (perforated support), a plate or a sheet of stainless steel (304L or 316L for example) (solid supports).
• the advantage of the mixture according to the invention is that it can be deposited on a solid or perforated collector, by the usual easily accessible deposition techniques and allowing deposition in the form of layers of variable thicknesses, ideally of the order of 10 at 100 pm.
• the mixture can be prepared by any technique known to those skilled in the art, in particular by mixing the binder and at least one catalytic material in powder form in an appropriate solvent or a mixture of suitable solvents for obtaining a mixture with rheological properties allowing the deposition of electrode materials in the form of a film of controlled thickness on an electronically conductive substrate.
• the use of the catalytic material in powder form allows maximization of the surface developed by the electrodes and enhancement of the associated performance.
• Those skilled in the art will be able to make the choices of the various formulation parameters in the light of their general knowledge and of the physicochemical characteristics of said mixtures.
• Another object according to the invention relates to an electrolysis device comprising an anode, a cathode, an electrolyte, in which at least one of the anode or the cathode is an electrode according to the invention.
• the electrolysis device can be used as a water electrolysis device for the production of a gas mixture of hydrogen and oxygen and / or the production of hydrogen alone comprising an anode, a cathode and an electrolyte, said device being characterized in that at least one of the cathode or of the anode is an electrode according to the invention, preferably the cathode.
• the electrolysis device consists of two electrodes (an anode and a cathode, electronic conductors) connected to a direct current generator, and separated by an electrolyte (ionic conductive medium).
• the anode is the seat of the oxidation of water.
• the cathode is the site of proton reduction and hydrogen formation.
• the electrolyte can be:
• a proton exchange polymer membrane which ensures the transfer of protons from the anode to the cathode and allows the separation of the anode and cathode compartments, which avoids reoxidizing at the anode the species reduced at the cathode and vice versa;
• the reaction has a standard potential of -1.23 V, which means that it ideally requires a potential difference between the anode and the cathode of 1.23 V.
• a standard cell usually operates under a potential difference of 1. , 5 V and at room temperature.
• Some systems can operate at higher temperatures. Indeed, it has been shown that electrolysis under high temperature (HTE) is more efficient than the electrolysis of water at room temperature, on the one hand, because part of the energy required for the reaction can be provided by heat (cheaper than electricity) and, on the other hand, because the activation of the reaction is more efficient at high temperature.
• HTE systems generally operate between 100 ° C and 850 ° C.
• the electrolysis device can be used as a nitrogen electrolysis device for the production of ammonia, comprising an anode, a cathode and an electrolyte, said device being characterized in that at least one of the cathode or anode is an electrode according to the invention, preferably the cathode.
• the electrolysis device consists of two electrodes (an anode and a cathode, electronic conductors) connected to a direct current generator, and separated by a electrolyte (ionic conductive medium).
• the anode is the site of the oxidation of water.
• the cathode is the site of nitrogen reduction and ammonia formation. Nitrogen is continuously injected into the cathode compartment.
• the nitrogen reduction reaction is:
• the electrolyte can be:
• a proton exchange polymer membrane which ensures the transfer of protons from the anode to the cathode and allows the separation of the anode and cathode compartments, which avoids reoxidizing at the anode the reduced species at the cathode and vice versa.
• the electrolysis device can be used as a carbon dioxide electrolysis device for the production of formic acid, comprising an anode, a cathode and an electrolyte, said device being characterized in that at least one of the cathode or the anode is an electrode according to the invention.
• An example of anode and electrolyte that can be used in such a device is described in detail in document FR3007427.
• the electrolysis device can be used as a fuel cell device for the production of electricity from hydrogen and oxygen comprising an anode, a cathode and an electrolyte (liquid or solid), said device being characterized in that at least one of the cathode or of the anode is an electrode according to the invention.
• the fuel cell device consists of two electrodes (an anode and a cathode, electronic conductors) connected to a load C to deliver the electric current produced, and separated by an electrolyte (ionic conductive medium).
• the anode is the site of the oxidation of hydrogen.
• the cathode is the site of oxygen reduction.
• the electrolyte can be:
• the following examples illustrate the present invention.
• the examples below relate to the electrolysis of water in a liquid electrolytic medium for the production of hydrogen.
• Example 1 Preparation of a C1 catalytic material (not in accordance with the invention) from H3PM012O40, 28 H 2 0 and Ni (N0 3 ) 2 , 6 H 2 0 in ethanol.
• the catalytic material C1 (compliant) is prepared by dry impregnation of 10 g of commercial carbon type support (ketjenblack®, 1400 m 2 / g) with 26 mL of solution.
• the support is impregnated by making a drop by drop of the volume of the solution, in rotation in a bezel.
• the precatalyst is then matured for 4 h (maturator filled with ethanol), then dried under an inert atmosphere and at reduced pressure (while drawing under vacuum) at 60 ° C (oil bath) using a rotary evaporator for 2h.
• the precatalyst is then sulfurized under pure H2S at a temperature of 400 ° C. for 2 hours under 0.1 MPa (1 bar) of pressure.
• Example 2 Preparation of a C2 catalytic material (according to the invention) from H3PM012O40, 28 H2O and Ni (NC> 3) 2.6 H2O impregnated in fusion.
• the catalytic material C2 (compliant) is prepared by molten impregnation of 10 g of commercial carbon type support (ketjenblack®, 1400 m 2 / g).
• the support is previously impregnated with 10 ml of water or 38% of the VRE. In order to let the support soak up properly, it is placed in a ripener for 1 hour.
• the water-pre-impregnated support is then transferred to the reactor with H3PM012O40, 28 H2O (PMA) and Ni (NC> 3) 2, 6H2O, whose melting points are respectively 85 ° C and 56.7 ° C.
• the reflux is set up and the reactor is heated to 85 ° C. with stirring for 3 h.
• the precatalyst is then left to mature for 18 hours.
• the precatalyst is then sulfurized under pure H2S at a temperature of 400 ° C. for 2 hours under 0.1 MPa (1 bar) of pressure.
• the characterization of the catalytic activity of the catalytic materials is carried out in a cell with 3 electrodes.
• This cell is composed of a working electrode, a platinum counter electrode and a Hg / Hg2S04 reference electrode.
• the electrolyte is an aqueous solution of suprapure sulfuric acid (H 2 SO 4 ) at 0.5 mol / L.
• the medium is deaerated by bubbling with argon for 30 minutes then hydrogen bubbling is carried out for 15 minutes in order to be at saturation with H2.
• An H2 sky is generated for the duration of the measurements.
• the working electrode consists of a 5 mm diameter glassy carbon disc crimped in a removable Teflon tip (rotating disc electrode).
• Glassy carbon has the advantage of having no catalytic activity and of being a very good electrical conductor.
• a catalytic ink is formulated. The glassy carbon tip is polished with diamond paste 3 then 1 ⁇ m between each test then washed with ultrasound according to the following program: 15 minutes acetone, 15 minutes EtOH + ultra pure water, 15 minutes ultra pure water then drying with oven at 110 ° C for 10 minutes.
• the ink consists of a binder in the form of a solution of 27 pL of National® 15% by mass, of a solvent (0.41 mL of ultrapure water + 1.29 mL of propan-1-ol ) and 10 mg of catalyst (C1, C2, C3) crushed with a pestle in a mortar.
• the role of the binder is to ensure the cohesion of the particles of the supported catalyst and the adhesion to the glassy carbon.
• This ink is then placed in an ultrasonic bath for 45 minutes in order to obtain good dissolution of the previously ground catalytic ink and to homogenize the mixture. 10 ⁇ l of the prepared ink are deposited on the glassy carbon tip (described above) previously heated to 100 ° C.
• - linear voltammetry it consists in applying to the working electrode a potential signal which varies with time, i.e. from 0 to - 1.1 V vs RH E at a speed of 20 mV / s, and in measuring the response faradic current, that is to say the current resulting from the oxidation-reduction reaction taking place at the level of the working electrode.
• This method is ideal for determining the catalytic power of a material for a given reaction. It allows, among other things, to determine the overvoltage necessary for the reduction of protons to H2.
• the catalytic performances are collated in Table 1, below. They are expressed as overvoltage at a current density of -10 mA / cm 2 .
• the C2 catalytic material exhibits performance relatively close to that of platinum. This result demonstrates the undeniable interest of the C2 material for the development of the hydrogen sector by electrolysis of water. Compared to catalyst C1, catalyst C2 exhibits slightly improved performance, which reinforces the advantage of the preparation by molten impregnation.

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