METHOD FOR PRODUCING A CATALYST FOR WATER ELECTROLYSIS, METHOD FOR PRODUCING AN ELECTRODE, ELECTRODE FOR WATER ELECTROLYSIS AND USE THEREOF

Abstract

TITLE OF THE INVENTION: METHOD FOR PRODUCING A CATALYST FOR WATER ELECTROLYSIS, METHOD FOR PRODUCING AN ELECTRODE, ELECTRODE FOR WATER ELECTROLYSIS AND USE THEREOF A method for producing a catalyst (59) for water electrolysis comprises at least one step in which a material (57) comprising at least one metal is brought into contact with an aqueous medium (58) containing at least one species of sulfate-reducing microorganism and at least one compound comprising sulfur (S). An electrode is capable of being manufactured using this manufacturing method. Figure for abstract: Figure 4

Description

Title of the invention: PROCESS FOR PREPARING A CATALYST FOR WATER ELECTROLYSIS, PROCESS METHOD OF MANUFACTURING AN ELECTRODE, ELECTRODE FOR WATER ELECTROLYSIS AND ITS USE Technical field of the invention

[0001] The present invention relates to the field of water electrolysis to produce dihydrogen (H2) and / or oxyhydrogen, which is a gas composed of dihydrogen (H2) and dioxygen (O2).

[0002] More specifically, the invention relates to a method for producing a catalyst for the electrolysis of water, a method for manufacturing an electrode, an electrode for the electrolysis of water and a use of this electrode. State of the art

[0003] Global warming is primarily due to an increase in the level of carbon dioxide in the atmosphere. This global warming and pollution pose a risk of massive destruction of ecosystems, rising sea levels, an increase in forest fires, epidemics of respiratory diseases, etc.

[0004] In this context, clean energy technologies are considered. In particular, one of them is the use of dihydrogen as a fuel. Having a higher energy density than gasoline, dihydrogen can provide high energy when combined with dioxygen to produce water as a by-product. On Earth, hydrogen is abundant as the major constituent of water, of which it makes up two-thirds in number of atoms.

[0005] Currently, most hydrogen is produced by steam methane reforming, which is economically attractive. However, to produce 1 kg of hydrogen, steam methane reforming releases 8 kg of carbon dioxide into the atmosphere. It is therefore important to develop alternative methods to produce hydrogen without emitting carbon dioxide or other greenhouse gases.

[0006] In this respect, direct electrolysis of water is one of the most promising technologies, as it can be completely "green" and cost-effective, especially when solar energy and / or wind energy is used to produce electricity. Therefore, research has been devoted to the development of efficient electrocatalysts and / or electrodes for high productivity. Current advanced electrodes are based on noble metals such as platinum (Pt), ruthenium (Ru), gold (Au), and iridium (Ir). However, noble metals are rare and expensive elements.

[0007] Document US 9034167 B2 discloses a system for producing hydrogen and / or oxygen. This system comprises an electrolysis cell, an integrated controller, a power control module, a voltage and / or current monitoring device, and a temperature monitoring device.

[0008] Document US 2016 / 0285118 A1 relates to a hydrogen gas generator and, more particularly, to a hydrogen generator for supplying hydrogen gas to a fuel cell system.

[0009] Document US 2015 / 0107990 A1 describes a system composed of an oxyhydrogen generator and a Zeer pot. The Zeer pot is provided to cool the oxyhydrogen generator, so as to reduce the temperature of the electrolyte and to limit the evaporation of the electrolyte. The evaporation of the electrolyte is one of the limitations in this system.

[0010] U.S. Patent No. 4,455,152 describes a hydrogen generator that includes an induction coil for heating water to the temperature where the water decomposes. The oxygen and hydrogen produced by the decomposition of the water are passed through ferrous oxide pellets placed in a fire-resistant crucible.

[0011] Document US 2010 / 0320083 A1 proposes a device which produces 4 liters of oxyhydrogen per minute, in the stoichiometric ratio, consuming 360 W at atmospheric pressure. The efficiency of this device increases from 50% to 100% by reducing the pressure by generating a vacuum.

[0012] US patent 8864974 B2 relates to a hydrogen generator and, more particularly, to a hydrogen generator comprising several cells.

[0013] US Patent No. 3,892,653 describes a hydrogen generator consisting of a voltaic cell comprising a non-reactive electrode immersed in salt water and an electrode containing reactive magnesium (Mg) which decomposes while water is decomposed to produce oxyhydrogen and / or dihydrogen. The water used to produce oxyhydrogen and / or dihydrogen is distilled water. This is a limitation, since a separate industrial plant is required to produce the distilled water in the case of scaling up to significant production capacities.

[0014] Document CN 107188326 A discloses a method in which wastewater from chemical nickel plating is treated by a combination of hydrogen peroxide oxidation and ion exchange adsorption. This method aims to recover metallic nickel from water discharged by nickel plating industries.

[0015] In WO 2016079746 A1, a method and system for producing hydrogen by electrolysis of water are described. According to this document, redox-active electrodes are used to generate hydrogen and / or oxygen by applying a potential between a hydrogen releasing electrode and an oxygen releasing electrode from an aqueous water solution. Summary of the invention

[0016] A process for producing a catalyst for the electrolysis of water comprises at least one step in which a material comprising at least one metal is brought into contact with an aqueous medium containing at least one species of sulfate-reducing microorganism and at least one compound comprising sulfur.

[0017] An electrode can be manufactured using this manufacturing method. Brief description of the figures

[0018] Other advantages and characteristics will emerge more clearly from the following description of particular embodiments of the invention, given as non-limiting examples and represented in the appended drawings, among which: [Fig.l] is a diagram of an installation for manufacturing an electrode and using it in electrolysis, according to an embodiment of the invention, [Fig.2] is a flowchart and shows the steps of a method which is a method for producing a catalyst for the electrolysis of water and which is according to an embodiment of the invention, [Fig.3] is a flowchart and shows the steps of a method which is a method for manufacturing an electrode for the electrolysis of water and which is according to an embodiment of the invention, [Fig.4] is a schematic view which shows an embodiment of one of the steps mentioned in [Fig.3], [Fig.5] is an image, obtained by microscope, of an outer surface of a nickel electrode whose nickel is bare before the step illustrated in [Fig.4], [Fig.6] is an image, obtained by microscope, of an outer surface of a treated electrode, which is the same electrode as that of [Fig.5] except that the step illustrated in [Fig.4] and cleaning have been applied to it, . [Fig.7] is an image, obtained by microscope, of a cross-section of the treated electrode visible in [Fig.6], [Fig.8] is an image, obtained by 2D atomic force microscopy, of an outer surface of the treated electrode of [Fig.6], [Fig.9] is a first graph obtained by X-ray photoelectron spectroscopy carried out on bare nickel and on the treated electrode of [Fig.6], [Fig. 10] is a second graph obtained by Raman spectroscopy performed on bare nickel and on the treated electrode of [Fig.6], [Fig.l 1] is a flowchart and shows the steps of a use, which is a use of an electrode for water electrolysis and which is according to an embodiment of the invention, and [Fig. 12] is a schematic view showing one embodiment of one of the steps mentioned in [Fig. 11]. Description of the embodiments

[0019] As used herein, the expression “organic waste” designates that which comes from the decomposition of one or more animal and / or plant materials.

[0020] As used herein, boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), polonium (Po) and astatine (At) are metalloids which are not metals.

[0021] As used herein, the term "sulfate-reducing microorganisms" refers to microorganisms capable of anaerobic respiration using the sulfate ion (SO42), as well as microorganisms capable of reducing at least one other oxidized inorganic sulfur compound, such as sulfite (SO32), dithionite (S2O4 2"), thiosulfate (S2O32 ), trithionate (S3O62 ), tetrathionate (S4O62~), elemental sulfur (S8) and polysulfides CS,,2 ).

[0022] "Distilled water" means water obtained by distillation. Water having the same degree of purity as water obtained by distillation is also called "distilled water", even if it is obtained by reverse osmosis.

[0023] By "water filtered to ten microns or less" is meant tap water or water obtained by filtration to the ten micron scale, or below, of fresh surface water such as lake and / or river water. In this case, filtration removes what are called suspended matter in the water.

[0024] "Unfiltered organic-laden water" means water that includes organic load and has not been filtered. For example, the organic load includes organic waste. For example, unfiltered organic-laden water is wastewater of domestic and / or agricultural origin. For example, unfiltered organic-laden water contains microorganisms, including sulfate-reducing microorganisms.

[0025] By "water with an organic load filtered between ten and twenty microns" is meant water that is obtained by filtration at the scale of ten microns, or above, of water with an organic load. In this case, any bacteria that may be present in the water with an organic load are not removed by filtration. For example, water with an organic load that is filtered to obtain water with Organic load filtered between ten and twenty microns is wastewater of domestic and / or agricultural origin. For example, organic load water that is filtered to obtain organic load water filtered between ten and twenty microns contains microorganisms, including sulfate-reducing microorganisms. For example, organic load includes organic waste.

[0026] [Fig. 1] represents an installation 5 for manufacturing an electrode and using it in electrolysis, according to an embodiment of the invention.

[0027] The installation 5 comprises a reservoir 11 for water which may be distilled water, water filtered to ten microns or less, unfiltered organically charged water, organically charged water filtered to between ten and twenty microns, and / or a mixture thereof. Electrodes 16 are immersed in an aqueous medium 7 resulting from the mixing of the water in the reservoir 11, sulfate-reducing microorganisms 12 and food 13 for these sulfate-reducing microorganisms.

[0028] The aqueous medium 7 resulting from the mixing of the water in the reservoir 11, the sulfate-reducing microorganisms 12 and the food 13 is contained in a basin 6 whose water can be renewed by renewal water coming from a reservoir 14. The renewal water in the reservoir 14 can be water filtered to ten microns or less, unfiltered water with an organic load, water with an organic load filtered between ten microns and twenty microns and / or a mixture of these.

[0029] A pump 15 regulates the flow rate of the renewal water. The pump 15 is connected between the tank 14 and the basin 6. A microcontroller 19 controls the operation of the pump 19.

[0030] A non-return valve 17 is connected between the basin 6 and a drainage 18 provided to evacuate the aqueous medium 7 from the basin 6.

[0031] After having been at least partially immersed in the aqueous medium 7, an electrode 16 is called a treated electrode 16. A stack 20 of treated electrodes 16 comprises several treated electrodes 16 which are grouped and assembled after having been at least partially immersed in the aqueous medium 7.

[0032] The stack 20 of treated electrodes 16 is immersed in an aqueous electrolytic solution 9, which is contained in a stainless steel storage tank 21.

[0033] The aqueous electrolytic solution 9 comprises one or more electrolytes initially present in a storage 22. The aqueous electrolytic solution 9 also comprises water initially contained in a reservoir 23. The water contained in the reservoir 23 may be distilled water, water filtered to ten microns or less, water with an organic charge filtered between ten microns and the twenty microns, and / or a mixture thereof. The electrolyte(s) initially present in a storage 22 are mixed with water by means of a mixer 24.

[0034] In operation, the treated electrodes 16 of the stack 20 are connected differently to a unidirectional current source 26 or to a unidirectional voltage source 27, so that electric currents are established between them. A current measuring and display unit 28 is provided for measuring and displaying the intensity of the current delivered by the unidirectional current source 26. A voltage measuring and display unit 29 is provided for measuring and displaying the voltage across the unidirectional voltage source 27. The microcontroller 19 controls the unidirectional current source 26 from the current measurement carried out by the current measuring and display unit 28 and / or controls the unidirectional voltage source 27 from the voltage measurement carried out by the voltage measuring and display unit 29.

[0035] In operation, the treated electrodes 16 of the stack 20 are at least partially immersed in the aqueous electrolytic solution 9. When electric currents are established in the aqueous electrolytic solution 9 using the treated electrodes 16 of the stack 20, electrolysis of the water constituting the aqueous electrolytic solution 9 occurs. Production of dihydrogen and dioxygen results from this electrolysis.

[0036] The hydrogen and / or oxygen produced by the electrolysis are collected by means of one or more collectors 30. According to an alternative embodiment of the invention, the hydrogen and / or oxygen produced by the electrolysis are collected in the form of oxyhydrogen by means of the collector(s) 30.

[0037] A non-return valve 25 is connected between the storage tank 21 and the collector(s) 30 so that hydrogen and / or oxygen are only allowed to pass in one direction, namely from the storage tank 21 to the collector(s) 30.

[0038] Preparation of a catalyst - manufacture of an electrode for the electrolysis of water

[0039] In [Fig.2], a method 40 according to an embodiment of the invention is a method for preparing a catalyst for the electrolysis of water.

[0040] In a step 41 of the method 40, a material comprising at least one metal is provided. In a step 42 of the method 40, an aqueous medium containing at least one species of sulfate-reducing microorganism and at least one compound comprising sulfur (S) is provided.

[0041] In a step 43 of the method 40, the material is subjected at least locally to ultrasonic cleaning.

[0042] A step 44 of the method 40 follows step 43. In step 44, the material comprising at least one metal is brought into contact with the aqueous medium. During step 44, the catalyst for the electrolysis of water is produced.

[0043] A step 45 of the method 40 follows step 44. In step 45, with cleaning water, the catalyst produced during step 44 is cleaned.

[0044] In [Fig.3], a method 50 according to one embodiment of the invention is a method of manufacturing an electrode for the electrolysis of water.

[0045] In a step 51 of the method 50, an electrode is provided comprising a material comprising at least one metal. In a step 52 of the method 50, an aqueous medium is provided containing at least one species of sulfate-reducing microorganism and at least one compound comprising sulfur (S).

[0046] In a step 53 of the method 50, the electrode is subjected at least locally to ultrasonic cleaning so as to subject at least locally the material comprising the metal to ultrasonic cleaning.

[0047] A step 54 of the method 50 follows step 53. In step 54, the electrode is brought into contact with the aqueous medium so as to bring at least a portion of the material comprising the metal into contact with the aqueous medium.

[0048] A step 55 of the method 50 follows step 54. In step 55, the electrode is cleaned with cleaning water. In step 55, the entire electrode is cleaned with the cleaning water at least in the case where the entire electrode has been kept immersed in the aqueous medium. According to an alternative embodiment of the invention, a portion of the electrode is cleaned with the cleaning water during step 55, this portion comprising at least the portion which has been kept immersed in the aqueous medium.

[0049] In methods 40 and 50, the metal of the material provided in step 41 and of the material of the electrode provided in step 51 is selected from the metals of groups 3 to 16 of the periodic table, with the exception of the eight noble metals which are gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os) and iridium (Ir).

[0050] In methods 40 and 50, at least a portion of the material provided in step 41 of method 40 and the electrode material provided in step 51 of method 50 consists of only a single metal, which is unalloyed, i.e., which is not a constituent of an alloy. For example, the material provided in step 41 of method 40 and the electrode material provided in step 51 of method 50 may each consist of nickel (Ni).

[0051] According to a variant of the invention, at least a portion of the material provided in step 41 of method 40 and of the material of the electrode provided in step 51 of method 50 is made of an alloy comprising the metal.

[0052] According to one possibility in methods 40 and 50, the aqueous medium contains several different species of sulfate-reducing microorganisms. According to this possibility, the aqueous medium contains at least five different species of sulfate-reducing microorganisms. reducers. Alternatively in processes 40 and 50, the aqueous medium contains only one species of sulfate-reducing microorganism.

[0053] According to one possibility in methods 40 and 50, the water of the aqueous medium is distilled water and / or water filtered to ten microns or less, for example obtained by filtration of natural surface fresh water such as river water or lake water. When this is the case, the sulfate-reducing microorganism(s) are added to the water.

[0054] According to one possibility in methods 40 and 50, the water of the aqueous medium is or comprises unfiltered organically loaded water such as wastewater of domestic, agricultural and / or urban origin. According to one possibility in methods 40 and 50, the unfiltered organically loaded water contains the sulfate-reducing microorganism(s), which then need not be added.

[0055] According to one possibility in the methods 40 and 50, the water of the aqueous medium is or comprises water with an organic load filtered between ten microns and twenty microns, for example obtained by filtration of wastewater of domestic, agricultural and / or urban origin. According to one possibility in the methods 40 and 50, the water with an organic load filtered between ten microns and twenty microns contains the sulfate-reducing microorganism(s), which can then not be added.

[0056] In method 40, step 44 is carried out by immersing at least a portion of the material comprising the metal in the aqueous medium.

[0057] In method 50, step 54 is carried out by immersing at least a portion of the electrode in the aqueous medium.

[0058] [Fig.4] illustrates an implementation of step 54. [Fig.4] also illustrates an implementation of step 44 in the case where the material comprising the metal is part of an electrode.

[0059] In [Fig.4], several electrodes 56 made of the material 57 comprising the metal are partly immersed in the aqueous medium, which is referenced 58.

[0060] While the material 57 is in contact with the aqueous medium 58 in step 44 or 54, a catalyst 59 for water electrolysis is produced. The catalyst 59 for water electrolysis is produced in the form of a porous layer on the material 57. The inventors believe that the catalyst 59 for water electrolysis is synthesized from the metal of the material 57 and the compound comprising sulfur, by at least a portion of the sulfate-reducing microorganisms present in the aqueous medium 58.

[0061] In step 44 or 54, the material 57 is left in contact with the aqueous medium 58 for a duration that is chosen according to the desired thickness of catalyst 59. For example, this duration may be of the order of at least one day.

[0062] In methods 40 and 50, the species or one of the species of sulfate-reducing microorganism in the aqueous medium 58 is chosen from bacteria: - bacillus cereus, - shewanella xiamenensis, - comamonas testosteroni, - sphingomonas dessicabilis and / or - bacillus tropicus.

[0063] It has been found that when this is the case, the catalyst 59 for the electrolysis of water is produced rapidly.

[0064] It is extremely easy to obtain the bacteria listed above, in fact: - the bacterium bacillus cereus is found in soil, dust, vegetation and food, in particular rice, - the bacterium shewanella xiamenensis is found in marine environments, including sea water and marine sediments, - Comamonas testosteroni is found in soil and aquatic environments, - Sphingomonas dessicabilis is found in desert soil and other extreme and arid environments, and - Bacillus tropicus is found in tropical environments.

[0065] As measured at 27°C for three days according to the methodology defined by Indian Standard 1S 3025 (Part 44) including Amendment No. 1 of October 2000, and also called "1S 3025 (PART 44), 1993 METHODS OF SAMPLING AND TEST (PHYSICAL AND CHEMICAL) FOR WATER AND WASTEWATER -PART 44 BIOCHEMICAL OXYGEN DEMAND (BOD)", the biochemical oxygen demand due to sulfate-reducing microorganisms in the aqueous medium is of the order of is equal to at least 50 mg / l and at most 6000 mg / l, in processes 40 and 50. It has been found that, when this is the case, the catalyst 59 for the electrolysis of water is produced rapidly.

[0066] In methods 40 and 50, the aqueous medium 58 is a growth medium for the sulfate-reducing microorganism species.

[0067] According to one possibility in methods 40 and 50, the aqueous medium 58 contains organic waste comprising the compound comprising sulfur.

[0068] In methods 40 and 50, the compound comprising sulfur is the sulfate ion (SO42'.

[0069] In processes 40 and 50, the cleaning water used in step 45 and in step 55 is distilled water.

[0070] Each of the electrodes visible in [Fig. 4] is according to an embodiment of the invention. Each of the electrodes visible in [Fig. 4] comprises an outer layer comprising the catalyst 59 for the electrolysis of water, as well as an electrically conductive part carrying the outer layer. In the embodiment of [Fig. 4], this electrically conductive part is made of the material 57. The catalyst 59 comprises a chemical compound comprising at least one metal and sulfur. In the embodiment of [Fig.4], this metal of the catalyst 59 is the metal of the material 57.

[0071] In the embodiment of [Fig.4], the outer layer comprising the catalyst 59 for the electrolysis of water is porous.

[0072] In the embodiment of [Fig.4], the metal of the catalyst 59 and of the material 57 is chosen from the metals of groups 3 to 16 of the periodic table, with the exception of the eight noble metals which are gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os) and iridium (Ir).

[0073] In the embodiment of [Fig.4], the metal of the catalyst 59 and of the material 57 is chosen from nickel (Ni), iron (Fe), copper (Cu), zinc (Zn), bismuth (Bi), manganese (Mn), palladium (Pb), tin (Sn) and indium (In).

[0074] Example 1

[0075] In a first example of implementation of the method 50, the material 57 of an electrode 56 was unalloyed nickel (Ni), i.e. not part of an alloy.

[0076] In the first example of implementation of the method 50, the aqueous medium 58 was obtained by adding sodium sulfate (Na2SO4) and at least one species of sulfate-reducing microorganism chosen from the bacteria: - bacillus cereus, - shewanella xiamenensis, - comamonas testosteroni, - sphingomonas dessicabilis and / or - bacillus tropicus, to distilled water, then subjecting the whole to mixing. In the first example of implementation of the method 50, the aqueous medium 58 thus contains only one species of sulfate-reducing microorganism.

[0077] As measured at 27°C for three days according to the methodology defined by Indian Standard 1S 3025 (Part 44) including Amendment No. 1 of October 2000, and also called "1S 3025 (PART 44), 1993 METHODS OF SAMPLING AND TEST (PHYSICAL AND CHEMICAL) FOR WATER AND WASTEWATER -PART 44 BIOCHEMICAL OXYGEN DEMAND (BOD)", the biochemical oxygen demand due to sulfate-reducing microorganisms in the aqueous medium 58 was of the order of 100 mg / l, in the first example of implementation of the method 50.

[0078] In the first example of implementation of the method 50, the aqueous medium 58 was a growth medium for one of the bacteria listed above thanks to the sulfate ions (SO42) coming from a dissolution of sodium sulfate (Na2SO4) in distilled water. In the first example of implementation of the method 50, the medium aqueous 58 contained about 4 to 5 g of sodium sulfate (Na2SO4) per liter of distilled water, at room temperature.

[0079] In the first example of implementation of the method 50, step 54 was carried out by immersing at least a portion of the electrode 56 in the aqueous medium 58, as illustrated in [Fig.4].

[0080] In the first example of implementation of the method 50, the material 57 was left at least partially immersed in the aqueous medium 58 for a period ranging from 1 to 7 days depending on the size of the electrodes 56.

[0081] In the first example of implementation of the method 50, the electrode 56 was cleaned with distilled water in step 55.

[0082] [Fig. 5] is an image of a surface of the nickel electrode 56 whose nickel is bare before step 54. [Fig. 6] is an image of a surface of the treated electrode 56, which is the same electrode as [Fig. 5] except that steps 54 and 55 of the first example of implementation of the method 50 have been applied to it.

[0083] The image in [Fig.5] and the image in [Fig.6] were obtained under identical conditions, using a scanning electron microscope (SEM).

[0084] A comparison of Figures 5 and 6 shows that globular agglomerates of a size less than 100 nm were formed at the surface of the electrode 56, during step 54 of the first example of implementation of the method 50, on the Nickel part which was left immersed in the aqueous medium 58 during this step 54.

[0085] [Fig. 7] is an image of a cross-section of the treated electrode 56 (also visible in [Fig. 6]), to which steps 54 and 55 of the first example of implementation of the method 50 have been applied. The image of [Fig. 7] was obtained by a scanning electron microscope (SEM).

[0086] A study was carried out using a focused ion beam (called "Focused Ion Beam" in English and also designated by the English acronym "FIB") on the cross-section of [Fig.7]. The study carried out using the focused ion beam on the cross-section of [Fig.7] confirms that the nickel core 70 of the treated electrode 56 carries a porous layer 71. The layer 71 has a thickness of the order of 80 nm.

[0087] [Fig. 8] is an image of an outer surface of the treated electrode 56 (also visible in FIGS. 6 and 7), to which steps 54 and 55 of the first example of implementation of the method 50 have been applied. The image of [Fig. 8] was obtained by 2D atomic force microscopy (called “2D atomic force microscopy” in English and also designated by the English acronym “AFM”).

[0088] 2D atomic force microscopy study confirmed that layer 71 is composed of globular nanoparticles.

[0089] X-ray photoelectron spectroscopy was performed on the bare nickel of electrode 56 of [Fig. 5] and on the treated electrode 56 of [Fig. 6] (also visible in Figures 7 and 8), to which steps 54 and 55 of the first example of implementation of method 50 were applied. [Fig. 9] is a graph that was obtained by means of this X-ray photoelectron spectroscopy.

[0090] As can be seen in [Fig.9], the X-ray photoelectron spectroscopy carried out on the treated electrode 56 of [Fig.6] shows the presence of nickel (Ni) and sulfur (S) in the porous layer 71 carried by the nickel core 70 of the treated electrode 56.

[0091] Raman spectroscopy was performed on the bare nickel of electrode 56 of [Fig. 5] and on the treated electrode 56 of [Fig. 6] (also visible in Figures 7 and 8), to which steps 54 and 55 of the first example of implementation of method 50 were applied. [Fig. 10] is a graph that was obtained by means of this Raman spectroscopy.

[0092] As can be seen in [Fig. 10], the Raman spectroscopy carried out on the treated electrode 56 of [Fig.6] shows the existence of six bands corresponding to vibration modes of rhombohedral Ni3S2.

[0093] Figures 9 and 10 show that the porous layer 71 is made of Ni3S2 coating the nickel of the core 70 of the treated electrode 56. The Ni3S2 is a nickel sulfide. The Ni3S2 is a catalyst for the electrolysis of water. The Ni3S2 of the porous layer 71 is the catalyst 59, which is porous in Example 1.

[0094] Example 2

[0095] In a second example of implementation of the method 50, the material 57 of an electrode 56 was unalloyed nickel (Ni), i.e. not part of an alloy.

[0096] In a second example of implementation of the method 50, the aqueous medium 58 was unfiltered organically loaded water and contained organic waste and the sulfate ion (SO42) originating from this organic waste. More precisely, this unfiltered organically loaded water was here domestic wastewater.

[0097] In the second example of implementation of the method 50, the aqueous medium 58 contained five different species of sulfate-reducing microorganisms, including at least one species of sulfate-reducing microorganism chosen from the bacteria: - bacillus cereus, - shewanella xiamenensis, - comamonas testosteroni, - sphingomonas dessicabilis and / or - bacillus tropicus.

[0098] In the second example of implementation of method 50, the unfiltered wastewater with organic load contained these five different species of sulfate-reducing microorganisms, which were therefore not added.

[0099] For the rest, method 50 was implemented in the second example as it was in the first example.

[0100] Like the first example of implementation of the method 50, the second example of implementation of the method 50 led to the development of a porous layer 71 on the nickel of the core 70. In the second example of implementation of the method 50 as in the first example of implementation of the method 50, this porous layer 71 comprised Ni3S2 and was carried by the nickel of the core 70 of the treated electrode 56.

[0101] Electrolysis

[0102] In [Fig. 11], a use 80 according to an embodiment of the invention is a use of an electrode for water electrolysis.

[0103] In a step 81 of the use 80, the electrode for the electrolysis of water is provided, which is a first electrode for the electrolysis of water. Still in a step 81 of the use 80, at least one second electrode for the electrolysis of water is provided. In [Fig. 12], each of the first and second electrodes for the electrolysis of water is referenced 86.

[0104] In use 80, each of the first and second electrodes 86 is according to one embodiment of the invention. Each electrode 86 locally comprises an outer layer comprising a catalyst for the electrolysis of water, as well as an electrically conductive portion carrying the outer layer. This catalyst comprises a chemical compound comprising at least one metal and sulfur. In use 80, the catalyst for the electrolysis of water is catalyst 59. In use 80, the electrically conductive portion carrying the outer layer is made of material 57.

[0105] According to a variant embodiment of the invention not shown, only one of the electrodes 86 is according to an embodiment of the invention.

[0106] In use 80, the outer layer is porous.

[0107] In use 80, the metal of the chemical compound of the catalyst is chosen from metals in groups 3 to 16 of the periodic table, with the exception of the eight noble metals: gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os) and iridium (Ir).

[0108] In use 80, each of the first and second electrodes 86 is manufactured using the manufacturing method 50 so that the outer layer of the electrode is the layer produced in step 54. According to a variant embodiment of the invention, not shown, only one of the electrodes 86 is manufactured using the manufacturing method 50 such that its outer layer is the layer produced in step 54.

[0109] In a step 82 of the use 80, an aqueous electrolytic solution is provided.

[0110] The use 80 comprises a step 83 of electrolyzing water from the aqueous electrolytic solution. [Fig. 12] illustrates an implementation of step 83. In [Fig. 12], the aqueous electrolytic solution is referenced 87.

[0111] In step 83 of use 80, a voltage or current source 89 generates an electric current in the aqueous electrolytic solution 87, between the first and second electrodes 86.

[0112] A step 84 of the use 80 follows step 83. In step 84, dihydrogen and / or oxyhydrogen 88 produced in step 83 is collected. In a variant of step 84, not shown, only dihydrogen produced in step 83 is collected.

[0113] According to one possibility in use 80, the aqueous electrolytic solution 87 contains at least one electrolyte such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). According to one possibility in use 80, the aqueous electrolytic solution 87 is basic.

[0114] In use 80, the aqueous electrolytic solution 87 contains at least one species of living or dead sulfate-reducing microorganism.

[0115] In use 80, the aqueous electrolytic solution 87 more precisely contains at least the living or dead sulfate-reducing bacteria. It has been found that, when this is the case, less electrical energy is used in step 83 to produce the same amount of oxyhydrogen 88, compared to the case where the aqueous electrolytic solution 87 does not contain a sulfate-reducing microorganism.

[0116] In use 80, the aqueous electrolytic solution 87 contains several species of living or dead sulfate-reducing bacteria. In use 80, the aqueous electrolytic solution 87 contains exactly five species of sulfate-reducing bacteria.

[0117] According to one possibility in the use 80, the water of the aqueous electrolytic solution 87 is water filtered to ten microns or less, for example produced by filtration of natural fresh surface water such as river water or lake water. When this is the case, the sulfate-reducing microorganism(s) are added to the water filtered to ten microns or less. Sodium hydroxide (NaOH) and / or potassium hydroxide (KOH) may also be added to the water filtered to ten microns or less.

[0118] According to one possibility in the use 80, the water of the aqueous electrolytic solution 87 is or comprises water with an organic charge filtered between ten microns and twenty microns, for example produced from wastewater of domestic, agricultural and / or urban origin. According to one possibility in the use 80, the water with an organic charge organic filtered between ten and twenty microns contains the sulfate-reducing microorganism(s), which can then not be added.

[0119] As measured at 27°C for three days according to the methodology defined by Indian Standard 1S 3025 (Part 44) including Amendment No. 1 of October 2000, and also referred to as "1S 3025 (PART 44), 1993 METHODS OF SAMPLING AND TEST (PHYSICAL AND CHEMICAL) FOR WATER AND WASTEWATER - PART 44 BIOCHEMICAL OXYGEN DEMAND (BOD)", the biochemical oxygen demand due to sulfate-reducing microorganisms in the aqueous electrolytic solution 87 is at least 10 mg / l and at most 50 mg / l, in use 80. It has been found that, when this is the case, less electrical energy is used in step 83 to produce the same amount of oxyhydrogen 88, compared to the case where the biochemical oxygen demand due to the microorganisms sulfate-reducing agents in the aqueous electrolytic solution 87 is outside this range.The biochemical oxygen demand due to the sulfate-reducing microorganisms in the aqueous electrolytic solution 87 is measured when the sulfate-reducing microorganisms are substantially all alive. In the electrolysis step 83, the sulfate-reducing microorganisms are either alive or dead. As used herein, the term "dead" applies both to the case where the sulfate-reducing microorganisms are dead and to the case where the sulfate-reducing microorganisms are dying.

[0120] Example Ibis

[0121] In a first example Ibis of implementation of the use 80, the first and second electrodes 86 used were the treated electrodes 56 which had been manufactured according to the first example of implementation of the method 50.

[0122] In the first example of implementation of use 80, the aqueous electrolytic solution 87 was obtained by adding potassium hydroxide (KOH) and an initially living sulfa-reducing bacterium to distilled water, then subjecting the whole to mixing.

[0123] As measured at 27°C for three days according to the methodology defined by Indian Standard 1S 3025 (Part 44) including Amendment No. 1 of October 2000, and also called "1S 3025 (PART 44), 1993 METHODS OF SAMPLING AND TEST (PHYSICAL AND CHEMICAL) FOR WATER AND WASTEWATER - PART 44 BIOCHEMICAL OXYGEN DEMAND (BOD)", the biochemical oxygen demand due to sulfate-reducing microorganisms in the aqueous electrolytic solution 87 was of the order of 20 mg / l, in the first example of implementation of use 80.

[0124] In the first example of implementation of use 80, the aqueous electrolytic solution 87 contained 5 g of sodium hydroxide (NaOH) per liter of distilled water, at room temperature.

[0125] In step 83 of electrolysis of water from aqueous electrolytic solution 87, the sulfate-reducing bacteria in this aqueous electrolytic solution 87 was either alive or dead.

[0126] In the first example of implementation of use 80, the power consumed by the electrolysis and the volume of oxyhydrogen produced per minute by the electrolysis were measured, this volume being measured at atmospheric pressure and at a temperature of the order of 25°C. From the measurements carried out, the electrical energy consumed to produce one kilogram of dihydrogen was calculated.

[0127] Example 2bis

[0128] In a comparison example 2bis which is a second example of implementation of use 80, the aqueous electrolytic solution 87 was replaced by distilled water, which did not contain any sulfate-reducing microorganisms.

[0129] For the rest, the use 80 was implemented in the second example of implementation of the use 80 as it was in the first example of implementation of the use 80. In particular, in the second example of implementation of the use 80, the first and second electrodes 86 used were the treated electrodes 56 which had been manufactured according to the first example of implementation of the method 50.

[0130] In the second example of implementation of use 80, the power consumed by the electrolysis and the volume of oxyhydrogen produced per minute by the electrolysis were measured, this volume being measured at atmospheric pressure and at a temperature of the order of 25°C. From the measurements carried out, the electrical energy consumed to produce one kilogram of dihydrogen was calculated.

[0131] The results obtained by the first and second examples of implementation of use 80 are indicated in Table 1 below:

[0132] [Tables 1] aqueous electrolytic solution Power consumed (W) Production of oxyhydrogen (liters per minute) Example 1bis Distilled water + KOH + Sulfate-reducing bacteria 69.12 0.807 Example 2bis Distilled water 67.34 0.433 I_________________________________________________________________________________________________________________I_________________________________________________________________________________I__________________________________________________________________________________________________I

[0133] It is noted that the energy yield of the production of hydrogen by water electrolysis in the case where the aqueous electrolytic solution 87 contains the sulfate-reducing bacteria is much higher than the energy yield of the production of hydrogen by water electrolysis in the case where the aqueous electrolytic solution 87 consists of distilled water, without sulfate-reducing microorganism.

[0134] Example 3

[0135] In a third example of implementation of use 80, the aqueous electrolytic solution 87 was an organically charged water filtered between ten microns and twenty microns and contained organic waste and the sulfate ion (SO42) originating from this organic waste.

[0136] In the third example of implementation of use 80, the aqueous electrolytic solution 87 contained five different species of sulfate-reducing microorganisms, including the sulfate-reducing bacterium. In the third example of implementation of use 80, these five different species of sulfate-reducing microorganisms were not added, because they were present in the organically charged water filtered between ten and twenty microns which was used, that is to say hydrolyzed.

[0137] For the rest, the use 80 was implemented in the third example of implementation of the use 80 as it was in the first example of implementation of the use 80. In particular, in the third example of implementation of the use 80, the first and second electrodes 86 used were the treated electrodes 56 which had been manufactured according to the first example of implementation of the method 50.

[0138] It has been found that the energy yield of hydrogen production by water electrolysis in the case where the aqueous electrolytic solution 87 is organically charged water filtered to between ten and twenty microns, containing organic waste and sulfate-reducing bacteria, is much higher than the energy yield of hydrogen production by water electrolysis in the case where the aqueous electrolytic solution 87 is replaced by distilled water without sulfate-reducing microorganism.

[0139] In the third example of implementation of the use 80 as in the second example of implementation of the use 80, the energy yield of the production of hydrogen by electrolysis in the case where the aqueous electrolytic solution 87 contains the sulfate-reducing bacteria is much higher than the energy yield of the production of hydrogen by electrolysis in the case where the solution aqueous electrolytic 87 is replaced by distilled water without sulfate-reducing microorganisms.

[0140] It has further been found that the first and second electrodes 86 manufactured according to the first example of implementation of the method 50 do not deteriorate or almost do not deteriorate during use for electrolyzing water with an organic charge filtered between ten microns and twenty microns for a period of at least 30 days. An electrode manufactured according to the first example of implementation of the method 50 is therefore particularly robust, including in uses for electrolyzing water with an organic charge filtered between ten microns and twenty microns, containing organic waste and microorganisms. Statement of the invention

[0141] The invention has at least the aim that a catalyst for the electrolysis of water can be produced at low cost.

[0142] According to the invention, this aim is achieved by means of a process for producing a catalyst for the electrolysis of water, which comprises at least one step in which:

[0143] a) a material comprising at least one metal is brought into contact with an aqueous medium containing at least one species of sulfate-reducing microorganism and at least one compound comprising sulfur (S).

[0144] Producing dihydrogen and / or dioxygen by electrolysis of water is more efficient and / or requires less energy and / or is faster in the presence of the catalyst produced by implementing the process according to the invention.

[0145] The production process according to the invention has a first advantage, namely that it is capable of not being polluting.

[0146] The production method according to the invention has a second advantage, namely that it is capable of not consuming energy.

[0147] Organic waste may be the source of the compound comprising sulfur. In the process according to the invention, it is therefore possible to use and / or recycle water comprising this organic waste. The water comprising the organic waste may comprise unfiltered organic-laden water such as domestic wastewater or agricultural wastewater. The production process according to the invention therefore has a third advantage, namely that it is capable of not consuming chemical products which have been synthesized and / or extracted by mining extraction techniques.

[0148] The production process according to the invention has a fourth advantage, namely that it is compatible with sustainable development.

[0149] The production process according to the invention has a fifth advantage, namely that it is possible to recycle and / or reuse unfiltered water with an organic load, such as wastewater of domestic, urban and / or agricultural origin. In this regard, it should be noted that human activities generate immense quantities of wastewater from domestic and agricultural sources.

[0150] The production process defined above may incorporate one or more other advantageous characteristics, individually or in combination, in particular among those defined below.

[0151] According to an advantageous possibility, the metal is chosen from the metals of groups 3 to 16 of the periodic table, with the exception of the eight noble metals which are gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os) and iridium (Ir).

[0152] According to an advantageous possibility, the metal is chosen from the metals of groups 4 to 16 of the periodic table and / or groups 5 to 16 of the periodic table and / or groups 3 to 12 of the periodic table, with the exception of the eight noble metals which are gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os) and iridium (Ir).

[0153] According to an advantageous possibility, the metal is chosen from nickel (Ni), iron (Fe), copper (Cu), zinc (Zn), bismuth (Bi), manganese (Mn), palladium (Pb), tin (Sn) and indium (In).

[0154] According to an advantageous possibility, the metal is nickel (Ni).

[0155] According to an advantageous possibility, at least a part of the material consists of the metal, which is unalloyed.

[0156] According to an advantageous possibility, at least a portion of the material is made of an alloy comprising the metal.

[0157] According to an advantageous possibility, the sulfate-reducing microorganism species is a sulfate-reducing bacterium.

[0158] According to an advantageous possibility, the species of sulfate-reducing microorganism is a Gram-negative bacterium.

[0159] According to an advantageous possibility, the species of sulfate-reducing microorganism is a bacterium belonging to the phylum Firmicutes, Pseudomonadota or Bacillota.

[0160] According to an advantageous possibility, the species of sulfate-reducing microorganism is a bacterium belonging to the class of bacilli, gammaproteobacteria, betaproteobacteria or alphaproteobacteria.

[0161] According to an advantageous possibility, the species of sulfate-reducing microorganism is a bacterium belonging to the order Bacillales, Alteromonadales, Burkholderiales, Sphingomonadales or Caryophanales.

[0162] According to an advantageous possibility, the species of sulfate-reducing microorganism is a bacterium belonging to the family of Bacillaceae, Shewanellaceae, Comamonadaceae or Sphingomonadaceae.

[0163] According to an advantageous possibility, the species of sulfate-reducing microorganism is a bacterium belonging to the genus Bacillus, Shewanella, Comamonas or Sphingomonas.

[0164] Thus, the catalyst for water electrolysis is produced rapidly.

[0165] According to an advantageous possibility, the aqueous medium contains several different species of sulfate-reducing bacteria.

[0166] According to an advantageous possibility, the production method comprises a step which precedes step a) and in which: - the material is subjected at least locally to ultrasonic cleaning.

[0167] According to an advantageous possibility, as measured at 27°C for three days according to the methodology defined by Indian Standard 1S 3025 (Part 44) including Amendment No. 1 of October 2000, and also called "1S 3025 (PART 44), 1993 METHODS OF SAMPLING AND TEST (PHYSICAL AND CHEMICAL) FOR WATER AND WASTEWATER - PART 44 BIOCHEMICAL OXYGEN DEMAND (BOD)", the biochemical oxygen demand due to sulfate-reducing microorganisms in the aqueous medium is equal to at least 50 mg / l and at most 6000 mg / l.

[0168] Thus, the catalyst for water electrolysis is produced more quickly.

[0169] According to an advantageous possibility, as measured at 27°C for three days according to the methodology defined by the Indian standard 1S 3025 (Part 44) including Amendment No. 1 of October 2000, and also called "1S 3025 (PART 44), 1993 METHODS OF SAMPLING AND TEST (PHYSICAL AND CHEMICAL) FOR WATER AND WASTEWATER - PART 44 BIOCHEMICAL OXYGEN DEMAND (BOD)", the biochemical oxygen demand due to sulfate-reducing microorganisms in the aqueous medium is of the order of 100 mg / l.

[0170] Thus, the catalyst for water electrolysis is produced even faster.

[0171] According to an advantageous possibility, the aqueous medium is a growth medium for the species of sulfate-reducing microorganism.

[0172] According to an advantageous possibility, the aqueous medium contains organic waste at the origin of the compound comprising sulfur.

[0173] According to an advantageous possibility, the compound comprising sulfur is the sulfate ion (SO42).

[0174] According to one possibility, the water of the aqueous medium comprises and / or is water filtered to ten microns or less, unfiltered organically loaded water and / or organically loaded water filtered between ten microns and twenty microns.

[0175] According to one possibility, the water of the aqueous medium comprises and / or is unfiltered organically loaded water, such as wastewater of domestic and / or agricultural origin.

[0176] According to one possibility, the unfiltered organic-loaded water contains the sulfate-reducing microorganism species.

[0177] According to an advantageous possibility, the catalyst is porous.

[0178] The invention also relates to a method for manufacturing an electrode for the electrolysis of water, which comprises a production method as defined above, the electrode comprising the material comprising the metal, step a) being carried out to produce a layer comprising the catalyst, on at least part of the material comprising the metal.

[0179] The manufacturing method according to the invention has the advantage of making it possible to manufacture a particularly robust electrode, which does not degrade or only slightly during its use, including in uses of the electrode for electrolyzing water filtered to ten microns or less and / or water with an organic charge filtered between ten microns and twenty microns, containing organic waste and microorganisms. The manufacturing method according to the invention has the further advantage of making it possible to manufacture an electrode provided with the catalyst in a layer which is particularly robust.

[0180] The manufacturing method defined above may incorporate one or more other advantageous characteristics, alone or in combination, in particular among those defined below.

[0181] According to an advantageous possibility, the layer comprising the catalyst is porous.

[0182] According to an advantageous possibility, in step a), at least a part is immersed of the electrode in the aqueous medium.

[0183] According to an advantageous possibility, the manufacturing method comprises a step which follows step a) and in which: - the electrode is cleaned with cleaning water.

[0184] According to an advantageous possibility, the cleaning water is distilled water.

[0185] The invention also relates to an electrode for the electrolysis of water, which, at least locally, comprises an outer layer comprising a catalyst for the electrolysis of water, the catalyst comprising a chemical compound comprising at least one metal and sulfur, the electrode comprising an electrically conductive part carrying the outer layer.

[0186] The use of an electrode according to the invention to produce dihydrogen and / or dioxygen by electrolysis of water is more efficient and / or requires less energy and / or is faster.

[0187] The electrode defined above may incorporate one or more other advantageous characteristics, in isolation or in combination, in particular among those defined below.

[0188] According to an advantageous possibility, the electrically conductive part carrying the outer layer is made of a material comprising metal.

[0189] According to an advantageous possibility, the outer layer is porous.

[0190] According to an advantageous possibility, the metal is chosen from the metals of groups 3 to 16 of the periodic table, with the exception of the eight noble metals which are gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os) and iridium (Ir).

[0191] According to an advantageous possibility, the metal is chosen from the metals of groups 4 to 16 of the periodic table and / or groups 5 to 16 of the periodic table and / or groups 3 to 12 of the periodic table, with the exception of the eight noble metals which are gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os) and iridium (Ir).

[0192] According to an advantageous possibility, the metal is chosen from nickel (Ni), iron (Fe), copper (Cu), zinc (Zn), bismuth (Bi), manganese (Mn), palladium (Pb), tin (Sn) and indium (In).

[0193] According to an advantageous possibility, the metal is nickel (Ni).

[0194] According to an advantageous possibility, the catalyst comprises a nickel sulfide.

[0195] According to an advantageous possibility, the nickel sulfide is in the form Ni3S2.

[0196] According to an advantageous possibility, the electrode is able to be manufactured by means of of the manufacturing process as defined above so that the outer layer of the electrode is the layer produced in step a).

[0197] The invention also relates to a use of an electrode as defined above, which comprises an electrolysis step in which:

[0198] b) an electric current is passed through an aqueous electrolytic solution, at least between the electrode and another electrode.

[0199] The electrolysis of water present in the aqueous electrolytic solution produces dihydrogen (H2) and dioxygen (O2).

[0200] The use according to the invention has a first advantage, namely that it is possible to recycle and / or reuse wastewater of domestic and / or agricultural origin. In this regard, it will be noted that human activities generate immense quantities of wastewater of domestic and agricultural origin.

[0201] According to an advantageous possibility, the water of the aqueous electrolytic solution comprises and / or is water with an organic charge filtered between ten microns and twenty microns, for example produced by filtration of waste water of domestic and / or agricultural origin.

[0202] Natural fresh surface water such as river water or lake water is available in large quantities in certain non-arid regions of the world. Furthermore, it is inexpensive or even free in certain non-arid regions of the world. The use according to the invention has a second advantage, namely that natural fresh surface water such as river water or lake water can be used.

[0203] According to an advantageous possibility, the water of the aqueous electrolytic solution comprises and / or is water filtered to ten microns or less, for example produced by filtration of natural surface fresh water such as river water or lake water.

[0204] The production method according to the invention has a third advantage, namely that it is compatible with sustainable development. In particular, the electrical power consumed in step b) can be produced by converting wind energy, solar energy and / or hydraulic energy and / or in another manner not accompanied by the release of carbon dioxide into the Earth's atmosphere.

[0205] The use defined above may incorporate one or more other advantageous characteristics, alone or in combination, in particular among those defined below.

[0206] According to an advantageous possibility, the use comprises a step in which:

[0207] c) dihydrogen and / or dioxygen and / or oxyhydrogen produced in step b) are collected.

[0208] According to an advantageous possibility, the aqueous electrolytic solution contains at least one species of living or dead sulfate-reducing microorganism.

[0209] Thus, it is possible to produce dihydrogen and / or dioxygen with less energy by electrolysis of water.

[0210] According to an advantageous possibility, the water of the aqueous electrolytic solution comprises and / or is water filtered to ten microns or less and / or water with an organic charge filtered between ten microns and twenty microns.

[0211] Thus, the water for the aqueous electrolytic solution can be produced from water available in large quantities and at low cost or even free of charge.

[0212] According to one possibility, the water of the aqueous electrolytic solution comprises and / or is water filtered to ten microns or less, for example produced by filtration of natural surface fresh water such as river water or lake water.

[0213] According to one possibility, the sulfate-reducing microorganisms in the aqueous electrolytic solution are dead during at least part of step b).

[0214] According to an advantageous possibility, the species of sulfate-reducing microorganism in the aqueous electrolytic solution or one of the species of sulfate-reducing microorganisms in the aqueous electrolytic solution is a sulfate-reducing bacterium.

[0215] According to an advantageous possibility, the species of sulfate-reducing microorganism in the aqueous electrolyte solution or one of the species of sulfate-reducing microorganisms in the aqueous electrolyte solution is a Gram-negative bacterium.

[0216] According to an advantageous possibility, the species of sulfate-reducing microorganism in the aqueous electrolytic solution or one of the species of sulfate-reducing microorganisms in the aqueous electrolytic solution is a bacterium belonging to the family Enterobacteriaceae.

[0217] Thus, it is possible to produce dihydrogen and / or dioxygen with even less energy by electrolysis of water.

[0218] According to an advantageous possibility, the aqueous electrolytic solution contains several species of sulfate-reducing bacteria.

[0219] According to an advantageous possibility, as measured at 27°C for three days according to the methodology defined by Indian Standard 1S 3025 (Part 44) including Amendment No. 1 of October 2000, and also called "1S 3025 (PART 44), 1993 METHODS OF SAMPLING AND TEST (PHYSICAL AND CHEMICAL) FOR WATER AND WASTEWATER - PART 44 BIOCHEMICAL OXYGEN DEMAND (BOD)", the biochemical oxygen demand due to sulfate-reducing microorganisms in the aqueous electrolytic solution is equal to at least 10 mg / l and at most 50 mg / l.

[0220] Thus, it is possible to produce dihydrogen and / or dioxygen with even less energy by electrolysis of water. The biochemical oxygen demand due to the sulfate-reducing microorganisms in the aqueous electrolytic solution is measured when the sulfate-reducing microorganisms are substantially all alive, even if they are no longer alive or do not remain alive in step b).

[0221] According to an advantageous possibility, as measured at 27°C for three days according to the methodology defined by Indian Standard 1S 3025 (Part 44) including Amendment No. 1 of October 2000, and also called "1S 3025 (PART 44), 1993 METHODS OF SAMPLING AND TEST (PHYSICAL AND CHEMICAL) FOR WATER AND WASTEWATER - PART 44 BIOCHEMICAL OXYGEN DEMAND (BOD)", the biochemical oxygen demand due to sulfate-reducing microorganisms in the aqueous electrolytic solution is of the order of 20 mg / l.

[0222] Thus, it is possible to produce dihydrogen and / or dioxygen with even less energy by electrolysis of water.

[0223] According to an advantageous possibility, the aqueous electrolytic solution contains at least one electrolyte such as sodium hydroxide (NaOH) or potassium hydroxide (KOH).

Claims

Claims

1. Method for producing a catalyst (59) for the electrolysis of water, characterized in that it comprises at least one step (44; 54) in which: a) a material (57) comprising at least one metal is brought into contact with an aqueous medium (58) containing at least one species of sulfate-reducing microorganism and at least one compound comprising sulfur (S).

2. A production method according to claim 1, wherein the metal is selected from metals of groups 3 to 16 of the periodic table, with the exception of the eight noble metals of gold (Au), platinum (Pt), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os) and iridium (Ir).

3. Production method according to one of claims 1 and 2, in which the metal is nickel (Ni).

4. Production process according to one of claims 1 to 3, in which at least one species of sulfate-reducing microorganism is chosen from the bacteria: - bacillus cereus, - shewanella xiamenensis, - comamonas testosteroni, - sphingomonas dessicabilis and / or - bacillus tropicus.

5. A production method according to any one of claims 1 to 4, wherein, as measured at 27°C for three days according to the methodology defined by Indian Standard 1S 3025 (Part 44) including Amendment No. 1 of October 2000, and also referred to as "1S 3025 (PART 44), 1993 METHODS OF SAMPLING AND TEST (PHYSICAL AND CHEMICAL) FOR WATER AND WASTEWATER - PART 44 BIOCHEMICAL OXYGEN DEMAND (BOD)", the biochemical oxygen demand due to sulfate-reducing microorganisms in the aqueous medium (58) is at least 50 mg / l and at most 6000 mg / l.

6. A method of manufacturing an electrode (16; 56; 86) for the electrolysis of water, characterized in that it comprises a production method according to one of claims 1 to 5, the electrode (16; 56; 86) comprising the material (57) comprising the metal, the step a) being carried out to produce a layer comprising the catalyst (59), on at least a portion of the material (57) comprising the metal.

7. Electrode for the electrolysis of water, characterized in that, at least locally, it comprises an outer layer comprising a catalyst (59) for the electrolysis of water, the catalyst (59) comprising a chemical compound comprising at least one metal and sulfur, the electrode (16; 56; 86) comprising an electrically conductive part (57) carrying the outer layer.

8. An electrode according to claim 7, wherein the catalyst (59) comprises a nickel sulfide in the form Ni3S2.

9. Electrode according to one of claims 7 and 8, which is capable of being manufactured by means of the manufacturing method (50) according to one of claims 6 and 7 so that the outer layer of the electrode (16; 56; 86) is the layer produced in step a).

10. Use of an electrode (16; 56; 86) according to one of claims 8 and 9, which comprises an electrolysis step (83) in which: b) an electric current is passed through an aqueous electrolytic solution (87), at least between the electrode (16; 56; 86) and another electrode, in which the aqueous electrolytic solution (87) contains at least one species of living or dead sulfate-reducing microorganism.

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