METHOD FOR PRODUCING GRAPHITE-CONTAINING METAL OXIDE ELECTRODE, USE OF GRAPHITE-CONTAINING METAL OXIDE ELECTRODE, AND ELECTROLYSIS CELL

Abstract

The present invention relates to a method for producing a graphite-containing metal oxide electrode, comprising the steps of: a) providing (1) an electrolytic cell (10) having an electrode (11), a further electrode (12) and an aqueous and / or non-aqueous carbonyl- and cyano-free solvent (14), b) introducing (2) a black mass (15) containing a graphite-supported noble-metal-free metal oxide and a proton source into the solvent (14) present in the electrolytic cell (10), and c) applying (3) a voltage to the electrode (11) and the further electrode (12), such that the noble-metal-free metal oxide and graphite provided by the black mass (15) are deposited on the electrode (11) to produce a graphite-containing metal oxide coating (17) on the electrode (11) for forming a graphite-containing metal oxide electrode. The present invention further relates to a graphite-containing metal oxide electrode produced by this method. The present invention further relates to the use of a graphite-containing metal oxide electrode for the production of hydrogen and / or oxygen by electrochemical water splitting (photoelectrochemical water splitting) and to an electrolysis cell (20) for the production of hydrogen and oxygen by electrochemical water splitting (photoelectrochemical water splitting), the electrolysis cell (20) comprising a graphite-containing metal oxide electrode as cathode (22) and / or a graphite-containing metal oxide electrode as anode (21).

Description

[Technical field]

[0001] The present invention relates to a method for producing a graphite-containing metal oxide electrode, a graphite-containing metal oxide electrode, uses of the graphite-containing metal oxide electrode, and electrolysis cells. In particular, the present invention relates to a facile method for producing a graphite-containing metal oxide electrode, a graphite-containing metal oxide electrode produced by this method, uses of the graphite-containing metal oxide electrode for electrochemically producing hydrogen and / or oxygen, and electrolysis cells configured to produce hydrogen and oxygen using the graphite-containing metal oxide electrode. [Background technology]

[0002] A known method for producing a carbon-containing metal oxide electrode is described in WO2015 / 082626A1, which describes a method for producing a metal chalcogenide thin film electrode.

[0003] The method for producing the metal chalcogenide thin film electrode includes the steps of: (a) contacting a metal or metal oxide with an elemental halogen in a non-aqueous solvent to produce a metal halide compound in solution; (b) applying a negative voltage to a conductive or semiconductive substrate in contact with the solution from step (a); (c) contacting the substrate with an elemental chalcogen during and / or after step (b) to form a metal chalcogenide layer on the substrate; Includes.

[0004] In this method, metals capable of forming metal halide compounds in which the metal is in an oxidation state of +2 or higher are used, in particular Fe, Co, Ni, Cr, Mn or mixtures or alloys thereof. The halogen is in particular iodine or bromine. The chalcogen is in particular O2, S or Se. The non-aqueous solvent used is preferably an organic solvent containing a carbonyl group (CO) or a cyano group (CN). The metal chalcogenide thin film electrode produced by this method can be used for electrochemical water splitting (photoelectrochemical water splitting), in particular as an electrode for oxygen evolution for electrochemical water splitting under an external potential or under illumination. However, this method is complicated because it is necessary to first generate a precursor for deposition. There is therefore a need to provide an electrode suitable as an electrode for use in electrochemical water splitting and easy to manufacture. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. WO2015 / 082626 Summary of the Invention [Problem to be solved by the invention]

[0006] It is therefore an object of the present invention to provide a method for the manufacture of electrodes that is easy to implement and results in electrodes suitable for electrochemical use in water splitting. [Means for solving the problem]

[0007] This object is achieved by a method having the features of claim 1, by a graphite-containing metal oxide electrode having the features of claim 7, by the use of a graphite-containing metal oxide electrode having the features of claim 8, and by an electrolytic cell having the features of claim 9. Advantageous developments and modifications are specified in the dependent claims.

[0008] The present invention relates to a method for producing a graphite-containing metal oxide electrode, a) providing an electrolysis cell having an electrode, a further electrode and an aqueous and / or non-aqueous carbonyl- and cyano-free solvent; b) introducing a black mass having a graphite supported noble metal free metal oxide and a proton source into a solvent in an electrolytic cell; c) applying a voltage to the electrode and the further electrode, such that the noble metal-free metal oxide and graphite provided by the black mass are deposited on the electrode to produce a graphite-containing metal oxide coating on the electrode to form a graphite-containing metal oxide electrode; Includes.

[0009] To produce graphite-containing metal oxide electrodes, no precursors for chalcogenide production are used. Rather, metal oxides present in black mass are used directly, optionally modified in terms of their percentage. Carbonyl- and cyano-free solvents are used. Preferably, cyclic ethers such as tetrahydrofuran and azeotropic alcohol water mixtures are used with cell voltages below 10V. Examples of electrode materials include nickel- or steel-based materials.

[0010] Protons are generated from a weakly Bronsted acidic proton source (molecules as solvents with OH, CH and NH groups). The preferred source of protons is based on the reaction of bromine and iodine with the solvent. Alternatively, highly dilute solutions (10 -4 ~10 -6 mol) may be used, which can be generated by adding hydrogen bromide or hydrogen iodide to the solvent. The protons act as a medium to immobilize the catalyst on the electrode.

[0011] In a preferred embodiment, the black mass is a recyclate. The recyclate is preferably a recycled material from used batteries for electrically driving electric vehicles, more preferably electric automobiles. The black mass is a material obtained from used batteries used for electrically driving electric vehicles, more preferably electric automobiles. In particular, the black mass is obtained by mechanical recycling by dismantling used electric automobile batteries to be recycled. Mechanical recycling includes several steps of crushing, sorting and classification of the residues after dismantling the housing and device electronics of the used batteries, from which inter alia the black mass is obtained and processed. The black mass was provided by Duesenfeld GmbH (Wendeburg, Germany). The black mass preferably comprises the layers, electrodes and / or electrolyte materials of used batteries. Preferably, the black mass is a granular mixture. The black mass is preferably enriched with the active materials of the electrodes, such as graphite and mixed oxides of lithium with transition metals such as cobalt, nickel and manganese. However, the composition of black mass depends on the chemical composition of the recycled used batteries. There are various types of batteries for electric vehicle traction, each with a different chemical composition.

[0012] In addition to metals and metal oxides, the black mass contains graphite, which acts as a support for the metals and metal oxides. The black mass preferably contains several metal oxides. The black mass preferably contains mixed metal oxides, such as oxides of Ni, Co and Mn. Alternatively, the black mass preferably contains oxides of Ni, Co and Al. Also alternatively, the black mass preferably contains iron phosphate Fe x (PO4) yThe black mass metal oxide may be composed of mixed Ni, Co, Mn oxides, Ni, Co, Al oxides, or graphite supported iron oxides. The metals (or metal oxides) do not contain precious metals.

[0013] Preferably, the one or more graphite-supported metal oxides comprise a mixture of Ni, Co and / or Mn with at least one of their oxides. The Ni:Mn:Co ratio in the black mass can vary depending on the wet chemical processing method used to remove lithium and other constituents in the cathode, and also depends on the particle size of the black mass after recycling.

[0014] Established materials for lithium batteries for electric vehicles that can be used to produce black mass include LiFePO4, LiMn2O4, Li(Ni,Co,Al)O2, LiNi, as described, for example, in Harper, G. et al. Nature 575, 75-86 (2019). 0.33 Mn 0.33 Co 0.33 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2 and LiNi 0.8 Mn 0.1 Co 0.1 O2. Particularly preferred materials are LiFePO4, Li(Ni,Co,Al)O2, LiNi 0.33 Mn 0.33 Co 0.33 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2, LiNi 0.6 Mn 0.2 Co 0.2 O2 and LiNi 0.8 Mn 0.1 Co 0.1 It's O2.

[0015] Preferably, the black mass used is recycled material from used batteries for electrically driving electric vehicles, as recycled material based on NMC batteries (Lithium Nickel Manganese Cobalt Oxide batteries) from Duesenfeld GmbH (Wendeburg, Germany). This recycled material contains 48.04% by weight C, 16.16% by weight O, 2.91% by weight Ni, 0.52% by weight Co, 0.30% by weight Fe and 32.07% by weight N. The morphology has a micro- and / or nano-structure. The morphology and particle size are non-uniform.

[0016] Alternatively, the black mass used is preferably recycled material from used batteries for electrically driving electric vehicles, as a recycled material based on LFP batteries (lithium iron phosphate batteries) from Duesenfeld GmbH (Wendeburg, Germany). This recycled material contains 31.90% by weight C, 36.87% by weight O, 19.30% by weight Fe and 11.94% by weight P. The morphology has a micro- and / or nano-structure. The morphology and particle size are non-uniform.

[0017] In a preferred embodiment, prior to step a) or step b), determining the composition and morphology of the black mass; a step of chemically modifying the black mass according to the determined composition and morphology, which includes changing the percentage of metals (oxides) present in the black mass; is executed.

[0018] The percentages of elements present in the black mass are preferably predetermined as maximum values ​​by wet chemical processing of the lithium battery cathode material. Since the percentages may vary between different batches and battery types, it is advantageous to determine the exact composition and morphology of the black mass and subsequently chemically modify the black mass to enhance the performance level of the graphite-containing metal oxide electrode produced. Preferably, the predetermined ratio of the proportions of metal oxides present in the black mass is established by chemical modification.

[0019] The composition and morphology of the black mass is known based on data provided by the black mass manufacturer and / or on safety data sheets and / or can be determined by solid state analysis (e.g., X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM)), powder X-ray diffraction (PXRD), and / or wet chemical analysis (e.g., ion chromatography with plasma (ICP)).

[0020] X-ray photoelectron spectroscopy (XPS) can be performed for chemical analysis of black mass and nuclear level lines can be assigned to specific oxidation states using published data such as Chastain & King (Eds.), Handbook of X-Ray Photoelectron Spectroscopy, Physical Electronics, Minnesota, USA, (1995).

[0021] Energy dispersive X-ray analysis (EDX) can be performed globally using averaging over the sample surface of the black mass for chemical elemental analysis, or locally using the lateral resolution of a scanning electron microscope, with excitation energies selected such that the expected elemental specific K or L lines of the elements are detected, for example, between 3 keV and 10 keV. The measured X-rays can be automatically assigned by control software such as NSS 2.2 (Thermo Fisher Scientific, USA) using database values.

[0022] In a preferred embodiment, the chemical modification of the black mass involves changing the percentage of metal (oxide) present in the black mass. In light of the publications by Cao X. et al., ACS Catal. 8, 8273-8289 (2018) and Lu Z. et al., Nat. Commun. 5, 4345 (2014), optimizing the percentage composition of metal oxides seems to be advantageous in the use of mixed ternary metal oxides obtained from recycled Li batteries, i.e. pure metal oxides without graphite.

[0023] Chemical modification includes, for example, the addition of metals (oxides) to obtain an optimal ratio of metals and an optimized surface of the black mass particles. The metals (oxides) used here may be the same as the metals (or metal oxides) already present in the black mass, so that their ratios in the black mass are modified relative to each other. Alternatively or additionally, the metals (oxides) used here may be different metals (oxides) from the metals (or metal oxides) already present in the black mass. The composition of the black mass may be changed by treating the black mass with molecular hydrogen as a reducing agent at 300-400°C, which may result in the partial formation of metal alloys such as NiCo that can be used to increase the water splitting efficiency of the black mass.

[0024] The metal (oxide) added for chemical modification of the black mass may be generated in situ, for example Ni(OAc)2 (nickel(II) acetate) may be added to the black mass and exposed to conditions that result in the decomposition reaction of Ni(OAc)2 to form nickel(II) oxide and nickel.

[0025] It is also possible to modify the black mass by altering the existing metal oxide structure and / or support material by anion / cation exchange under acidic or basic conditions. For example, to effect anion / cation exchange under acidic conditions, the black mass may be heated in an aqueous solution of formic acid and H2O2. Anion / cation exchange under basic conditions may be achieved by heating the black mass in an aqueous solution of KOH.

[0026] The chemical modification of the black mass may further comprise the chemical modification of graphite as a support. For this purpose, prior to step a) or b), preferably: Adding one or more foreign atoms (promoter atoms) to the graphite support of the black mass. is executed.

[0027] The one or more heteroatoms are preferably selected from the group consisting of nitrogen, sulfur, phosphorus and / or boron. More preferably, the one or more heteroatoms are nitrogen and / or sulfur.

[0028] In a preferred embodiment, the heteroatom is nitrogen. The addition of nitrogen to graphite can increase the performance level and current density by at least 50%, for example in the case of electrolytic hydrogen production with Ni / Co / Mn-containing black mass. The addition here can be carried out in amounts ranging from doping to substoichiometric amounts. To add nitrogen to graphite, the black mass is preferably heated at 200°C to 400°C, more preferably 300°C to 350°C, for one or several hours, preferably 1 hour to 10 hours, in a flow of ammonia gas as the nitrogen source. This ensures that the nitrogen is incorporated into the graphite carrier. Evidence of nitrogen in the material can be provided on the basis of XPS (X-ray photoelectron spectroscopy) emission spectra. Alternatively, nitrogen may be added using N2, urea, or hydrazine.

[0029] Alternatively or additionally, the heteroatom is preferably sulfur. The addition of sulfur results in a dramatic increase in the hydrogen production activity of the black mass. The addition of sulfur results in the formation of small amounts of metal sulfides such as NiS, CoS and MnS, which can promote electrolytic hydrogen production if the relevant metals are present in the black mass. Sulfur can be added, for example, using S8 or hydrogen sulfide.

[0030] Sulfur and nitrogen may be added simultaneously by reacting the black mass with thiourea, which acts as both a nitrogen and sulfur source at the same time. For example, 0.1-0.3 wt. % thiourea is used. The reaction may be carried out at 150-200° C. for several hours.

[0031] Alternatively or additionally, the heteroatom is preferably phosphorus, which may be added using, for example, red phosphorus.

[0032] Alternatively or additionally, the heteroatom is preferably boron, which may be added using, for example, boric acid or diboron trioxide.

[0033] In a preferred embodiment, the solvent is selected from the group consisting of cyclic ethers and / or azeotropic alcohol water mixtures. It has been found that even cyclic ethers that are difficult to oxidize, such as tetrahydrofuran and azeotropic alcohol water mixtures, can be used in a process with a cell voltage of less than 10V.

[0034] The present invention further relates to a graphite-containing metal oxide electrode manufactured by one of the methods according to one or more of the above-mentioned embodiments.

[0035] The graphite-containing metal oxide electrode comprises one of the electrodes first used in the method in the form of a conductive or semiconducting substrate, and a graphite-supported metal oxide and optionally a layer of foreign atoms and / or metals (or metal alloys) deposited on the substrate by the method. The graphite support provides the necessary strength and impermeability for the layers deposited on the substrate. Charge transport from the substrate to the metal oxide is optimized and the stability of the substrate is increased.

[0036] The graphite-containing metal oxide electrode preferably comprises a layer up to a few micrometers, more preferably up to 10 μm, deposited on a substrate. The thicker the layer, the longer it will last during operation and the higher current densities that can be achieved during operation.

[0037] Here, the graphite-containing metal oxide electrode may be provided in the form of a module having a plurality of layers of electrodes. Such electrodes in modular form may have a maximum size of 1 cm. 2 Preferably, the graphite-containing metal oxide electrode is 1 cm 2 Larger size, preferably 16cm 2 Larger size, preferably 0.16~2.5m 2 The sizes range from 0.01 to 0.01.

[0038] The present invention further relates to the use of a graphite-containing metal oxide electrode for producing hydrogen and / or oxygen by electrochemical water splitting (photoelectrochemical water splitting). The graphite-containing metal oxide electrode may be used as both an anode and a cathode in electrochemical water splitting, i.e., for producing oxygen and / or hydrogen in electrolytic water splitting. The above should be understood to mean that the graphite-containing metal oxide electrode is not used simultaneously as an anode and a cathode during electrochemical water splitting, but rather one graphite-containing metal oxide electrode produced by the above method is used as an anode, while a further graphite-containing metal oxide electrode produced by the above method is used as a cathode.

[0039] The graphite-containing metal oxide electrodes can be used on an industrial scale. They are particularly suitable for the production of hydrogen on an industrial scale. This hydrogen is also called green hydrogen, since it can be produced in an environmentally friendly way from a renewable energy source (electric current). However, it is advantageous to produce a plurality of graphite-containing metal oxide electrodes by the above-mentioned method, to use one of the produced graphite-containing metal oxide electrodes as an electrode for hydrogen production, and to use a further produced graphite-containing metal oxide electrode as an anode for oxygen production in an overall electrochemical water splitting.

[0040] Furthermore, the present invention relates to an electrolysis cell for producing hydrogen and oxygen by electrochemical water splitting (photoelectrochemical water splitting), comprising a graphite-containing metal oxide electrode according to one or more of the above-mentioned embodiments as a cathode and / or a graphite-containing metal oxide electrode according to one or more of the above-mentioned embodiments as an anode.

[0041] In a preferred embodiment, the electrolysis cell contains an alkaline solution as the electrolyte. The alkaline solution preferably contains 0-6 molar KOH, and for a 0 molar KOH solution, the electrolysis cell has an alkaline exchange membrane (AEM). The electrolysis cell is preferably configured to perform electrolysis at a temperature range of room temperature to 80°C. The voltage across the cell for complete water splitting is in the range of 1.23-2.5 V, and the current density is 100 kcal per square centimeter (cm -2 )100~1000mA.

[0042] The electrolysis cell is preferably constructed on an industrial scale for producing hydrogen on an industrial scale. The graphite-containing metal oxide electrode may be produced by the method according to the invention as a large area electrode with a size of 0.16 to 2.5 square meters. -2 At a current density of 1000 s, the electrolytic cell is 2.5 m 2 Using graphite-containing metal oxide electrodes, up to 8 tons of H2 (=4×10 6 mol) can be produced.

[0043] The invention is explained in more detail below with reference to the accompanying drawings and examples, in which the drawings are schematic and not to scale. [Brief description of the drawings]

[0044] [Figure 1a] FIG. 1a shows a flow diagram (part 1) of a method according to one embodiment. [Figure 1b] FIG. 1b shows a flow diagram (part 2) of a method according to one embodiment. [Figure 1c] FIG. 1c shows a flow diagram (part 3) of a method according to one embodiment. [Diagram 2] FIG. 2 shows a flow diagram of a method according to a further embodiment. [Diagram 3] FIG. 3 shows a cross-sectional view of an electrolysis cell according to the invention. [Figure 4] FIG. 4 shows the powder diffraction pattern of black mass. [Diagram 5] FIG. 5 shows a powder diffraction pattern of a further black mass. [Figure 6] FIG. 6 shows the cyclic voltammogram of a graphite-containing metal oxide electrode according to the present invention. [Figure 7] FIG. 7 shows the chronopotentiometry of the graphite-containing metal oxide electrode shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Figures 1a-1c show a flow diagram of a method according to one embodiment. Shown in each example is a cross-sectional view of an electrolysis cell in which a graphite-containing metal oxide electrode according to the invention is produced. Figure 1a shows a step in which an electrolysis cell 10 is provided, comprising an electrode 11, a further electrode 12 and an aqueous and / or non-aqueous carbonyl- and cyano-free solvent 14. Figure 1b shows a subsequent step in which a black mass 15 is introduced into the solvent 14 in the electrolysis cell 10, the black mass 15 comprising a graphite-supported noble metal-free metal oxide. Figure 1c shows a subsequent step in which a voltage is applied to the electrode 11 and the further electrode 12, so that the noble metal-free metal oxide and graphite provided by the black mass 15 are deposited on the electrode 11 to produce a graphite-containing metal oxide coating 17 on the electrode 11 to form a graphite-containing metal oxide electrode.

[0046] FIG. 2 shows a flow diagram of a method according to a further embodiment. The method comprises first carrying out a step 4 of determining the composition and morphology of the black mass, followed by a step 5 of chemically modifying the black mass according to the composition and morphology determined in step 4, in which, starting from the ratio of the proportions of metal oxides present in the black mass, the ratio is changed in order to achieve a higher level of performance and a longer stability of the graphite-containing electrode to be produced when used in electrochemical water splitting. Then, optionally, a step 6 is carried out of adding one or more foreign atoms (promoter atoms), such as nitrogen, sulfur and / or phosphorus, to the graphite support of the black mass. Step 5 or optional step 6 is followed by step 1 of providing an electrolytic cell having an electrode, a further electrode and an aqueous and / or non-aqueous carbonyl and cyano-free solvent. Step 1 is followed by step 2 of introducing the black mass into the solvent in the electrolytic cell. Step 2 is followed by step 3 of applying a voltage to the electrode and the further electrode, such that the noble-metal-free metal oxide and graphite provided by the black mass are deposited on the electrode to produce a graphite-containing metal oxide coating on the electrode to form a graphite-containing metal oxide electrode.

[0047] FIG. 3 shows a cross-sectional view of an electrolysis cell according to the invention. The electrolysis cell 20 is configured to produce hydrogen and oxygen by electrochemical water splitting (photoelectrochemical water splitting). The electrolysis cell comprises two graphite-containing metal oxide electrodes according to the invention, for example manufactured by the method shown in FIG. 1a-1c or FIG. 2. One of the graphite-containing metal oxide electrodes serves as a cathode 22 and the other graphite-containing metal oxide electrode serves as an anode 21. The cathode 22 comprises a substrate 27 provided with a coating 17 of graphite-supported metal oxide. The anode 21 comprises a further substrate 28 provided with a coating 17. Furthermore, the electrolysis cell 20 comprises an alkaline solution 24. The electrolysis cell 20 also comprises a diaphragm 25, for example in the form of an AEM, which separates the anode space from the cathode space.

[0048] During operation of the electrolysis cell 20, an electric current is applied to the cathode 22 and the anode 21, resulting in the splitting of water. Oxygen is produced at the anode 21 and hydrogen is produced at the cathode 22.

[0049] Figure 4 shows a powder diffraction pattern of black mass, which indicates the composition of the black mass described as a recycled material in Example 2 below.

[0050] Figure 5 shows a further powder diffraction pattern of the black mass, which indicates the composition of the black mass described as recycled material in Example 3 below.

[0051] FIG. 6 shows the cyclic voltammogram of a graphite-containing metal oxide electrode according to the invention at a scan rate of 5 mV / s. Measurements of the second and tenth cycles were carried out in a three-electrode configuration. A Hg / HgO reference electrode was used, the potential of which is based on the reversible hydrogen electrode (RHE). To prepare a graphite-containing metal oxide electrode according to the invention, the black mass produced in Examples 2-5 below was used and subjected to a method corresponding to that described in Example 1 using Ni foam. The graphite-containing metal oxide electrode thus prepared was used as a working electrode for oxygen generation.

[0052] Figure 7 shows the current density at 100mA / cm 2 4 shows the chronopotentiometry of this graphite-containing metal oxide electrode at 2000 K. EXAMPLES

[0053] Example 1 Fabrication of graphite-containing metal oxide electrodes To produce a graphite-containing metal oxide electrode according to the invention, an electrolytic cell is provided, for example with an electrode based on Ni, Fe and / or Cu foam and a further electrode made of steel in 10 ml of a solvent of a cyclic ether such as tetrahydrofuran. 25 mg of black mass and 2 mg of iodine are introduced into the solution. A voltage of 10 V is then applied to the electrodes at room temperature in air for 30 seconds to 10 minutes. 2 mg of iodine and 25 mg of black mass are sufficient to produce 10 to 15 graphite-containing metal oxide electrodes. The graphite-containing metal oxide electrodes thus produced are washed with an organic solvent and air-dried.

[0054] Example 2 Determination of the composition and morphology of black mass The black mass used is a recycled material from used batteries for the electrical drive of electric vehicles, in particular electric cars. The recycled material is a recycled material based on NMC batteries (lithium nickel manganese cobalt oxide batteries), which were provided by Duesenfeld GmbH (Wendeburg, Germany). The one or more graphite-supported precious metal-free metal oxides of the black mass comprise a mixture of Ni, Co and Mn with at least one of their oxides. In addition to various graphites, the recycled material also contains (Li 0.98 Ni 0.02 )(Li 0.05 Ni 0.75 Co 0.10 Mn 0.10 )O2, aluminum, and Al2O3. Figure 4 shows the powder diffraction pattern of this black mass.

[0055] Example 2-1 Chemical modification of black mass 500 mg of the black mass used in Example 2 was placed in an autoclave together with 20.05 g of Ni(OAc) and 30 ml of water, and heated at 180° C. for 16 hours. The suspension was naturally cooled in the oven, washed with water and acetone, and air-dried.

[0056] Example 2-2 Chemical modification of black mass 500 mg of the black mass used in Example 2 was placed in an autoclave together with 20.1 g of Ni(OAc) and 30 ml of water, and heated at 180° C. for 16 hours. The suspension was naturally cooled in the oven, washed with water and acetone, and air-dried.

[0057] Example 2-3 Chemical modification of black mass 100 mg of the black mass used in Example 2 was ground and heated in an aqueous solution of 2 M formic acid and 6% H2O2 at 80° C. for 2 hours. The material was then washed with water and acetone and air-dried.

[0058] Examples 2-4 Chemical modification of black mass 100 mg of the black mass used in Example 2 was ground and heated in an aqueous solution of 1MKOH at 80° C. for 2 hours. The material was then washed with water and acetone and air-dried.

[0059] Examples 2-5 Addition of nitrogen as a heteroatom 100 mg of the black mass used in Example 2 was first flushed with NH3 in a tubular furnace for 2 hours, then heated to 300°C (ramp 300°C / h). After 6 hours, it was naturally cooled to room temperature.

[0060] Examples 2-6 Addition of nitrogen as a heteroatom 100 mg of the black mass used in Example 2 was first flushed with NH3 in a tubular furnace for 2 hours and then heated to 400° C. (ramp 300° C. / h). After 6 hours, it was naturally cooled to room temperature.

[0061] Examples 2-7 Addition of nitrogen as a heteroatom 100 mg of the black mass used in Example 2 was first flushed with NH3 in a tubular furnace for 2 h and then heated to 200° C. (ramp 300° C. / h). After 6 h, it was naturally cooled to room temperature.

[0062] Examples 2-8 Addition of nitrogen as a heteroatom 100 mg of the black mass used in Example 2 was first flushed with NH3 in a tubular furnace for 2 h and then heated to 350° C. (ramp 300° C. / h). After 6 h, it was naturally cooled to room temperature.

[0063] Examples 2-9 Addition of nitrogen as a heteroatom 100 mg of the black mass used in Example 2 was first flushed with NH3 in a tubular furnace for 2 h and then heated to 250° C. (ramp 300° C. / h). After 6 h, it was naturally cooled to room temperature.

[0064] Example 2-10 Addition of nitrogen as a heteroatom 100 mg of the black mass used in example 2 was added to a solution of ethanol (40 ml) and urea (1.5 g) and suspended in an ultrasonic bath for 2 hours. The solvent was evaporated with a stream of N2 for 2 hours. The product formed was crushed, placed in a tube furnace and flushed with N2 for 1 hour. The black mass thus obtained was heated to 300°C (ramp 300°C / h) and maintained at that temperature for 2 hours before being allowed to cool naturally.

[0065] Example 2-11 Addition of nitrogen as a heteroatom 100 mg of the black mass used in Example 2 was ground and placed in a tube furnace. The system was flushed with N2 for 1 h. The black mass thus treated was then heated to 300°C (ramp 300°C / h) and maintained at that temperature for 2 h before being allowed to cool naturally.

[0066] Example 2-12 Addition of nitrogen as a heteroatom 500 mg of the black mass used in Example 2 was placed in an autoclave together with 1.5 g of urea and 30 ml of water, and heated at 180° C. for 16 hours. The suspension was naturally cooled in the oven, washed with water and acetone, and air-dried.

[0067] Example 2-13 Addition of nitrogen and sulfur as heteroatoms 500 mg of the black mass used in Example 2 was placed in an autoclave together with 1.5 g of thiourea and 30 ml of water, and heated for 16 hours at 180° C. The suspension was naturally cooled in the oven, washed with water and acetone, and air-dried.

[0068] Example 2-14 Addition of sulfur as a heteroatom 500 mg of the black mass used in Example 2 was placed in an autoclave together with 50 mg of elemental sulfur (S8) and 30 ml of water and heated at 180° C. for 16 hours. The suspension was allowed to cool naturally in the oven, washed with water and acetone, and air-dried.

[0069] Example 2-15 Addition of phosphorus as a foreign atom 500 mg of the black mass used in Example 2 was placed in an autoclave together with 50 mg of red phosphorus and 30 ml of water, and heated at 180° C. for 16 hours. The suspension was naturally cooled in the oven, washed with water and acetone, and air-dried.

[0070] Example 2-16 Addition of sulfur as a heteroatom 100 mg of the black mass used in Example 2 was pulverized and heated to 300° C. in a tubular furnace in an H 2 S atmosphere (ramp 300° C. / h), and the temperature was maintained for 3 hours and then naturally cooled.

[0071] Example 2-17 Addition of boron as a foreign atom 500 mg of the black mass used in Example 2 was placed in an autoclave together with 700 mg of boric acid or diboron trioxide and 30 ml of water, and heated at 180° C. for 16 hours. The suspension was naturally cooled in the oven, washed with water and acetone, and air-dried.

[0072] Example 2-18 Addition of nitrogen as a heteroatom 500 mg of the black mass used in Example 2 was placed in an autoclave together with 3 ml of hydrazine and 27 ml of water, and heated at 180° C. for 16 hours. The suspension was naturally cooled in the oven, washed with water and acetone, and air-dried.

[0073] Example 3 The black mass used is a recycled material from used batteries for electrically driving electric vehicles, in particular electric cars. The recycled material is a recycled material based on LFP batteries (lithium iron phosphate batteries), which was provided by Duesenfeld GmbH (Wendeburg, Germany). The one or more graphite-supported noble metal-free metal oxides of the black mass include iron oxide. The powder diffraction diagram of this black mass is shown in Figure 5.

[0074] Example 3-1 Addition of nitrogen as a heteroatom 100 mg of the black mass used in Example 3 was first flushed with NH3 in a tubular furnace for 2 h and then heated to 300° C. (ramp 300° C. / h). After 6 h, it was naturally cooled to room temperature.

[0075] Example 3-2 Chemical modification of black mass 100 mg of the black mass used in Example 3 was ground and heated in an aqueous solution of 2 M formic acid and 6% H2O2 at 80° C. for 2 hours. The material was then washed with water and acetone and air-dried.

[0076] Example 3-3 Chemical modification of black mass 100 mg of the black mass used in Example 3 was ground and heated in an aqueous solution of 1MKOH at 80° C. for 2 hours. The material was then washed with water and acetone and air-dried. [Explanation of symbols]

[0077] 1 offer 2 Introduction 3 application 4 decision 5 Qualification 6 addition 10 Electrolysis Cell 11 electrodes 12 electrodes 14 Solvents 15. Black Mass 16 Voltage Source 17 Coating 20 Further electrolytic cells 21 Anode 22 Cathode 24 Alkaline Solution 25 Diaphragm 26 Further voltage sources 27 Substrate 28 More Substrates

Claims

1. 1. A method for producing a graphite-containing metal oxide electrode, comprising: a) providing (1) an electrolytic cell (10) having an electrode (11), a further electrode (12) and an aqueous and / or non-aqueous carbonyl- and cyano-free solvent (14); b) introducing (2) into the solvent (14) in the electrolytic cell (10) a black mass (15) having a graphite-supported noble metal-free metal oxide and a proton source; c) applying a voltage (3) to said electrode (11) and to said further electrode (12), so that the noble metal-free metal oxide and graphite provided by the black mass (15) are deposited on said electrode (11) to produce a graphite-containing metal oxide coating (17) on said electrode (11) to form said graphite-containing metal oxide electrode; The method includes:

2. 2. The method according to claim 1, characterized in that the black mass (15) is a recycled material, preferably the recycled material is recycled material from used batteries for electrically driving electric vehicles, preferably electric cars.

3. 3. The method of claim 1 or 2, wherein the one or more graphite supported noble metal free metal oxides comprise a mixture of Ni, Co and / or Mn with at least one of their oxides, or comprise iron oxide(s), or comprise a mixture of Ni, Co, Al oxides.

4. Prior to step a) or step b), (4) determining the composition and morphology of said black mass (15); - a step (5) of chemically modifying said black mass (15) according to the determined composition and morphology, including changing the percentage of metals (oxides) present in said black mass; 4. The method according to claim 1, wherein the step of:

5. Prior to step a) or step b), - adding (6) one or more heteroatoms (promoter atoms) to the graphite support of said black mass (15), said heteroatoms being preferably nitrogen, sulfur, phosphorus and / or boron, more preferably nitrogen and / or sulfur; 5. The method according to claim 1, wherein the step of:

6. The method according to any one of claims 1 to 5, characterized in that the solvent (14) is selected from the group consisting of cyclic ethers and / or azeotropic alcohol water mixtures.

7. A graphite-containing metal oxide electrode produced by the method according to any one of claims 1 to 6.

8. Use of a graphite-containing metal oxide electrode for producing hydrogen and / or oxygen by electrochemical water splitting (photoelectrochemical water splitting).

9. 10. An electrolysis cell (20) for producing hydrogen and oxygen by electrochemical water splitting (photoelectrochemical water splitting), comprising a graphite-containing metal oxide electrode according to claim 7 as a cathode (22) and / or a graphite-containing metal oxide electrode according to claim 7 as an anode (21).

10. 10. The electrolytic cell (20) of claim 9, characterized in that the electrolyte is an alkaline solution.

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