EP4377497A2

EP4377497A2 - Method for the selective catalytic hydrogenation of organic compounds, and electrode and electrochemical cell for said method

Info

Publication number: EP4377497A2
Application number: EP22761071.4A
Authority: EP
Inventors: Daniel SIEGMUND; Ulf-Peter APFEL; Kai JUNGE PURING; Kevinjeorjios PELLUMBI; Julian Tobias KLEINHAUS
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV; Ruhr Universitaet Bochum
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV; Ruhr Universitaet Bochum
Priority date: 2021-07-29
Filing date: 2022-07-28
Publication date: 2024-06-05
Also published as: CA3227590A1; WO2023006930A3; WO2023006930A2; JP2024529620A; KR20240033080A; DE102021119761A1

Abstract

The application relates to a method for the electrocatalytic hydrogenation of organic compounds in an electrochemical cell, in which the reducible organic compound is present in liquid form or at least partially in dissolved form, wherein the reducible organic compound is hydrogenated at the cathode. The cathode comprises, as a catalyst, a transition metal chalcogenide selected from sulfides, selenides and tellurides. The application also relates to an electrode, comprising a carrier material and a layer of the catalyst provided on the carrier material; to an electrochemical cell having an electrode of this type; and to the use of the transition metal chalcogenide catalyst for the electrochemical hydrogenation of organic compounds.

Description

Patent application:

Process for the selective catalytic hydrogenation of organic compounds and electrode and electrochemical cell for this process

The application relates to a method for the electrocatalytic hydrogenation of organic chemical compounds using an electrode which has a transition metal chalcogenide, essentially a sulfide, selenide and/or telluride, as the catalytically active layer. The application also relates to an electrode for electrocatalytic hydrogenation and an electrochemical cell for carrying out said reaction. The composition of the catalysts used can be varied and adjusted over a wide range, so that the catalysts can be used to adjust an increased selectivity with regard to multiply reducible compounds and various hydrogenatable functional groups. The electrocatalytic hydrogenation according to the application can in principle be used for any chemical synthesis, for example in the hydrogenation of unsaturated organic compounds. In particular, the synthesis of fine chemicals, the hydrogenation of vegetable oils in fat hardening in the food industry, the upgrading of biomass, the hydrogenolytic elimination of corresponding protective groups and the storage of hydrogen in the form of liquid organic hydrogen carriers (LOHCs) should be mentioned.

According to the prior art, the hydrogenation of organic compounds can be carried out using the following processes: hydrogenation of organic compounds using stoichiometric hydride transfer agents, hydrogenation in thermal heterogeneously or homogeneously catalyzed processes and electrocatalytic hydrogenation reactions.

This type of hydrogenation by means of stoichiometric hydride transfer agents is used in particular in the reduction of multiple CO bonds in small-scale batch processes or on a laboratory scale and requires the resulting products to be separated off stoichiometric waste products. These waste products may be of environmental concern (e.g. cyanoboron compounds).

The thermal-catalytic hydrogenations with elemental hydrogen in the presence of a suitable catalyst are associated with the inherent disadvantage of the need for upstream hydrogen generation. In addition, many hydrogenation reactions must be run at elevated temperatures and pressures to ensure adequate conversion. This not only represents an additional input of energy, but also places increased demands on process reliability. The only suitable catalysts for homogeneously catalyzed reactions are often expensive transition metal complexes based on Pt, Pd, Ru, Ir or Rh. Nevertheless, for the selective hydrogenation of more complex systems, e.g. in asymmetric hydrogenation, mostly thermal-catalytic hydrogenations with noble metal catalysts have to be used. Noble metals are also frequently used in heterogeneously catalyzed reactions. Noble metal-free catalysts are based on finely divided, small-particulate transition metals such as Ni. In contrast to the noble metals, however, increased process pressures and possibly increased temperatures are required in order to achieve a sufficient degree of hydrogenation. A disadvantage of these systems is their severely limited selectivity in the hydrogenation of polyunsaturated compounds. In addition, the heterogeneous catalysts are often susceptible to catalyst poisons. This results in a limitation of the potentially hydrogenatable substrates.

A relatively new type of hydrogenation is electrocatalysis. The electrocatalytic hydrogenation of unsaturated organic substrates through the use of electrodes based on Raney Ni on stainless steel is known (US2014110268 A). Electrocatalytic conversion with metal particles on porous carbon substrates has also been described (US2015008139 A). Another disadvantage is the use of (noble metal) catalysts, which have a low tolerance of catalyst poisons, are expensive and whose production is fraught with environmental concerns. US20190276941 A1 discloses the selective hydrogenation of alkynes to alkenes on copper electrodes. In this case, it is not possible to adapt the catalyst to difficult substrates such as electron-deficient alkynes. In addition to the focus on noble metal-based catalysts and Raney-Ni, the major disadvantage of electrocatalytic processes is the limitations in flexibility (especially in the presence of several functional groups or the cleavage of multiple bonds) at the achievable degrees of cleavage and, in turn, the susceptibility to catalyst poisons.

A noble metal-free electrocatalytic system is also known from electrocatalytic water splitting. WO 2020/169806 describes the use of pentlandites as electrocatalysts for the electrolytic production of H ₂ .

The present invention is based on the object of specifying a process for the electrocatalytic lydration of organic compounds with which the disadvantages of the prior art can be overcome. In particular, the electrocatalyst used should have a high selectivity and adaptability to complex organic substrates, work as energy-efficiently as possible, deliver the highest possible yields and/or also be free of noble metals if possible; In addition, it is sought that the greatest possible current densities can be realized with the electrodes that can be produced therefrom.

At least one of these objects is solved by the method, the electrode and the electrochemical cell according to the independent claims. The dependent claims and the description as well as the examples teach advantageous developments.

The method according to the application for the electrocatalytic lysing of organic compounds is characterized in that the electrode used comprises or consists of a transition metal chalcogenide as an electrocatalyst, the transition metal chalcogenide being a sulfide, a selenide or a telluride (or mixtures of two or three of the mentioned chalcogenides such as sulfoselenides) is. The electrode (particularly the cathode) used for the catalytic hydrogenation comprises or consists of this transition metal chalcogenide as a catalyst. The lydration takes place in such a way that an organic compound to be reduced (in particular to be hydrogenated) in an electrochemical cell (which, in addition to a cathode and an anode, contains a liquid and/or solid electrolyte has) is reduced at the cathode. The hydrogenation can take place either continuously (in particular in a flow cell) or discontinuously (in a batch cell).

According to the application, a reducible organic compound is understood to mean, in particular, organic compounds which have at least one aromatic or heteroaromatic structural unit, but in particular at least one multiple bond. Mention should be made here in particular of CC multiple bonds, aromatics, heterocycles, CO multiple bonds, CN multiple bonds, NO ₂ groups and NN multiple bonds or combinations of compounds with two or more of the groups/bonds mentioned. Both double bonds and triple bonds can be considered here; both low molecular weight substances and polymers are suitable. The organic compound to be reduced can be liquid, it can be present at least partially in dissolved form in a solvent and in both cases it can also be partially present as a solid (if it is ensured that at least part has gone into solution or is liquid). The reduction of gaseous compounds is also conceivable, in particular if these are at least partially in dissolved form. The state of aggregation at room temperature serves as a benchmark here. According to the application, the electrocatalytic reduction itself usually takes place at temperatures between -78 and 100.degree. Since—in contrast to hydrogenation reactions in which H ₂ is mandatory—the hydrogenation reactions according to the invention are usually endothermic and atomic hydrogen present on the catalyst surface serves as the hydrogenating agent according to current understanding, there is in principle no restriction with regard to the upper limit of the temperature. The specified upper limit of the temperature at 100 °C therefore has economic reasons. Usually the temperature will be between 0°C and 100°C and often between 20°C and 80°C. Furthermore, independently of this, the reactions are usually carried out under atmospheric pressure. The reduced organic compound is also usually present in the aforementioned aggregate states, i.e. in particular as a dissolved substance or as a liquid (in principle, however, the reduced compound can also precipitate out of the solvent as a solid, which in special cases can be determined by the choice of solvent or solvent mixture in addition to the choice of catalyst can serve the reduction towards a specific product). Irrespective of the aforementioned parameters, current densities can be achieved in the method according to the invention which are in particular at least 10 mA cm ^-2 and in particular greater than 100 mA cm ^-2 . Current densities of up to 1 A cm ^-2 can also be achieved, particularly with coated electrodes; current densities of up to 2 A cm ^-2 are also possible when using appropriate electrodes. However, Elohe current densities are very relevant from an economic point of view (and thus in particular for industrial processes).

According to the invention, it has now been found that transition metal sulfides, selenides and tellurides used as catalysts have the property of selectively reducing or hydrogenating organic compounds. The catalytic activity is based in particular on the presence of the chalcogenide and only secondarily on the metal (cation). In particular, it was found that there is a wide range of variation with regard to the catalysts and their selectivity and, depending on the transition metal chalcogenide used, it can be influenced which functional group of a molecule with several reducible groups is reduced in the catalytic cleavage and which configurational isomer is obtained in the cleavage of a triple bond . It goes without saying that the chalcogenides according to the invention are understood as meaning salt-like compounds in which the chalcogen is present as an anion and the transition metal is present as cation. One route for preparing these chalcogenides is typically either from mixtures of powders of the elements, or from powders of the elements and metal chalcogenides (the latter, for example, to adjust a certain stoichiometry); typically, in this and alternative processes, chalcogenides with a substantially continuous chalcogenide structure are also present; In other words, the chalcogenides are essentially present as the stoichiometric chalcogenide, where essentially means that within the scope given two paragraphs below, some non-stoichiometry can also be present. In exceptional cases, however, a production method can also be used in which only the surface of the catalyst particles involved in the catalytic process carries a sulfide, selenide and/or telluride layer, which was obtained, for example, by reacting the elementary metal particles with the chalcogen. Using the chalcogenides according to the application, a process optimization for the formation of a desired product can therefore take place. Furthermore found that high Faraday efficiencies can be achieved with the catalysts mentioned. In contrast to the well-known flydration processes, it is not necessary to use a stoichiometric reducing agent and waste products are avoided. The supply of gaseous hydrogen can also be dispensed with; an active reduction takes place directly on the catalyst surface without the intermediate step of the formation of H ₂ . The protons required for this can in particular be made available by a protic solvent or can be supplied to the cathodic half cell via the anodic half cell and the oxidation process taking place there with the formation of protons via a membrane arranged between the half cells and/or a solid electrolyte. Compared to the thermal and electrocatalytic flydrations according to the prior art, in particular with the noble metal catalysts palladium, platinum or ruthenium (which have so far been among the most active catalysts for flydration reactions), the catalysts according to the application are significantly cheaper and more sustainable and also have (in electrocatalytic reactions) a high activity. The systems according to the invention can also be used to hydrogenate organic compounds of low purity or to carry out flydrations of organic compounds which contain sulfur. This is also due to the fact that the known catalyst poisons for noble metal catalysts or for other typical flydriation catalysts (such as Fi ₂ S) do not pose a problem with the catalysts used according to the invention.

According to one embodiment of the invention, the transition metal chalcogenide for the electrocatalytic flydration is selected from compounds which essentially have the empirical formula MX, MX ₂ , M ₂ X ₃ , M ₂ X ₄ , M ₃ X ₄ , M ₉ X ₈ or M" ₆ M _k correspond to X _| X' _m .

In this case, M is selected from a transition metal of the 4th, 5th or 6th period, the metals of the 4th period being preferred, in particular the metals of the 4th period of groups 4 to 10, with a lower priority—for the reasons explained above these are also the metals of the 5th or 6th period that are not noble metals. For reasons of cost alone, metals from the 4th period should be preferred in case of doubt. M can also be a mixture of several of the metals mentioned. Often the metal M will be Fe, Co and/or Ni or will comprise at least one or more of these metals.

The metal M" is a main group metal, in particular an alkali metal or alkaline earth metal; M" can also stand for a mixture of two or more main group metals.

X stands for S, Se or Te and for mixtures of the chalcogenides mentioned and X ^′ for a halide, where in the case of the compound class M″ ₆ M _k X _m X′ _n k, m and n stand for decimal numbers, where 24≦k≦ 25 and 26 ≤ m ≤ 28 and 0 ≤ n ≤ 1.

Of the chalcogenides mentioned, the sulfides and the sulfoselenides are often preferred for reasons of toxicity alone. Without restricting the generality of what has been said above and below, from the current point of view of the applicant, the use of transition metal chalcogenides in particular seems to be particularly advantageous, in which either the transition metal in the crystal structure can assume two different oxidation states and/or the chalcogenide X does not exclusively have a charge as X ^2" can be attributed, as is the case, for example, in the presence of X ₂ ^2" . This applies in particular to pentlandites, chalcogenides with a spinel structure or a spinel-like structure and, to a lesser extent, also for chalcogenides whose structure has X ₂ ^2_ ions, for example chalcogenides with a pyrite structure or a pyrite-like structure. Such structures seem to favor the coordination of atomic hydrogen at the catalyst surface. In contrast, compounds of the molecular formula MX or MX ₂ will only be selected as a secondary option, since these generally have somewhat low stability under electrochemical conditions.

In principle, this means that chalcogenides of the formula M ₂ X ₄ , M ₉ X ₈ or M" ₆ M _k X _| X' _m are particularly suitable, especially when M is a metal of the 4th period of groups 4 to 10, and here in turn is in particular Fe, Co and/or Ni or comprises at least one or more of these metals.

According to the application, “essentially the empirical formula” is understood to mean that the transition metal chalcogenides can also be not only pure compounds but also non-stoichiometric compounds or that doping can be present. In the case of the non-stoichiometric compounds, the molar ratio X/M can be changed (up or down) by up to 2%, occasionally up to 5% or in extreme cases even up to 10% compared to the integer ratio. Doping with a non-metal, for example with one or more of the elements B, O, N, P, As, F, CI,

Br, I, are present in a content of up to 5 atomic % based on the metal M. One Doping can, for example, by the possible for all stoichiometries thermal production of the compounds MX, MX ₂ , M ₂ X ₃ , M ₂ X ₄ , M ₃ X ₄ , M ₉ X ₈ or M " ₆ M _k X _| X ' _m from the Elements M (where - as explained - M can also stand for different transition metals) and X with admixture of the corresponding non-metal with which doping is carried out. Oxygen doping can take place, for example, by the transition metal chalcogenide, for example pentlandite, being partially oxidized. In this case, a partial surface modification takes place, so that a surface is then present on a backbone of the transition metal chalcogenide X, which also has oxygen in addition to the chalcogen X. Furthermore, doping - for example with nitrogen or a halogen - can take place by the production from the elements a chemical compound of the non-metal to be doped is additionally added, for example a transition metal nitride or a transition smetal halide.

Transition metal chalcogenides have proven to be particularly suitable which essentially correspond to the formula M ₉ X ₈ and are at least partially crystallized in the pentlandite structure (according to the application, the relevant measurement is carried out by means of powder diffractometry (PXRD)). Here again, the compounds of the formula Fe _9-abc Ni _a Co _b M' _c S _8-d Se _d are to be emphasized in particular. Here, M ^' is selected from the same transition metals with the same preferred variants as specified above for M, and is selected in particular from one or more metals from the group consisting of Ag, Cu, Zn, Cr and Nb. a, b, c and d are decimal numbers, but often integers or half-integers (where a stoichiometric compound and a non-stoichiometric compound as defined above can also be present), where a is a number from 0 to 7, in particular from 1 to 6, b is one is a number from 0 to 9, in particular from 0 to 8, c is a number from 0 to 2, in particular from 0 to 1 and d is a number from 0 to 6, in particular from 0 to 4. The sum is usually a+b +c is a number from 0 to 9, in particular from 3 to 7. It is often the case here that a is a number from 1 to 6, b is a number from 0 to 8, c is a number from 0 to 1, d is a number from 0 to 4 and the sum a+b+c is a number from 3 to 7.

The proportion of the transition metal chalcogenide M ₉ X ₈ that is present in the pentlandite structure is usually at least 80%, usually even at least 90%. Contents of this type can be achieved without any problems using the usual synthesis methods, in particular using the thermal production from the elements already mentioned. According to a further embodiment, only two of the three metals or essentially only two of the three metals iron, cobalt and nickel are contained in the compound Fe9_ _abc Ni _a Co _b M' _c S8- _d Se _d and no metal M ¹ or essentially no metal ^M1 . Essentially means in each case that the proportion of the metal not present or of the metal M ¹ , based on the metal, is less than 5 mol %.

According to a further embodiment, the electrocatalytic reduction can be carried out both in liquid and solid electrolyte cells, and in particular also in polymer electrolyte cells. In the case of liquid electrolyte cells, the organic compound to be hydrogenated is usually present in an aqueous or organic solution.

In addition, polymer electrolyte cells also make it possible to fly the organic compound in pure form or as a solution. In addition, the solvent can also contain a fat salt - for example, if water or an alcohol is used as the solvent; in the case of polymer electrolyte cells, fat salts are often not used. In each of the cells mentioned, the flydriding can take place both in a discontinuous batch operation and in a continuous flow operation. By selecting the cell and the electrolyte, the Faraday yields can be further optimized for the desired flydriding. Additional influence can also be exerted on the selectivity in the direction of different flydration products.

The method according to the invention can also be further developed in an advantageous manner if an electrode is used which is configured as described in more detail below and which in particular has one or more of the advantageous configurations of the electrode described below.

An electrode for the electrocatalytic flydriding of organic compounds in an electrochemical cell comprises, in addition to any electrical contacting of the electrode that is present and belonging to the electrode, a carrier material and a catalyst layer arranged at least on part of the surface of the carrier material. It goes without saying that the contacting (which can take place, for example, via a metal and is often glued on or pressed on) is therefore not part of the carrier material according to the application. The catalyst layer contains or consists of a transition metal chalcogenide as a catalyst, the transition metal chalcogenide being selected from sulfides, selenides and/or tellurides.

The fact that the catalyst layer is arranged “on” the carrier material can mean here and below that the catalyst layer is arranged or applied directly in direct mechanical and/or electrical contact on the carrier material. Furthermore, an indirect contact can also be referred to, in which further layers or areas are arranged between the catalyst layer and the support material.

An electrode according to the application for the electrocatalytic process has in particular one or more of the following features:

• In addition to the transition metal chalcogenide, the catalyst layer comprises a polymeric binder, in particular a polymeric non-ion-conducting binder, or consists of the two components.

• In addition to the transition metal chalcogenide and a binder that may be present, the catalyst layer also includes an additive or consists of the two (or three components if a binder is present).

• The electrode has at least partially porous areas.

• The electrode has a catalytically active surface of at least 0.2 cm ² .

Particularly good results are - as explained in more detail above in the process to which reference is made in full with regard to the suitable catalysts - usually achieved when the catalyst used are transition metal chalcogenides which essentially correspond to the formula M ₉ X ₈ and at least partially in the Crystallized pentlandite structure.

According to an advantageous embodiment, the catalyst layer comprises a polymeric binder, in particular a polymeric binder that does not belong to the ionic polymers. This binder leads to improved relaxation of the individual Catalyst particles together usually leads to improved mechanical stability and/or easier processing of the catalyst material. Depending on the carrier material, better adhesion to the carrier material can also be achieved. A binder can be used advantageously if the catalyst layer can be applied to the carrier material in the form of inks, in particular sprayed on, or if the catalyst material is used in the form of a hot-pressable mass.

Hydrophobic binders are particularly suitable as binders. In particular, these can be selected from polyolefins, fluorinated polyolefins, copolymers with polyolefins and/or fluorinated polyolefins and polymer blends which contain polyolefins and/or fluorinated polyolefins, all of which are preferably non-ion-conducting polymers. If appropriate, chlorinated polymers or copolymers (e.g. PVC or PVC-containing copolymers) can also be used or used in addition. Here, the polyolefins and fluorinated polyolefins are selected in particular from the group consisting of PE, PP, PVDF, FEP and PTFE. The proportion of binder in the catalyst layer is usually 1 to 90% by weight, in particular 5 to 80% by weight, for example 10 to 25% by weight. At levels above 25% by weight, the efficiency of the reaction in terms of the yields achieved often decreases. Adequate adhesion of the catalyst particles to one another and to any support material present can usually be achieved from 1% by weight and in particular from 5% by weight.

According to a further embodiment, the catalyst layer comprises an additive in addition to the transition metal chalcogenide and a binder that may be present. The additive can be selected in particular from substances to increase the electrical conductivity (e.g. carbon black, graphite or carbon nanotubes), substances to increase the ionic conductivity (e.g. ionomers such as Nafion, Sustainion, Piperion, Aemion, Durion, Orion), substances to increase the thermal conductivity, substances to increase corrosion resistance, substances to modify hydrophobicity and substances to improve adsorption of the organic compound to be hydrogenated (e.g. carbon black and activated carbon). Several of the additives mentioned can also be present. In addition or at the same time, additives to improve the mechanical Properties and / or additives to improve the adsorption properties are included. Alternatively or additionally, there can also be (at least) one intermediate layer between the catalyst layer and the support material. For example, layers to improve the adhesion of the catalyst layer to the support material or layers to improve the electrical conductivity are conceivable. An electrically conductive additive in the catalyst layer can also lead to a better distribution of the active centers. Finally, a further layer can also be applied to the side of the catalyst layer facing away from the support material, for example to improve the corrosion resistance or to change the hydrophilic or lipophilic properties of the surface.

The catalyst layer can be arranged on the support material in various ways. For example, the catalyst layer can be sprayed on (in particular by means of an ink); however, it can also be applied by dipping, squeegeeing, printing processes, decal processes or thermal pressing, so that functional electrode assemblies are created. The electrical contact can be made both on the front and on the back, i. H. the contact can be made either on the support material or on the catalyst layer itself.

The catalyst particles used for the catalyst layer can in principle have any particle size. However, particles with a d90 value of less than 10 μm, determined by means of a sieving method, have often proven to be advantageous because larger particles are often more difficult to process, particularly when they are used in inks to be sprayed.

According to a further embodiment, a porous material can be used as the carrier material. By using a porous material it can be achieved that the active surface of the catalyst layer (which is not a real layer but a coating in the inner surface, ie pores, cavities, interstices and the like) can be increased significantly. Such an enlarged surface can be obtained in particular if the porous support material is infiltrated with the catalyst ink, for example by dipping methods or by spraying on. According to the application, a porous carrier material is not just a carrier material with pores (in particular with a significant proportion of macropores) understood, wherein the porous carrier material can also have an open-pored structure, but also a carrier material in the form of a felt, in the form of a fabric or in the form of a mesh, for example a nickel mesh. Grid-like structures are also conceivable.

Regardless of whether the carrier material is porous, this will usually be a flat structure, and in particular a carrier material can be used which is a metal, a metal oxide, a polymer, a ceramic, a carbon-based material, a composite material or a mixture such substances. As a rule, the support material itself is not catalytically active. However, the carrier material will often have electrical conductivity. The flat carrier material can be present, for example, as a woven fabric, expanded metal, felt or foil. It can also be a membrane (particularly in the case of electrodes of a polymer electrolyte cell) or a filter film (which consists, for example, of a polymer or metal), e.g. a PTFE membrane or an Ag filter.

According to a further embodiment, the catalyst layer has an area of at least 0.2 cm ² , in particular at least 1 cm ² , preferably 1 cm ² to 4 m ² . This can be a continuous surface; however, the layer or the coating can also be interrupted or divided into several separate areas of the carrier material. The values given are for the outer surface and only the surface that does not face the carrier material (essentially this is the side facing away from the carrier material); the inner surface of a porous carrier material is not included in the calculation, ie the mathematical calculation is only based on the outer dimensions, in the simplest case of height, length and width. According to the application, electrodes of any size can therefore be produced, with surfaces in the square meter range also being able to be realized for large-scale technical application; for smaller quantities, areas of 1 cm ² or less can also be useful.

According to a further embodiment, the catalyst layer of the electrode is formed in such a way that the catalyst loading is 0.1-500 mg cm ^-2 , in particular 1-250 mg cm ^-2 , for example 2-10 mg cm ^-2 . The catalyst loading can be measured are measured by weight before and after application of the catalyst layer to the support material. From areas of 0.5 to 1 mg cm ^-2 , the active centers can usually be distributed, with which a significant conversion can be achieved. With a catalyst loading of more than 250 mg cm ^-2 only a small additional effect is achieved.

The layer thickness is also important for the number of active centers, although thicker layers can also deliver good results if a conductivity additive is added. In principle, however, it is possible to provide very thin layers (in the range of a few nanometers, for example a value of up to 10 nm), but thicker layers of up to 500 μm are also possible, with upper limits being very difficult to specify because they are very dependent strongly from the catalyst material. For economic reasons, layer thicknesses of 5 to 50 μm are often used (the layer thickness can be measured by means of scanning electron microscopy).

The object according to the invention is also achieved by an electrochemical cell for electrochemical hydrogenation, which contains the electrode described in more detail above as the electrode, in particular as the cathode. The electrochemical cell for electrocatalytic hydrogenation has in particular a reactor in which a cathode, an anode and an electrolyte are contained, with a reducible organic compound being present in liquid or at least partially dissolved form in the reactor and the reducible organic compound being present on the Cathode can be hydrogenated. In this case, the electrode has a catalyst layer and a carrier layer, as described in more detail above.

In particular, the electrochemical cell according to the application is not designed to generate a gas. The apparatus is therefore designed in such a way that it is ensured that a gas is produced as a by-product, but the hydrogenated organic compound can be produced as the main product. In particular, this means that the hydrogen frequently formed in the electrocatalytic hydrogenation is at most 50% (based on the total current yield), provided that reasonably reasonable reaction conditions are implemented. In most cases, the proportion of the resulting hydrogen is even less than 20%. Ideally, the formation of hydrogen largely avoided, so that only values in the single-digit percentage range occur.

Finally, the object according to the invention is also achieved through the use of a transition metal chalcogenide, in particular a transition metal chalcogenide selected from compounds which essentially have the molecular formula MX, MX ₂ , M ₂ X ₃ , M ₂ X ₄ , M ₃ X _4I M ₉ X ₈ or M" ₆ M _k X _| X' _m correspond, for example, to a pentlandite as a catalyst for the electrocatalytic hydrogenation of organic compounds.The use of the compounds specified in more detail further above is particularly advantageous here, with what was said above also applying equally here.

Without restricting the generality, the invention is described in more detail below with reference to figures and exemplary embodiments.

I. Electrocatalysts in batch operation

The method according to the invention was initially carried out using an electrochemical cell in batch operation. Figure 1 shows a schematic view of an electrochemical batch cell 1 with two half-cells 2, 3. In addition to the catholyte chamber 37, the cathode half-cell 3 contains the cathode with the actual electrode 32, the end plate 31 and the electrode holder 33 as well as the reference electrode 36 In addition to the anolyte chamber 24, the anode half-cell 2 contains the anode with the actual electrode 22 and the end plate 21. An ion exchange membrane 4 is provided between the two chambers 2, 3. A plurality of seals 23, 25, 5, 34, 35 are arranged in between.

Example 1 - Electrocatalytic Hydrogenation of MBY with Pentlandite Catalysts

The cell according to FIG. 1 is used for the electrocatalytic hydrogenation of 2-methyl-3-butyn-2-ol (MBY) to 2-methyl-3-buten-2-ol (MBE) or 2-methyl-butan-2 -ol (MBA) used at room temperature. Here and below, the reaction is stopped approximately at the alkene stage, but under appropriate reaction conditions it can also be carried out until essentially only the alkane is still present. All metal chalcogenide non-porous cathodes were used as the cathode Pentlandite-based catalysts used. Ni wire was used as the anode. A Nafion cation exchange membrane was used as the membrane. A 1 M solution of MBY in a solvent/conductive salt combination of 0.3 M KOH in methanol was used. The cathode had an area of 0.071 cm ² and was contacted via a brass rod in a PTFE housing. The electrocatalytic reduction was carried out for 2 hours.

Table 1 shows for various catalysts based on pentlandite (the pentlandite catalysts were obtained by means of thermal synthesis from the respective elements according to B. Konkena et al., Nat. Commun. 7: 12269 doi: 10.1038/ncomms12269 (2016), always more than 90% by weight - measured with PXRD - in the pentlandite structure templates) which Faraday efficiencies were achieved based on the desired reduction to MBE in the reaction according to Example 1 and which potentials (compared to a reversible hydrogen electrode E _RH E as reference electrode ) at a current density of -100 mA cm ^-2 were required for the lydration. It turns out that Faraday efficiencies of up to 100% can be achieved and that lower potentials than when using platinum electrodes were required throughout. According to the application, the potentials were always determined using a Gamry 101 OB potentiostat. According to the invention, yields were always determined by NMR spectroscopy using potassium hydrogen phthalate as an internal standard. Table 1 Fig. 2 shows for example 1 with Fe ₃ Ni ₆ S ₈ as a catalyst, the required potentials (E / V) for a current density of -100 mA cm ^-2 and the achieved Farraday efficiencies (FE) in comparison to experiments in which a platinum electrode or a glassy carbon electrode. It can be seen that only with Fe ₃ Ni ₆ S ₈ as a catalyst is a significant efficiency observed and at the same time a lower or significantly lower potential is required than with the comparatively examined electrodes.

Example 2 - Electrocatalytic fluxing of butynediol with pentlandite catalysts

In an electrochemical cell according to example 1, the selectivity of the flydration of 2-butyne-1,4-diol was examined with two pentlandites already used in example 1 and different conducting salt/solvent combinations (MeOFI=methanol):

Table 2 shows that in this reaction with Fe ₃ Ni ₆ S ₈ essentially the cis product is formed, while Fe ₃ Co ₃ Ni ₃ S ₈ leads to an increased formation of the trans product. The use of water as the solvent and KOFI as the conductive salt shows the best selectivity and the most favorable potential values.

Tab.2:

Example 3 - Electrocatalytic Flvdriuna of MBY by means of catalysis The M" ₆ M _k X _m X' _n _catalysts were produced by means of hotch temperature synthesis in evacuated ampoules. Stoichiometric amounts of the respective elements were treated in a quartz glass ampule for 96 h in an oven at a temperature that is typically between 650 and 800. The The temperature chosen depends on the stoichiometry used: Ba ₆ Ni ₂₅ : 675 °C, Ba ₆ Fe _12.5 Co ₂₅ : 675 °C,

Ba ₆ Fe _8.33 Co _8.33 Ni _8.33 : 700°C. Ba ₆ Fe ₁₂₅ Co ₂₅ then tempered for a further 96 h at 775°C and Ba ₆ Fe _{8 .33} Co _{8 .33} Ni ₈ .33 for a further 96 h at 800°C. The successful synthesis of the catalysts can be confirmed by PXRD analysis.

In an electrochemical cell according to example 1, the selectivity of the hydrogenation of 2-butyne-1,4-diol was examined. In contrast to Examples 1 and 2, non-porous catalysts based entirely on metal chalcogenide were used as the cathode. The reaction was carried out using a _1M _MBY solution in _0.3M _KOH /H ₂ 0 or 0.3M KOH/MeOH as a fine salt/solvent, with butenediol being obtained Table 3 shows that all the materials are suitable for an electrocatalytic hydrogenation.

Table 3

Example 4 - Electrocatalytic Hydrogenation of MBY with MX and MX ₂ Catalysts

The reaction according to Example 1 was carried out using transition metal sulfides of the empirical formulas MS and MS ₂ as a catalyst with a 1M MBY solution in 0.3M KOH/H ₂ O as

carried out fat salt / solvent, whereby MBE is obtained. For comparison, the last line gives an example of a catalyst with a pentlandite structure (Fe ₃ Ni ₆ S ₈ from example 1). Tab. 4 shows the required potentials (E/V) for a current density of -100 mA cm ^-2 and the achieved Faraday efficiencies (FE).

Table 4: Example 5 - Electrocatalytic hydrogenation of nitro compounds, aldehydes and terminal alkynes with pentlandite catalysts

Functional groups other than disubstituted alkynes can also be reduced with the hydrogenation according to the invention. The reaction was carried out under the same conditions as in Example 1. In addition, Table 5 specifies the conductive salts, solvents, concentrations and (also used in Example 1) pentlandite catalysts used.

Table 5:

Example 6 Electrocatalytic Hydrogenation of MBY with Pentlandite Catalysts in a Solid Electrolyte Cell Using Different Electrode Concepts The reaction according to Example 1 was also carried out with other electrode concepts instead of with electrodes consisting entirely of metal chalcogenide, namely electrodes with a pentlandite coating, with a pressed catalyst mass or with a catalyst mass pressed onto a metal grid. For the coated electrode, a Sigracell GFD 2.5 carbon fleece was dipped several times in an ink consisting of 90% by weight Fe ₃ Ni ₆ S ₈ and 10% by weight PTFE and dried at 80°C until the desired catalyst loading (5 mg*cm ^-2 ) was reached. In contrast to Example 1, a 1M MBY solution in 0.3M KOEI/EI2O was used as the conductive salt/solvent, carried out at 80 mA cm ^-2 and in a solid electrolyte cell. The electrodes produced achieved a Faraday efficiency of 25% in terms of MBE and 5% in terms of MBA at a cell voltage of 2.5 V.

For a pressed catalyst mass electrode, a mixture of Kynar Superflex 2501 PVDF and Fe _4.5 Ni ₄ . ₅ S ₇ Se was mixed together using an IKA M20 knife mill. The mass produced was hot-pressed at 170° C. and a contact pressure of 1 kN cm ^-2 . Alternatively, other thermoplastics can also be used instead of PVDF. Optionally, conductive additives can be added to increase the conductivity between the active sites. In contrast to Example 1, a 1M MBY solution in 0.3M KOH/H ₂ O was again carried out as the conductive salt/solvent and in a solid electrolyte cell. Table 6 shows the required cell voltages (U/V) for a current density of 80 mA cm ^-2 in the solid electrolyte cell.

Table 6 For an electrode with a catalyst mass pressed onto a metal grid, a mixture of Kynar Superflex 2501 PVDF and Fe ₃ Co ₃ Ni ₃ S ₈ was milled using an IKA M20 knife mill. The mass produced was pressed onto a stainless steel grid (Flaver & Boecker, 0.2 mm×0.16 mm) at 170° C. and a contact pressure of 2 kN cm ^-2 . The electrode produced has increased mechanical stability. In contrast to Example 1, a 1M MBY solution in 0.3M KOH/H ₂ O was again carried out as the conductive salt/solvent and in a solid electrolyte cell. Table 7 shows the required cell voltages (UA/) for a current density of 80 mA cm ^-2 in a solid electrolyte cell. Table 7

II. Electrocatalysis with a flow cell

The method according to the invention was initially carried out using an electrochemical cell in batch operation. Figure 3 shows a schematic view of an electrochemical flow cell 101 with two half-cells 102, 103. The cathode half-cell 103 contains the catholyte chamber 135, the cathode with the actual electrode 133 and the end plate 131 and the reference electrode 136. The catholyte Chamber 135 is supplied with catholyte from reservoir 138 via pump 137 . In addition to the anolyte chamber 125, the anode Elalb cell 102 contains the anode with the actual electrode 123 and the end plate 121. The anolyte chamber 125 is supplied with anolyte from the reservoir 127 via a pump 126. An ion exchange membrane 104 (in the following examples, for example, a cation exchange membrane FS-10120-PK was used) is provided between the two chambers 102, 103. A plurality of seals 122, 124, 132, 134 and the membrane-retaining seals 105, 106 are arranged in between.

The transition metal chalcogenide-containing electrodes were produced by applying a porous carbon-containing carrier material, for example a carbon fiber fabric, a mixture of the transition metal chalcogenide with a binder, for example PTFE, was sprayed on or applied to the carrier material in the form of a hot-pressable mass. Spraying can be done, for example, using 15 mL of an ink made of 5% by weight PTFE and 85% by weight Fe ₃ Ni ₆ S ₈ onto a 10 cm x 10 cm W1S1010 CeTech Carbon Cloth, with a catalyst loading of 2 mg cm ^{- 2} is reached. The stress pressing is carried out using a mixture of ground PTFE powder with the transition metal chalcogenide catalyst and a 10 cm x 10 cm carbon substrate, which has an active area of 9 cm x 7 cm.

In this way, larger electrode surfaces can be produced much more easily. Compared to the cells described under I., significantly higher current densities can also be realized with these larger-area electrodes, for example current densities of up to 1 A cm ^-2 .

Example 7 - Electrocatalytic hydrogenation of MBY with pentlandite-coated electrodes with different binders and current densities

In a flow cell according to FIG. 3, a 1 M solution of MBY in 0.3 M KOFI in H ₂ O using an electrode with a catalyst loading of pentlandite Fe ₃ Ni ₆ S ₈ (F production as in Example 1) of 2 mg cm ^{- 2} hydrogenated at room temperature. The electrolyte chamber has a volume of 15 mL, the flow rate is 8 mL min ^-1 . The electrocatalytic reduction was carried out for 2 hours. The cathode was prepared by spraying the catalyst onto the substrate by means of an ink, the size of the electrode with one side spray coating obtained as described above being 7.1 cm ^-2 . The ink contains (A) 258 pL of a 60% by weight PTFE dispersion as a binder, 15g of a 1% by weight methylcellulose (MC) in water as an inert additive, 5g of water as a solvent and 1g of the catalyst or (B) 258 pL of a 60% by weight PTFE dispersion as a binder and 15g isopropanol (IPA) and 5g water as a solvent and 1g of the catalyst.

Figure 4A shows for a current density of -100 mA cm ^-2 that the composition of the ink has little effect on the required potential. Figure 4B shows, however, that when using IPA inks slightly better yields (Y) and Faraday efficiencies (FE) and a slightly better selectivity in terms of stopping the Reduction in the alkene (MBE) is recorded and only relatively little alkane (MBA) is formed. The slightly better yields with the IPA ink are probably due to better exposed active centers.

Figures 5A and 5B show the influence of current density on the required potential (EL/) and on the yield (Y) and Faraday efficiency (FE) for the IPA-based ink. It turns out (Fig. 5A) that the current density has no significant influence on the required potential. The Faraday efficiency decreases at higher current densities (CD); however, yield and selectivity (MBE/MBA) remain fairly constant (Figure 5B). Example 8 - Electrocatalytic hydrogenation of MBY with pentlandite-coated electrodes with different binder contents

The implementation of example 8 corresponds to that of example 7/IPA ink with the difference that the ink used contains a varying content of the binder PTFE. Tests were carried out with 10, 15 and 25% by weight of PTFE based on the total weight of the catalyst layer.

FIGS. 6A and 6B show the influence of the binder content on the required potential (E/V) and on the yield (Y) or Faraday efficiency (FE). It can be seen (FIG. 6A) that an increased binder content has only a very small influence on the required potential. However, Faraday efficiency and yield decrease slightly; the selectivity (MBE/MBA) remains fairly constant. From this it can be deduced that a significantly increased proportion of binder has a positive effect on the mechanical stability; too high a binder content, however, usually leads to lower yields.

Example 9 - Electrocatalytic Hydrogenation of MBY with Pentlandite Coated

Electrodes with Different Catalyst Loadings The implementation of example 9 corresponds to that of example 7/IPA ink with a PTFE content of 10% by weight, with the difference that more ink was sprayed onto the carrier material. The spraying process was carried out until a loading of 0.6, 1, 2 or 5 mg cm ^-2 could be detected. FIGS. 7A and 7B show the influence of the catalyst loading (CL) on the required potential (E/V) and on the yield (Y) or Faraday efficiency (FE). It turns out (Fig.

7A) that very low catalyst loadings lead to a deterioration in terms of the potential to be applied. However, increasing the loading from a value of 1 mg cm ^-2 does not result in any significant changes. Has very little impact on the required potential. Higher loadings, however, lead to higher yields; the selectivity (MBE/MBA) remains fairly constant.

Example 10 Electrocatalytic Hydrogenation of MBY with Pentlandite-Coated Electrodes with Different Catalysts and Different Membranes In contrast to Example 7, the polymer electrolyte membranes of the flow cell were varied. On the one hand, a proton exchange membrane (PEM) was used (Fumatech BWT GmbEI (FS-10120-PK)); on the other hand, an anion exchange membrane (AEM) (Fumatech BWT GmbEI (FM-FAA-3-PK-130)). Furthermore, in contrast to Example 7, different catalysts were used. The inks used for this correspond to those from Example 7 / IPA base, although

15 wt .-% PTFE were used as a binder. The catalyst loading was in each case

2 mg cm ^-2 .

FIGS. 8A and 8B show the influence of the membrane (PEM or AEM) on the required potential (EL/) and on the yield (Y) or Faraday efficiency (FE). It turns out (Fig.

8A) that the proton exchange membranes consistently lead to better results in terms of the required potential. However, if the catalyst used is also taken into account, it is found that there are different catalyst/membrane combinations that are particularly advantageous.

In terms of potential, the selenium-containing catalyst Fe _4.5 Ni _4.5 S ₄ Se ₄ is best in PEM and about equal to Fe ₂ Co ₄ Ni ₃ S ₈ ; in the AEM, on the other hand, Fe ₂ Co ₄ Ni ₃ S ₈ is slightly worse than the other two catalysts. A different picture emerges for yields and Faraday efficiencies. Here, Fe ₃ Ni ₆ S ₈ delivers the best results for both membranes, with these being significantly better for the anion exchange membrane than for the proton exchange membrane. However, Fe _4.5 Ni _4.5 S ₄ Se ₄ shows a somewhat poorer selectivity with regard to the MBE/MBA ratio. In summary, it can be stated that the proton exchange membranes are somewhat more energy efficient, since the required potential is lower, but in return also deliver lower yields.

Example 11 - Electrocatalytic Hydrogenation of MBY with Pentlandite-Coated Electrodes at Different Temperatures In contrast to example 7, the hydrogenation reactions were carried out at different temperatures.

FIGS. 9A and 9B show the required potential (E/V) and the yield (Y) or Faraday efficiency (FE) for different reaction temperatures. As a result, for higher temperatures, the potential required is somewhat lower; however, the yield and Faraday efficiency are slightly higher at room temperature. A significant influence on the selectivity is not observed.

Example 12 - Electrocatalytic hydrogenation of MBY with pentlandite-coated electrodes in a solid electrolyte cell

Figure 10 shows a schematic view of a solid electrolyte cell 201 with two half-cells 202, 203. In addition to the cathode flow field 234, the cathode half-cell 203 contains the cathode with the actual electrode 235, the conductor plate 233 and the end plate 231 as well as the plastic spacer 232. The cathode flow field 234 is supplied with catholyte from the reservoir 237 via a pump 236 . In addition to the anode flow field 224, the anode half cell 202 contains the anode with the actual electrode 225, the conductor plate 223 and the end plate 221 as well as the plastic spacer 222. The anode flow field 224 is supplied with anolyte from the reservoir 227 via a pump 226. An ion exchange membrane 204 is provided between the two chambers 202, 203. A plurality of seals 205, 206 are arranged in between.

In contrast to example 7, no liquid electrolyte but a polymer electrolyte system was used. Instead of the FS-10120-PK cation exchange membrane, an FM-FAA-3-PK-130 anion exchange membrane was used. Furthermore, the IPA ink was used as in Example 7, but with a PTFE content of 10% by weight. The Current density was only -80 mA cm ^-2 instead of -100. A Faraday efficiency of 67% (in terms of MBE) was achieved at a cell voltage of -2.5 V.

Example ₁₃ _{Electrocatalytic} _{Hydrogenation} of _MBY in a Solid Electrolyte Cell with Pentlandite Electrodes at Different Current Densities different currents repeatedly. Table 8 shows that with the same reaction times (2 hours) and higher current densities, the Faraday efficiency decreases; however, the yield increases.

Further increases in selectivity and conversion for the targeted lytion products at higher current densities can be achieved by adjusting the electrolyte used.

Table 8

Example 14 - Electrocatalytic hydrogenation of MBY in a solid electrolyte cell with pentlandite electrodes with different binders

For the reaction according to Example 12, the binders of the pentlandite coating were also varied. In addition, different ion exchange membranes were used: the anion exchange membranes Piperion A80 (Versogen) and FM-FAA-3-PK-130 (Fumatech) and the cation exchange membrane Nafion 115 (lonPower). Fluorine-containing polymers as well as the ionomers Piperion (Versogen), Aemion (lonomr) and Nafion (lonPower) were used as binders. The ionomers mentioned not only have the function of a binder but also the function of an additive that increases conductivity. The electrodes examined were produced using an IPA ink with a binder loading of 10% by weight and a catalyst loading of 2.5 mg cm ^-2 on a W1 S1010 carbon cloth (CeTech). The reaction according to Example 10 was carried out at 80 mA cm ^-2 using the membranes mentioned and the coated electrodes. Table 9 shows the influence of different binders on the hydrogenation reaction.

Table 9

Depending on the combination used, the Faraday efficiency for hydrogenation changes. Hydrophobic binders such as the mentioned fluorine-containing polymers generally show a higher Faraday efficiency for electrochemical hydrogenation (as can be shown with PTFE, Nafion and PVDF).

Example 15 Electrocatalytic Hydrogenation of MBY in a Solid Electrolyte Cell Using Different Catalysts (Comparative Experiment) To compare the reaction according to the application, the reaction according to Example 12 was also carried out with electrocatalysts according to the prior art. For comparison, Pd-based electrodes (current industrial state-of-the-art) with Pd particles (Alfa Aesar, 0.35-0.8 miti) were generated analogously to example 12. Furthermore, Ni foam (1.6 mm, Goodfellow) was used directly as the electrode material. Table 10 shows the influence of the electrocatalyst on the hydrogenation of MBY. The

Reaction was again carried out according to Example 12 with a 1 M MBY solution in 0.3 M KOH/H ₂ O as conductive salt/solvent at 80 mA cm ^-2 . The Fe ₃ Ni ₆ S ₈ catalyst shows slightly better Faraday efficiencies and cell voltages than the industrial Pd standard. Compared to the Ni foam, the Fe ₃ Ni ₆ S ₈ shows a significantly higher activity and selectivity for the flydration. Tab.10

Example 16 - Electrocatalytic hydrogenation of aromatic alkynes and aldehydes with pentlandite catalysis

To produce the electrode, the IPA ink with a PTFE content of 10% by weight was sprayed onto a carbon fleece (Sigracell GFD 2.5). An Fe ₃ Ni ₆ S ₈ coating was applied with a loading of 5 mg cm ^-2 . Analogously to Example 7, the reaction of a 1 M phenylacetylene solution in 0.3 M KOFI/MeOFI as conductive salt/solvent was carried out at a current density of 80 mA cm ^-2 . A cation exchange membrane (Nafion 115) was used in the solid electrolyte cell. A Faraday efficiency of 30% (with respect to phenylethylene) was achieved at a cell voltage of 2.2 V during the flydration. The flydriation of a 1 M benzaldehyde solution in 0.3 M sodium acetate/MeOFI as conductive salt/solvent was carried out with the same electrode under the same conditions. A Faraday efficiency of 10% (with respect to benzyl alcohol) was achieved at a cell voltage of 4.0 V.

Claims

patent claims

1 . A method for the electrocatalytic hydrogenation of organic compounds in an electrochemical cell comprising a cathode, an anode and an electrolyte, the reducible organic compound being present in liquid or at least partially dissolved form and the reducible organic compound being hydrogenated at the cathode, wherein the cathode comprises or consists of a transition metal chalcogenide catalyst, the transition metal chalcogenide being selected from sulphides, selenides and tellurides.

2. The method according to the preceding claim, wherein the reducible organic compound has at least one multiple bond and in particular comprises at least one CC multiple bond, CO double bond, CN multiple bond, NO ₂ group or NN multiple bond and/or an aromatic or heteroaromatic one connection is.

3. The method according to any one of the preceding claims, wherein the reducible organic compound comprises at least two different reducible functional groups.

4. The method according to any one of the preceding claims, wherein the transition metal chalcogenide essentially corresponds to the molecular formula MX, MX ₂ , M ₂ X ₃ , M ₂ X _4I M ₃ X _4I M ₉ X _8I or M" ₆ M _k X _m X' _n , where M is one or more metals selected from the transition metals of the 4th, 5th or 6th period and

M" is selected from alkali and alkaline earth metals, where X is S, Se and Te, and

X ¹ is a halide and k, m and n are decimal numbers with 24≦k≦25, 26≦m≦28 and 0≦n≦1.

5. The method according to the preceding claim, wherein the transition metal chalcogenide essentially has the molecular formula M ₂ X ₄ , M ₉ X ₈ , or M" ₆ M _k X _m X' _n and M selected from a 4th period transition metal of groups 4 to 10, and in particular one, two or three of the metals Fe, Co and Ni or at least one or more of these metals.

6. The method according to one of the two preceding claims, wherein the transition metal chalcogenide corresponds to the formula M ₉ X ₈ and is present at least partially crystallized in the pentlandite structure and in particular a compound of the formula Fe _9-abc Ni _a Co _b M' _c S _{8- d} Se _d is where

- M ¹ is a transition metal of the 4th, 5th or 6th period and is selected in particular from one or more metals from the group consisting of Ag,

Cu, Zn, Cr, Nb,

- a is a number from 0 to 7, in particular from 1 to 6

- b is a number from 0 to 9, in particular from 0 to 8

- c is a number from 0 to 2, in particular from 0 to 1 - d is a number from 0 to 6, in particular from 0 to 4

- where the sum a+b+c is a number from 0 to 9, in particular from 3 to 7.

7. The method according to the preceding claim, wherein the transition metal chalcogenide corresponds to Fe _9-abc Ni _a Co _b _M'c S _8-d Se _d and the compound contains essentially only two of the three elements Fe, Ni and Co and additionally essentially no metal M ¹ is included.

8. The method according to any one of the preceding claims, wherein the electrocatalytic flydration is carried out in batch mode or in continuous flow mode.

9. The method according to any one of the preceding claims, wherein the applied current density is greater than 10 mA cm ^-2 , in particular greater than 100 mA cm ^-2 .

10. Electrode for the electrocatalytic flydration of organic compounds in an electrochemical cell, in particular by means of the method according to any one of the preceding claims, with a support material and a catalyst layer arranged at least on part of the surface of the support material, the catalyst layer containing a polymeric binder and a transition metal chalcogenide as a catalyst or consisting of these components, the transition metal chalcogenide being selected from sulfides, selenides and tellurides.

11. Electrode according to the preceding claim, wherein the catalyst layer is porous or the carrier material is at least partially formed from a porous material and the catalyst layer is at least partially arranged as a coating on the inner surface of the porous carrier material.

12. Electrode according to one of the preceding claims, wherein the polymeric binder is selected from polyolefins, fluorinated polyolefins, copolymers with polyolefins and/or fluorinated polyolefins and polymer blends containing polyolefins and/or fluorinated polyolefins, the polyolefins and fluorinated polyolefins being selected in particular from the group consisting of PE, PP, PVDF, FEP and PTFE.

13. Electrode according to one of the preceding claims, wherein the proportion of the binder in the catalyst layer is 1 to 90% by weight, in particular 5 to 80% by weight, for example 10 to 25% by weight.

14. Electrode according to one of the preceding claims, wherein the catalyst layer contains or consists of the transition metal chalcogenide, optionally a binder and at least one additive, wherein the at least one additive is selected from substances for increasing the electrical conductivity, substances for increasing the ion conductivity, Substances to increase thermal conductivity, substances to increase corrosion resistance, substances to increase electrophobicity and substances to improve adsorption of the organic compound to be hydrogenated.

15. Electrode according to one of the preceding claims, wherein the catalyst layer has a catalyst loading of 0.1-500 mg cm ^-2 , in particular 1-250 mg cm ^-2 , for example 2-10 mg cm ^-2 .

16. Electrode according to one of the preceding claims, wherein the transition metal chalcogenide essentially corresponds to the molecular formula MX, MX ₂ , M ₂ X ₃ , M ₂ X _4I M ₃ X _4I M ₉ X ₈ , M'' ₆ M _k X _m X' _n , where M is one or more metals selected from the transition metals of the 4th, 5th or 6th period and

X ¹ is an elalogenide and k, m and n are decimal numbers with 24≦k≦25, 26≦m≦28 and 0≦n≦1.

17. The electrode according to the preceding claim, wherein the transition metal chalcogenide essentially corresponds to the empirical formula M ₂ X ₄ , M ₉ X ₈ , or M" ₆ M _k X _m X' _n and M selected from a transition metal of the 4th period of groups 4 to 10, and in particular one, two or three of the metals Fe, Co and Ni or at least one or more of these metals.

18. Electrode according to one of the two preceding claims, wherein the transition metal chalcogenide corresponds to the formula M ₉ X ₈ and is present at least partially crystallized in the pentlandite structure and in particular a compound of the formula Fe _9.abc Ni _a Co _b M' _c S _{8. d} Se _d is where

- M ¹ is a transition metal of the 4th, 5th or 6th period and is selected in particular from one or more metals from the group consisting of Ag, Cu, Zn, Cr, Nb,

- a is a number from 0 to 7, in particular from 1 to 6

- b is a number from 0 to 9, in particular from 0 to 8

- c is a number from 0 to 2, in particular from 0 to 1

- d is a number from 0 to 6, in particular from 0 to 4

- where the sum a+b+c is a number from 0 to 9, in particular from 3 to 7.

19. Electrode according to one of the preceding claims, wherein the carrier material is selected from metals, carbon, ceramic materials, polymers and composite materials.

20. Electrode according to one of the preceding claims, wherein the carrier material is flat and is selected from fabric layers, felts, grids, membranes and foils.

21. Electrode according to one of the preceding claims, wherein the catalyst layer has an outer surface area of at least 0.2 cm ² , in particular at least 1 cm ² , preferably 1 cm ² to 4 m ² .

22. Electrochemical cell for the electrocatalytic lydration of organic compounds, having a reactor containing a cathode, an anode and an electrolyte, wherein a reducible organic compound is present in liquid or at least partially dissolved form in the reactor and wherein the reducible organic compound is hydrogenated at the cathode, wherein the cathode comprises or consists of a transition metal chalcogenide as a catalyst, wherein the transition metal chalcogenide is selected from sulphides, selenides and tellurides, and in particular an electrode according to any one of claims 9 to 19 and wherein the electrochemical cell is not for generation of a gas is formed.

23. Use of a transition metal chalcogenide as a catalyst for the electrocatalytic lydration of organic compounds, in particular a transition metal chalcogenide selected from compounds which essentially have the molecular formula MX, MX ₂ , M ₂ X ₃ , M ₂ X ₄ , M ₃ X ₄ , M ₉ X ₈ or M" ₆ M _k X _| X' _m , for example a pentlandite, where M is one or more metals selected from the transition metals of the 4th, 5th or 6th period and M" is selected from alkali and alkaline earth metals, where X stands for S, Se and Te and X' is a halide and k, m and n are decimal numbers with 24≦k≦25, 26≦m≦28 and 0≦n≦1.