Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds
  • C25B3/20—Processes
  • C25B3/25—Reduction
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
  • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
  • C25B11/031—Porous electrodes
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
  • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
  • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
  • C25B11/095—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one of the compounds being organic

Definitions

• the present invention relates to a gas diffusion electric ⁇ de comprising, preferably copper-containing one support and a first layer comprising at least copper and at least one binder, wherein the (first) layer hydrophilic and hydrophobic pores and / or channels comprises, further comprising comprising a second layer of copper and at least one binder, wherein the second layer is on the carrier and the first layer is on the second layer, wherein the content of binder in the first layer is smaller than in the second layer, a method for producing such a gas diffusion electrode and an electrolytic cell comprising such a gas diffusion electrode.
• Energy amount corresponds ideally to the combustion energy of the fuel and should come only from renewable sources or use electricity that just can not be taken off the grid.
• an overproduction of renewable energies is not continuously available, but currently only at times with strong sunlight and / or strong wind.
• this will continue to increase or even out in the near future as the installations are located in different locations.
• Table 1 shows the typical Faraday efficiencies (FE) on different metal cathodes.
• FE Faraday efficiencies
• CO 2 is almost exclusively reduced to CO at Ag, Au, Zn, and with restrictions on Pd, Ga
• copper has a large number of hydrocarbons as reduction products.
• pure metals and metal alloys and mixtures of metal and metal oxide which is co-catalytically effective interest since they increase the Se ⁇ selectivity of a particular hydrocarbon Kings ⁇ nen.
• this is the state of the art is not very pronounced.
• the electrode In order to be able to provide all these crystallographic surfaces for a high ethylene-forming efficiency at high current density, the electrode must not consist of a smooth metal sheet, but should be micro- to nanostructured.
• the accessibility of such catalytically active centers limits the ethylene formation to a Faraday efficiency of about 20% or limits the achievable current density
• Electrolysis be achieved, as determined in their own work. With electrodes made in this way, however, the selectivity of the electrode may decrease with duration, which may lead to an increase in hydrogen production. A temporal change in the selectivity can be correlated with a structural coarsening of the material, which was also observable for example on the basis of microscopic images.
• a selective catalyst nano-dendritic Cu structures were identified that contain both Cu ° and Cu 1 in the form of CU 2 O.
• GDE gas diffusion electrodes
• Silver / silver oxide / PTFE (polytetrafluoroethylene) -based gas diffusion electrodes have recently been used industrially for the production of caustic soda in the existing chloralkali electrolyte (oxygen-consuming) process.
• the efficiency of the chloralkali electrolysis process could be increased by 30-40% unlike conventional electrodes.
• PTFE is known from a variety of publications and patents.
• Said wet process 1 may in this case have the stated hereinafter disadvantages, apart from the fact that known from the literature examples of gas diffusion electrodes containing the catalyst only as an additive and consist mainly of bound conductive carbon (for high conversions should Ka ⁇ talysatorbeladung be high):
• the suspensions or pastes usually applied by spraying or knife application generally have long drying times, which means that continuous production with larger (technically relevant) electrode surfaces is not economically possible. Too fast drying leads to the formation of cracks, so-called "mud cracking", within the applied layers, whereby the electrode is unusable.
• the porosity of the applied layer is determined in the nassche ⁇ mix method almost exclusively by the evaporation of the solvent (generated). This process is strongly solvent- or boiling point-dependent and can lead to a high rejection rate of the electrodes thus produced, since the evaporation can not be uniformly ensured over the entire surface.
• Thickeners to call plasticizing which are used to stabilize the particle suspensions, as they can not be removed without residue by the corresponding Trocknungspha ⁇ sen or the thermal crosslinking process.
• the embedding method 2 by using, instead of PTFE Nafion® (perfluorosulfonic; perfluorosulfonic acid, PFSA) which is used as Bin ⁇ also has corresponding disadvantages, since a wet chemical method is applied using appropriate surfactants.
• Nafion® itself a hydrophilic ionomer, which has strongly acidic R-HSO 3 groups, which in some catalysts can lead to undesirable acid corrosion or partial dissolution of the metal.
• Nafion®-bonded layers furthermore have a much lower porosity than PTFE Tied ⁇ ne.
• Nafion® is not suitable for the formation of hydrophobic channels due to the hydrophilic properties, which are advantageous for gas transport within a gas diffusion electrode.
• Applicable electrodes comprising Nafion® should therefore consist of several layers in order to realize the essential properties of a GDE.
• multi-layer coating processes are less attractive host ⁇ regards aspects.
• Nafion®-based compounds can also lead to the undesirable formation of hydrogen.
• the dry process 3. is based on a roll calendering process, for example of PTFE / catalyst powder.
• the corresponding technology is due to the EP 0297377 A2, in accordance with the electrodes on MN20 3 -based batteries Herge ⁇ provides were.
• DE 3710168A1 refers to the use of the drying process with regard to the preparation of metallic electrocatalyst electrodes.
• the technique was further silver-based in patents for the preparation of (silver (I) - or silver (11) oxide) ⁇ gas diffusion electrode (oxygen consuming electrodes) are used.
• the patents EP 2444526 A2 and DE 10 2005 023615 A1 mention mixtures which have a binder content of 0.5-7%.
• the carriers used were Ag or nickel nets with a wire diameter of 0.1-0.3 mm and a mesh width of
• EP 2410079 A2 describes the one-step process for producing a silver-based oxygen-consuming electrode with the addition of metal oxide additives such as Ti0 2 , Fe 3 0 4 , Fe 2 0 3 , Ni0 2 , Y 2 0 3 , Mn 2 0 3 , Mn 5 0 8 , W0 3 , Ce0 2 and spinels such as CoAl 2 0 4 , Co (AlCr) 2 Ü4 and inverse spinels such as (Co, Ni, Zn) 2 (Ti, Al) 0 4 , perovskites such as LaNi0 3 , ZnFe 2 0 4 .
• metal oxide additives such as Ti0 2 , Fe 3 0 4 , Fe 2 0 3 , Ni0 2 , Y 2 0 3 , Mn 2 0 3 , Mn 5 0 8 , W0 3 , Ce0 2 and spinels such as CoAl 2 0 4 , Co (AlCr) 2 Ü4 and
• noble metals e.g. Pt, Rh, Ir, Re, Pd
• noble metal alloys e.g. Pt-Ru
• noble metal-containing compounds e.g.
• the method describes how by means of three coating cycles a hydrophobic gas Trans ⁇ port layer and based on three other coatings, a catalyst-containing layer is applied. After each layer, a drying phase (325 ° C) takes place with subsequent static pressing (1000- 5000Psi). For the obtained ⁇ nen electrode a Faraday efficiency of> 60% and a current density of> 400mA / cm 2 was specified. Reproduction experiments, which are given as comparative examples below, prove, however, that the described static pressing method does not lead to stable electrodes. A negative influence of the mixed volcano XC 72 was also found, so that likewise no hydrocarbons were obtained.
• DE 101 30 441 A1 discloses a biporoid pore system in a gas diffusion electrode, but not a two-layer structure.
• a flood of the electrode was observed in its own preliminary experiments.
• a single-layer structure can also be used, for example
• US 2013/0280625 A1 discloses a two-layer structure of a gas diffusion electrode, which, however, does not disclose any hydrophobic pores, but only pores in the diffusion layer as a hydrophilic layer. In it, a sacrificial material is necessarily used, which is required for the formation of pores, but our own preliminary tests have shown that this is not expedient.
• H + is for ethylene or alcohols like
• the present invention relates to a gas diffusion electrode, comprising a, preferably copper-containing, carrier, preferably in the form of a sheet, and a first layer comprising at least copper and at least one binder, wherein the first layer hydrophilic and hydrophobic pores and or channels, further comprising a second layer comprising copper and at least one binder, wherein the second layer is on the carrier and the first layer on the second layer, the content of binder in the first layer being smaller than in the second layer.
• the present OF INVENTION ⁇ dung relates to a method for preparing a gas diffusion electrode comprising
• the proportion of binder in the second mixture is 3-30% by weight, preferably 10-30 % By weight, more preferably 10-20% by weight, based on the second mixture, and wherein the proportion of binder in the first mixture is 0-10% by weight, preferably 0.1-10% by weight, more preferably 1-10% by weight, more preferably 1-7% by weight, even more preferably 3-7% by weight, based on the first mixture, wherein the content of binder in the first mixture is smaller than in the second mixture ; or comprehensive
• the present invention relates to an electrolytic cell comprising the erfindungsge ⁇ Permitted gas diffusion electrode.
• FIG. 1 shows a schematic representation of a modern fiction, ⁇ gas diffusion electrode with hydrophobic and hydrophi ⁇ len areas or channels.
• Figure 2 shows a schematic representation for producing a gas diffusion electrode according to the invention on the basis of egg ⁇ nes exemplary PTFE-bound catalyst.
• FIG. 3 schematically illustrates a further embodiment of a gas diffusion electrode according to the invention in the form of a multilayer preparation.
• Figures 4 to 6 schematically exemplary illustrations of a possible structure of an electrolytic cell are shown in accordance with egg ⁇ ner embodiment of the present invention.
• Figures 7 and 8 show exemplary embodiments for a gas distribution chamber behind a gas diffusion electrode according to the invention in an electrolysis ⁇ cell according to the invention.
• FIG. 9 shows the results of Faraday efficiencies of the electrolytic cell of Comparative Example 3.
• FIGS. 10 and 11 show the results of Faraday efficiencies of the electrolysis cell of Comparative Example 4.
• hydrophobic is understood as meaning water-repellent. Hydrophobic pores and / or channels according to the invention are therefore those which repel water. In particular, hydrophobic properties are associated according to the invention with substances or molecules with nonpolar groups.
• hydrophilic is understood as the ability to interact with water and other polar substances.
• the present invention relates to a gas diffusion electrode comprising
• a, preferably copper-containing, carrier preferably in the form of a sheet
• a first layer comprising at least copper and at least one binder, wherein the (first) layer comprises hydrophilic and hydro ⁇ phobe pores and / or channels, further comprising a second layer comprising copper and at least one binder, wherein the second layer is on the carrier and the first layer is on the second layer, wherein the content of binder in the first layer is smaller than in the second layer.
• the second layer may, like the first layer, hydro ⁇ hydrophilic and / or hydrophobic pores and / or channels comprise.
• a gas diffusion electrode comprising a, preferably copper-containing, carrier, preferably in the form of a sheet, and
• a first layer comprising at least copper and at least one binder, the layer comprising hydrophilic and hydrophobic pores and / or channels.
• Figure 1 illustrates the relationships between hydrophilic and hydrophobic regions of a GDE, which can achieve a good three-phase relationship liquid, solid, gaseous.
• inactive catalyst centers 5 are located on the gas side.
• Particularly active centers are located in four Dreiphasenge ⁇ Biet liquid, solid, gaseous.
• An ideal GDE thus has a maximum permeation of the bulk material with hydrophilic and hydrophobic channels in order to obtain as many as possible three-phase areas for active catalyst centers.
• the first layer hyd ⁇ rophile and hydrophobic pores and / or channels comprises.
• the support here is not particularly limited insofar as it is suitable for a gas diffusion electrode and is preferably copper-containing.
• parallel wires can form a carrier in extreme cases.
• the support is a sheet, more preferably a mesh, most preferably a copper mesh.
• the carrier can also be suitably adjusted with respect to the electrical Leitfä ⁇ ability of the first layer. By Ver ⁇ application of copper in an appropriate carrier conductivity can be provided resistance and the risk of introduction of unwanted foreign metals can be reduced.
• the carrier is therefore made of copper.
• a preferred copper-containing carrier is, according to certain embodiments, a copper mesh with a mesh size w of
• the first layer comprises copper, and a high electrical conductivity of the catalyst so as ⁇ , in particular in conjunction with a copper grid, a homogeneous potential distribution across the entire surface Elektrodenflä ⁇ (potential-dependent product selectivity) can be ensured.
• a preferably copper-containing network preferably the copper network used as the carrier, has a mesh size of the carrier between 0.3 and 2.0 mm, preferably between 0.5-1.4 mm in order to achieve a good Leit ⁇ ability and stability.
• the binder comprises a polymer, for example a hydrophilic and / or hydrophobic polymer, for example a hydrophobic polymer, in particular PTFE.
• a polymer for example a hydrophilic and / or hydrophobic polymer, for example a hydrophobic polymer, in particular PTFE.
• PTFE particles having a particle diameter between 5 and 95 ⁇ m, preferably between 8 and 70 ⁇ m, are used to produce the first layer.
• Suitable PTFE powders include beispielswei ⁇ se Dyneon® TF 9205 and Dyneon TF 1750.
• Suitable binders Parti ⁇ kel, for example, PTFE particles may for example be spherical in ⁇ approaching, for example spherical, and can be prepared for example by emulsion polymerization.
• the binder particles are free of surfactants.
• the particle size can be determined, for example, in accordance with ISO 13321 or D4894-98a and can correspond, for example, to the manufacturer's instructions (eg TF 9205: mean particle size 8ym according to ISO 13321, TF 1750: mean particle size 25ym according to ASTM D4894-98a).
• the first layer comprises at least copper, which may be present for example in the form of metallic copper and / or copper oxide and which acts as a catalyst center.
• the first layer contains metallic copper in the oxidation state 0.
• the first layer contains copper oxide, in particular CU 2 O.
• the oxide can contribute to stabilizing the oxidation states +1 of the copper and thus to maintain the selectivity for ethylene in the long-term stable. Under electrolysis conditions it can be reduced to copper.
• the first layer comprises at least 40 At. % (Atomic percent), preferably at least 50 at.%, More preferably at least 60 at. % Copper, based on the layer. This allows both a suitable mechanical see stability as well as a suitable catalytic crei ⁇ ty this first layer as a catalyst layer
• the copper for producing the gas diffusion electrode according to the invention is provided as particles, which are further defined below.
• the first layer may also hold other promoters ent ⁇ which improve in cooperation with the copper, the catalytic activity of the GDE.
• the first layer at least one metal ⁇ oxide, which preferably has a lower reduction potential than the ethylene development, preferably ZrÜ 2, Al 2 O 3, CeÜ 2, Ce 2 ⁇ 0 3, ZnÜ 2, MgO; and / or at least one copper-rich intermetallic phase, preferably at least one Cu-rich phase, which is selected from the group of the binary systems Cu-Al, Cu-Zr, Cu-Y, Cu-Hf, CuCe, Cu-Mg and the ternary systems Cu-Y-Al, Cu-Hf-Al, Cu-Zr-Al, Cu-Al-Mg, Cu-Al-Ce with Cu contents> 60 At .-%; and / or copper-containing perovskites and / or defect perovskites and / or perovskite-related compounds, preferably YBa 2 Cu 3
• Preferred promoters here are the metal oxides.
• the metal oxide used is insoluble in water in accordance with certain execution ⁇ shapes, so that aqueous electrolytes may be used in an electrolysis using the gas diffusion electrode of the invention.
• the fact that the redox potential of the metal oxide is less than that of the ethylene development ensures that ethylene can be produced from CO 2 by means of the GDE according to the invention.
• the oxides should not be reduced in a carbon dioxide reduction. For example, nickel and iron are unsuitable because hydrogen is formed here.
• the metal oxides are preferably not inert, but should preferably represent hydrophilic reaction ⁇ centers, which can serve for the provision of protons.
• the promoters in particular the metal oxide, can in this case promote the function and production of long-term stable electrocatalysts by stabilizing catalytically active Cu nanostructures.
• the structural promoters can reduce the high surface mobilities of the Cu nanostructures and thus their sintering tendency.
• the concept originates from heterogeneous catalysis and is successfully used within high-temperature processes.
• Oxides are not added as additives, but are part of the catalyst itself.
• the oxide satisfied in addition to its radio ⁇ tion as a promoter also the feature copper in the oxidation state I and moreover also intermediates in the carbon dioxide reduction, such as CO, C 2 H 4 (or OH) to stabilize.
• the catalyst has the following inventive features: In contrast to the known and technically used heterogeneous catalysts CU / Al 2 O 3 , Cu / ZrO 2 , Cu / MgO / Al 2 O 3 are used for the electrochemical Reduction of CO 2 due to the required electrical conductivity according to certain embodiments preferably only very copper-rich catalysts with a mole fraction> 60 At. % Cu used.
• Gasdiffusi ⁇ onselektroden invention metal oxide copper catalyst structures which are prepared as follows.
• CU6AI 2 CO3 (OH) 1 6 .4 (H 2 O) which can be obtained in greater yield.
• the entspre ⁇ sponding precursors may be prepared by co-dosage of a metal salt solution and a basic carbonate pH are precipitated controlled. A special feature of these materials is the presence of ultra-fine copper crystallites with egg ⁇ ner size of 4-10 nm, which are stabilized struc ⁇ rell through the existing oxide.
• the metal oxide can lead to better distribution of the catalyst metal due to its high specific surface; fructis ⁇ perse metal centers can be stabilized by the metal oxide; the CO 2 chemisorption can be ver ⁇ pieces by the metal oxide; Copper oxides can be stabilized.
• the generated oxide predictors can also be used directly in be reduced to a H 2 / Ar gas stream, wherein only the CU 2 O or CuO is reduced to Cu and the oxide promoter is maintained.
• the activation step can also be carried out electrochemically in retrospect. In order to improve the electrical conductivity of the deposited layer prior to electrochemical activation, partial oxide precursors and activated precursors may also be mixed. In order to increase the Grundleitance also 0-10 wt.% Copper powder can be mixed in similar particle size.
• the finished calendered electrode is subjected to a subsequent Kalzi ⁇ discrimination / thermal treatment before the electro-chemical activation is performed.
• Another possibility of producing suitable electrocatalysts is based on the approach of producing copper-rich intermetallic phases such as, for example, CusZr, CuioZr 7 ,
• Cu5iZri 4 which can be produced from the melt. Corresponding ingots can subsequently be ground and calcined completely or partially in the 0 2 / argon gas stream and converted into the oxide form.
• Copper-rich phases are described, for example, by E. Kneller, Y. Khan, U. Gorres, The Alloy System Copper-Zirconium, Part I. Phase Diagram and Structural Relations, Zeitschrift für Metallischen 77 (1), pp. 43-48, 1986 for Cu-Zr phases, from
• the content of copper is preferably greater than 40 at.%, Further be ⁇ vorzugt greater than 50 at.%, Particularly preferably greater than 60 at.%.
• intermetallic ⁇ phases also contains non-metal elements such as oxygen, nitrogen, sulfur, selenium and / or phosphorus, so for example, oxides, sulfides, selenides, nirides and / or
• the intermetallic phases are partially oxidized.
• the following copper-containing perovskite structures and / or defect perovskites and / or perovskite-related compounds for electrocatalysts, in particular for the formation of hydrocarbons can be used: YBa 2 Cu 3 07-6, where 0 ⁇ ⁇ 1, CaCu 3 Ti 4 O 2 , Lai, 85 Sr 0 , 15, Cu0 3 , 930CI0, 053, (La, Sr) 2CUO 4 . Furthermore, it is not excluded that mixtures of these materials can be used for electrode preparation or, if necessary, subsequent calcination or activation steps are carried out.
• the catalyst particles comprising or consisting of copper, for example, copper particles, which are used to prepare the GDE according to the invention, a uniform particle size between 5 and 80 .mu.m, preferably 10 to 50 ym, more preferably Zvi ⁇ 's 30 and 50 ym , Furthermore, according to certain embodiments, the catalyst particles have a high purity without foreign metal traces. By suitable structuring, if appropriate with the aid of the promoters, high selectivity and long-term stability can be achieved.
• the promoters for example the metal oxides, may have an appropriate particle size in the production.
• the following properties can be achieved or improved by the above promoters:
• H + is for ethylene or alcohols like
• Cu powder aggregates having a particle diameter of 50 to 600 ⁇ m may be preferred
• the particle diameter of these aggregates is 1 / 3-1 / 10 of the total layer thickness, according to certain embodiments
• a gas diffusion electrode of the invention can insbesonde re ⁇ by the inventive manufacturing method Herge ⁇ provides, as described further below.
• the first layer comprises less than 5 wt.%, More preferably less than 1 wt.%, And even more preferably no carbon- and / or carbon black-based, for example, conductive, filler with respect to the layer.
• activated carbons Leitru hybrid (such as volcano XC72), Acetylenblack, or other coals point.
• Leitru hybrid such as volcano XC72
• Acetylenblack or other coals point.
• the present invention that much reduced traces of carbon and / or carbon black, the Selekti ⁇ vity of the catalyst to hydrocarbons and the undesired formation of hydrogen can be ⁇ cheap.
• the first layer in accordance with certain execution contains ⁇ forms no surfactants.
• the first and / or second layer also contain no sacrificial material, eg a sacrificial material with a release temperature of approximately below 275 ° C, for example of less than 300 ° C or below 350 ° C, in particular no Porenchan ⁇ ner, which or which Typically, when electrodes are fabricated using such material, they may remain at least partially in the electrode.
• the use of surfactants such as Triton X is therefore to be avoided according to certain embodiments, so that a wet-chemical procedure is not suitable for embedding Cu-based catalysts.
• the content or proportion of binder for example PTFE, according to certain embodiments, 3-30 wt.%, Preferably 3-20 wt.%, More preferably 3-10 wt. %, even more preferably 3-7% by weight, based on the one (first) layer.
• the GDE invention further comprises a second layer comprising copper and at least one binder, wherein the two ⁇ th layer is located on the support and the first layer on the second layer, wherein the content of the binder in the first layer is smaller than in the second Layer.
• the second layer coarser Cu or Inertmaterial- particles for example having particle diameters from 50 to 700 ym, preferably 100-450 .mu.m, include, to provide a suitable Ka ⁇ Nal or pore structure.
• the second layer here comprises 3 to 30% by weight of binder, preferably 10 to 30% by weight of binder, more preferably 10 to 20% by weight of binder, preferably> 10% by weight of binder, more preferably> 10% by weight. and up to 20% by weight of binder, based on the second layer, and the first layer of 0-10% by weight of binder, eg 0.1 to 10% by weight of binder, preferably 1 to 10% by weight of binder, more preferably 1 to 7% by weight, even more preferably 3 to 7% by weight of binder, based on the first binder
• the binder may in this case be the same as in the first layer, for example PTFE.
• the particles for producing the second layer may be the same as or different from those of the first.
• the second layer is in this case a metal particle layer (metal particle layer, MPL) che wel ⁇ below the catalyst layer (CL) is located.
• MPL metal particle layer
• CL catalyst layer
• Layer the first layer partially. This can e.g. can be achieved by the method according to the invention and allows a good transition between the layers with respect to the diffusion.
• the GDE according to the invention may also have further layers, for example on the first layer and / or on the other side of the support.
• a mixture for an MPL based on a highly conductive Cu mixture of dendritic Cu with particle sizes between 5-100 ⁇ m, preferably smaller than 50 ⁇ m and coarser Cu or inert material particles with particle sizes of 100 ⁇ m may be prepared.
• a multi-layer gas diffusion electrode as shown in Figure 3 is shown schematically, with a Cu network 8, an MPL 9 and a CL 10 can be obtained.
• Through the MPL can provide better mechanical stability, further reducing the penetration of electrolyte and better conductivity, especially when using nets as carriers.
• a stepwise production of the GDE by each sifting and rolling of each individual layer can lead to a lower adhesion between the layers and is therefore less preferred.
• the present invention relates to a method for producing a gas diffusion electrode, comprising
• Preparation of a first mixture comprising at least copper and at least one binder Applying the first mixture comprising at least copper and at least one binder to a, preferably copper-containing, carrier, preferably in the form of a sheet, and
• the content of binder in the mixture is 3-30% by weight, preferably 3-20% by weight, more preferably 3-10% by weight, still more preferably 3-7% by weight, based on the first mixture.
• the preparation of the first and second mixtures or of the first mixture is in this case not particularly limited and can be carried out in a suitable manner, for example by stirring, dispersing, etc.
• the first Mi ⁇ research% binder may also contain 0 wt. Include, thus no binder, because it can explode when rolling binder from the second mixture in the forming of the first mixture hineindiffun- first layer and thus also the first layer has a content of binder, for example, at least 0.1.%, beispielswei ⁇ se 0.5 wt.% as prepared in preliminary tests, may have.
• the first blend when applying 2 or more blends, contains binders.
• the binder comprises a polymer, for example a hydrophilic and / or hydrophobic polymer, for example a hydrophobic polymer, in particular PTFE.
• a polymer for example a hydrophilic and / or hydrophobic polymer, for example a hydrophobic polymer, in particular PTFE.
• PTFE particles having a particle diameter between 5 and 95 ⁇ m, preferably between 8 and 70 ⁇ m, are used to produce the first layer.
• Suitable PTFE powders include, for example, Dyneon® TF 9205 and Dyneon TF 1750.
• the copper is in the form of particles or catalyst for the preparation of the mixture.
• torparticles for example, dendritic copper, before, which have a uniform particle size between 5 and 80 ym, preferably 10 to 50 ym, more preferably between 30 and 50 ym.
• the catalyst particles in accordance with certain embodiments have a high purity without Fremdme ⁇ tallspuren.
• the particle sizes of copper and binder and optionally further additives such as promoters, the pores and / or channels, ie the hydrophobic and hydrophilic pores and / or channels, of the GDE can be adjusted specifically for the passage of gas and / or electrolyte and thus for the catalytic reaction.
• the first and / or second mixture contains no sacrificial material, e.g. a sacrificial material having a release temperature of approximately less than 275 ° C, e.g. of less than 300 ° C or less than 350 ° C, in particular no pore-forming agent, which may usually remain at least partially in the electrode when electrodes are produced using such a material.
• a sacrificial material e.g. a sacrificial material having a release temperature of approximately less than 275 ° C, e.g. of less than 300 ° C or less than 350 ° C, in particular no pore-forming agent, which may usually remain at least partially in the electrode when electrodes are produced using such a material.
• the first and / or second mixtures are not pasty, e.g. in the form of inks or pastes, but in the form of powder mixtures.
• the application of a first, second and further mixture (s) is not particularly limited and can be done, for example, by sprinkling, sifting, knife coating, etc.
• the rolling is not particularly limited and can be done appropriately. Rolling the mixture or mass (particles) into the structure of the carrier, for example a net structure, is according to certain embodiments expressly desired in order to ensure a high mechanical stability of the electrode.
• Layers prefers that the blends for the layers be applied one at a time to the backing and then rolled all together to provide better adhesion between the layers
• the layers can penetrate at least partially, for example in a thickness of 1 to 20 ⁇ m.
• the mechanical stress of the binder, for example of plastic particles, by the rolling process leads to crosslinking of the powder by the formation of binder channels, for example PTFE fibrils.
• binder channels for example PTFE fibrils.
• the achievement of this state is particularly important in order to guarantee a suitable porosity or me ⁇ chanische stability of the electrode.
• the hydrophobicity can be adjusted via the respective content of polymer or via the physical properties of the catalyst powder.
• a binder content in the second mixture is from 10-30% by weight, preferably 10-20% by weight, based on the second mixture, and a proportion of binder in the first mixture from 0-10% by weight, preferably 0.1-10% by weight, more preferably 1-10% by weight, even more preferably 1-7% by weight, still more preferably 3-7% by weight, as suitable proved.
• a binder for example PTFE, content of 3-30% by weight, preferably 3-20% by weight, more preferably 3-10% by weight, even more preferably 3, has been particularly suitable -7 wt.% Binder, based on the first mixture proved.
• the degree of fibrillation of the binder correlates directly with the applied shear rate, since the binder, for example a polymer, behaves as a shear-thinning (pseudoplastic) fluid upon swelling. After extrusion, the resulting layer has an elastic character due to the fibrillation. This structural change is irreversible, so that this effect can no longer be subsequently enhanced by further rolling, but the layer is damaged by the elastic behavior upon further action of shear forces. A particularly strong fibrillation can disadvantageously lead to a layer-side coiling of the electrode, so that too high contents of binder should be avoided.
• the serge What ⁇ halt example, a maximum corresponds to the room humidity during rolling.
• the content of water and Lö ⁇ sungsstoffn is in rolling less than 5 wt.%, Preferably less than 1 wt.%, And for example, 0 wt.%.
• the copper-containing carrier is a copper mesh with a mesh size w of
• a net such as a copper net
• the gaps in the net e.g. Copper net, bridged by the lying on top (for example, highly conductive) layer so to speak and a complete 3D contacting of the electrode are made possible. As a result, higher oxide levels are possible.
• the preparation of the gas diffusion electrode according to the invention is based on the exclusion of carbon and / or soot-based, for example conductive, fillers.
• a coal substitute here serves the catalyst itself or dendritic copper (eg formed by activation of the catalyst) or mixtures of both.
• the method according to the invention does not contain surface-active substances or thickeners and additives (such as flow improvers) which have been identified as catalyst poisons.
• the bulk height y of the first mixture on the carrier when applied is in the range of 0.3 mm ⁇ y ⁇ 2.0 mm, preferably 0.5 mm ⁇ y ⁇ 1.0 mm.
• each layer may have an appropriate bulk ⁇ height y, although the bulk heights of all layers is preferably not more than 2.0 mm, preferably not more than 1.5 mm, more preferably not more than 1 mm , addie ⁇ ren.
• the rolling is performed by a calender.
• the copper content in the mixture is at least 40 at.%, Preferably at least
• the mixture further comprises at least a metal oxide which has a lower Reduktionspo ⁇ tential than the ethylene development, preferably ZrÜ 2, A1 2 0 3, Ce0 2, Ce 2 0 3, Zn0 2, MgO;
• the mixture further comprises at least one copper-rich intermetallic phase, preferably at least one Cu rich phase selected from the binary systems Cu-Al, Cu-Zr, Cu-Y, Cu-Hf, CuCe, Cu-Mg and / or the ternary systems Cu-Y-Al, Cu-Hf-Al, Cu-Zr-Al, Cu-Al-Mg, Cu-Al-Ce with Cu contents> 60 at.%;
• the mixture is at least one metal to form a copper-rich metallic phase, preferably Al, Zr, Y, Hf, Ce, Mg, or at least two metals to form ternary phases, preferably Y-Al, Hf-Al, Zr-Al , Al-Mg, Al-Ce, so that the Cu content is> 60 at%;
• the mixture containing copper perovskites and / or defect perovskite and / or perovskite-related encryption bonds preferably 6 YBa2Cu307- X a, CaCu3Ti 4 0I2,
• metal to form a copper-rich metallic phase, preferably Al, Zr, Y, Hf, Ce, Mg, or at least two metals to form ternary phases, preferably Y-Al, Hf-Al, Zr-Al, Al- Mg, Al-Ce, so that the Cu content
• At .-% may be accomplished, for example, that in the manufacture of the gas diffusion electrode, game, form at ⁇ by melting and thermal oxidation, intermetallic phases that can be selectively reduced then, for example, electrochemically.
• a melt in the mixture takes place before the binder is added.
• the metal is first added and fused with copper before adding to the mixture of the binders and optionally further substances.
• the method according to the invention can be carried out by a calendering process, as shown schematically in FIG.
• the rolling or calendering is carried out at a rolling speed between 0.3 to 3 U / min, preferably 0.5-2 U / min.
• approximately ⁇ form is the flow rate or feed rate (the GDE in length per time, for example when calendering) Q in the range of 0.04 to 0.4 m / min, preferably 0.07 to
• Cu powder aggregates having a particle diameter of 50 to 600 ⁇ m, preferably 100 to 450 ⁇ m, more preferably 100 to 200 ⁇ m, in particular in the second mixture when applying several layers, can be added become.
• the particle diameter of these aggregates is 1 / 3-1 / 10 of the total layer thickness of the layer.
• the addition may also be an inert material such as a metal oxide. As a result, an improved formation of pores or channels can be achieved.
• an exemplary method for producing a gas diffusion electrode can proceed for example as follows: To prepare the GDE ayerkalandrierclar can be used in which a mixture of a kaltflie ⁇ Hzdem polymer (preferably PTFE) and the respective pre-calcined catalyst powder comprising Cu and optionally a Pro ⁇ moter, in an intensive mixing device or on a laboratory scale with a knife mill (IKA) is produced.
• the Mischproze- dur for example, follow the following procedure, but is not limited to: 30sec milling / mixing, 15 sec pause for 6 min, this indication is pulls ⁇ for example to the knife mill with 50g total loading be.
• the mixed powder reaches a slightly sticky consistency after the mixing process, in which case, for example, a fibrillation of the binder, for example PTFE, takes place.
• a fibrillation of the binder for example PTFE
• the mixing time may also vary until this state is reached.
• the powder mixture obtained is in connection to a Kup ⁇ fernetz with a mesh size of> 0.5 mm and ⁇ 1.0 mm and a wire diameter of 0.1-0.25 mm in a bulk thickness of 1 mm scattered or sieved.
• the applied Pul ⁇ -mixing is then subjected Pick ⁇ for example with a doctor blade. This process can be repeated several times until a uniform layer is obtained.
• the powder mixture can be granulated during or after the mixing operation to obtain a pourable material, for example with an agglomerate diameter of 0.05 to 0.2 mm. So that the powder does not trickle through the net, the back ⁇ side of the Cu mesh can be sealed with a film that is not limited.
• the prepared layer is compacted by means of a two-roller rolling device (calender). The rolling process itself is characterized in that a reservoir of material forms in front of the roll.
• Speed of the roller is between 0.5-2 rpm and the gap width has been increased to the height of the carrier + 40% to 50% of the
• Huft Too Hf of the powder set or corresponds to almost the thickness of the network + 0.1-0, 2mm delivery.
• the calender can also be heated. Preference is given to temperatures in the range from 20 to 200 ° C., preferably from 20 to 50 ° C.
• the catalyst itself can be processed before application in the calcined state, for example as a metal oxide precursor, or even in the reduced state. Mixtures of both forms are possible. This also applies to the case of the intermetallic phases or Legie- described stanchions so that they can be eisole also in the oxide form or metal ⁇ metallic state. Furthermore, it is not excluded the calendered electrode Nachhin ⁇ a calcine, for example for 5 to 15 minutes at 300- 360 ° C.
• the gas diffusion electrode according to the invention it is above ⁇ geous, especially in the case of kohlenwasserstoffselekti ⁇ ven copper catalyst electrodes, to make better contact nano-scale materials, while maintaining a high porosity, apply a copper-PTFE base layer as a second layer.
• the base layer can be characterized by a very high conductivity, for example 7 mOhm / cm or more, and preferably has a high porosity, for example of 50-70%, and a hydrophobic character.
• the binder content, for example PTFE may ⁇ example, between 3- 30 wt.%, For example 10-30 wt.%, Are selected.
• the copper intermediate layer as the second layer may be the first in the region of the overlap zone to the catalyst layer
• Layer itself catalytically active, and serves in particular for better surface electrical connection of the electrocatalyst and can improve the CO 2 - availability due to the high porosity.
• the corresponding electrocatalyst / binder (eg PTFE) mixture can be screened out in a first step on the back of the power distribution and calendered.
• the binder used, the ⁇ special PTFE should be treated in accordance with certain embodiments previously in a knife mill to achieve a Fa ⁇ formation of condensate.
• Suitable PTFE powders for example, Dyneon® TF 9205 and Dyneon® TF 1750 have proven particularly useful. To support this effect, abrasive
• Hard materials in the range between 0-50 wt.% are mixed.
• the following materials are suitable, for example: SiC, B 4 C, Al 2 O 3 (noble corundum), SiO 2 (glass breakage), preferably in a grain size of 50-150 ⁇ m.
• the preparation of the gas diffusion electrode with binder (eg PTFE) based diffusion barrier based on several layers that are not to be considered isolated from each other, but preferably in the Grenzberei ⁇ Chen as wide as possible overlap zone, for example 1-20 ym.
• the method of the two-layer structure also has the possibility to dispense within the catalyst layer as the first layer on binder materials, creating a better electrical conductivity can be achieved. It can also handle very ductile or brittle powder Parti ⁇ kel. This is not possible in a single-layered structure. In mechanically sensitive catalysts can be applied to the process step of the knife mill omitted who ⁇ , whereby the catalyst remains unchanged, as a me chanical stress ⁇ by the mixing process can be avoided.
• a subsequent electrochemical activation of the electrode may get ⁇ NEN accordance with certain embodiments, if necessary, be carried out, for example by chemical or electrochemical activation, and is not particularly be limited ⁇ .
• An electrochemical activation procedure can lead to cations of the electrolyte electrolyte (eg KHCO3, K2SO4 NaHC0 3 , KBr, NaBr) penetrating the hydrophobic GDE channels, creating hydrophilic regions. This effect is particularly advantageous and has not been described in the Li ⁇ erature.
• the present invention ⁇ an electrolytic cell comprising a gas diffusion electrode of the invention, which is preferably used as the cathode.
• the gas diffusion electrodes according to the invention can be operated especially in plate electrolyzers.
• the other components of the electrolysis cell such as the anode, possibly one or more membranes, supply line (s) and discharge (s), the voltage source, etc., and other op ⁇ tionale devices such as cooling or heating devices are not particularly limited according to the invention, as well as not anolyte and / or catholyte used in such an electrolytic cell, the electrolytic cell according to certain embodiments being used on the cathode side for the reduction of carbon dioxide.
• the configuration of the anode compartment and the cathode compartment is also not particularly limited.
• FIGS. 4 to 6 Exemplary embodiments for an exemplary construction of a typical electrolysis cell and of possible anode and cathode compartments are shown in FIGS. 4 to 6.
• An electrochemical reduction of, for example, CO 2 takes place in an electrolysis cell, which usually consists of an anode and a cathode compartment.
• an electrolysis cell which usually consists of an anode and a cathode compartment.
• an electrolysis cell usually consists of an anode and a cathode compartment.
• a gas diffusion electrode according to the invention can be used, for example as a cathode.
• the cathode compartment II is is madestal ⁇ tet in Figure 4, that a catholyte is fed from the bottom and then up leaving the cathode compartment II.
• the cathode compartment II is madestal ⁇ tet in Figure 4, that a catholyte is fed from the bottom and then up leaving the cathode compartment II.
• Katholyt but also supplied from above, such as in falling film electrodes.
• the anode A which is electrically connected to the cathode K by means of a current source for providing the voltage for the electrolysis, takes place in the anode compartment I, the oxidation of a substance, which is supplied from below, for example with an anolyte, and the anolyte with the product the oxidation then leaves the anode compartment.
• a reaction gas such as carbon dioxide can be promoted through the gas diffusion electrode into the cathode space II for reduction.
• the spaces I and II are separated by a membrane M.
• Figure 6 corresponds to a mixed form of the structure of Figure 4 and the structure of Figure 5, wherein an on ⁇ construction is provided with the gas diffusion electrode to catholyte, as shown in Fi gur 4, whereas on the anolyte side a structure as shown in FIG. 5 is provided.
• an on ⁇ construction is provided with the gas diffusion electrode to catholyte, as shown in Fi gur 4
• a structure as shown in FIG. 5 is provided.
• the cathode-side electrolyte and the anode-side electrolyte can thus be identical, and the electrolysis ⁇ cell / electrolysis unit can do without membrane.
• the electrolytic cell in such embodiments has a membrane, but this is associated with additional expense in terms of the membrane as well as the applied voltage.
• Catholyte and anolyte can also optionally be mixed again outside the electrolysis cell.
• Figures 4 to 6 are schematic representations.
• the electro ⁇ lysezellen of Figures 4 to 6 can also be assembled into mixed variants.
• the Ano ⁇ denraum can be designed as a PEM half-cell, as in Figure 5, while the cathode compartment consists of a half-cell, which includes a certain volume of electrolyte between the membrane and electrode, as shown in Figure 4.
• the distance between the electrode and the membrane is very small or 0 if the membrane is made porous and contains a supply of the electrolyte.
• the membrane may also be made multilayered, so that separate Zumoni ⁇ approximations of anolyte or catholyte is made possible.
• the membrane may be an ion-conducting membrane, or a separator which causes only a mechanical separation and is permeable to cations and anions.
• the gas diffusion electrode of the invention it is possible to use a three-phase electrodeberichtbau ⁇ en.
• a gas from the rear to the electric active front of the electrode are performed there to perform an electro-chemical reaction.
• the gas diffusion electrode can also be behind only flows, that is, a gas such as CO2 is guided past the rear side of the gas diffusion electrode in relation to the electrolyzer ⁇ th, the gas can then pass through the pores of the gas diffusion electrode and the product can be discharged back , Preference is given to the gas flow during
• a cell variant (a) allows a direct active flow through the GDE with a gas such as CO2.
• the resulting products are removed from the electrolysis cell through the catholyte outlet and separated from the liquid electrolyte in a subsequent phase separator.
• Disadvantage of this method is the increased mechanical loading of the GDE ⁇ African as well as a partially or completely pushed out of the electrolyte from the pores.
• the second cell variant describes a mode of operation in which the CO2 flows in the rear area of the GDE through an adapted gas pressure.
• the gas pressure should be so selected ⁇ , the that it is equal to the hydrostatic pressure of the electrolyte in the cell, so that no electrolyte is suppressed carried.
• An essential advantage of the cell variant is a higher conversion of the reaction gas used, for example CO2, in contrast to the flow-through variant.
• a film can be deposited on the side remote from the electric ⁇ LYTEN side of the gas diffusion electrode, that is on the carrier, for example a net, to prevent the electrolyte on conversion to gas.
• the film may be suitable here provided and is playing at ⁇ hydrophobic.
• the electrolytic cell on a diaphragm which separates the cathode chamber and the anode chamber of the electrolytic cell to prevent a mixing of the electric ⁇ LYTEN.
• the membrane is not particularly limited here, as long as it separates the cathode space and the anode space. In particular, it essentially prevents a transfer of the gases produced at the cathode and / or anode to the anode or cathode space.
• a preferred membrane is an ion exchange membrane, for example polymer based.
• a preferred material of an ion exchange membrane is a sulfonic fonATORs tetrafluoroethylene polymer, such as Nafion ®, Example ⁇ as Nafion ® 115.
• anode In addition to polymeric membranes can be used, for example those mentioned in EP 1685892 Al and / or loaded with zirconium oxide polymers, such as polysulfones, ceramic membranes , Likewise, the material of the anode is not particularly limited and depends primarily on the desired reaction. Exemplary anode materials include platinum or platinum alloys, palladium or palladium alloys, and glassy carbon. Further anode materials are also conductive oxides such as doped or undoped TiO 2 , indium tin oxide (ITO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), iridium oxide, etc. these catalytic acti ⁇ ven compounds may be deposited on the surface even in thin-film technology, for example on a titanium carrier.
• ITO indium tin oxide
• FTO fluorine-doped tin oxide
• AZO aluminum-doped zinc oxide
• iridium oxide etc.
• the electrolysis cells from FIGS. 4 to 6 can also be combined to form mixed variants.
• the anode space can act as a proton exchange membrane (proton exchange membrane).
• PEM proton exchange membrane
• Ka ⁇ Thode space consists of a half-cell containing a certain volume of electrolyte between the membrane and electrode GE membrane.
• the distance between the electrode and the membrane is very small or 0, if the membrane is porous and contains a supply of the electrolyte.
• the membrane may also be made multilayered, so that separate Zumoni ⁇ approximations of anolyte or catholyte is made possible. Separation effects are achieved in aqueous electrolytes, for example by the hydrophobicity of intermediate layers. Nevertheless, conductivity can be ensured if conductive groups are integrated in such separation layers.
• the membrane may be an ion-conducting membrane, or a separator which causes only a mechanical separation.
• reaction gas for example CO 2
• different gas distribution chambers may be provided, of which two are exemplified in Figures 7 and 8. These can be provided in order to further increase the residence time of a reaction gas such as CO 2 and the associated conversion.
• the gas distributor may, in particular at a behind flocked gas diffusion electrode ⁇ contribute to enhanced mass transfer over the entire electrode surface.
• FIG. 1 Further aspects of the present invention relate to an electrolysis plant comprising an electrode according to the invention or an electrolysis cell according to the invention, and the use of the gas diffusion electrode according to the invention in an electrolysis cell or an electrolysis plant.
• the other components of the electrolysis system are not limited and can be suitably provided.
• Comparative Example 1 a multilayer Gasdiffusi ⁇ onselektrode by the procedure of R. Cook (J. Electrochem. Soc., 1990, 137, 2) was prepared.
• the preparation of the hydrophobic gas transport layer was carried out according to publication: 2.5 g of volcano XC 72 and 2.8 g of Teflon 30B (Dupont) were dispersed in 25 ml of water and applied to a dense copper mesh (100 mesh). The coated layer was dried in air and pressed at 344 bar for 2 min. With the- This procedure produced a total of three layers. Since ⁇ after the pressing of three further katalysatorbe ⁇ content layers with the following mixing ratio was made:
• the catholyte was an IM KHC0 3 solution with KHCO 3 in an IM concentration and the anolyte was IM KHCO 3 , each in deionized water (18 ⁇ ), each in an amount of 100 mL, and the temperature was 25
• 0.5MK 2 S0 4 was also tried as the catholyte and 2.5M KOH as the anolyte.
• the substrate used in Comparative Example 3.1 was a commercially available carbon cloth for gas diffusion electrodes (Elat® LT1400W, NuVant) in the form of a microporous layer.
• a Nafion® D521 dispersion was applied as an electrocatalyst, which was prepared as follows. 0.87 g Cu (OAc) 2 * H 2 0 were dissolved in about 1 ml of H 2 O. Further, 1.36 g of Vulcan XC 72 was mixed with 15 ml of ethylene glycol, and the dissolved Cu (OAc) 2 was added and dispersed for 1 hour. Subsequently, 1.5 g of the Nafion® D521 suspension were added and stirred with the glass rod. Following the Mi ⁇ research was applied to the hydrophobic gas diffusion layer, in air and then dried in a drying oven for 2 hours at 120 ° C. The mixture was then calcined in the oven at 250 ° C with a slope of 10K / min in an atmosphere of
• the electrode obtained in this way was subsequently characterized in terms of its electrochemical properties with a test setup which, with the exception of the GDE, corresponded to that of Comparative Example 1.
• Comparative Example 3.1 the results shown in Table 3 were achieved by varying the support (Cu mesh with a mesh size of 0.25 and a wire diameter of 0.14 mm) and the applied mixture.
• PTFE was also used instead of Nafion®.
• Table 3 Quantities and results in comparison examples 3.2 - 3.5 Backing binder precursor Nafion® amount Kata ⁇ Kataly ⁇ Max. FE carbon [wt.%] Of Kata ⁇ lyst sator C 2 H 4 [%] [wt.%] Lysators [mg / cm 2] [wt. %]
• a multi-layer gas diffusion electrode was prepared as described in United ⁇ equal to 3.1, for example, with a Cu / Zr02 catalyst was used as catalyst, which was obtained from CusZr. 3
• the GDE was also reduced prior to measurement
• 4.3 refers to an electrochemically activated electrode
• 4.4 refers to a hydrogen activated electrode.
• Table 4 the results are also shown in Figures 10 and 11. In Fig. 10, a current series is shown, and in Fig. 11 a measurement at constant current.
• coal-based GDE in Comparative Examples 1 to 4 showed increased Faraday efficiencies for hydrogen. It was concluded that carbon in the form of carbon blacks or activated carbon is less suitable for the production of ethylene-selective gas diffusion electrodes.
• the material used was the following:
• PTFE suspension TF5035R, 58 wt. % (Dyneon TM),
• Triton-100 (Fluka Chemie AG)
• Thickener hydroxyethylmethylcellulose (WalocelMKX 70000 PP 01, Wolff Cellulosics GmbH & Co. KG).
• the GDEs contain considerable amounts of the surfactant used, which was identified as the catalyst poison in a control experiment.
• the entspre ⁇ sponding catalyst poison Triton X 100 ((p-tert-octylphenoxy) polyethoxyethanol) could not be driven off without leaving a residue at temperatures> 340 ° C also, could be confirmed as tronenmikroskopisch rasterelek-.
• a corresponding Hydrotalcitprekursor the composition Cuo, ⁇ o, 4 (OH) 2] (CO3) 0.4 * mH 2 0 (unknown water content for the freshly precipitated hydrotalcite) is made by co-precipitation ⁇ .
• a catalyst powder is prepared by co-precipitating Cu (NO 3 ) 2 * 3H 2 O and ZrO (NO 3 ) 2 * XH 2 O according to Reference Example 1 with the respective molar amounts (mol).
• the mixing procedure follows the following procedure: 30 seconds grinding / mixing and 15 seconds rest for a total of 6 minutes.
• This information refers to the knife mill with 50g total load.
• the mixed powder he ⁇ reaches after mixing a slightly sticky consistency. Depending on the amount of powder or selected polymer or chain length, the mixing time may also vary until this state is reached.
• the resulting powder mixture is then spread or screened onto a copper mesh with a mesh size of> 0.5 mm and ⁇ 1.0 mm and a wire diameter of 0.1-0.25 mm in a bulk thickness of 1 mm.
• the back ⁇ side of the Cu mesh can be sealed with a film, the not further limited.
• the prepared layer is compacted by means of a two-roller rolling device (calender).
• the rolling process itself is characterized in that a reservoir of material forms in front of the roll.
• the speed of rotation of the roller is between 0.5-2 rpm and the gap width was at the level of the carrier + 40% to 50% of the
• Huftiere Hf of the powder set or corresponds to almost the thickness of the network + 0.1-0, 2mm delivery.
• the gas diffusion electrode obtained is activated 3 solution for 6 hours at a current density of 15mA / cm 2 in an electrolyzer in a ⁇ sebad IN KHCO.
• Dendritic Cu powder (45 g, particle size ⁇ 45 ym, determined by sieving with corresponding mesh size (45ym)) is mixed with 5 g PTFE in an IKA knife mill according to the procedure described inaddbei ⁇ game 6 and processed under the same conditions to a GDE.
• the described GDE provided a Faraday efficiency of
• the prepared oxide precursor is ground for 3 min in a planetary ball mill (powder set) before being used and subsequently sieved (particle size
• Copper powder with a particle diameter of 100-200 ym and PTFE TF 1750 Dyneon were mixed for 6 minutes in an IKA A10 knife mill (15 seconds grinding, 30 seconds rest).
• the powder layer was then screened over a 0.5 mm thick template and straightened to form a basecoat. This was followed by extrusion with a 2-roll calender with a roll spacing of 0.5 mm.
• the result was a highly porous base layer with a porosity> 70%, good mechanical stability and very good conductivity with 5 mOhm / cm. It could be used catalysts with 40 wt.% Cu content. Preferably, the catalysts have a purity which is above the commercially available materials or quality standards, as in the example. This could be detected by (surface-sensitive) XPS. Also, REM / EDX mapping analyzes also indicated no contamination of the hydrophobic base layer.
• Electrolysis cell which usually consists of an Ano ⁇ den- and a cathode compartment.
• FIGS. 4 to 6 show examples of a possible cell arrangement. For each of these cell arrangements, the idea presented below is applicable.
• the electrolysis cells from FIGS. 4 to 6 can also be combined to form mixed variants.
• the anode compartment can be used as proton exchange membrane (proton exchan- GE membrane, PEM) half cell to be executed while the Ka ⁇ Thode space consists of a half-cell containing a certain volume of electrolyte between the membrane and electrode.
• the distance between the electrode and the membrane is very small or 0, if the membrane is porous and contains a supply of the electrolyte.
• the membrane may also be made multilayered, so that separate Zumoni ⁇ approximations of anolyte or catholyte is made possible. Separation effects are achieved in aqueous electrolytes, for example by the hydrophobicity of intermediate layers. Nevertheless, conductivity can be ensured if conductive groups are integrated in such separation layers.
• the membrane may be an ion-conducting membrane, or a separator which causes only a mechanical separation.
• the present invention provides the possibility of selective ethylene, dimensionally stable gas diffusion electrode to Katalysa ⁇ torpulverbasis manufacture.
• This technique represents the basis for the production of electrodes on a larger scale, which can achieve current densities> 170mA / cm 2 depending on the mode of operation.
• All previously known methods for producing ethylene-selective Cu electrodes are not suitable for scale-up or are not dimensionally stable.
• the preparation of the gas diffusion electrode according to the invention is based on the exclusion of conductive fillers based on carbon blacks or carbon blacks.
• a coal substitute here serves the catalyst itself or dendritic copper or mixtures of both.
• the method according to the invention is in accordance with certain exporting ⁇ approximately forms without surface active agents / surfactants or
• Thickeners and additives (such as flow improvers), which were identified as catalyst poisons.

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• 2015
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