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
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/042—Electrodes formed of a single material
  • C25B11/043—Carbon, e.g. diamond or graphene
  • C25B11/044—Impregnation of carbon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/14—Alkali metal compounds
  • C25B1/16—Hydroxides
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B1/00—Electrolytic production of inorganic compounds or non-metals
  • C25B1/01—Products
  • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
  • C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
• • 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
  • C25B15/00—Operating or servicing cells
• • 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
  • C25B15/00—Operating or servicing cells
  • C25B15/02—Process control or regulation
• • 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
  • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
  • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
  • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/18—Carbon
  • B01J21/185—Carbon nanotubes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M12/00—Hybrid cells; Manufacture thereof
  • H01M12/04—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type
  • H01M12/06—Hybrid cells; Manufacture thereof composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type with one metallic and one gaseous electrode
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

• the present invention relates to an electrochemical process for the reduction of molecular oxygen in alkaline solutions in the presence of nitrogen-doped carbon nanotubes, in which no hydrogen peroxide is produced as a by-product of the reduction.
• the desired reduction products of molecular oxygen in such electrochemical reduction reactions are usually doubly negatively charged oxygen ions, which are usually in the form of hydroxide ions in aqueous solutions.
• the electrochemical reduction of molecular oxygen can also result in another reduction product which can be formed in smaller or larger amounts depending on the conditions of the reduction process and depending on the electrode material.
• This other reduction product is hydrogen peroxide.
• Hydrogen peroxide Due to the autoprotolysis of water, hydrogen peroxide would automatically be present in aqueous solutions in addition to the abovementioned hydrogen peroxide anion. Hydrogen peroxide is generally an undesirable by-product in the reduction of molecular oxygen due to its corrosive and oxidative properties.
• the disclosed process is disadvantageous in that it does not allow transferability of the process to technically relevant processes, such as the sodium chloride electrolysis process, in which the electrochemical reduction of molecular oxygen is of great importance and which generally in alkaline media and, second, that it can not prevent formation of hydrogen peroxide, thereby reducing the yield of double negatively charged oxygen ions, such as hydroxide ions, by the reaction of formula (IV).
• technically relevant processes such as the sodium chloride electrolysis process, in which the electrochemical reduction of molecular oxygen is of great importance and which generally in alkaline media and, second, that it can not prevent formation of hydrogen peroxide, thereby reducing the yield of double negatively charged oxygen ions, such as hydroxide ions, by the reaction of formula (IV).
• the aforementioned doubly negatively charged oxygen ions in connection with the present invention also refer to doubly negatively charged oxygen ions, which may be bound to hydrogen ions in the abovementioned solutions having a pH greater than or equal to 8. Such compounds are about hydroxide anions (OH " ) or water (H 2 O). In the following, as well as above, reference is made to various anions of oxygen.
• the aforementioned doubly negatively charged oxygen ions (anions) can, as described above, also be bound to hydrogen ions, without this impairing the mode of action of the present invention.
• the process according to the invention makes it possible for the first time to carry out a reduction of the molecular oxygen present in solution of a pH greater than or equal to 8 molecularly dissolved directly to double-negative-charged oxygen ions.
• the nitrogen-doped carbon nanotubes used in the process according to the invention usually have a diameter of from 3 to 150 nm, preferably from 4 to 100 nm and particularly preferably from 5 to 50 nm.
• the nitrogen-doped carbon nanotubes used in the process according to the invention usually have a ratio of length to diameter (aspect ratio) of at least 2, preferably at least 5, particularly preferably at least 10.
• the preferred and preferred diameter and aspect ratios of the nitrogen-doped carbon nanotubes are advantageous because high aspect ratios coupled with the In particular, the outer surfaces of the nitrogen-doped carbon nanotubes are particularly suitable for the aforementioned transfer of four electrons according to the formula (III).
• the nitrogen-doped carbon nanotubes contain pyridine and quaternary nitrogen in a ratio greater than or equal to 1, preferably greater than or equal to 1.5, particularly preferably greater than or equal to 2.
• the nitrogen-doped carbon nanotubes for this purpose contain a proportion of greater than 1 atom% of nitrogen.
• the electrode is absorbed / released in the electrolyte (c [- -]), depending on the m
• the limiting current i Diff is determined at different rotational speeds ⁇ of the annular disk electrode, and then this limiting current i Diff is determined
• the slope of the Koutecky-Levich diagram thus obtained is, in a linearized manner, the constant factor K, which can be read off.
• the nitrogen-doped carbon nanotubes used according to the method of the invention and its preferred embodiments can be prepared according to the methods of the prior art if the aforementioned properties of the nitrogen-doped carbon nanotubes are obtained therefrom.
• the nitrogen-doped carbon nanotubes are obtained from the processes according to German patent application with the application number DE 10 2007 062 421.4.
• suitable catalysts for the preparation of nitrogen-doped carbon nanotubes are also disclosed in WO 2007 093 337.
• the nitrogen-doped carbon nanotubes are obtained from the processes according to the German patent application with the application number DE 10 2007 062 421.4, in which the temperature for producing the nitrogen-doped carbon nanotubes is about 650 0 C and in which the starting material comprising carbon and nitrogen is pyridine.
• the liberating can be done by washing the nitrogen-doped carbon nanotubes with an acid.
• the acid is hydrochloric acid.
• the freeing of the nitrogen-doped carbon nanotubes from the catalyst material is particularly advantageous, because in this way the residues of catalyst material are no longer available as possible, catalytically active components for a possible reduction of molecular oxygen to hydrogen peroxide according to the formula (E).
• the nitrogen-doped carbon nanotubes are free of metal or semimetal components, such as Fe, Ni, Cu, W, V, Cr, Sn, Co, Mn and Mo.
• the inventive method is usually when applying a voltage of +0.2 to -0.8 V between a silver / silver chloride reference electrode (Ag / AgCl reference electrode) and an electrode comprising the aforementioned nitrogen-doped carbon nanotubes with a proportion of pyridinic and quaternary nitrogen, wherein the reduction of the molecular oxygen according to the method according to the invention takes place at the surface of the electrode comprising the nitrogen-doped carbon nanotubes with a content of pyridinic and quaternary nitrogen.
• the voltage specified here is based on an Ag / AgCl reference electrode, as the person skilled in the art generally knows.
• the inventive method is characterized by a reduced electrical power consumption with otherwise the same yield of double negatively charged oxygen ions, which is due, inter alia, that the transmission of the aforementioned four electrons according to the method presented here at lower Stress already takes place, as would be the case in prior art methods, such as using Leitruß. This means that the overvoltages on the electrode surface observed in the method according to the invention, which can be observed, are pleasingly low.
• the current densities are essentially in accordance with the above-mentioned voltage or after the aforementioned diffusion rate under application of the aforementioned voltage and are in the process according to the invention or in methods according to preferred variants advantageously high at low voltages, since in a step four electrons are already transferred at low voltages.
• the nitrogen-doped carbon nanotubes used according to the invention with a content of pyridinic and quaternary nitrogen in solutions of a pH greater than 8 allow such minimization of the energy used by reducing the minimum voltage required for the reduction (the cell voltage).
• Another object of the present invention is the use of nitrogen-doped carbon nanotubes with a proportion of py ⁇ dinischem and quaternary nitrogen for the reduction of molecular oxygen in aqueous solutions of a pH greater than 8.
• a final object of the present invention is an electrolysis device for the electrochemical reduction of molecular oxygen to double negatively charged oxygen
• Ions characterized in that they have a first electrode space (1) filled with a
• the method according to the invention can be carried out particularly advantageously.
• the measuring points shown relate to the rotational speeds of the annular disk electrode of 400 min -1 over 900 mm -1 to 1600 mm 1 .
• the illustrated line is a linear approximation for determining the factor K according to the formula (VI) obtained at 20.7
• FIG. 2 shows a comparison of the measurement data recorded by means of an annular disk electrode against an Ag / AgCl reference electrode at a rotation speed of 3600 mm.sup.- 1 of the annular disk electrode in the case of the noninventive method according to Comparative Example 1 (line B) and in the case of the inventive method according to the example 1 (line A).
• FIG. 3 shows a Koutecky-Levich diagram obtained from the measured data of the method according to the invention according to example 2.
• the limiting current I D ⁇ is shown in microamps above the root
• Approximation for determining the factor K according to the formula (VI) obtained at 17.4. 4 shows a Koutecky-Levich diagram obtained from the measured data of the inventive method according to example 3. The limiting current i mff in microamps is shown above the root j 1 of the rotational speed ⁇ 2 of the annular disc electrode in V min -1
• Measuring points refer to the rotational speeds of the annular disc electrode of 400 min -1 over 900 min -1 and 1600 min -1 to 2500 min -1 .
• the illustrated line is a linear approximation for determining the factor K according to the formula (VI) obtained at 20.1.
• FIG. 5 shows a Koutecky-Levich diagram with all measured data from the methods according to the invention according to Examples 1 to 3, as well as from the non-inventive method according to Comparative Examples 2 and 3.
• the data from the inventive method according to Example 1 are as filled circles whose linear approximation for determining the factor K according to the formula (VI) is shown as a thick solid line.
• the data from the inventive method according to Example 2 are shown as filled squares whose linear approximation for determining the factor K according to the formula (VT) as a thin solid line.
• the data from the inventive method according to Example 3 are shown as filled triangles whose linear approximation for determining the factor K according to the formula (VI) as a shaded solid line.
• the respective linear approximations of the methods according to the invention according to Examples 1 to 3 are additionally characterized by the numbers 1 to 3.
• the data from the non-inventive method according to Comparative Example 2 are shown as empty squares whose linear approximation for determining the factor K according to the formula (VI) as a thin dashed line.
• the data from the non-inventive method according to Comparative Example 3 are shown as empty circles whose linear approximation for determining the factor K according to the formula (VI) as a thick dashed line.
• FIG. 6 shows a device according to the invention with a first electrode (Ia) comprising a surface layer (Ia ') with nitrogen-doped carbon nanotubes with a content of pyridinic and quaternary nitrogen in a first electrode space (1) containing a 0.2 M
• NaOH solution is filled with a pH of 13.31.
• a membrane (4) Separated from this by a membrane (4) is another electrode space (2) with a titanium electrode (2a), wherein the
• Electrode space (2) is filled with a 0.5 wt .-% sodium chloride solution and wherein the titanium electrode (2a) to the first electrode (Ia) is electrically connected via a voltage source (3).
• the nitrogen-doped carbon nanotubes were previously examined by means of electron spectroscopy for chemical analysis (ESCA, ThermoFisher, ESCALab 22OiXL, method according to the manufacturer) and by means of transmission electron microscopy (TEM, FEI device type: Tecnai20, Megaview DI, method according to the manufacturer) ,
• the nitrogen-doped carbon nanotubes had a content of 6.5 atom% of nitrogen, that they had a ratio of pyridine to quaternary nitrogen of 2.88, that they have a mean diameter d 50 of about 10 nm and have a minimum length of about 150 nm, so that they had an aspect ratio of greater than 10.
• the rotating annular disk electrode now comprising the nitrogen-doped carbon nanotubes, was then used as a working electrode in a laboratory cell containing 3 electrodes (working electrode, counter electrode and reference electrode).
• the structure used is generally known to the person skilled in the art as a three-electrode arrangement.
• a 1 molar NaOH solution in water was used, which was previously saturated with oxygen by passing a stream of pure oxygen gas through it.
• the reference electrode used was a commercially available Ag / AgCl electrode (Mettler-Toledo).
• the electrolyte was heated to 60 0 C.
• the reduction of molecular oxygen dissolved in the electrolyte was also carried out at this temperature, which was controlled.
• a single measurement obtained from the above-mentioned Koutecky-Levich diagrams are shown in Fig. 2 for a measurement at 3600 revolutions of the annular disk electrode per minute (A) compared to the corresponding measurement from Comparative Example 1 (B).
• Example 2 An experiment similar to that in Example 1 was carried out, with the only difference that, instead of the nitrogen-doped carbon nanotubes used there, nitrogen-doped carbon nanotubes prepared by catalytic decomposition of pyridine at 650 ° C. in a fixed bed reactor on a catalyst corresponding to Example 1 WO 2007 093 337, were used. Measurements were also carried out at a rotational speed of the annular disc electrode of 2500 revolutions per minute.
• the nitrogen-doped carbon nanotubes were previously investigated by ESCA. It was found that the nitrogen-doped carbon nanotubes had a proportion of 3.8 atom% of nitrogen, and that they had a ratio of pyridine to quaternary nitrogen of 2.79.
• Example 3 Still further oxygen reduction according to the invention
• Example 2 An experiment similar to that in Example 2 was carried out, with the only difference that instead of the nitrogen-doped carbon nanotubes used there, nitrogen-doped carbon nanotubes, prepared by catalytic decomposition of pyridine at 650 0 C in a fixed bed reactor, on a catalyst according to Example 2 of WO 2007 093 337 were used.
• the nitrogen-doped carbon nanotubes were previously investigated by ESCA. It was found that the nitrogen-doped carbon nanotubes had a content of 5.8 atom% of nitrogen and that they had a ratio of pyridine to quaternary nitrogen of 1.61.
• Example 2 An experiment similar to that in Example 1 was carried out with the only difference that carbon black (Vulcan XC72, Cabot Co.) was used instead of the nitrogen-doped carbon nanotubes used there.
• carbon black Vulcan XC72, Cabot Co.
• Example 2 An experiment similar to that in Example 1 was carried out, with the only difference that instead of the nitrogen-doped carbon nanotubes used there, nitrogen-doped carbon nanotubes were now used, which according to ESCA had a pyridine to quaternary nitrogen ratio of 0.63.
• These nitrogen-doped carbon nanotubes were prepared by catalytic decomposition of pyridine at 750 ° C. in a fixed bed reactor, on a catalyst corresponding to Example 2 of WO 2007 093 337.

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• 2008
  • 2008-12-18 DE DE102008063727A patent/DE102008063727A1/de not_active Withdrawn
• 2009
  • 2009-12-05 WO PCT/EP2009/008699 patent/WO2010069490A1/de not_active Ceased
  • 2009-12-05 CN CN200980150665.8A patent/CN102257182B/zh not_active Expired - Fee Related
  • 2009-12-05 JP JP2011541157A patent/JP5607064B2/ja not_active Expired - Fee Related
  • 2009-12-05 EP EP09764740.8A patent/EP2379782B1/de not_active Not-in-force
  • 2009-12-05 SG SG2011041928A patent/SG172041A1/en unknown
  • 2009-12-05 US US13/131,166 patent/US20110233071A1/en not_active Abandoned
• 2016
  • 2016-11-18 US US15/355,855 patent/US20170107634A1/en not_active Abandoned

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