Electrolyzer and method for splitting water

Patent metadata

Field	Value
Publication number	US-2021054511-A1
Application number	US-202016947737-A
Country	US
Kind code	A1
Filing date	Aug 14, 2020
Priority date	Aug 20, 2019
Publication date	Feb 25, 2021
Grant date	—

Abstract

An electrolyzer for splitting molecular water into molecular hydrogen and molecular oxygen using electrical energy comprises an anodic half-cell with an anode and a cathodic half-cell with a cathode. The anodic half-cell and the cathodic half-cell are separated from each other by a separator. The anodic half-cell comprises an anodic electrolyte, which is in contact with the anode. The cathodic half-cell comprises a cathodic electrolyte, which is in contact with the cathode. The anodic half-cell comprises an anodic catalyst. The cathodic half-cell contains at least one cation complex for forming at least one mediator complex. The at least one cation complex is reducible to the mediator complex by taking up at least one electron at the cathode. The mediator complex is a catalytically active chemical complex for splitting the molecular water (H2O) into molecular hydrogen (H2) and hydroxide ions (OH−) while releasing at least one electron.

First claim

What is claimed is:

1 . An electrolyzer for splitting molecular water into molecular hydrogen and molecular oxygen using electrical energy, which electrolyzer comprises an anodic half-cell with an anode and a cathodic half-cell with a cathode, wherein the anodic half-cell and the cathodic half-cell are separated from each other by a separator, wherein the anodic half-cell comprises an anodic electrolyte, which is in contact with the anode, and wherein the cathodic half-cell comprises a cathodic electrolyte, which is in contact with the cathode, wherein the anodic half-cell comprises an anodic catalyst, wherein the cathodic half-cell comprises at least one cation complex for forming at least one mediator complex, wherein the at least one cation complex is reducible to the mediator complex by taking up at least one electron at the cathode, and wherein the mediator complex is a catalytically active chemical complex for splitting the molecular water (H 2 O) into molecular hydrogen (H 2 ) and hydroxide ions (OH − ) while releasing at least one electron.

2 . The electrolyzer in accordance with claim 1 , wherein the at least one cation complex is a catalytically inactive or substantially inactive chemical complex.

3 . The electrolyzer in accordance with claim 1 , wherein the cation complex and the mediator complex are dissolved in the cathodic electrolyte.

4 . The electrolyzer in accordance with claim 1 , wherein the at least one cation complex is formed by at least one first central particle and at least one first ligand, which surrounds the at least one first central particle, wherein the mediator complex is formed by at least one second central particle and at least one second ligand, which surrounds the at least one second central particle, wherein the at least one first central particle and the at least one second central particle form a redox pair in such a way, wherein the first central particle is reducible to the second central particle by taking up at least one electron, and wherein the at least one second central particle is oxidizable to the first central particle by releasing at least one electron.

5 . The electrolyzer in accordance with claim 4 , further comprising at least one of the following features:
a) The at least one first central particle is a cation reducible by at least one oxidation state and the at least one second central particle is the cation reduced by the at least one oxidation state, wherein in particular the reducible cation and the reduced cation are ions of different oxidation states of the same metal,
wherein further in particular the metal is a metal from the group of transition metals, in particular from the group of lanthanides, wherein further in particular at least one of the following features is provided:
a1) The transition metal is ruthenium (Ru), chromium (Cr), vanadium (V), manganese (Mn), rhodium (Rh), cobalt (Co), or iron (Fe)
and
a2) the lanthanide is europium (Eu) or cerium (Ce),
and b) the cation complex is formed by one single first central particle and/or the mediator complex is formed by one single second central particle,
wherein in particular the single first central particle of the cation complex is surrounded by at least three first ligands and/or wherein the mediator complex is surrounded by at least three second ligands.

6 . The electrolyzer in accordance with claim 4 , further comprising at least one of the following features:
a) The at least one first ligand and the at least one second ligand are identical and b) the at least one first ligand and/or the at least one second ligand are configured in the form of a complexing agent,
wherein in particular the complexing agent is configured in the form of a complexing molecule,
and c) the at least one first ligand and/or the at least one second ligand is or contains mercaptoacetic acid, 2-mercaptopropionic acid, cysteamine, cysteine, cysteinmethylester, or catechol and d) the at least one first central particle is introduced into the cathodic electrolyte by dissolving a salt, which contains the at least one first central particle and e) the at least one first ligand and/or the at least one second ligand is introduced into the cathodic electrolyte by dissolving.

7 . The electrolyzer in accordance with claim 1 , further comprising at least one of the following features:
a) The separator is configured in the form of an anion exchange membrane,
wherein in particular the anion exchange membrane is configured to be permeable to hydroxide ions,
and b) the cathodic electrolyte is water or an aqueous solution and/or the anodic electrolyte is water or an aqueous solution and c) the anodic electrolyte has a pH value of at least about 7, in particular at least about 9, and d) the cathodic electrolyte has a pH value in a range from 0 to about 9 and e) a pH value of the anodic electrolyte and a pH value of the cathodic electrolyte are different and define a pH gradient,
wherein in particular the pH gradient is at least 1, in particular at least 3, further particularly at least 5.

8 . The electrolyzer in accordance with claim 1 , further comprising at least one of the following features:
a) The cathodic half-cell contains a pH value regulator,
wherein in particular the pH value regulator is or contains hydrochloric acid (HCl), sulfuric acid (H 2 SO 4 ), acetic acid, phosphoric acid, and/or a phosphoric acid buffer,
and b) the anode consists of the anodic catalyst or is made of the anodic catalyst or contains the anodic catalyst or is coated with the anodic catalyst or is electrically conductively in contact with the anodic catalyst
or
the separator is coated with the anodic catalyst or is electrically conductively in contact with the anodic catalyst.

9 . The electrolyzer in accordance with claim 1 , further comprising at least one of the following features:
a) The anode is of solid or reticular configuration and b) the anodic catalyst is nickel, iridium, or cobalt, or contains nickel, iridium, and/or cobalt, in particular in the form of NiO x , NiCeO x , NiCoO x , NiCuO x , NiFeO x , NiLaO x , IrO x , CoFeO x or CoO x , and c) the cathode is made of carbon or stainless steel.

10 . A method for splitting molecular water into molecular hydrogen and molecular oxygen using electrical energy, in which method hydroxide ions are oxidized in an anodic half-cell with an anode with the involvement of an anodic catalyst, wherein the anodic half-cell is separated from a cathodic half-cell with a cathode by a separator, wherein the anodic half-cell comprises an anodic electrolyte, which is in contact with the anode, and wherein the cathodic half-cell comprises a cathodic electrolyte, which is in contact with the cathode, wherein the molecular water (H 2 O) in the cathodic half-cell is split into molecular hydrogen (H 2 ) and hydroxide ions (OH − ) with the involvement of at least one mediator complex, wherein in the cathodic half-cell the at least one mediator complex is formed from at least one cation complex, wherein the mediator complex is a catalytically active chemical complex for splitting the molecular water (H 2 O) into molecular hydrogen (H 2 ) and hydroxide ions (OH − ) while releasing at least one electron, and wherein the at least one cation complex is reduced to the mediator complex by taking up at least one electron at the cathode.

11 . The method in accordance with claim 10 , wherein a catalytically inactive or substantially inactive chemical complex is used as the at least one cation complex.

12 . The method in accordance with claim 10 , wherein the cation complex and the mediator complex are dissolved in th

Assignees

• Deutsch Zentr Luft & Raumfahrt

Inventors

• Hosseiny Seyed Schwan
• Mitzel Jens
• Rodriguez Aldo Saul Gago

Classifications

• C25B11/044

  Impregnation of carbon · CPC title

• C25B9/73

  of the filter-press type · CPC title

• C25B9/23

  comprising ion-exchange membranes in or on which electrode material is embedded · CPC title

• C25B1/04 Primary

  by electrolysis of water · CPC title

• C25B15/02

  Process control or regulation · CPC title