Charge transfer mediator based systems for electrocatalytic oxygen reduction

Patent metadata

Field	Value
Publication number	US-9812727-B2
Application number	US-201715617181-A
Country	US
Kind code	B2
Filing date	Jun 8, 2017
Priority date	Mar 14, 2014
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

Disclosed are systems for the electrocatalytic reduction of oxygen, having redox mediator/redox catalyst pairs and an electrolyte solution in contact with an electrode. The redox mediator is included in the electrolyte solution, and the redox catalyst may be included in the electrolyte solution, or alternatively, may be in contact with the electrolyte solution. In one form a cobalt redox catalyst is used with a quinone redox mediator. In another form a nitrogen oxide redox catalyst is used with a nitroxyl type redox mediator. The systems can be used in electrochemical cells wherein neither the anode nor the cathode comprise an expensive metal such as platinum.

First claim

We claim:

1. A fuel cell or electrosynthetic cell comprising:
(a) an anode half-cell containing an anode electrode, wherein in operation a fuel or precursor chemical is oxidized;
(b) a cathode half-cell comprising:
(i) an electrolyte solution comprising a redox mediator that is capable of transferring or accepting electrons and protons while undergoing reduction or oxidation;
(ii) a cathode electrode in contact with the electrolyte solution, where in operation the redox mediator is reduced; and
(iii) a heterogeneous redox catalyst in contact with the electrolyte solution, where in operation the redox mediator is oxidized, wherein the heterogeneous redox catalyst is not in direct contact with the cathode electrode;

(c) an inlet to facilitate the flow of O 2 or air comprising O 2 into the cathode half-cell, where in operation the O 2 is reduced at the redox catalyst;
(d) a membrane separating the anode half-cell and the cathode half-cell; and
(e) an electrical circuit connecting the anode electrode and the cathode electrode.

2. The fuel cell or electrosynthetic cell of claim 1 , wherein the fuel cell or electrosynthetic cell is a fuel cell.

3. The fuel cell or electrosynthetic cell of claim 1 , wherein the fuel cell or electrosynthetic cell is an electrosynthetic cell.

4. The fuel cell or electrosynthetic cell of claim 1 , wherein the membrane is a cation selective membrane.

5. The fuel cell or electrosynthetic cell of claim 1 , wherein the reduced form of the redox mediator is selected from the group consisting of a substituted 1,2 dihydroxybenzene, a substituted 1,4 dihydroxybenzene, and a substituted hydroxylamine.

6. The fuel cell or electrosynthetic cell of claim 5 , wherein one or more hydrogen atoms on the ring of the substituted dihydroxybenzene is substituted with a substituent group that is independently selected from the group consisting of an alkyl with less than ten carbons, an aryl, a fused aryl, a heterocycle, an alkenyl, an alkynyl, a cycloalkyl, an amine, a protonated amine, a quaternary amine, sulfate, a sulfonate, sulfonic acid, a phosphate, a phosphonate, a phosphinate, a ketone, an aldehyde, a hydrazone, an oxime, a nitrone, an ether, an ester, a halide, a nitrile, a carboxylate, an amide, a thioether, a fluoroalkyl, a perfluoroalkyl, a pentafluorosulfanyl, a sulfonamide, a sulfonic ester, an imide, a carbonate, a carbamate, an urea, a sulfonylurea, an azide, a sulfone, a sulfoxide, an amine oxide, phosphine oxide, a quaternary phosphonium, a quaternary borate, a siloxane, and a nitro.

7. The fuel cell or electrosynthetic cell of claim 6 , wherein the fused aryl is selected from the group consisting of napthohydroquinone and derivatives thereof, and anthrahydroquinone and derivatives thereof.

8. The fuel cell or electrosynthetic cell of claim 5 , wherein one or more nitrogen-bound hydrogen atoms in the substituted hydroxylamine is substituted with a substituent group that is independently selected from the group consisting of an alkyl with less than ten carbons, an aryl, a cycloalkyl, and a bicycloalkyl.

9. The fuel cell or electrosynthetic cell of claim 8 , wherein both nitrogen-bound hydrogen atoms can be substituted with the same or different substituents, and the two substituents are linked, thus forming a heterocycle.

10. The fuel cell or electrosynthetic cell of claim 8 , wherein one or more of the substituent groups further comprises an alkyl with less than ten carbons, an aryl, a heterocycle, an alkenyl, an alkynyl, a cycloalkyl, an amine, a protonated amine, a quaternary amine, sulfate, a sulfonate, sulfonic acid, phosphate, a phosphonate, a phosphinate, a ketone, an aldehyde, an oxime, a hydrazone, a nitrone, an ether, an ester, a halide, a nitrile, carboxylate, an amide, a thioether, a fluoroalkyl, a perfluoroalkyl, a pentafluorosulfanyl, a sulfonamide, a sulfonic ester, an imide, carbonate, a carbamate, urea, a sulfonylurea, an azide, a sulfone, a sulfoxide, an amine oxide, a phosphine oxide, a quaternary phosphonium, a quaternary borate, a siloxane, a nitro, and combinations of two or more thereof on the same or on different positions on the substituent.

11. The fuel cell or electrosynthetic cell of claim 1 , wherein the heterogeneous redox catalyst comprises one or more metals selected from the group consisting of Pt, Pd, Ru, Co, Mn, Fe, Cu, V, Mo, Ag, and W.

12. The fuel cell or electrosynthetic cell of claim 1 , wherein the heterogeneous redox catalyst is attached to a support.

13. The fuel cell or electrosynthetic cell of claim 12 , wherein the heterogeneous redox catalyst is dispersed on the support.

14. The fuel cell or electrosynthetic cell of claim 12 , wherein the support comprises a non-conductive material.

15. The fuel cell or electrosynthetic cell of claim 1 , wherein the heterogeneous redox catalyst is contained within a reactor.

16. The fuel cell or electrosynthetic cell of claim 15 , wherein the electrolyte solution comprising the redox mediator and an oxidizing agent are flowing through the reactor, whereby the redox mediator is oxidized and the oxidizing agent is reduced.

17. The fuel cell or electrosynthetic cell of claim 16 , wherein the oxidizing agent is oxygen.

18. A method of producing electricity, comprising:
contacting the anode half-cell of the fuel cell of claim 1 with a fuel; and
contacting the cathode half-cell of the fuel cell of claim 1 with O 2 ;
whereby the fuel is oxidized, O 2 is reduced, and electricity is produced.

19. A method of producing a desired chemical product, comprising:
contacting the anode half-cell of the electrosynthetic cell of claim 1 with a precursor chemical; and
contacting the cathode half-cell of the electrosynthetic cell of claim 1 with O 2 ;
whereby the precursor chemical is oxidized to the desired product, and the O 2 is reduced.

Assignees

• Wisconsin Alumni Res Found

Inventors

• Stahl Shannon S
• Gerken James B
• Anson Colin W

Classifications

• H01M4/9008

  Organic or organo-metallic compounds · CPC title

• H01M8/20

  Indirect fuel cells, e.g. fuel cells with redox couple being irreversible (H01M8/18 takes precedence) · CPC title

• H01M8/188 Primary

  by recharging of redox couples containing fluids; Redox flow type batteries · CPC title

• C25B1/00

  Electrolytic production of inorganic compounds or non-metals · CPC title

• C25B9/08

  Chemistry & Metallurgy · mapped topic