Use of polyoxometalate mediators

Patent metadata

Field	Value
Publication number	US-11851773-B2
Application number	US-202218086364-A
Country	US
Kind code	B2
Filing date	Dec 21, 2022
Priority date	Jan 24, 2018
Publication date	Dec 26, 2023
Grant date	Dec 26, 2023

Abstract

A method is disclosed of manufacturing a semiconductor structure comprising an (001) oriented zincblende structure group III-nitride layer, such as GaN. The layer is formed on a 3C-SiC layer on a silicon substrate. A nucleation layer is formed, recrystallized and then the zincblende structure group III-nitride layer is formed by MOVPE at temperature T3 in the range 750-1000° C., to a thickness of at least 0.5μ. There is also disclosed a corresponding semiconductor structure comprising a zincblende structure group III-nitride layer which, when characterized by XRD, shows that the substantial majority, or all, of the layer is formed of zincblende structure group III-nitride in preference to wurtzite structure group III-nitride.
The present invention provides methods for producing hydrogen using a mediator that is capable of reversibly donating and accepting four or more electrons. A method of the invention comprises the steps of reducing a mediator by four or more electrons to yield a reduced mediator, and oxidising a reduced mediator to yield a mediator, and reducing protons to yield hydrogen.

First claim

The invention claimed is:

1. A method for producing hydrogen, the method comprising the steps of:
(i) reducing a mediator by four or more electrons to yield a reduced mediator;
(ii) oxidising a reduced mediator to yield a mediator, and reducing protons to yield hydrogen;
wherein the reduced mediator of step (i) is used as the reduced mediator of step (ii), or the mediator of step (ii) is used as the mediator of step (i);
wherein the mediator in step (i) is (a) reduced by five or more electrons and/or (b) provided in an aqueous electrolyte solution at a concentration of at least 2 mM.

2. The method of claim 1 , wherein the mediator is reduced by six or more electrons, or seven or more electrons.

3. The method of claim 1 , wherein the mediator is reduced by ten or more electrons, or 18 electrons.

4. The method of claim 1 , wherein the mediator is a polyoxometalate.

5. The method of claim 4 , wherein the polyoxometalate has 12 or more, or 18 or more metal atoms.

6. The method of claim 4 , wherein the polyoxometalate is of formula [X 2 M 18 O 62 ] n− , where M is a metal, selected from Mo, W and V, and mixtures thereof, X is selected from P and S and mixtures thereof, and n is 3, 4, 5 or 6 as appropriate.

7. The method of claim 6 , wherein the polyoxometalate is of formula [P 2 W 18 O 62 ] 6− .

8. The method of claim 1 , where step (ii) comprises exposing the mediator to a catalyst.

9. The method of claim 8 , wherein the catalyst is a platinum-containing catalyst.

10. A battery comprising a working electrode and a counter electrode, wherein the working electrode side comprises an electrolyte holding a mediator that may reversibly accept 4 or more electrons, and/or a reduced form of the mediator that may reversibly donate 4 or more electrons, and the counter electrode side comprises:
(i) an electrolyte holding a redox active agent in reduced and/or oxidised form; or
(ii) an electrolyte holding an oxygen source, and/or holding or exposed to oxygen, and
wherein the mediator is (a) reduceable by five or more electrons and/or (b) provided in the electrolyte at a concentration of at least 2 mM.

11. The battery of claim 10 , wherein the mediator is reduceable by six or more electrons, or seven or more electrons.

12. The battery of claim 10 , wherein the mediator is reduceable by ten or more electrons, or 18 electrons.

13. The battery of claim 10 , wherein the mediator is a polyoxometalate.

14. The battery of claim 13 , wherein the polyoxometalate has 16 or more, or 18 or more metal atoms.

15. The battery of claim 14 , wherein the polyoxometalate is of formula [X 2 M 18 O 62 ] n− , where M is a metal, selected from Mo, W and V, and mixtures thereof, X is selected from P and S and mixtures thereof, and n is 3, 4, 5 or 6 as appropriate.

16. The battery of claim 15 , wherein the polyoxometalate is of formula [P 2 W 18 O 62 ] 6− .

17. The battery of claim 10 , which is:
(i) a flow battery;
(ii) a charged battery wherein the battery contains predominately the reduced form of the mediator; or
(iii) a discharged battery wherein the battery contains predominately the mediator.

18. The method of claim 1 , wherein the concentration of the mediator in the aqueous electrolyte solution is at least 5, 10, 20 or 50 mM.

19. The method of claim 1 , wherein the concentration of the mediator in the aqueous electrolyte solution is at most 1,000, 2,000 or 5,000 mM.

20. The method of claim 1 , wherein the mediator in step (i) is (b) provided in an aqueous electrolyte solution, which is an acidic aqueous electrolyte solution, for example at a pH of pH 4 or less.

21. The battery of claim 10 , wherein the mediator is provided in an electrolyte at a concentration of at least 5, 10, 20 or 50 mM.

22. The battery of claim 10 , wherein the mediator is provided in an electrolyte is at a concentration of at most 1,000, 2,000 or 5,000 mM.

23. The battery of claim 10 , wherein the mediator is provided in an acidic aqueous electrolyte solution.

Assignees

• Univ Glasgow Court

Inventors

• Cronin Leroy
• Symes Mark
• Chen jia-jia

Classifications

• C25B1/04 Primary

  by electrolysis of water · CPC title

• H01M8/188

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

• H01M12/08

  composed of a half-cell of a fuel-cell type and a half-cell of the secondary-cell type · CPC title

• Y02E60/36

  Hydrogen production from non-carbon containing sources, e.g. by water electrolysis · CPC title

• Y02E60/50

  Fuel cells · CPC title