Systems and methods of decoupled hydrogen generation using energy-bearing redox pairs

Patent metadata

Field	Value
Publication number	US-2018269516-A1
Application number	US-201815988213-A
Country	US
Kind code	A1
Filing date	May 24, 2018
Priority date	Jan 22, 2015
Publication date	Sep 20, 2018
Grant date	—

Abstract

Described herein are systems and methods of hydrogen generation and electrolyte regeneration as independent operations in separate redox flow cells. The operations can be decoupled by using an energy-bearing redox pair that electrochemically bears energy facilitating flexible, efficient hydrogen generation. In one example, the hydrogen generation redox flow cell can include a liquid, energy-bearing electrolyte solution in which at least one species of an energy-bearing redox pair is dissolved, to decouple the hydrogen evolution reaction from the reaction at the opposite electrode (e.g., the oxygen evolution reaction of conventional direct water electrolysis). Each species of the energy-bearing redox pair is associated with a standard electrode potential within the water electrolysis window.

First claim

What is claimed is:

1 . A system of hydrogen generation comprising:
A first redox flow cell generating hydrogen and having:
A positive electrode side oxidizing an energy-bearing redox species dissolved in a liquid, energy-bearing, electrolyte solution to an oxidized state;
A negative electrode side comprising a H + /H 2 half-cell; and
A proton permeable membrane separating the positive electrode and negative electrode sides; and
A second redox flow cell regenerating the liquid, energy-bearing electrolyte solution and having:
A negative electrode side reducing the energy-bearing redox species to a reduced state
A positive electrode side comprising an oxygen evolution reaction (OER) half-cell; and
A proton permeable membrane separating the positive electrode and negative electrode sides;
wherein the energy-bearing redox species is associated with a reversible redox reaction having a standard electrode potential within a water electrolysis voltage window for the electrolyte solution, and wherein the first and second redox flow cells are decoupled for independent operation one from another.

2 . The system of claim 1 , further comprising a circulation sub-system configured to transfer a first, liquid, energy-bearing, electrolyte solution comprising the energy-bearing redox species from the first redox flow cell to the second, and configured to transfer a second, liquid, energy-bearing, electrolyte solution comprising the energy-bearing redox species from the second redox flow cell to the first.

3 . The system of claim 2 , wherein the circulation sub-system further comprises a first storage container configured to store a portion of the first liquid, energy-bearing, electrolyte solution and a second storage container configured to store a portion of the second liquid, energy-bearing, electrolyte solution.

4 . The system of claim 1 , further comprising a controller operably connected to the first and second redox flow cells and configured to select for operation of the first redox flow cell alone, the second redox flow cell alone, or concurrently both based on an energy-market condition.

5 . The system of claim 4 , wherein energy-market condition comprises price of energy supply, energy demand, power grid health, H 2 price, H 2 demand, time of day, weather conditions, or a combination thereof.

6 . The system of claim 1 , wherein the energy-bearing redox species in the reduced and oxidized states comprise Fe 2+ and Fe 3+ , respectively.

7 . The system of claim 1 , wherein the energy-bearing redox species comprises iodine, vanadium, bromine, chlorine, TEMPO, respectively.

8 . The system of claim 1 , wherein the liquid, energy-bearing electrolyte solution comprises an aqueous acid solution.

9 . The system of claim 1 , wherein the aqueous acid solution comprises a dissolved acid having a concentration greater than or equal to 2 M, 4 M, 6 M, 8 M, or 10 M.

10 . The system of claim 1 , wherein the liquid, energy-bearing electrolyte solution comprises the energy-bearing redox species in an amount greater than or equal to 0.5 M, 1 M, 1.5 M, 2 M, 3 M, 4 M, 5 M, or 8 M.

11 . A method of producing fuel comprising the steps of:
generating hydrogen from in a first redox flow cell having a negative electrode side comprising a H + /H 2 half-cell and oxidizing an energy-bearing redox species from a reduced state to an oxidized state on a positive-electrode side, wherein the energy-bearing redox species is dissolved in a liquid, energy-bearing, electrolyte solution and is associated with a reversible redox reaction having a standard electrode potential within a water electrolysis voltage window for the electrolyte solution; and regenerating the liquid, energy-bearing electrolyte solution by reducing the energy-bearing redox species from the oxidized state to the reduced state on a negative-electrode side of a second redox flow cell having a positive electrode side comprising an OER half-cell, wherein the first and second redox flow cells are decoupled for independent operation one from another.

12 . The method of claim 11 , further comprising transferring a first, liquid, energy-bearing, electrolyte solution comprising the energy-bearing redox species in the oxidized state from the first redox flow cell to the second, and transferring a second, liquid, energy-bearing, electrolyte solution comprising the energy-bearing redox species in the reduced state from the second redox flow cell to the first.

13 . The method of claim 12 , further comprising storing a portion of the first liquid, energy-bearing, electrolyte solution in a first storage container and storing a portion of the second liquid, energy-bearing, electrolyte solution in a second storage container.

14 . The method of claim 11 , further comprising the step of selecting said generating hydrogen alone, said regenerating the liquid, energy-bearing electrolyte solution alone, or concurrently both based an energy market condition.

15 . The method of claim 14 , wherein the energy-market condition comprises price of energy supply, energy demand, power grid health, H 2 price, H 2 demand, time of day, weather conditions, or a combination thereof.

16 . The method of claim 11 , further comprising the steps of:
performing said generating step based on a first price of energy supply; and performing said regenerating step based a second price of energy supply; wherein the second price of energy supply is less than the first price of energy supply.

17 . A system comprising an electrolyte-regeneration flow cell system configured to regenerate a spent, liquid, energy-bearing electrolyte solution from a hydrogen-production flow cell system operated independently from the electrolyte-regeneration flow cell system, wherein the energy-bearing electrolyte solution comprises an energy-bearing redox species dissolved therein and associated with a reversible redox reaction having a standard electrode potential within a water electrolysis voltage window for the electrolyte solution.

18 . The system of claim 17 , further comprising a controller operating the electrolyte-regeneration flow cell system, the hydrogen-production flow cell system, or both based on an energy market condition.

19 . The system of claim 18 , wherein the energy market condition comprises price of energy supply, energy demand, power grid health, H 2 price, H 2 demand, time of day, weather conditions, or a combination thereof.

20 . The system of claim 17 , wherein the energy-bearing redox species comprises iron.

Assignees

• Battelle Memorial Institute

Inventors

• Wang Wei
• Lu Dongping
• Shao Yuyan
• Huang Qian

Classifications

• H01M8/188 Primary

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

• H01M8/04925

  Power, energy, capacity or load · CPC title

• C25B1/10

  Chemistry & Metallurgy · mapped topic

• C25B1/04

  by electrolysis of water · CPC title

• C25B9/73

  of the filter-press type · CPC title