REDOX FLOW BATTERY WITH A BALANCING CELL

A redox flow battery with an electrochemical balancing cell having first and second chambers. The first chamber includes a catalyst coated substrate and the second chamber includes an electrode. Each receives an electrolyte from the redox flow battery. There is a single interface between the two chambers. The balancing cell reverses parasitic reactions in the first chamber that occur in the redox flow battery. The products of the reversed reactions are carried away from the electrochemical balancing cell and back to the redox flow battery in the electrolyte that carried the reactant to the first chamber. Also, processes for reversing a parasitic reaction in a redox flow battery.

FIELD OF THE INVENTION

This invention relates generally to redox flow batteries and more specifically, to an electrochemical balancing cell in redox flow batteries.

BACKGROUND OF THE INVENTION

Aqueous redox flow batteries (RFBs) with sufficiently high voltages, such as all-iron or all-vanadium batteries, will produce electrochemical side reactions that form a gas, for example, oxygen or hydrogen.

Generally, a redox flow battery includes an anode, a cathode, an anolyte or negative electrolyte, a catholyte or positive electrolyte, and an ion-selective membrane. The ion-selective membrane provides a semipermeable membrane between the anolyte and the catholyte. Pumps introduce and recirculate the anolyte to the anode and the catholyte to the cathode, respectively. In an all-iron RFB, the anolyte includes mostly iron (II), Fe2+. The catholyte includes mostly iron (III), Fe3+. During charging of the iron RFB, the reaction in the anolyte at the anode is Fe2++2e−→Fe0. The reaction in the catholyte at the cathode is 2Fe2+→2Fe3++2e−. During discharge, the reaction in the anolyte at the anode is Fe0→Fe2++2e−and the reaction in the catholyte at the cathode is 2Fe3++2e−→2Fe2. As noted above, various undesired side reactions occur in the RFBs.

More specifically, an all-iron RFB typically operates with an acidic electrolyte which produces hydrogen gas as a parasitic side reaction. This reaction removes electrons from the positive electrolyte and protons from the negative electrolyte.

This has the net effect of creating an imbalance in the state of charge of the battery. The positive electrolyte is “charged” during this side reaction, but no iron is plated from the negative electrolyte to counter the “charging.”

Eventually, if there is no remedy, this imbalance in the state of charge of the battery will lead to cell failure. Thus, RFBs need a mechanism to reverse this process to balance the cell.

While presumably effective for their intended purposes, the current processes and systems for rebalancing the cells in an RFB suffer from drawbacks. In a first conventional method, an interface is created across a membrane between the positive electrolyte and the hydrogen gas. In this cell, the hydrogen is oxidized to protons (H+) and the Fe3+is reduced to Fe2+. When the reaction occurs, the state of charge is balanced, however the protons (H+) migrate into the positive electrolyte. This essentially takes protons (H+) from the negative electrolyte (during hydrogen generation) and releases them into the positive electrolyte (during rebalancing).

In another method, a flow through cell is provided between a hydrogen gas chamber and the positive electrolyte chamber. This design allows for the same electrochemical state of charge balancing. Additionally, this configuration provides for the direct insertion of protons (H+) back into the negative electrolyte instead of into the positive. This, in effect, balances not only the state of charge but also the pH of the negative electrolyte. However, this design requires a second membrane, and also requires that one of the membranes is highly conductive for proton (H+) transport. These two factors increase the cost of the rebalancing cell.

Accordingly, it would be desirable to provide a rebalancing cell for an RFB which provides for the state of charge balancing and maintains the protons in the negative electrolyte without requiring multiple membranes between the half-cells of the balancing cell.

SUMMARY OF THE INVENTION

One or more rebalancing cells for an RFB have been invented which balance the state of charge of the positive electrolyte and the pH of the negative electrolyte, however, without requiring a highly proton conductive membrane or membrane electrode assembly.

In one new configuration, the first chamber of the rebalancing cell includes an upper gaseous portion above the negative electrolyte. A catalyst spans the gaseous and liquid phases to create a series of triple interfaces between the catalyst, the gas, and the electrolyte. When the oxidation reaction occurs, the protons (H+) are carried directly into the negative electrolyte without the use of an additional membrane. Buoyancy may be used to generate the gas-electrolyte interface. This removes the need for a highly proton conductive membrane between the gas and negative electrolytes saving on failure points and cost.

In another new configuration, hydrogen gas, the product of the parasitic reaction in the specified RFB, is combined with the negative electrolyte before the electrolyte is passed into the reaction chamber. A valve is used to control the flow of the hydrogen gas, while the electrolyte can be continuously flowed through the chamber. Such a configuration also provides new processes for controlling the cell in reversing the parasitic reaction.

Thus, various configurations of the present invention do not require multiple membranes for multiple interfaces. Additionally, the present invention is able to balance state of charge of the positive electrolyte and pH of the negative electrolyte—without requiring a highly proton conductive membrane or membrane electrode assembly.

Therefore, the present invention may be characterized, in at least one aspect, as providing a redox flow battery having a redox flow battery cell, and an electrochemical balancing cell. The electrochemical balancing cell includes: a first chamber with an inlet for a first electrolyte, an outlet for the first electrolyte, and a catalyst coated substrate; a second chamber comprising an inlet for a second electrolyte, an outlet for the second electrolyte, and an electrode; and, a separator forming an interface between the first chamber and the second chamber. The first chamber is configured to receive a stream of a gas from the redox flow battery cell. The first electrolyte includes a reaction product from an oxidation or reduction of the gas.

The first chamber of the electrochemical balancing cell may further include an inlet for the stream of the gas. The first chamber of the electrochemical balancing cell may further include an upper portion configured to receive the gas from the inlet for the stream of the gas and a lower portion configured to receive the first electrolyte from the inlet for the first electrolyte. The catalyst coated substrate may extend between the upper portion and the lower portion. The first chamber further may include an outlet for a gaseous effluent.

The first chamber may have a T-shape, with a lower portion and an upper portion that is wider than the lower portion.

The gas from the stream of the gas may be introduced to the first chamber of the electrochemical balancing cell with the first electrolyte via the inlet for the first electrolyte. The inlet for the first electrolyte may be located at a height in the first chamber of the electrochemical balancing cell that is lower than a height of the outlet for the first electrolyte. The catalyst coated substrate may include a catalyst supported on an electrically conductive porous substrate. The redox flow battery may further include a control valve in a line in communication with the inlet for the first electrolyte, and the control valve may be configured to adjust an amount of the gas passed to the first chamber of the electrochemical balancing cell.

In a second aspect, the present invention may be generally characterized as providing a redox flow battery having: an anode half-cell with an anode and an anolyte flowing through the anode chamber; a cathode half-cell with a cathode and a catholyte flowing through the cathode chamber, the cathode in electrical communication with the anode; and, an electrochemical balancing cell. The electrochemical balancing cell may include: a first chamber comprising an inlet for the anolyte, an outlet for the anolyte, and a catalyst coated substrate; a second chamber comprising an inlet for the catholyte, an outlet for the catholyte, and an electrode; and, a separator forming an interface between the first chamber and the second chamber. The first chamber may be configured to receive a gaseous reaction product produced at the anode, and the anolyte may include a reaction product from an oxidation reaction, at the catalyst coated substrate, of the gaseous reaction product.

The first chamber of the electrochemical balancing cell may further include an inlet for a stream of the gaseous reaction product and an outlet for a gaseous effluent. The first chamber may include an upper portion configured to receive the stream of the gaseous reaction product from the inlet for the stream of the gaseous reaction product and a lower portion configured to receive the anolyte from the inlet for the anolyte. The catalyst coated substrate may extend between the upper portion and the lower portion.

The first chamber may have a T-shape, with a lower portion and an upper portion that is wider than the lower portion.

A stream of the gaseous reaction product may be introduced to the first chamber with the anolyte via the inlet for the anolyte. The inlet for the anolyte may be located at a height in the first chamber that is lower than a height of the outlet for the anolyte. A substrate of the catalyst coated substrate may be a porous substrate. The redox flow battery may further include a control valve in a line in communication with the inlet for the anolyte. The control valve may be configured to adjust an amount of the gaseous reaction product to the first chamber.

In yet another aspect, the present invention, broadly, provides a process for reversing a parasitic reaction in a redox flow battery by: monitoring at least one condition of an electrolyte of a redox flow battery; adjusting, when the at least one condition is above or below a preset limit, a flow of a gaseous steam to an electrochemical balancing cell of the redox flow battery, the gaseous stream comprising a gaseous reaction product from the redox flow battery; and, oxidizing or reducing the gaseous reaction product in the electrochemical balancing cell. The flow of the gaseous steam may be adjusted independent of a flow of an electrolyte passed to the electrochemical balancing cell.

In a further embodiment, the present invention generally may be characterized as providing a process for reversing a parasitic reaction in a redox flow battery by: monitoring a pH of a negative electrolyte of a redox flow battery; adjusting, when the at least one condition is above or below a preset limit, the pH of the negative electrolyte by adjusting a flow of a hydrogen gas to a chamber of an electrochemical balancing cell, the chamber receiving the negative electrolyte; oxidizing the hydrogen gas in the electrochemical balancing cell; and, maintaining a constant voltage of the electrochemical balancing cell while the flow a hydrogen gas is adjusted.

Additional aspects, embodiments, and details of the invention, all of which may be combinable in any manner, are set forth in the following detailed description of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned above, a new flow battery has been invented which includes a rebalancing cell for reversing a parasitic reaction product from the flow battery. According to the present invention, the half cells of the rebalancing cell are separated by a single interface with a separator. This reduces the number of interfaces and the number of separators that are required for the rebalancing cell. Additionally, in the present invention, the reversed reaction products are maintained in the electrolyte with the parasitic reaction product. Additionally, in at least one embodiment, the rebalancing cell provides for new processes for reversing the parasitic reaction.

With these general principles in mind, one or more embodiments of the present invention will be described with the understanding that the following description is not intended to be limiting.

As shown inFIG. 1, a flow battery10includes a redox flow battery cell12and an electrochemical balancing cell14. The redox flow battery cell12includes two oppositely charged half cells16,18with a separator20between the two half cells16,18of the electrochemical cell. The separator can be comprised of an ionic conducting material such as a microporous or ion-exchange membrane.

Each half cell16,18includes an electrode22,24that is formed from a suitably conductive material, such as a metal, carbon, graphite, and the like, and the materials for two can be the same or different. Pumps26,28circulate an electrolyte30,32from tanks34,36, to one of the half cells16,18.

In the depicted redox flow battery cell12, a first electrode22is an anode and a first electrolyte30is an anolyte. Accordingly, the second electrode24is the cathode and the second electrolyte32is a catholyte. This is merely exemplary and is not intended to be limiting.

More specifically, the following description may be focused, in parts, on oxidizing hydrogen gas to distribute protons (H+) into the negative electrolyte. However, the principals of the present invention could be implemented in a variety of different flow battery configurations. For example, the gas may be hydrogen, oxygen, chlorine. Additionally, the products of the gas reaction may be deposited into the positive electrolyte. Thus, this description is not intended to be limiting.

In a known manner, the electrodes22,24are in electrical communication through a closed circuit which causes reactions at the electrodes22,24. As discussed above, over the course of time, hydrogen gas is generated at the anode22and circulates within the anolyte30. In addition to lowering the state of charge of the anolyte30(compared with the catholyte32), the production of the hydrogen gas results in an increase pH of the anolyte30. Further, flows of ions though the separator20offsets the charge balance between the anolyte30and the catholyte32. To counteract the production of the hydrogen, the pH change and the state of change imbalance, the anolyte30and the catholyte32are passed to the electrochemical balancing cell14.

Generally, the electrochemical balancing cell14includes a first chamber38which receives one of the electrolytes30,32and which includes a catalyst coated substrate40. The electrochemical balancing cell14also includes a second chamber42which receives the other of the electrolytes30,32and which includes an electrode44. A separator46forms an interface between the first and second chambers38,42. Based on a voltage applied, hydrogen in the anolyte30can be oxidized at the catalyst coated substrate40. As discussed above, the present invention provides configurations for the electrochemical balancing cell14.

Accordingly, turning toFIG. 2, an embodiment of the electrochemical balancing cell14according to the present invention is shown in more detail. The first chamber38of the electrochemical balancing cell14includes an inlet48for the first electrolyte30and an outlet50for the first electrolyte30. The first chamber38may also include an inlet52for a stream of gas54and an outlet56for a gaseous effluent58. The stream of gas54may be passed from the head space of the first tank34, with the gaseous effluent58being passed back to same. The stream of gas54may also be passed to the head space of the second tank36to form a pressure equalizing headspace connection. As will be appreciated, the head spaces of the two tanks36,34are preferably in communication to avoid a gas build up on in one of the head spaces. The second chamber42includes an inlet60for the second electrolyte32and an outlet62for the second electrolyte32.

As can be best seen inFIG. 3, the first chamber38preferably includes an upper portion64and a lower portion66. The upper portion64receives the stream of gas54from the inlet52and is in open communication with the outlet56for the gaseous effluent58. The lower portion66receives the first electrolyte30via the inlet48for the first electrolyte30and provides the first electrolyte30to the outlet50for the first electrolyte30. The catalyst coated substrate40extends between the upper and lower portions64,66of the first chamber38.

The placement and positioning of the inlets48,52and outlets50,56in the first chamber30may be used to achieve a stable level of negative electrolyte on the surface of the catalyst coated substrate40at all times while concurrently supplying a method for the wicking of produced protons (H+) away from the catalyst coated substrate40. Accordingly, control valves (not shown) be used on the lines bringing the various streams to the first chamber to allow for adjustment to ensure a proper level of liquid within the first chamber38.

In a preferred configuration, the first chamber38comprises a T-shape, with the lower portion66having a width W1(distance along a line extending between the inlets48,52and the outlets50,56), and the upper portion64having a width W2greater than the width W1of the lower portion66. Preferably, the width W2of the upper portion64is also greater that a width of the catalyst coated substrate40.

By using the upper and lower portions64,66receiving the stream of gas54and the first electrolyte30, respectively, the first chamber38is provided with an interface between a liquid phase (the first electrolyte30) and a gaseous phase (the gas from the stream of gas54). It is at this interface that, both hydrogen (from the gas) and the first electrolyte30contact the catalyst on the catalyst coated substrate40and can be oxidized to protons (H+). Additionally, the same reaction may occur lower, within the liquid, based on dissolved hydrogen present in the first electrolyte30.

Accordingly, it is preferred that the catalyst coated substrate40comprises a high surface area. By “high” surface area, it is meant that the surface area of the substrate is at least 1%, or at least 5%, or at least 10%, or at least 25% greater than the area of the substrate as calculated by adding 2(length×width) and 2(width×depth) and 2(length×depth). For example, the substrate of the catalyst coated substrate40may be a porous material, like mesh, in order to provide a catalyst coated substrate40with a high surface area. The substrate of the catalyst coated substrate40may have undulations, a pattern, or a texture to increase the surface area of the catalyst coated substrate40.

In addition to having a high surface area, the support of the catalyst coated substrate40should be conductive and in electrical communication with the electrode of the second chamber. Contemplated materials include graphite, carbon cloth, felt, paper, titanium mesh, conductive plastic, and iron mesh.

Further, the catalyst deposited on the catalyst coated substrate40depends on the chemistry of the redox flow battery cell12. In the depicted example, where the parasitic reaction results in the production of hydrogen gas, platinum may be a catalyst. Other materials may be used like ruthenium, palladium, iridium, and alloys thereof.

Returning toFIG. 2, two gaskets68may be used with the separator46, one on each side, to seal the separator46between the two chambers38,42. The chambers38,42may be formed in materials that act as current collectors.

The separator46is configured to allow for ions to flow between the two electrolytes. Exemplary materials include microporous or ion-exchange membranes. As should be appreciated, the separator may be a layered material with the materials forming a single interface for the electrochemical balancing cell14.

In use, when hydrogen is oxidized in the first chamber38, the produced protons (H+) will remain in the anolyte30unlike previous designs of electrochemical balancing cells which have the protons deposited into the catholyte or in another fluid. Further, unlike previous designs which require multiple interfaces and thus multiple membranes, the depicted electrochemical balancing cell14only requires a single interface between the two chambers38,42.

Turning toFIG. 4, another embodiment for an electrochemical balancing cell112according to the present invention is shown. The same elements in the electrochemical balancing cell112ofFIG. 4and the electrochemical balancing cell14inFIGS. 2 and 3are identified by the same reference numerals.

In the electrochemical balancing cell112ofFIG. 4, the first chamber38includes the inlet48for the first electrolyte30. However, instead of the separate inlet52for the stream of gas54in the previous embodiment, in this embodiment, the stream of gas54is introduced to the first chamber38of the electrochemical balancing cell14with the first electrolyte30via the inlet48for the first electrolyte30.

Accordingly, lines, pipes, or conduits carrying the first electrolyte30and the stream of gas54converge at a junction70prior to the first electrolyte30being passed into the first chamber38. A control valve72may be disposed in the line carrying the stream of gas54. The control valve72is configured to adjust an amount of the stream of gas54that is passed to the first chamber38of the electrochemical balancing cell14.

InFIG. 4the first electrolyte30flows vertically (bottom to top), while inFIGS. 2 and 3, the first electrolyte30flows horizontally (left to right). Accordingly, in the embodiment ofFIG. 4, the inlet48for the first electrolyte30is located lower along a height H1of the first chamber38than the outlet50for the first electrolyte30.

The electrochemical balancing cell112depicted inFIG. 4provides the same benefits of as the one depicted inFIGS. 2 and 3. Specifically, the electrochemical balancing cell112results in the oxidized products remaining the first electrolyte30. Additionally, the electrochemical balancing cell112only has a single interface and thus does not require membranes for multiple interfaces.

The electrochemical balancing cell112ofFIG. 4also provides a configuration that may be operated to extend the life of the catalyst. More specifically, the electrochemical balancing cell112may be operated with a continuous voltage applied to the electrode and the catalyst coated substrate40. The valve72can be opened and closed to start and stop the flow of the stream of gas54to adjust the current. When the valve72is closed, no gas will be oxidized, but the voltage will reduce or prevent the catalyst from degrading over time.

Accordingly, such a configuration allows for new processes for reversing the parasitic reaction in a redox flow battery. As in conventional processes, the present processes include monitoring at least one condition of an electrolyte30,32, of the redox flow battery10. For example, the condition may be a pH, a state of charge, a conductivity, or a pressure in the head spaces of one of the tanks34,36(see,FIG. 1) associated with one of the electrolytes30,32. Conventional sensors may be utilized and may be in communication with a controller or a computing devices.

When the measured value of the condition is above or below a preset limit, a flow of the gaseous steam54to an electrochemical balancing cell of the redox flow battery may be adjusted via the valve72without necessarily require a change to the flow of the first electrolyte30. Thus, unlike conventional processes, this allows for the flow of the gaseous steam54to be adjusted independent of the flow of the electrolyte30passed to the electrochemical balancing cell112. Additionally, unlike conventional processes a constant voltage be maintained between the electrode44and the catalyst coated substrate40—even when the gaseous stream54is not flowing to the first chamber38. This constant voltage will help prevent the catalyst from degrading overtime.

Example

A working example of the present invention was produced for a 5-25 cm2cell. An upper portion of the first chamber was constructed by milling a small active area for the catalyst coated substrate in a graphite current collector. A lower portion of the chamber, in fluid connection with the first, was then drilled into the same current collector. The lower portion of the first chamber was connected to a source of negative electrolyte, and the upper portion of the first chamber was connected to a source of hydrogen. This formed the negative side of the half cell. A positive side was constructed as a normal IFB plate. The same separator was used for the electrochemical rebalancing cell as was used for the redox flow battery cell. All three working fluids (catholyte, anolyte, and hydrogen) were driven by peristaltic pumps to prevent stalling from mass transfer limitations. The catalyst used was a platinum on carbon coated carbon paper. The anolyte contained Fe2+and a supporting electrolyte, and the catholyte contained Fe3+and a supporting electrolyte. The current was monitored via an external system, but the reaction was self-driven.

The performance of the working example is shown inFIG. 5. As can be appreciated fromFIG. 5, the negative pH of the working example was lowered when the device turned on (as signified by an increase in the line representing charge passed). This was capable of affecting pH control at different pH conditions, both at around 3.0 and also around 4.0 in the negative electrolyte.

Accordingly, the present invention provides rebalancing cells for redox flow batteries that provide advantages over the current configurations.

It should be appreciated and understood by those of ordinary skill in the art that various other components such as valves, pumps, filters, coolers, etc. were not shown in the drawings as it is believed that the specifics of same are well within the knowledge of those of ordinary skill in the art and a description of same is not necessary for practicing or understanding the embodiments of the present invention.

Any of the above lines, conduits, units, devices, vessels, surrounding environments, zones or similar may be equipped with one or more monitoring components including sensors, measurement devices, data capture devices or data transmission devices. Signals, process or status measurements, and data from monitoring components may be used to monitor conditions in, around, and on process equipment. Signals, measurements, and/or data generated or recorded by monitoring components may be collected, processed, and/or transmitted through one or more networks or connections that may be private or public, general or specific, direct or indirect, wired or wireless, encrypted or not encrypted, and/or combination(s) thereof; the specification is not intended to be limiting in this respect.

Signals, measurements, and/or data generated or recorded by monitoring components may be transmitted to one or more computing devices or systems. Computing devices or systems may include at least one processor and memory storing computer-readable instructions that, when executed by the at least one processor, cause the one or more computing devices to perform a process that may include one or more steps. For example, the one or more computing devices may be configured to receive, from one or more monitoring component, data related to at least one piece of equipment associated with the process. The one or more computing devices or systems may be configured to analyze the data. Based on analyzing the data, the one or more computing devices or systems may be configured to determine one or more recommended adjustments to one or more parameters of one or more processes described herein. The one or more computing devices or systems may be configured to transmit encrypted or unencrypted data that includes the one or more recommended adjustments to the one or more parameters of the one or more processes described herein.

Specific Embodiments

A first embodiment of the invention is a redox flow battery, comprising a redox flow battery cell, and an electrochemical balancing cell comprising a first chamber comprising an inlet for a first electrolyte, an outlet for the first electrolyte, and a catalyst coated substrate; a second chamber comprising an inlet for a second electrolyte, an outlet for the second electrolyte, and an electrode, and, a separator forming an interface between the first chamber and the second chamber, wherein the first chamber is configured to receive a stream of a gas from the redox flow battery cell, and wherein the first electrolyte includes a reaction product from an oxidation or reduction of the gas. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the first chamber of the electrochemical balancing cell further comprises an inlet for the stream of the gas. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the first chamber of the electrochemical balancing cell further comprises an upper portion configured to receive the gas from the inlet for the stream of the gas; and, a lower portion configured to receive the first electrolyte from the inlet for the first electrolyte. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the catalyst coated substrate extends between upper portion and the lower portion. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the first chamber further comprises an outlet for a gaseous effluent. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the first chamber comprises a T-shape, with a lower portion and an upper portion that is wider than the lower portion. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the gas from the stream of the gas is introduced to the first chamber of the electrochemical balancing cell with the first electrolyte via the inlet for the first electrolyte. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the inlet for the first electrolyte is located at a height in the first chamber of the electrochemical balancing cell that is lower than a height of the outlet for the first electrolyte. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, wherein the catalyst coated substrate comprises a catalyst supported on an electrically conductive porous substrate. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph, further comprising a control valve in a line in communication with the inlet for the first electrolyte, wherein the control valve is configured to adjust an amount of the gas passed to the first chamber of the electrochemical balancing cell.

A second embodiment of the invention is a redox flow battery comprising an anode half-cell comprising an anode and an anolyte flowing through the anode chamber; a cathode half-cell comprising a cathode and a catholyte flowing through the cathode chamber, the cathode in electrical communication with the anode; and, an electrochemical balancing cell comprising a first chamber comprising an inlet for the anolyte, an outlet for the anolyte, and a catalyst coated substrate. a second chamber comprising an inlet for the catholyte, an outlet for the catholyte, and an electrode; and, a separator forming an interface between the first chamber and the second chamber, wherein the first chamber is configured to receive a gaseous reaction product produced at the anode, and wherein the anolyte includes a reaction product from an oxidation reaction, at the catalyst coated substrate, of the gaseous reaction product. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the first chamber of the electrochemical balancing cell further comprises an inlet for a stream of the gaseous reaction product and an outlet for a gaseous effluent. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the first chamber comprises an upper portion configured to receive the stream of the gaseous reaction product from the inlet for the stream of the gaseous reaction product; and, a lower portion configured to receive the anolyte from the inlet for the anolyte. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the catalyst coated substrate extends between the upper portion and the lower portion. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the first chamber comprises a T-shape, with a lower portion and an upper portion that is wider than the lower portion. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein a stream of the gaseous reaction product is introduced to the first chamber with the anolyte via the inlet for the anolyte. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein the inlet for the anolyte is located at a height in the first chamber that is lower than a height of the outlet for the anolyte. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, wherein a substrate of the catalyst coated substrate comprises a porous substrate. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the second embodiment in this paragraph, further comprising a control valve in a line in communication with the inlet for the anolyte, wherein the control valve is configured to adjust an amount of the gaseous reaction product to the first chamber.

A third embodiment of the invention is a process for reversing a parasitic reaction in a redox flow battery, comprising monitoring at least one condition of an electrolyte of a redox flow battery; adjusting, when the at least one condition is above or below a preset limit, a flow of a gaseous steam to an electrochemical balancing cell of the redox flow battery, the gaseous stream comprising a gaseous reaction product from the redox flow battery; and, oxidizing or reducing the gaseous reaction product in the electrochemical balancing cell, wherein the flow of the gaseous steam is adjusted independent of a flow of an electrolyte passed to the electrochemical balancing cell.

A fourth embodiment of the invention is a process for reversing a parasitic reaction in a redox flow battery, the process comprising monitoring a pH of a negative electrolyte of a redox flow battery; adjusting, when the at least one condition is above or below a preset limit, the pH of the negative electrolyte by adjusting a flow of a hydrogen gas to a chamber of an electrochemical balancing cell, the chamber receiving the negative electrolyte; oxidizing the hydrogen gas in the electrochemical balancing cell; and, maintaining a constant voltage of the electrochemical balancing cell while the flow a hydrogen gas is adjusted.