Methods and systems for removing impurities from electrolyte solutions having three or more valence states. In some embodiments, a method includes electrochemically reducing an electrolyte solution to lower its valence state to a level that causes impurities to precipitate out of the electrolyte solution and then filtering the precipitate(s) out of the electrolyte solution. In embodiments in which the electrolyte solution is desired to be at a valence state higher than the precipitation valence state, a method of the disclosure includes oxidizing the purified electrolyte solution to the target valence.

There is described a direct carbon fuel cell system. The system includes fuel cells, each fuel cell having a porous fuel cell anode and a fuel cell cathode. The system further includes a molten carbonate electrolyte and a fuel supply apparatus for flowing a fuel slurry having carbon particles and a carbon carrier fluid to the fuel cell anodes in parallel. The carbon carrier fluid has a same composition as the molten carbonate electrolyte. An oxidant supply apparatus flows an oxygen-containing stream to the fuel cell cathodes in parallel. An electrolyte circulation apparatus circulates the molten carbonate electrolyte in contact with each of the fuel cells. During operation of the direct carbon fuel cell system to generate electric power, carbon is oxidized at the fuel cell anodes to produce carbon dioxide, and at the fuel cell cathodes oxygen and carbon dioxide react to produce carbonate ions.

The present invention is directed to novel membrane electrode assemblies, and devices and systems incorporating them. Representative membrane electrode assemblies comprise (a) a first, porous electrode; (b) a buffer layer optionally comprising an aqueous solution comprising a pH buffer; (c) a membrane; and (d) a second, porous electrode comprising a catalyst for the generation of oxygen (O2); wherein the membrane is interposed between the first electrode and the second electrode, and the buffer layer is interposed between the membrane and the first electrode.

A battery system comprising a sealed aqueous flow battery that employs a passive, in-tank electrolyte recombination system. The recombination system allows for electrolyte stabilization in batteries where hydrogen evolution may occur as a side reaction without the need to use any externally-supplied rebalancing reactants. The system is a passive system that does not require a control system, additional pumps, or pumping energy.

A method of rebalancing electrolytes in a redox flow battery system comprises directing hydrogen gas generated on the negative side of the redox flow battery system to a catalyst surface, and fluidly contacting the hydrogen gas with an electrolyte comprising a metal ion at the catalyst surface, wherein the metal ion is chemically reduced by the hydrogen gas at the catalyst surface, and a state of charge of the electrolyte and pH of the electrolyte remain substantially balanced.

Flow battery systems are provided, including flowing a liquid electrolyte from a storage tank of a flow battery system to an electrode chamber of the flow battery system, the liquid electrolyte comprising a solvent and a first active ion dissolved in the solvent, wherein the storage tank comprises the liquid electrolyte and a first solid composed of the active ion and an ion of the solvent; inducing an electrochemical reaction in the electrode chamber to convert the first active ion dissolved in the solvent to a second active ion dissolved in the solvent, wherein the first solid dissolves to provide more of the first active ion dissolved in the solvent; flowing the liquid electrolyte comprising the solvent and the second active ion dissolved in the solvent from the electrode chamber back to the storage tank; and precipitating a second solid composed of the second active ion and the ion of the solvent in the storage tank.

Methods and systems are provided for a rebalancing reactor of a flow battery system. In one example, a pH of a battery electrolyte may be maintained by the rebalancing reactor by applying a negative potential to a catalyst bed of the rebalancing reactor. A performance of the rebalancing reactor may further be maintained by treating the catalyst bed with deionized water.

Methods and systems are provided for a rebalancing reactor of a flow battery system. In one example, a pH of a battery electrolyte may be maintained by the rebalancing reactor by applying a negative potential to a catalyst bed of the rebalancing reactor. A performance of the rebalancing reactor may further be maintained by treating the catalyst bed with deionized water.

A plant includes a fuel supply line for supplying high-pressure fuel gas; and at least one expander disposed in the fuel supply line and configured to extract power from the high-pressure fuel gas by expanding the high-pressure fuel gas.

A controller stops flow of posolyte through a positive electrode chamber of a flow cell to trap the posolyte within the positive electrode chamber and hydraulically isolate the flow cell without stopping flow of negolyte through a negative electrode chamber of the flow cell, discharges the flow cell until hydrogen gas is evolved at a reactive surface of the positive electrode chamber while the posolyte is trapped within the positive electrode chamber, and subsequently discontinues the discharge and restarts the flow of the posolyte through the positive electrode chamber.