A method of the type where a brine solution is converted to an alkali metal hydroxide solution within a diaphragm cell, and the resulting cell liquor from the diaphragm cell is introduced to one or more fuel cells for the conversion of the alkali metal hydroxide to form electricity, the improvement comprising regulating the conversion of alkali metal hydroxide within the fuel cell to a conversion of less than 90%, and then subsequently concentrating the alkali metal hydroxide concentration from the anolyte stream of the fuel cell.

Disclosed are a method and device for using CO.sub.2 mineralization to produce sodium bicarbonate or sodium carbonate and output electric energy. The device comprises an anode area, an intermediate area, and a cathode area. The anode area and the intermediate area are spaced by a negative ion exchange membrane (2). The intermediate area and the cathode area are spaced by a positive ion exchange membrane (3). The anode area, the intermediate area, and the cathode area can accommodate corresponding electrolytes. An anode electrode (1) is disposed in the anode area, a cathode electrode (4) is disposed in the cathode area, and the cathode electrode and the anode electrode are connected through a circuit. A raw material hydrogen gas inlet is disposed in the anode area, and a CO.sub.2 inlet and a product hydrogen gas outlet are disposed in the cathode area. The method is based on the principle of CO.sub.2 mineralization and utilization, combines the membrane electrolysis technology, facilitates spontaneous reaction by using the acidity of CO.sub.2 and the alkalinity of the reaction solution and realizes separation of the products, and converts through a membrane electrolysis apparatus the energy released by the reaction into electric energy at the same time when producing the sodium bicarbonate or sodium carbonate and outputs the electric energy. The method and device have low energy consumption, high utilization rate of raw materials and little environmental pollution, and can output electric energy while producing sodium carbonate at the same time.

A metal-air battery including: a current collector; a metal electrode including a metal and contacting the current collector; an air electrode on the metal electrode and opposite the current collector; a solid electrolyte between the metal electrode and the air electrode; a discharge product of the metal on the air electrode; wherein the metal-air battery is configured to release the discharge product.

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.

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.

The present invention is directed to a redox flow battery comprising at least one electrochemical cell in fluid communication with a balancing cell, said balancing cell comprising: a first and second half-cell chamber, wherein the first half-cell chamber comprises a first electrode in contact with a first aqueous electrolyte of the redox flow battery; and wherein the second half-cell chamber comprises a second electrode comprising a catalyst for the generation of O.sub.2; and wherein the second half-cell chamber does not contain an aqueous electrolyte.

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.

The invention is based on a fuel cell device which is provided to be operated with a natural gas, having a fuel cell unit (12) and an anode gas processor (14) arranged upstream of the fuel cell unit (12), which anode gas processor is provided to prepare the natural gas for use in the fuel cell unit (12) and which comprises a desulfurization unit (18), which is provided to desulfurize the natural gas, an oxidation unit (20), which is provided to perform partial oxidation, and a reformer unit (22), which is provided to produce at least one fuel gas. It is proposed that the fuel cell device comprise a recirculation unit (16), which is provided to supply at least a proportion of an anode waste gas from the fuel cell unit (12) to the fuel cell device (10).

One embodiment is a redox flow battery system that includes an anolyte; a catholyte; an anolyte tank configured for holding at least a portion of the anolyte; a catholyte tank configured for holding at least a portion of the catholyte; a primary redox flow battery arrangement, and a second redox flow battery arrangement. The primary and secondary redox flow battery arrangements share the anolyte and catholyte tanks and each includes a first half-cell including a first electrode in contact with the anolyte, a second half-cell including a second electrode in contact with the catholyte, a separator separating the first half-cell from the second half-cell, an anolyte pump, and a catholyte pump. The peak power delivery capacity of the secondary redox flow battery arrangement is less than the peak power delivery capacity of the primary redox flow battery arrangement.

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.