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 nitrogen battery of the present disclosure includes a positive electrode that uses nitrogen as a positive electrode active material, a negative electrode, and an ion conducting medium that contains a silane compound and conducts alkali metal ions.

A redox device of a metal-air flow battery includes a container, a rod inserted into and electrically insulated from the container, a net connected to and surrounding the rod, a power supply, and an ultrasonic module. The container, the rod, and the net are electrically conductive, respectively. The net moves away from the rod gradually in a spiral manner. The container receives an electrolyte solution containing a product originated from the metal-air flow battery. The net is immersed in the electrolyte solution. The power supply is electrically connected to the container, the rod, and the net to form an electric loop via the electrolyte solution. The power supply provides a pulse current to the electric loop to electrochemically deposit metal from the electrolyte solution on the net. The ultrasonic module provides vibrations to the container to shake off metal from the net and suspend the metal in the electrolyte solution.

A method for preparation of electrolyte for a redox flow battery includes reducing chromium ore using a carbon source to convert the chromium ore to an iron/chromium alloy with carbon particles; dissolving the iron/chromium alloy with carbon particles in sulfuric acid to form a first solution; adding calcium chloride or barium chloride to the first solution to produce a second solution including FeCl.sub.3 and CrCl.sub.3; and adding an acid to the second solution to form the electrolyte. Other methods can be used for preparing an electrolyte from chromium waste material.

A method and a system of generating electrical power or hydrogen from thermal energy is disclosed. The method includes separating, by a selectively permeable membrane, a first saline solution from a second saline solution, receiving, by the first saline solution and/or the second saline solution, thermal energy from a heat source, and mixing the first saline solution and the second saline solution in a controlled manner, capturing at least some salinity-gradient energy as electrical power as the salinity difference between the first saline solution and the second saline solution decreases. The method further includes transferring, by a heat pump, thermal energy from the first saline solution to the second saline solution, causing the salinity difference between the first saline solution and the second saline solution to increase. The method and system may include a regeneration process, such as membrane distillation, forward osmosis, electrodialysis, salt evaporation and/or salt decomposition.

A method and system of generating electrical power or hydrogen from thermal energy is disclosed. The method includes separating, by a selectively permeable membrane, a first saline solution from a second saline solution, receiving, by the first saline solution and/or the second saline solution, thermal energy from a heat source, and mixing the first saline solution and the second saline solution in a controlled manner, capturing at least some salinity-gradient energy as electrical power as the salinity difference between the first saline solution and the second saline solution decreases. The method further includes transferring, by a heat pump, thermal energy from the first saline solution to the second saline solution, causing the salinity difference between the first saline solution and the second saline solution to increase. The method may include a process of membrane distillation, forward osmosis, evaporation, electrodialysis, and/or salt decomposition for further energy efficiency and power generation.

The present invention provides a method for removing pentavalent antimony contaminants in water without adding a DC power supply and also provides a fuel cell capable of removing the pentavalent antimony contaminants in water by utilizing self-generated electric energy. A technical solution of the present invention is as follows: waste water is pumped into a reactor for reaction after a pH value of the waste water containing the pentavalent antimony contaminants adjusted to 3-6.5; the inside of a reactor is an anaerobic environment; and an iron anode is arranged in the reactor, a through hole is formed in a side wall of the reactor, a cathode for reducing oxygen by electrons and protons sealed and inlaid in the through hole, and a resistor is connected between the iron anode and the cathode in series. The present invention is suitable for a water treatment technology.

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.

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.

This invention provides a redox fuel cell comprising an anode and a cathode separated by an ion selective polymer electrolyte membrane; means for supplying a fuel to the anode region of the cell; means for supplying an oxidant to the cathode region of the cell; means for providing an electrical circuit between the anode and the cathode; a non-volatile catholyte solution flowing in fluid communication with the cathode, the catholyte solution comprising a polyoxometallate redox couple being at least partially reduced at the cathode in operation of the cell, and at least partially re-generated by reaction with the oxidant after such reduction at the cathode, the catholyte solution further comprising vanadium species that result from the speciation of the polyoxometallate at an elevated temperature and/or pressure.