Large Batteries for Electric Power Storage

Because vanadium ions exist in four different oxidation states (as V2+, V3+, V02+ and V02+) in aqueous solution, redox couples can be formed by all vanadium ions. The emf of a vanadium redox battery is 1.4 V and the electrode kinetics are higher than those of the Fe-Cr battery. Also, the energy density of the battery can be increased due to the high solubility of vanadium salts.257 In the battery, vanadium sulfate solution is used, 

The H2-02 fuel cell is, in general, prepared by pressing and heating a mixture 

Water management is important in the optimization of the cell operation, affecting both internal resistance and cathode polarization losses of the cell.273 Because protons (H30+) permeate through the membrane together with hydrated water and the fuel cell is generally operated at 80 °C, water should be supplied to the anode side. Fuel (hydrogen) and oxygen (air) also should be humidified to keep the membrane wet. 

Because most hydrogen gas for the cell is produced by reforming hydrocarbons, a trace amount of CO is contained in the hydrogen gas after purification. The CO bonds to the Pt electrode catalyst and makes it inactive below 150 °C.274 The allowable amount of CO in the feed H2 gas is reported to be below 10 ppm.275 Electrode catalysts that tolerate CO have been under development, e.g. Pt-Ru,276 Pt alloys.277 

To reform hydrocarbons to hydrogen gas, a reforming apparatus (reformer) is necessary. This makes the fuel cell process complicated and large. This is not 

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