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A fuel cell is an electrochemical cell that reacts hydrogen fuel with oxygen or another oxidizing agent, to convert chemical energy to electricity. Fuel cells are different from batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy comes from ...
Gas-liquid separation membranes allow gas but not liquid to pass through. Flowing a solution inside a gas-liquid separation membrane and evacuating outside makes the dissolved gas go out through the membrane. This method has the advantage of being able to prevent redissolution of the gas, so it is used to produce very pure solvents.
The so-called gas distribution layer is located in the middle of the electrode. With only a small gas pressure, the electrolyte is displaced from this pore system. A small flow resistance ensures that the gas can freely flow inside the electrode. At a slightly higher gas pressure the electrolyte in the pore system is restricted to the work layer.
A positive cell potential gives a negative change in Gibbs free energy. This is consistent with the cell production of an electric current from the cathode to the anode through the external circuit. If the current is driven in the opposite direction by imposing an external potential, then work is done on the cell to drive electrolysis.
The system can be flushed with an inert gas to reduce the concentration of oxygen so that when the flammable gas is admitted, an ignitable mixture cannot form. In NFPA 56, [1] this is known as purge-into-service. In combustion engineering terms, the admission of inert gas dilutes the oxygen below the limiting oxygen concentration.
Chemical reactions are determined by the laws of thermodynamics. Reactions can proceed by themselves if they are exergonic, that is if they release free energy. The associated free energy change of the reaction is composed of the changes of two different thermodynamic quantities, enthalpy and entropy: [17]
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The sodium–mercury amalgam flows to the center cell, where it reacts with water to produce sodium hydroxide and regenerate the mercury. Mercury cell electrolysis, also known as the Castner–Kellner process, was the first method used at the end of the nineteenth century to produce chlorine on an industrial scale.