Electrochemical flow oxygen separator

Fig. 5. Exploded view of an ion-exchange membrane electrochemical oxygen separator. Oxygen removal characteristics of the flow-through type oxygen removal system are shown. Air cathode area = 100 cm2, water temperature = 40 °C.

Fuel cells are electrochemical systems that convert the energy of a fuel directly into electric power. The design of a fuel cell is based on the key components an anode, to which the fuel is supplied a cathode, to which the oxidant is supplied and an electrolyte, which permits the flow of ions (but no electrons and reactants) from anode to cathode. The net chemical reaction is exactly the same as if the fuel was burned, but by spatially separating the reactants, the fuel cell intercepts the stream of electrons that spontaneously flow from the reducer (fuel) to the oxidant (oxygen) and diverts it for use in an external circuit. 

Kiipper et al. carried out a methoxylation reaction of 4-methoxytoluene in an electrochemical microreactor in which a glass carbon anode and a stainless steel cathode were separated by a microchannel foil 25 pm thick [54], The chemical resistance of the microchannel foils was very important because of the evolution of hydrogen and oxygen gases and the strong pH shifts during electrolysis. PEEK was found to be the most robust material. They also observed that selectivity of the oxidation of 4-methoxytoluene in acidified methanolic solution (pH 1, sulfuric acid) was influenced by the current density and flow rate. 

A fuel cell, similar in some respects to an electrolytic cell or battery, is a device in which a fuel is oxidized electrochemically to produce electric power. It has the characteristics of a battery in that it consists of two electrodes, separated by an electrolyte. However, the reactants are not stored in tlie cell, but are fed to it continuously, and the products of reaction are continuously withdrawn. The fuel cell is thus not given an initial electric charge, and in operation it does not lose electric charge. It operates as a continuous-flow system as long as fuel and oxygen are supplied, and produces a steady electric current. 

The overpotentials at the anode qAnode (oxygen overpotential) and cathode qcathode (hydrogen overpotential), also referred to as charge transfer overpotentials, result from the inhibition of electron transport in the separate electrochemical reactions (see Fig. 11.2). In order for current to flow through the electrolysis cell, the resistance polarization must also be overcome. It is caused by the ohmic resistance of the ceU (electrolytes, separator and electrodes). The ohmic voltage drop can be calculated from the current density i in A cm and the surface-specific resistance R of the ceU in Q cm. ... 

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