8.4 Ethanol Fuel Cells
Ethanol fuel cells are a relatively new type of fuel cell. Hydrogen-based fuel cells have been around since the early space-age, where they were vital parts of many early spacecraft such as the Gemini and Apollo missions during the 1960s. Fuel cells using methanol are even newer, having been developed to take advantage of the physical and chemical properties of methanol. Ethanol fuel cells are beingdeveloped to replace methanol fuel cells, since methanol is toxic. 
An ethanol fuel cell works using the same principles as a hydrogen fuel cell. Using liquid ethanol in place of hydrogen gas, the fuel reacts and produces an electric current. The ethanol combines with water to produce carbon dioxide. Protons travel through a proton exchange membrane (PEM) which causes electric current to flow through a wire from an anode to a cathode.
Whether it’s burning in an internal combustion engine or being used in a fuel cell, ethanol is being oxidized, which can result in different products. When the reaction is most efficient, the only products are carbon dioxide (CO2) and water (H2O). A less efficient reaction results in acetic acid (CH3COOH, shown at left) which is, as its name might suggest, an acid. So the more efficient the fuel cell’s reaction, the less acidic its product will be.
The two reactions are below:
|C2H5OH + 3O2 → 3H2O + 2CO2
C2H5OH + O2 → CH3OOH + H2O