Electro-Chem-Technic

Mini Fuel Cell

A remarkable small fuel cell, designed for demonstrating and explaining fuel cells, and for a wide range of chemistry experiments. The cell can be used with a range of fuels, such as methanol or ethanol. With sodium borohydride as the fuel its power is very impressive.

A very important feature of our mini fuel cell is that a very wide range of fuels can be used, and no hydrogen is needed. It is very easy to use – indeed it has been specifically designed for use by children and students. When using methanol or ethanol as the fuel it produces enough current to show the principle of fuel cell operation. If, NaBH₄ (sodium tetrahydridoborate) is used as the fuel, then much greater power is obtained, and the performance exceeds similar size PEM fuel cells. For its size, it is very powerful, and it will easily drive small electric motors. Through our DC/DC converter it can drive small radios, tape players and the like.

The mini fuel cell is very simple and easy to use. It consists of two components, a red cathode, and a beaker-like anode. These are shown, partly separated, below.

An electrolyte connects the two electrodes. The electrolyte is about 65 cm³ of potassium hydroxide solution. The concentration of the KOH should be 1M, but this is not critical, and 4M can be used if a higher performance is required.

The fuel is mixed with the electrolyte. The cathode is then inserted into the beaker-like anode, and the fuel cell is set up, as in the diagram below. (Full instructions are supplied)

The best performance is obtained using NaBH₄ (sodium tetrahydridoborate). This is not a well-known chemical, but is not particularly expensive or hazardous. We sell small quantities of the fuel for a few dollars, and this is enough for well over 100 hours use! From its formula, it can be seen that it contains four atoms of hydrogen per molecule, which makes it a very good and convenient "hydrogen store". Using this fuel the performance of this very lost-cost fuel cell matches that of any other low temperature, ambient pressure, fuel cell, including any PEM fuel cell.

The cell can be used with other fuels, a very wide range of fuels. These include:-

• Methanol CH₃OH, is more readily available, and gives enough current to show the principle of a fuel cell.
• Methanal (formaldehyde) or methanoic (formic) acid.
• Ethanol C₂H₅OH
• Any ethanol containing beverage!
• Almost any alcohol, or alcohol containing fluid, such as automobile windscreen washer fluid.

The performance of the cell varies with temperature and other factors, but typical indicative figures are:-

Clearly the performance with NaBH₄ is vastly superior, but nevertheless the liquid fuels, which all give similar performance, do give enough current and voltage to illustrate fuel cell operation, and are usually more readily available. Only tiny quantities of NaBH₄ are used, and it is not expensive. Typically just 20 mg (0.02 cm³) will run the cell for one hour!