How does a fuel cell function?

A fuel cell generates electricity through a chemical reaction between a fuel source and an oxidant.

Fuel cells function by converting chemical energy into electrical energy through a series of reactions. The process begins with a fuel source, typically hydrogen, and an oxidant, usually oxygen, being introduced to the cell. These two elements are kept separate, each being introduced to a different side of the cell. The fuel cell consists of two electrodes, an anode (negative) and a cathode (positive), separated by an electrolyte.

At the anode, a catalyst encourages the fuel to undergo oxidation, a process that causes the fuel to split into positive ions and negative electrons. In the case of hydrogen fuel, this results in hydrogen ions (protons) and electrons. The electrolyte, a substance specifically designed to allow positive ions to pass through while blocking electrons, forces these electrons to travel along an external circuit to reach the cathode. This movement of electrons creates an electric current that can be harnessed to do work, such as powering a motor or lighting a bulb.

Meanwhile, at the cathode, the oxidant is reduced by gaining the electrons that have travelled through the external circuit. In the case of oxygen, it combines with the electrons and the hydrogen ions that have passed through the electrolyte to form water, which is the only by-product of a hydrogen-oxygen fuel cell.

The overall reaction in a hydrogen-oxygen fuel cell is the combination of hydrogen and oxygen to form water, a process that releases energy. However, instead of this energy being released as heat and light, as in a typical combustion reaction, it is harnessed as electrical energy. This makes fuel cells a highly efficient and environmentally friendly method of generating electricity, as they can operate at higher efficiencies than traditional combustion engines and their only by-product is water.

The key to the operation of a fuel cell is the electrolyte. Different types of fuel cells use different electrolytes, and the choice of electrolyte can affect the efficiency, operating temperature, and fuel compatibility of the cell. Despite these differences, all fuel cells operate on the same basic principle of separating a fuel source and an oxidant to generate an electric current.