Nowadays most of us are already conscious of the different “man-made” threats which affect our environment. Poisonous substances, devastating machineries, a wide range of inconsiderate technologies and contaminating waste of a growing comfort- and consume-orientated society. Air pollution and its undesirable offspring, the “greenhouse effect” and the “ozone hole”, which currently affect divers urban centres worldwide, are just popular examples for the result of more than 100 years of negligent industrialization.
It is time to reconsider our position and function towards our environment in order to conserve and repair what rests from Earth’s natural harmony on which our species relies. In this sense, I would like to focus on a very promising technology which might contribute to a better and more pleasant world: The fuel cell!
What is a fuel cell? Fuel cells are electrochemical devices that combine hydrogen and oxygen to produce electricity, with water and heat as its derivate. A fuel cell are like a battery but it does not run down, nor does it require recharging as long as fuel (hydrogen) is supplied. The conversion of hydrogen to energy takes place without combustion, therefore the process is highly efficient, clean and quiet!
The idea behind fuel cells is quite simple. Some of us may still remember the electrolysis (splitting of water) experiment at school. In this experiment two electrodes (similar metals), which are connected to the poles (+ and -) of a source of “direct current” (battery), are introduced into a electrolyte (i.e. salt dissolved in water). The electrode, which is connected to the positive pole, is called anode. The other electrode is connected to the negative pole and is called cathode. In the salt (NaCl) solution the positively charged ions (cations: Na+) migrate to the cathode (-) and the negatively charged ions (anions: Cl-) move to the anode (+). On the electrodes the ions are discharged and are then present as neutral particles (atoms or molecules). In this form they react with the chemical environment: they precipitate on the electrode, escape upward as a gas or are involved in secondary reactions.
In our case (salt solution) chlorine (Cl-) forms gas molecules (Cl2), which rise to the surface as small bubbles. Sodium (Na+), on the other hand, is unstable in water and is immediately converted in a secondary reaction to sodium hydroxide (NaOH). For this to happen, an OH- ion must be torn from the water (H2O), leaving an H+. The H+ ions join to form hydrogen molecules, which rise at the cathode as small bubbles. The reaction products of the electrolysis of common salt solution are hence chlorine gas (Cl2) and hydrogen gas (H2).
Fuel cells work like an inverse electrolysis – it also consists of two electrodes separated by an electrolyte. In most cases, hydrogen fuel (H2) is fed into the anode of the fuel cell. Oxygen (O2 or air) enters the fuel cell at the cathode. Encouraged by a catalyst, the hydrogen splits into protons and electrons. The protons pass through the electrolyte while the electrons must take the long way around, creating a separate current that can be utilized before they return to the cathode. On the cathode the electrons are reunited with the hydrogen and oxygen to form a molecule of water.