Inorganic and Applied Chemistry

Download free books at BookBooN.com

Inorganic and Applied Chemistry

The following half cell reaction takes place at the anode:

2H 2 (g) + O 2 (g)  2 H 2 O(l)

whereas the following half cell reaction takes place at the cathode:

O 2 (g) + 2 H 2 O(l) + 4 e-  4 OH-(aq)

In recent years the research in fuel cells has increased significantly. One of the reasons for this is that the

reactions in fuel cells do not involve environmentally dangerous species. What is of further importance is

that fuel cells involve reactions where CO 2 is not produced.

6.6 Corrosion

Well-known phenomena as corrosion of e.g. cobber roofs are closely related to the electrochemistry. Because

corroded metal as e.g. iron looses its strength corrosion chemistry has great practical importance. Metals are

especially exposed to corrosion as metals are easily oxidised. From tables of standard reduction potentials

one will see that with the exception of noble metals as e.g. gold the standard reduction potentials of common

metals are lower than for oxygen. This means that the oxidation of most metals is a spontaneous reaction

even though not metals are equally oxidised in the presence of oxygen.

Even though many metals ought to be corrosive in the presence of oxygen it is actually seldom the case. This

is caused by the fact that many metals build a small oxide layer on the outside of the metal that help to

prevent corrosion. This we will look into in the following example.

Electrochemistry