Electrochemistry occurs – how could it be otherwise – at the interface between electricity and chemistry. Consider phenomena that occur when chemical reactions generate an electric current, or when you can use electricity to modify chemical compounds or materials. For example, chemical reactions in batteries and fuel cells generate electricity. Conversely, electrolysers allow hydrogen gas to be generated by applying an electrical voltage over water, with oxygen as a by-product. Corrosion, on the other hand, is an undesirable electrochemical process in which a metal surface is attacked, usually in the presence of oxygen and water.
Electrochemistry is also found in the living nature around us. Electrochemical reactions play a key role in photosynthesis, a biological process in plants where water and carbon dioxide are converted into carbohydrates and oxygen under the influence of sunlight. Electrons are required for the formation of the biological energy carrier NADPH.
Non-destructive analysis techniques such as impedance spectroscopy are available to understand electrochemical processes. This involves applying a small alternating voltage over an object and measuring the current through the object. The frequency-dependent ratio of these two tells us something about the electrical/electrochemical transport in this object, without needing to open the ‘black box’.