Electrolysis of Sea Water

Abstract

In implementation of the hydrogen economy, the electrolysis of sea water as the source of hydrogen has been discussed. Two options exist for performance of this electrolysis. The first option is to subject the water to total desalinization to remove all impurities and produce essentially distilled water. This distilled water can then be subjected to electrolysis in conventional, alkaline electrolyte, electrolysis cells. The disadvantages of this approach are the capital costs of the water purification equipment and the environmental problem arising from the need to dispose of the residual salts removed during desalinization. The advantages are the ability to use developed technology.

The second option is to design electrolyzer systems capable of utilizing natural sea water to perform the electrolysis. It is probable that these systems would operate at a low power density and electrolyze only a small portion of the water in contact with electrodes. The disadvantages are new technology must be developed to solve the probable corrosion and contamination problems and undesirable electrochemical products such as chlorine. The advantages are possible lower capital costs and natural elimination of the waste brine which is only slightly enriched with salts. It may also be possible to recover economically significant quantities of the metals present in sea water that are less active electrochemically than hydrogen: silver, gold, mercury, and copper.

Preliminary data indicates that low current densities are insufficient to prevent deposits and chlorine formation and that while hydrogen can be produced at reasonable efficiency (89 percent), the overall process may not be environmentally acceptable for very large-scale applications