External electric current application

Autocatalytic deposition is the most widely used type of plating of metals from aqueous solutions, without an application of the external electrical current or potential. This process is frequently called electroless or chemical deposition, although, these terms do not precisely describe the autocatalytic deposition. 

Opposite from galvanic cell is an electrolytic cell where external electric current is applied in order to induce chemical changes within a cell a textbook example is a cell used to electrolyze hquid water into gaseous H2 and O2. Electrolytic cells have a number of important industrial applications and are the subject of technical-engineering electrochemistry. 

During experiments to find alternate ways of doping polymers, a graduate student of Professor MacDiarmid discovered one of the first practical applications of polyacetylene. He placed two strips of polyacetylene into a solution of doping ions and connected the strips to an electric current. The hope was that the ions would penetrate the polymer under the action of the external electric current. But after the student removed the external electric current, the polymer strips retained a charge and acted as a battery. Since then an all-plastic battery has been developed. Its electrodes are made of conductive polymers, and the electrolyte is a polymer gel. 

The EMD studies are performed without any external electric field. The applicability of the EMD results to useful situations is based on the validity of the Nemst-Planck equation, Eq. (10). From Eq. (10), the current can be computed from the diffusion coefficient obtained from EMD simulations. It is well known that Eq. (10) is valid only for a dilute concentration of ions, in the absence of significant ion-ion interactions, and a macroscopic theory can apply. Intuitively, the Nemst-Planck theory can be expected to fail when there is a significant confinement effect or ion-wall interaction and at high electric... 

The term electromembrane process is used to describe an entire family of processes that can be quite different in their basic concept and their application. However, they are all based on the same principle, which is the coupling of mass transport with an electrical current through an ion permselective membrane. Electromembrane processes can conveniently be divided into three types (1) Electromembrane separation processes that are used to remove ionic components such as salts or acids and bases from electrolyte solutions due to an externally applied electrical potential gradient. (2) Electromembrane synthesis processes that are used to produce certain compounds such as NaOH, and Cl2 from NaCL due to an externally applied electrical potential and an electrochemical electrode reaction. (3) Eletectromembrane energy conversion processes that are to convert chemical into electrical energy, as in the H2/02 fuel cell. 

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