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Concept
Linear sweep voltammetry
Résumé
In analytical chemistry, linear sweep voltammetry is a method of voltammetry where the current at a working electrode is measured while the potential between the working electrode and a reference electrode is swept linearly in time. Oxidation or reduction of species is registered as a peak or trough in the current signal at the potential at which the species begins to be oxidized or reduced.
The experimental setup for linear sweep voltammetry utilizes a potentiostat and a three-electrode setup to deliver a potential to a solution and monitor its change in current. The three-electrode setup consists of a working electrode, an auxiliary electrode, and a reference electrode. The potentiostat delivers the potentials through the three-electrode setup. A potential, E, is delivered through the working electrode. The slope of the potential vs. time graph is called the scan rate and can range from mV/s to 1,000,000 V/s.
The working electrode is one of the electrodes at which the oxidation/reduction reactions occur—the processes that occur at this electrode are the ones being monitored. The auxiliary electrode (or counter electrode) is the one at which a process opposite from the one taking place at the working electrode occurs. The processes at this electrode are not monitored. The equation below gives an example of a reduction occurring at the surface of the working electrode. Es is the reduction potential of A (if the electrolyte and the electrode are in their standard conditions, then this potential is a standard reduction potential). As E approaches Es, the current on the surface increases, and when E = Es, the concentration of A equals that of the oxidized/reduced A at the surface ([A] = [A−]). As the molecules on the surface of the working electrode are oxidized/reduced, they move away from the surface and new molecules come into contact with the surface of the working electrode. The flow of electrons into or out of the electrode causes the current. The current is a direct measure of the rate at which electrons are being exchanged through the electrode-electrolyte interface.
Source officielle
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