Supporting electrolyte

A supporting electrolyte, in electrochemistry, according to an IUPAC definition, is an electrolyte containing chemical species that are not electroactive (within the range of potentials used) and which has an ionic strength and conductivity much larger than those due to the electroactive species added to the electrolyte. Supporting electrolyte is also sometimes referred to as background electrolyte, inert electrolyte, or inactive electrolyte.

Supporting electrolytes are widely used in electrochemical measurements when control of electrode potentials is required. This is done to increase the conductivity of the solution (to practically eliminate the so-called IR drop, or ohmic potential drop from Ohm's law: V = IR), to eliminate the transport of electroactive species by ionmigration in the electric field, to maintain constant ionic strength, to maintain constant pH, etc. Supporting electrolytes also play a critical role in defining the structure of the electrical double layer at the electrode-electrolyte interface, which can influence electron transfer kinetics and interfacial capacitance. Common supporting electrolytes include tetraalkylammonium salts (e.g., tetrabutylammonium hexafluorophosphate) in nonaqueous systems and alkali metal salts (e.g., potassium chloride or sodium sulfate) in aqueous media, chosen for their high solubility, chemical inertness, and wide electrochemical window.