Overpotential

<p>In <a href="/facts/Electrochemistry/C0RUWpBH">electrochemistry</a>, overpotential is the <a href="/facts/Electric_potential/Nmqm6hm5">potential</a> difference (<a href="/facts/Voltage/EN2po6N2">voltage</a>) between a <a href="/facts/Half-reaction/4pDKxYa6">half-reaction</a>'s thermodynamically determined <a href="/facts/Reduction_potential/PqpNUgSl">reduction potential</a> and the potential at which the <a href="/facts/Redox/Pyd5RVcj">redox</a> event is experimentally observed. The term is directly related to a cell's <i>voltage efficiency</i>.  In an <a href="/facts/Electrolytic_cell/Cn3U4dSp">electrolytic cell</a> the existence of overpotential implies that the cell requires more energy than thermodynamically expected to drive a reaction. In a <a href="/facts/Galvanic_cell/a4V7CQC8">galvanic cell</a> the existence of overpotential means less energy is recovered than <a href="/facts/Thermodynamics/q4hIx3yP">thermodynamics</a> predicts. In each case the extra/missing energy is lost as <a href="/facts/Heat/FjDGssCs">heat</a>. The quantity of overpotential is specific to each cell design and varies across cells and operational conditions, even for the same reaction. Overpotential is experimentally determined by measuring the potential at which a given <a href="/facts/Current_density/IlUKSe2B">current density</a> (typically small) is achieved.
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Overpotential open-in-new

Overpotential