Mixed potential theory
Mixed potential theory is a theory used in electrochemistry that relates the potentials and currents from differing constituents to come up with a 'weighted' potential at zero net current. In other words, it is an electrode potential resulting from a simultaneous action of more than a single redox couple, while the net electrode current is zero.
IUPAC definition
According to the IUPAC definition[1], mixed potential is the potential of an electrode (against a suitable reference electrode, often the standard hydrogen electrode) when appreciable fraction to the anodic or cathodic current arises from species of two or more different redox couples, but when the total current on the electrode is zero.