What does a wider peak separation indicate about the redox couple?

A wider peak separation in a redox couple typically indicates significant changes in kinetics. This is because peak separation is influenced by the rate of the redox reaction. As the kinetics of the electron transfer become slower, or if there are substantial energy barriers to the reaction, the peak heights will rise and the peak separation will widen. In contrast, if the reaction is highly reversible, the peaks would be expected to be closer together, reflecting that the electron transfer process proceeds with relatively low energy barriers and rapid kinetics.

Other factors, such as concentration and reversibility, might also affect peak characteristics, but a wider peak separation is most directly tied to how slow or fast the electron transfer is occurring. Hence, a significant increase in peak separation serves as an indicator of changes in the kinetics of the electron transfer reactions for the redox couple in question.