Redox conductors, charge transport

While the case is far from closed, the bulk of the currently available evidence suggests that the rate of this charge-transport process is controlled by ionic diffusion in the polymer phase (14-18). Because diffusional mass-transport plays a role in many electrochemical experiments, it should be possible to assess the rate of the conductor/insulator switching reaction using an electrochemical method. For example, large amplitude electrochemical methods have been used to assess the rates of charge-transport in redox polymer films on electrode surfaces (19-24). 

For every electron passed upward along the conductor, a corresponding amount of reduced species must move away from, or oxidised species move toward, the conductor. This continual migration of redox-active species must be coupled with redox reactions in order to transfer charge. If redox equipotential lines are totally static, the production of reduced species at the conductor must be accompanied by the simultaneous consumption of reduced species somewhere between bedrock and the water table. This would result in the almost instantaneous transfer of electrical current despite the much longer time required for mass transport of reduced species to the ground surface (see discussion on ion mobility, below). 

Between the electrodes, the solution behaves as an ionic conductor with a resistance, known as the ohmic solution resistance. At the electrode-solution interface, some of the ions are used to adjust the ionic atmosphere until the charge balance between the electrode surface and the solution is reached. Electrically, this is equivalent to the charge or discharge of a capacitor with capacitance Q, known as the double layer capacitance. Simultaneously, i.e. in parallel, redox species undergo an electron transfer with the electrode this yields the faradaic current whose magnitude reflects the rate of arrival of the reactants (the rate of mass transport) and the rate of the electron transfer process. Electrically, this is equivalent to two resistors in series one for the kinetics of the electron... 

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