Charge Transport and Electrical Potential Equation

The relationship of charge transport and electrical potential field is analogous to the solution of heat transfer on the basis of the temperature field. In 

At the anode electrode-electrolyte interface, there is an increase in the electrical potential owing to the formation and accumulation of charge species in the electrical double layer that spans over the anode-electrolyte interface. 

Accumulation of charges in electric double layer and electrical potential, (a) Comprehensive double layer model, (b) Simplified double layer model. 

The elecfrical double layer acts like a capacitor with an increase in electrical potential over a very small thickness of the order of nanometers at the anode-electrolyte interface. Similarly, at the cathode-electrolyte interface, there is again an increase in electrical potential because of the formation and accumulation of charged ions over the electrical double layer. This is followed by the drop in electrical potential over the thickness of the cathode electrode because of the resistance of electron transport. 

As we can see, the electrical potential decreases over the thicknesses of the anode and cathode electrodes owing to the ohmic resistance of the electrode gas diffusion layers to electron transport. These losses are referred to as the anode and cathode ohmic aoerpotentials Tiohm.a lohm.c/ respectively. 

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