Why do some of the fuel cell's positive pass into the carbon dioxide?
In the internal circuit (electrolyte solution), the cation (positively charged) moves toward the positive electrode, and the anion (negatively charged) moves toward the negative electrode. This formed a continuous flow of charge, the electrical trend of the balance of the closed circuit.
In the external circuit (outside the electrolyte solution), the electron (negative charge) from the negative through the wire (including ammeter and other appliances) to the positive, so that the negative positive trend, positive positive negative trend.
Adjust the reaction rate, control the stability of the electrolyte solution, extend the use of time.