Oxygen reduction reaction organic impurities

The equilibrium potential observed is depicted in the Figure 1 where we illustrate the potential-current behavior for the cathodic reaction (the oxygen reduction) coupled with a possible unspecified anodic oxidation of organic impurities. At electrochemical equilibrium i. = i and no net current flows in the circuit,... 

Other competing cathodic reactions can occur, and these cause an increase in zinc usage which adversely affects the process efficiency. Examples of these are hydrogen gas evolution or oxygen reduction. Other metal cations or impurities that load into the organic may also be reduced depending on the processing parameters and the electrochemical nature of the impurities. 

Various anodic reactions have been proposed (1) oxidation of impurities (mostly organic) from the solution (2) oxidation of H2O2 accumulated in solution as a result of the two-electron oxygen reduction (3) the formation of surface oxides and (4) platinum anodic dissolution/ " ... 

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