Possible Paths for the Oxygen-Evolution Reaction

Oxygen evolution is a more complex reaction than hydrogen evolution, involving the transfer of four electrons. The overall reaction in alkaline solution is 

40H-- 02 + 4eM + 2H20 whereas in neutral or acid solutions it is 6H20 02+4H30+ +4ew 

Let us write a mechanism (one of many possible) for this reaction. The first step would be charge transfer 

This could be followed by a further charge-transfer step, such as 

Followed, for example, by atom-atom recombination, to yield 

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