... but, if there's a hydrogen ION flow (as distinct from an...

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.. but, if there's a hydrogen ION flow (as distinct from an electron flow), then the dissociation of the hydrogen from the water molecule MUST result in the production of free oxygen. Is the graphene oxidising further... until it can't absorb any more oxygen, at which point the "battery" stops working... or is oxygen being given off into the atmosphere? Or is the google article not quite correct in asserting that there is an ion flow, when in fact there is an electron flow? Also, come to think of it, where does the free hydrogen (ionised or otherwise) end up eventually, also?

Separating water into hydrogen and oxygen is normally an endothermic reaction requiring the INPUT of electricity. It seems highly unlikely that the mere presence of graphene (or graphene oxide) is going to spontaneously reverse this process and produce electricity as a result of the hydrogen/oxygen dissociation.

It's time for me to stop wondering and read the article, the link to which you have graciously supplied.

P.