  The ability to tune charge storage properties of graphene oxide (GO) is of
utmost importance for energy conversion applications. Here we show that
electrochemical reduction of GO is highly sensitive to the cations present in
the solution. GO is reduced at lower potential in alkali metal chloride
solutions than in alkaline earth metal chlorides. During the reduction,
capacitance of GO increases from 10 to 70 times. Maximum capacitances of
reduced GO are between 65 and 130 F g-1, depending on the electrolyte and the
presence of conductive additive. We propose that different interactions of
cations with oxygen functional groups of GO during the reduction are
responsible for the observed effect.
