In order to appreciate the electrochemistry of S-doped graphene for energy storage, it is advisable to realize the interaction between the doped sulphur atoms and the ions present in the electrolyte. It has been reported that both sulfoxide and sulphone enhance the pseudocapacitance of S-doped graphene by involving the faradaic interactions with ions from the electrolyte. Initially, the sulphone groups are reduced to sulfoxide and the sulfoxide groups are further reduced to sulphenic acid . The proposed electrochemical mechanism of Sdoped graphene in aqueous electrolytes is depicted as follows: