New aspects of enhancing the graphene capacitance by defects in aqueous electrolytes and ionic liquids

The influence of internal and external defects in graphene on the capacitance of the graphene/electrolyte interface was explored using Density Functional Theory (DFT) calculations. Aqueous solutions and ionic liquids were considered as electrolyte. The results indicate that in aqueous solutions the intrinsic defects, such as mono- and divacancies, enhance the integral capacitance more effectively than external ones, such as nitrogen impurity and oxygen functional groups, used in practice. On the other hand, the strategy of increasing the integral capacitance by creating defects in graphene is ineffective for ionic liquids with an electrochemical window larger than 2 V.