Controlled Spacing of Few-Layer Graphene Sheets Using Molecular Spacers: Capacitance That Scales with Sheet Number

Preventing graphene sheet aggregation while retaining full accessibility to the total graphene surface area is key to optimizing the performance of graphene supercapacitors. Spacer species can be added to graphene assemblies to prevent aggregation, but typical methodologies do not allow accurate assessment of the extent of sheet separation nor whether spacing groups block some of the surface area. In this work we have grafted sub-10 nm films of aryl spacer groups to chemical vapor deposition-grown few layer graphene (FLG) sheets using aryldiazonium salts. Using a layer-by-layer strategy that relies on individually handling each FLG sheet, 3-sheet stacks were prepared and electrochemically interrogated. By comparing the differential and integral capacitances of modified and unmodified single FLG sheets and 3-sheet stacks, we show that in the 3-sheet stacks of modified FLG, the grafted spacer groups fully separate the FLG sheets and allow complete double layer formation at all FLG-solution interfaces. The stacks of modified FLG show no decrease in double layer capacitance over 20 000 charge–discharge cycles, indicating that full separation of the FLG sheets is maintained and confirming that these grafted spacer layers offer a practical solution to the problems of graphene aggregation.