Addition of multiwalled carbon nanotube and graphene nanosheet in cobalt oxide film for enhancement of capacitance in electrochemical capacitors

In order to enhance the capacitance of electrochemical capacitors, multiwalled carbon nanotubes (MWCNTs) and graphene nanosheets (GNS) were added to cobalt oxide (Co3O4) paste. The composite film based on Co3O4/MWCNT/GNS (95:4:1 wt%) exhibited a capacitance of 294 F/g while the capacitance of Co3O4/MWCNT (95:5 wt%) and pure Co3O4 film is 205 and 163 F/g, respectively. The enhanced capacitance of Co3O4/MWCNT/GNS composite film was attributed to the electrochemical contributions of the Co3O4 nanoparticle attached to the GNS as well as their significantly increased specific surface areas by MWCNTs. Furthermore, the composite films showed faradaic redox capacitive behavior to double-layer capacitive behavior due to the different nanostructures of the composites.

► Enhanced capacitance in CNT and graphene (GNS) with Co3O4 composites films.
► Co3O4/MWCNT/GNS composite film shows a capacitance of 294 F/g.
► This is higher capacitance than those of Co3O4/MWCNT and pure Co3O4 composites.
► This is due to the electrochemical contributions of the Co3O4 attached to the GNS.
► This is also due to significantly increased specific surface areas by MWCNTs.