Physicochemical characterisation of graphene oxide and reduced graphene oxide composites for electrochemical capacitors

The aim was to prepare mesoporous composites of graphene oxide (GO) and titania with improved physicochemical properties for use as electrodes in electrochemical double layer capacitors (EDLCs). This was done by using a known amount of titania (5, 10, 20 and 40 wt%) to synthesise graphene oxide-titania (GOTi), reduced graphene oxide-titania (RGOTi) and nanocrystalline cellulose (NCC) reduced graphene oxide-titania (CRGTi) composites by sol–gel method. Titania positively impacted the exfoliation of GO sheets but excess amounts culminated in large titania agglomerates in the composites. The carbon-oxygen-titanium interactions, facilitated by oxygen moieties, were strongest in the GOTi composites. The reduction of GOTi, to form RGOTi, enhanced the surface area from 136.89 to 434.24 m² g^− 1 for the 5 wt% titania composites. The RGOTi composites were more defective than the GOTi ones with an I_D/I_G ratio of 1.13 and 0.88, respectively, at 40 wt% titania. Inclusion of NCC in the synthesis of RGOTi composites enhanced the surface areas relative to those of both GOTi and RGOTi at 10–40 wt% titania. The 5 wt% titania RGOTi composite displayed the best EDLC quality with the highest specific capacitance of 45 F g^− 1 in sodium sulfate electrolyte.