High Power-Density WO3-x-Grafted Corannulene-Modified graphene nanostructures for Micro-Supercapacitors

The emergence of nanotechnology and development of new methods of nanoengineering novel materials have enabled to design supercapacitors, new devices filling the niche between the high energy-density electrochem-ical batteries and the high power-density dry capacitors. Thanks to the nanoengineering, new devices combin-ing the unique properties of electrochemical double-layer capacitance with high storage capability of pseudocapacitance materials could became a reality. A special niche in these applications is for micro-superca-pacitors, which can drive miniature sensors and implantable biodevices, requiring fast remote charging and high energy density packed in a small volume. In this work, the micro-supercapacitors were fabricated using WO3-x nanoparticles immobilized on rGO nanosheets to increase the carbon nanoform double-layer capacitance by adding very high pseudocapacitance of WO3-x. To improve the attachment of WO3 to the carbon support and enhance the graphene matrix conductance, grafting of WO3 nuclei onto the GO defect sites was employed by electrochemical processing and nanoparticle growth, followed by the electroreduction of unprotected oxida-tion sites of GO to form a highly-conductive reduced graphene oxide (rGO) support. Further protection of rGO nanosheets from stacking interactions was also necessary. It was achieved by modifying graphene sheets with corannulene (CORA) which is a C20H10 polyaromatic hydrocarbon (PAH) molecule forming a cup (or: Bucky bowl) structure. We have found that corannulene can efficiently separate the rGO nanosheets in more hydrophobic locations of rGO where WO3-x nanoforms are missing. The chemical structure, morphology, and electrochemical properties of hybrid materials used for designing the micro-supercapacitor devices were characterized by Raman spectroscopy (RS), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infra-red spectroscopy (FTIR), electrochemical quartz crystal nanogravimetry (EQCN), cyclic voltammetry (CV), as well as potential-pulse and current-pulse charging/dis-charging characteristics. The supercapacitor properties of the proposed WO3,CORA/rGO devices were favor-able compared with those for mono plate graphene (MPG) and laser-induced graphene (LIG) MSCs.