Abstract
In this dissertation, graphene based nanostructures including graphene aerogels (GAs), graphene quantum dots (GQDs), and 3D porous graphene (StG) are produced and applied in supercapacitors, dye-sensitized solar cells (DSSCs), and hydrogen production through photocatalytic water splitting. For supercapacitor applications, MnO2 electrodeposited on GAs are used as the electrode for pseudocapacitors. The 3D structural advantages of GAs made possible the high mass loading of the active material, manganese oxide, large amounts of electroactive surfaces for the superficial redox events, fast mass transfer within the porous structure, and well-connected conductive paths for the involved charge transport. Furthermore, 3D porous graphene nanostructure (StG) was synthesized by a simple, fast, and scalable mix-and-heat process. StG was used as the electrode material to fabricate flexible, gel-type symmetric supercapacitors of outstanding capacitive performances and applicable in a wide temperature range environment. For DSSC applications, GQDs were derived from carbon black through one fast microwave-assisted oxidative cleavage process and thus decorated mesoporous carbon aerogels (GQD/CA) are used as the counter electrode. The GQD/CA composite thus proves to be an inexpensive, efficient, and stable alternative to Pt as the counter electrode material for DSSCs. Finally, a cocktail strategy to design composite semiconductor photocatalysts for p-Cu2S/n-ZnxCd1-xS nanocrystals dispersed in 3D porous graphene nanostructure, possessing excellent charge separations and suitable band structures, are applied in hydrogen generation through photocatalytic water splitting. The relevant properties of the synthesized graphene based nanostructures and the performances of the supercapacitors, DSSCs, and photocatalysts are investigated and discussed in this study.