Control of Graphene Nanostructures for Superior Energy Storage and Thermoelectric Materials

Graphene has great interests because of its incredible properties for the potential future applications, such as high electrical & thermal conductivity, high surface area and their transparency, from molecular-levelly thin two-dimensional materials. In this talk, I firstly present sub-10-nm graphene nanoribbons and nanomeshes for the measuring field effect transistor property and thermoelectric property which fabricated by self-assembled block copolymer patterns as a lithographical template on chemical vapor deposition (CVD) grown graphene mono- and bi- layer sheets. We also measured thermal conductivity and Seebeck coefficient of graphene nanomesh using optothermal Raman technique and conventional thin film type Seebeck coefficient measuring system.

For the second part, we fabricated three-dimensional (3D) graphene structures with templated-assisted crumpled graphene approach and directionally porous ice-templated approach for the energy storage application, such as supercapacitor electrodes. We introduce a sea urchin-like spiky template with simultaneous chemical etching/reduction process for the fabrication of 3D crumpled graphene balls. And, using a facile ice-templated self-assembly process with reduced graphene sheets and vanadium phosphate (VOPO4) nanosheets, we realize a three-dimensional (3D) porous graphene/VOPO4 nanosheet nanocomposite with high surface area and high electrical conductivity for the enhanced pseudocapacitive properties. In the last part, we also used the vertically porous graphene nanostructures as a stretchable supercapacitor electrode. Radially compressed honeycomb structures exhibited reentrant framework and negative Poission ratio structures and maintained their structure and electrical conductivity even at 100 % of biaxially stretched states. These stretchable graphene structures also shows superb capacitive performance among the stretchable supercapacitors and still maintains high performance in high stretch conditions and highly repetitive tension experiments in full cell architectures.