Thermoelectric Properties of Graphene-Carbon Nanotube Aerogels as ‘Organic’ Energy Harvesters

In this work, we prepared graphene-carbon nanotube (Gr-CNT, hereon) and nitrogenated analogs three dimensional scaffolds using facile hydrothermal technique as thermal and thermo-electrochemical energy harvesters. The resulting aerogels are structurally ordered with ultralow densities and tunable mesoscopic pore sizes by means of organic wet chemistry used to cross-link the component nanomaterials yielding multiplex hierarchical topologies. In contrast to methods that utilize physical cross-links between GO nanosheets, this approach with polymeric linkers and organic functionalization provides covalent carbon bonding among the graphene nanosheets and molecular attachment with carbon nanotubes, facilitating rapid and facile electron and ion transport. They exhibit large internal surface area thus promote enhanced surface ion adsorption viable for use in thermal energy harvesting technologies. They have shown improved electrical conductivities (> 5 S.cm^-1), higher Seebeck coefficient (> 0.5 V.K^-1), and moderate thermal conductivity (~0.028 W.m^-1.K^-1). Complementary characterization techniques such as electron microscopy, Raman spectroscopy and scanning electrochemical microscopy established structural property-activity-performance correlations.