Highly Robust 3D rGO Aerogel with Tunable Thermoelectric Effect for Multifunctional Sensing Applications

The increasing demands for all-carbon-based flexible sensors in engineering have intensified research efforts toward multifunctional integration that responds to diverse stimuli. In this study, a three-dimensional (3D) reduced graphene oxide thermoelectric aerogel (rGOTEA) was created by a chemical agent-assisted bottom-up assembly with nanometer-thick rGO sheets as basic building units. Through bidirectional freeze-squeezing and reconstructing treatments, the hyperbolically patterned 3D rGOTEA exhibited lightweight density (≤5.4 mg cm^-3), superelastic deformation capability (recoverable strain ≥ 90%) and remarkable fatigue resistance. By quantitative regulation of oxygen-containing groups' distribution and interfacial bonding conditions, the carrier transport and phonon scattering over the multilayered rGO sheets were decoupled to optimize rather than that of 3D graphene monoliths with intact crystal structures. Attributed to numerous graphitized domains and in-plane defects (e.g., dangling bonds and holes), the 3D rGOTEA exhibited high electrical conductivity (95.834 S m^-1) yet low thermal conductivity (0.028 W m^-1 K^-1). 3D rGOTEA demonstrated a programmable thermoelectric performance with a tunable Seebeck coefficient ranging from 6.9 to 19.5 μV/K. This tunability endowed the material with a heightened sensitivity for detecting fluctuations in external physical signals. As a result, the flexible rGOTEA device displayed multifunctional sensing responses to changes in thermal insulation, electrical conductivity, and mechanical deformation. Moreover, an rGOTEA-based thermal energy converter was assembled to deliver a maximum output of 600 μV under a temperature gradient of 2.4 K/mm. The versatility of the 3D rGOTEA suggested its promising applications as multifunctional sensors, thermal insulator, and energy harvestor.