水热法制备三维导电石墨烯气凝胶及其焦耳热性能研究

Joule-heating studies of different electric-conducting nanocarbon aerogels have been extensively exploited, however, there are no systematic investigations on the Joule-heating characteristics of reduced graphene oxide (rGO) aerogels prepared via the hydrothermal approach. Therefore, this work adopted the hydrothermal and freeze-drying methods, followed by thermal reduction to fabricate three-dimensional, cylindrical, and electric-conducting reduced hydrothermal graphene oxide aerogel, i.e., rHT-GO aerogel. Electron microscopic analysis showed that the aerogel interior presented a high density of nanocarbon interconnectivity and multiscale porosity, providing numerous paths for electrons to transport, hence available for systematic Joule-heating studies. The results demonstrated that the power input and Joule-heating temperature exhibited a good linear correlation with R² > 0.999, high electrothermal transformation efficiency (reaching up to 128℃ with only 2 W energy consumption), ultrafast heating/cooling capacities, long-duration electrothermal performance and excellent cycling capability. The 3D variable range hopping (3D VRH) model elucidated that the Joule-heating effects can reach the entire rHT-GO aerogel. The high electrical conductivity (9.0 S∙m^-1) was originated from the small bandgap (E_a = 0.015 eV). Additionally, the radial temperature gradient fitting results corroborated that the as-prepared rHT-GO aerogels also displayed distinct thermal conductivity (0.222 W∙m^-1∙K^-1), resulting in their ultrafast cooling rates (456 K∙min^-1) and consequently outperforming traditional external radiative heating modes. Importantly, the as-prepared cylindrical rHT-GO aerogels in this study can also be potentially utilized as Joule-heating-assisted adsorption/desorption agents, energy-efficient heaters, temperature-controllable catalyst supports, highly accurate sensors, and solar water evaporators.