Density-Induced Joule-Heating Characteristics of Nanocarbon Aerogels: Implications for Tunable Electrothermal Behaviors

Abstract

An in-depth understanding of the electrothermal characteristics and behaviors of nanocarbon aerogels is crucial for optimizing their Joule-heating performance and expanding their applications. Modifying a single parameter of nanocarbon aerogels can reveal potential variations in Joule heating, which makes it a valuable area for investigation. This study explores reduced graphene oxide aerogels and reduced graphitized nanofiber aerogels with varying densities (14.9–31.7 mg·cm–3), fabricated using the hydrothermal method and polymer-assisted cross-linking method, to elucidate density-induced Joule-heating discrepancies. The critical step in aerogel preparation is the freeze-drying process, which yields structurally intact nanocarbon aerogels for Joule-heating experiments. Aerogels with higher densities displayed enhanced electrical and thermal conductivities (up to 24.9 S·m–1 and 0.882 W·m–1·K–1, respectively) compared to their lower-density counterparts, owing to the increased number of pathways available for electron/phonon transportation. The low-density aerogels exhibited more pronounced features in the heating temperature range (up to 117 °C) and efficiency (up to 46.5 °C·W–1), making them more suitable for energy-efficient applications. Despite variations in the density, all of the fabricated aerogels showed efficient electron hopping between the interconnected nanocarbons, which enabled uniform resistive heating throughout the aerogel entity. This work highlighted the importance of density control in altering the Joule-heating performance of nanocarbon aerogels for specific applications, which has far-reaching implications for optimizing the properties of other electrically conducting aerogel materials.