Toward the Development of Graphene/Chitosan Biocomposite Aerogels with Enhanced Mechanical and Thermal Insulation Performance

Developing lightweight three-dimensional (3D) materials from biopolymers that exhibit high heat resistance, improved mechanical strength, and low thermal conductivity is crucial for numerous advanced applications. Herein, we successfully fabricated low-density biocomposite aerogels based on chitosan (CS) with exceptional porous structures (porosity exceeding 98%) by utilizing a straightforward approach free of hazardous chemicals. These aerogels combined high mechanical performance, thermal insulation, thermal stability and fire safety. This was achieved through the incorporation of a small amount of graphene nanofillers (G) using an eco-friendly freeze-drying process. The significant influence of the synthesis method as well as the composition and microstructure on the mechanical and thermal insulation performance of G-CS aerogels were highlighted. Two dispersion approaches for graphene were compared: direct addition to the CS solution followed by sonication, and predispersion in water before incorporation into the CS solution. After multidirectional random freezing at different temperatures (−30, −60, and −196 °C) and subsequent freeze-drying, the second approach yielded superior mechanical properties in G-CS aerogels. These aerogels showed improved mechanical resistance with increasing graphene content, reaching a Young’s modulus of 376 KPa, which was 2.75 times larger than that of pure chitosan aerogel. G10-CS showed a remarkable compressive strength to bear loads, approximately 3000 times its weight. Scanning electron microscopy (SEM) analyses revealed that graphene incorporation and reducing the freezing temperature to −60 °C transformed the aerogel’s microstructure from lamellar to a 3D interconnected honeycomb-like structure, resulting in reduced thermal conductivity (0.038 W m–1 K–1). The G10-CS composite aerogel is expected to be a promising candidate for various practical applications, including thermal and acoustic insulation, energy storage systems, gas detection sensors, biomedical devices, environmental remediation, advanced filtration technologies, and drug delivery.