Multifunctional hierarchical graphene-carbon fiber hybrid aerogels for strain sensing and energy storage

Graphene oxide nanosheets can be assembled into multifunctional graphene aerogels for sensing and energy storage applications. However, due to strong van der Waals forces, reduced graphene oxide nanosheets often stack together, significantly compromising their performance. Here, we demonstrate high-performance multifunctional hybrid carbon aerogels by hybridizing graphene oxide nanosheets with functionalized carbon fibers using a hydrothermal assembly method followed by two-step freezing, natural drying, and annealing. We compared the difference between carbon microfibers and carbon nanofibers. Our results show that flexible carbon nanofibers can enable more bindings with graphene nanosheets, creating stabler three-dimensional structures and enabling more efficient electron transfer. The resulting hybrid graphene aerogels have a high compressive strength of 56.7 kPa at 50% strain, an electrical conductivity of 3.072 S m(-1), and a strain-responsive electrical response sensitivity of 11.3 k Pa-1 in a low-pressure range of 0-0.15 kPa. These hybrid carbon aerogels were applied in strain sensors to detect various human bio-signals. Furthermore, they were used as free-standing electrodes in flexible supercapacitors, demonstrating satisfactory energy storage performances. Overall, we show that three-dimensional graphene-carbon nanofiber hybrid aerogels have excellent multifunctional properties for applications in flexible electronics and energy storage devices.