Layered heterojunction of porous-oriented cellulose-based material to enhance electromechanical conversion and energy storage efficiencies for self-powered motion sensing.

Porous materials based on cellulose nanocrystals (CNCs), rich of hydroxyl groups facilitating electron transfer, are promising anode dielectric layers of wearable triboelectric nanogenerators (TENG) due to their light weight. To match the bio-based cathode dielectric layer, we fluorinated the CNCs surface to generate electron acceptors, which is then combined with neat CNCs to form a PN heterojunction structure. The UV-Vis spectroscopy shows that the electronic energy gap between fluorinated CNCs (FCNCs) and CNCs decreases to 3.87 eV. The heterojunction material, without additional negative dielectric layers, establishes a vertical contact-separation mode of TENG, achieving an output power of 354.2 mW/m. Then, sodium alginate is used as flexible base to prepare elastic porous material, and single-walled carbon nanotubes are used to construct conductive network. Such a porous material exhibits a capacitance of 2.66 F/g, and the conductive network enhance the dielectric constant of the material to 3521.2, resulting in enhancement in self-powering capabilities. Meanwhile, this composite also presents a high strain piezoresistive sensitivity of 3.67. Thus, this heterojunction design should be a high-value strategy for CNCs-based materials to improve electromechanical conversion and piezoresistive sensitivity simultaneously, alongside to establish energy storage ability.