Porous cellulose composite aerogel films with super piezoelectric properties for energy harvesting.

The piezoelectric effect is one of the most promising electromechanical coupling processes for mechanical energy conversion and energy harvesting. However, natural polymer based piezoelectric materials are of poor piezoelectric performance. we developed flexible porous piezoelectric aerogel films based on TEMPO-oxidized cellulose nanofibrils (TOCN) and MoS2 nanosheets. Those aerogel films possessed large specific surface areas and abundant mesopores. Moreover, they exhibited very good piezoelectric properties when a field strength of 20 MV/m was used to polarize MoS2 nanosheets and air in the mesopores. When assembled to piezoelectric nanogenerators (PENGs), a TOCN/MoS2 aerogel film PENG containing 6 wt% of MoS2 exhibited the best output performance. It generated an open circuit voltage of 42 V and a short-circuit current of 1.1 µA, a maximum area power density of 1.29 µW/cm2 and a maximum volume power density of 0.143 µW/cm3. These features enable them to be promising piezoelectric materials for energy harvesting.