Robust and ultra-thin nanocellulose/MXene composite film and its performance in efficient electricity-generation and sensing.

The conversion of mechanical energy into electrical energy by triboelectric nanogenerators (TENG) has attracted attention in recent years, particularly in the field of wearable sensor. In this work, TEMPO-oxidized cellulose nanofibers (TOCNF) with carboxylate groups were compounded with MXene to serve as both the negative friction layer and the electrode in assembling a TENG with nylon. The synergistic effect between TOCNF and MXene was analyzed to disclose its influence on the performance of the as-prepared TENG. The MXene/TOCNF composite film, containing 50 wt% MXene, exhibited the best performance among all specimens, and the assembled TENG demonstrated excellent performance with an open-circuit voltage of 210 V, a short-circuit current of 0.84 μA, and a transferred charge of 8.6 nC. The excellent output performance might be attributed to the presence of carboxylate and F-containing groups in the composite film. This flexible TENG also functioned as a self-powered sensor, generating sensitive and stable signals in response to human motion and writing. This work verifies the simultaneous use of robust and flexible nanocellulose/MXene composite films as both the friction layer and electrode, which could spur the development of TENGs using sustainable and abundant cellulosic materials.