Tailoring charge affinity, dielectric property, and band gap of bacterial cellulose paper by multifunctional Ti2NbO7 nanosheets for improving triboelectric nanogenerator performance

Transparent, flexible, and high-performance triboelectric nanogenerator (TENG) from nature-derived materials are required for sustainable society development. However, low triboelectricity from natural material is generally observed. Tunable electronic band diagram (EBD) through facile manipulation is one of the efficient methods to promote the TENG output, requiring fundamental, in depth understanding. Herein, we employed the high quality, single crystal-like Ti2NbO7 nanosheets (NSs) with dual dielectric and semiconducting properties as filler for bacterial cellulose (BC)-based TENG. Several techniques including Xray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), ultraviolet visible (UV vis) absorption, energy dispersive X-ray spectroscopy (EDS), and synchrotron radiation X-ray tomographic microscopy (SRXTM) were applied to characterize the long-range structure, microstructure, optical properties, elemental composition, and three-dimensional (3D) distribution of components in the composites. The semi-transparent and flexible 5 vol.% Ti2NbO7 NSs/BC preserved the integrity of cellulose, contained well-dispersed nanosheets, reduced optical band gap (4.20 vs. 5.75 eV for BC), and increased surface roughness. The dielectric permittivity and conductivity increased with nanosheets content. Adding negatively-charged Ti2NbO7 NSs could regulate the charge affinity of BC composite via shifting of Fermi energy over that of Al. It is found that adding 5 vol.% NSs into the BC film improved electrical outputs (similar to 36 V and similar to 8.8 mu A), which are 2-4 times higher than that of pure BC, even when paired with Al which lies adjacent in triboelectric series. Our work demonstrated the method to enhance BC-based TENG performance through EBD regulation using multifunctional Ti2NbO7 NSs.

Automated summary

This study demonstrates the use of high-quality Ti2NbO7 nanosheets as fillers in bacterial cellulose-based TENG, resulting in improved performance through the regulation of the electronic band diagram. The addition of Ti2NbO7 nanosheets significantly increases the electrical output of the TENG.