Triboelectric nanogenerator-integrated symmetric supercapacitor based on TiO2 encrusted MXene nanosheets for energy harvesting and storage applications

Abstract

With the rapid advances in the Internet of Things, it is possible to construct a self-charging power system integrating a triboelectric nanogenerator (TENG) and supercapacitor (SC), which represents an excellent tool for simultaneous conversion and storage of distributed environmental energy. In particular, the well-researched Ti3C2T x MXene materials for triboelectric nanogeneration lack high and stable power density, mainly due to the charge dissipation effect on their surface. Herein, the effectiveness of MXenes is enhanced by encrusting TiO2 on the inner and outer surfaces via a hydrothermal method. TiO2, which has inherent dielectric properties, could serve the dual function of electron trapping/blocking and surface polarization, mitigating the diffusion and drifting of surficial tribo-charges and thus increasing output TENG performance. An integrated TENG based on MXene/TiO2 composites with a TiO2 concentration of 3 mM has a higher output voltage than a pristine MXene-based TENG (110 V, a 1.83-fold increase) and achieves a maximum instantaneous power density of ∼1440 mW m−2. TiO2 is also conductive to pseudo-faradaic reactions, and the integrated MXene/TiO2 based symmetric SC exhibits an enhanced specific capacitance of 231.08 F g−1 at 1 A g−1, which is 4.52 times that of pristine MXene, with a maximum energy density of 12.74 W h kg−1 at a power density of 483.06 W kg−1. Finally, utilizing polyimide sheets as substrates, the flexible self-charging power system was integrated: the TENG charges the SC up to 0.8 V with a charging/discharging time of 37 s/40 s, showing great promise for the demands of flexible and self-powered electronics.