ZnO nanorods@conductive carbon black nanocomposite based flexible integrated system for energy conversion and storage through triboelectric nanogenerator and supercapacitor

Highlights: • A flexible integrated energy conversion and storage system is developed. • The work function of ZnO NRs is tuned with a simple coating of conductive carbon black. • Facilely fabricated ZnO NRs@CB NCs coated NF is used to develop flexible TENG as well as a flexible supercapacitor. • A flexible integrated system composed of a FZCT and a FZCS works efficiently as a power source for wearable electronics. Owing to the tremendous increase in global environmental pollution and the scarcity of fossil fuel depletion, the scout for new, renewable, and green energy alternatives has been escalated. Specifically, flexible energy conversion and storage devices that act as power sources for wearable electronics are in demand. Herein, we propose an integrated energy conversion and storage system composed of flexible ZnO nanorods (NRs)@conductive carbon black (CB) nanocomposite (NC) based triboelectric nanogenerator (FZCT) and supercapacitor (FZCS). Firstly, ZnO NRs are prepared via a facile precipitation method and then the work function of the ZnO NRs is tuned with the addition of CB. The FZCT is fabricated using ZnO NRs@CB NCs coated nickel foam (NF) as a positive tribo-layer against counter tribo-layer (PTFE). FZCT with optimized content of CB (20 wt%) generated an open circuit voltage (V_OC) of 28 V, a short circuit current (I_SC) of 4.5 µA, and a power density of 80 µW/cm². The V_OC and the I_SC values of the FZCT with optimized CB content are greater than that of pure ZnO NRs based FZCT. The FZCS is developed using the same ZnO NRs@CB/NF as a positive electrode and activated carbon coated NF (AC/NF) as a negative electrode in 1 M Na₂SO₄ electrolyte. The areal capacitance, maximum areal energy density, and power density of the FZCS are, 448 mF/cm², 0.12 mW h/cm², and 27.44 mW/cm², respectively. Furthermore, an integrated energy conversion and storage system is successfully implemented by connecting the FZCT and FZCS through a bridge rectifier. The integrated device is able to convert and store the energy generated by FZCT very efficiently. The experiments reveal that the FZCT developed from this study can deliver the electrical output while it is attached even onto the human body. This study offers new opportunities in integrated energy conversion and storage devices with simple structured flexible materials.