Enhanced performance of direct-current triboelectric nanogenerators based on SiO₂-PVDF composite fibers coated with...

Direct-current triboelectric nanogenerators (DC-TENGs) based on metal-semiconductor interfaces are attractive for self-powered electronics because they can generate usable direct current without external rectification. However, their performance is often limited by insufficient charge transport in porous polymer membranes, especially under humid conditions. Herein, we report a DC-TENG based on SiO₂-PVDF composite fibers fabricated via vapor phase infiltration (SiO₂-VPI) and subsequently coated with TiO₂ by spatial atomic layer deposition (TiO₂-SALD). Porous PVDF fibers membranes were first prepared by electrospinning a PVDF/PVP precursor, followed by PVP removal. SiO₂-VPI was then employed to incorporate SiO₂ into the PVDF fiber network, forming SiO₂-PVDF composite membrane while preserving the porous morphology. This treatment improved the membrane hydrophilicity and promoted more uniform TiO₂ deposition during the subsequent SALD process. As a result, the optimized membrane exhibited significantly enhanced DC-TENG performance under humid conditions, delivering a current density of 341 µA cm^-2 and an output voltage of 0.72 V. A maximum power density of 82.8 µW cm^-2 was obtained at 3000 Ω, which is approximately twice that of the direct-TiO₂-SALD control. The device also showed stable operation over 4000 cycles and was capable of directly charging capacitors and powering a digital thermo-hygrometer. These results demonstrate that the integration of SiO₂-PVDF composite fibers with TiO₂ coating by SALD provides an effective route to high-performance DC-TENGs for energy harvesting.