Vertical contact-separation mode triboelectric generator (TEG) based on lead-free perovskite, zinc stannate (ZnSnO 3 )-polyvinylidene fluoride (PVDF) composite and polyamide-6 (PA6) membrane is demonstrated. For the 5wt% PVDF-ZnSnO 3 nanocomposites, the facile phaseinversion method provides a simple route to achieve high crystallinity and β-phase with a piezoelectric coefficient d 33 of -65 pmV -1 , as compared to -44 pmV -1 for pristine PVDF membranes. Consequently, at a cyclic excitation impact of 490 N/3 Hz, the PVDF-ZnSnO 3 /PA6 based TEGs provide a significantly higher voltage of 520 V and a current © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2 density of 2.7 mAm -2 (corresponding charge density of 62.0 µCm -2 ), as compared to the pristine PVDF-PA6 TEG which provides up to 300 V with a current density of 0.91 mAm -2(corresponding to a charge density of 55.0 µCm -2 ). This increase in the electrical output can be attributed to not only the enhanced polarisation of PVDF by ZnSnO 3 leading to an increase in the β-phase content, but also to the surface charge density increase by stress induced polarisation of ZnSnO 3 , leading to the generation of stronger piezoelectric potential.The work thus introduces a novel method of enhancing the surface charge density via the addition of suitable high polarization piezoelectric materials thus eliminating the need for prior charge injection for fluoropolymer membranes.

Electrospinning is a simple, versatile technique for fabricating fibrous nanomaterials with the desirable features of extremely high porosities and large surface areas. Using emulsion electrospinning, polytetrafluoroethylene/polyethene oxide (PTFE/PEO) membranes were fabricated, followed by a sintering process to obtain pure PTFE fibrous membranes, which were further utilized against a polyamide 6 (PA6) membrane for vertical contact-mode triboelectric nanogenerators (TENGs). Electrostatic force microscopy (EFM) measurements of the sintered electrospun PTFE membranes revealed the presence of both positive and negative surface charges owing to the transfer of positive charge from PEO which was further corroborated by FTIR measurements. To enhance the ensuing triboelectric surface charge, a facile negative charge-injection process was carried out onto the electrospun (ES) PTFE subsequently. The fabricated TENG gave a stabilized peak-to-peak open-circuit voltage (V) of up to ∼900 V, a short-circuit current density (J) of ∼20 mA m, and a corresponding charge density of ∼149 μC m, which are ∼12, 14, and 11 times higher than the corresponding values prior to the ion-injection treatment. This increase in the surface charge density is caused by the inversion of positive surface charges with the simultaneous increase in the negative surface charge on the PTFE surface, which was confirmed by using EFM measurements. The negative charge injection led to an enhanced power output density of ∼9 W m with high stability as confirmed from the continuous operation of the ion-injected PTFE/PA6 TENG for 30 000 operation cycles, without any significant reduction in the output. The work thus introduces a relatively simple, cost-effective, and environmentally friendly technique for fabricating fibrous fluoropolymer polymer membranes with high thermal/chemical resistance in TENG field and a direct ion-injection method which is able to dramatically improve the surface negative charge density of the PTFE fibrous membranes.

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Significant triboelectric enhancement using interfacial piezoelectric ZnO nanosheet layer, Nano Energy, http://dx.doi.org/10. 1016/j.nanoen.2017.08.053 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Utilising an interfacial piezoelectric ZnO nanosheet layer, a significant enhancement in the power density is reported for the triboelectric nanogenerators (TENG) based on phase inversion membranes of polyvinylidene fluoride (PVDF) and polyamide-6 (PA6). At an applied force of 80 N, the TENG device incorporating electrochemically deposited ZnO nanosheets produces an output voltage of ~625 V and a current density of ~40 mAm -2 (corresponding a charge density of 100.6 Cm -2 ), respectively; significantly higher than ~310 V and ~10 mAm -2 (corresponding a charge density of 77.45 Cm -2 ) for the pristine TENG device. The enhancement in the surface charge density provided by the interfacial piezoelectric ZnO layer is also reflected in the high piezoelectric coefficient d 33 (-74 pmV -1 ) as compared to the pristine fluoropolymer membranes (-50 pmV -1 ). For tribo-negative membranes incorporating the interfacial ZnO layer, piezoelectric force microscopy measurements further show enhanced domain size which can be attributed to the interfacial dipole-dipole interaction with the ferroelectric polarization of PVDF, which promotes the alignment with the polar axis of ZnO. Under compressive stress, the piezoelectric potential thus produced in the ZnO nanosheets provides charge injection on to the surface of ZnSnO 3 -PVDF membrane, improving the charge density, which in-turn significantly enhances the power density from 0.11 to ~1.8 W/m 2 . The TENG devices thus fabricated using a facile electrochemical deposition and phase inversion technique show enhanced output power without the need for high electric field poling or external charge injection process by relying on coupling of triboelectric and piezoelectric effects.