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The development of triboelectric nanogenerators (TENGs) can convert mechanical energy into electricity and bring new prospect for energy crisis. Improving tribo-charge surface density and contact area are two pivotal factors to enhance the output performance of TENG. However, improving the charge density and manipulating surface structure cannot be achieved simultaneously and complicated fabrication procedures may limit application of TENG. In this work, an environment friendly TENG based on bacteria cellulose film fabricated via facile vacuum filtration method was reported. In the presence of modifications, high dielectric particles BaTiO 3 were introduced into BC nanofiber film to improve the dielectric constant as well as construct micro-nano structure at the same. With the combination of the enhancement of dielectric constant and surface structure of BC nanofibers layer, the open voltage of 181 V, the short current of 21 μA, and transfer charge of 76.6 nC was achieved at a frequency of 2 Hz and a peak force of 42 N with the optimized film consisting of 13.5 vol% BaTiO 3 particles. Additionally, a peak power density of 4.8 W/m2 was achieved when connecting with the resistance in series. Moreover, the TENG showed excellent stability and can harvest the mechanical energy by human motion. This work gives a better understanding of the triboelectricity produced by the TENG from the point of materials and provides a feasible and effective way to enhance the output performance of TENG from the material itself as well as surface modification. Image 1 • Improving the dielectric constant and surface roughness of triboelectric material simultaneously when introducing BaTiO 3 particles. • Fabricating environmentally friendly TENG by easily vacuum filtration method. • Excellent flexibility greatly facilitates the application of TENG integrating with the clothes to harvest mechanical energy from human motion. • Achieving outstanding electric output performance by facile method. [ABSTRACT FROM AUTHOR]

A flexible nickel foam (NF) based reduced Holey Graphene Oxide (rHGO) wrapping on NiO@NF hybrid supercapacitor electrode is fabricated using facile hydrothermal reaction followed by HGO dispersion dipping to achieve an efficient, bendable and scalable supercapacitor with high capacitance for wearable smart device usage. The sample electrode reveals a typical wrapping morphology of porous rHGO spreading on uniform nickel oxide crystal layer while exposing crystals through recurrent rHGO slits. Benefiting from this morphology and optimization of fabrication parameters, the sample electrode gains better electrochemical performance from higher electric double layer capacitance incorporation and more efficient electrolyte ion transportation, with less than 0.1 Ω equivalent series resistance (ESR), 752.9 F/g of capacitance, and 90% capacitance retention under 10 A/g current density. The sample electrode is then made into an all-solid-state supercapacitor device possessing 0.267 Wh/m2 energy density at a power density of 8.14 W/m2, and the bendable fact of the device endows it 97% capacitance retention after 500 times of curving, making it especially suitable as flexible energy provider. This simple fabrication method should shed light on flexible hybrid supercapacitor development. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs), a promising energy harvesting technology, have been rapidly developed in past few years. However, the specific structure and complicated preparation method greatly limited their mechanical flexibility as well as their potential applications. In this work, a novel and effective strategy to fabricate all-in-one triboelectric nanogenerator(TENG) was reported. The as-mentioned TENG was based on rubber/carbon nano-fiber composites achieved by supercritical carbon dioxide foaming process, which is environmentally friendly and suitable for mass production. Under the optimal condition, 91 V of the open voltage, 2.87 μA of short current and 40 nC of transferred charge was obtained, while this structure contributed to about 10-fold enhancement to transferred charge compared with the single-layer structured TENG at the same area of 4 cm2. The flexible silicone rubber based TENG can collect complex mechanical energy, such as stretching, twisting, bending and compressing. Moreover, when being pasted on soles, it can harvest the mechanical energy from human motion and the outputs can also be regarded as sensing signals which can be used to analyze the gait and sense the motion. This work provides a feasible and effective way to prepare an all-in-one TENG with high outputs, which can bring potential for the industrialized production and widespread application. Image 1 • Achieving an all-in-one and porous TENG based on rubber/carbon nano-fiber composites. • Fabricating flexible TENG by easily supercritical carbon dioxide foaming strategy. • Simple structure and excellent flexibility makes TENG collect complex mechanical energy, judge gait when pasting on soles. [ABSTRACT FROM AUTHOR]

A hierarchical structure is proved to be important for the improvement of electrochemical performances of MnO 2 -based electrode materials used in supercapacitors. However, the rational design of materials' structure and its real performance served as electrode materials are still facing challenges. Herein, hierarchical porous carbon nanofibers using ZIF-8 nanoparticles as pore templates are designed to provide one-dimensional hollow frameworks for the growth of ultrathin MnO 2 nanosheets (referred as HPCNF/MnO 2). The as-prepared HPCNF/MnO 2 samples have a hierarchical coaxial core-shell structure, with HPCNFs as the core and MnO 2 sheets as the shell. The novel nanostructure of this hybrid provides abundant electrochemical active sites for Faradic reactions and short diffusion channels for ions/electron transport. The utilization of HPCNF/MnO 2 active material with such a structure can be significantly enhanced, especially at the high current density. When evaluated as electrode materials, HPCNF/MnO 2 exhibits a specific capacitance of 269 F g−1 at 0.5 A g−1 (308 F g−1 for MnO 2), a high capacitive retention of 98% even after 5000 cycles at 50 mV s−1 by cyclic voltammetry (86.7% capacitance retention at 1 A g−1 after 2000 cycles) and a rate capability of 58% from 0.5 to 10 A g−1. Especially at the current density of 10 A g−1, the specific capacitance of HPCNF/MnO 2 has increased by 133% compared with that of non-porous carbon fiber/MnO 2 composites, demonstrating a great superiority of hierarchical porous carbon nanofibers as frameworks to support pseudocapacitive materials. [ABSTRACT FROM AUTHOR]

We reported a novel and effective strategy to achieve higher continuity at a lower volume fraction of interphase by using compatibilizers in ternary blend consisting of PVDF, PS and HDPE. PVDF-g-PS was synthesized by electron beam radiation induced free radical graft copolymerization reaction and PVDF-g-PS was characterized by FTIR, DSC and 1 H NMR. PVDF-g-PS showed effective compatibilization in PVDF/PS binary blend. The phase size of PVDF/PS binary blend was decreased at addition of PVDF-g-PS. For phase morphology development, morphology of uncompatibilized PVDF/PS/HDPE (52/6/42 vol%) ternary blend revealed a part of PS droplets situated in PVDF/HDPE interface, the other part was located inside HDPE phase. Whereas, compatibilized blend showed more and more PS migrate to PVDF/HDPE interface. When adding 7% PVDF-g-PS, PS droplets formed into uniform layer self-assembly arrayed at interface, then tri-continuous morphology was formed and continuity of PS phase increased by 32%, ultralow percolation threshold ternary blend was successfully achieved. [ABSTRACT FROM AUTHOR]

High-performance supercapacitors are widely studied, but few works have paid attention to the optimization of conductive bonding networks in the electrode to improve its electrochemical performance. Herein, a rationally designed three-dimensional (3D) conductive bonding network consisting of one-dimensional carboxylated carbon nanotubes (CNT-COOH) and two-dimensional reduced holey graphene oxide (rHGO) is introduced to porous carbon nanofiber/ultra-thin MnO 2 nanosheets (PCNF/U-MnO 2) electrode through vacuum filtration. The CNT-COOH/rHGO network endows the electrode with desired electron transport and ion diffusion properties for its advantages in 3D structures, conductivity and electrolyte wettability, which promote efficient use of PCNF/U-MnO 2 active materials. Thus, PCNF/U-MnO 2 in the electrode with CNT-COOH/rHGO network shows better capacitive performance than that of traditionally fabricated electrode with PTFE and acetylene black. Besides, CNT-COOH/rHGO network is conducive to structural stability of PCNF/U-MnO 2 electrode, and it obtains a capacitance retention of 87% even after 4500 cycles. Then, an asymmetric supercapacitor with PCNF/U-MnO 2 cathode and N, B-doped PCNFs anode has been assembled, which exhibits good flexibility using LiCl/PVA hydrogel as electrolyte and has a high energy density of 45 Wh kg−1 at a power density of 540.8 W kg−1. The strategy of CNT-COOH/rHGO network construction can be an effective and promising way beneficial to high-performance supercapacitor fabrication. [Display omitted] [ABSTRACT FROM AUTHOR]