Fiber‐based flexible thermoelectric energy generators are 3D deformable, lightweight, and desirable for applications in large‐area waste heat recovery, and as energy suppliers for wearable or mobile electronic systems in which large mechanical deformations, high energy conversion efficiency, and electrical stability are greatly demanded. These devices can be manufactured at low or room temperature under ambient conditions by established industrial processes, offering cost‐effective and reliable products in mass quantity. This article presents a critical overview and review of state‐of‐the‐art fiber‐based thermoelectric generators, covering their operational principle, materials, device structures, fabrication methods, characterization, and potential applications. Scientific and practical challenges along with critical issues and opportunities are also discussed.

The progress of spontaneous energy generation from ubiquitous moisture is hindered the low output current and intermittent operating voltage of the moisture‐electric generators. Herein a novel and efficient ionic hydrogel moisture‐electric generator (IHMEG) is developed by rational combination of poly(vinyl alcohol), phytic acid, and glycerol‐water binary solvent. Thanks to the synergistic effect of notable moisture‐absorption capability and fast ion transport capability in the ionic hydrogel network, a single IHMEG unit of 0.25 cm2 can continuously generate direct‐current electricity with a constant open‐circuit voltage of ≈0.8 V for over 1000 h, a high short‐current density of 0.24 mA cm−2, and power density of up to 35 µW cm−2. Of great importance is that large‐scale integration of IHMEG units can be readily accomplished to offer a device with voltage up to 210 V, capable of directly driving numerous commercial electronics, including electronic ink screen, metal electrodeposition setup, and light‐emitting‐diode arrays. Such prominent performance is mainly attributed to the enhanced moisture‐liberated proton diffusion proved by experimental observation and theoretical analysis. The ionic hydrogel with high cost‐efficiency, easy‐to‐scaleup fabrication, and high power‐output opens a brand‐new perspective to develop a green, versatile, and efficient power source for Internet‐of‐Things and wearable electronics.

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Despite of the rapid development and demonstrations of wearable energy harvesting devices, their industrial applications have been limited by the lack of highly flexible, scalable and facile fabrication method. Especially, few studies have involved the theoretical analysis with the relevant experimental verification. To this end, we demonstrate a highly flexible and large-area textile-based hybrid nanogenerator integrated a net-shaped nanofiber reinforced piezoelectric unit and a triboelectric unit with a micro-structured surface configuration.Electrospinning technique was used to fabricate an optimized PVDF-CNT-BaTiO3 nanofiber/particle nonwoven fabric of 18 cm×27 cm for the piezoelectric unit without further polarization. Then a large-area free-standing PDMS-MWCNT-Graphite flexible composite film of 20 cm×25 cm, optimized for the triboelectric unit was prepared by doctor-blading method. The resultant hybrid nanogenerator, with 4.5 cm×5 cm in size, generated a rectified average peak output voltage of 161.66 V, along with the highest peak power output of 2.22 W/m 2 , directly driving 150 LEDs. Importantly, explicit theoretical model for the hybrid nanogenerator were proposed and good agreements were obtained between the theoretical and corresponding experimental results, which sheds new lights on the mechanism and predicts the ways to optimize such hybrid nanogenerators.

Piezoelectric catalysis (piezocatalysis) is a physical/chemical process that utilizes piezoelectric potential for accelerating chemical reactions, in which ubiquitous mechanical energies in nature are used for various catalysis applications, e.g., treating organic water pollutants. Despite the high efficiency achieved by piezocatalytic powders, the particles used tend to diffuse in water systems and are hard to be separated, thus causing secondary pollution. Herein, a free‐standing piezocatalytic foam is designed and fabricated, which is composed of BaTiO3 nanoparticles embedded in the PVDF scaffold. The as‐prepared PVDF–BaTiO3 composite foam demonstrates outstanding piezocatalytic efficiency in removing aqueous organics among state‐of‐the‐art integral piezocatalytic platforms, which lie in the synergy of piezoelectric materials and abundant interconnected pores within the foam. Significantly, PVDF–BaTiO3 foam is further applied for purifying natural water samples, by which the permanganate index of the water sample reduces by nearly 30% after 2 h of treatment. In addition, as a monolithic platform, PVDF–BaTiO3 foam is easy to be collected, with high reuse stability and applicability for treating various pollutants, resulting in dominant advantages over powder‐based systems for practical high‐flux wastewater treatment. Herein, a piezocatalytic platform is provided for the effective degradation of organic pollutants in water, with minimal environmental side effects.