Integration of advanced nanogenerator technology with conventional textile processes fosters the emergence of textile‐based nanogenerators (NGs), which will inevitably promote the rapid development ...and widespread applications of next‐generation wearable electronics and multifaceted artificial intelligence systems. NGs endow smart textiles with mechanical energy harvesting and multifunctional self‐powered sensing capabilities, while textiles provide a versatile flexible design carrier and extensive wearable application platform for their development. However, due to the lack of an effective interactive platform and communication channel between researchers specializing in NGs and those good at textiles, it is rather difficult to achieve fiber/fabric‐based NGs with both excellent electrical output properties and outstanding textile‐related performances. To this end, a critical review is presented on the current state of the arts of wearable fiber/fabric‐based piezoelectric nanogenerators and triboelectric nanogenerators with respect to basic classifications, material selections, fabrication techniques, structural designs, and working principles, as well as potential applications. Furthermore, the potential difficulties and tough challenges that can impede their large‐scale commercial applications are summarized and discussed. It is hoped that this review will not only deepen the ties between smart textiles and wearable NGs, but also push forward further research and applications of future wearable fiber/fabric‐based NGs.
Combining the advantages of smart textiles and mechanical energy harvesting technology, fiber/fabric‐based piezoelectric and triboelectric nanogenerators will play an increasing role in wearable electronics and artificial intelligences. In view of their current research status and development trends, a comprehensive, systematic, and multiperspective review is presented to provide better understanding and beneficial guidance for future research and product design.
A novel in situ replication and polymerization strategy is developed for the synthesis of Fe‐N‐doped mesoporous carbon microspheres (Fe‐NMCSs). This material benefits from the synergy between the ...high catalytic activity of Fe‐N‐C and the fast mass transport of the mesoporous microsphere structure. Compared to commercial Pt/C catalysts, the Fe‐NMCSs show a much better electrocatalytic performance in terms of higher catalytic activity, selectivity, and durability for the oxygen reduction reaction.
Electrochemical CO2 reduction to valuable ethylene and ethanol offers a promising strategy to lower CO2 emissions while storing renewable electricity. Cu‐based catalysts have shown the potential for ...CO2‐to‐ethylene/ethanol conversion, but still suffer from low activity and selectivity. Herein, the effects of surface and interface structures in Cu‐based catalysts for CO2‐to‐ethylene/ethanol production are systematically discussed. Both reactions involve three crucial steps: formation of CO intermediate, CC coupling, and hydrodeoxygenation of C2 intermediates. For ethylene, the key step is CC coupling, which can be enhanced by tailoring the surface structures of catalyst such as step sites on facets, Cu0/Cuδ+ species and nanopores, as well as the optimized molecule–catalyst and electrolyte–catalyst interfaces further promoting the higher ethylene production. While the controllable hydrodeoxygenation of C2 intermediate is important for ethanol, which can be achieved by tuning the stability of oxygenate intermediates through the metallic cluster induced special atomic configuration and bimetallic synergy induced the double active sites on catalyst surface. Additionally, constraining CO coverage by the complex–catalyst interface and stabilizing CO bond by N‐doped carbon/Cu interface can also enhance the ethanol selectivity. The structure–performance relationships will provide the guidance for the design of Cu‐based catalysts for highly efficient reduction of CO2.
This review focuses on the two very important products of CO2RR, ethylene and ethanol, and systematically discusses the surface and interface structure effects of Cu‐based catalysts for CO2‐to‐ethylene/ethanol conversions. The influence factors of activity and selectivity are summarized in detail and the structure–performance relationship of the catalyst for ethylene/ethanol is clearly displayed, especially combined with the recent important progresses.
Piezopotential‐assisted catalysis is of great significance for low cost and efficient catalysis processes. Here, Aux/BaTiO3 plasmonic photocatalysts are fabricated by precipitating Au nanoparticles ...on piezoelectric BaTiO3 nanocubes through a chemical approach. The Au nanoparticles (<8 nm) are decorated uniformly on the surface of BaTiO3, which endows the heterostructure with a wide light absorption from 300 to 600 nm. The photocatalytic properties of the heterostructures are investigated in detail toward methyl orange (MO) degradation. The Au content, piezoelectric potential of the BaTiO3 substrate, and surface plasmon resonance (SPR) are confirmed to be vital to the photocatalytic activity. The Au4/BaTiO3 shows an optimum photocatalytic performance for a complete degradation of MO in 75 min under full spectrum light irradiation with auxiliary ultrasonic excitation. The piezoelectric field originating from the deformation of BaTiO3 further enhances the separation of photon‐generated carriers induced by SPR and promotes the formation of hydroxyl radicals, which results in a strong oxidizing ability of organic dyes. This work introduces the piezotronic effect to enhance plasmonic photocatalysis with Aux/BaTiO3 heterostructures, which is ready to extend to other catalytic systems and offers a new option to design high‐performance catalysts for pollutant treatment.
The piezotronic effect is introduced to enhance plasmonic photocatalysis by fabricating Aux/BaTiO3 nano‐heterostructures. Piezoelectric polarization of the BaTiO3 nanocrystal upon sonication suppresses the recombination of photogenerated hot electron–hole pairs to enhance the localized surface plasmon resonance of Au nanoparticles to improve the photocatalysis process.
Hollow materials derived from metal–organic frameworks (MOFs), by virtue of their controllable configuration, composition, porosity, and specific surface area, have shown fascinating physicochemical ...properties and widespread applications, especially in electrochemical energy storage and conversion. Here, the recent advances in the controllable synthesis are discussed, mainly focusing on the conversion mechanisms from MOFs to hollow‐structured materials. The synthetic strategies of MOF‐derived hollow‐structured materials are broadly sorted into two categories: the controllable synthesis of hollow MOFs and subsequent pyrolysis into functional materials, and the controllable conversion of solid MOFs with predesigned composition and morphology into hollow structures. Based on the formation processes of hollow MOFs and the conversion processes of solid MOFs, the synthetic strategies are further conceptually grouped into six categories: template‐mediated assembly, stepped dissolution–regrowth, selective chemical etching, interfacial ion exchange, heterogeneous contraction, and self‐catalytic pyrolysis. By analyzing and discussing 14 types of reaction processes in detail, a systematic mechanism of conversion from MOFs to hollow‐structured materials is exhibited. Afterward, the applications of these hollow structures as electrode materials for lithium‐ion batteries, hybrid supercapacitors, and electrocatalysis are presented. Finally, an outlook on the emergent challenges and future developments in terms of their controllable fabrications and electrochemical applications is further discussed.
Recent developments of controlled synthesis of hollow‐structured functional materials by using metal–organic framework as precursors are summarized, along with their promising applications in electrochemical energy storage and conversion.
Most organic polymeric materials have high flammability, for which the large amounts of smoke, toxic gases, heat, and melt drips produced during their burning cause immeasurable damages to human life ...and property every year. Despite some desirable results having been achieved by conventional flame‐retardant methods, their application is encountering more and more difficulties with the ever‐increasing high flame‐retardant requirements such as high flame‐retardant efficiency, great persistence, low release of heat, smoke, and toxic gases, and more importantly not deteriorating or even enhancing the overall properties of polymers. Under such condition, some advanced flame‐retardant methods have been developed in the past years based on “all‐in‐one” intumescence, nanotechnology, in situ reinforcement, intrinsic char formation, plasma treatment, biomimetic coatings, etc., which have provided potential solutions to the dilemma of conventional flame‐retardant methods. This review briefly outlines the development, application, and problems of conventional flame‐retardant methods, including bulk‐additive, bulk‐copolymerization, and surface treatment, and focuses on the raise, development, and potential application of advanced flame‐retardant methods. The future development of flame‐retardant methods is further discussed.
Flame‐retardant methods for polymeric materials are reviewed with particular focus on advanced flame‐retardant methods developed in recent years. Both the advantages and drawbacks of these methods are discussed, and prospects for the future development of flame‐retardant methods are presented. It is hoped that this review will guide the development of flame‐retardant polymeric materials.
Triboelectric nanogenerators are an energy harvesting technology that relies on the coupling effects of contact electrification and electrostatic induction between two solids or a liquid and a solid. ...Here, we present a triboelectric nanogenerator that can work based on the interaction between two pure liquids. A liquid-liquid triboelectric nanogenerator is achieved by passing a liquid droplet through a freely suspended liquid membrane. We investigate two kinds of liquid membranes: a grounded membrane and a pre-charged membrane. The falling of a droplet (about 40 μL) can generate a peak power of 137.4 nW by passing through a pre-charged membrane. Moreover, this membrane electrode can also remove and collect electrostatic charges from solid objects, indicating a permeable sensor or charge filter for electronic applications. The liquid-liquid triboelectric nanogenerator can harvest mechanical energy without changing the object motion and it can work for many targets, including raindrops, irrigation currents, microfluidics, and tiny particles.
Contact electrification (CE) has been known for more than 2600 years but the nature of charge carriers and their transfer mechanisms still remain poorly understood, especially for the cases of ...liquid-solid CE. Here, we study the CE between liquids and solids and investigate the decay of CE charges on the solid surfaces after liquid-solid CE at different thermal conditions. The contribution of electron transfer is distinguished from that of ion transfer on the charged surfaces by using the theory of electron thermionic emission. Our study shows that there are both electron transfer and ion transfer in the liquid-solid CE. We reveal that solutes in the solution, pH value of the solution and the hydrophilicity of the solid affect the ratio of electron transfers to ion transfers. Further, we propose a two-step model of electron or/and ion transfer and demonstrate the formation of electric double-layer in liquid-solid CE.
Identifying effective means to improve the electrochemical performance of oxygen‐evolution catalysts represents a significant challenge in several emerging renewable energy technologies. Herein, we ...consider metal–nitrogen–carbon sheets which are commonly used for catalyzing the oxygen‐reduction reaction (ORR), as the support to load NiO nanoparticles for the oxygen‐evolution reaction (OER). FeNC sheets, as the advanced supports, synergistically promote the NiO nanocatalysts to exhibit superior performance in alkaline media, which is confirmed by experimental observations and density functional theory (DFT) calculations. Our findings show the advantages in considering the support effect for designing highly active, durable, and cost‐effective OER electrocatalysts.
Sitting on the FeNC: Metal–nitrogen–carbon sheets are used as the supports for metal oxide catalysts for the oxygen‐evolution reaction (OER). Iron–nitrogen–carbon (FeNC) sheets loaded with NiO nanoparticles give superior performance in alkaline media. The improved performance originates from a synergistic effect between the FeNC sheets and NiO.
One major challenge for wearable electronics is that the state‐of‐the‐art batteries are inadequate to provide sufficient energy for long‐term operations, leading to inconvenient battery replacement ...or frequent recharging. Other than the pursuit of high energy density of secondary batteries, an alternative approach recently drawing intensive attention from the research community, is to integrate energy‐generation and energy‐storage devices into self‐charging power systems (SCPSs), so that the scavenged energy can be simultaneously stored for sustainable power supply. This paper reviews recent developments in SCPSs with the integration of various energy‐harvesting devices (including piezoelectric nanogenerators, triboelectric nanogenerators, solar cells, and thermoelectric nanogenerators) and energy‐storage devices, such as batteries and supercapacitors. SCPSs with multiple energy‐harvesting devices are also included. Emphasis is placed on integrated flexible or wearable SCPSs. Remaining challenges and perspectives are also examined to suggest how to bring the appealing SCPSs into practical applications in the near future.
Self‐charging power systems (SCPSs) integrate energy‐harvesting and energy‐storage devices so that environmental energy can be in situ scavenged and stored for sustainable power supply of wearable electronics. Recent progress in wearable SCPSs integrated with piezoelectric nanogenerators, triboelectric nanogenerators, solar cells, thermoelectric nanogenerators, and hybrid energy‐harvesting devices is summarized.
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