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The fundamental requirements of self-powered hydrogels used in flexible electronic products encompass excellent mechanical performance and conductivity. However, simultaneously achieving high performance in both the aspects remains a great challenge during the fabrication of self-powered hydrogels. In this study, robust and recyclable self-powered polysaccharide-reinforced polyvinyl alcohol (PVA) networks were established by modulating ionic channels using Zn2+/Li+ bimetallic salt solutions. The results indicate that the hydrogel equilibrated in a bimetallic salt solution of 1 M concentration can simultaneously achieve an impressive tensile strength of 1.36 MPa and an optimal ionic conductivity of 1.64 S m−1 since carboxyl groups on the polysaccharide chains enable the adsorption of more metal ions without restricting ionic mobility as a result of higher conductivity. By leveraging their excellent electrochemical performance, conductive hydrogels can serve not only as flexible sensing materials with enhanced sensitivity to monitor human motion and facilitate information transmission, but also as recyclable electrolytes in self-powered hydrogel batteries. Interestingly, self-powered hydrogel batteries can maintain a stable voltage of 0.82 V and show good recyclability, which can restore the original voltage output via a simple salt solution equilibration method, offering significant potential in applications such as wilderness survival. This work provides a novel strategy for the rapid and green preparation of robust, recyclable, and self-powered polysaccharide-based hydrogels. [ABSTRACT FROM AUTHOR]

Next-generation wearable electronics yearn for sensitive components with cost-effectiveness, flexibility, sensitivity, and multi-functionality. In this work, an ultra-stretchable dual-mode strain/tactile sensor with high sensitivity and a wide detection range is developed on a permeable olefin block copolymer (OBC) nonwoven substrate, which manifests outstanding capabilities for monitoring human motions and presenting the shape of various sounds. A skin-friendly OBC elastomer is first electrospun into a highly elastic fibrous matrix; CNTs are subsequently incorporated in the OBC microfibers firmly and homogeneously via a versatile sonication-assisted assembly, achieving a highly elastic fibrous conductor with superior piezoresistive sensing performance under both stretching and pressing. Specifically, an extremely low detection limit (0.074%), an ultrawide sensing range (0.074–350%), and a fast response time (107 ms) are obtained when the fibrous conductor is utilized as a strain sensor. Moreover, a wide response range (0–70 kPa), a high sensitivity (0.073 kPa−1), and fast response/recovery times (30 ms/60 ms) are also achieved when it is applied as a tactile sensor. Thus, the dual-mode strain/tactile sensor is capable of monitoring a wide range of human activities ranging from subtle deformations to vigorous body movements. More excitingly, a wireless sound detector developed based on the dual-mode sensor can readily differentiate a range of natural sounds through air pressure sensing, exhibiting enormous potential in sound visualization technology. [ABSTRACT FROM AUTHOR]

Conductive elastomer composites are widely recognized as prospective strain sensing materials in soft robotics and biomedical engineering due to their high elasticity and light weight. However, achieving high-performance strain sensors with a broad sensing range and high gauge factor synchronously is still challenging due to the trade-off between sensitivity and stretchability. In this work, an anisotropic fiber film-based strain sensor with extraordinary dual-mode sensing capabilities was developed using highly aligned styrene-block-poly(ethylene-ran-butylene)-block-poly-styrene (SEBS)/PEO–PPO–PEO triblock copolymer (F127) fiber films as an anisotropic elastomer matrix and intimately incorporated multiwall carbon nanotubes (CNTs) as a deformable conductive coating. Via blending F127 with SEBS to endow the elastomer with superhydrophilicity, aligned electrospinning was subsequently employed to prepare highly stretchable and hydrophilic SEBS/F127 fiber films, followed by surface-induced assembly to obtain anisotropic CNT/SEBS/F127 composite fiber films equipped with an adaptive deformable CNT conducting layer. Attributed to the strong interfacial interaction between CNTs and the anisotropic fiber matrix, the obtained CNT/SEBS/F127 sensor exhibited excellent mechanical strength and exceptional dual-mode strain-sensing performance in terms of an ultra-broad response range (up to 1300% strain) and an ultra-high sensitivity (GF value of 3564 at 700% strain) when stretching parallel and perpendicular to the fiber alignment, respectively, as well as fast response/recover times (51 ms/71 ms in parallel, and 100 ms/100 ms in perpendicular) and great sensing stabilities (5000 stretching–releasing cycles) in both loading directions. Additionally, the CNT/SEBS/F127 strain sensor was able to detect various human motions, such as breathing, phonation and joint bending, presenting great potential in next-generation wearable electronics. [ABSTRACT FROM AUTHOR]

Rationally designing and engineering electrodes with multiple components and favorable architectures is an effective way to modulate their electrochemical performance. Here, we present the tailored synthesis of a novel 3D macroporous electrode with hierarchical lollipop-like MnCo2S4/FeCo2S4 heterostructures immobilized on a flexible N-doped carbon matrix, which delivers a high specific capacitance of 2806 F g−1 (capacity of 1403 C g−1) at 1 A g−1 and excellent cycling stability (85.1% of its initial value after 5000 cycles). Moreover, a hybrid supercapacitor device based on the self-supported MnCo2S4/FeCo2S4/N-CMF electrode achieves a high energy density of 87.3 W h kg−1 at a power density of 799.9 W kg−1 and great electrochemical stability under bending conditions. This remarkable capacitive performance is attributed to the collaborative contribution from three components involving the enhanced charge transfer on the 3D interconnected carbon matrix, the unique ion-diffusion "short-cuts" provided by the hollow interior of the carbon skeleton, the abundant void space and electroactive sites in sheet-built MnCo2S4 spheres and rough FeCo2S4 nanoneedles, and great structural stability of firmly connected MnCo2S4/FeCo2S4 "lollipops". Thus, this work offers insight into the rational construction of transition metal sulfide complexes for next-generation high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Active CoMoV LDH nanosheet arrays grown on nickel foam were obtained for the first time. The doping of high-valence Mo and V in the Co-based LDH could tune the electronic structure and keep Co in a high-valence state for the OER, and high-valence Mo could also act as the active site for the HER, thus obtaining superior bifunctional water splitting performance. [ABSTRACT FROM AUTHOR]

Controllable synthesis of uniform graphene–metal oxide nanocomposites is of great interest in energy storage applications, due to the combination of their merits and the synergistic effects on the enhancement of their electrochemical performance. Herein, we report a controllable synthesis of uniform mesoporous H-Nb2O5/rGO nanocomposites, which exhibit higher reversible specific capacity (∼190 mA h g−1), and better rate capability and cycling stability (the capacitance retention is 96.5% over 500 cycles) than pristine H-Nb2O5 microflowers, attributed to their large specific surface area (364.17 m2 g−1), porous structure, and intimate interface. More remarkably, the H-Nb2O5/rGO-based lithium ion hybrid supercapacitor (LIHS) delivered a high energy density of 100.2 W h kg−1 at 50 W kg−1 and still retained 18.3 W h kg−1 at an ultrahigh power density of 20 000 W kg−1, as well as an excellent cycling stability. It is worth noting that some other nanocomposites, including Zn2Ti3O8/rGO, Si/rGO, NaNbO3/rGO, Nb4N5/rGO, and H-Nb2O5/2D g-C3N4, have also been successfully synthesized by this method, demonstrating that it can be extended to prepare other functional nanocomposites for applications in energy conversion and storage, photocatalytic hydrogen production, sensors, and so on. [ABSTRACT FROM AUTHOR]

A 3D hierarchical NiCo2O4/PANI/MF composite foam with a macroporous 3D skeleton, a conductive PANI coating and highly electrochemically active NiCo2O4 nanosheets is synthesized as a lightweight and low-cost electrode material. Due to the collaborative contribution of all the components, the prepared composite foam exhibits excellent capacitive performances when incorporated into an asymmetric supercapacitor. [ABSTRACT FROM AUTHOR]

Bifunctional electrocatalysts, which are active both for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), can increase the efficiency of overall water splitting, which is considered an attractive technology for hydrogen production. In this study, we report NiCo-LDH ultrathin nanosheets grown on nickel foam as a bifunctional electrocatalyst for overall water splitting. When used as OER and HER electrodes, NiCo-LDH/NF demonstrated excellent water splitting performance, achieving a current density of 10 mA cm−2 at 1.66 V. Thus, the synthesis of hierarchical 3D porous structure composed of 2D ultrathin nanosheets in NiCo-LDH/NF demonstrated the significance of structural features for achieving a high electrocatalytic activity in overall water splitting. [ABSTRACT FROM AUTHOR]

As a novel kind of carbon-based material, carbon aerogels have attracted widespread attention owing to their integrated properties of a large internal surface area, small pore size, and outstanding mechanical strength. In this study, a fascinating carbon aerogel has been rationally designed with a unique cellular structure, consisting of one-dimensional carbon nanofibers derived from oxidized polyacrylonitrile (o-PAN) and two-dimensional carbon sheets originating from polyimide (PI). The interconnected o-PAN/PI (oPP) carbon aerogel exhibits low density but increased mechanical strength and can not only act as a versatile adsorbent but also as an ideal template for the in situ growth of MnO2 nanosheets to obtain oPP@MnO2 hybrid carbon aerogel. The oPP@MnO2 composite aerogel exhibits extraordinary electrochemical characteristics with a maximum specific capacitance of 1066 F g−1, approaching the theoretical value (1370 F g−1) of MnO2. Moreover, an assembled oPP@MnO2//activated oPP (A-oPP) asymmetric supercapacitor delivers a considerably high energy density of up to 30.3 W h kg−1, highlighting the advantages of the unique cellular structure of the oPP carbon aerogel and oPP@MnO2 hybrid carbon aerogel. Therefore, the successful fabrication of the oPP carbon aerogel widens the scope of traditional electrospun lamellar membranes to multi-dimensional aerogels, providing a new strategy for the construction of nanofiber-based materials for energy storage and environmental protection applications. [ABSTRACT FROM AUTHOR]

Dopamine is an excellent and flexible agent for surface coating of various materials, with the high-concentration of amine groups serving as a facile stabilizer for some metallic nanoparticles. In this work, mesoporous composites of nitrogen-doped carbon fibers (NCFs) decorated with cobalt nanoparticles have been successfully fabricated via the combination of a mussel-inspired biomimetic polydopamine (PDA)-coating process using electrospun porous polystyrene fibers as templates, a simple solution deposition method and subsequent high-temperature carbonization. This rationally designed porous NCF–Co composite possesses a large surface area and numerous electrochemically active sites, which exhibits synergistically improved catalytic activity for oxygen reduction reactions (ORRs) with a relatively positive onset potential, large current density, as well as superior durability compared with the commercial platinum–carbon (Pt/C) catalyst, making it a promising noble-metal-free catalyst for practical ORR applications. [ABSTRACT FROM AUTHOR]

Maximizing the number of exposed active edges in newly emerged two-dimensional few-layer MoSe2 nanostructures is a key issue to fully realize the excellent electrochemical properties of MoSe2. In this work, a SnO2@MoSe2 nanostructure was successfully fabricated through a facile electrospinning technique combined with sintering and a solvothermal method. This rationally designed hierarchical architecture has perpendicularly oriented few-layered MoSe2 nanosheets uniformly and fully covering both inner and outer surfaces of SnO2 nanotubes, which exhibits excellent electrochemical activity as a hydrogen evolution reaction (HER) catalyst with a small onset potential of −0.11 V vs. reversible hydrogen electrode (RHE) and a small Tafel slope of 51 mV per decade. This excellent performance may originate from the unique hierarchical tubular structure with fully exposed active edges and open spaces for fast electron/electrolyte transfer, enabling their potential to replace Pt as a future electrocatalyst in HER. [ABSTRACT FROM AUTHOR]

Removal of hazardous metal ions from industrial wastewater is of paramount importance. Taking advantage of the metal–ligand binding specificity and electrospun nanofibers with a high surface area to volume ratio and a porous structure, we developed thymine (T)-grafted poly(vinyl alcohol) (PVA)–polyethyleneimine (PEI) nanofibers for selective removal of mercury ions (Hg2+) with high efficiency. In this study, thymine-1-acetic acid was first grafted with the primary surface amines of branched PEI via a 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide coupling reaction. The formed PEI–T conjugate was mixed with PVA solution for subsequent formation of T-grafted electrospun PVA–PEI (PVA–PEI-T) nanofibers. The formed PEI–T conjugate and the crosslinked PVA–PEI-T nanofibers were characterized via different techniques. We show that the grafting of the T moieties onto the surface of PEI does not appreciably impact the smooth fibrous morphology of PVA–PEI-T nanofibers when compared with the PVA–PEI nanofibers without T grafting, except that the T-grafted fibers have slightly increased fiber diameter. With the grafting of T moieties, the formed PVA–PEI-T nanofibers enabled selective removal of Hg2+ from aqueous solution and improved removal efficiency was able to be achieved by increase of the T-grafting density on the PEI surface. With the good reusability for repetitive Hg2+ removal, the newly developed T-functionalized PVA–PEI nanofibers may hold a great promise for high-selectivity and high-efficiency removal of Hg2+ from laboratory and industrial wastes. [ABSTRACT FROM AUTHOR]

We report here a facile approach to assembling low generation poly(amidoamine) (PAMAM) dendrimer-stabilized gold nanoparticles (Au DSNPs) onto electrospun polymer nanofibrous mats for catalytic applications. In this study, Au DSNPs formed using amine-terminated generation 2 PAMAM dendrimers as stabilizers were assembled onto electrospun polyacrylic acid (PAA)/polyvinyl alcohol (PVA) nanofibrous mats either through electrostatic interactions or through the covalent 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) coupling reaction. The assembly of Au DSNPs with a mean diameter of 5.4 nm onto the electrospun nanofibrous mats was characterized via different techniques. The catalytic activity of the Au DSNP-assembled nanofibrous mats was evaluated by the transformation of 4-nitrophenol to 4-aminophenol. We show that both approaches enable the efficient assembly of Au DSNPs onto nanofiber surfaces and the as prepared Au DSNP-containing nanofibers formed via both approaches have excellent catalytic activity and reusability. However, the Au DSNP-assembled nanofibers via electrostatic physical interactions display a much higher catalytic activity than those formed via the chemical assembly approach. The facile dendrimer-mediated assembly approach to modifying electrospun nanofibers may be used to fabricate other composite nanofiber systems for applications in catalysis, sensing, and biomedical sciences. [ABSTRACT FROM AUTHOR]

A 3D hierarchical NiCo2O4/PANI/MF composite foam with a macroporous 3D skeleton, a conductive PANI coating and highly electrochemically active NiCo2O4 nanosheets is synthesized as a lightweight and low-cost electrode material. Due to the collaborative contribution of all the components, the prepared composite foam exhibits excellent capacitive performances when incorporated into an asymmetric supercapacitor.

Bifunctional electrocatalysts, which are active both for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), can increase the efficiency of overall water splitting, which is considered an attractive technology for hydrogen production. In this study, we report NiCo-LDH ultrathin nanosheets grown on nickel foam as a bifunctional electrocatalyst for overall water splitting. When used as OER and HER electrodes, NiCo-LDH/NF demonstrated excellent water splitting performance, achieving a current density of 10 mA cm -2 at 1.66 V. Thus, the synthesis of hierarchical 3D porous structure composed of 2D ultrathin nanosheets in NiCo-LDH/NF demonstrated the significance of structural features for achieving a high electrocatalytic activity in overall water splitting.