Confined Assembly of Hollow Carbon Spheres in Carbonaceous Nanotube: A Spheres-in-Tube Carbon Nanostructure with Hierarchical Porosity for High-Performance Supercapacitor.

Carbonaceous nanotubes (CTs) represent one of the most popular and effective carbon electrode materials for supercapacitors, but the electrochemistry performance of CTs is largely limited by their relatively low specific surface area, insufficient usage of intratube cavity, low content of heteroatom, and poor porosity. An emerging strategy for circumventing these issues is to design novel porous CT-based nanostructures. Herein, a spheres-in-tube nanostructure with hierarchical porosity is successfully engineered, by encapsulating heteroatom-doping hollow carbon spheres into one carbonaceous nanotube (HCSs@CT). This intriguing nanoarchitecture integrates the merits of large specific surface area, good porosity, and high content of heteroatoms, which synergistically facilitates the transportation and exchange of ions and electrons. Accordingly, the as-prepared HCSs@CTs possess outstanding performances as electrode materials of supercapacitors, including superior capacitance to that of CTs, HCSs, and their mixtures, coupled with excellent cycling life, demonstrating great potential for applications in energy storage.

Straightforward Strategy Toward In Situ Water-Phase Exfoliation and Improved Interfacial Adhesion to Fabricate High-Performance Polypropylene/Graphene Nanocomposites.

Graphene is a potential candidate for achieving high-performance and multifunctional polypropylene (PP) composites. However, the complex manufacturing process and low dispersibility of graphene, as well as poor interfacial adhesion between graphene and polypropylene chains, stifle progress on large-scale production and applications of graphene/polypropylene composites. Here, we develop a strategy of maleic anhydride grafted polypropylene (MAPP) latex-assisted graphene exfoliation and melt blending to address the key challenges facing in industrial production. The surface property of the graphitic precursor is well-designed to achieve a high graphene exfoliation yield of ∼100% and induce abundant hydrogen bonding between the obtained mild-oxidized graphene (MOG) sheets and MAPP chains. Therefore, the MAPP-modified MOG can homogeneously disperse in the PP matrix and exhibits an excellent interfacial compatibility with the polymer. The addition of 5 wt % MOG results in simultaneous increase in the initial decomposition temperature, crystallization temperature, tensile strength, and Young's modulus by 43.2, 11.4 °C, 21.5, and 50.7%, respectively, and the electrical conductivity increases to 0.02 S·m-1. This work illustrates a practical solution to low-cost, eco-friendly, and feasible industrial production of graphene/PP composites through synchronous exfoliation and interfacial modification of graphene.

Accordion-like reduced graphene oxide embedded with Fe nanoparticles between layers for tunable and broadband electromagnetic wave absorption.

Electromagnetic wave absorbers constructed by reduced graphene oxide (rGO) and magnetic nanoparticles are extremely desirable for enhancing electromagnetic wave absorption performance due to the effective integration of the properties of dielectric and magnetic materials. However, the arrangement of graphene sheets and the growth of magnetic nanoparticles have always been challenging. Herein, an in-situ growth process has been used to successfully prepare accordion-like graphene with homogeneously distributed Fe nanoparticles in the confined structure via ion absorption and pyrolysis. The as-prepared Fe/layered rGO composites show excellent electromagnetic wave absorption performance with thin thickness, low filler loading, and broad effective absorption bandwidth (EAB). The minimum reflection loss of the composites achieves -54.6 dB with 20 wt% filler loading, and the tunable EAB reach 6.8 GHz (2.2 mm with 10 wt% filler loading) and 4.6 GHz (2.8 mm with 30 wt% filler loading), which can cover the entire Ku-band and X-band. The mechanism analysis indicates that the superior absorption performance is attributed to the multi-component loss mechanism, enhanced impedance matching degree and attenuation ability caused by the synergistic effect of layered rGO sheets and magnetic nanoparticles. This work opens up a new avenue for constructing accordion-like graphene-based composites as highly efficient electromagnetic wave absorbers.

Water transport facilitated by carbon nanotubes enables a hygroresponsive actuator with negative hydrotaxis.

Hygroresponsive actuators harness minor fluctuations in the ambient humidity to realize energy harvesting and conversion, thus they are of profound significance in the development of more energy-saving and sustainable systems. However, most of the existing hygroresponsive actuators are only adaptive to wet environments with limited moving directions and shape morphing modes. Therefore, it is highly imperative to develop a hygroresponsive actuator that works in both wet and dry environments. In this work, we present a bidirectional actuator responsive to both wet and dry stimuli. Our strategy relies on the introduction of carbon nanotubes to provide transport channels for water molecules. The actuation is enabled by the rapid transport of water in and out of the system driven by the moist/dry surroundings owing to the transport channels. The resultant actuator demonstrates reconfiguration and locomotion with turnover frequency F = 30 min-1, coupled with the capability of lifting objects 6 times heavier and transporting cargos 63 times heavier than itself. Oscillations (24°) driven by dry air flow in a cantilever display a high frequency (2 Hz) and large amplitude. Furthermore, a touchless electronic device was constructed to output varying signals in response to humid and dry environments. Our work provides valuable guidance and implications for designing and constructing hygroresponsive actuators, and paves the way for next-generation robust autonomous devices to exploit energy from natural resources.

Buckled Amorphous Hollow Carbon Spheres: Facile Fabrication, Buckling Process, and Applications as Electrode Materials for Supercapacitors.

Buckled hollow carbon nanospheres (BHCSs) integrate several attractive properties desired for a variety of potential applications. However, the development of a feasible and simple method for preparing BHCS nanoparticles remains a great challenge. Herein, we present a facile strategy for fabricating monodisperse BHCSs via the compression of intact hollow carbon nanospheres (HCSs) with improved mechanical strength. The essence of our strategy lies in the successful preparation of robust HCSs that can sustain large mechanical deformation during compression, based on the introduction of polyvinylpyrrolidone in the synthesis of HCS templates. Both experiments and finite element analyses are conducted to probe the deformation mechanism of buckling, suggesting that the residual stress introduced by pyrolysis of precursors plays a predominant role in the buckling process. Furthermore, the use of BHCSs as high-performance supercapacitors is demonstrated. Our work provides important insights into the engineering of robust amorphous carbon nanomaterials by the template method and mechanical modulation and provides an innovative synthetic strategy for fabricating asymmetric hollow spheres with potential for a diversity of applications.

A bio-inspired homogeneous graphene oxide actuator driven by moisture gradients.

An actuator driven by moisture gradients has been developed from a homogeneous graphene oxide film, relying on the in situ formation of a bilayer structure induced by water adsorption. This actuator shows efficient and controllable bending motions, coupled with the capability of lifting objects 8 times heavier than itself.