Fiber nanomaterials can become fundamental devices that can be woven into smart textiles, for example, miniaturized fiber-based supercapacitors (FSCs). They can be utilized for portable, wearable electronics and energy storage devices, which are highly prospective areas of research in the future. Herein, we developed porous carbon nanotube–graphene hybrid fibers (CNT–GFs) for all-solid-state symmetric FSCs, which were assembled through wet-spinning followed by a hydrothermal activation process using environmentally benign chemicals (i.e., H2O2 and NH4OH in deionized water). The barriers that limited effective ion accessibility in GFs were overcome by the intercalation of CNTs in the GFs which enhanced their electrical conductivity and mechanical properties as well. The all-solid-state symmetric FSCs of a precisely controlled activated hybrid fiber (a-CNT–GF) electrode exhibited an enhanced volumetric capacitance of 60.75 F cm–3 compared with those of a pristine CNT–GF electrode (19.80 F cm–3). They also showed a volumetric energy density (4.83 mWh cm–3) roughly 3 times higher than that of untreated CNT–GFs (1.50 mWh cm–3). The excellent mechanical flexibility and structural stability of a miniaturized a-CNT–GF are highlighted by the demonstration of negligible differences in capacitance upon bending and twisting. The mechanism of developing porous, large-scale, low-cost electrodes using an environmentally benign activation method presented in this work provides a promising route for designing a new generation of wearable, portable miniaturized energy storage devices.

Confining molecules in the nanoscale environment can lead to dramatic changes of their physical and chemical properties, which opens possibilities for new applications. There is a growing interest in liquefied gas electrolytes for electrochemical devices operating at low temperatures due to their low melting point. However, their high vapor pressure still poses potential safety concerns for practical usages. Herein, we report facile capillary condensation of gas electrolyte by strong confinement in sub-nanometer pores of metal-organic framework (MOF). By designing MOF-polymer membranes (MPMs) that present dense and continuous micropore (~0.8 nm) networks, we show significant uptake of hydrofluorocarbon molecules in MOF pores at pressure lower than the bulk counterpart. This unique property enables lithium/fluorinated graphite batteries with MPM-based electrolytes to deliver a significantly higher capacity than those with commercial separator membranes (~500 mAh g−1 vs. <0.03 mAh g−1) at −40 °C under reduced pressure of the electrolyte.

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CommuniCation(1 of 6) 1600401 mechanical performance is limited compared to commercial carbon fibers. Here, we present a straightforward fabrication method to produce GO fibers with LC solution of GO using trivalent cation salts as an ionic binder. To utilize the full potential of GO fiber, it is critically important to control the microstructure of fiber. The microstructure of GO fibers, such as shape and d-spacing between sheets, is ultimately controlled by the metal cation coagulants which are then processed into a fiber. Given the advantages of LC-GO, the resulting microstructure dominates most of the fiber mechanical properties (stiffness, strength, strain, etc.), and consequently its control in the early stage is regarded as a key method to achieve high mechanical performance. The underlying advantage is that trivalent metal cations modulate chemical interactions between GO sheets and drive ion cross-linking, which improves mechanical properties remarkably.To see the effect of GO coagulation with multivalent cation binders, Co 2+ , Al 3+ , and Fe 3+ were considered. Well dispersed GO was prepared as described in the Experimental Section and was observed by atomic force microscopy (AFM) topography and the thickness of GO sheets were measured as 1.2 nm (Figure 1a). GO aqueous dispersions were prepared by dispersing GO powders in deionized water (DIW) by mild sonication (Figure 1b). Dispersed GO solutions (1.0 mg mL −1 ) were kept stationary between two crossed polarizers and their LC phases were characterized with the observation of the textures of nematic LC. As presented in Figure 1c, GO dispersion showed the optical birefringence morphology; dark and bright brushes were interwoven, signifying a nematic LC phase. This phase implies that the anisotropic particles are well dispersed within the dispersing media without aggregates, which is largely resulted from electrostatic repulsion. [1,[17][18][19] To observe the changes of LC-GO in the presence of cations, different metal salts were added at a concentration of 20 × 10 −3 m. The addition of cations eventually disrupted dense LC patterns. Interestingly, it was still possible to observe the birefringence effect. This observation indicates that the multivalent cation acts as an ionic binder for the GO and the dispersion formed stacked crystalline-like GO sheets.The prepared GO dispersions were spun and the dispersions gelated in the coagulation bath. The cations which diffuse into the inner structure of the GO gel undergo electrostatic attraction with the negative charge of GO's oxygen functional groups, leading to bonding in the basal planes. [20] Furthermore, the coordination bonds between the GO and metal cations act as bridges between the sheet edges. [21][22][23] The GO gels immobilized by cation binder are pulled out of the coagulation bath and continuously coiled along the reel. Drafting was not performed

In this work, a novel graphene quantum dot/iron phthalocyanine conjugate is synthesized. This hybrid material show efficient electrocatalytic activityviafour electron reaction and distinguished tolerance toward methanol and CO.

Selective electrochemical oxygen reduction (ORR) toward a two-electron (2e À ) pathway is an eco-friendly alternative method for H 2 O 2 synthesis to replace the energy-intensive anthraquinone oxidation process. Carbon-based electrocatalysts (CBEs) show great potential for practical H 2 O 2 synthesis. However, their complex structures make it challenging to determine the nature of active sites and to precisely control them. Herein, we show that precise modulation of the chemistry and structures of holey graphene with edge sites enriched by oxygen-containing functional groups can facilitate 2e À ORR. These combined functionalities could improve ORR performance under various pH conditions, for example, resulting in an average of 95% H 2 O 2 selectivity, ~97% Faraday efficiency, high productivity of 2360 mol kg cat À1 h À1 in alkaline media. Density functional theory calculations on the oxygen functional groups at the edge sites revealed the most active site for 2e À ORR is a synergy between ether (C O C) and carbonyl (C O) functional groups with nearly zero overpotential.

Nitrogen (N) and oxygen (O) doping for carbon-based electrocatalysts is one of the most effective methods for improving the oxygen reduction reaction (ORR). Despite its significance, fundamental studies remain needed to determine the effects of atomic configuration on the two-electron (2e − ) oxygen reduction. In this study, we investigate the coupling effects between pyrrolic N and the O functional groups, including ether (O−C−O) and carbonyl (CO), on 2e − ORR. The results suggest that the 2e − ORR performance depends on the CO/O−C−O ratio. Among several atomic configurations, the coupling of pyrrolic N with carbonyl O is the most favorable type for the 2e − reaction, with 98.3% H 2 O 2 selectivity at 0.0 V (vs the reversible hydrogen electrode) in the alkaline electrolyte. Additionally, this combination exhibits considerably stable performance during long-term (12 h) durability test, demonstrating approximately 100% current retention. The experimental results were further supported by theoretical calculation, exhibiting optimal adsorption free energy of OOH* for the couple of pyrrolic N and carbonyl O.

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