•Numerous conditions are used to prepare electropolymerized PEDOT/GO hybrids.•The compact microstructures of PEDOT are changed thoroughly by incorporating GO.•Different preparation conditions result ...in significantly different supercapacitive behaviors.•The PEDOT/GO hybrid obtained by optimized conditions exhibits superior properties.
Poly(3,4-ethylenedioxythiophene) (PEDOT) is known for compact morphology owing to dense growth, which limits its electrochemical capacitive properties. In this work, we have facilitated the dispersed growth of PEDOT by incorporating graphene oxide (GO) nanosheets, thus forming the PEDOT/GO hybrids via a facile electropolymerization route, in which GO nanosheets act as substrates with large specific area to load PEDOT coatings. The impact of electropolymerization modes and parameters on the supercapacitive properties of PEDOT/GO hybrids is studied in detail. Electrochemical measurements indicate that GO incorporation remarkably enhances the supercapacitive properties of PEDOT electrode. Among numerous preparation conditions, galvanostatically prepared electrode using 1 mA cm−2 presents the optimal supercapacitive properties, delivering an areal capacitance of 109.3 mF cm−2 at 0.5 mA cm−2 and retaining 95.1% of initial capacitance after 10,000 cycles. Such an electrode preserves the curly morphology of GO nanosheets and gives rise to more dispersed distribution for PEDOT coatings.
A novel strategy is proposed to obviously enhance the electrochemical capacitive properties of polypyrrole/graphene oxide/carbon nanotubes (PPy/GO/CNT) ternary composite. Here GO is treated by ...carboxylation reaction to obtain carboxyl graphene (CG). For comparison, PPy/GO/CNT and PPy/CG/CNT composites are synthesized with the same one-pot electro-co-deposition. Fourier transform infrared spectrometry, energy-dispersive X-ray spectroscopy, X-ray diffraction, scanning and transmission electron microscopy are carried out to characterize the composition and morphology of both composites. Unlike only utilizing the edged carboxyl groups on GO to combine with PPy coating, the current PPy/CG/CNT composite makes use of carboxyl groups distributed on basal planes and edges of CG nanosheets to combine with PPy. Accordingly, electrochemical measurements indicate that the PPy/CG/CNT electrodes markedly improve the supercapacitive properties compared to PPy/GO/CNT electrodes. The as-prepared PPy/CG/CNT composite electrodes show a high areal specific capacitance of 196.7 mF cm−2 at the current density of 0.5 mA cm−2 and superior rate capability, as well as achieve 98.1% of capacitance retention after 5000 CV cycles. The PPy/CG/CNT ternary composite we have developed holds promise for high-efficiency supercapacitor applications.
•PPy/CG/CNT ternary composite is synthesized by one-step electro-co-deposition.•CG provides more carboxyl as active sites for PPy polymerization compared with GO.•PPy/CG/CNT exhibits obviously boosted capacitive properties relative to PPy/GO/CNT.•PPy/CG/CNT shows high specific capacitance and excellent cycling stability.
Ternary composite electrodes based on carbon nanotubes thin films (CNFs)-loaded graphene oxide (GO) supported poly(3,4-ethylenedioxythiophene)- carbon nanotubes (GO/PEDOT-CNTs) have been prepared via ...a facile one-step electrochemical codeposition method. The effect of long and short CNTs-incorporated composites (GO/PEDOT-lCNTs and GO/PEDOT-sCNTs) on the electrochemical behaviors of the electrodes is investigated and compared. Electrochemical measurements indicate that the incorporation of CNTs effectively improves the electrochemical performances of the GO/PEDOT electrodes. Long CNTs-incorporated GO/PEDOT-lCNTs electrodes have more superior electrochemical behaviors with respect to the short CNTs-incorporated GO/PEDOT-lCNTs electrodes, which can be attributed to the optimized composition and specific microstructures of the former. To verify the feasibility of the prepared composite electrodes for utilization as flexible supercapacitor, a solid-state supercapacitor using the CNFs-loaded GO/PEDOT-lCNTs electrodes is fabricated and tested. The device shows lightweight, ultrathin, and highly flexible features, which also has a high areal and volumetric specific capacitance (33.4 m F cm−2 at 10 mV s−1 and 2.7 F cm−3 at 0.042 A cm−3), superior rate capability, and excellent cycle stability (maintaining 97.5% for 5000 cycles). This highly flexible solid-state supercapacitor has great potential for applications in flexible electronics, roll-up display, and wearable devices.
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•GO/PEDOT-CNTs ternary composites are prepared via a facile electrochemical method.•The long CNTs more effectively improve the capacitive performance of GO/PEDOT.•A lightweight and thin solid-state highly flexible supercapacitor is fabricated.•The supercapacitor device shows a high specific capacitance and cycle stability.
The recent discovery of the all‐boron fullerenes or borospherenes, D2d B40−/0, paves the way for borospherene chemistry. Here we report a density functional theory study on the viability of ...metalloborospherenes: endohedral M@B40 (M=Ca, Sr) and exohedral M&B40 (M=Be, Mg). Extensive global structural searches indicate that Ca@B40 (1, C2v, 1A1) and Sr@B40 (3, D2d, 1A1) possess almost perfect endohedral borospherene structures with a metal atom at the center, while Be&B40 (5, Cs, 1A′) and Mg&B40 (7, Cs, 1A′) favor exohedral borospherene geometries with a η7‐M atom face‐capping a heptagon on the waist. Metalloborospherenes provide indirect evidence for the robustness of the borospherene structural motif. The metalloborospherenes are characterized as charge‐transfer complexes (M2+B402−), where an alkaline earth metal atom donates two electrons to the B40 cage. The high stability of endohedral Ca@B40 (1) and Sr@B40 (3) is due to the match in size between the host cage and the dopant. Bonding analyses indicate that all 122 valence electrons in the systems are delocalized as σ or π bonds, being distributed evenly on the cage surface, akin to the D2d B40 borospherene.
Into higher spheres: The recently observed B40 borospherene is predicted to be capable of hosting a metal atom inside (M@B40; M=Ca, Sr) or coordinating one on its heptagonal surface (M&B40; M=Be, Mg). Metalloborospherenes are charge‐transfer M2+B402− complexes, demonstrating the structural and electronic integrity of borospherene, akin to C60 buckyball.
A 17-electron CBe5H4+ cluster features planar pentacoordinate carbon, owing to the 2π/6σ double aromaticity. The neutral CBe5H4 cluster has a tetrahedral configuration despite its 18-electron ...counting. The latter species is governed by σ conjugation.
Flexible electrodes of ternary composites, in which highly conductive carbon nanotube films (CNFs) are coated with carbon nanotube-doped graphene oxide/polypyrrole (CNT-GO/PPy), have been fabricated ...via facile electrochemical synthesis. Long and short CNTs are separately doped into the composites (lCNT-GO/PPy and sCNT-GO/PPy) and their electrochemical performances are compared. Electrochemical measurements indicate that the doping of CNTs in the composites significantly improves the electrochemical behaviors of the GO/PPy electrodes. Notably, the lCNT-GO/PPy electrodes show superior electrochemical properties with respect to the sCNT-GO/PPy electrodes, which is related to the introduction of abundant CNTs in the former electrodes and their special microstructures. Two symmetric electrodes with the lCNT-GO/PPy composites coated on CNFs are assembled to fabricate a solid-state supercapacitor device, which features lightweight, ultrathinness, and high flexibility. The device achieves a high areal and volumetric specific capacitance of 70.0 mF cm−2 at 10 mV s−1 and 6.3 F cm−3 at 0.043 A cm−3, respectively. It also shows superior rate performance and cycle stability, with a capacitance retention rate of 87.7% for 10,000 cycles. The supercapacitor device fabricated is promising for the use in lightweight and flexible integrated electronics.
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•CNT-GO/PPy ternary composites have been prepared by one-pot electropolymerization.•The supercapacitive performance of GO/PPy is remarkably improved by doping CNTs.•A light and thin highly flexible solid-state supercapacitor has been fabricated.•The supercapacitor presents a high specific capacitance and cycle stability.
Two low‐lying structures are unveiled for the Be6B11− nanocluster system that are virtually isoenergetic. The first, triple‐layered cluster has a peripheral B11 ring as central layer, being ...sandwiched by two Be3 rings in a coaxial fashion, albeit with no discernible interlayer Be−Be bonding. The B11 ring revolves like a flexible chain even at room temperature, gliding freely around the Be6 prism. At elevated temperatures (1000 K), the Be6 core itself also rotates; that is, two Be3 rings undergo relative rotation or twisting with respect to each other. Bonding analyses suggest four‐fold (π and σ) aromaticity, offering a dilute and fluxional electron cloud that lubricates the dynamics. The second, helix‐type cluster contains a B11 helical skeleton encompassing a distorted Be6 prism. It is chiral and is the first nanosystem with a boron helix. Molecular dynamics also shows that at high temperature the helix cluster readily converts into the triple‐layered one.
Fluxional or helical: The Be6B11− cluster is calculated to adopt two competitive conformations. The coaxial triple‐layered cluster mimics the earth–moon system, featuring three‐dimensional structural fluxionality and dual dynamic modes (revolution versus rotation). The helix‐type cluster is the first boron helix; the highly charged boron core presumably governs the helical arrangement.
We report a σ + π double aromatic CB5S5+ cluster, the first global minimum unusually having a planar hypercoordinate carbon inside a boron wheel. Five peripheral sulfur atoms stabilize the ...carbon-centered boron wheel by weakening the electron deficiency of the boron atoms through strong S → B π back-bonding.
Boron-based complex clusters are a fertile ground for the exploration of exotic chemical bonding and dynamic structural fluxionality. Here we report on the computational design of a ternary MgTa2B6 ...cluster via global structural searches and quantum chemical calculations. The cluster turns out to be a new member of the molecular rotor family, closely mimicking a turning clock at the subnanoscale. It is composed of a hexagonal B6 ring with a capping Ta atom at the top and bottom, whereas the Mg atom is linked to one Ta site as a radial Ta–Mg dimer. These components serve as the dial, axis, and hand of a nanoclock, respectively. Chemical bonding analyses reveal that the inverse sandwich Ta2B6 motif in the cluster features 6π/6σ double aromaticity, whose electron counting conforms to the (4n + 2) Hückel rule. The Ta–Mg dimer has a Lewis-type σ bond, and the Mg site has negligible bonding with B6 ring. The ternary cluster can be formulated as an Mg0Ta2B60 complex. Molecular dynamics simulations suggest that the cluster is structurally fluxional analogous to a nanoclock, even at a low temperature of 100 K. The Ta–Mg hand turns almost freely around the Ta2 axis and along the B6 dial. The tiny intramolecular rotation barrier is less than 0.3 kcal mol−1, being dictated by the bonding nature of double 6π/6σ aromaticity. The present system offers a new type of molecular rotor in physical chemistry.
Boron-based clusters possess unusual structural and bonding properties owing to boron's electron-deficiency. We report on the theoretical prediction of two binary B–Na clusters, Na6B7− and Na8B7+, ...which assume unique sandwich geometries, featuring a perfectly planar B7 wheel and two triangular Na3 or quasi-tetrahedral Na4 ligands. Despite distinct electronegativities of B/Na, the B–Na clusters do not form typical salts. Both sandwich species are dynamically fluxional at 300 K and beyond. Two dynamic modes are observed: an in-plane rotation of the B7 wheel versus twisting of the two Na3/Na4 ligands. Their energy barriers are negligibly small. Natural bond orbital calculations show that the clusters are charge-transfer complexes Na3+B73−Na3+ and Na42+B73−Na42+, respectively. Chemical bonding analyses indicate that the B7 wheel in the clusters has 6π/6σ double aromaticity and the Na3/Na4 ligands are 2σ aromatic, collectively leading to four-fold π/σ aromaticity. The quasi-tetrahedral Na4 ligand is the simplest example of spherical aromaticity and can also be considered a superatom. Interlayer bonding in the sandwiches is greater than 20 eV, due to electrostatics, which should not be confused with weakly bound species. Four-fold π/σ aromaticity and robust interlayer ionic bonding offer uniform and dilute electron clouds over the sandwiches, facilitating their dual-mode dynamic fluxionality. The Na8B7+ cluster is also a superalkali cation.
