Cu-exchanged small-pore zeolites (CHA and AEI) form methanol from methane (>95% selectivity) using a 3-step cyclic procedure (Chem. Commun.20155144474450) with methanol amounts higher than Cu-ZSM-5 and Cu-mordenite on a per gram and per Cu basis. Here, the Cu x O y species formed on Cu-SSZ-13 and Cu-SSZ-39 following O2 or He activation at 450 °C are identified as trans-μ-1,2-peroxo dicopper­(II) ([Cu2O2]2+) and mono-(μ-oxo) dicopper­(II) ([Cu2O]2+) using synchrotron X-ray diffraction, in situ UV–vis, and Raman spectroscopy and theory. [Cu2O2]2+ and [Cu2O]2+ formed on Cu-SSZ-13 showed ligand-to-metal charge transfer (LMCT) energies between 22,200 and 35,000 cm–1, Cu–O vibrations at 360, 510, 580, and 617 cm–1 and an O–O vibration at 837 cm–1. The vibrations at 360, 510, 580, and 837 cm–1 are assigned to the trans-μ-1,2-peroxo dicopper­(II) species, whereas the Cu–O vibration at 617 cm–1 (Δ18O = 24 cm–1) is assigned to a stretching vibration of a thermodynamically favored mono-(μ-oxo) dicopper­(II) with a Cu–O–Cu angle of 95°. On the basis of the intensity loss of the broad LMCT band between 22,200 and 35,000 cm–1 and Raman intensity loss at 571 cm–1 upon reaction, both the trans-μ-1,2-peroxo dicopper­(II) and mono-(μ-oxo) dicopper­(II) species are suggested to take part in methane activation at 200 °C with the trans-μ-1,2-peroxo dicopper­(II) core playing a dominant role. A relationship between the [Cu2O y ]2+ concentration and Cu­(II) at the eight-membered ring is observed and related to the concentration of [CuOH]+ suggested as an intermediate in [Cu2O y ]2+ formation.

conventional 3D and 2D types when used for miniaturized electronic devices, textile electronics, and implantable medical devices. [1,2] However, compared with other energy storage devices such as batteries, the much lower stored specific energy of 1D supercapacitors limited their practical applications. Since the energy stored in a supercapacitor is proportional to CV 2 (E = 1/2 CV 2 , where C is the capacitance of the device and V is the operating voltage), enhancements in energy density can be achieved by increasing the specific capacitance (C) or widening the operating voltage range (V). [3] Specific capacitance can be improved by the incorporation of electrochemically active nanomaterials (e.g., metal oxides or conducting polymers) into the base electrode materials, such as carbon nanotube (CNT) or graphene assemblies. In comparison, insufficient attention has been paid to improve the voltage range of flexible supercapacitors. This is especially true in fiber-shaped supercapacitors (FSSs), which usually show ideal capacitive behavior only in a relatively small potential window (0.8-1.0 V), [4][5][6][7][8][9][10][11][12][13][14] and consequently deliver limited energy or power densities. An effective approach for addressing this issue is the strategy of asymmetric electrode configuration by coupling different positive and negative electrode materials with well-separated potential windows for achieving a high operating voltage. [15][16][17][18] So far, several papers addressing asymmetric FSS can be found in the literature. A fiber-based flexible all-solid state asymmetric supercapacitor using molybdenum disulfide (MoS 2 )-reduced graphene oxide (rGO)/multiwalled carbon nanotube (MWCNT) and rGO/MWCNT fibers has accomplished a potential window of 1.4 V with high Coulombic efficiency and improved energy density. [19] Cheng et al. reported an asymmetric fiber-shaped supercapacitor based on MnO 2 /conducting polymer/CNT fiber and ordered microporous carbon/ CNT hybrid fiber as positive and negative electrode, respectively, which produced a high energy density of 11.3 mW h cm −3 . [20] Yang et al. fabricated a fiber-shaped asymmetric supercapacitor by using porous NiO/Ni(OH) 2 /PEDOT/contra wire electrode as the positive electrode, and the ordered mesoporous carbon fiber as the negative electrode. The supercapacitor exhibited an output voltage of 1.5 V. [21] Wang et al. used titanium wire/cobalt oxide (Co 3 O 4 ) nanowires and carbon fibers/graphene electrodes to fabricate an asymmetric supercapacitor, which enhanced both stored energy and delivered power by at least 1860% compared with that of the supercapacitor with a potential window The emerging fiber-shaped supercapacitors (FSSs) have motivated tremendous research interest in energy storage devices. However, challenges still exist in the pursuit of combination of excellent electrochemical performance and mechanical stretchability. Here, a core-sheath asymmetric FSS is first made by wrapping gel electrolyte coated carbon nanotube (CNT)@MnO 2 core fiber with CNT@...

The emergence of stretchable electronic devices has attracted intensive attention. However, most of the existing stretchable electronic devices can generally be stretched only in one specific direction and show limited specific capacitance and energy density. Here, we report a stretchable isotropic buckled carbon nanotube (CNT) film, which is used as electrodes for supercapacitors with low sheet resistance, high omnidirectional stretchability, and electro-mechanical stability under repeated stretching. After acid treatment of the CNT film followed by electrochemical deposition of polyaniline (PANI), the resulting isotropic buckled acid treated CNT@PANI electrode exhibits high specific capacitance of 1147.12 mF cm(-2) at 10 mV s(-1). The supercapacitor possesses high energy density from 31.56 to 50.98 μWh cm(-2) and corresponding power density changing from 2.294 to 28.404 mW cm(-2) at the scan rate from 10 to 200 mV s(-1). Also, the supercapacitor can sustain an omnidirectional strain of 200%, which is twice the maximum strain of biaxially stretchable supercapacitors based on CNT assemblies reported in the literature. Moreover, the capacitive performance is even enhanced to 1160.43-1230.61 mF cm(-2) during uniaxial, biaxial, and omnidirectional elongations.

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