Highly porous nitrogen-doped carbon nanomaterials have distinct advantages in energy storage and conversion technologies. In the present work, hydrothermal treatments in water or ammonia solution were used for modification of mesoporous nitrogen-doped graphitic carbon, synthesized by deposition of acetonitrile vapors on the pyrolysis products of calcium tartrate. Morphology, composition, and textural characteristics of the original and activated materials were studied by transmission electron microscopy, X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, infrared spectroscopy, and nitrogen gas adsorption method. Both treatments resulted in a slight increase in specific surface area and volume of micropores and small mesopores due to the etching of carbon surface. Compared to the solely aqueous medium, activation with ammonia led to stronger destruction of the graphitic shells, the formation of larger micropores (1.4 nm vs 0.6 nm), a higher concentration of carbonyl groups, and the addition of nitrogen-containing groups. The tests of nitrogen-doped carbon materials as electrodes in 1M H2SO4 electrolyte and sodium-ion batteries showed improvement of electrochemical performance after hydrothermal treatments especially when ammonia was used. The activation method developed in this work is hopeful to open up a new route of designing porous nitrogen-doped carbon materials for electrochemical applications.
We
identify the “missing” 1D-phosphorus allotrope,
red phosphorus chains, formed in the interior of tip-opened single-walled
carbon nanotubes (SWCNTs). Via a comprehensive experimental and theoretical
study we show that in intermediate diameter cavities (1.6–2.9
nm), phosphorus vapor condenses into linear P8]P2 chains and fibrous
red-phosphorus type cross-linked double-chains. Thermogravimetric
and X-ray photoelectron spectroscopy analysis estimates ∼7
atom % of elemental phosphorus in the sample, while high-resolution
energy dispersive X-ray spectroscopy mapping reveals that phosphorus
fills the SWCNTs. High-resolution transmission electron microscopy
(HRTEM) shows long chains inside the nanotubes with varying arrangement
and packing density. A detailed match is obtained between density
functional theory (DFT) simulations, HRTEM, and low-frequency Raman
spectroscopy. Notably, a signature spectroscopic signal for phosphorus
chain cross-linking is identified. When coupled with reinterpretation
of literature data and wide-ranging DFT calculations, these results
reveal a comprehensive picture of the diameter dependence of confined
1D-phosphorus allotropes.
We present a comprehensive theoretical and experimental Raman spectroscopic comparative study of bulk Phosphorus allotropes (white, black, Hittorf’s, Fibrous) and their monolayer equivalents, demonstrating that the application of the Placzek...
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