Hailong Tang,Yongqing Ma,Ganhong Zheng,Chuhong Zhu,Meiling Wang,Yilin Lu,Xiao Sun
Photocatalytic CH 4 conversion to CH 3 OH under mild conditions is undoubtedly an efficient strategy to realize CH 4 upgrading. In this work, in-situ formed highly reactive Fe IV =O complex with a bound Cl axial ligand was detected at ambient temperature and its contribution to CH 4 photoxidation to CH 3 OH was deeply investigated. Under optimized experimental condition, a high CH 3 OH yield of 3026.1 mmol mol Fe −1 (6.76 mmol g cat −1 h −1 ) with selectivity of 73.6 % was obtained during 8 h. Isotope labeling mass spectroscopy experiments manifested that O 2 was the only source of oxygen in products. The formation of Cl-(H 2 O) 4 Fe IV O complex was confirmed using low-temperature electron spin resonance spectroscopy and cryogenic Raman spectroscopy (ν(Fe O) = 828 cm −1 ). Through density functional theory (DFT) calculation, we showed that the Cl axial ligand acts as an “electron reservoir” during CH 4 conversion, i.e., electron acceptor during the process of CH 4 oxidation to CH 3 OH, while electron donor in CH 3 OH desorption. This not only lowered C-H cleavage energy, but also facilitated CH 3 OH desoption and inhibited overoxidation. As far as we know, Cl-(H 2 O) 4 Fe IV O is the first detected Fe IV O complex generated directly from O 2 and Fe 3+ at ambient temperature.
Titanium nitride (TiN) has been attracting increasing interest as an anode material for electrochemical energy storage and conversion systems due to its superior thermal stability, electrical conductivity and chemical durability. The most commonly used strategy to synthesize TiN nanostructures is nitriding TiO 2 nanostructures using ammonia gas as the nitrogen source, and thus is not environmental friendly. Herein, we report an ammonia-free strategy to synthesize TiN nanomaterials using TiO 2 precursors via a magnesium-assisted nitriding reaction using nitrogen gas (N 2 ) as the nitrogen source. Systematical studies were conducted to reveal the mechanism of magnesium-assisted nitriding process in constructing TiN nanostructures under N 2 atmosphere. The as-synthesized TiN NRs were directly used as the anodes for lithium ion batteries and delivered an excellent reversible capacity of 710 mAh g −1 at the current density of 100 mA g −1 after 200 cycles. In addition, the TiN NRs also exhibited excellent cycling stability and rate capability. Our work provides a low cost, environmental friendly and reliable strategy to synthesize TiN materials from TiO 2 by using N 2 as the nitrogen source, which may facilitate the practical applications of TiN materials in electrochemical/photo-electrochemical energy storage and conversion systems.
Owing to the high interface thermal resistance and aggregation in polymer-based materials, the thermal conductivity of multi-walled carbon nanotubes (MWCNTs) has been severely decreased in practical applications. In this work, an amino-functionalized black phosphorene (BP–NH 2 ) fabricated by ball milling has been employed to react with carboxylated multi-wall carbon nanotubes (MWCNTs–COOH) via covalent bonds to prepare a nanofiller (BP–MWCNTs) with high thermal conductivity and excellent flame retardancy. When incorporating 20.0 wt% BP–MWCNTs into cellulose nanofiber (CNF), the CNF/BP–MWCNTs 20.0 shows an in-plane thermal conductivity of 22.38 ± 0.39 W m −1 K −1 and a cross-plane thermal conductivity of 0.36 ± 0.03 W m −1 K −1 , resulting in an anisotropy index of 62.17. The effective medium theory (EMT) calculation demonstrates the interface thermal resistance is reduced to 1/39 that of pure MWCNTs, which is ascribed to the covalent bond between BP–NH 2 and MWCNTs–COOH. Simultaneously, the CNF/BP–MWCNTs 20.0 can pass the testing of UL-94 V-0 grade and the limiting oxygen index (LOI) value can be increased from 18.1% to 29.9%. Its peak of heat release rate (PHRR), total heat release (THR), smoke production rate (SPR), total smoke production (TSP), CO generated per second (COP) and CO 2 generated per second (CO 2 P) are decreased by 37.47%, 43.51%, 50.00%, 35.29%, 50.00% and 19.70%, respectively, which is due to the formation of an intumescent flame-retardant system rich in carbon source (MWCNTs), acid source (BP) and gas source (amino groups). This covalent linkage strategy offers a new thought for the preparation of flexible materials to enhance the thermal conductivity and fire resistance .
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