摘要: Carbon fiber-reinforced epoxy resin composites (CFRCs) have been used in the transportation and aerospace fields because of their excellent mechanical properties. The recycling of CFRCs has attracted attention worldwide in recent years. Chemical recycling is a promising method, which can selectively destroy specific resin bonds to achieve controllable degradation. Matrix epoxy resins are degraded into monomers or oligomers, and the high-value carbon fibers can be recycled. First, we summarize progress on chemical recovery methods, mainly super- and subcritical fluids, oxidation, alcoholysis and electrochemical recycling etc. Then, we briefly introduce the synthesis and depolymerization mechanism of recyclable thermosetting resins by the insertion of reversible chemical bonds into the resin to prepare recyclable resins, which is beneficial for the recycling and reuse of components in CFRCs. Finally, possible developments in the chemical recycling of CFRCs and the preparation of high-performance recyclable epoxy resins are proposed.
Three dimensional (3D) printing is a modern technology that has the possibility to transform existing production methods. It offers a novel production method of layered manufacturing and layer-by-layer stacking, which radically simplifies the manufacturing process and enables large-scale customizable production. However, there are still numerous problems with this new technology. Except for pure graphene, sp2 carbons can be 3D printed with little difficulty because of their hydrophilicity. The hydrophobic nature of pure graphene makes it difficult to print and process in water-based media, but advances in capillary inks allow for the 3D printing of pure graphene. This review focuses on the most recent developments in the 3D printing of sp2 carbons. A concise overview of 3D printing technologies is presented, followed by a summary of 3D printed sp2 carbons and their diverse applications. Finally, prospects and opportunities for this new field are discussed.
Capacitive deionization (CDI) has rapidly become a promising approach for water desalination. The technique removes salt from water by applying an electric potential between two porous electrodes to cause adsorption of charged species on the electrode surfaces. The nature of CDI favors the use of nanostructured porous carbon materials with high specific surface areas and appropriate surface functional groups. Electrospun carbon nanofibers (CNFs) are ideal as they have a high specific surface area and surface characteristics for doping/grafting with electroactive agents. Compared with powdered materials, CNF electrodes are free-standing and don’t require binders that increase resistivity. CNFs with an appropriate distribution of mesopores and micropores have better desalination performance. Compositing CNFs with faradaic materials improve ion storage by adding pseudocapacitance to the electric double layer capacitance. The use of electrospun CNFs as electrodes for CDI is summarized with emphasis on the major precursor materials used in their preparation and structure modification, and their relations to the performance in salt electrosorption.
摘要: With the rapid development of electric vehicles and large-scale power grids, lithium-ion batteries inevitably face the problem that their limited energy density and high cost cannot meet the growing demand. Room temperature sodium-sulfur (RT Na-S) batteries, which have the potential to replace lithium-ion batteries, have become a focus of attention. However, the challenging problem of their poor cycling performance cause by the “shuttle effect” of the reaction intermediates (sodium polysulfides) needs to be addressed. We report a method to incorporate TiO2 nano particles into the multichannels of electrospun carbon fibers (TiO2@MCCFs) to stabilize the sulfur compounds and produce high-performance RT Na-S batteries. The TiO2@MCCFs were prepared by electrospinning followed by heat treatment, and were infiltrated by molten sulfur to fabricate S/TiO2@MCCF cathode materials. The addition of the TiO2 nanoparticles increases the affinity of cathode materials for polysulfides and promotes the conversion of polysulfides to lower order products. This was verified by DFT calculations. A S/TiO2@MCCF cathode with a S content of 54% has improved electrochemical rate and cycling performance, with a specific capacity of 445.1 mAh g−1 after 100 cycles at 0.1 A g−1 and a nearly 100% Coulombic efficiency. Even at 2 A g−1, the cathode still has a capacity of 300.5 mAh g−1 after 500 cycles. This work provides a new way to construct high performance RT Na-S battery cathodes.
摘要: Hard carbons have recently attracted wide interest as anode materials for potassium ion batteries (PIBs) because of their high reversible capacity. But, their high preparation cost and poor cycling stability prevent their practical use. Coconut shell-derived hard carbons (CSHCs) were prepared from waste biomass coconut shell using a one-step carbonization method, and were used as anode materials for potassium ion batteries. The effects of the carbonization temperature on the microstructures and electrochemical properties of the CSHCs were investigated by X-ray diffraction, nitrogen adsorption, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, and cyclic voltammetry, etc. Results indicate that the CSHC carbonized at 1 000 °C (CSHC-10) has a suitable graphite microcrystal size, pore structure and surface defect content, and has the best electrochemical performance. Specifically, it has a high reversible specific capacity of 254 mAh·g−1 at 30 mA·g−1 with an initial Coulombic efficiency of 75.0%, and the capacity retention rates are 87.5% after 100 cycles and 75.9% after 400 cycles at 100 mA·g−1, demonstrating its excellent potassium storage performance.
摘要: Using CO2 as a renewable carbon source for the production of high-value-added fuels and chemicals has recently received global attention. The photoelectrocatalytic (PEC) CO2 reduction reaction (CO2RR) is one of the most realistic and attractive ways of achieving this, and can be realized effectively under sunlight illumination at a low overpotential. Oxygen-incorporated carbon nitride porous nanosheets (CNs) were synthesized from urea or melamine by annealing in nitrogen or N2/O2 gas mixtures. They were used as the photoanode with Bi2CuO4 as the photocathode to realize PEC CO2 reduction to the formate. The electrical conductivity and the photoelectric response of the CNs were modified by changing the oxygen source. Oxygen in CNs obtained from an oxygen-containing precursor improved the conductivity because of its greater electronegativity, whereas oxygen in CNs obtained from the calcination atmosphere had a lower photoelectric response due to a down shift of the energy band structure. The CN prepared by annealing urea, which served as the source of oxygen and nitrogen, at 550 °C for 2 h in nitrogen is the best. It has a photocurrent density of 587 μA cm−2 and an activity of PEC CO2 reduction to the formate of 273.56 µmol cm−2 h−1, which is nearly 19 times higher than a conventional sample. The CN sample shows excellent stability with the photocurrent remaining constant for 24 h. This work provides a new way to achieve efficient catalysts for PEC CO2 reduction to the formate, which may be expanded to different PEC reactions using different cathode catalysts.
摘要: Hard carbon is considered the most promising anode material for sodium-ion batteries, but its volume change during sodiation/desodiation limits its cycle life. Hard carbon microspheres (HCSs) with no binder were composited with a MXene film to form an electrode and its sodium storage properties were studied. The microspheres were prepared using Shanxi aged vinegar as a liquid carbon source. Two-dimensional Ti3C2Tx MXene (T is a functional group) was used as a multifunctional conductive binder to fabricate the flexible electrodes. Remarkably, because of the three-dimensional conductive network, the HCS/Ti3C2Tx film electrode has a high capacity of 346 mAh g−1, excellent rate performance and outstanding cycling stability over 1 000 cycles. This remarkable electrochemical performance indicates that the flexible film is a very promising anode for next-generation sodium-ion batteries.
摘要: Several graphite samples with different microstructures were prepared from anthracite using industrial silicon powders as catalyst. The mechanism of the catalytic reaction and the electrochemical properties of the prepared coal-based graphite in lithium anodes were investigated. The correlation between the microstructure and the properties of the graphite is discussed. Results show that the sample with 5% silicon (G-2800-5%) has the best lithium storage. It has the well-developed graphitic structure with a degree of graphitization of 91.5% as determined from the interlayer spacing. When used as an anode material, a high reversible capacity of 369.0 mAh g−1 was achieved at 0.1 A g−1 and its reversible capacity was 209.0 mAh g−1 at a current density of 1 A g−1. It also exhibits good cycling stability with a capacity retention of 92.2% after 200 cycles at 0.2 A g−1. The highly developed graphite structure, which is favorable for the formation of a stable SEI and therefore reduces lithium ion loss, is responsible for the superior electrochemical performance.
摘要: Graphene oxide (GO) obtained from coal-based graphite by the Hummers method was hydrothermally treated to obtain reduced GO (rGO). TiO2 was mixed with aqueous suspensions of GO and rGO and dried at 70 oC to obtain GO-TiO2 and rGO-TiO2 with 95% (mass fraction) TiO2. TiO2 was also combined with a GO suspension by hydrothermal treatment to obtain rGO-hTiO2 with 95% TiO2. The three hybrids were used as catalysts for the photocatalytic degradation of rhodamine B (Rh B) and methyl orange (MO). Of the three materials, rGO-hTiO2 had the highest catalytic activity for the degradation of Rh B and MO under visible light irradiation. The reasons for having the best catalytic activity are that the incorporation of rGO into TiO2 helps increase its adsorption capacities for Rh B and MO as evidenced by adsorption in dark, and a narrowing of the TiO2 band gap as revealed by diffuse UV reflectance spectroscopy. This reduces the rate of recombination of electron–hole pairs by there being intimate contact between the TiO2 particles and rGO, forming Ti-O-C bonds as confirmed by XPS, with the TiO2 particles being uniformly decorated on the rGO sheets.
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