## 优先发表

Three dimensional (3D) printing is a modern technology in the 4th engineering revolution that has the possibility to transform existing production methods. It offers a novel production method of layered manufacturing and layer-by-layer stacking based on the forming principle, which radically simplifies the manufacturing process and enables large-scale customizable production. However, there are still numerous issues with this new technology. Except 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. Thanks to the advancement of capillary inks, which allow for the 3D printing of pure graphene. The current review focuses on the most recent developments in 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, perspectives and opportunities for this new field are discussed. Three dimensional (3D) printing is a modern technology in the 4th engineering revolution that has the possibility to transform existing production methods. It offers a novel production method of layered manufacturing and layer-by-layer stacking based on the forming principle, which radically simplifies the manufacturing process and enables large-scale customizable production. However, there are still numerous issues with this new technology. Except 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. Thanks to the advancement of capillary inks, which allow for the 3D printing of pure graphene. The current review focuses on the most recent developments in 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, perspectives and opportunities for this new field are discussed.

Carbon fiber reinforced epoxy resin composites (CFRCs) have been used in automotive and aerospace fields due to their excellent mechanical properties. The recycling of CFRCs attracts attention worldwide in recent years. Chemical recycling is a more promising method, which can selectively destroy the specific bond of resin to achieve controllable degradation. Matrix epoxy resins are degraded into monomers or oligomers, and high-value carbon fibers can be recycled. Therefore, we focus on summarizing the progress of chemical recovery method, mainly including super- and subercritical fluids, oxidation, solvolysis, alcoholysis, electrochemical recycling and so on. In addition, the insertion of reversible chemical bonds into the resin to prepare recyclable resins is beneficial for recyling and reuse of components in CFRCs. Therefore, we also briefly introduce the synthesis and depolymerization mechanism of recyclable thermosetting resins. Finally, the possible development directions of chemical recovery of CFRCs and preparation of high-performance recyclable epoxy resins are proposed. Carbon fiber reinforced epoxy resin composites (CFRCs) have been used in automotive and aerospace fields due to their excellent mechanical properties. The recycling of CFRCs attracts attention worldwide in recent years. Chemical recycling is a more promising method, which can selectively destroy the specific bond of resin to achieve controllable degradation. Matrix epoxy resins are degraded into monomers or oligomers, and high-value carbon fibers can be recycled. Therefore, we focus on summarizing the progress of chemical recovery method, mainly including super- and subercritical fluids, oxidation, solvolysis, alcoholysis, electrochemical recycling and so on. In addition, the insertion of reversible chemical bonds into the resin to prepare recyclable resins is beneficial for recyling and reuse of components in CFRCs. Therefore, we also briefly introduce the synthesis and depolymerization mechanism of recyclable thermosetting resins. Finally, the possible development directions of chemical recovery of CFRCs and preparation of high-performance recyclable epoxy resins are proposed.

Capacitive deionization (CDI) has rapidly become a promising approach for water desalination. The technique removes salt from water through 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 area and appropriate surface functional groups. Electrospun carbon nanofibers (CNFs) are quite ideal as they have 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. Hierarchically structured CNFs with an appropriate distribution of mesopores and micropores have better desalination performance. Compositing CNFs with faradaic materials enhances ion storage by additional pseudocapacitance besides the electric double layer capacitance. Herein, the use of electrospun CNFs as electrodes for CDI is summarized with emphasis on the major precursor materials used and structure modification, and their relations to the performance in salt electrosorption. Capacitive deionization (CDI) has rapidly become a promising approach for water desalination. The technique removes salt from water through 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 area and appropriate surface functional groups. Electrospun carbon nanofibers (CNFs) are quite ideal as they have 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. Hierarchically structured CNFs with an appropriate distribution of mesopores and micropores have better desalination performance. Compositing CNFs with faradaic materials enhances ion storage by additional pseudocapacitance besides the electric double layer capacitance. Herein, the use of electrospun CNFs as electrodes for CDI is summarized with emphasis on the major precursor materials used and structure modification, and their relations to the performance in salt electrosorption.

Ordered and disordered carbons have been commonly used as coating materials for silicon (Si) anodes, however the effect of carbons with different crystallinities and pore structures on their electrochemical performance remains controversial. We used pitch and phenolic resin (PR) as the precursors of ordered and disordered carbon, respectively, to prepare carbon-coated silicon (Si@C) with strictly controlled carbon contents and surface functional groups. Their electrochemical behavior was investigated. An ordered crystalline structure is favorable for electron transport, and mesopores and macropores are conducive to the diffusion of lithium ions. Such a coating with a small pore volume is an excellent buffer for the expansion of Si, and the electrode maintains structural integrity for 50 cycles. A disordered porous structure is less robust and produces a large polarization, which produces continuous volume expansion with cycling and leads to inferior electrochemical performance. As a result, the capacity and capacity retention after 100 cycles at 0.5 A g−1 of Si@C-Pitch are respectively 8 times and 1.9 times those of Si@C-PR. This study provides theoretical guidance for the selection of carbon materials used in Si@C anodes. Ordered and disordered carbons have been commonly used as coating materials for silicon (Si) anodes, however the effect of carbons with different crystallinities and pore structures on their electrochemical performance remains controversial. We used pitch and phenolic resin (PR) as the precursors of ordered and disordered carbon, respectively, to prepare carbon-coated silicon (Si@C) with strictly controlled carbon contents and surface functional groups. Their electrochemical behavior was investigated. An ordered crystalline structure is favorable for electron transport, and mesopores and macropores are conducive to the diffusion of lithium ions. Such a coating with a small pore volume is an excellent buffer for the expansion of Si, and the electrode maintains structural integrity for 50 cycles. A disordered porous structure is less robust and produces a large polarization, which produces continuous volume expansion with cycling and leads to inferior electrochemical performance. As a result, the capacity and capacity retention after 100 cycles at 0.5 A g−1 of Si@C-Pitch are respectively 8 times and 1.9 times those of Si@C-PR. This study provides theoretical guidance for the selection of carbon materials used in Si@C anodes.

Graphene oxide (GO) obtained by the Hummers method from coal-based graphite was composited with TiO2 by hydrothermal and wet mixing methods to obtain (H-rGO)/TiO2 and M-TiO2/rGO composites, respectively, which were used as catalysts for photocatalytic degradation of rhodamine B (Rh B) and methyl orange (MO). Compared with the M-TiO2/GO and M-TiO2/rGO composites, the TiO2 nanoparticles in H-TiO2/rGO were more uniformly decorated on both sides of rGO sheets, forming a stacked-sheet structure while apparent aggregation of TiO2 nanoparticles was found in both M-TiO2/GO and M-TiO2/rGO. H-rGO@TiO2 had the highest catalytic activity towards degradation of Rh B and MO under visible light irradiation among the three, where the incorporation of rGO into TiO2 helps to narrow the band gap of TiO2, inhibits the recombination rate of electron–hole pairs and provides conductive networks for electron transfer. Graphene oxide (GO) obtained by the Hummers method from coal-based graphite was composited with TiO2 by hydrothermal and wet mixing methods to obtain (H-rGO)/TiO2 and M-TiO2/rGO composites, respectively, which were used as catalysts for photocatalytic degradation of rhodamine B (Rh B) and methyl orange (MO). Compared with the M-TiO2/GO and M-TiO2/rGO composites, the TiO2 nanoparticles in H-TiO2/rGO were more uniformly decorated on both sides of rGO sheets, forming a stacked-sheet structure while apparent aggregation of TiO2 nanoparticles was found in both M-TiO2/GO and M-TiO2/rGO. H-rGO@TiO2 had the highest catalytic activity towards degradation of Rh B and MO under visible light irradiation among the three, where the incorporation of rGO into TiO2 helps to narrow the band gap of TiO2, inhibits the recombination rate of electron–hole pairs and provides conductive networks for electron transfer.

In the context of sustainable development, tackling the severe solid waste pollutions has become extremely urgent. Herein, the solid waste gangue was used to synthesize the ceramic-based microwave absorbing composites decorated with Co particles by a novel synthesis method, where the magnetic Co particles were uniformly loaded in the ceramic matrix by pelletizing gangue accompanied by spraying a solution containing Co2+, followed by in-situ carbothermal reduction using the fixed carbon in gangue as the reduction agent. The Co contents in ceramic composites are precisely controlled by adjusting the Co2+ concentration in the solutions. The fixed carbon in gangue is partially consumed and there are residue carbons in the composites, which have more defects as compared with that in gangue and play an important role as an dielectric constitute. Compared with gangue, the optimized composite exhibits excellent microwave absorbing properties with the minimum reflection loss value of −48.2 dB and the effective absorbing band of 4.3 GHz under a coating thickness of 1.5 mm. which is mainly attributed to the enhanced magnetic loss and multiple interface polarization in the composite. Such use of gangue in this work can effectively realize the resource utilization and production of low-cost and light-weight of microwave absorbing materials. In the context of sustainable development, tackling the severe solid waste pollutions has become extremely urgent. Herein, the solid waste gangue was used to synthesize the ceramic-based microwave absorbing composites decorated with Co particles by a novel synthesis method, where the magnetic Co particles were uniformly loaded in the ceramic matrix by pelletizing gangue accompanied by spraying a solution containing Co2+, followed by in-situ carbothermal reduction using the fixed carbon in gangue as the reduction agent. The Co contents in ceramic composites are precisely controlled by adjusting the Co2+ concentration in the solutions. The fixed carbon in gangue is partially consumed and there are residue carbons in the composites, which have more defects as compared with that in gangue and play an important role as an dielectric constitute. Compared with gangue, the optimized composite exhibits excellent microwave absorbing properties with the minimum reflection loss value of −48.2 dB and the effective absorbing band of 4.3 GHz under a coating thickness of 1.5 mm. which is mainly attributed to the enhanced magnetic loss and multiple interface polarization in the composite. Such use of gangue in this work can effectively realize the resource utilization and production of low-cost and light-weight of microwave absorbing materials.

Using CO2 as a renewable carbon source for the production of high-value-added fuels and chemicals has drawn global attention lately. Photoelectrocatalytic (PEC) CO2 reduction (CO2RR) is one of the most realistic and attractive way, which can be realized effectively under sunlight illumination at low overpotential. Here, oxygen-incorporated carbon nitride (CNs) porous nanosheets were synthesized, which were used as photoanodes with Bi2CuO4 as the photocathode to realize the PEC CO2 reduction to formate. The electrical conductivity and the photoelectric response of CNs were tailored by changing the oxygen source. The oxygen obtained from the oxygen-containing precursor could improve the conductivity due to the more negative electronegativity. The oxygen obtained from the calcination atmosphere has lower photoelectric response due to the energy band structure. Under the optimal conditions, the CN has a photocurrent density of 587 μA cm−2 and an activity of PEC CO2 reduction to formate of 273.56 µmol cm−2 h−1, which is nearly 19 times higher than that of the conventional sample. Moreover, the optimal CN sample shows excellent stability with the photocurrent kept constant for 24 h. This work provides a new avenue to achieve catalysts efficient for PEC CO2 reduction to formate, which may be expanded to different PEC reactions using different cathode catalysts.ode catalysts. Using CO2 as a renewable carbon source for the production of high-value-added fuels and chemicals has drawn global attention lately. Photoelectrocatalytic (PEC) CO2 reduction (CO2RR) is one of the most realistic and attractive way, which can be realized effectively under sunlight illumination at low overpotential. Here, oxygen-incorporated carbon nitride (CNs) porous nanosheets were synthesized, which were used as photoanodes with Bi2CuO4 as the photocathode to realize the PEC CO2 reduction to formate. The electrical conductivity and the photoelectric response of CNs were tailored by changing the oxygen source. The oxygen obtained from the oxygen-containing precursor could improve the conductivity due to the more negative electronegativity. The oxygen obtained from the calcination atmosphere has lower photoelectric response due to the energy band structure. Under the optimal conditions, the CN has a photocurrent density of 587 μA cm−2 and an activity of PEC CO2 reduction to formate of 273.56 µmol cm−2 h−1, which is nearly 19 times higher than that of the conventional sample. Moreover, the optimal CN sample shows excellent stability with the photocurrent kept constant for 24 h. This work provides a new avenue to achieve catalysts efficient for PEC CO2 reduction to formate, which may be expanded to different PEC reactions using different cathode catalysts.ode catalysts.

With the rapid development of electric vehicles and large-scale power grids, lithium-ion batteries inevitably face the dilemma in that the limited energy density and high cost fail to meet the growing demand. Room temperature sodium-sulfur (RT Na-S) batteries, which have the potential to replace lithium-ion batteries, have become the focus of attention. However, the challenging problem of poor cycling performance arising from “shuttle effect” of the reaction intermediates (sodium polysulfides) needs to be addressed. We report a method to incorporate TiO2 nano particles into multichannels of electrospun carbon fibers (TiO2@MCCFs) to stabilize sulfur compounds to produce high-performance RT Na-S batteries. The TiO2@MCCFs were prepared by electrospinning followed by heat treatment, which were infiltrated by molten sulfur to fabricate S/TiO2@MCCF cathode materials. The addition of TiO2 nanoparticles enhances the affinity to polysulfides and promotes the conversion of polysulfides to lower order products, which was verified by DFT calculations. The S/TiO2@MCCF cathode with a S content of 54% has improved electrochemical 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 exhibits a capacity of 300.5 mAh g−1 after 500 cycles, demonstrating excellent rate and cycling performance. This work provides a new way to construct high performance RT Na-S battery cathodes. With the rapid development of electric vehicles and large-scale power grids, lithium-ion batteries inevitably face the dilemma in that the limited energy density and high cost fail to meet the growing demand. Room temperature sodium-sulfur (RT Na-S) batteries, which have the potential to replace lithium-ion batteries, have become the focus of attention. However, the challenging problem of poor cycling performance arising from “shuttle effect” of the reaction intermediates (sodium polysulfides) needs to be addressed. We report a method to incorporate TiO2 nano particles into multichannels of electrospun carbon fibers (TiO2@MCCFs) to stabilize sulfur compounds to produce high-performance RT Na-S batteries. The TiO2@MCCFs were prepared by electrospinning followed by heat treatment, which were infiltrated by molten sulfur to fabricate S/TiO2@MCCF cathode materials. The addition of TiO2 nanoparticles enhances the affinity to polysulfides and promotes the conversion of polysulfides to lower order products, which was verified by DFT calculations. The S/TiO2@MCCF cathode with a S content of 54% has improved electrochemical 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 exhibits a capacity of 300.5 mAh g−1 after 500 cycles, demonstrating excellent rate and cycling performance. This work provides a new way to construct high performance RT Na-S battery cathodes.

Biomorphic hard carbons have attracted widely interest as anode materials for potassium ion batteries (PIBs) recently owing to their high reversible capacity. But, the high preparation cost and poor cycle stability significantly hinder their practical applications. In this study, coconut shell-derived hard carbon (CSHCs) were prepared from waste biomass coconut shell using a one-step carbonization method, which 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) possesses a suitable graphite microcrystalline size, pore structure and surface defect content, which exhibits the best electrochemical performance. Specifically, it presents 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. Biomorphic hard carbons have attracted widely interest as anode materials for potassium ion batteries (PIBs) recently owing to their high reversible capacity. But, the high preparation cost and poor cycle stability significantly hinder their practical applications. In this study, coconut shell-derived hard carbon (CSHCs) were prepared from waste biomass coconut shell using a one-step carbonization method, which 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) possesses a suitable graphite microcrystalline size, pore structure and surface defect content, which exhibits the best electrochemical performance. Specifically, it presents 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.

In this work, graphites with various microstructures were prepared by cost-effective anthracite and industrial silicon powder as precursor and catalyst, respectively. The mechanism of catalytic reaction and the electrochemical properties of the as-prepared coal-based graphite as lithium anode were investigated. The correlation between structure and properties of graphite was discussed. The results demonstrate that the as-obtained sample with 5% silicon catalyst (G-2800-5%) exhibits the best overall lithium storage performance. In detail, G-2800-5% displays the best graphite structure with graphitization degree of 91.5%. As anode materials, a high reversible capacity of 369.0 mAh g−1 can be achieved at 0.1 A g−1. Meanwhile, the reversible capacity of 209.0 mAh g−1 can be obtained at the current density of 1 A g−1. It also delivers good cyclic stability with the retention rate of 92.2% after 200 cycles at 0.2 A g−1. The highly developed graphite structure, which is favorable to the formation of stable SEI and reduces lithium ion loss should be responsible for the superior electrochemical performance. In this work, graphites with various microstructures were prepared by cost-effective anthracite and industrial silicon powder as precursor and catalyst, respectively. The mechanism of catalytic reaction and the electrochemical properties of the as-prepared coal-based graphite as lithium anode were investigated. The correlation between structure and properties of graphite was discussed. The results demonstrate that the as-obtained sample with 5% silicon catalyst (G-2800-5%) exhibits the best overall lithium storage performance. In detail, G-2800-5% displays the best graphite structure with graphitization degree of 91.5%. As anode materials, a high reversible capacity of 369.0 mAh g−1 can be achieved at 0.1 A g−1. Meanwhile, the reversible capacity of 209.0 mAh g−1 can be obtained at the current density of 1 A g−1. It also delivers good cyclic stability with the retention rate of 92.2% after 200 cycles at 0.2 A g−1. The highly developed graphite structure, which is favorable to the formation of stable SEI and reduces lithium ion loss should be responsible for the superior electrochemical performance.

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. 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.

Tailor-made fabrication of sulfur host is very effective for solving the main challenges of lithium-sulfur (Li-S) batteries, such as the shuttle effect and sluggish redox kinetics, due to that sulfur host as a reactor for redox reactions determines the electrochemical properties of the sulfur cathode. Under this guidance, sulfur is in-situ confined in a hollow thin-walled C/Mo2C reactor with size smaller than 7 nm, in which these nanosized primary particles are connected each other to form secondary microsized particles. In such composites, the nanoscale sulfur core and continuous conductive network can facilitate lithium-ion and electron transport. Moreover, the microporous C/Mo2C shell can mitigate the outward diffusion of polysulfides via the physical/chemical obstruction and enhance redox kinetics by effectively catalytic conversion of polysulfides. Stem from these merits, the S@C/Mo2C cathode materials can achieve a high reversible capacity of 1210 mA h g−1 at 0.5 C with a low capacity fading rate of 0.127% per cycle over 300 cycles and high rate performance (780 mA h g−1 at 3.0 C). The present work may shed light on designing advanced sulfur host for Li-S batteries with high rate performance and high cycle stability. Tailor-made fabrication of sulfur host is very effective for solving the main challenges of lithium-sulfur (Li-S) batteries, such as the shuttle effect and sluggish redox kinetics, due to that sulfur host as a reactor for redox reactions determines the electrochemical properties of the sulfur cathode. Under this guidance, sulfur is in-situ confined in a hollow thin-walled C/Mo2C reactor with size smaller than 7 nm, in which these nanosized primary particles are connected each other to form secondary microsized particles. In such composites, the nanoscale sulfur core and continuous conductive network can facilitate lithium-ion and electron transport. Moreover, the microporous C/Mo2C shell can mitigate the outward diffusion of polysulfides via the physical/chemical obstruction and enhance redox kinetics by effectively catalytic conversion of polysulfides. Stem from these merits, the S@C/Mo2C cathode materials can achieve a high reversible capacity of 1210 mA h g−1 at 0.5 C with a low capacity fading rate of 0.127% per cycle over 300 cycles and high rate performance (780 mA h g−1 at 3.0 C). The present work may shed light on designing advanced sulfur host for Li-S batteries with high rate performance and high cycle stability.

An anodized carbon fiber tow is sized continuously. The effects of aqueous polyurethane as the sizing agent for enhancing the interfacial properties of carbon fiber reinforced polyurethane composite is investigated based on interlaminar shear strength (ILSS), elemental and functional group analysis, thermal gravimetric analysis and differential scanning calorimetry. The results show the polyurethane as the sizing agent of carbon fiber can significantly improve the interfacial properties of the composites. The ILSS of the sized carbon fiber reinforced composite is increased by 17.5%, from 39.5 MPa to 46.4 MPa compared with that the oxidized carbon fiber reinforced. Treating the sized carbon fiber reinforced composite at 170 °C can further increase the ILSS by 9.5%, to 50.8 MPa. It is considered the sizing agent can form chemical binding with the oxygen-contained functional groups on the oxidized carbon fiber surface and form hydrogen bonds with the matrix resin. After heat treatment at 170 °C, the blocking groups in the sizing agent are unblocked to reveal the isocyanate roots that react with the carbamate of the matrix to form allophanate. It can be concluded that the polyurethane sizing agent is suitable for improving the interface performance of carbon fiber reinforced polyurethane resin composites. Unsealing the sizing agent at high temperature treatment after curing can further improve the interface performance of the composite. An anodized carbon fiber tow is sized continuously. The effects of aqueous polyurethane as the sizing agent for enhancing the interfacial properties of carbon fiber reinforced polyurethane composite is investigated based on interlaminar shear strength (ILSS), elemental and functional group analysis, thermal gravimetric analysis and differential scanning calorimetry. The results show the polyurethane as the sizing agent of carbon fiber can significantly improve the interfacial properties of the composites. The ILSS of the sized carbon fiber reinforced composite is increased by 17.5%, from 39.5 MPa to 46.4 MPa compared with that the oxidized carbon fiber reinforced. Treating the sized carbon fiber reinforced composite at 170 °C can further increase the ILSS by 9.5%, to 50.8 MPa. It is considered the sizing agent can form chemical binding with the oxygen-contained functional groups on the oxidized carbon fiber surface and form hydrogen bonds with the matrix resin. After heat treatment at 170 °C, the blocking groups in the sizing agent are unblocked to reveal the isocyanate roots that react with the carbamate of the matrix to form allophanate. It can be concluded that the polyurethane sizing agent is suitable for improving the interface performance of carbon fiber reinforced polyurethane resin composites. Unsealing the sizing agent at high temperature treatment after curing can further improve the interface performance of the composite.

Mesophase pitch-based carbon fibers (MPCFs) have the characteristics of high modulus, low resistivity and high thermal conductivity, so it has broad application prospects in many fields. High-performance carbon fibers were prepared from naphthalene-based mesophase pitches synthesized by HF/BF3 catalytic one-step method (AR-MP) and AlCl3 catalytic two-step method (N-MP), respectively. These two mesophase pitches, and spun pitch fibers, pre-oxidized fibers carbonized fibers and graphitized fibers produced from them were characterized by TG-MS, FT-IR, 13 C-NMR, MALDI-TOF-MS, XRD, SEM and elemental analysis. The molecular structures and properties of mesophase pitches prepared by different catalytic polymerization processes were compared, and the effects of molecular structure differences of mesophase pitches on the structure and properties of carbon fibers were further explored. In comparison to N-MP, AR-MP possesses a rod-like semi-rigid molecular configuration containing more naphthenic structures and methyl side chains. The pre-oxidized fibers derived from AR-MP show better carbon layer orientation, thus their graphitized fibers have higher thermal conductivity of 716 W/m·K. N-MP with higher aromaticity possesses a disc-like rigid molecular configuration. Therefore, the graphitized fibers prepared from N-MP have higher tensile strength of 3.47 GPa due to their fewer resulted defects during the preparation. The molecular structures of AR-MP and N-MP have an obvious influence on the structure and properties of their graphited fibers. Mesophase pitch-based carbon fibers (MPCFs) have the characteristics of high modulus, low resistivity and high thermal conductivity, so it has broad application prospects in many fields. High-performance carbon fibers were prepared from naphthalene-based mesophase pitches synthesized by HF/BF3 catalytic one-step method (AR-MP) and AlCl3 catalytic two-step method (N-MP), respectively. These two mesophase pitches, and spun pitch fibers, pre-oxidized fibers carbonized fibers and graphitized fibers produced from them were characterized by TG-MS, FT-IR, 13 C-NMR, MALDI-TOF-MS, XRD, SEM and elemental analysis. The molecular structures and properties of mesophase pitches prepared by different catalytic polymerization processes were compared, and the effects of molecular structure differences of mesophase pitches on the structure and properties of carbon fibers were further explored. In comparison to N-MP, AR-MP possesses a rod-like semi-rigid molecular configuration containing more naphthenic structures and methyl side chains. The pre-oxidized fibers derived from AR-MP show better carbon layer orientation, thus their graphitized fibers have higher thermal conductivity of 716 W/m·K. N-MP with higher aromaticity possesses a disc-like rigid molecular configuration. Therefore, the graphitized fibers prepared from N-MP have higher tensile strength of 3.47 GPa due to their fewer resulted defects during the preparation. The molecular structures of AR-MP and N-MP have an obvious influence on the structure and properties of their graphited fibers.

The phenolic resin was coated on the surface of nano-Si by microencapsulation technology, and then carbonized under the Ar protection to prepare nano-Si@C nanocomposite. Firstly, four mass ratios of phenolic resin to nano-Si (1∶2, 1∶4, 1∶6, 1∶8) were employed to prepare nano-Si@C nanocomposites. The obtained average thickness of amorphous carbon coating was 7, 4.5, 3.7, 2.8 nm, respectively. By comparing the cycling and rate capability, the best electrochemical performance was obtained when the mass ratio of phenolic resin to nano Si was 1∶4, that is, the amorphous carbon coating was 4.5 nm.. The electrochemical properties of optimized nano-Si@C nanocomposite was then evaluated comprehensively, which exhibited excellent electrochemical performance as anode material for Li-ion batteries. Under a current density of 100 mAg−1, the nano-Si@C nanocomposite delivered a first discharge specific capacity of 2382 mAhg−1, first charge specific capacity of 1667 mAhg−1, and a first coulombic efficiency of 70%. Moreover, the discharge specific capacity of 835.6 mAhg−1 could be retained after 200 cycles with a high coulombic efficiency of 99.2%. In addition, nano-Si@C nanocomposite also demonstrated superior rate performance. Under the current densities of 100, 200, 500, 1000 and 2000 mAg−1, the average discharge specific capacities were 1716.4, 1231.6, 911.7, 676.1, and 339.8 mAhg−1, respectively. When the current density returned to 100 mAg−1, the specific capacity restored to 1326.4 mAhg−1. The phenolic resin was coated on the surface of nano-Si by microencapsulation technology, and then carbonized under the Ar protection to prepare nano-Si@C nanocomposite. Firstly, four mass ratios of phenolic resin to nano-Si (1∶2, 1∶4, 1∶6, 1∶8) were employed to prepare nano-Si@C nanocomposites. The obtained average thickness of amorphous carbon coating was 7, 4.5, 3.7, 2.8 nm, respectively. By comparing the cycling and rate capability, the best electrochemical performance was obtained when the mass ratio of phenolic resin to nano Si was 1∶4, that is, the amorphous carbon coating was 4.5 nm.. The electrochemical properties of optimized nano-Si@C nanocomposite was then evaluated comprehensively, which exhibited excellent electrochemical performance as anode material for Li-ion batteries. Under a current density of 100 mAg−1, the nano-Si@C nanocomposite delivered a first discharge specific capacity of 2382 mAhg−1, first charge specific capacity of 1667 mAhg−1, and a first coulombic efficiency of 70%. Moreover, the discharge specific capacity of 835.6 mAhg−1 could be retained after 200 cycles with a high coulombic efficiency of 99.2%. In addition, nano-Si@C nanocomposite also demonstrated superior rate performance. Under the current densities of 100, 200, 500, 1000 and 2000 mAg−1, the average discharge specific capacities were 1716.4, 1231.6, 911.7, 676.1, and 339.8 mAhg−1, respectively. When the current density returned to 100 mAg−1, the specific capacity restored to 1326.4 mAhg−1.

The present manuscript reports a coal-based fluorescent CDs which fabricated at room temperature through a friendly method with mixture of hydrogen peroxide (H2O2) and formic acid (HCOOH) as an oxidant instead of concentrated acid (HNO3 or H2SO4). The prepared CDs show the excitation dependent behavior with high QY approximately 7.2%. The as-made CDs are water soluble, robust photo-stability, good resistance to salt solution, insensitive to pH in a range of 2.0-12.0. The coal-based CDs served as a very sensitive nano-probe for the turn-off sensing of Fe3+ ion with a minimum LOD as low as 600 nM in a dynamic range 2 to 100 μM. This efficient, rapid synthesis of coal-based CDs will not only increase high value-added utilization of coal, but also have potential application value in sensing and several another analytical applications. The present manuscript reports a coal-based fluorescent CDs which fabricated at room temperature through a friendly method with mixture of hydrogen peroxide (H2O2) and formic acid (HCOOH) as an oxidant instead of concentrated acid (HNO3 or H2SO4). The prepared CDs show the excitation dependent behavior with high QY approximately 7.2%. The as-made CDs are water soluble, robust photo-stability, good resistance to salt solution, insensitive to pH in a range of 2.0-12.0. The coal-based CDs served as a very sensitive nano-probe for the turn-off sensing of Fe3+ ion with a minimum LOD as low as 600 nM in a dynamic range 2 to 100 μM. This efficient, rapid synthesis of coal-based CDs will not only increase high value-added utilization of coal, but also have potential application value in sensing and several another analytical applications.

In this study, a novel pantograph carbon slider (PCS) was designed by incorporating a sulfonated graphene (SG). This enhanced the mechanical and wear performances of the slider. The PCS was prepared through mold pressing, hot extrusion and roasting. A mock current-carrying wear test showed that the wear rate of the PCS reinforced by 1 wt % SG was lower by 50.0% in the normal environment and 51.0% in the rainy weather environment, compared with the control group. In addition, the flexural strength of samples with SG was higher by 41.8% compared to those without SG. Moreover, the dragging effect of SG decreased that number of random cracks and increased the compactness of fracture surface of slider materials. These changes markedly inhibited the electro-erosion of the PCS, thus improving mechanical and wear resistance significantly. In this study, a novel pantograph carbon slider (PCS) was designed by incorporating a sulfonated graphene (SG). This enhanced the mechanical and wear performances of the slider. The PCS was prepared through mold pressing, hot extrusion and roasting. A mock current-carrying wear test showed that the wear rate of the PCS reinforced by 1 wt % SG was lower by 50.0% in the normal environment and 51.0% in the rainy weather environment, compared with the control group. In addition, the flexural strength of samples with SG was higher by 41.8% compared to those without SG. Moreover, the dragging effect of SG decreased that number of random cracks and increased the compactness of fracture surface of slider materials. These changes markedly inhibited the electro-erosion of the PCS, thus improving mechanical and wear resistance significantly.

The development of high-performance electromagnetic wave absorbing materials (EWAMs) posed a prospective way to solve electromagnetic wave radiation issues in both military and civil fields. The desirable EWAMs feature strong absorption intensity, broad bandwidth, lightweight, thin thicknesses as well as other exceptional properties such as oxygen resistance, wear resistance, high-temperature resistance and high strength. In these regards, carbon-based materials, including carbon nanostructures and carbonaceous composites have become the significant participants of EWAMs, standing out for their unique structures and properties compared with the other absorption materials. In this review, we summarized the recent inspiring achievements in carbon-based EWAMs involving different dimensional (0D, 1D, 2D and 3D) carbon nanostructures and various types of carbonaceous composites (binary dielectric-carbon composite, binary magnetic-carbon composite and heterogeneous composite). Firstly, the influential factors affecting the electromagnetic microwave absorption (EWA) performances involving conductivity \begin{document}$\sigma$\end{document}, permittivity \begin{document}$\varepsilon$\end{document}and permeability \begin{document}$\mu$\end{document} were discussed based on the EWA mechanisms. Secondly, the representative reports and corresponding mechanisms about improving the EWA performance of carbon-based EWAMs were highlighted and analyzed in detail such as self-modification and composite structure construction. Finally, the current modification strategies and research prospects of carbon-based EWAMs were summarized and outlined. The development of high-performance electromagnetic wave absorbing materials (EWAMs) posed a prospective way to solve electromagnetic wave radiation issues in both military and civil fields. The desirable EWAMs feature strong absorption intensity, broad bandwidth, lightweight, thin thicknesses as well as other exceptional properties such as oxygen resistance, wear resistance, high-temperature resistance and high strength. In these regards, carbon-based materials, including carbon nanostructures and carbonaceous composites have become the significant participants of EWAMs, standing out for their unique structures and properties compared with the other absorption materials. In this review, we summarized the recent inspiring achievements in carbon-based EWAMs involving different dimensional (0D, 1D, 2D and 3D) carbon nanostructures and various types of carbonaceous composites (binary dielectric-carbon composite, binary magnetic-carbon composite and heterogeneous composite). Firstly, the influential factors affecting the electromagnetic microwave absorption (EWA) performances involving conductivity $\sigma$, permittivity $\varepsilon$and permeability $\mu$ were discussed based on the EWA mechanisms. Secondly, the representative reports and corresponding mechanisms about improving the EWA performance of carbon-based EWAMs were highlighted and analyzed in detail such as self-modification and composite structure construction. Finally, the current modification strategies and research prospects of carbon-based EWAMs were summarized and outlined.

Metal-nitrogen carbon catalysts have received great attention in the field of gas-involving electrocatalysis due to their high activity, large specific surface area and efficient gas diffusion pathways. Carbon nanofibers embedded with iron-nitrogen active sites were synthesized through an electrospinning approach followed by high-temperature treatment. We found that the introduction of g-C3N4 can enhance the anchoring of iron-nitrogen sites in the nanofiber, thus avoiding the formation of inorganic nanoparticles during high-temperature annealing. Compare with Fe3C/CNFs prepared without g-C3N4, Fe/CNFs showed an outstanding 4e oxygen reduction reaction (ORR) activity in both alkaline and acidic media. Furthermore, as air electrodes in Zn-air batteries, Fe/CNFs catalyst exhibit excellent performance with an open-circuit voltage of up to 1.49 V, a power density of 146 mW cm−2 and a specific capacity of 703 mAh gZn−1.This work proposes an effective strategy to prepare metal-nitrogen-carbon catalysts for energy-related electrocatalytic applications. Metal-nitrogen carbon catalysts have received great attention in the field of gas-involving electrocatalysis due to their high activity, large specific surface area and efficient gas diffusion pathways. Carbon nanofibers embedded with iron-nitrogen active sites were synthesized through an electrospinning approach followed by high-temperature treatment. We found that the introduction of g-C3N4 can enhance the anchoring of iron-nitrogen sites in the nanofiber, thus avoiding the formation of inorganic nanoparticles during high-temperature annealing. Compare with Fe3C/CNFs prepared without g-C3N4, Fe/CNFs showed an outstanding 4e oxygen reduction reaction (ORR) activity in both alkaline and acidic media. Furthermore, as air electrodes in Zn-air batteries, Fe/CNFs catalyst exhibit excellent performance with an open-circuit voltage of up to 1.49 V, a power density of 146 mW cm−2 and a specific capacity of 703 mAh gZn−1.This work proposes an effective strategy to prepare metal-nitrogen-carbon catalysts for energy-related electrocatalytic applications.

Interfacial adhesion between carbon fiber (CF) and polyetherketoneketone (PEKK) is the key factor to affect the mechanical performances of their composites, and thus it is very critical to impregnate PEKK into CF bundles as efficiently as possible. Here we report that owing to the high dissolubility, PEKK can be introduced onto CF surfaces via a wet strategy. The excellent wettability of PEKK guarantees a full covering and tight binding on CFs, making it possible to evaluate the interfacial shear strength (IFSS) with the microdroplet method. Furthermore, the interior of CF bundles can be completely and uniformly filled with PEKK by the solution impregnation, leading to a high interlaminar shear strength (ILSS). The maximum IFSS and ILSS can reach 107.8 and 99.3 MPa, respectively. Such superior shear properties are ascribed to the amorphous PEKK confined in the limited spacing between CFs. Interfacial adhesion between carbon fiber (CF) and polyetherketoneketone (PEKK) is the key factor to affect the mechanical performances of their composites, and thus it is very critical to impregnate PEKK into CF bundles as efficiently as possible. Here we report that owing to the high dissolubility, PEKK can be introduced onto CF surfaces via a wet strategy. The excellent wettability of PEKK guarantees a full covering and tight binding on CFs, making it possible to evaluate the interfacial shear strength (IFSS) with the microdroplet method. Furthermore, the interior of CF bundles can be completely and uniformly filled with PEKK by the solution impregnation, leading to a high interlaminar shear strength (ILSS). The maximum IFSS and ILSS can reach 107.8 and 99.3 MPa, respectively. Such superior shear properties are ascribed to the amorphous PEKK confined in the limited spacing between CFs.

In the paper, Ni/NiO nanoparticles coated with a conductive carbon layer were synthesized by hydrothermal method. They were subjected to mild gradient calcination in argon, followed by partial oxidation in oxygen. Unique 3D consecutive electron conductive network as well as synergetic effect of Ni, NiO, carbon layer and graphene sheets can effectively alleviate a large volume expansion, which can restrain the electrode crushing and aggregation, and improve the conductivity. Moreover, Ni nanoparticles can reversibly decompose Li2O during delithiation procedure, which remarkably increases the reversible capacity of Ni/NiO@C/GN anodes. Thanks to these advantages, the Ni/NiO@C/GN hybrid material has better lithium-ion storage performance than Ni/NiO/C. Compared with the initial cycle (711.6 mA h g−1), the reversible capacity of 772.1 mA h g−1 can be maintained after 300 repetitions. The property assessment enables Ni/NiO@C/GN materials to be used in the next generation of large-capacity, high-rate, stable and environmentally friendly lithium-ion batteries. In the paper, Ni/NiO nanoparticles coated with a conductive carbon layer were synthesized by hydrothermal method. They were subjected to mild gradient calcination in argon, followed by partial oxidation in oxygen. Unique 3D consecutive electron conductive network as well as synergetic effect of Ni, NiO, carbon layer and graphene sheets can effectively alleviate a large volume expansion, which can restrain the electrode crushing and aggregation, and improve the conductivity. Moreover, Ni nanoparticles can reversibly decompose Li2O during delithiation procedure, which remarkably increases the reversible capacity of Ni/NiO@C/GN anodes. Thanks to these advantages, the Ni/NiO@C/GN hybrid material has better lithium-ion storage performance than Ni/NiO/C. Compared with the initial cycle (711.6 mA h g−1), the reversible capacity of 772.1 mA h g−1 can be maintained after 300 repetitions. The property assessment enables Ni/NiO@C/GN materials to be used in the next generation of large-capacity, high-rate, stable and environmentally friendly lithium-ion batteries.

Polyether ether ketone (PEEK) has favorable mechanical properties. However, its high melt viscosity limits its applications because it is hard to process. In this study, PEEK nanocomposites modified with carbon nanotubes (CNTs) and polyether imide (PEI) were prepared using a direct wet powder blending method. The melt viscosity of the nanocomposites decreased by approximately 50%. Under optimal conditions, the addition of CNTs and PEI resulted in a synergistic increase in the toughness of the nanocomposites. The elongation at break increased by 129%, and the fracture energy increased by 97%. The uniformly dispersed CNTs/PEI powder reduces the processing difficulty of PEEK nanocomposites without affecting the heat resistance. The nanocomposites prepared by this method have lower melt viscosity. This improvement of the properties of PEEK would facilitate its use in the preparation of thermoplastic composites by powder impregnation or laser sintering technology. Polyether ether ketone (PEEK) has favorable mechanical properties. However, its high melt viscosity limits its applications because it is hard to process. In this study, PEEK nanocomposites modified with carbon nanotubes (CNTs) and polyether imide (PEI) were prepared using a direct wet powder blending method. The melt viscosity of the nanocomposites decreased by approximately 50%. Under optimal conditions, the addition of CNTs and PEI resulted in a synergistic increase in the toughness of the nanocomposites. The elongation at break increased by 129%, and the fracture energy increased by 97%. The uniformly dispersed CNTs/PEI powder reduces the processing difficulty of PEEK nanocomposites without affecting the heat resistance. The nanocomposites prepared by this method have lower melt viscosity. This improvement of the properties of PEEK would facilitate its use in the preparation of thermoplastic composites by powder impregnation or laser sintering technology.

Hollow-shaped porous carbon fiber for Li-S batteries electrodes is prepared by KOH activation using polyacrylonitrile (PAN) as the precursor. The obtained porous carbon fiber has a high specific surface area of 2491 m2·g−1 and a large pore volume of 1.22 cm3·g−1. And it exhibits an initial specific capacity of 330 mAh·g−1 at current density of 1 C. To further improve electrochemical performance, the fiber precursor is modified using hydrazine hydrate to prepare nitrogen doped hollow-shaped porous carbon fiber. The modified fiber shows a specific surface area of 1690 m2·g−1, a pore volume of 0.84 cm3·g−1 and a high nitrogen content of 8.81 at%. Since nitrogen doping can increase the polarity and adsorption capacity, the initial specific capacity of the nitrogen doped porous carbon fiber can be increased to 420 mAh·g−1 at current density of 1 C. Hollow-shaped porous carbon fiber for Li-S batteries electrodes is prepared by KOH activation using polyacrylonitrile (PAN) as the precursor. The obtained porous carbon fiber has a high specific surface area of 2491 m2·g−1 and a large pore volume of 1.22 cm3·g−1. And it exhibits an initial specific capacity of 330 mAh·g−1 at current density of 1 C. To further improve electrochemical performance, the fiber precursor is modified using hydrazine hydrate to prepare nitrogen doped hollow-shaped porous carbon fiber. The modified fiber shows a specific surface area of 1690 m2·g−1, a pore volume of 0.84 cm3·g−1 and a high nitrogen content of 8.81 at%. Since nitrogen doping can increase the polarity and adsorption capacity, the initial specific capacity of the nitrogen doped porous carbon fiber can be increased to 420 mAh·g−1 at current density of 1 C.

Carbon-based oxygen reduction reaction (ORR) catalysts are considered a potential substitution for the expensive platinum-based ORR catalysts in the aspect of energy conversion. Recently, metal and nitrogen codoped carbon materials (M-N-C) formed by transition metals and nitrogen-doped carbon materials have attracted much attention from researchers due to their low cost and excellent activity. Herein, a cobalt- and nitrogen-codoped porous carbon material (Co-N@CNT-C800) is prepared via a simple one-step pyrolysis method by well-designed carambola-shaped MOFs (ZIF-8@ZIF-67). The obtained Co-N@CNT-C800 consists of many carbon nanotubes (CNTs) with substantial Co doping and N doping. A large surface area (428 m2·g−1) and a favorable three-dimensional structure are also observed. The obtained Co-N@CNT-C800 exhibits excellent performance in half-wave potential and limited current density in alkaline media with a value of 0.841 V and 5.07 mA·cm−2, respectively. In addition, Co-N@CNT-C800 also shows excellent electrochemical stability and methanol tolerance compared with commercial Pt/C materials. The proposed strategy inspires a effective way to fabricate low cost and high activity electrocatalysts used for energy conversion. Carbon-based oxygen reduction reaction (ORR) catalysts are considered a potential substitution for the expensive platinum-based ORR catalysts in the aspect of energy conversion. Recently, metal and nitrogen codoped carbon materials (M-N-C) formed by transition metals and nitrogen-doped carbon materials have attracted much attention from researchers due to their low cost and excellent activity. Herein, a cobalt- and nitrogen-codoped porous carbon material (Co-N@CNT-C800) is prepared via a simple one-step pyrolysis method by well-designed carambola-shaped MOFs (ZIF-8@ZIF-67). The obtained Co-N@CNT-C800 consists of many carbon nanotubes (CNTs) with substantial Co doping and N doping. A large surface area (428 m2·g−1) and a favorable three-dimensional structure are also observed. The obtained Co-N@CNT-C800 exhibits excellent performance in half-wave potential and limited current density in alkaline media with a value of 0.841 V and 5.07 mA·cm−2, respectively. In addition, Co-N@CNT-C800 also shows excellent electrochemical stability and methanol tolerance compared with commercial Pt/C materials. The proposed strategy inspires a effective way to fabricate low cost and high activity electrocatalysts used for energy conversion.