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Heteroatom-doped three-dimensional (3D) porous carbons possess great potential as promising electrodes for high-performance supercapacitors. Inspired by the inherent features of intumescent flame retardants (IFRs) with universal availability, rich heteroatoms and easy thermal-carbonization to form porous carbons, herein we proposed a self-assembling and template self-activation strategy to produce N/P dual-doped 3D porous carbons by nano-CaCO

The wide application of carbon nanosheets (CNS) is still restricted by low production. Meanwhile, the accumulation of waste plastic generates serious environmental pollution. Nowadays, the conversion of waste plastic into two-dimensional CNS is regarded as a promising way to address these issues due to the high carbon content of waste plastic. However, this conversion process is still impeded by low-efficient catalysts so far. Herein, the highly efficient carbonization of waste polypropylene (PP) into CNS is achieved using a combined catalyst of ferrocene and sulfur. The carbonization process in sealed space ensures an ultrahigh carbon yield (62.8%) and a thin thickness (4–4.5 nm) of as-prepared CNS, even though little catalyst is used. After activation, the activated carbon nanosheets (ACNS) show a well-defined hierarchical porous structure with a large specific surface area (3200 m2 g−1) and a big pore volume (3.71 cm3 g−1). The ACNS based electrode delivers a high specific capacitance of 349 F g−1 at 0.5 A g−1. The fabricated symmetric supercapacitor manifests a high energy density of 23 Wh kg−1 at 225 W kg−1. These findings provide a reference for the efficient conversion of waste plastic into energy storage materials.

Carbon materials derived from zeolitic imidazolate framework-8 (ZIF-8) and composites thereof have been intensively investigated in supercapacitors. The particle size of the used ZIF-8 ranges from dozens of nanometers to several microns. However, the influence of the particle size of ZIF-8 on the capacitive performances is still not clear. A series of ZIF-8 with different particle sizes (from 25 to 296 nm) has been synthesized and carbonized for supercapacitors. Based on TEM, EDX mapping, XRD, Raman, nitrogen adsorption-desorption, XPS, and the results of electrochemical tests, the optimal particle size (≈70 nm) for superior supercapacitor performances in both acidic and alkaline electrolytes has been obtained. This important result provides a significant reference to guide future ZIF-8 related research to achieve the best electrochemical performance.

Carbon-based supercapacitors have aroused ever-increasing attention in the energy storage field due to high conductivity, chemical stability, and large surface area of the investigated carbon active materials. Herein, eucalyptus-derived nitrogen/oxygen doped hierarchical porous carbons (NHPCs) are prepared by the synergistic action of the ZnCl2 activation and the NH4Cl blowing. They feature superiorities such as high specific surface area, rational porosity, and sufficient N/O doping. These excellent physicochemical characteristics endow them excellent electrochemical performances in supercapacitors: 359 F g−1 at 0.5 A g−1 in a three-electrode system and 234 F g−1 at 0.5 A g−1 in a two-electrode system, and a high energy density of 48 Wh kg−1 at a power density of 750 W kg−1 accompanied by high durability of 92% capacitance retention through 10,000 cycles test at a high current density of 10 A g−1 in an organic electrolyte. This low-cost and facile strategy provides a novel route to transform biomass into high value-added electrode materials in energy storage fields.

Porous carbon-based supercapacitor has been regarded as a promising candidate for powering wearable electronics. To improve its energy density and mechanical flexibility, great efforts have been ma...

Polystyrene (PS) derived porous carbon sheets (CSs) were synthesized through the MgO template coupled with KOH activation. The influence of KOH ratio on the morphology, surface area and pore structure of the obtained carbon sheets was studied and discussed in details. Subsequently, the prepared carbon materials were used as the electrodes for symmetric supercapacitors. Benefiting from KOH activation, PCSs showed outstanding electrochemical performance using 1 M H2SO4 as the electrolyte. The optimal mass ratio of CSs:KOH was 1:3 (PCS-3). This sample displayed specific capacitances of 135 and 97 F g−1 at the scan rate of 1 mV s−1 and the current density of 1 A g−1. An excellent rate performance of 82.9% retention even when current density increased up to 20 A g−1 was detected. Moreover, the energy density of 3.4 W h kg−1 with the corresponding high-power density of 250 W kg−1 in the aqueous electrolyte was achieved. In particular, PCS-3 showed an excellent capacitance retention of 92.41% even after 10,000 charge/discharge cycles, clearly demonstrating the robust long-term stability.

Recently great efforts have been focused on converting biowastes into high-valued carbon materials. However, it is still a great challenge to achieve high carbon yield and controllable porous distribution in both industrial and academic research. Inspired by the multi-void structure of waste coffee grounds, herein we fabricated hierarchical porous carbon via the combination of catalytic carbonization and alkali activation. The catalytic carbonization process was applied to obtain well-defined mesoporous carbon with carbon yield as high as 42.5 wt%, and subsequent alkali activation process produced hierarchical porous carbon with ultrahigh specific surface area (3549 m2g−1) and large meso-/macropores volume (1.64 cm3g−1). In three-electrode system, the electrode exhibited a high capacitance of 440 F g−1at 0.5 A g−1in 6 M KOH aqueous electrolyte, superior to that of many reported biomass-derived porous carbons. In two-electrode system, its energy density reached to 101 Wh kg−1at the power density of 900 W kg−1in 1-Ethyl-3-Methylimidazolium Tetrafluoroborate (EMIMBF4). This work provided a cost-effective strategy to recycle biowastes into hierarchical porous carbon with high yield for high-performance energy storage application.

With the ever-increasing consumption of polyethylene terephthalate (PET) related products, how to recycle the waste PET still remains as a great challenge for the sustainable development. Converting waste PET into porous carbon material has been emerged as a promising way to address this issue. Recently, the microporous carbon derived from waste PET has drawn considerable attention in adsorption field, but its electrochemical application is still impeded by low specific surface area (SSA

Summary Poly(butylene succinate)/magnesium hydroxide (PBS/Mg(OH)2) composites were prepared by melt compounding to investigate the effect of particle size on the flame retardancy of PBS. Their flammability properties were investigated by limiting oxygen index, UL-94, and cone calorimeter tests, which suggested that the medium-sized Mg(OH)2-5 µm displayed the best flame retardancy. The residual char structure were analyzed and indicated that Mg(OH)2-5 µm could form a better protective layer than other sized particles, leading to the better flame retardancy to PBS. © 2016 The Authors. Fire and Materials published by John Wiley & Sons, Ltd.

A novel coordination polymer with the chemical formula [Cu4Br(CN)(mtz)2]n (mtz = 5-methyl tetrazole) (), has been synthesized under solvothermal conditions and characterized by elemental analysis, infrared (IR) spectroscopy, thermal gravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. Interestingly, the Cu(i), CN(-) and mtz(-) in compound are all generated from an in situ translation of the original precursors: Cu(2+), acetonitrile and 1-methyl-5-mercapto-1,2,3,4-tetrazole (Hmnt). The in situ ring-to-ring conversion of Hmnt into mtz(-) was found for the first time. Structural analysis reveals that compound is a novel 3D tetrazole-based Cu(i) coordination polymer, containing both metal halide cluster Cu6Br2 and metal pseudohalide cluster Cu2(CN)2 secondary building units (SBUs), which shows an unprecedented (3,6,10)-connected topology. Notably, a pseudo-porphyrin structure with 16-membered rings constructed by four mtz(-) anions and four copper(i) ions was observed in compound . The fluorescence properties of compound were investigated in the solid state and in various solvent emulsions, the results show that compound is a highly sensitive naked-eye colorimetric sensor for NB and 2-NT (NB = nitrobenzene and 2-NT = 2-nitrotoluene).

Conversion of waste polymer on a metal-free catalyst is a promising method for the preparation of nanocarbons. Herein, we synthesized porous carbon sheets and hollow carbon shells through the carbonization of polystyrene on magnesium oxide with different morphologies at 700 °C using a one-pot method. The morphologies, microstructure, phase structure, surface element composition, thermal stability, and textural properties of the obtained nanocarbons were analyzed by SEM, TEM, XRD, TGA, and Raman. The yield of the nanocarbons increased as the weight ratio of magnesium oxide to polystyrene increased. Magnesium oxide acted as a template for the shape-controlled growth of the carbon nanostructure. The surface area of the porous carbon sheets and hollow carbon shells reached 854 and 523 m2 g−1 without any activation, respectively. The porous carbon sheets were used as adsorbents to remove methylene blue from water and showed an adsorption capacity of 358.8 mg g−1. Product composition for the pyrolysis of polystyrene in the presence of magnesium oxide was analyzed using GC and GC-MS to elucidate the reaction mechanism. The yield of styrene in the liquid products reached 50% by the catalysis of polygonal magnesium oxide. This strategy provides a cheap and sustainable catalyst for converting polymer into high-value nanocarbons and useful chemicals.

It is a great challenge to improve the flame retardancy of polymer materials by adding eco-friendly magnesium hydroxide (Mg(OH)2) but simultaneously maintain satisfied mechanical performances. In this study, expanded graphite (EG) as a synergist was introduced into poly(butylene succinate) (PBS)/Mg(OH)2 system to investigate the effect of EG on their flame retardancy, thermal stability and mechanical properties. The results showed that only addition of 5 wt% EG into PBS/20 wt%Mg(OH)2 resulted in excellent flame retardancy, including that the LOI was 29.4%, the UL-94 rating reached to V0, and the PHRR decreased by 73%. These flame retarded parameters were comparable or even better than that of PBS/40 wt%Mg(OH)2 composites. More importantly, PBS/20 Mg(OH)2/5 EG presented much better thermal stability and mechanical properties than PBS/40 wt%Mg(OH)2, indicating a balanced improvement on comprehensive performances of PBS. Based on the comparison with PBS/20 Mg(OH)2/5Graphene(Gr) system and the structure analysis for residual chars, the mechanism for improved flame retardancy was attributed to the formation of gradient-structured char layer due to the helpful thermal expansion process of EG together with the decomposition of Mg(OH)2 during combustion, resulting in better barrier action to heat, oxygen and flammable gases via “labyrinth effect”. As far as we know, it is the first report that gradient-structured char layer was discussed in flame retarded polymer systems. Hence, this work provides not only a high-efficient synergist to improve the flame retardant efficiency of Mg(OH)2, but also useful guidelines to design polymer composites with balanced comprehensive performances.

Great efforts have been devoted to designing porous carbons to improve energy density of supercapacitor, yet still impeded by high-cost and time-consuming procedures. The low capacitance and poor rate capability of various biomass-derived carbons in organic electrolyte remain a challenge for their practical application. Herein, to address these issues, biomass (leek) is used to produce three-dimensional (3D) porous carbon, which possesses big cavities, high specific surface area and well-defined hierarchical pores. In three-electrode system, it exhibits a high capacitance of 349 F g−1 at 0.5 A g−1 in 6 M KOH electrolyte and a superior cycling stability of no capacitance decay at 20 A g−1 over 10,000 cycles. Notably, the assembled symmetric cell reveals a high capacitance of 191 F g−1 at 0.5 A g−1 with a good rate capability (77% capacitance retention at 10 A g−1) in organic electrolyte. In addition, a high energy density of 86 Wh kg−1 at the power density of 450 W kg−1 is demonstrated, while it remains 55 Wh kg−1 at a high power density of 18 kW kg−1, superior to that of many biomass-derived carbon materials. The excellent electrochemical performance offers great potential as next-generation electrode material for supercapacitor.

Carbon-based supercapacitors have attracted considerable academic and practical interest due to their advantages of low cost, high power density, and superior durability. Herein, we report the facile synthesis of hierarchical porous carbon sheets (HPCSs) featuring a high specific surface area (2788 m2 g-1), derived from pyrrole through a combination of MgO template carbonization and KOH activation. The hierarchical pores with the co-existence of micropores and mesopores were obtained in the HPCSs. Benefiting from the high surface area, well-balanced pore size distribution as well as high conductivity, the prepared HPCSs exhibited a high gravimetric specific capacitance of 226.4 F g-1 at a scan rate of 1 mV s-1 in the electrolyte of 1 M H2SO4 in the two-electrode configuration. Moreover, the excellent electrochemical long-cycle stability has been demonstrated by 10 000 cycles of rapid charging-discharging at 10 A g-1 with a capacitance retention of 97.3%. The electrochemical performance clearly indicates the promising potential of using HPCSs as electrode materials for supercapacitors.

Recently porous carbon hybrids have attracted ever-increasing attention as electrode materials for supercapacitors, but it remains a great challenge to simultaneously control their pore structure and element composition with optimal electrochemical performances. Herein, Na3PO4assistant dispersion of nano-CaCO3template in egg white was proposed to fabricate nitrogen/oxygen/phosphorus (N/O/P) co-doped 3D hierarchical porous carbon hybrids. The as-prepared carbon exhibited a high surface area (2576m2g−1), well-balanced pore size distribution with a large micropore volume (0.77cm3g−1) and multi-heteroatoms doped carbon skeleton (3.9% of N, 12.2% of O and 4.1% of P). These physicochemical advantages were synergistically beneficial to supercapacitive performances: an ultrahigh capacitance of 452Fg−1at 0.5Ag−1in 6M KOH electrolyte and excellent stability of 92.4% capacitance retention after 10000 cycles at 10Ag−1. The energy density was 22.6Wh kg−1at the power density of 225.0Wkg−1in the neutral electrolyte of 1M Li2SO4. Especially, a flexible symmetric solid-state supercapacitor was assembled, which delivered a high capacitance (166Fg−1) and excellent flexibility (86.3% capacitance retention) with bending angles to 180°. Thus, this work provides a cost-effective strategy to fabricate multi-element co-doped 3D hierarchical porous carbon and expand its application for flexible energy storage devices.