•Nitrogen-doped hierarchical porous carbon (N-HPC) was prepared by pyrolysis of magnesium citrate.•Carbon-coated Fe2O3 (Fe2O3@C) was synthesized by pyrolysis of ferric citrate.•N-HPC and Fe2O3@C were integrated to fabricate a lithium-ion hybrid electrochemical capacitor.•N-HPC//Fe2O3@C delivers 31 W h kg−1 at a high power density of 9.2 kW kg−1.Achieving high-power lithium-ion hybrid electrochemical capacitor (Li-HEC) through facile and low-cost synthesis procedures is still quite challenging. In this work, starting from daily used food additives, nitrogen-doped hierarchical porous carbon (N-HPC) was prepared through facile pyrolysis of magnesium citrate and subsequent NH3 treatment, and carbon-coated Fe2O3 (Fe2O3@C) was synthesized by thermal decomposition of ferric citrate and following heat treatment in air, respectively. As-prepared N-HPC and Fe2O3@C were separately employed as cathode and anode materials to fabricate a high-power, which delivers a high energy density of 65 W h kg−1 at 368 W kg−1, and 31 W h kg−1 at a high power density of 9.2 kW kg−1. And it remains 84.1% capacity over 1000 galvanostatic charge-discharge cycles at 1 A g−1.

Carbon materials for electrodes of capacitive deionization (CDI) process are reviewed. Electrochemical cells are briefly explained by classifying into conventional, membrane and flow-electrode CDI cells. CDI performance of carbon materials, porous carbons, including activated carbons (ACs), activated carbon fibers (ACFs), templated nanoporous carbons, carbon aerogels, carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphenes, have been reviewed in detail. The feasibility of CDI techniques is then discussed on the basis of the experimental results reported.

Two-dimensional graphitic carbon nitride (g-C3N4) nanosheets (GCNNs) have been considered as an attractive metal-free semiconductor because of their superior catalytic, optical, and electronic properties. However, it is still challenging to prepare monolayer GCNNs with a reduced lateral size in nanoscale. Herein, a highly efficient ultrasonic technique was used to prepare nanosized monolayer graphitic carbon nitride nanosheets (NMGCNs) with a thickness of around 0.6 nm and an average lateral size of about 55 nm. With a reduced lateral size yet monolayer thickness, NMGCNs show unique photo-responsive properties as compared to both large-sized GCNNs and GCN quantum dots. A dispersion of NMGCNs in water has good stability and exhibits strong blue fluorescence with a high quantum yield of 32%, showing good biocompatibility for cell imaging. Besides, compared to the multilayer GCNNs, NMGCNs show a highly improved photocatalysis under visible light irradiation. Overall, NMGCNs, characterized with monolayer and nanosized lateral dimension, fill the gap between large size (very high aspect ratio) and quantum dot-like counterparts, and show great potential applications as sensors, photo-related and electronic devices.不含金属的二维石墨相氮化碳纳米片由于具有优异的催化、光学及电学性能而受到研究者的广泛关注. 然而制备纳米级尺寸的单层石墨相氮化碳纳米片仍然存在挑战. 本文采用一种高效超声方法制备了横向尺寸约为55 nm, 厚度约为0.6 nm的单层石墨相氮化碳纳米片(NMGCNs). 由于其纳米级尺寸及单层片状结构, NMGCNs表现出与大尺寸纳米片和量子点显著不同的光响应特性. NMGCNs的水分散溶液具有良好的稳定性能和优异的荧光性能, 荧光量子产率可达32%, 所以可用于细胞荧光成像. 此外, NMGCNs表现出比多层石墨相氮化碳纳米片更优异的可见光催化性能. 独特的小尺寸及单层超薄结构使得NMGCNs在传感器和光电子等领域都具有潜在应用前景.

Developing high-performance noble metal-free and free-standing catalytic electrodes are crucial for overall water splitting. Here, nickel sulfide (Ni3S2) and nickel selenide (NiSe) are synthesized on nickel foam (NF) with a one-pot solvothermal method and directly used as free-standing electrodes for efficiently catalyzing hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution. In virtue of abundant active sites, the Ni3S2/NF and the NiSe/NF electrodes can deliver a current density of 10 mA cm−2 at only 123 mV, 137 mV for HER and 222 mV, 271 mV for OER. Both of the hierarchical Ni3S2/NF and NiSe/NF electrodes can serve as anodes and cathodes in electrocatalytic overall water-splitting and can achieve a current density of 10 mA cm−2 with an applied voltage of ∼1.59 V and 1.69 V, respectively. The performance of as-obtained Ni3S2/NF||Ni3S2/NF is even close to that of the noble metal-based Pt/C/NF||IrO2/NF system.A facile solvothermal method was proposed to synthesize free-standing nickel sulfide (Ni3S2) and nickel selenide (NiSe) electrodes, which contain high density of active sites and could serve as highly efficient catalysts for overall water splitting. Download high-res image (168KB)Download full-size image

PAN-based carbon nanofibers (PCNFs) modified with MnOx–CeO2–Al2O3 mixed oxides were prepared by the electrospinning method. The ternary complex coupled with PCNFs displays remarkable catalytic activity for NO oxidation at room temperature.

A supercapacitor that possesses excellent performance in a wide temperature range is constructed with a partially graphitized porous carbon (PGPC) as the electrode material and tetraethylammonium tetrafluoroborate/propylene carbonate (Et4NBF4/PC) as the electrolyte. The PGPC-based electrode shows a very consistent performance in a wide temperature range of −20 to 50 °C. At working temperatures as high as 50 °C and as low as −20 °C, it delivers specific capacitances of ∼148 and ∼135 F g−1, respectively, and the supercapacitors exhibit high energy densities of ∼46 and ∼43 W h kg−1. In particular, the low-temperature capacitive performance and rate capability of PGPC are much better than those of the normally used activated carbon and among the best ones ever-reported for carbon-based supercapacitors. More significantly, the PGPC-based supercapacitor shows excellent cycling performance at all tested working temperatures, with a capacitance retention of ∼98% after 1000 cycles at 5 A g−1 even when the working temperature decreases to −20 °C.

Magnesium citrate and potassium citrate are two commonly used food additives in our daily life. Herein, we prepared nitrogen-doped hierarchical porous carbon nanosheets (N-HPCNSs) through direct pyrolysis of their mixtures and subsequent NH3 treatment. The as-prepared N-HPCNS shows hierarchical porosity (specific surface area of 1735 m2 g−1 and pore volume of 1.71 cm3 g−1), and a moderate nitrogen doping of 1.7%. Moreover, it can be effectively applied in various energy storage/conversion systems. When used as supercapacitor electrodes, it shows a high specific capacitance of 128 F g−1 in organic electrolytes and retains 45% of the original capacitance even at an ultrahigh current density of 100 A g−1. It can also serve as an effective sulfur carrier in lithium–sulfur batteries. The N-HPCNS/sulfur cathode shows high discharge capacities of 1209 mA h g−1 at 0.2C and 493 mA h g−1 even at 4C. Over 500 charge/discharge cycles at 1C, it still retains a high discharge capacity of 486 mA h g−1 with an ultralow capacity loss of 0.051% per cycle and a high average coulombic efficiency of 99.4%.

N-enriched mesoporous carbon nanofibers (NMCNFs) were prepared by an electrospinning technique using graphitic carbon nitride (g-C3N4) nanosheets both as sacrificial template and N-doping source. The resultant NMCNF film has a high N-doping level of 8.6 wt% and a high specific surface area of 554 m2 g−1. When directly used as the electrode material for supercapacitor, the free-standing NMPCNF film shows a significantly improved capacitive performance including a higher specific capacitance (220 F g−1 at 0.2 A g−1) and a better rate capability (∼70% retention at 20 A g−1) than those of microporous carbon nanofiber film prepared using the same process without using g-C3N4 nanosheets (145 F g−1 at 0.2 A g−1 and ∼45% retention at 20 A g−1). Moreover, the NMCNFs show superior stability with only a ∼3% decrease of its initial capacitance after 1000 cycles at a high current density of 10 A g−1. More significantly, the energy density of a symmetrical supercapacitor (SC) based on the NMPCNF film can reach 12.5 Wh kg−1 at a power density of 72 W kg−1.

•A LIC is constructed with LTO/C and PGM as the anode and cathode, respectively.•The optimized LIC delivers a maximum energy density of 72 Wh kg−1 at 650 W kg−1.•The LIC still reaches 40 Wh kg−1 at 8.3 kW kg−1.•The LIC retains 65% after 1000 cycles even at a high current density of 10 A g−1.A Li-ion capacitor (LIC) is constructed with Li4Ti5O12/C hybrid as the negative electrode and 3D porous graphene macroform (PGM) as the positive electrode. After optimizing the mass ratio (m+/m−) of the electrode materials with the value of 2, the as-fabricated LIC delivers a maximum energy density of 72 Wh kg−1 with the power density of 650 W kg−1 in a voltage range of 1.0–3.0 V. Furthermore, the energy density of the LIC reaches 40 Wh kg−1 even at a high power density of 8.3 kW kg−1. More significantly, the LIC exhibits a good cycling stability with the retention of 65% after 1000 cycles at a high current density of 10 A g−1, suggesting great potential application in energy storage of the LIC.A Li-ion capacitor constructed with a Li4Ti5O12/C hybrid based anode and a porous graphene macroform based cathode is demonstrated with both high energy and power densities.

•Novel continuous hollow carbon nanofibers with randomly distributed open swells.•NH3 activation leads to high content of N-doping and superior areal capacitance.•The HACNFs can be directly used as the electrodes for supercapacitor.•The HACNFs electrode shows excellent rate capability and cycling stability.Nitrogen-doped hollow activated carbon nanofibers (HACNFs) have been prepared by the concentric electrospinning and the following NH3 activation. The as-obtained samples were directly used as supercapacitor electrode without binders and conductive additives. Owing to the unique hollow architecture and high N-doping level (8.2%), the HACNFs exhibit a high specific capacitance of 197 F g−1 at 0.2 A g−1, which is 1.33 times than that of the solid electrospun nanofibers activated in the same condition. The samples also possess a superior rate capability of 72.1% (143 F g−1) at 20 A g−1 and long-term cycling stability with a retention of 98.6% after 1000 cycles at 5 A g−1 in 6 M KOH.

It is quite desirable but challenging to prepare highly active materials for various energy storage applications at low cost. Here, an efficient strategy to produce nitrogen-enriched hierarchical porous carbon (N-HPC) is reported by facile pyrolysis of magnesium citrate and subsequent NH3 treatment. As-prepared N-HPC presents a developed hierarchical micro- and trimodal meso-porosity with a high specific surface area of 1290 m2 g−1 and pore volume of 3.04 cm3 g−1. It also shows an abundant nitrogen doping of 3.6%. When used for electrochemical electrodes in supercapacitors and lithium–sulfur (Li–S) batteries, significantly enhanced performances have been obtained compared with commercially available activated carbon. In supercapacitor testing, the N-HPC electrode shows a specific capacitance of 101 F g−1 in a nonaqueous electrolyte. And the capacitance retains 67% even at a 200-fold charge/discharge rate. Moreover, its performance in Li–S batteries is more outstanding. It enables a very high sulfur loading (76.2% by weight) and the resulting N-HPC/S cathode shows high discharge capacities of 1153 mA h g−1sulfur (or 702 mA h g−1electrode) at 0.2C and 671 mA h g−1 even at 4C. And it still remains 600 mA h g−1 over 300 charge/discharge cycles at 1C with an average coulombic efficiency of 99.0%.

•A novel nitrogen-enriched mesoporous carbon nanospheres/graphene (N-GMCS) nanocomposite is designed for lithium ion capacitor (LIC) cathode.•The N-GMCS cathode shows both superior rate performance and high mass density.•The N-GMCS cathode was coupled with prelithiated microcrystalline graphite (PLMG) anode to intergrate a high-performance hybrid LIC system.•The N-GMCS//PLMG system shows high energy density (80 W h kg−1, 68.6 W h L−1) and state-of-the-art maximum power density (352 kW kg−1, 292 kW L−1).•The presented strategy offers a new perspective in designing ultrahigh-rate LIC system.Lithium-ion capacitors (LICs) are novel advanced electrochemical energy storage (EES) systems integrating both battery and capacitor functions. Most efforts for developing high-power LICs are currently dedicated to nanostructure design of battery-type anodes, which in general results in low packing densities and cannot fundamentally improve the slow Faradaic reaction. Up to now, little attention has been focused on the effects of porous carbon cathodes and the reasonable matching of cathode/anode on the power performance of LICs. Herein, a novel nitrogen-enriched mesoporous carbon nanospheres/graphene (N-GMCS) nanocomposite is demonstrated, which shows simultaneously hierarchical porous structure, 3D conductive network, as well as very high mass density. When such N-GMCS cathode is coupled with prelithiated microcrystalline graphite (PLMG) anode, the integrated device shows quite high packing density which is highly desirable in EES systems. In particular, the PLMG anode in N-GMCS//PLMG system breaks the limitation of slow Faradaic reaction and lithium-ion bulk diffusion, providing an ultrafast capacitor-like electrochemical response. Quite attractive maximum energy density (80 W h kg−1, 68.6 W h L−1) and state-of-the-art maximum power density (352 kW kg−1, 292 kW L−1) can be achieved in N-GMCS//PLMG, which are 5 and 2.8 times as large as those of the supercapacitor counterpart, respectively.

Mildly expanded graphite (MEG) was synthesized by using perchloric acid as both intercalating agent and oxidizing agent. Its performance as anode material for lithium ion battery was investigated. SEM, XRD, TEM, nitrogen adsorption and TGA/DSC were used to characterize the sample. Charge/discharge tests show that the MEG exhibits a rate capacity as high as 397 mAh/g at 0.2 C and 250 mAh/g at 1.6 C.

•Soft-templated ordered mesoporous carbon nanospheres (OMCNS) were prepared.•OMCNS possesses hierarchical porous structure and a high mass density.•The OMCNS electrode exhibits high gravimetric and volumetric capacitance.•The OMCNS electrode shows a good excellent rate capability.Ordered mesoporous carbon nanospheres (OMCNS) were prepared through a facile soft-template method and used as electrode materials for high-performance supercapacitors. The obtained OMCNS possesses a hierarchical porous structure and a relatively high mass density. And the OMCNS electrode exhibits both high gravimetric (173 F g− 1) and volumetric (107 F cm− 3) capacitances simultaneously, as well as a high rate capability and a long-term cycling stability.

Zinc-based metal–organic frameworks/graphene oxide (MOF-5/GO) composites were synthesized via the solvothermal method. The materials were characterized by scanning electron microscopy (SEM), nitrogen adsorption, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS), and their performances for hydrogen sulfide (H2S) removal were evaluated by dynamic testing at room temperature. The composites exhibit microporous structure with a small amount of mesopores, and the structure is highly dependent on the amount of GO loaded. The surface area and pore volume first increase and then decrease with increasing GO, reaching the maximum value when the GO ratio is 5.25%. The composites exhibit high adsorption capacities for H2S, with the maximum uptakes reaching up to 130.1 mg/g. Although the loading of GO makes a contribution to the enhancement of dispersive force in the porous structure, it leads to the crystal distortion of MOF-5. The introduction of glucose can restrain this distortion to maintain the structure stability. A good match between GO and glucose have a well synergy effect to develop the porous structure, resulting in the highest H2S adsorption capacity.Keywords: composites; desulfurization; glucose; graphene oxide; hydrogen sulfide; metal−organic frameworks;

Adsorption of water vapor on graphene nanosheets (GNS) derived by vacuum-promoted low-temperature exfoliation method was investigated using a volumetric system. The pristine and thermally modified GNS were characterized with scanning electron microscopy (SEM) observation, Fourier transform infrared (FT-IR) analysis and nitrogen adsorption–desorption. The results show that the absorbed amount of water vapor against the pristine GNS can reach 249 cm3/g at 20 °C, and the capability of water vapor adsorption was weakened by heat treatment at 500 °C and 700 °C, the isosteric heat of water vapor adsorption against GNS is 42.6 kJ/mol based on the adsorption isotherms at 10 °C and 30 °C.Highlights► The water vapor adsorption on graphene nanosheets (GNS) was investigated experimentally by volumetric system. ► GNSs exhibit a significant adsorption against water vapor, the water adsorbed amount of graphene can reach 249 cm3/g at 20 °C. ► The heat-treatment reduced the hydrophilic functional groups that resulted in the decrease of water vapor adsorption. ► The isosteric heat of water vapor adsorption against GNS is 42.6 kJ/mol, which is close to physical adsorption.

Phenolic resin-based porous carbon nanofibers (PCNFs) with large surface area and narrow pore size distribution have been successfully prepared using novolac-type phenolic resin as precursor. The high molecular weight precursor was first synthesized in this study, then was dissolved in methanol. The PCNFs were finally obtained through electrospinning the phenolic resin polymer solution followed by successive curing and carbonization without activation. The N2 adsorption/desorption isotherms reveal that the PCNFs have high specific surface area about 812 m2/g, the pore size falls in the range of 0.4–0.7 nm and the pore volume is 0.91 cm3/g. The vapor adsorption testing demonstrated that PCNFs exhibited different adsorption performance for ethanol and water.

Graphene nanosheets (GNSs) that were obtained by vacuum-promoted low-temperature exfoliation were used to adsorb lead ions from an aqueous system. The pristine and thermally modified GNSs were characterized with scanning electron microscopy observation and X-ray photoelectron spectroscopy analysis. It was interestingly found that the adsorption against lead ions was enhanced by heat treatment, although the oxygen complexes of GNSs showed a significant decrease. In addition, lead ion uptake resulted in an increase in the pH value of the solution. It is supposed that the Lewis basicity of GNSs is improved by heat treatment under a high vacuum, in favor of simultaneous adsorption of lead ions and protons onto GNSs.

Ultrafine carbon fiber webs were prepared from oxidatively stabilized electrospun poly(acrylonitrile) fibers, followed by carbonization or by further activation with steam. Capacitive de-ionization was evaluated in the batch mode. It was found that the webs exhibited considerable electrical adsorption, which was enhanced by activation with a faster electrosorption rate and a higher electrosorption capacity.

Mesoporous carbon nanosheets with high surface areas and large total pore volumes were prepared using tubular halloysite as inorganic matrix and furfuryl alcohol (FA) as carbon precursor by a template-like method. Field emission scanning electron microscope, high-resolution transmission electron microscopy (HRTEM) and nitrogen adsorption analysis were employed to characterize the morphologies and pore structures of the samples. It is found that tunable mesoporous carbons can be obtained by adjusting FA volume concentration. Lowering FA concentration leads to an increase in the BET specific surface area and narrowing of the mesopore size distribution.

A strain of bacterium (BC027) for quinoline degradation was inoculated on the activated bamboo charcoal (ABC) substrate. SEM observation showed that the bacterium grew well on the charcoal substrate and thus obtained biologically activated bamboo charcoal (BABC). The investigation on quinoline removal showed that BABC has greater capacity for removing quinoline than ABC or dissociate BC027. The removal ability of BABC is influenced by initial concentration and domestication process. Adsorption of carbon substrate only occurred at the beginning stage, while it had no effect on the bacterium inoculation and activity. The bacteria enhanced the treatment capacity of ABC and prolonged its usage life.

One kind of novel hierarchical carbon nanotubes/bamboo charcoal (CNTs/BC) was prepared by CVD growth of CNTs on low-cost bamboo charcoal (BC). The obtained CNTs/BC composites were characterized by SEM and TEM observations. Adsorption of copper ions by CNTs/BC in aqueous solution was investigated. The adsorbed copper species were analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that the CNTs/BC composites exhibited higher adsorption capacities toward aqueous copper ions than the pristine BCs and commercial activated bamboo charcoals (ABCs) with a specific surface area of over 1000 m2 g−1. The adsorption capacity increases with nanotube growth time. Moreover, nitric acid treatment was used for the oxidation of the carbon surface. The surface functional groups of carbon samples were analyzed by Fourier transform infrared spectroscopy (FT-IR), Boehm’s titration method, and zeta potential analysis. It was found that nitric acid treatment for CNTs/BC produced more oxygen-containing functional groups, leading to a higher copper ion adsorption capability than conventional carbon adsorbents under the same treatment condition.

Photoactive TiO2 was homogeneously mounted on PAN-based activated carbon cloths (ACCs) by a process of dip-coating and subsequent annealing in nitrogen atmosphere. The crystallinity of TiO2 and pore structure of hybrids was characterized by XRD and N2 adsorption. The adsorption and photocatalytic activity for TiO2-mounted ACC towards methylene blue (MB) solution was investigated. The results showed that the coating of TiO2 gel resulted in a marked decrease in specific surface area and pore volume from the pristine ACC, which was recovered gradually with increasing treatment temperature. Besides crystallinity of TiO2 can be modified by heat treatment, its pore structure can be postulated by adding different amount of polyethylene glycol (PEG). Both pore structure of hybrids and crystallinity of TiO2 as well as the carbon residue produced by PEG pyrolysis had effects on their adsorptive and photocatalytic performances of TiO2-mounted ACCs. It would be a promising technology to integrate adsorption and photocatalysis for TiO2-mounted ACCs.

A supercapacitor that possesses excellent performance in a wide temperature range is constructed with a partially graphitized porous carbon (PGPC) as the electrode material and tetraethylammonium tetrafluoroborate/propylene carbonate (Et4NBF4/PC) as the electrolyte. The PGPC-based electrode shows a very consistent performance in a wide temperature range of −20 to 50 °C. At working temperatures as high as 50 °C and as low as −20 °C, it delivers specific capacitances of ∼148 and ∼135 F g−1, respectively, and the supercapacitors exhibit high energy densities of ∼46 and ∼43 W h kg−1. In particular, the low-temperature capacitive performance and rate capability of PGPC are much better than those of the normally used activated carbon and among the best ones ever-reported for carbon-based supercapacitors. More significantly, the PGPC-based supercapacitor shows excellent cycling performance at all tested working temperatures, with a capacitance retention of ∼98% after 1000 cycles at 5 A g−1 even when the working temperature decreases to −20 °C.

Magnesium citrate and potassium citrate are two commonly used food additives in our daily life. Herein, we prepared nitrogen-doped hierarchical porous carbon nanosheets (N-HPCNSs) through direct pyrolysis of their mixtures and subsequent NH3 treatment. The as-prepared N-HPCNS shows hierarchical porosity (specific surface area of 1735 m2 g−1 and pore volume of 1.71 cm3 g−1), and a moderate nitrogen doping of 1.7%. Moreover, it can be effectively applied in various energy storage/conversion systems. When used as supercapacitor electrodes, it shows a high specific capacitance of 128 F g−1 in organic electrolytes and retains 45% of the original capacitance even at an ultrahigh current density of 100 A g−1. It can also serve as an effective sulfur carrier in lithium–sulfur batteries. The N-HPCNS/sulfur cathode shows high discharge capacities of 1209 mA h g−1 at 0.2C and 493 mA h g−1 even at 4C. Over 500 charge/discharge cycles at 1C, it still retains a high discharge capacity of 486 mA h g−1 with an ultralow capacity loss of 0.051% per cycle and a high average coulombic efficiency of 99.4%.

PAN-based carbon nanofibers (PCNFs) modified with MnOx–CeO2–Al2O3 mixed oxides were prepared by the electrospinning method. The ternary complex coupled with PCNFs displays remarkable catalytic activity for NO oxidation at room temperature.

Carbon materials for electrodes of capacitive deionization (CDI) process are reviewed. Electrochemical cells are briefly explained by classifying into conventional, membrane and flow-electrode CDI cells. CDI performance of carbon materials, porous carbons, including activated carbons (ACs), activated carbon fibers (ACFs), templated nanoporous carbons, carbon aerogels, carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphenes, have been reviewed in detail. The feasibility of CDI techniques is then discussed on the basis of the experimental results reported.