Adsorption of phenol from aqueous solution by a hierarchical micro-nano porous carbon material

A hierarchical micro-nano porous carbon material (MNC) was prepared using expanded graphite (EG), sucrose, and phosphoric acid as raw materials, followed by sucrose-phosphoric acid solution impregnation, solidification, carbonization and activation. Nitrogen adsorption and mercury porosimetry show that mixed nanopores and micropores coexist in MNC with a high specific surface area of 1978 m2·g-1 and a total pore volume of 0.99 cm3·g-1. In addition, the MNC is found to consist of EG and activated carbon with the latter deposited on the interior and the exterior surfaces of the EG pores. The thickness of the activated carbon layer is calculated to be about one hundred nanometers and is further confirmed by scanning electron microscope (SEM) and transmission election microscope (TEM). A maximum static phenol adsorption of 241.2 mg·g-1 was obtained by using MNC, slightly higher than that of 220.4 mg·g-1 by using commercial activated carbon (CAC). The phenol adsorption kinetics were investigated and the data fitted well to a pseudo-second-order model. Also, an intra-particle diffusion mechanism was proposed. Furthermore, it is found that the dynamic adsorption capacity of MNC is nearly three times that of CAC. The results suggest that the MNC is a more efficient adsorbent than CAC for the removal of phenol from aqueous solution.

Nitrogen-doped hierarchical porous carbon materials derived from diethylenetriaminepentaacetic acid (DTPA) for supercapacitors

Nitrogen-doped porous carbon materials（NPCs） have been successfully fabricated by a simple one-step pyrolysis of diethylenetriaminepentaacetic acid（DTPA） in the presence of KOH. The as-synthesized NPCs displayed a high specific surface area(3214 m;g;) and a well-defined porous structure when the annealing temperature reached 800 ℃, which showed superior electrochemical performance as supercapacitor electrode materials. Electrochemical tests showed that the NPCs achieved an impressive specific capacitance of 323 F g;at a current density of 0.5 A g;in 6 M KOH aqueous solution and an outstanding cycle stability, negligible specific capacitance decay after 5000 cycles at 10 A g;. This strategy offered a new insight into the preparation of novel carbon materials for the advanced energy storage devices, such as supercapacitors, fuel cells and lithium ion batteries.

The impact of having an oxygen-rich microporous surface in carbon electrodes for high-power aqueous supercapacitors

The growth of electrical transportation is crucially important to mitigate rising climate change concerns regarding materials supply.Supercapacitors are high-power devices,particularly suitable for public transportation since they can easily store breaking energy due to their high-rate charging ability.Additionally,they can function with two carbon electrodes,which is an advantage due to the abundance of carbon in biomass and other waste materials(i.e.,plastic waste).Newly developed supercapacitive nanocarbons display extremely narrow micropores(<0.8 nm),as it increases drastically the capacitance in aqueous electrolytes.Here,we present a strategy to produce low-cost flexible microporous electrodes with extremely high power density(>100 kW kg^(-1)),using fourty times less activating agent than traditionnal chemically activated carbons.We also demonstrate that the affinity between the carbon and the electrolyte is of paramount importance to maintain rapid ionic diffusion in narrow micropores.Finally,this facile synthesis method shows that low-cost and bio-based free-standing electrode materials with reliable supercapacitive performances can be used in electrochemistry.

Converting furfural residue wastes to carbon materials for high performance supercapacitor

Sustainable development based on the value-added utilization of furfural residues(FRs)is an effective way to achieve a profitable circular economy.This comprehensive work highlights the potential of FRs as precursor to prepare porous carbons for high performance supercapacitors(SCs).To improve the electrochemical performance of FR-based carbon materials,a facile route based on methanol pretreatment coupled with pre-carbonization and followed KOH activation is proposed.More defects could be obtained after methanol treatment,which is incline to optimize textural structure.The activated methanol treated FR-based carbon materials(AFRMs)possess high specific surface area(1753.5 m^(2) g^(-1)),large pore volume(0.85 cm^(3) g^(-1)),interconnected micro/mesoporous structure,which endow the AFRMs with good electrochemical performance in half-cell(326.1 F g^(-1) at 0.1 Ag^(-1),189.4 Fg^(-1) at 50 A g^(-1) in 6 mol L^(-1) KOH).The constructed symmetric SCs based on KOH,KOH–K_(3)Fe(CN)_(6) and KOH-KI electrolyte deliver energy density up to 8.9,9.9 and 10.6 Wh kg^(-1) with a capacitance retention of over 86%after 10,000 cycles.Furthermore,the self-discharge can be restrained by the addition of K_(3)Fe(CN)_(6) and KI in KOH electrolyte.This study provides an effective approach for high-valued utilization of FR waste.

Polysaccharide from Loquat Leaves to Prepare Hierarchical Porous Carbon as a Matrix for Active Sulfur

Fossil fuel exhaustion and overdevelopment usually lead to a recession,which is worsened by the environmental pollution.So it is of high priority to develop high-efficiency energy storage device.Here,agreen and environment-friendly strategy is devised to fabricate carbon materials from biomass.By water extraction and alcohol precipitation,polysaccharide is extracted from loquat leaves.After calcining under high temperature,hierarchical porous carbon materials(HPCM)are obtained,possessing a variety of macropores,mesopores and micropores.Such ample and hierarchical pores enable the electrolyte infiltration and the buffering of the volume expansion of sulfur in repeated electrochemical reactions.The structure stability of the entire electrode can thus be well maintained.When evaluated as the scaffold for sulfur,the electrochemical performance of carbon/sulfur composite was tested.Even after 500 cycles,the reversible capacity is retained as high as 485.4 mA·h/g at the current density of 1.6 A/g.It also offers a notable rate capability,attaining the discharge capacity of 700.7 mA·h/g at 2 C.All the electrochemical performance results prove the feasibility of the proposed strategy.

Effective exposure of nitrogen heteroatoms in 3D porous graphene framework for oxygen reduction reaction and lithium–sulfur batteries

The introduction of nitrogen heteroatoms into carbon materials is a facile and efficient strategy to regulate their reactivities and facilitate their potential applications in energy conversion and storage. However,most of nitrogen heteroatoms are doped into the bulk phase of carbon without site selectivity, which significantly reduces the contacts of feedstocks with the active dopants in a conductive scaffold. Herein we proposed the chemical vapor deposition of a nitrogen-doped graphene skin on the 3D porous graphene framework and donated the carbon/carbon composite as surface N-doped grapheme（SNG）. In contrast with routine N-doped graphene framework（NGF） with bulk distribution of N heteroatoms, the SNG renders a high surface N content of 1.81 at%, enhanced electrical conductivity of 31 S cm^（-1）, a large surface area of 1531 m^2 g^（-1）, a low defect density with a low I_D/I_G ratio of 1.55 calculated from Raman spectrum, and a high oxidation peak of 532.7 ℃ in oxygen atmosphere. The selective distribution of N heteroatoms on the surface of SNG affords the effective exposure of active sites at the interfaces of the electrode/electrolyte, so that more N heteroatoms are able to contact with oxygen feedstocks in oxygen reduction reaction or serve as polysulfide anchoring sites to retard the shuttle of polysulfides in a lithium–sulfur battery. This work opens a fresh viewpoint on the manipulation of active site distribution in a conductive scaffolds for multi-electron redox reaction based energy conversion and storage.

Lightweight foam-like nitrogen-doped carbon nanotube complex achieving highly efficient electromagnetic wave absorption

With the increased electromagnetic wave(EMW)threat to military and human health,the develop-ment of EMW-absorbing materials is crucial.Metal-organic framework derivatives containing magnetic nanoparticles and a carbon matrix are potential candidates for designing efficient EMW-absorbing mate-rials.Herein,a zeolitic imidazolate framework-67(ZIF-67)-embedded three-dimensional melamine foam is pyrolyzed to afford carbon foam-based nitrogen-doped carbon nanotube composites,named 3D foam-like CoO/Co/N-CNTs.Magnetic CoO/Co particles are confined in the dielectric carbon nanotube skeleton.The carbon nanotubes provide considerable conductive loss,while CoO/Co magnetic particles are con-ducive to providing magnetic loss and adjusting impedance matching.Moreover,the numerous defect structures introduced by heteroatomic doping(nitrogen)cause dipole polarization and simultaneously adjust impedance matching.Meanwhile,the unique porous nanotube structure promotes multiple re-flections and scattering of EMWs,further optimizing impedance matching.CoO/Co/N-CNTs composites exhibit a minimum reflection loss of−52.3 dB at a matching thickness of 2.0 mm,while the correspond-ing effective absorption bandwidth is 5.28 GHz at a matching thickness of 2.2 mm.This study reports a novel approach to fabricating a lightweight high-performance EMW-absorbing material.

Facile construction of honeycomb-shaped porous carbon electrode materials using recyclable sodium chloride template for efficient lithium storage

Carbon materials are the preferred anode materials for Li-ion batteries.Here,we propose an easy and sustainable strategy to prepare honeycomb-shaped porous carbon(HPC)electrode materials through a process involving simple calcination and subsequent water washing by using polyvinyl-pyrrolidone(PVP)as carbon source and NaCl as pore-forming agent.A controllable cavity size and distribution of the carbon materials can be readily obtained solely by adjusting the NaCl amount.Results showed that the optimized HPC sample had a relatively uniform cavity distribution and a highly porous structure.Moreover,the special honeycomb-shaped structure was conducive to the electronic conductivity of the electrode materials,provided a short path for Li-ion transport and a wide interface with the electrolyte,and buffered the volume change of active materials.The special honeycomb-shaped structure was also maintained well after long cycles,which improved electrode stability.When used as anode materials for Li-ion batteries(LIBs),the sample demonstrated excellent cycling stability and rate performance,with a high specific capacity of 230 mA hg^-1 and a reversible capacity of 197 mA hg^-1,after 1200 cycles at 2 C.Overall,we introduced a simple strategy for the potential mass production of porous carbon materials for LIBs.

Trimodel hierarchical yolk-shell porous materials TS-1@mesocarbon:Synthesis and catalytic application

Trimodal hierarchical yolk-shell materials consisting of TS-1 core and mesoporous carbon shell （YS-TS- I@MC） was successfully synthesized by using TS-l@mesosilica as hard template, sucrose as carbon source and organic base tetrapropylammonium hydroxide （TPAOH） as silica etching agent. The resultant YS-TS-I@MC contains the micropores （0.51 nm） in TS-1 core, the mesopores （2.9 rim） in carbon shell as well as a void or a stack pore between TS-1 fragements （TS-1 intercrystal mesopores, -18.4 nm）. Under the rigorous etching conditions, the crystalline structure of TS-1 core was well retained. The YS-TS- I@MC served as a good support for palladium nano-particles （Pd NPs） or Rh（OH）x species, giving rise to efficient bifunctional catalysts for the tandem reactions including one-pot synthesis of propylene oxide or amides.

Pomegranate-like C_(60)@cobalt/nitrogen-codoped porous carbon for high-performance oxygen reduction reaction and lithium-sulfur battery

Porous carbon materials play essential roles in electrocatalysis and electrochemical energy storage.It is of significant importance to rationally design and tune their porous structure and active sites for achieving high electrochemical activity and stability.Herein,we develop a novel approach to tune the morphology of porous carbon materials(PCM)by embedding fullerene C_(60),achieving improved performance of oxygen reduction reaction(ORR)and lithium-sulfur(Li-S)battery.Owing to the strong interaction between C_(60)and imidazole moieties,pomegranate-like hybrid of Ow-embedded zeolitic imidazolate framework(ZIF-67)precursor is synthesized,which is further pyrolyzed to form C_(60)-embedded cobalt/nitrogen-codoped porous carbon materials(abbreviated as C_(60)@Co-N-PCM).Remarkably,the unique structure of C_(60)@Co-N-PCM offers excellent ORR electrocatalytic activity and stability in alkaline solutions,outperforming the commercial Pt/C(20 wt.%)catalyst.Besides,C_(60)@Co-N-PCM as a novel cathode delivers a high specific capacity of-900 mAh·g^(-1) at 0.2 C rate in Li-S batteries,which is superior to the pristine ZIF-67-derived PCM without embedding C_(60).

Preparation of porous carbon directly from hydrothermal carbonization of fructose and phloroglucinol for adsorption of tetracycline

Hydrothermal carbonization of biomass is a promising method to prepare carbonaceous materials.Generally,post physical or chemical activation is necessary to increase surface area and porosity of the carbon.Herein,porous carbonaceous material（FPC） with large surface area（481.7 m^2/g） and pore volume（0.73 cm^3/g） was prepared directly from hydrothermal carbonization of fructose and phloroglucinol in hydroalcoholic mixture.Structure characteristics of the FPC and its adsorption capacity for a representative antibiotic tetracycline in aqueous solution were investigated.This work provides a green and efficient method to fabricate porous carbonaceous adsorbent that has great potential applications in chemical and environmental fields.

MoS2 nanosheet arrays supported on hierarchical porous carbon with enhanced lithium storage properties

MoS_2 nanosheet arrays supported on hierarchical nitrogen-doped porous carbon（MoS_2@C） have been synthesized by a facile hydrothermal approach combined with high-temperature calcination.The hierarchical nitrogen-doped porous carbon can serve as three-dimensional conductive frameworks to improve the electronic transport of semiconducting MoS_2.When evaluated as anode material for lithium-ion batteries,the MoS_2@C exhibit enhanced electrochemical performances compared with pure MoS_2 nanosheets,including high capacity（1305.5 mAhg^（-1） at lOOmAg^（-1））,excellent rate capability（438.4mAhg^（-1） at 1000mAg^（-1））.The reasons for the improved electrochemical performances are explored in terms of the high electronic conductivity and the facilitation of lithium ion transport arising from the hierarchical structures of MoS_2@C.

Physicochemical Properties of Coal Gasification Fly Ash from Circulating Fluidized Bed Gasifier

The coal gasification fly ash(CGFA) is an industrial solid waste from coal gasification process and needs to be effectively disposed for environmental protection and resource utilization.To further clarify the feasibility of CGFA to prepare porous carbon materials,the physicochemical properties of ten kinds of CGFA from circulating fluidized bed(CFB) gasifiers were analyzed in detail.The results of proximate and ultimate analysis show that the CGFA is characterized with the features of near zero moisture content,low volatile content as low as 0.90%-9.76%,high carbon content in the range of 37.89%-81.62%,and ultrafine particle size(d50=15.8-46.2 μm).The automatic specific surface area(SSA) and pore size analyzer were used to detect the pore structure,it is found that the pore structure of CGFA is relatively developed,and part of the CGFA has the basic conditions to be used directly as porous carbon materials.From SEM images,the microscopic morphology of the CGFA is significantly different,and they basically have the characteristics of loose and porous structure.XRD and Roman spectroscopy were used to characterize the carbon structure.The result shows that the CGFA contains abundant amorphous carbon structure,and thus the CGFA has a good reactivity and a potential to improve pore structure through further activation.Through thermal gravimetric analysis,it can be concluded that the order of reactivity of the CGFA under CO_(2) atmosphere has a good correlation with the degree of metamorphism of the raw coal.The gasification reactivity of the CGFA is generally consistent with the change trend of micropores combined with the pore structure.According to the physicochemical properties,the CGFA has a good application prospect in the preparation of porous carbon materials.