Waste to wealth: Oxygen-nitrogen-sulfur codoped lignin-derived carbon microspheres from hazardous black liquors for high-performance DSSCs

Carbon materials are effective substitutes for Pt counter electrodes(CEs) in dye-sensitized solar cells(DSSCs). However, many of these materials, such as carbon nanotubes and graphene, are expensive and require complex preparation process. Herein, waste lignin, recycled from hazardous black liquors,is used to create oxygen-nitrogen-sulfur codoped carbon microspheres for use in DSSC CEs through the facile process of low-temperature preoxidation and high-temperature self-activation. The large number of ester bonds formed by preoxidation increase the degree of cross-linking of the lignin chains, leading to the formation of highly disordered carbon with ample defect sites during pyrolysis. The presence of organic O/N/S components in the waste lignin results in high O/N/S doping of the pyrolysed carbon,which increases the electrolyte ion adsorption and accelerates the electron transfer at the CE/electrolyte interface, as confirmed by density functional theory(DFT) calculations. The presence of inorganic impurities enables the construction of a hierarchical micropore-rich carbon structure through the etching effect during self-activation, which can provide abundant catalytically active sites for the reversible adsorption/desorption of electrolyte ions. Under these synergistic effects, the DSSCs that use this novel carbon CE achieve a quite high power-conversion efficiency of 9.22%. To the best of our knowledge, the value is a new record reported so far for biomass-carbon-based DSSCs.

Novel Bilayer-Shelled N,O-Doped Hollow Porous Carbon Microspheres as High Performance Anode for Potassium-Ion Hybrid Capacitors

With the advantages of high energy/power density,long cycling life and low cost,dual-carbon potassium ion hybrid capacitors(PIHCs)have great potential in the field of energy storage.Here,a novel bilayer-shelled N,O-doped hollow porous carbon microspheres(NOHPC)anode has been prepared by a self-template method,which is consisted of a dense thin shell and a hollow porous spherical core.Excitingly,the NOHPC anode possesses a high K-storage capacity of 325.9 mA h g^(−1)at 0.1 A g^(−1)and a capacity of 201.1 mAh g^(−1)at 5 A g^(−1)after 6000 cycles.In combination with ex situ characterizations and density functional theory calculations,the high reversible capacity has been demonstrated to be attributed to the co-doping of N/O heteroatoms and porous structure improved K+adsorption and intercalation capabilities,and the stable long-cycling performance originating from the bilayer-shelled hollow porous carbon sphere structure.Meanwhile,the hollow porous activated carbon microspheres(HPAC)cathode with a high specific surface area(1472.65 m^(2)g^(−1))deriving from etching NOHPC with KOH,contributing to a high electrochemical adsorption capacity of 71.2 mAh g^(−1)at 1 A g^(−1).Notably,the NOHPC//HPAC PIHC delivers a high energy density of 90.1 Wh kg^(−1)at a power density of 939.6 W kg^(−1)after 6000 consecutive charge-discharge cycles.

Insights into the thermochemical evolution of maleic anhydride-initiated esterified starch to construct hard carbon microspheres for lithium-ion batteries

Starch,as a typical polysaccharide with natural spherical morphology,is not only a preferred precursor for preparing carbon materials but also a model polymer for investigating thermochemical evolution mechanisms.However,starch usually suffers from severe foaming and low carbon yield during direct pyrolysis.Herein,we report a simple and eco-friendly dry strategy,by maleic anhydride initiating the esterification of starch,to design carbon microspheres against the starch foaming.Moreover,the infuence of ester grafting on the pyrolytic behavior of starch is also focused.The formation of ester groups in precursor guarantees the structural stability of starch-based intermediate because it can promote the accumulation of unsaturated species and accelerate the water elimination during pyrolysis.Meanwhile,the esterification and dehydration reactions greatly deplete the primary hydroxyl groups in the starch molecules and thus the rapid levoglucosan release is inhibited,which well keeps the spherical morphology of starch and ensures the high carbon yield.In further exploration as anode materials for Lithium-ion batteries,the obtained carbon microspheres exhibit good cyclability and rate performance with a reversible capacity of 444 m Ah g^(-1)at 50 m A g^(-1).This work provides theoretical fundamentals for the controllable thermal transformation of biomass towards wide applications.

Hollow Carbon Microspheres/MnO_2 Nanosheets Composites:Hydrothermal Synthesis and Electrochemical Behaviors

This article reported the electrochemical behaviors of a novel hollow carbon microspheres/manganese dioxide nanosheets(micro-HC/nano-MnO2) composite prepared by an in situ self-limiting deposition method under hydrothermal condition. The results of scanning electron microscopy reveal that MnO2 nanosheets homogeneously grow onto the surface of micro-HC to form a loose-packed microstructure. The quantity of MnO2 required in the electrode layer has thereby been reduced significantly, and higher specific capacitances have been achieved. The micro-HC/nano-MnO2 electrode presents a high capacitance of 239.0 F g-1 at a current density of 5 m A cm-2, which is a strong promise for high-rate electrochemical capacitive energy storage applications.

Understanding the improved performance of sulfur-doped interconnected carbon microspheres for Na-ion storage

As one of the low-cost energy storage systems,Na-ion batteries(NIBs)have received tremendous attention.However,the performance of current anode materials still cannot meet the requirements of NIBs.In our work,we obtain sulfur-doped interconnected carbon microspheres(S-CSs)via a simple hydrothermal method and subsequent sulfurizing treatment.Our S-CSs exhibit an ultrahigh reversible capacity of 520 mAh g^(-1) at 100 mA g^(-1) after 50 cycles and an excellent rate capability of 257 mAh g^(-1),even at a high current density of 2 A g^(-1).The density functional theory calculations demonstrate that sulfur doping in carbon favors the adsorption of Na atom during the sodiation process,which is accountable for the performance enhancement.Furthermore,we also utilize operando Raman spectroscopy to analyze the electrochemical reaction of our S-CSs,which further highlights the sulfur doping in improving Na-ion storage performance.

Nitrogen-doped lignin based carbon microspheres as anode material for high performance sodium ion batteries

Nitrogen-doped lignin-based carbon microspheres are synthesized using 3-aminophenol as a nitrogen source by the hydrothermal method.The structural change and the effect on the electrochemical properties are systematically investigated. Nitrogen-doped lignin-based carbon microspheres represent well-developed spherical morphology with many active sites, ultramicroporous(< 0.7 nm) structure, and large interlayer spacing. Consistent with the obtained physical structures and properties, the nitrogen-doped carbon microspheres exhibit fast sodium ion adsorption/intercalation kinetic process and excellent electrochemical performance. For example, a reversible specific capacity of 374 m Ah g^(-1) at 25 m A g^(-1) with high initial coulombic efficiency of 85% and high capacitance retention of 90% after 300 cycles at 100 m A g^(-1) and stable charge/discharge behavior at different current density is obtained. The additional defects and abundant ultramicroporous structure can enhance sloping capacity, and large interlayer spacing is considered to be the reason for improving plateau capacity.

Preparation and Characterization of Carbon Microspheres From Waste Cotton Textiles By Hydrothermal Carbonization

Carbon microspheres were prepared from waste cotton fibers by hydrothermal carbonization(HTC)with the addition of copper sulphate in this work.The important influence factors,temperature,concentration of copper sulphate,resident time were explored here.The smooth and regular carbon microspheres could be formed at 330°C with 0.15 wt%copper sulphate after 6 h from waste cotton fibers.The crystal structures of cotton fibers were destructed in a short resident time with 0.15 wt%copper sulphate from SEM images and XRD patterns of solid products.This strategy provides a new,mild and efficient method to prepare carbon microspheres from waste cotton fibers by HTC.FTIR spectra verified that the abundant functional groups existed on the surface of synthesized carbon microspheres.From XPS and element analysis results,the copper sulphate participated in the forming process of carbon microspheres indeed.The presence of copper sulphate in the carbon microspheres provided a possibility for the application in antibacterial field.Besides,the catalytic mechanism of copper sulphate on the hydrolysis and carbonization of waste cotton fibers were also discussed.In conclusion,the copper sulphate is an efficient agent for preparing carbon microspheres by HTC from waste cotton fibers.

A dandelion-like carbon microsphere/MnO_2 nanosheets composite for supercapacitors

This article reported the electrochemical performance of a novel cabon microsphere/MnO2nanosheets(CMS/MnO2) composite prepared by a in situ self-limiting deposition method under hydrothermal condition. The results of scanning electron microscopy(SEM) and transmission electron microscopy(TEM) revealed that MnO2nanosheets homogeneously grew onto the surface of CMS to form a loose-packed and dandelion-like core/shell microstructure. The unique microstructure plays a basic role in electrochemical accessibility of electrolyte to MnO2active material and a fast diffusion rate within the redox phase. The results of cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrometry indicated that the prepared CMS/MnO2composite presented high capacitance of 181 F g-1and long cycle life of 61% capacity retention after 2000 charge/discharge cycles in 1 mol/L Na2SO4solution, which show strong promise for high-rate electrochemical capacitive energy storage applications.

Selective Hydrogenation of Maleic Anhydride to Succinic Anhydride over Nickel Catalyst Supported on Carbon Microspheres

The colloidal carbon microspheres(CMS)were prepared by the hydrothermal method.The nickel catalysts supported on carbon microspheres(Ni/CMS)were further prepared and were characterized by the Fourier transform infrared spectroscopy(FTIR),the X-ray diffraction(XRD),the scanning electron microscopy(SEM),the transmission electron microscopy(TEM),and the N_(2)adsorption technique.The selective hydrogenation of maleic anhydride(MA)to succinic anhydride(SA)over the Ni/CMS catalysts was investigated.The results indicated that the Ni/CMS catalyst,which was prepared with glucose as carbon source and calcined at 500℃,exhibited the best performance.The hydrogen pressure,reaction temperature,and reaction time could significantly affect the conversion of maleic anhydride during the hydrogenation reaction.A 98.4%conversion of MA and an 100%selectivity to SA were achieved over the Ni/CMS catalyst in acetic anhydride solvent under mild conditions covering a temperature of 90℃,a H2 pressure of 1.0 MPa,and a reaction time of 3 h.

Preparation and Self-assembly of Chitosan/Carbon Microsphere Composite

Carbon-based films were synthesized by self-assembly of chitosan-encapsulated carbon microsphere （CMS@CS） composite. First, carbon microspheres （CMSs） prepared by chemical vapor deposition were modified by HNO3 and H2O2. Second, oxidized CMSs were modified by chitosan （CS）. Finally, CMS@CS was self-assembled by vertical deposition, in which suspension concentration and deposition temperature on the quality of self-assembling film were investigated. Field emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, thermogravimetry, and Fourier transformation infrared spectrometry were employed to characterize the morphology and structure of the samples. The results show that CMSs modified by CS had uniform particle size and good dispersion, CMS@CS was self-assembled into a dense film, the film thickened with increasing suspension concentration at fixed temperature, and more ordered film was obtained at 1 wt% of suspension concentration and 50 ℃. The ultraviolet-visible absorption spectra show that the absorbance of CMS@CS film grew steadily with increasing suspension concentration and that the CMSs with oxygen-containing groups have a good assembling performance to form composite films with CS.

Impact of H_(2)S on Hg^(0)capture performance over nitrogen-doped carbon microsphere sorbent:experimental and theoretical insights

A nitrogen-doped carbon microsphere sorbent with a hierarchical porous structure was synthesized via aggregation-hydrothermal carbonization.The Hg^(0)adsorption performance of the nitrogen-doped carbon microsphere sorbent was tested and compared with that of the coconut shell activated carbon prepared in the laboratory.The effect of H_(2)S on Hg^(0)adsorption was also investigated.The nitrogen-doped carbon microsphere sorbent exhibited superior mercury removal performance compared with that of coconut shell activated carbon.In the absence of H_(2)S at a low temperature(≤100℃),the Hg^(0)removal efficiency of the nitrogen-doped carbon microsphere sorbent exceeded 90%.This value is significantly higher than that of coconut shell activated carbon,which is approximately 45%.H_(2)S significantly enhanced the Hg^(0)removal performance of the nitrogen-doped carbon microsphere sorbent at higher temperatures(100–180℃).The hierarchical porous structure facilitated the diffusion and adsorption of H_(2)S and Hg^(0),while the nitrogen-containing active sites significantly improved the adsorption and dissociation capabilities of H_(2)S,contributing to the generation of more active sulfur species on the surface of the nitrogen-doped carbon microsphere sorbent.The formation of active sulfur species and HgS on the sorbent surface was further confirmed using X-ray photoelectron spectroscopy and Hg^(0)temperature-programmed desorption tests.Density functional theory was employed to elucidate the adsorption and transformation of Hg^(0)on the sorbent surface.H_(2)S adsorbed and dissociated on the sorbent surface,generating active sulfur species that reacted with gaseous Hg^(0)to form HgS.

MOFs derived magnetic porous carbon microspheres constructed by core-shell Ni@C with high-performance microwave absorption

Lightweight and high-performance are two determining factors for metal-organic-frameworks(MOFs)derived microwave absorbers.However,most of the reported MOFs derived absorbers usually possess high filler loading.Herein,a series of MOFs derived magnetic porous carbon microspheres with tunable diameter and high specific surface area have been synthesized via a pyrolysis process.The synthesized magnetic porous carbon microspheres,constructed by uniformly distributed core-shell Ni@C,exhibit high-performance microwave absorption with a low filler loading of 10 wt%.Considering the mciro-mesoporous structures,matched impedance,strong conductive loss,enhanced dipolar/interfacial polarization as well as strong magnetic coupling network,a minimum reflection loss of-60 dB and an absorption bandwidth of 7.0 GHz can be achieved at 2.6 mm.Moreover,the bandwidth reaches as wide as 10.2 GHz when the thickness is 4 mm.In addition,compared with other MOFs derived absorbers,this work provides us a simple strategy for the synthesis of porous carbon microspheres with lightweight and high-performance microwave absorption for practical applications.

Electrosprayed porous Fe3O4/carbon microspheres as anode materials for high-performance lithium-ion batteries

Porous Fe3Odcarbon microspheres （PFCMs） were successfully fabricated via a facile electrospray method and subsequent heat treatment, using ferrous acetylacetonate, carbon nanotubes （CNTs）, Ketjen black （KB）, polyvinylpyrrolidone （PVP）, and polystyrene （PS） as raw materials. The porous carbon sphere framework decorated with well-dispersed CNTs and KB exhibits excellent electronic conductivity and acts as a good host to confine the Fe304 nanoparticles. The abundant mesopores in the carbon matrix derived from polymer pyrolysis can effectively accommodate the volume changes of F%O4 during the charge/ discharge process, facilitate electrolyte penetration, and promote fast ion diffusion. Moreover, a thin amorphous carbon layer on the Fe304 nanoparticle formed during polymer carbonization can further alleviate the mechanical stress associated with volume changes, and preventing aggregation and exfoliation of F%O4 nanoparticles during cycling. Therefore, as anode materials for lithium-ion batteries, the PFCMs exhibited excellent cycling stability with high specific capacities, and outstanding rate performances. After 130 cycles at a small current density of 0.1 A-g-1, the reversible capacity of the PFCM electrode is maintained at almost 1,317 mAh-g-1. High capacities of 746 and 525 mAh-g-1 were still achieved after 300 cycles at the larger currents of I and 5 A-g-1, respectively. The optimized structure design and facile fabrication process provide a promising way for the utilization of energy storage materials, which have high capacities but whose performance is hindered by large volume changes and poor electrical conductivity in lithium or sodium ion batteries.

Preparation and adsorption property of novel inverse-opal hierarchical porous N-doped carbon microspheres

The design of pore structure is the key factor for the performance of porous carbon spheres.In this wo rk,novel micron-sized colloidal crystal microspheres consisting of fibrous silica(F-SiO_(2)) nanoparticles are firstly prepared by water-evapo ration-induced self-assembly of F-SiO_(2) nanoparticles in the droplets of an inverse emulsion system to be used as sacrificial templates.Acrylonitrile(AN) was infiltrated in the voids of the F-SiO_(2) colloidal crystal microspheres,and in-situ induced by ^(60)Co γ-ray to polymerize into polyacrylonitrile(PAN).After the PAN-infiltrated F-SiO_(2) colloidal crystal microspheres were carbonized and etched with HF solution,novel micron-sized inverse-opal N-doped carbon(IO-NC) microspheres consisting of hollow carbon nanoparticles with a hierarchical macro/meso-porous inner surface were obtained.The IO-NC microspheres have a specific surface area as high as 266.4 m^(2)/g and a molar ratio of C/N of 5.They have a good dispersibility in water,and show a high adsorption capacity towards rhodamine B(RhB) up to 137.28 mg/(g microsphe re).This work offers a way to obtain novel micron-sized hierarchical macro/meso-porous N-doped carbon microspheres,which opens a new idea to prepare high-performance hierarchical porous carbon materials.

Chitin-derived fibrous carbon microspheres as support of polyamine for remarkable CO_(2) capture

Supported polyamines are promising candidates for the chemical adsorption of CO_(2),the performance of which is highly dependent on the porous structure of supports.In this work,we synthesized a kind of fibrous carbon microspheres(FCMs)from environmentally friendly and low-cost chitin.The synthesized FCMs have microspheric morphology and fibrous sub-architecture,and the carbon fibers interweave to form pores with large diameters.The flexibility of the pores formed by the interweaving of carbon fibers also enable the supporting of high quantity of polyamines.Given these features,pentaethylenehexamine(PEHA)was physically dispersed in the pores of FCMs to prepare PEHA/FCMs adsorbents,which were systematically characterized and investigated for CO_(2) capture performance.It is found that PEHA/FCMs adsorbents show excellent ability for CO_(2) adsorption,with the highest CO_(2) capacity of 3.90 mmol g^(-1) at 75℃ when using 10 vol%of CO_(2) for determinations.The reversibility of PEHA/FCMs adsorbents for CO_(2) adsorption is also fairly good,and PEHA/FCMs adsorbents have strong ability for the selective adsorption of low-content CO_(2) from N_(2).

In-situ synthesis of N, S co-doped hollow carbon microspheres for efficient catalytic oxidation of organic contaminants

Metal-free heteroatom doped nanocarbons are promising alternatives to the metal-based materials in catalytic ozonation for destruction of aqueous organic contaminants. In this study, N, S co-doped hollow carbon microspheres (NSCs) were synthesized from the polymerization products during persulfate wet air oxidation of benzothiazole. The contents of doped N and S as well as the structural stability were maneuvered by adjusting the subsequent N_(2)-annealing temperature. Compared with the prevailing single-walled carbon nanotubes, the N_(2)-annealed NSCs demonstrated a higher catalytic ozonation activity for benzimidazole degradation. According to the quantitative structure-activity relationship (QSAR) analysis, the synergistic effect between the graphitic N and the thiophene-S which redistributed the charge distribution of the carbon basal plane contributed to the activity enhancement of the N_(2)-annealed NSCs. Additionally, the hollow structure within the microspheres served as the microreactor to boost the mass transfer and reaction kinetics via the nanoconfinement effects. Quenching and electron paramagnetic resonance (EPR) tests revealed that benzimidazole degradation was dominated by the produced singlet oxygen (^(1)O_(2)) species, while hydroxyl radicals (^(·)OH) were also generated and participated. This study puts forward a novel strategy for synthesis of heteroatom-doped nanocarbons and sheds a light on the relationship between the active sites on the doped nanocarbons and the catalytic performance.

Structural evolution of carbon aerogel microspheres by thermal treatment for high–power supercapacitors

In this work, a series of carbon aerogel microspheres（CAMs） with tailored pore structures were successfully prepared via a sol-gel method and subsequent heat-treatment at various temperatures from 600 to 1600 ℃. The effects of heat-treatment temperature（HTT） on the CAM microstructure were systematically investigated by physical and chemical characterization. The electrical conductivity increased by up to 250 S/cm and mesopores with high electrolyte accessibility developed in the CAM with increasing HTT. However, the specific surface area（SSA） decreased for HTTs from 1000 to 1600 ℃. The results show that these two factors should be finely balanced for further applications in high power supercapacitors.The CAMs carbonized at 1000 ℃ had the highest SSA（1454 m^2/g）, large mesoporous content（20%） and favorable conductivity（71 S/cm）. They delivered a high energy density of 38.4 Wh/kg at a power density of 0.17 kW/kg. They retained an energy density of 25.5 Wh/kg even at a high power density of 10.2 kW/kg,and a good rate capability of 84% after 10,000 cycles. This performance is superior to, or at least comparable to, those of most reported carbon materials.

Effect of Ultrasonication on the Properties of Multi-walled Carbon Nanotubes/Hollow Glass Microspheres/Epoxy Syntactic Foam

Multi-walled carbon nanotubes（MWCNTs） reinforced hollow glass microspheres（HGMs）/epoxy syntactic foam was fabricated. The effects of ultrasonication on the density, compression strength, and water absorption properties were studied. Better dispersed MWCNTs can be obtained after ultrasonication treatment, but an increasing viscosity will lead to a larger amount of voids during syntactic foam preparation especially when the content of HGMs is more than 70 vol%. The existing voids will decrease the density of epoxy syntactic foam. However, the ultrasonication does not change the compression strength much. Ultrasonication treatment will decrease the water absorption content due to the better dispersion and hydrophobic properties of MWCNTs. But a significant increase of water absorption content occurs when HGMs is more than 70 vol%, which is attributed to the higher viscosity and larger amount of voids.

N/S codoping modification based on the metal organic frameworkderived carbon to improve the electrochemical performance of different energy storage devices

Carbon-based materials have become a research hotspot in the field of energy storage devices in recent years due to their abundant resources,low cost,and environmental friendliness.However,the low capacity and poor high rate performance still constitute great challenges.Metal organic framework-derived carbon has been widely researched because of its high porosity,tunable structure,and good conductivity.In this work,N/S codoped hierarchical porous carbon microspheres were prepared by a high-temperature heat treatment and atomic doping process using a zinc-based organic framework as the precursor.When used as a potassium-ion battery anode,it has a high reversible specific capacity(435.7 mAh g^(-1)),good rate performance(133.5 mAh g^(-1)at 10,000 m A g^(-1)),and long-term cycling stability(73.2%capacity retention after the 2500th cycle).The potassium storage mechanism of the derived carbon was explained by various electrochemical analysis methods and microstructure characterization techniques,and the relationship between the structural characteristics and electrochemical properties was researched.In a supercapacitor,the porous carbon material exhibits a specific capacitance of 307.2 F g^(-1)at a current density of 0.2 A g^(-1)in a KOH aqueous solution and achieves a retention rate of 99.88%after 10,000 cycles.The assembled symmetric supercapacitor device delivers a high energy density of 6.69 Wh kg^(-1),with a corresponding power density of 2500 W kg^(-1).In addition,density functional theory calculations further confirmed that N/S codoping can improve the adsorption capacities of potassium and hydroxyl ions in the derived carbon.

Construction of Highly Efficient Photocatalyst with Core-Shell Au@Ag/C@SiO_(2)Hybrid Structure towards Visible-Light-Driven Photocatalytic Reduction

Main observation and conclusion Herein,we report a rational construction of Au@Ag/C@SiO_(2)system with Au@Ag core-shell nanoparticles(NPs)as a promising photocatalyst based on the plasmonic coupling effect for the first time towards the photoreduction of nitroaromatic compounds under visible light.The combination and elaborate construction of Au@Ag NPs,carbon microspheres and mesoporous SiO_(2)shell can endow this system with several outstanding features towards photocatalytic reaction.Firstly,the broadband light harvesting across ultraviolet-visible-near infrared(UV-vis-NIR)region can be achieved due to the comprehensive effect of surface plasmonic resonance(SPR)coupling model of Au and Ag,near-field scattering light of carbon microspheres and light reflecting effect of SiO_(2)shell,resulting in the production of more electrons for phororeduction reaction.Secondly,the carbon microspheres in Au@Ag/C@SiO_(2)system possess electron-rich property due to their strong electron-withdrawing ability,which can act as the Lewis acid and Lewis basic site,and promote the stepwise hydrogenation of nitrobenzene.Thirdly,Au@Ag/C@SiO_(2)exhibits excellent reusability because of the protection of SiO_(2)shell,which restricts metal NPs inside the spheres and protects them from aggregation and being lost during reaction process.Our present work demonstrates the significance of construction of hybrid nanostructures based on the plasmonic coupling effect,which can be a promising approach to design efficient photocatalyst towards organic synthesis under visible light.