Biomass Homogeneity Reinforced Carbon Aerogels Derived Functional Phase-Change Materials for Solar–Thermal Energy Conversion and Storage

We deviseda functional form stable compositephase-change materials(PCMs)toachieve a three-dimensional(3D)interconnectedporous carbon aerogel structure for encapsulating polyethyleneglycol(PEG).Anovelhomogeneity reinforced carbonaerogel witha well-interconnected porous structure was constructed bycombining a flexible carbonresource from biomass guar gum with hard-brittle carbonfrom polyimide,to overcome severeshrinkage andpoor mechanical performance of traditionalcarbon aerogel.Thesupportingcarbon aerogel-encapsulated PEG produced thenovel composite PCMswithgood structure stability andcomprehensive energy storage performance.Theresults showed thatthecomposite PCMsdisplayed awell-defined 3Dinterconnected structure,and theirenergy storage capacities were 171.5 and169.5 J/g,which changed onlyslightlyafter 100 thermalcycles,andthe compositescould maintainthe equilibrium temperature at50.0−58.1℃ for about 760.3 s.The thermal conductivityofthe compositescould reach0.62 W m^(−1) K^(−1),which effectively enhanced the thermalresponse rate.And thecomposite PCMs exhibited good leakage-proof performance andexcellent light–thermal conversion.The compressive strengthof thecomposite PCMscan improveupto 1.602 MPa.Results indicatethatthisstrategy canbe efficiently usedtodevelop novel composite PCMswithimproved comprehensive thermalperformance and high light–thermal conversion.

Optimal Electrochemical Performances of CO_2 Activated Carbon Aerogels for Supercapacitors

Activated carbon aerogels（ACAs） derived from sol-gel polycondensation of resorcinol （R） and formaldehyde （F） were pyrolyzed under Ar flow and activated in CO2 atmosphere. The morphology of ACAs was characterized by scanning electron microscopy （SEM） and the structural properties were determined by N2 adsorption at 77 K. The results show that ACAs have a typical three-dimensional nanonetwork structure composing of cross-linking of carbon nanoparticles. The specific surface area and the total pore volume remarkably increase with increasing activation time while the previous porous structure still remains. The specific capacitance of the 950-10-ACA electrode can reach up to 212.3 F/g in 6 mol/L KOH electrolyte. The results of constant-current charge-discharge testing indicate that the ACAs electrodes present fast charge- discharge rate and long cycle life （about 98% capacitance retained after 3000 charge-discharge cycles at 1.25 mA/cm2）. Lower internal resistances can be achieved for 950-10-ACA electrode in KOH electrolyte. Our investigations are very important to improve the wettability and electrochemical performance of electrode for supercapacitors.

Optimized Synthesis of Carbon Aerogels via Ambient Pressure Drying Process as Electrode for Supercapacitors

Carbon aerogels were synthesized via ambient pressure drying process using resorcinolformaldehyde as precursor and P123 to strengthen their skeletons. CO2 activation technology was implemented to improve surface areas and adjust pore size distribution. The synthesis process was optimized, and the morphology, structure, adsorption properties and electrochemical behavior of different samples were characterized. The CO2-activated samples achieved a high specific capacitance of 129.2 F/g in 6 M KOH electrolytes at the current density of 1 m A/cm^2 within the voltage range of 0-0.8 V. The optimized activation temperature and duration were determined to be 950 ℃ and 4 h, respectively.

S-doped carbon aerogels/GO composites as oxygen reduction catalysts

Composites of carbon aerogel and graphite oxide（GO） were synthesized using a self-assembly method based on dispersive forces. Their surface was modified by treatment in hydrogen sulfide at 650 and800 ℃. The samples obtained were characterized by adsorption of nitrogen, TA-MS, XPS, potentiometric titration, and HRTEM and tested as catalysts for oxygen reduction reactions（ORR） in an alkaline medium.The synergistic effect of the composite（electrical conductivity, porosity and surface chemistry） leads to a good ORR catalytic activity. The onset potential for the composite of carbon aerogel heated at 800 ℃ is shifted to a more positive value and the number of electron transfer was 2e-at the potential 0.68 V versus RHE and it increased to 4e-with an increase in the negative values of the potential. An excellent tolerance to methanol crossover was also recorded.

Heteroatom tuning in agarose derived carbon aerogel for enhanced potassium ion multiple energy storage

The incorporation of heteroatoms into carbon aerogels(CAs)can lead to structural distortions and changes in active sites due to their smaller size and electronegativity compared to pure carbon.However,the evolution of the electronic structure from single-atom doping to heteroatom codoping in CAs has not yet been thoroughly investigated,and the impact of codoping on potassium ion(K+)storage and diffusion pathways as electrode material remains unclear.In this study,experimental and theoretical simulations were conducted to demonstrate that heteroatom codoping,composed of multiple heteroatoms(O/N/B)with different properties,has the potential to improve the electrical properties and stability of CAs compared to single-atom doping.Electronic states near the Fermi level have revealed that doping with O/N/B generates a greater number of active centers on adjacent carbon atoms than doping with O and O/N atoms.As a result of synergy with enhanced wetting ability(contact angle of 9.26°)derived from amino groups and hierarchical porous structure,ON-CA has the most optimized adsorption capacity(−1.62 eV)and diffusion barrier(0.12 eV)of K^(+).The optimal pathway of K^(+)in ON-CA is along the carbon ring with N or O doping.As K^(+)storage material for supercapacitors and ion batteries,it shows an outstanding specific capacity and capacitance,electrochemical stability,and rate performance.Especially,the assembled symmetrical K^(+)supercapacitor demonstrates an energy density of 51.8 Wh kg^(−1),an ultrahigh power density of 443Wkg^(−1),and outstanding cycling stability(maintaining 83.3%after 10,000 cycles in 1M KPF6 organic electrolyte).This research provides valuable insights into the design of highperformance potassium ion storage materials.

Cuprous oxide/copper oxide interpenetrated into ordered mesoporous cellulose-based carbon aerogels for efficient photocatalytic degradation of methylene blue

The casual discharge of dyes from industrial settings has seriously polluted global water systems.Owing to the abundance of biomass resources,preparing photocatalysts for photocatalytic degradation of dyes is significant;however,it still remains challenging.In this work,a cuprous oxide/copper oxide composite was interpenetrated onto carbon nanosheets of cellulose-based flexible carbon aerogels(Cu_(2)O/CuO@CAx)via a simple freeze-drying-calcination method.The introduction of the carbon aerogel effectively prevents the aggregation of the cuprous oxide/copper oxide composite.In addition,Cu_(2)O/CuO@CA0.2 has a larger specific surface area,stronger charge transfer capacity,and lower recombination rate of photogenerated carriers than copper oxide.Moreover,Cu_(2)O/CuO@CA0.2 exhibited high photocatalytic activity in decomposing methylene blue,with a degradation rate reaching up to 99.09% in 60 min.The active oxidation species in the photocatalytic degradation process were systematically investigated by electron spin resonance characterization and poisoning experiments,among which singlet oxygen played a major role.In conclusion,this work provides an effective method for preparing photocatalysts using biomass resources in combination with different metal oxides.It also promotes the development of photocatalytic degradation of dyes.

Self-assembled dandelion-like NiS nanowires on biomass-based carbon aerogels as electrode material for hybrid supercapacitors

Carbon aerogels derived from biomass have low specific capacity due to the underutilized structure,limiting their application in high-performance supercapacitors.In this work,the hierarchical nickel sulfide/carbon aerogels from liquefied wood(LWCA-NiS)were synthesized via a simple two-step hydrothermal method.Benefitting from the unique 3D coral-like network structure of LWCA,selfassembled NiS nanowires with the dandelion-like structure showed high specific surface(389.1 m^(2)·g^(−1))and hierarchical pore structure,which increased affluent exposure of numerous active sites and structural stability,causing superior energy storage performance.As expected,LWCA-NiS displayed high specific capacity(131.5 mAh·g^(−1) at 1 A·g^(−1)),good rate performance,and highly reversible and excellent cycle stability(13.1%capacity fading after 5000 cycles)in the electrochemical test.Furthermore,a symmetrical supercapacitor using LWCA-NiS-10 as the electrode material delivered an energy density of 12.7 Wh·kg^(−1) at 299.85 W·kg^(−1).Therefore,the synthesized LWCA-NiS composite was an economical and sustainable candidate for the electrodes of highperformance supercapacitors.

Synthesis of monolithic carbon aerogels with high mechanical strength via ambient pressure drying without solvent exchange

A simple,fast and cost-effective method for monolithic carbon aerogels(CAs) preparation was proposed through sol-gel polycondensation of resorcinol with fo rmaldehyde in a basic aqueous solution followed by ambient pressure drying without solvent exchange,and carbonization.The microstructure and network strength of CAs were tailored by adju sting the catalyst concentration([resorcinol]/[sodium carbonate] in the range of 300-2000),water content([deionized water]/[resorcinol] equals to 17 and 24,respectively),and gelation temperature(Tgel in the range of 30-90℃).Resultantly,the CAs with a wide range of density(0.30-1.13 g/cm3),high specific surface area(465-616 m2/g),high compressive strength(6.5-147.4 MPa)and low thermal conductivity(0.065-0.120 W·m-1 K-1) were obtained in this work.Moreover,the largesized CAs(100×100×20 mm3) can also be prepared by this method since the formed robust skeleton network can resist shrinkage/collapse of pore structure and prevent cracking during drying.The improved mechanical strength and monolithic forming abilities could be mainly attributed to the uniform arrangement of carbon particles and pores,fine particle size,abundant network structure and enhanced particle neck.

N-doped interconnected carbon aerogels as an efficient SeS2 host for long life Na-SeS2 batteries

Selenium sulfide(SeS2)cathodes have attracted much concern as an optimized choice comparing to sulfur and selenium for lithium and sodium storage.However,it also suffers from poor cycling stability due to the dissolution of reaction intermediate products.In this study,N-doped Interconnected carbon aerogels was applied as an efficient SeS2 host by infiltrating selenium sulfide into its microporous structure(denoted as SeS2@NCAs),which could effectively accommodate the volume change of SeS2 during cycling and alleviate the dissolution of reaction intermediate products.Therefore,as for Na storage,the SeS2@NCAs cathode delivers a superior long-term cycling performance of 536 mA·h·g^-1 at a current density of 0.5 A·g^-1 after 1,000 cycles with only 0.04%capacity decline per cycle and a high rate performance(524 mA·h·g^-1 at 2 A·g^-1 and 745 mA·h·g^-1 at 0.1 A·g^-1 retained),indicating the remarkable cycling stability of SeS2@NCAs cathodes.

Carbon aerogels prepared by autocondensation of flavonoid tannin

The first carbon aerogels prepared by autocondensation of condensed(flavonoid)tannin,a cheap renewable resource extracted from Mimosa barks,are presented.Mixing aqueous solutions of tannin and sodium silicate indeed produced the very fast gelation of tannins,thus leading to organic hydrogels which were first converted into organic aerogels by supercritical drying,and then into carbon aerogels after pyrolysis at 900℃.Subsequent dissolution of the silica nanoparticles thus formed within the carbon structure further increased significantly the porosity of the materials.Silica thus appeared to be both the gelation catalyst and a pore-directing agent.In this work,the influence on the porosity of the silica/tannin ratio and of the nature of the etching agent used for removing the silica was thoroughly investigated by combining several techniques.The conditions for producing either the most porous materials or those with the highest surface areas were identified and discussed.

High Performance Supercapacitors from Hierarchical Porous Carbon Aerogels Based on Sliced Bread

Supercapacitor electrodes with porous structure based on renewable,eco-friendly and cost-effective materials have caused extensive concern in energy storage fields.Sliced bread,the common food ingredient,mainly containing glucose polymers,can be a promising candidate to fabricate porous supercapacitor electrodes.Highly porous carbon aerogels by using sliced bread as the raw material were synthesized through a carefully controlled aerogel carbonization-activation process.Interestingly,the specific surface area and the pore size distribution of the porous carbon were controlled by the activation temperature,which result in the varied performance of the carbon aerogel as a supercapacitor.Electrochemical investigation measurements revealed that the hierarchical porous carbon aerogel shows an excellent capacitor behavior for construction of a symmetric supercapacitor,which demonstrated a high specific capacitance of 229 F·g-1 at discharge current of 0.2 A·g-1.In addition,the fabricated supercapacitor displayed excellent capacitance retention of 95.5% over 5000 cycles.

High-performance organic electrolyte supercapacitors based on intrinsically powdery carbon aerogels

A novel class of powdery carbon aerogels（PCAs） has been developed by the union of microemulsion polymerization and hypercrosslinking, followed by carbonization. The resulting aerogels are in a microscale powdery form, demonstrate a well-defined 3D interconnected nanonetwork with hierarchical pores derived from numerous interstitial nanopores and intraparticle micropores, and exhibit high surface area（up to 1969 m^2/g）. Benefiting from these structural features, PCAs show impressive capacitive performances when utilized as electrodes for organic electrolyte supercapacitors,including large capacitances of up to 152 F/g, high energy densities of 37-15 Wh/kg at power densities of 34–6750 W/kg, and robust cycling stability.

Cellulose nanofiber-derived carbon aerogel for advanced room-temperature sodium–sulfur batteries

Room-temperature sodium–sulfur(RT/Na–S)batteries are regarded as promising large-scale stationary energy storage systems owing to their high energy density and low cost as well as the earth-abundant reserves of sodium and sulfur.However,the diffusion of polysulfides and sluggish kinetics of conversion reactions are still major challenges for their application.Herein,we developed a powerful and functional separator to inhibit the shuttle effect by coating a lightweight three-dimensional cellulose nanofiber-derived carbon aerogel on a glass fiber separator(denoted NSCA@GF).The hierarchical porous structures,favorable electronic conductivity,and three-dimensional interconnected network of N,S-codoped carbon aerogel endow a multifunctional separator with strong polysulfide anchoring capability and fast reaction kinetics of polysulfide conversion,which can act as the barrier layer and an expanded current collector to increase sulfur utilization.Moreover,the hetero-doped N/S sites are believed to strengthen polysulfide anchoring capability via chemisorption and accelerate the redox kinetics of polysulfide conversion,which is confirmed from experimental and theoretical results.As a result,the assembled Na–S coin cells with the NSCA@GF separator showed a high reversible capacity(788.8 mAh g^(−1) at 0.1 C after 100 cycles)and superior cycling stability(only 0.059%capacity decay per cycle over 1000 cycles at 1 C),thereby demonstrating the significant potential for application in high-performance RT/Na–S batteries.

Amperometric Ascorbic Acid Sensor Based on Disposable Facial Tissues Derived Carbon Aerogels

In this study,the disposable facial tissues derived carbon aerogels(DFTs-CAs)were synthesized using disposable facial tissues as the raw material for fabricating a sensitive amperometric ascorbic acid(AA)sensor.The experimental results indicated that compared to glassy carbon electrode(GCE)and the popular carbon nanotubes modified GCE(CNTs/GCE),DFTs-CAs modified GCE(DFTs-CAs/GCE)exhibited better electrocatalytic activity(i.e.,lower peak potential and higher peak current)for AA electrooxidation and higher analytical performance for AA determination(i.e.,wider linear range,higher sensitivity and lower detection limit),which could be most likely due to the high density of defective sites and large specific surface area of DFTs-CAs.Especially,the DFTs-CAs/GCE was used for evaluating the AA level in real samples(i.e.,medical injection dose,vitamin C tablets,fresh orange juice and human urine)and the results are satisfactory.

Activated nitrogen-enriched carbon/carbon aerogel nanocomposites for supercapacitor applications

Activated nitrogen-enriched carbon/carbon aerogel nanocomposites (ANC/ACA) were prepared by synthesis of melamine resin/carbon aerogel composites, carbonization and KOH activation. Novel asymmetric supercapacitors consisting of Ni(OH)2/Co(OH)2 as anode and ANC/ACA with different composite ratios as cathode were assembled. The influence of composite ratio on electrochemical performances of materials was detected by cycle voltammetry (CV) and galvanostatic charge/discharge methods. The results of XPS and SEM show that N atoms exist in the ANC/ACA and ANC/ACA shows nanometer and honeycomb structure with more pores. When the composite ratio of ANC/ACA is 12-1, the ANC/ACA shows the highest Cp1 (312.8 F/g) vs 103.4 F/g of ACA and 230.1 F/g of ANC. And the optimal asymmetric supercapacitor with the ANC/ACA as cathode also shows the best electrochemical performances. The optimal supercapacitor is stable over 100 cycles. When the current density is 50 mA/cm2, the Cp2, Ep and P of the optimal supercapacitor are still 57.3 F/g, 9.0 W·h/g and 1 302.1W/kg, respectively.

Lightweight,Flexible Cellulose-Derived Carbon Aerogel@Reduced Graphene Oxide/PDMS Composites with Outstanding EMI Shielding Performances and Excellent Thermal Conductivities

In order to ensure the operational reliability and infor-mation security of sophisticated electronic components and to protect human health,efficient electromagnetic interference(EMI)shielding materials are required to attenuate electromagnetic wave energy.In this work,the cellulose solution is obtained by dissolving cotton through hydrogen bond driving self-assembly using sodium hydroxide(NaOH)/urea solution,and cellulose aerogels(CA)are prepared by gelation and freeze-drying.Then,the cellulose carbon aerogel@reduced graphene oxide aerogels(CCA@rGO)are prepared by vacuum impregnation,freeze-drying followed by thermal annealing,and finally,the CCA@rGO/polydimethylsiloxane(PDMS)EMI shielding composites are prepared by backfilling with PDMS.Owing to skin-core structure of CCA@rGO,the complete three-dimensional(3D)double-layer con-ductive network can be successfully constructed.When the loading of CCA@rGO is 3.05 wt%,CCA@rGO/PDMS EMI shielding composites have an excellent EMI shielding effectiveness(EMI SE)of 51 dB,which is 3.9 times higher than that of the co-blended CCA/rGO/PDMS EMI shielding composites(13 dB)with the same loading of fillers.At this time,the CCA@rGO/PDMS EMI shielding composites have excellent thermal stability(T_(HRI) of 178.3℃)and good thermal conductivity coefficient(λ of 0.65 W m^(-1) K^(-1)).Excellent comprehensive performance makes CCA@rGO/PDMS EMI shielding composites great prospect for applications in lightweight,flexible EMI shielding composites.

Environmentally Friendly and Multifunctional Shaddock Peel-Based Carbon Aerogel for Thermal-Insulation and Microwave Absorption

Eco-friendly electromagnetic wave absorbing materials with excellent thermal infrared stealth property,heat-insulating ability and compression resistance are highly attractive in practical applications.Meeting the aforesaid requirements simultaneously is a formidable challenge.Herein,ultra-light carbon aerogels were fabricated via fresh shaddock peel by facile freeze-drying method and calcination process,forming porous network architecture.With the heating platform temperature of 70℃,the upper surface temperatures of the as-prepared carbon aerogel present a slow upward trend.The color of the sample surface in thermal infrared images is similar to that of the surroundings.With the maximum compressive stress of 2.435 kPa,the carbon aerogels can provide favorable endurance.The shaddock peel-based carbon aerogels possess the minimum reflection loss value(RLmin)of−29.50 dB in X band.Meanwhile,the effective absorption bandwidth covers 5.80 GHz at a relatively thin thickness of only 1.7 mm.With the detection theta of 0°,the maximum radar cross-sectional(RCS)reduction values of 16.28 dB m^(2) can be achieved.Theoretical simulations of RCS have aroused extensive interest owing to their ingenious design and time-saving feature.This work paves the way for preparing multi-functional microwave absorbers derived from biomass raw materials under the guidance of RCS simulations.

Biomass Carbon Aerogel Modified by N235 and KH560 for Removal of Iodide from Oilfield Brine

Owing to porous structure,stable chemical properties,low cost and available raw material,biomass carbon aerogel is a promising adsorbent framework material.Herein,a pomelo peel-based carbon aerogel was prepared by hydrothermal-freeze drying-high temperature carbonization method and modified with Tri-n-ocylamine(N235)and γ-Glycidyloxypropyltrimethoxysilane(KH560)via impregnation process.The as-prepared adsorbents exhibit superior adsorption performance for iodide in simulated and oilfield brines,and the highest adsorption amount of iodide in oilfield brine can reach 0.58 mmol/g.It is also demonstrated by adsorption kinetics and isotherms that iodide is adsorbed through chemical adsorption.Protonation of tertiary amide group in N235 and epoxy group in KH560 may be the main reason for the highly selective adsorption of iodide.

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.

Defect reduction to enhance the mechanical strength of nanocellulose carbon aerogel

Carbon aerogels prepared from renewable nano building blocks are rising-star materials and hold great promise in many fields.However,various defects formed during carbonization at high temperature disfavor the stress transfer and thus the fabrication of flexible carbon aerogel from renewable nano building blocks.Herein,a structural defect-reducing strategy is proposed by altering the pyrolysis route of cellulose nanofiber.Inorganic salt that inhibits the generation of tar volatilization during pyrolysis can prevent the formation of various structural defects.Microstructure with fewer defects can reduce stress concentration and remarkably enhance the compressibility of carbon aerogel,thus increasing the maximum stress retention of carbon aerogel.The carbon aerogel also has high stress sensor sensitivity and excellent temperature coefficient of resistance.The structural defect-reducing strategy will pave a new way to fabricate high-strength carbon materials for various fields.