Search

To explore the natural resources as sustainable precursors offers a family of green materials. The use of bio-waste precursors especially the remaining from food processing is a scalable, highly abundant, and cost-effective strategy. Exploring waste materials is highly important especially for new materials discovery in emerging energy storage technologies such as lithium sulfur batteries (LSBs). Herein, waste milk powder is carbonized and constructed as the sulfur host with the hollow micro-/mesoporous framework, and the resulting carbonized milk powder and sulfur (CMP/S) composites are employed as cathodes for LSBs. It is revealed that the hollow micro-/mesoporous CMP/S framework can not only accommodate the volume expansion but also endow smooth pathways for the fast diffusion of electrons and Li-ions, leading to both high capacity and long cycling stability. The CMP/S composite electrode with 56 wt.% loaded sulfur exhibits a remarkable initial capacity of 1596 mAh g−1 at 0.1 C, corresponding to 95% of the theoretical capacity. Even at a rate of 1 C, it maintains a high capacity of 730 mAh g−1 with a capacity retention of 72.6% after 500 cycles, demonstrating a very low capacity fading of only 0.05% per cycle. Importantly, the Coulombic efficiency is always higher than 96% during all the cycles. The only used source material is expired waste milk powders in our proposal. We believe that this “trash to treasure” approach will open up a new way for the utilization of waste material as environmentally safe and high performance electrodes for advanced LSBs.

Reasonable construction of sulfur host with high conductivity, large sulfur storage gap, strong chemical adsorption, and fast oxidation-reduction kinetics of polysulfide is very significant for its practical use in lithium-sulfur batteries (LSBs). In this paper, the surface modification of MIL-88A(Fe) is carried out by Dawson-type polyoxometalate (POM), and a hollow capsule shell material with P2W18, Fe3O4, and C components is synthesized by the subsequent carbonization process. When applied as the sulfur host, the hollow capsule shell material can efficiently improve the conductivity of sulfur electrode and restrain the volumetric change of active sulfur while charging and discharging. On this foundation, electrochemical analysis and density functional theory (DFT) calculation show that the P2W18 on the outer layer of the capsule shell have effective electrocatalytic activity and potent chemical bond on the lithium polysulfides (LiPSs), which is helpful to block the shuttle effect. Therefore, the as-assembled LSBs display the outstanding specific capacity and prominent cycle stability. Specifically, it delivers an excellent reversible capacity of 1063 mAh/g after 100 cycles of charge–discharge at a rate of 0.5 C, accounting for a preservation by 96% in comparison to that of the initial cycle. Moreover, even after 2000 cycles at 1 C, the reversible specific capacity of 585 mAh/g can still be maintained with an average decay rate of only 0.021%.

In this study, porous carbon has been prepared through potassium hydroxide (KOH) activation of coconut fiber (CF) and subsequent carbonization in the presence of an inert gas. The activated carbons (AC) were prepared via carbonization of the precursor at different temperatures. Subsequently, their electromagnetic wave absorption (EMWA) performance was investigated at X-band frequency. The phase crystallinity, porous features, and degree of graphitization of the activated carbons were studied using XRD, nitrogen adsorption/desorption isotherm, and Raman spectroscopy, respectively. Using the BET method, the activated carbon prepared at 750 °C displayed a high specific surface area of 602.9 m2 g−1 and an average pore size of 6 nm, which confirms the extant of mesopores. The EMWA was studied using COMSOL Multiphysics software based on the finite element method. Results show that the activated carbon prepared at 750 °C attained an optimal reflection loss of −45.6 dB at 10.96 GHz with a corresponding effective bandwidth of 3.5 GHz at a thickness of 3.0 mm. In conclusion, this study interestingly shows that porous carbon obtained from coconut fiber has great potential for attenuating electromagnetic waves.

As an aromatic polymer in nature, lignin has recently attracted gross attention because of its advantages of high carbon content, low cost and bio-renewability. However, most lignin is directly burnt for power generation to satisfy the energy demand of the pulp mills. As a result, only a handful of isolated lignin is used as a raw material. Thus, increasing value addition on lignin to expand its scope of applications is currently a challenge demanding immediate attention. Many efforts have been made in the valorization of lignin, including the preparation of precursors for carbon fibers. However, its complex structure and diversity significantly restrict the spinnability of lignin. In this review, we provide elaborate knowledge on the preparation of lignin-based carbon fibers ranging from the relationships among chemical structures, formation conditions and properties of fibers, to their potential applications. Specifically, control procedures for different spinning methods of lignin, including melt spinning, solution spinning and electrospinning, together with stabilization and carbonization are deeply discussed to provide an overall understanding towards the formation of lignin-based carbon fibers. We also offer perspectives on the challenges and new directions for future development of lignin-based carbon fibers.

Core-shell structured Ni-ZIF-67@ZIF-8 derived bimetal selenides encapsulating into a 3D interpenetrating dual-carbon framework (Ni3Se4@CoSe2@C/CNTs) have been designed and prepared via carbonization and subsequent selenization processes. In this hierarchical structure, Ni3Se4@CoSe2 nanocrystals were uniformly dispersed into the 3D carbon framework structure/carbon nanotubes networks, which greatly enhanced the electronic conductivity and further enabled ultrafast Na-ion diffusion kinetics. When used as anode materials of sodium ion battery (SIB), The Ni3Se4@CoSe2@C/CNTs electrode delivered the excellent rate capability of 206 mA h g-1 at 3 A g-1 and marvelous cyclic stability with capacity retention of 243 mA h g-1 after 600 cycles at 1 A g-1. This research provides a new way to prepare bimetallic selenide derived from MOF precursor with amazing heterostructure as the advanced anode materials for SIBs.

The photocatalytic performance of the semiconductor CdS can be improved with carbon materials capable of limiting photocorrosion and the fast recombination of photogenerated charges. For this purpose, carbon derived from biomass exhibit several advantages including low cost, high abundance, and renewability. Here, photocatalytic CdS nanorods modified with carbon derived from the leaves of Japanese raisin trees were synthesized via a single hydrothermal step. Composite CdS nanorods with 5% biomass-derived carbon photocatalyzed H2 evolution 1.8 times faster than unmodified CdS at a rate of 5.71 mmol g−1 h−1. The apparent quantum efficiency of 5%C/CdS nanorods was 14.96%. Furthermore, the addition of biomass-derived carbon to CdS nanorods augmented the stability of the semiconductor under visible light. The characterization of the composite PC indicated that a larger specific surface area, as well as upgraded charge separation caused by biomass-derived carbon, were involved in the acceleration of photocatalytic hydrogen production.

To meet the increasing energy demand, the research and development of efficient and clean fuel cells and metal-air batteries are of great significance. Under these circumstances, these hierarchically porous carbon nanomaterials obtained by pyrolysis of coordination polymers are regarded as excellent oxygen reduction catalysts and are expected to be used as air cathode materials. Herein, a type of 2-dimensional structure of InOF-26 has been thermally converted into ultrathin graphitized nitrogen-doped carbon nanosheets, denoted as NG-CNS. During the carbonization, the addition of ferric chloride assists in breaking the intermolecular forces between crystal structures, which is further conducive to the formation of carbon nanosheets with an improved graphitization degree. Meanwhile, the subsequent ammonia impregnation together with secondary calcination can readjust the coordination environment of nitrogen species in the carbonaceous matrix. The obtained product of NG-CNS exhibits excellent ORR performance with a high half-wave potential of 0.80 V, a large diffusion-limited current density of 6.00 mA cm−2, a small Tafel slope of 57.3 mV dec−1, to show unexpected practicability in Zn-air battery and Al-air battery. The relatively simple synthetic procedure, low cost, high repeatability, and satisfactory electrochemical performance of NG-CNS will provide a direction for the facile preparation of coordination polymer-derived carbon nanomaterials in energy storage and conversion applications.

Carbon aerogels with nanoporous structure are attractive for thermal insulation under extreme conditions, but their practical applications are usually plagued by the inherent brittleness and easy-oxidation characteristic at high temperature. Herein, silica-modified carbon aerogels (SCAs) with extraordinarily high strength are prepared via a facile sol-gel polymerization of phenolic resin and siloxane, followed by ambient pressure drying and carbonization. The resulting SCAs possess medium-high density of ∼ 0.5 g·cm-3 and mesoporous structure with the mean pore size of 33 nm. During carbonization process, the siloxane could be gradually transformed into the amorphous SiO2 particles and crystalline SiC particles, which are coated on the surface of carbon nanoparticle and consequently improve the oxidation-resistance of carbon aerogels. Due to the density-porosity trade-off, the SCAs have high compressive strength of 10.0 MPa and satisfied thermal conductivities of 0.118 W·m-1·K-1 at 25 °C and 0.263 W·m-1·K-1 at 1000 °C. Furthermore, needled carbon fiber-reinforced SCAs (CF-SCAs) with ultrahigh compressive strength of 210.5 MPa are prepared, which exhibit good thermal conductivities of 0.207 W·m-1·K-1 at 25 °C and 0.407 W·m-1·K-1 at 1000 °C. The ultrahigh mechanical strength, good oxidation-resistance, good thermal insulation as well as the facile preparation make the SACs great promising in high-temperature insulations especially under harsh conditions.

Silicon-based anode materials with high theoretical capacity have great challenges of enormous volume expansion and poor electronic conductivity. Herein, a novel dual carbon confined SiOx/C@void@Si/C yolk-shell monodisperse nanosphere with void space have been fabricated through hydrothermal reaction, carbonization, and in-situ low-temperature aluminothermic reduction. Furthermore, the O/Si ratio and void space between SiOx/C core and Si/C shell can be effectively tuned by the length of aluminothermic reduction time. The SiOx/C core plays a role of maintaining the spherical structure and the void space can accommodate the volume expansion of Si. Moreover, the inner and outer carbons not only alleviate volume variation of SiOx and Si but also enhance the electrical conductivity of composites. Benefiting from the synergy of the double carbon and void space, the optimized VSC-14 anode affords prominent cycle stability with reversible capacity of 1094 mAh g-1 after 550 cycles at 200 mA g-1. By pre-lithiation treatment, the VSC-14 achieves an initial Coulombic efficiency of 93.27% at 200 mA g-1 and a reversible capacity of 348 mAh g-1 at 5 A g-1 after 4000 cycles. Furthermore, the pouch cell using VSC-14 anode and LiFePO4 cathode delivers a reversible capacity of 138 mAh g-1 at 0.2 C. We hope this strategy can provide a scientific method to synthesis yolk-shell Si-based materials.

Designing intertwined porous structure is highly desirable to improve the electrochemical performance of carbon materials for supercapacitor. In this contribution, three-dimensional (3D) carbonized polyimide/cellulose (CPC) composite is fabricated via a facile “one-step” carbonization, in which cellulose as cross-linked agent is capable of modulating the molecular structure of polyamic acid, thus ensuring the formation of intertwined porous networks in the obtained carbon skeleton. Benefitting from the high specific surface area (951 m2 g-1) and uniformly distributed pores, the optimized CPC-5 electrode exhibits an outstanding specific capacitance of 300 F g-1 in 6.0 M KOH electrolyte. More impressively, the CPC-5 based symmetrical supercapacitor affords a high energy density of 22.6 Wh kg-1 at power density of 800 W kg-1, as well as an exceptional capacitance retention of 91.4% after 10000 cycles. This work affords an effective strategy to yield a promising polyimide derived carbon material for high-performance supercapacitors.

Heteroatom-doped carbon materials have demonstrated great potential in the electrochemical reduction reaction of CO2 (CO2RR) due to their versatile structure and function. However, rational structure control remains one challenge. In this work, we reported a unique carbon precursor of soft template-containing porous poly(ionic liquid) (PIL) that was directly synthesized via free-radical self-polymerization of ionic liquid monomer in a soft template route. Variation of the carbonization temperature in a direct pyrolysis process without any additive yielded a series of carbon materials with facile adjustable textural properties and N species. Significantly, the integration of soft-template in the PIL precursor led to the formation of hierarchical porous carbon material with a higher surface area and larger pore size than that from the template-free precursor. In CO2RR to CO, the champion catalyst gave a Faraday efficiency of 83.0% and a current density of 1.79 mA cm−2 at −0.9 V vs. reversible hydrogen electrode (vs. RHE). The abundant graphite N species and hierarchical pore structure, especially the unique hierarchical small-/ultra-micropores were revealed to enable better CO2RR performance.

A novel carbonized phenolic formaldehyde resin (PF) resin-coated Ni foam was used as an interlayer for brazing carbon fiber reinforced carbon composites (C/C) and Nb using a Ti–Ni filler. At first, uniformly distributed carbonaceous laminae with different mass fractions on the Ni foam surface were acquired after the carbonization process by controlling the concentration of the PF solution. Afterwards, the obtained carbonaceous laminae covered Ni foam composite (C-Nif) was applied as an interlayer for brazing C/C and Nb via an assembly of C/C/Ti foil/Ni foil/C-Nif interlayer/Ti foil/Nb. The morphologies and microstructures of the carbonization product and the interfacial microstructures of the joints were investigated. The brazing mechanism has been elaborated in detail. With the help of the interconnected porous structure of the Ni foam, the distribution of the in-situ formed (Ti,Nb)2Ni particles, (Ti,Nb)C ring reinforcements as well as the Nb solid solution were uniformly obtained throughout the brazing seam. As a result, the joint residual stress was effectively released and consequently, the joint shear strength at elevated temperature (1000 °C) reached up to 33 MPa, which is 4.5 times higher than the directly brazed joint without an interlayer.

Nowadays, developing microwave absorption materials (MAMs) with thin thickness, wide-frequency effective absorption bandwidth (EAB) and strong absorbing capacity is an urgent requirement to tackle the increasingly serious electromagnetic radiation issue. Herein, we report a novel high-performance MAMs by growing Fe3O4 nanoparticles on activated porous carbon derived from egg white via a facile carbonization and subsequent hydrothermal approach. The resultant composite features three-dimensional hierarchical porous carbon embedded with Fe3O4 nanoparticles. Benefiting from the balanced impedance matching and the multi-loss that involve the conductive loss, dielectric loss, dipolar/interfacial polarization and magnetic loss, the prepared composite achieves a minimum reflection loss (RL) of -43.7 dB at 9.92 GHz and a broad EAB (RL

It is a significant challenge to combine a large pseudocapacitive material with conductive honeycomb-like carbon frameworks for long-term stable supercapacitors. Herein, hierarchical composite materials are manufactured by using biomass carbon, ZIF-67, and a mild pore former (Ni(CH3COO)2) to generate alloy-type CoNi3 nanoparticles planted into conductive honeycomb-like carbon frameworks (C@ZIF-67-T). Meanwhile, the effect of carbonization temperature on the honeycomb-like pore size and the structure of composite materials is systematically investigated. As the honeycomb-like carbon skeleton structure guarantees good ionic and electronic conductivities and a large contact area, whereas the alloy nanoparticles provide a rich redox reaction for Faradaic capacitance. Therefore, the as-obtained C@ZIF-67–600 electrode presents a remarkable specific capacitance of 1044.8 F · g−1 at 1.0 A · g−1 and an ultra-long cycling stability with 30,000 cycles at 5.0 A · g−1 in a three-electrode system. In addition, the assembled C@ZIF-67–600//activated carbon asymmetrical supercapacitor exhibit a high specific capacitance of 274.4F · g−1 at 1.0 A · g−1 and a long-term stable lifespan with a capacitance retention of 87% after 20,000 cycles at 5.0 A · g−1. Besides, the asymmetrical supercapacitor also presents a maximum energy density of 85.13 Wh · kg−1 at a power density of 750 W · kg−1. Such superior electrochemical performance demonstrate that the designed electrode material provides a promising energy storage application.

Catalytic methane decomposition (CMD) is a promising route for H2 production. In this paper, MOF-derived hierarchical carbon catalysts were prepared by the carbonization of ZIF-8 with additional carbon source and used for CMD. The effects of carbonization temperature, reaction temperature, and the kinds of additional carbon sources on the structure of derived carbon materials and their catalytic performances were studied. The results showed that the morphology and textural properties can be improved by varying the carbonization temperature and additional carbon source. The specific surface area of the ZIF-derived carbon can be significantly increased, and the hierarchical pore structure with improved pore size distribution can be obtained, which leads to good performances for CMD. Catalytic performance can be obviously enhanced by increasing the reaction temperature. The C950-FA prepared by carbonization of ZIF-8 with furfuryl alcohol as additional carbon source exhibits the highest initial conversion of methane (64%) and good stability at 890 °C. About 11% methane conversion was kept after 2750 min. This study provides a new route for the preparation of carbon material catalysts to achieve high-efficient conversion of methane.

Zeolitic imidazolate framework-67 (ZIF67) derivatives are considered as promising active materials for energy storage owing to the possible formation of cobalt oxide and N-doped graphite. Cobalt oxide has multiple redox states for generating redox reactions for charge storage, while N-doped graphite can provide high electrical conductivity for charge transfer. In this study, it is the first time to synthesize binder-free electrodes composed of cobalt oxide and N-doped graphite derived from ZIF67 on carbon cloth (CC) for supercapacitor (SC). Successive oxidation and carbonization along with additional coverage of ZIF67 derivatives are applied to synthesize ZIF67 derivatives composed of cobalt oxide, N-doped graphite and cobalt oxide/N-doped graphite composites with different layer compositions. The highest specific capacitance (CF) of 90.0F/g at 20 mV/s is obtained for the oxidized ZIF67/carbonized ZIF67/carbon cloth (O67/C67/CC) electrode, due to the large surface area and high electrical conductivity benefitted from preferable morphology and growing sequence of Co3O4 and N-doped graphite. The symmetric SC composed of O67/C67/CC electrodes shows the maximum energy density of 2.53 Wh/kg at the power density of 50 W/kg. Cycling stability with CF retention of 70% and Coulombic efficiency of 65% after 6000 times repeatedly charge/discharge process is also obtained for this symmetric SC.

Nowadays, alkali titanate (ATO) fibers are attracting attention because they can provide a reinforcing as well as a functional effect. In this study, ATO fibers were synthesized by a one-step calcination route without specialized equipment and flux using a resorcinol–formaldehyde (RF) resin. Homogeneous mixing of the RF resin dissolved in water, TiO2, and an alkali source led to a uniform dispersion, and the three-dimensional polymerized RF resin formed a closely structured matrix with TiO2 and the alkali source. By carbonizing the RF resins prepared using K or Na as the alkali source, titanate fibers with lengths greater than 1 mm were formed. Growth mechanisms and crystal structures of the titanate fibers synthesized with and without the RF resin were completely different. Effects of the RF resin on the crystal structure and morphology of the titanate fibers were systematically studied by changing the calcination temperature and molar ratio of TiO2 and alkali source (Li, Na, or K). We found that the RF resin played an essential role in producing a suitable reaction field for fiber growth and controlling the morphology of titanate fibers.

A toad egg-inspired structure comprising bismuth (Bi) nanoparticles (NPs) contained in a carbon microrod shell (Bi@C) was synthesized via the one-pot supercritical acetone (scAct) route and subsequent carbonization. During the formation of Bi NPs in scAct in the presence of nitric acid, a few decomposed acetone molecules acted as carbon sources, which generated an albumen-like N-doped carbon microrod with an average shell thickness of 38 nm and were embedded with yolk-like Bi NPs having size in the range of 30–200 nm. The densely packed Bi NPs inside the carbon micron shell resulted in a high Bi loading of 78 wt%. When utilized for Li storage, the Bi@C delivered a high reversible capacity of 337 mAh g–1 after 70 cycles at 0.05 A g–1, long-term cyclability of 0.04 decay per cycle for 1000 cycles at 1 A g–1, and high volumetric energy density of 870 mAh cm–3. The use of a mixed ether- and ester-based electrolyte in the Bi@C cell reduced the resistivity and increased the capacitive contribution, thereby resulting in a better high-rate performance and long-term stability than those obtained using conventional ester-based electrolytes.

Biomass-derived porous carbon has attracted tremendous attention in many research fields due to its cheap and feasible strategy. In this work, bark-derived Co-doped porous carbon composites (Co@PC) for microwave absorption (MA) applications were successfully prepared through a simple method. The minimum reflection loss (RLmin) of Co@PC (carbonized at 800 °C, Co2+ concentration is 0.15 molL-1) is −49.2 dB at 10 GHz and a wide effective absorption bandwidth (EAB) of 6.16 GHz was obtained. Further, by adjusting carbonization temperature of the bark, the MA performance could be further enhanced. The results show that the RLmin could be −58.4 dB at 8.6 GHz when the bark was carbonized at 900 °C. The retained channel structures of the bark played an important role in this excellent MA performance, which is not only cause multiple reflections and scattering of microwaves, but also benefit to the impedance matching. Cobalt-nanoparticles (Co-NPs) dispersed on the surface of the channel structures, endow a strong magnetic loss of microwave energies. In addition, radar cross section (RCS) simulation results also demonstrate that Co@PC can be applied in the field of microwave absorbing materials (MAMs).

A cost-effective electrocatalyst with high activity and stability was developed. The Fe-Nx and pyridinic-N active sites were embedded in nitrogen-doped mesoporous carbon nanomaterial by carbonization at high temperature. The electrocatalyst exhibited excellent electrochemical performance for the oxygen reduction reaction, with high onset potential and half-wave potential values (Eonset = 1.10 ​V and E1/2 ​= ​0.944 ​V) than 20 ​wt % Pt/C catalyst (1.04 and 0.910 ​V). The mass activity of the Schiff base network (SNW) based SNW-Fe/N/C@800° electrocatalyst (0.64 ​mA ​mg−1 @ 1 ​V) reached about half of the commercial Pt/C electrocatalyst (1.35 ​mA ​mg−1 @ 1 ​V). The electrocatalyst followed the 4-electron transfer mechanism due to very low hydrogen peroxide yield (H2O2 ​

FeS2-embedded in porous carbon (FeS2/C) was prepared by simultaneous sulfidation and carbonization of an iron-based metal-organic framework precursor, and subsequently immobilized in polyvinylidene fluoride membranes (FeS2/C@PVDF) for organics removal via peroxymonosulfate (PMS) activation. The composition, structure, and morphology of the FeS2/C@PVDF membrane were extensively characterized. Scanning electron microscopy images manifest that the FeS2/C nanoparticles with an average diameter of 40 nm are assembled on the external and internal membrane surface. The as-prepared FeS2/C@PVDF membrane exhibits excellent performances over a wide pH range of 1.53-9.50, exceeding carbon-free syn-FeS2@PVDF. The effective degradation could be improved by inner pyrite FeS2 cores and thus enhanced the electron transfer between carbon shell and PMS. Electron paramagnetic resonance and quenching experiments elucidated that radical ( HO ∙ , SO 4 ∙ - ) and nonradical (1O2) species were the predominant reactive oxidants. In addition, FeS2/C@PVDF exhibited high stability with low Fe leaching (0.377 mg/L) owing to the effective protection of the outer carbon skeleton. Plentiful porosity of PVDF membranes not only affords a controlled size and confined uniform distribution of the immobilized FeS2/C nanoparticles, but also enables a persistent exposure of active sites and enhanced mass transfer efficiency. Our findings demonstrate a promise for utilizing the novel FeS2/C@PVDF membrane as an efficient catalyst for the environmental cleanup.

Development of low-cost electrode materials with long cycle life and high volumetric capacity is important for large-scale applications of lithium-ion batteries (LIBs). Here, an electrode made from Fe2O3 encapsulated with N-doped carbon (Fe2O3@N-C) via ZIF-8 coating and carbonization process is reported. A cavity was generated between the Fe2O3 and N-C material during the carbonization process that is conducive to alleviating the volume expansion of Fe2O3. As a result, the Fe2O3@N-C composite exhibits a high specific capacity (1064 mAh/g at 0.1 A/g) and cycle stability (803.6 mAh/g at 1.0 A/g after 1100 cycles) when used as the LIB anode. In addition, the influence of carbonization under air on the LIB performance was investigated by controllably changing the crystal phase of Fe2O3 and the thickness of the carbon layer. This work provides a new method for the design and fabrication of yolk-shell composite electrodes for LIBs and other applications.

Efficient electrocatalytic reduction of CO2 to value-added chemicals and fuels is a promising technology for mitigating energy shortage and pollution issues yet highly relay on the development of high-performance electrocatalysts. Herein, we develop an effective strategy to fabricate carbonized wood membrane (CW) decorated with AuPd alloy nanoparticles with tunable composition (termed as AuPd@CW) as self-supported electrodes for efficient electrocatalytic CO2 reduction. The uniformly distributed AuPd nanoparticles on wood matrix are first achieved through the in-situ reduction of metal cations by the lignin content in wood. Subsequently, two-step carbonization was employed to promote the alloying of AuPd nanoparticles and the formation of CW. The AuPd@CW membrane electrode features an integrated macroscopic structure with numerous open and aligned channels for rapid electron transfer and mass diffusion and well-dispersed AuPd alloy nanoparticles as active sites for the CO2 reduction. The optimal Au95Pd5@CW electrode affords a high selectivity for CO2 electroreduction with a maximum CO faradaic efficiency (FECO) of 82% at an overpotential of 0.49 V, much higher than those obtained on Au@CW and Pd@CW electrodes. The CO current density and FECO remain relatively stable during a 12 h electrolysis reaction. In addition, density functional theory (DFT) calculations reveal that alloying Au with Pd enables a balance between the formation of intermediate COOH* and the desorption of CO on the surface of AuPd nanoparticles, thus enhancing the selectivity of CO production. This work offers an effective strategy for the fabrication of bimetallic alloys supported on wood-based carbon membrane as a practical electrode for electrochemical energy conversion.

Solar-driven interface water evaporation has shown great potential in seawater desalination. A solar steam generation device with excellent performance requires materials that can efficiently absorb solar energy to achieve photothermal conversion. ZIF-L (a Co-based metal–organic framework) after carbonization has the dual role of carbon nanoplates and cobalt nanoparticles to absorb solar light, exhibiting broad light absorption. Herein, based on carbonized ZIF-L and natural wood, we designed a solar-driven interface water evaporation device, in which ZIF-L after carbonization is used to achieve photothermal conversion, and wood aerogel with high porosity is used as a supporting layer to transport seawater to the evaporation interface and realize self-floating of the device. The prepared evaporator exhibited a high evaporation rate of 1.52 kg m−2 h−1 and an evaporation efficiency of 92.42% under 1 sun illumination, and neither salt accumulation nor a significant decrease in the evaporation rate of the device was observed after continuous operation for 10 evaporation cycles. Additionally, the excellent resistance to salt deposition and automatic salt discharge ability of the evaporator were demonstrated, which can ensure its long-term stable operation. The high-efficiency and stable evaporation performance demonstrate the evaporator's great potential in the practical application of solar energy production of clean water.

Zirconium carbide hollow microspheres (ZrC HMs) were fabricated via spray drying process and polymer-derived ceramics technique. The stable and homogeneous ZrC precursor solution can be prepared by mixing polyzirconoxane (PZO), phenolic resin (PR), curing agent p-toluenesulfonic acid (TsOH) and solvent n-propanol. The precursor solution was spray-dried to form hollow precursor microspheres. During the spray drying process, morphology of the hollow precursor microspheres can be regulated by adjusting temperature of inlet hot N2, concentration of precursor solution and the amount of curing agent TsOH. The prepared hollow precursor microspheres were carbonized at 700 °C and then converted into ZrC HMs by carbothermal reduction reaction above 1500 °C. During the pyrolysis process, nanosized ZrO2 grains produced by PZO decomposition are evenly dispersed, so is the carbon produced by PR pyrolysis, as prevents overgrowth of ZrO2 grains in the following process, even when it is changed to ZrC. ZrC HMs maintained excellent spherical morphology at temperatures of 1500–1900 °C, with particle size Dv(50)=16.4–18.7 μm, which enable their promising applications in ultra-high temperature insulation material. This preparation method is simple and can be prepared on a large scale.

C/C-BN-SiC composite was prepared by ceramic slurry infiltration combined with resin impregnation and carbonization, and the matrix with continuous distributed self-healing phase was obtained. In this study, the kinetic characteristics and oxidation behavior of the composites with various h-BN/SiC ratios in the temperature range of 600∼1300°C were studied by combining the isothermal oxidation test with the kinetic model. The optimal h-BN/SiC ratio balances the thermal stability and fluidity of the oxidized product, which not only has high thermal stability and low oxygen permeability to acts as an oxygen diffusion barrier but also has a certain fluidity to seal defects.

Heteroatom-doping had been demonstrated to effectively improve the capacitive energy storage of hard carbon in potassium ion batteries (KIBs). However, the external defects introduced during doping process are responsible to alter the microstructure of carbon host. But there is a scarcity of systematic in-depth understanding the comprehensive effects of defects and heteroatoms in hard carbon for K storage performance. Herein, a series of porous carbon microspheres in different defects level and S-doping amount (SPCS) were simply synthesized under different carbonization temperatures. It was found that various microstructural features of SPCS exhibited different trends with the change of carbonization temperature. Moreover, the depth of the K-ion insertion reaction, the additional oxidation-reduction reaction, and the adsorption process of K-ion on active sites can be enhanced by regulating the S-doping amount and defect level. Specially, the best SPCS can obtain a prominent reversible charging capacity of 435.1 mA h g−1 at 50 mA g−1 over 100 cycles. In addition, in-situ XRD characterization reveals that its lattice structure undergoes a disordered transformation without expansion of interlayer spacing during the K-ions insertion process. This work demonstrates that rational regulation of doping engineering is of great significance for obtaining high-performance carbon anodes for KIBs.

Hard carbon (HC) is a promising anode material for K+-storage due to its randomly oriented turbostratic structure. However, most reported HC anodes exhibit low initial Coulombic efficiency (ICE) and no obvious discharge platform during K+-intercalation/deintercalation, thus restricting their practical application. Herein, the cheap and renewable sanitary tissue is utilized as the precursor to construct a flexible self-supporting hard carbon microbelt paper (HCMB). As a binder-free anode, the HCMB can achieve a high ICE value of 88% with a high charge capacity below 1 V (204 mAh g−1 at 100 mA g−1), excellent rate capability (151 mAh g−1 at 1000 mA g−1) and superior cycling stability in a conventional KPF6-based electrolyte. More importantly, the HCMB-based anodes exhibit a rather low discharge platform, which is close to graphite anode (0.25 V vs. K/K+). To demonstrate its practical use, a novel 4.5 V potassium ion capacitor (PIC) device is successfully constructed based on the HCMB anode and the activated carbon cathode together with the gel polymer electrolyte. The energy density of this hybrid system is up to 152 W h kg−1, and still maintains as high as 112 Wh kg−1 at a high power density of 17500 W kg−1. In addition, the effect of the carbonization temperature on the K+-storage behavior of HCMB and its comparison with carbon counterparts (graphite and soft carbon) are systematically investigated.

Stable cycling of potassium metal anodes in classic carbonate electrolytes remains a great challenge. Three-dimensional carbon hosts have been widely adopted to address the low Coulombic efficiency and devastated dendrite growth, but a correlation between the carbon microstructure and potassium plating/stripping stability has yet to be established. Here, stark contrasted carbonization temperatures, i.e., 800 and 2800 °C, are applied to electrospun carbon nanofiber (CNF) films for regulating graphitization degree. The resulted CNFs demonstrate distinct stability when serving as hosts for potassium metal anodes. We reveal that the carbon microstructure has a huge impact on not only the nucleation and diffusion of the K ions but also the mechanical properties of solid electrolyte interphases (SEIs). The maximum elastic deformation energy (U), which reveals the combined effects of Young's modulus and yield strain, is utilized to reflect the capability of SEI in accommodating the electrode deformation upon K deposition. The CNFs prepared at 2800 °C benefit the formation of a high U-value SEI. Consequently, it exhibits a small polarization and an ultra-long life of over 2000 h at 0.5 mA cm−2 in the carbonate electrolyte.

A series of coal-based hierarchical porous carbons with adjustable pores were successfully prepared with the assistance of the soluble salt Zinc chloride (ZnCl2). During the carbonization process, ZnCl2, with a low melting point (238 °C), “in situ occupied” and “occupied” within the coal solids to generate interconnected pores, which acted as a template. Simultaneously, the activation of ZnCl2 reduced the oxygen content of products and further improves their electrical conductivity. Optimization of the mass of the salt and the carbonization temperature resulted in targeted product with a suitable specific surface area (1581 m2 g−1) and unique pores (Vmeso/Vtotal = 45%), which exhibited a high specific capacitance (470.7 F g−1 at 0.5 A g−1) in 6 M KOH electrolyte. The symmetrical supercapacitor of targeted product has favorable rate performance (256.7 F g−1 at 0.5 A g−1, 84.8% capacity retention at 30 A g−1) and excellent cycling performance (after 10000 cycles, the specific capacitance increases to 115% of the initial capacity at 10 A g−1). In the EMIMBF4 electrolyte system, the energy density is 95.31 Wh kg−1 at 213.13 W kg−1. Therefore, this work provides an effective method to improve the green and efficient use of coal.

The nitrogen-doped carbon (NC) coating encapsulating heterostructural Sn/SnO2 microcube powders (Sn/SnO2@NC) are successfully fabricated through hydrothermal, polymerization of hydrogel, and carbonization processes, in which the SnO precursor powders exhibit regular microcube structure and uniform size distribution in the presence of optimized N2H4·H2O (3.0 mL of 1.0 mol/L). Interestingly, the precursor powders are easily subjected to a disproportionated reaction to yield the desirable heterostructural Sn/SnO2@NC microcube powders after being calcined at 600 °C in N2 atmosphere in the presence of home-made hydrogel. The coin cells assembled with the Sn/SnO2@NC electrode present a high initial discharge specific capacity (1058 mAh g−1 at 100 mA g−1), improved rate capability (an excellent DLi+ value of 2.82 × 10-15 cm2 s−1) and enhanced cycling stability (a reversible discharge specific capacity of 486.5 mAh g−1 after 100 cycles at 100 mA g−1). The enhanced electrochemical performance can be partly ascribed to the heterostructural microcube that can accelerate the transfer rate of lithium ions by shortening the transmission paths, and be partly to the NC coating that can accommodate the volume effect and contribute to partial lithium storage capacity. Therefore, the strategy may be able to extend the fabrication of Sn/SnO2 heterostructural microcube powders and further application as promising anode materials in lithium ion batteries.

Non-noble metal catalyst with high catalytic activity and stability towards oxygen reduction reaction (ORR) is critical for durable bioelectricity generation in air-cathode microbial fuel cells (MFCs). Herein, nitrogen-doped (iron-cobalt alloy)/cobalt/cobalt phosphide/partly-graphitized carbon ((FeCo)/Co/Co2P/NPGC) catalysts are prepared by using cornstalks via a facile method. Carbonization temperature exerts a great effect on catalyst structure and ORR activity. FeCo alloys are in-situ formed in the catalysts above 900 °C, which are considered as the highly-active component in catalyzing ORR. AC-MFC with FeCo/Co/Co2P/NPGC (950 °C) cathode shows the highest power density of 997.74 ± 5 mW m−2, which only declines 8.65% after 90 d operation. The highest Coulombic efficiency (23.3%) and the lowest charge transfer resistance (22.89 Ω) are obtained by FeCo/Co/Co2P/NPGC (950 °C) cathode, indicating that it has a high bio-electrons recycling rate. Highly porous structure (539.50 m2 g−1) can provide the interconnected channels to facilitate the transport of O2. FeCo alloys promote charge transfer and catalytic decomposition of H2O2 to •OH and •O2−, which inhibits cathodic biofilm growth to improve ORR durability. Synergies between metallic components (FeCo/Co/Co2P) and N-doped carbon energetically improve the ORR catalytic activity of (FeCo)/Co/Co2P/NPGC catalysts, which have the potential to be widely used as catalysts in MFCs.

Carbon aerogels are prepared by a thermal treating-freeze drying approach from chitosan, with glycine hydrochloride ionic liquid (IL) acting as solvent and nitrogen source. Different post-treatments such as ball milling and high temperature carbonization are employed to functionalize the obtained carbon aerogels with tuned properties, making it promising candidates as fluorescence material (NACs-Q), electrode material (FDC-800) and catalyst support (NACPd-C). NACs-Q is water-soluble quantum dot with average particle sizes of 3.8 nm, presenting excitation-/emission-independent and pH-sensitive properties, which could be used as sensor for testing acetone vapor or an “on-off-on” sensor for detections of Fe3+ and vitamin C in fruits. FDC-800 exhibits fluffy lamellar structure with developed micro-mesopores and nitrogen-containing groups on their surfaces, which is beneficial for building flexible solid-state supercapacitor with excellent performance, delivering a capacitance of 208F/g at 0.5 A/g, and achieving an energy density of 7.2 W h/kg at a power density of 50 W/kg. Moreover, NACPd-C can be used as catalyst for phenol hydrogenation, and phenol conversion of 100% with cyclohexanone selectivity of 98.3% is achieved, due to the synergetic effects of the Pd active-site, the N-containing groups, and the Lewis acid sites on the support.

The nonprecious electrocatalyst with high electrocatalytic activity and low cost is urgently desired to fulfill the demands of efficient rechargeable Zn-air batteries (ZABs). Herein, the heteroatom functional carbon-based nanocage Zn-NC is prepared through pyrolysis of ZIF-8. In this process, the organic ligands are converted into partially graphitized carbon with simultaneously reduction of Zn2+ to metal Zn, thus the nitrogen doping porous structure and homogeneous distributed zinc endow the Zn-NC more exposed active surface. Further co-heat treatment of carbonized ZIF-8 precursor with dicyandiamide and glucose results in the formation of Zn, N atomic-level modified carbon material Zn-NC/GD. The dual-shell carbon nanocage structure produces obvious interface properties, which can well bind the escaping metallic zinc to form Zn–N–C bond structure. Benefiting from double carbon modification, interfacial properties, and bonding structure, the Zn-NC/GD performs outstanding half-wave potential (0.86 V) and a lower Tafel slope (97.8 mV dec−1). Consequently, as an air electrode, the Zn-NC/GD also exhibits high open circuit voltage (1.531 V), remarkable power density (326.1 mW cm−2), and excellent specific capacity (824.7 mAh gzn−1). The critical findings demonstrate promising potential to obtain an efficient atomic-level modification of carbon-based electrocatalyst for ZABs.

Sustainable transformation and efficient utilization of biomasses and their derived materials are environmentally as well as economically compliant strategies. Biomass seaweed-derived nitrogen self-doped porous carbon with tailored surface area and pore structures are prepared through carbonization and activation. The influence of carbonization temperature on morphology, surface area, and heteroatom dopants are investigated to optimize sodium-ion storage capability. Seaweed-derived nitrogen self-doped activated carbon (SAC) as anode materials for sodium-ion batteries exhibits remarkable reversible capacity of 303/192 mAh g−1 after 100/500 cycles at current densities of 100/200 mA g−1, respectively, and a good rate capability. The interconnected and porous conducting nature along with the heteroatom dopant role in creating defective sites and charge stabilization are favorable for ion storage and diffusion and electron transport, indicating the electrodes can offer improved electrochemical performances. In addition, post-mortem analysis of the cycled carbon electrodes through ex-situ tools demonstrates the sodium-ion storage mechanism.

Advanced microwave absorption (MA) materials have attracted widespread attention to meet the challenges of electromagnetic (EM) pollution. Herein, MgFe2O4/MgO/C fibers were successfully prepared via electrospinning technology and carbonization, and their surfaces were coated by MoS2 via hydrothermal method. The EM wave absorption performance of composites was enhanced due to the introduction of MoS2. The results showed that the EM wave absorption performance of MgFe2O4/MgO/C could not meet the requirements due to low dielectric loss and poor impedance matching. The performance of the composites was improved after coating of MoS2, which showed the strong wave absorption capability and the broad absorption bandwidth. The optimal reflection loss (RL) is −56.94 dB at 9.5 GHz and the effective absorption bandwidth is 3.9 GHz (8.08–11.98 GHz) with a thickness of 2.7 mm. The excellent MA performance can be mainly attributed to excellent synergistic effect between MgFe2O4/MgO/C and MoS2. Furthermore, MoS2 also contributes to dielectric loss and ideal impedance matching. MgFe2O4/MgO/C@MoS2 composites may be utilized for lightweight and high-efficient MA materials.

Given the abundant natural reserves of potassium and its similar properties to lithium, potassium-ion batteries (KIBs) are expected to be an emerging energy storage system to replace lithium-ion batteries (LIBs). Here, to overcome the sluggish diffusion kinetics and structure collapse of the anode in current KIBs, copper tetrathiovanadate (Cu3VS4) nanoparticles uniformly loaded in carbon nanofibers (CVS/CNF) are designed as a new anode for KIBs through electrospinning and subsequent carbonization/sulfidation treatment. Benefiting from the highly conductive Cu species and CNF network, an outstanding charge transfer kinetics is achieved in CVS/CNF composites. Meanwhile, the nanosized CVS particles and robust CNF networks are believed to be beneficial for enhanced structural stability during potassium insertion, and thus endow the composite anode with an excellent long-term capability. The CVS/CNF composite anode displays a high capacity (486 mA h g−1 at 0.1 A g−1), great rate feature (162 mA h g−1 at 6 A g−1) and outstanding cycling performance (193 mA h g−1 after 2000 cycles at 1 A g−1), which are superior to those of most of the reported transition metal sulfide anodes.

Carbon origami has been recently reported to enable the fabrication of lightweight, 3D and architected shapes of carbon materials using renewable cellulose paper as the carbon precursor. Here, we characterize the effect of different processing variables on the mechanical stiffness of carbon origami shapes. The study is conducted using a Miura-ori pattern. The processing variables studied here include the geometrical features of the unit cell of a Miura-ori pattern, carbonization conditions, and thickness of the cellulose paper. Change of the carbonization environment exhibits a stronger impact on the density and mechanical properties of the carbon origami structure, compared to the effect of final temperature of the carbonization process. Furthermore, the elastic modulus exhibited a proportional relation to a design angle α and an inversely proportional relation to a folding angle β. The elastic modulus of a carbon Miura-ori further increases with the thickness of the paper used for fabrication of the precursor origami shape. We compare the mechanical stiffness obtained from all the variables, which shows that a combination of α and β exhibits the most dominant effect. Combination of all these effects can potentially lead to fabrication of a carbon origami shape that can exhibit mechanical stiffness superior to state-of-the-art cellular materials at a given low density. Further optimization of the processing parameters is needed to achieve such a carbon origami structure.

Reasonable control of the redox states within the catalytic units together with the interconnection degrees of the substrate is of great significance in the modulation of a well-performing transducer. Herein, a novel carbon black (CB)-modified copper metal–organic framework nanomaterial (CB@Cu-MOF) prepared at room temperature was utilized as a precursor to synthesize mixed-valent copper–oxide composite catalysts (NC/CuxO-T). By tuning the carbonization process of the precursor at different temperatures (T = 100 °C, 200 °C, 300 °C and 400 °C), the different ratio configurations of the redox-alternated CuxO portions were successfully controlled with the simultaneous effective tailoring of the defect abundance in the N-doped carbon substrate. As a result, an optimized NC/CuxO-300 electrochemical H2O2 sensor was able to present a low detection limit (0.26 μM) and decent linear ranges (0.02–1.79 mM and 2.29–9.29 mM). Our strategy using easily available initial materials with mild preparation conditions is expected to promote the practical application of the star materials in laboratories.

The high-efficiency catalyst for the reduction of nitroarenes with hydrogen under room temperature has always been paid much attention to. Herein, using a kind of hydroxyl-terminated hyperbranched ...

The rational design of an excellent architecture for active materials combined with carbon matrix is of particular importance to obtain flexible electrode material with high electrochemical properties. Well-designed nanofibers possess unique 3D network structure, which can significantly improve the electron/ion transportation and supplies sufficient active sites for Li+/Na+ insertion. Electrospinning-carbonization technology is a popular strategy to prepare nanofibers with active material embedded in carbon. It is found that the architecture of nanofibers tended to be wrecked and destroyed during the carbonization process without pre-oxidation treatment. In this study, we prepared Na2MnPO4F particles embedded in carbon nanofibers (Na2MnPO4F/C) using PVP as carbon source and investigated the strengthen mechanism of pre-oxidation on their architecture. The experiment and simulation results demonstrate that, without pre-oxidation, the main chain of PVP is severely ruptured during the carbonization procedure, consequently leads to fractured architecture of Na2MnPO4F/C nanofibers. In contrast, with pre-oxidation treatment, a long-chain and heat-resistance structured carbon matrix formed, and Na2MnPO4F/C nanofibers with stable architecture and improved electrochemical performance can be achieved. This study demonstrates a promising guide to construct carbon based nanofiber electrodes with stable architecture and high electrochemical performance.

Thermally insulating and fire-resistant carbon composite foams are prepared by consolidating natural cotton fibre dispersed in aqueous sucrose solution by filter-pressing followed by drying and carbonization. The compressive strength (5 kPa to 1.4 MPa) and thermal conductivity (0.069 to 0.185 W m − 1 .K − 1) depend on the foam density (0.06 to 0.31 g cm−3) which is modulated by varying the sucrose solutions concentration (100 to 700 g L − 1). Partially flexible to the rigid transition of the carbon composite foams occurs at sucrose concentration above 200 g L − 1. The tubular carbon fibre formed from cotton is welded at their contact points by the amorphous carbon produced from sucrose leading to partial flexibility at low sucrose concentration and advancement of fibre- to- fibre bonding area at higher sucrose concentration results in rigid foam. The porosity in the inter-fibre space and lumen of the carbonized cotton fibre contributes to the low thermal conductivity. The carbon composite foams prepared at a sucrose solution concentration of 500 g L − 1 and above are amenable to machining using conventional machines and tools. The rigid carbon foams show EMI shielding effectiveness and specific shielding effectiveness in the ranges of 21.5 to 38.9 dB and 108–138 dB cm3 g − 1, respectively.

Photo-thermal conversion is one of the effective ways to utilize solar energy. Regarding the intermittence and instantaneousness of solar energy, using phase change materials (PCMs) can solve this issue by storing the obtained thermal energy. In this paper, Balsa wood (BW) is treated by delignification and carbonization firstly. Then the carbonized wood (CW) with regular pore structure is introduced into the PCMs as the supporting and photo-thermal conversion media by vacuum impregnation method. The microstructure and thermal properties of the woods and composite PCMs are tested by SEM, POM, MIP, FT-IR, DSC, and TG. The results indicate that the CWs present a similar porous structure to BW, and its porosity is as high as 92.03%. The PCMs are packaged in the porous structure of CWs due to the surface tension and capillary forces, and the maximum effective impregnation ratio of the PCMs into the CW-3 reaches to 85.25 wt%. The phase change temperature and latent heat of CW-3/OP44E are measured as 41 °C and 206.3 J/g, respectively. Moreover, the composite PCMs possess a suitable photo-thermal conversion property, and the photo-thermal conversion efficiency of the composite PCM CW-3/OP44E is 90%. The good thermal stability also indicates its potential application in the thermal energy storage system.

Transforming waste resources into energy storage materials is a new way to turn waste into treasure and solve the problem of energy shortage and environmental pollution in current society. In this paper, nitrogen/phosphorus co-doped activated carbon material was synthesized from the waste cotton fabric by one-step carbonization and activation in molten salt system combined with ammonium polyphosphate co-doping technology. The morphology, structure and composition of the materials were characterized by scanning electron microscopy (SEM), nitrogen adsorption desorption (BET), Raman spectroscopy (Raman) and X-ray photoelectron spectroscopy (XPS). The cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) were used to test the supercapacitor performance of the prepared materials. The results show that the waste cotton fabric, which is mixed with ammonium polyphosphate in the ZnCl2/KCl molten salt medium, then treated by carbonization and activation under high temperature, generates the nitrogen/phosphorus co-doped activated carbon with the specific surface area of 751 m2·g−1. In the three-electrode system, the specific capacitance is as high as 423 F·g−1 (at a current density of 0.25 A·g−1), and its capacitance retention is as high as 88.9% of the initial capacitance after 5000 cycles at a current density of 5 A·g−1. Meanwhile, when the material was assembled into a symmetrical supercapacitor, the achieved energy density can be up to 28.67 Wh·kg−1 at a power density of 200 W·kg−1. According to these results, converting waste cotton fabric resources into energy storage materials has succeeded in achieving high value-added reuse of waste textiles.

Extensive research to explore cost-effective carbon materials as electrocatalysts and electrode materials for energy conversion and storage has been conducted in the recent literature. This raised a crucial question regarding the origin of this electrocatalytic activity from the heteroatom doping/ hierarchical porous defect-rich architecture and/ or the trace metal impurities introduced during synthesis/ inherent to the precursor. In this work, an insight into this issue is provided by considering a lignocellulosic biowaste, Euryale Ferox (foxnut) shells as a precursor to derive micro/ mesoporous defective graphitic carbon sheets by the phosphoric acid (H3PO4) dictated in-situ carbonization for oxygen reduction reaction (ORR) and supercapacitor applications. The sample synthesized at 900 °C (FP900) shows an onset potential of 0.98 V vs. reversible hydrogen electrode (RHE), ORR current density of 5.5 mA cm−2, and current stability of 93% (in 10 h measurement) in 0.1 M KOH. In addition, a symmetric supercapacitor device is assembled using the prepared material and the specific capacitance of 207.5 F g−1 at 1 A g−1 is obtained. An attempt to explain the origin of the electrochemical performance is made by establishing parallels with the physicochemical characterizations. The inherently doped heteroatoms give rise to electroactive functionalities and the wide enough pore size distribution improves the active sites utilization efficiency by enhancing the accessibility to electrolytic ions resulting in better electrochemical performance. Furthermore, the contribution from the intrinsic trace metal impurities is evaluated using X-ray fluorescence (XRF) spectroscopy. The presented research clarifies the non-contributing nature of trace metal species owing to the inaccessibility of active sites and lower abundance in F900 and FP900, respectively.

Micro/mesopore carbon spheres as electrode materials of supercapacitors were prepared by hydrothermal carbonization followed by KOH/NaOH activation using sucrose as the carbon precursor. The effects of KOH and NaOH activation parameters on the specific surface area, pore size distribution and electrochemical performance of the carbon spheres were investigated. Results indicate that the use of NaOH leads to the development of mesopores while the use of KOH is favorable to increase specific surface area and micropore volume. The pore size distribution of carbon spheres could be adjusted by varying the fraction of NaOH in the activation agent. A balanced capacitance and rate performance of the supercapacitor electrode in both 6 mol L−1 KOH aqueous electrolyte and 1 mol L−1 MeEt3NBF4/PC electrolyte is achieved when the carbonized product is activated at a mass ratio of NaOH+KOH/ carbonized product of 3∶1 with a NaOH/KOH mass ratio of 2∶1. As-prepared porous carbon delivers a capacitance of 235 F g-1 at 0.1 A g-1 and capacitance retention rate of 81.5% at 20 A g-1 in the 6 mol L−1 KOH aqueous electrolyte. In 1 mol L−1 MeEt3NBF4/PC, the cell based on the porous carbon delivers the highest energy and power output of 30.4 Wh kg−1 and 18.5 kW kg−1, respectively.