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A grand challenge in the state-of-the-art porous carbons is the lack of reliable synthesis strategy for achieving ultrahigh surface areas while maintaining a high carbonization yield. Generally, the realization of the ultrahigh surface area depends on the inherent properties of the starting precursors. Meanwhile, excessive development of porosity (>3500 m2 g−1) will undoubtedly give rise to low carbonization yield (

Aqueous zinc ion battery constitutes a safe, stable and promising next-generation energy storage device, but suffers the lack of suitable host compounds for zinc ion storage. Development of a facile way to emerging cathode materials is strongly requested toward superior electrochemical activities and practical applications. Herein, defect engineering, i.e., simultaneous introduction of nitrogen dopant and oxygen vacancy into commercial and low-cost MnO, is proposed as a positive strategy to activate the originally inert phase for kinetically propelling its zinc ion storage capability. Both experimental characterization and theoretical calculations demonstrate that the nitrogen dopant significantly improves the electric conductivity of electrochemical inert MnO. Simultaneously, the oxygen vacancy creates sufficient large inserted channels and available activated adsorption sites for zinc ions storage. These synergistic structural advantages obviously ameliorate the electrochemical performance of inert MnO. Therefore, even without any conductive agent additive, the as-prepared material shows high specific capacity, superb rate capability, prolonged cycling stability and attractive energy density, which are dramatically superior to those of the pristine MnO as well as many other host cathode materials. This work presents fresh insights on the role of defect engineering in the enhancement of the intrinsic electrochemical reactivity of inert cathode, and an effective strategy for scalable fabrication of high-performance cathode for zinc ion battery.

In light of the silicon-reservoir feature of renewable natural resources, the exploitation of the inexpensive biomass towards high value-added silicon-based materials has achieved great attention. However, the biomass-derived silicon is usually extracted by high-temperature metal-reduction, which tends to trigger side reaction and collapse the porous structure. Herein, introducing molten-salt assisted low-temperature aluminothermic reaction, we have fabricated micro/meso-porous carbon network embedded nano Si-SiOx@C (Si-SiOx@C/C) composites directly using sugarcane leaves as silica and carbon sources. This low-temperature synthesis strategy can perfectly preserve the three-dimensional (3D) carbon network embedded by fine Si-SiOx@C nanoparticles, which is beneficial to enhancing the electrochemical conductivity, reducing volume change, and stabilizing solid electrolyte interface membranes. In addition, the content of Si in SiOx can be controlled by the reduction temperature and reaction time. Consequently, the optimized SC-250-16 anode establishes a favorable reversible capacity (1562.8 mAh g−1 after 400 cycles at 200 mA g−1) and superior cyclability at high rates (678.6 mAh g−1 after 3000 cycles at 2 A g−1). Furthermore, the SC-250-16//LiFePO4 full cell delivers a prominent energy density of 412.1 Wh kg−1. This molten-salt assisted low-temperature reaction strategy can boost the advancement of 3D porous Si/C anodes and their relevant functional composites derived from other biomasses.

In this work, a simple and efficient method is introduced to prepare biomass-based porous carbon with excellent performance by changing the content of component (e.g., cellulose, hemicellulose, lignin, and extractives) of the raw materials. When the content of the components change, the corresponding carbon skeleton will be separated, resulting in a structure that is conducive to activation conditions. Using bagasse with fiber tubular structure as carbon precursor, the synthetic hierarchical porous carbon (BHPC-4) possesses a high specific surface area (SSA) of 3135 m2 g−1 more than the control sample (2484 m2 g−1). Benefitting from the improvement of the structure, the BHPC-4 electrode exhibits an appealing capacitance of 410.5F g−1 at 0.5 A g−1 and long-term cycling stability of 100% capacitance retention after 10,000 cycles in the 6.0 M KOH system. Furthermore, a delightful energy density of 25.6 Wh kg−1 at a 226 W kg−1 can be achieved in 1.8 V Na2SO4 aqueous symmetrical supercapacitors. This method has universal significance in preparing high-porosity and high-performance biomass-based carbon materials for various energy storage/conversion.

Spherical carbon materials exhibit great competence as electrode materials for electrochemical energy storage, owing to the high packing density, low surface to volume ratio, and excellent structure stability. How to utilize renewable biomass precursor by green and efficient strategy to fabricate porous carbon microspheres remains a great challenge. Herein, we report a KOH-free and sustainable strategy to fabricate porous carbon microspheres derived from cassava starch with high specific surface area, high yield, and hierarchical structure, in which potassium oxalate monohydrate (K2C2O4·H2O) and calcium chloride (CaCl2) are employed as novel activator. The green CaCl2 activator is crucial to regulate the graphitization degree, specific surface area, and porosity of the carbon microspheres for improving the electrochemical performance. The as-prepared carbon microspheres exhibit high specific surface area (1668 m2 g−1), wide pore size distribution (0.5–60 nm), high carbon content (95%), and exfoliated surface layer. The hierarchical porous carbon microspheres show high specific and areal capacitance (17.1 μF cm−2), superior rate performance, and impressive cycling stability. Moreover, the carbon microspheres based symmetric supercapacitor exhibits high capacitance and excellent cycling performance (100% after 20 000 cycles at a current density of 5 A g−1). This green and novel approach holds great promise to realize low-cost, high-efficient and scalable of renewable cassava starch-derived carbon materials for advanced supercapacitive energy storage applications.

Microporous carbons with large oxygen content have been successful synthesized from biomass by the sodium alginate assisted strategy. During the activation process, the Na2O formed by the decomposition of sodium alginate combines with the activator KOH to undergo a redox reaction in situ with precursor, thereby forming a rich porosity in the samples. The obtained samples possess not only high SSA (2310~3001 m2 g−1) and large pore volume (0.89~1.19 cm3 g−1) arising almost completely (>90%) from micropores, but also retains a high content of oxygen (21.86~32.47 wt %). As supercapacitor electrodes, the oxygen-doped microporous carbons display a high specific capacitance of 385 F g−1 at 0.5 A g−1 with capacity stability of 91.5% after 20 000 cycles at 5 A g−1. As hydrogen storage materials, the oxygen-doped microporous carbons exhibit enhanced hydrogen storage capacity of 2.84 wt% (77 K, 1 bar) and 0.91 wt% (303 K, 50 bar). Experimental data indicate that this work provides a simple-efficient and universal strategy for preparing oxygen-doped microporous carbon for high-performance energy and hydrogen storage.

Porous carbon has been constructed in various strategies for hydrogen storage. In this work, a simple-effective strategy was proposed to transform sustainable biomass into porous carbon by degrade partial lignin and hemicellulose with Na2SO3 and NaOH aqueous mixture. This method collapses the biomass structure to provide more active sites, and also avoid the generation and accumulation of non-porous carbon nanosheets. As a result, the as-prepared sample possesses high specific surface area (2849 m2 g−1) and large pore volume (1.08 cm3 g−1) concentrating almost completely on micropore. Benefit to these characteristics, the as-prepared sample exhibits appealing hydrogen storage capacity of 3.01 wt% at 77 K, 1 bar and 0.85 wt% at 298 K, 50 bar. The isosteric heat of hydrogen adsorption is as high as 8.0 kJ mol−1, which is superior to the most biochars. This strategy is of great significance to the conversion of biomass and the preparation of high-performance hydrogen storage materials.

The ever-increasing electric vehicles and portable electronics make lithium-ion barreries (LIBs) toward high energy density, resulting in long driving range and standby times. Generally, excellent electrochemical performance can be obtained in thin electrode materials with low mass loadings ( 10 mg cm−2). In this work, we report a facile method for fabricating nitrogen doped carbon microtubes (N-CMTs) consisted of crumped carbon nanosheets for high-performance LIBs with ultrahigh mass loading, where non-tubular biomass waste (i.e., peanut dregs) is employed as the precursor. Benefiting from the hollow tubular conductive network, high graphitization, and hierarchical structure, the as-synthesized N-CMTs exhibit ultrahigh area capacity of 6.27 mAh cm−2 at a current density of 1.5 mA cm−2 with a high mass loading of 15 mg cm−2 and superior cycling stability for LIBs. Our approach provides an effective strategy for the preparation of nitrogen-doped carbon microtubes to develope high energy LIBs with high mass loading electrodes.

Recently, researchers are no longer satisfied with the investigation of the fluorescence properties of carbon dots (CDs), but instead focus on the more attractive afterglow luminescence, especially room temperature phosphorescence (RTP) and thermal activation delayed fluorescence (TADF). Numerous attempts have been made to construct CD-based afterglow materials, including embed CDs in various rigid matrices or construct self-protective structures. Because of the diversity of construction methodologies, different mechanisms and effects would be produced, thus resulting in distinguishing afterglow characteristics. Afterglow of CDs in organic matrices is mainly due to the formation of hydrogen bonds, which can suppress intramolecular vibration and stabilize triplet states, thus generating afterglow emission. Afterglow of CDs in diverse inorganic matrices are completely different because the multifarious interactions between CDs and different matrices are generated (e.g., rigid structure covalent bonds, structural confinement, energy transform, etc). The self-protective CDs always possess polymer-like structure or polymer-chains on their surface, which can act as rigid matrix to activating afterglow emission. This review aims to sum up the relationships between structure construction and afterglow characteristics, and the mechanism of afterglow generation, which are of great significance for stimulating more exciting progress in the purposeful design of afterglow materials.

Evolution of fast-charging alkali-metal ion battery (AIB) is of great importance, but severely limited by the high ion/electron transport resistance in the electrode structure. Carbon-based composites have demonstrated competitive results for accelerating the related technology development. However, their efficient design, versatile synthesis and diverse structural variability remain the major challenges. Herein, we propose a general and versatile protocol for synthesizing a hierarchical network structure composed of metal compound (e.g., metal oxide, metal selenide and metal sulfide) encapsulated in carbon nanoparticle unit, and demonstrate its superiority for fast-charging anode of AIB. Key to this strategy is utilization of a rational hybrid assembly comprising of chelating resin and metal ions as building blocks. The strong coordinate-covalent bond between chelating resin and metal ions not only realizes a highly homogeneous organic/inorganic interface at the molecular level, but also confines metal ions to in-situ generate metal compound nanoparticles uniformly distributed into the carbon framework after a carbonization treatment, endowing a strong binding at the carbon/non-carbon interface structure. Benefitting from the well-organized structure, the resultant network-structured metal compound@carbon composites exhibit extraordinary fast-charging alkali-metal ion storage performance. For example, the typical network-structured Fe2O3@carbon composite anode can be fully charged within 2.2 ​min and discharge continuously for more than 120 ​min with a large charge/discharge capacity of 730 ​mAh g−1 in lithium ion batteries, and is able to be fully charged within 5.6 ​min accompanying with a long discharge time of about 110 ​min and a high charge/discharge capacity of 92 ​mAh g−1 in potassium ion batteries.

Abiotic stress severely threatens agriculture. Herein, we studied the effect of heteroatom-free carbon dots (CDs) on the alleviation of abiotic stresses in rice for the first time. During in vitro coincubation, suspended rice cells were exposed to 2,4-dichlorophenoxyacetate sodium (2,4-D-Na, 30 μg mL-1), 2,4-dichlorophenoxyacetic acid (2,4-D, 5 μg mL-1), NaCl (0.15 mol·L-1), and high light (2000 Lux), both with and without CDs (100 μg mL-1). After a week, CDs significantly reduced the inhibition rate of 2,4-D-Na on the rice cell biomass from 48.16 to 27.44% and increased the biomass of rice cells exposed to 2,4-D, NaCl, and high light, by 4.12, 1.10, and 4.01 times that of the control (pure nutrient medium), respectively. Furthermore, the growth of CD-germinated rice seedlings was not obviously affected by 2,4-D-Na, 2,4-D, and NaCl. Further results showed that the CDs demonstrated an intrinsic free-radical scavenging property and could increase the peroxidase activity and the contents of phenolics and flavonoids in rice by 125.81, 39.60, and 47.63%, respectively. Furthermore, CDs improved the nutrient assimilation of rice cells under 2,4-D stress by 14.69%. With higher antioxidant capacity and sufficient nutrients, the CD-treated rice showed excellent resistance to abiotic stresses. This study suggested the great potential of CDs in protecting crops against abiotic stress.

Potassium-ion batteries (KIBs) have been developed as an emerging electrochemical energy storage device due to the low cost and abundant resource of potassium. However, they suffer insufficient cyclability and poor rate capability caused by the large K+, severely limits their further applications. Herein, a nanonetwork-structured carbon (NNSC) is reported to address the issue. Cycling stability with very low decay rate of 0.004% per cycle over 2000 cycles and excellent rate capability (i.e., 261 mAh g−1 at 100 mA g−1 and 108 mAh g−1 at 5000 mA g−1) are achieved. The superior performance is attributed to the unique structure of NNSC, in which the three-dimensional interconnected hierarchical porous structure with hollow nanosphere as network units not only can effectively alleviate the volume expansion induced by the insertion of large K+, but also can offer fast pathways for K+ diffusion. In addition, the local graphitized carbon shell of NNSC can promote conductivity of material and reduce the resistance to K+ transportation. Thus, the NNSC has great potential in developing stable-structure and high-rate electrodes for next generation KIBs.

Two-dimensional carbon-based composite nanosheets (2D-CCNSs) are expected to be promising electrodes for fast charging lithium-ion batteries. Even though synthesis procedures exist for these materials, current approaches often require rigid reaction conditions and complicated synthetic steps. Herein, we develop a facile and general approach to fabricate a new type of 2D-CCNSs and demonstrate its superiority as a high-rate anode for lithium-ion batteries. It is found that the introduction of a nanocellulose as building unit can guide itself to self-assemble with polydopamine and metal ions to form a 2D inorganic–organic hybrid, which can be directly transformed into 2D-CCNSs after a carbonization treatment without structural deterioration. Unlike common 2D-CCNSs with a pure graphitic or amorphous carbon framework, the as-constructed materials possess a distinctively heterogeneous carbonaceous skeleton comprising graphitic nanorods with a crystalline framework and amorphous carbon with a microporous structure. The synthetic strategy is also demonstrated to be general for embedding numerous metal oxides, such as Fe2O3, CoO, NiO nanoparticles, into the carbon framework just by adjusting the types of metal ions. Profiting from the well-orchestrated structure, the as-prepared 2D-CCNSs exhibit impressive high-rate lithium ion storage performance. For instance, after being fully charged within 40.8 s, a long discharge time as high as 342 min can be achieved accompanied with a high and stable reversible capacity of 560 mA h g−1.

Afterglow including thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) has stimulated considerable attention owing to bright potential applications in optoelectronic devices, sensing, and security systems. However, previously reported afterglow materials are mostly single-mode (one of RTP or TADF only), a tunable multi-mode afterglow emission is still rarely achieved. Herein, we report the temperature-responsive conversion characteristics of TADF and RTP of carbon dots in silica (CDs@SiO2) for the first time. The unique temperature-responsive afterglow characteristics, that is, phosphorescence and TADF can be mutually transformed as the temperature changes, resulting in the free conversion of the RTP/TADF ratio as well as the afterglow color change through simple temperature control. The Si–O network plays multiple roles to strengthen and confine the embedded CDs, thus resulting in ultralong RTP emission and unique afterglow characteristics. Furthermore, CDs@SiO2 exhibited excellent stability against water, acid, alkali, salt and oxidants as well as polar solvents. CDs@SiO2 with unique afterglow characteristics and high stability can have multiple potential applications in rapid fingerprint detection and temperature sensing, especially in advanced temperature-responsive multicolor anti-counterfeiting and encryption.

Exploration of effective ways to highly porous carbon is a critical but remains challenging issue for high-performance supercapacitors. Here, we propose a new and facile strategy to synthesize polyacrylonitrile-based porous carbon (PPC) material. The as-prepared PPC not only possesses a well-defined hierarchical pore structure, but also exhibits the highest BET surface area of 3751 m2 g−1 and the largest pore volume of 2.48 cm3 g−1 among all the materials derived from polyacrylonitrile. The key to this preparation strategy is utilization of KNO3 as a mediator for pre-oxidation of polyacrylonitrile, which leads to construction of a fluffy and rigid semi-carbonized framework for the easy accessibility of activator KOH. Benefiting from the well-developed porosity, the PPC electrode exhibits an unusually high capacitance of 448 F g−1 at 0.5 A g−1 and an outstanding long-term stability of 96.5% capacitance retention after 10000 cycles in 1.0 V aqueous supercapacitors. Additionally, a remarkable energy density of 23.6 Wh kg−1 can be delivered at a high out-put power density of 220 W kg−1 in 1.8 V aqueous supercapacitors. These attractive electrochemical properties enable PPC to go far beyond many reported carbonaceous electrodes, which is expected to be as competitive candidate for high-performance supercapacitor electrode.

Hierarchical Fe2O3 and SnO2 nanostructures have shown great potential for applications in high-performance ion batteries because of their superiority, including wide resources, facile preparation, environmental friendliness, and high energy density. However, some severe challenges, such as rapid capacity decay due to volume expansion upon cycling and poor conductivity, limit their rate performance. To address this issue, multishelled Fe2O3@SnO2@C (FSC) nanotubes were designed and synthesized by using a template method and Ostwald interaction. The as-prepared FSC nanotubes can deliver a high capacity of 1659 mA h g-1 at a current density of 200 mA g-1 and a high reversible capacity of 818 mA h g-1 at 2000 mA g-1 for lithium-ion batteries. Particularly, a high specific capacity of 1024 mA h g-1 is still maintained after 100 charging/discharging cycles at 200 mA g-1. Applied in sodium-ion batteries, the multishelled FSC nanotubes manifest a high specific capacity of 449 mA h g-1 after 180 cycles at 50 mA g-1. Such excellent performances of the as-fabricated FSC nanotubes may be due to the unique multishelled tubular structure, porous characteristics, and high specific surface area. Therefore, the present work provides an outstanding method to improve the energy storage performance of metal oxide composites and other types of nanocomposites.

The specific surface area, pore volume, and pore size distribution of biomass-derived porous carbon are crucial factors when they are applied in energy and gas storage. Each application has specifi...

In this work, a facile and effective route is introduced to optimize the performance of biomass-based porous carbon materials by partially degrading the component (e.g., lignin, hemicellulose, and ...

In this paper, a common low-cost chemical material-polyacrylonitrile (PAN) is transformed into porous carbon with excellent specific surface area (2564.6–3048.8 m2 g−1) and highly concentrated micropore size distribution (0.7–2.0 nm). Benefit to the unique structure, the as-prepared materials show appealing hydrogen adsorption capacity (4.70–5.94 wt % at 20 bar, 7.15–10.14 wt % at 50 bar), demonstrating a promising prospect of practical application. This work also confirmed that the narrow and deep ultramicropore ( 20 bar), which provides valuable guidance for the construction of ideal porous adsorbent for efficiency hydrogen storage.

3D porous carbon nanosheets have attracted tremendous concern for their large opened layer with an ultrahigh specific surface area and superb electronic transportation capability. However, the high...

A cost-effective route is developed to fabricate hierarchically porous carbons (HPCs) from renewable mixed-biomass wastes of crab shells and rice husks by hydrothermal carbonization followed by KOH...

It is a long-lasting challenge to design and synthesize electric double-layered electrode materials with suitable graphitization strength, simultaneously working to achieve a high capacitance for e...

A superb supercapacitor with high specific capacitance and high rate capacitance has been developed from taro epidermis biomass-derived carbon materials through a mild carbonizing and activation pr...

In this work, a non-toxic and mild strategy was presented to efficiently fabricate porous and nitrogen-doped carbon nanosheets. Silkworm cocoon (SCs) acted as carbon source and original nitrogen source. Sodium carbonate (Na2CO3) could facilitate the SCs to expose silk protein and played a catalytic role in the subsequent activation of calcium chloride (CaCl2). Calcium chloride served as pore-making agent. The as-obtained carbon materials with protuberant porous nanosheets exhibit high specific surface area of 731 m2 g−1, rich native nitrogen-doped of 7.91 atomic %, wide pore size distribution from 0.5 to 65 nm, and thus possessing high areal specific capacitances of 34 μF cm−2 as well as excellent retention rate of 97% after 20 000 cycles at a current density of 20 A g−1 in 6 M KOH electrolyte. The assembled carbon nanosheet-based supercapacitor displays a maximum energy density of 21.06 Wh kg−1 at the power density of 225 W kg−1 in 1 M Na2SO4 electrolyte. Experimental results show that a mild and non-toxic treatment of biomass can be an effective and extensible method for preparing optimal porous carbon for electrochemical energy storage.

Facile fabrication of anode materials with low cost, good rate capability and high capacity is a critical factor towards developing sodium-ion battery for practical applications. Herein, a N, O co-doped porous carbon with uniform ultramicropores (NOPC-UM), is synthesized by an in-situ ultramicro templating strategy, and demonstrated as a high-performance sodium-ion storage material. Key to this strategy is employment of an inherent KCl as untramicro template, which leads to formation of uniform size of ultramicropores and heteroatoms (i.e., N and O) doping after high-temperature pyrolysis. The as-constructed NOPC-UM delivers a large capacity of 305 mAh g−1, accompanying with a 93% specific capacity below 1.00 V, and superior cycling stability about 100% after 4000 cycles. These attractive electrochemical performances endow NOPC-UM with impressive potential use as anode materials of sodium-ion battery.

In this work, we report a universal KOH-free strategy to fabricate two-dimensional nitrogen-doped carbon nanosheets from edible oil residues. The saponification process and novel mild activators are introduced for the first time to optimize the microstructure of the nitrogen-doped carbon nanosheets. The resulting carbon nanosheets present a high specific surface area (2470 m2 g−1), wide pore size distribution (0.5–60 nm), and high nitrogen content (4.96%). As electrode materials for supercapacitors, the as-prepared nitrogen-doped carbon nanosheets exhibit a high specific capacitance of 340 F g−1 at a current density of 0.5 A g−1 and retain a high capacitance of 282 F g−1 at a very high current density of 50 A g−1, with no capacitance attenuation seen after 20 000 charge/discharge cycles in 6.0 M KOH electrolyte. The as-fabricated carbon nanosheet-based symmetric cell manifests a maximum energy density of 55.5 W h kg−1 at the power density of 369 W kg−1 and retains a high energy density of 32.3 W h kg−1 at 6180 W kg−1 in 1.0 M LiPF6 electrolyte. Experimental results reveal that this study provides an efficient and universal strategy for novel pre-treatment and KOH-free activation of nitrogen-doped carbon nanosheets with high specific surface area for high-rate and high-energy supercapacitors.

High surface area and heteroatom doping are crucial factors for porous carbon when it is used in supercapacitors. However, it still remains a huge challenge to integrate high surface area and rich heteroatoms into one material. Herein, we develop new type of N, O and S co-doped porous carbon with a highly porous structure derived from silkworm cocoons via facile carbonization and copper chloride activation. The silkworm cocoon-derived porous carbon (SC-PC) possesses both a high specific surface area (2826 m2 g−1) and a rich heteroatom weight percentage up to 21.9 wt%, including N (7.3 wt%), O (13.0 wt%) and S (1.6 wt%). Benefiting from the synergistic effects of the high surface area contributing to a large amount of ion absorption and rich heteroatom doping improving the pseudocapacitance, the SC-PC electrode displays a high specific capacitance of 435 F g−1 at 0.5 A g−1 and an excellent capacitance retention of 93.4% after 10 000 cycles in a 6 M KOH electrolyte. Moreover, the symmetric supercapacitors can deliver a high energy density of 23.0 W h kg−1 using 1 M Na2SO4 aqueous solution, demonstrating that SC-PC developed here is promising for application in supercapacitors.

Room temperature phosphorescence materials have inspired extensive attention owing to their great potential in optical applications. However, it is hard to achieve a room temperature phosphorescence material with simultaneous long lifetime and high phosphorescence quantum efficiency. Herein, multi-confined carbon dots were designed and fabricated, enabling room temperature phosphorescence material with simultaneous ultralong lifetime, high phosphorescence quantum efficiency, and excellent stability. The multi-confinement by a highly rigid network, stable covalent bonding, and 3D spatial restriction efficiently rigidified the triplet excited states of carbon dots from non-radiative deactivation. The as-designed multi-confined carbon dots exhibit ultralong lifetime of 5.72 s, phosphorescence quantum efficiency of 26.36%, and exceptional stability against strong oxidants, acids and bases, as well as polar solvents. This work provides design principles and a universal strategy to construct metal-free room temperature phosphorescence materials with ultralong lifetime, high phosphorescence quantum efficiency, and high stability for promising applications, especially under harsh conditions., For room temperature phosphorescence (RTP) materials to reach their potential for optical applications, new materials with improved performance must be realized. Here, the authors report multi-confined carbon dots as high stability RTP materials with long afterglow lifetime & high efficiency.

The development of ultrahigh-surface-area biomass-based carbonaceous electrode materials is a major science and engineering challenge for high-performance supercapacitors. Here we present a type of highly porous carbon material derived from waste bagasse by the purposeful combination of hydrothermal carbonization with chemical activation. The obtained waste bagasse-based carbon materials not only exhibit a valuable hierarchically porous structure with a honeycomb-like texture but also have a very high specific surface area. The highest specific surface area reaches 3151 m2 g–1, which is superior to those of other bagasse-based porous carbons reported so far. Benefiting from the combination of hierarchical pore structure and well-developed porosity, such a type of carbon materials serves very well when used as electrodes in both 1.0 and 1.8 V aqueous supercapacitors. For example, the as-prepared carbon electrode gives a high capacitance of 413 F g–1 at 1 A g–1 and a satisfied cycling stability of 93.4% cap...

Rational design and facile synthesis of porous carbon materials with optimized porosity are necessary to boost electrochemical performance for energy storage and conversion devices. In this work, we report the fabrication of three-dimensional (3D) highly crumpled porous carbons (HCPCs) inspired by the crumpled structure and functionality of renewable Moringa oleifera leaves by a facile postactivation-free method. The as-resulted HCPCs deliver an interconnected framework, abundant active interfaces, rich heteroatom content, and notably multidirectional porosity for fast ion transport and efficient charge storage. Employed as electrode materials for supercapacitors, the HCPCs exhibit ultrahigh rate capability of capacitance retention over 90% when increasing the current density from 1.0 to 50 A g–1 as well as outstanding cycling stability over 20 000 charge/discharge cycles. Furthermore, the HCPC-based symmetric supercapacitor manifests a high specific energy of 21.6 Wh kg–1, along with excellent structural...

Understanding the influence of pore structure on hydrogen storage behaviour is fundamental to develop high-performance hydrogen adsorbents. Nevertheless, there are rare compellent evidences to clearly clarify the relationship between pore size and hydrogen storage performance in porous materials. The main reason could be ascribed to the lack of appropriate porous model structures. Herein, we propose an interesting and convincing insight into the aforementioned important issue by designing proper well-defined three types of porous carbon materials with different pore size distributions. Except for the pore size distribution, these porous carbons are derived from the same source (i.e., chitosan), and have very similar surface area of ca. 3300 m2 g−1, grain morphology and carbon microcrystalline framework structure. With these features, the obtained carbon materials can be adopted as appropriate objects to evaluate the correlation of the pore size with the hydrogen storage performance. It is demonstrated that the presence of nanopore with size from 1.5 to 2.5 nm can significantly improve high-pressure hydrogen storage capacity. Moreover, nanopores with size below 1.5 nm are indeed the most efficient hydrogen storage spaces no matter at low pressures or high pressures, whereas those mesopores with size above 2.5 nm are believed to not participate in the hydrogen storage. These results convincingly indicate that there indeed exists a strong contribution of the pore size to high hydrogen storage capacity.

A nanoflakes assembled hydrangea-like Fe2O3@C@MoS2@C has been synthesized as anode material for lithium/sodium ion battery via hydrothermal method. In the as-prepared nanocomposite, Fe2O3 possesses a hollow ring structure with size of 80 nm and MoS2 shows the flower-like nanosheet morphology with thickness of 40 nm. When used as anode material for lithium ion battery, the nanocomposite shows excellent cycling stability and rate performance. It delivers a high reversible capacity of 1078 mAh g−1 after 200 cycles at a current density of 200 mA g−1, and a discharge capacity of 536.7 mAh g−1 even at a current density of 1000 mA g−1. Employed as anode materials for sodium ion batteries, it also provides an excellent reversible capacity of 498 mAh g−1after 200 cycles at a current density of 200 mA g−1. These excellent electrochemical performances can be attributed to the synergic effects of double carbon coating on the surface of Fe2O3 and MoS2, hollow ring of Fe2O3, and multi edge nanosheets of hydrangea-like MoS2. Double carbon layers can not only buffer huge volume change during Li/Na insertion/extraction process, but also enhance the electrical conductivity of Fe2O3 and MoS2. The multi-edged nanosheets of MoS2 are favorable for increasing Li/Na storage capacity of the nanocomposite. We believe that such nanocomposite of hollow rings of Fe2O3@C loaded with multi edged nanosheets of MoS2@C is a good candidate for high-performance lithium/sodium ion battery.

In this contribution, the well-developed, 3D vertically aligned graphene nanosheet arrays (VAGNAs) are prepared via a simple and environmentally friendly hydrothermal carbonization approach and subsequent KOH activation process by using biomass wastes (i.e., spruce bark) as the precursor for the first time. Ascribing to the combined superior inherent properties of graphene and the special structure configuration, the as-obtained 3D VAGNAs present unique features such as 3D interconnected structure, ultrahigh specific surface area (ca. 2385 m2/g), large volume of hierarchical pore volume (ca. 1.68 cm3/g), and easily accessible open surfaces of the graphene nanosheets. As the electrode material for supercapacitor, the 3D VAGNAs exhibit a high capacitance of 398 F g−1 at a current density of 0.5 A g−1 and an outstanding cycling stability (96.3% capacitance retention after 10,000 cycles) in 6.0 M KOH electrolyte. Moreover, in TEABF4/AN electrolyte, the VAGNA-900 based symmetric supercapacitor exhibits an outstanding capacitance of 239 F g−1 at 1 A g−1, and a high energy density of 74.4 W h kg−1 could be obtained at power density of 743.7 W kg−1. Such a remarkable electrochemical performance is highly desirable for supercapacitors to compete with other energy storage devices for real applications.

The synthesis and energy storage application of hierarchical porous carbons with size ranging from nano-to micrometres has attracted considerable attention all over the world. Exploring eco-friendly and reliable synthesis of hierarchical porous carbons for supercapacitors with high energy density and high power is still of ongoing challenge. In this work, we report the design and synthesis of super-hierarchical porous carbons with highly developed porosity by a stepwise removal strategy for high-rate supercapacitors. The mixed biomass wastes of coconut shell and sewage sludge are employed as raw material. The as-prepared super-hierarchical porous carbons present high surface areas (3003 m2 g−1), large pore volume (2.04 cm3 g−1), appropriate porosity, and outstanding electrochemical performance. The dependence of electrochemical performance on structural, textural, and functional properties of carbons engineered by various synthesis strategies is investigated in detail. Moreover, the as-assembled symmetrical supercapacitor exhibits high energy density of 25.4 Wh kg−1 at a power density of 225 W kg−1 and retains 20.7 Wh kg−1 even at a very high power of 9000 W kg−1. This work provides an environmentally benign strategy and new insights to efficiently regulate the porosity of hierarchical porous carbons derived from biomass wastes for energy storage applications.

Sustainable synthesis methods for the production of porous carbon with appropriate structural properties for use as supercapacitor electrodes are in high demand. Generally, activation is the most convenient and effective method to increase the surface area of carbon materials. However, the existing activation methods usually suffer from a low yield and low specific surface area; so the search for a new activation agent capable of preparing porous carbon with both a high yield and large surface area remains a great challenge. Here, a new and efficient activation agent copper chloride (CuCl2) is proposed for the production of porous carbon using rape pollen biomass as the carbon precursor. The advantages of using CuCl2 to fulfil synchronous carbonization and activation can be ascribed to the following features: (i) excellent ability to generate micropores in biomass; (ii) a high yield of porous carbon; (iii) low-destruction of the natural structure of the precursor; (iv) high retention of heteroatoms. The as-prepared rape pollen carbon (RPC) exhibits a porous structure with a large specific surface area (2488 m2 g−1), sphere-like structure and high heteroatom content. More importantly, the RPC exhibits a high yield of porous carbon of up to 37.6 wt% based on the raw rape pollen. Furthermore, the RPC electrode exhibits extremely high specific capacitance (390 F g−1 at 0.5 A g−1) and long cycling stability (retaining 92.9% after 10 000 cycles at 20 A g−1) in 6.0 M KOH aqueous electrolyte, and a high energy density of 26.8 W h kg−1 at a power density of 181.4 W kg−1 in 1.0 M Na2SO4 aqueous electrolyte. This method has universal significance in producing highly porous and high-performance carbons from biomass for various energy storage/conversion energy storage applications.

Carbon dot (CD)-based solid-state fluorescent materials have attracted a lot of attention in recent years owing to their superior optical and environmentally friendly properties, demonstrating a potential use in many applications. However, previously reported CD-based solid-state fluorescent materials mostly assemble a type of CD in the matrix which has only a single characteristic peak, and those of assembled double CDs with two characteristic peaks are very rare. Such a drawback restricts their further application, particularly in the field of white light emitting diodes (WLEDs). Herein, a rare type of double CD-based fluorescent material has been synthesized with dual characteristic peaks at 420 nm and 635 nm via the one-step assembly of blue- and red-emissive carbon dots (bCDs, rCDs) into mesoporous aluminas (MAs). The MA non-fluorescent matrix neither competes for absorbing excitation light nor absorbs the emission from the CDs, leading to excellent PL emitting properties and color and thermal stabilities. The emissive colors are tunable in the white-light region simply through adjusting excitation wavelengths, showing their great potential for phosphor-based WLEDs. In the field of agricultural planting, transparent sunlight conversion films based on co-assembled phosphors have been obtained, revealing inherent optical properties and an efficient process for converting sunlight into blue and red lights, which are essential for plant photosynthesis.

Development of efficient, low-cost and high-performance carbon materials as the electrodes is of significance for supercapacitors. Here we report a new class of hierarchical porous carbon with a three-dimensional network morphology of interconnected nanoparticle units prepared by using natural Indicalamus leaves and polytetrafluoroethylene as carbon precursor and silica-in-situ-remover, respectively. This protocol allows for successful post-treatment-free synthesis of biomass-based hierarchical porous carbon with specific surface area as high as 1801 m2/g without any extra activation process. Accordingly, when used as the electrodes of aqueous symmetrical supercapacitor, the as-prepared carbon material demonstrates superior capacitive behaviors, including high capacitances of 326 and 211 F/g in 1.0-V and 1.8-V supercapacitors, respectively, high energy density of 23.7 Wh/kg at power density of 224.5 W/kg, and excellent cycling stability. With these extremely attractive capacitive properties, this class of hierarchical porous carbon outperforms many typical state-of-the-art carbonaceous electrodes.

Hierarchically porous carbons are of increasing importance due to their special physicochemical properties. The state-of-the-art approaches for synthesizing hierarchical porous carbon with network structure normally suffer from specific chemistries, rigid reaction conditions, high cost, and multiple tedious steps that limit their large scale production. Herein, we present an interesting insight into the important role of Teflon additive in fabrication of hierarchical porous carbon derived from biomass and, thus, use natural Indicalamus leaves for the first time to successfully synthesize hierarchical porous carbon with a three-dimensional morphology of interconnected nanoparticle units by using a facile and post-treatment-free carbonization technique. It is surprisingly found that the addition of Teflon not only reduces the synthesis procedure by combining post-removal of silica and carbonization in a single step but also plays a decisive role in generating the hierarchical carbonaceous network structure ...

Development of facile and scalable synthesis process for the fabrication of nanoporous carbon materials with large specific surface areas, well-defined nanostructure, and high electrochemical activity is critical for the high performance energy storage applications. The key issue is the dedicated balance between the ultrahigh surface area and highly porous but interconnected nanostructure. Here, we demonstrate the fabrication of new sulfur doped nanoporous carbon sphere (S-NCS) with the ultrahigh surface area up to 3357 m 2 g −1 via a high-temperature hydrothermal carbonization and subsequent KOH activation process. The as-prepared S-NCS which integrates the advantages of ultrahigh porous structure, well-defined nanospherical and modification of heteroatom displays excellent electrochemical performance. The best performance is obtained on S-NCS prepared by the hydrothermal carbonization of sublimed sulfur and glucose, S-NCS-4, reaching a high specific capacitance (405 F g −1 at a current density of 0.5 A g −1 ) and outstanding cycle stability. Moreover, the symmetric supercapacitor is assembled by S-NCS-4 displays a superior energy density of 53.5 Wh kg −1 at the power density of 74.2 W kg −1 in 1.0 M LiPF 6 EC/DEC. The synthesis method is simple and scalable, providing a new route to prepare highly porous and heteroatom-doped nanoporous carbon spheres for high performance energy storage applications.

Interconnected 3 D nanosheet networks of reduced graphene oxide decorated with carbon dots (rGO/CDs) are successfully fabricated through a simple one-pot hydrothermal process. The as-prepared rGO/CDs present appropriate 3 D interconnectivity and abundant stable oxygen-containing functional groups, to which we can attribute the excellent electrochemical performance such as high specific capacitance, good rate capability, and great cycling stability. Employed as binder-free electrodes for supercapacitors, the resulting rGO/CDs exhibit excellent long-term cycling stability (ca. 92 % capacitance retention after 20 000 charge/discharge cycles at current density of 10 A g-1 ) as well as a maximum specific capacitance of about 308 F g-1 at current density of 0.5 A g-1 , which is much higher than that of rGO (200 F g-1 ) and CDs (2.2 F g-1 ). This work provides a promising strategy to fabricate graphene-based nanomaterials with greatly boosted electrochemical performances by decoration of with CDs.

An efficient self-crosslinking procedure to reasonably construct porous shells is reported for the synthesis of yolk–shell Au@microporous carbon nanospheres.

Two-dimensional carbon-based nanomaterials have demonstrated great promise as electrode materials for electrochemical energy storage. However, there is a trade-off relationship between energy storage and rate capability for carbon-based energy storage devices because of the incrementing ion diffusion limitations, especially for thick electrodes with high mass loading. Herein, we report the cross-linked microporous carbon nanosheets enabling high-energy and high-rate supercapacitors. The as-fabricated microporous carbon nanosheets exhibit an extraordinary thickness-independent electrochemical performance. With the thickness of 15 μm, the as-fabricated carbon nanosheet electrode possesses areal/volumetric/gravimetric capacitance of 895 mF cm

Carbon dots (CDs) profiting from their stable photoluminescence, small size and good biocompatibility have been used in higher organic fields. The relationship between CDs and edible fungi was less reported. Herein, blue emission CDs are prepared by one-step hydrothermal synthesis, and applied on oyster mushroom (Pleurotus ostreatus) for studying the relationship between CDs and mushroom. Laser scanning confocal imaging shows that the CDs could enter into mushroom hypha. The CDs also can transport among the sporophore. The CDs could be nutrition for oyster mushroom hypha growth in PDA-free medium, and the enhancement effect of CDs on edible fungi hypha is dose-response. Using high concentration on sporophore, their growth would not be affected. It shows that the sporophore of oyster mushroom has well toxicity tolerance for CDs. This study illustrates the relationship of uptake, translocation and toxicity of CDs on edible fungi, which lays the foundation for CDs further application on edible fungi system.

Silicon (Si)-based materials have emerged as promising anode materials owing to the theoretical capacity as high as 4200 mAh g−1 and satisfying working potential for lithium insertion. However, silicon-based anode materials inevitably face the dilemmas of huge volume variation and poor electric conductivity. In this study, three-dimensional (3D) hierarchically porous SiOx/C and carbon materials have been designed and fabricated from one renewable biomass precursor (i.e., bamboo shoot hulls) through low-temperature activated treatment and mildly aluminothermic reduction. The SiOx/C anode after pre-lithiation treatment achieves an initial discharge capacity of 1332 mAh g−1 and a high capacity of 1289 mAh g−1 after 400 cycles at 200 mA g−1 as anode electrode for half lithium-ion batteries (LIBs). When employed for full LIBs, the SiOx/C exhibits a specific capacity of 142 mAh g−1 at 0.1 C with prominent cyclic stability and exceptionally low volume expansion. Moreover, hierarchically porous carbons are also prepared from the same precursor through activation of CuCl2 and further removal of SiO2, exhibiting excellent electrochemical performances for lithium/sodium ion batteries.

The development of an effective route to high-performance carbonaceous electrode materials derived from low-cost biomass is critical but remains challenging for supercapacitors. Here we propose a new and cost-effective way to produce chitosan-based hierarchical porous carbons by the union of hydrothermal carbonization and chemical activation. The key to this preparation strategy is the utilization of acetic acid as an additive for hydrothermal carbonization, which not only favors the construction of a conducive environment for accessibility of activator KOH, but also leads to the formation of a rigid semi-carbonized framework substrate for generating an ultrahighly porous structure. Thus, our synthetic approach allows for a lower amount of activation agent and lower heating temperature when compared with normal chemical activation techniques, providing a more efficient way to produce ultrahigh-surface-area carbon materials. The as-prepared hierarchical porous carbon possesses a unique honeycomb-like framework and the highest BET surface area of 3532 m2 g−1 among all the carbon materials derived from chitosan. The combination of the hierarchical pore structure for rapid ion diffusion and the ultrahigh surface area for sufficient electrochemically active sites significantly improves the material's capacitive behaviors. An unusually high capacitance of 455 F g−1, an excellent cycling stability with 99% capacity retention over 20 000 cycles in KOH aqueous electrolyte, and a high energy density of 20.6 W h kg−1 at a power density of 226.8 W kg−1 in 1.8 V Na2SO4 aqueous supercapacitors have been obtained, demonstrating that the chitosan-based hierarchical porous carbons developed here are very attractive for application in supercapacitors.

Mesocrystals are advantageous in providing a large specific surface and favorable transport properties, and have been extensively studied for energy-related applications including supercapacitors, solar cells, lithium-ion batteries, and catalysis. However, the practical applications of mesocrystals are hindered by many obstacles, such as high cost, complicated synthesis processes, and utilization of deleterious additives. Herein, we report a facile one-step and additive-free route for the controllable synthesis of NiO mesocrystals (NOMs) with a cuboctahedral morphology and layered hierarchical structures consisting of self-assembled NiO nanosheets. When employed as an electrode material for supercapacitors, the as-prepared NOMs exhibited an exceptional electrochemical performance such as an ultrahigh reversible specific capacity of ca. 1039 F g−1 at a current density of 1.0 A g−1 and excellent cycling stability (ca. 93% capacitance retention after 10 000 charge/discharge cycles). Moreover, an all-solid-state hybrid supercapacitor based on hierarchical NOMs and three-dimensional nitrogen-doped graphene manifested a high energy density of 34.4 W h kg−1 at a power density of 150 W kg−1 in 2.0 M KOH aqueous electrolyte. These results further demonstrate the potential of NiO mesocrystals as a promising electrode material by constructing a hierarchical mesostructure, which can improve the electrochemical performance for energy storage. The outstanding electrochemical performance may be attributed to their hierarchical mesostructure that can effectively enhance the electrical conductivity and avoid the aggregation of NiO nanosheets, and the exposed {100} facets with a high electrochemical activity.

A simple and effective method is developed to synthesize bimetal oxide@graphitized carbon nanocomposites composed of graphitized carbons, Ni-Co oxides, and a small amount of Ni and Co metals (denoted as NC x O@G, where x represents Ni/Co mole ratio), by in-situ thermal decomposition of their corresponding coordination polymers. The resultant NC x O@G nanocomposites exhibit excellent electrochemical performance such as high specific capacity and good cycling stability. Experimental results demonstrate that the Ni/Co mole ratio plays an important role in determining the electrochemical behaviors, and a small amount of Ni and Co metals can boost the performance. A maximum specific capacity of ca. 673.5C g −1 at current density of 1.2 A g −1 , a superior capacity retention (∼105% after 10,000 cycles at 10 mV s −1 ), and a remarkable energy density of 46 Wh kg −1 with a high power density of 300 W kg −1 can be achieved when the Ni/Co ratio equals to ca. 1.0, signifying that this kind of nanocomposites are potential candidates for electrochemical energy storage.

Three dimensional nitrogen-doped graphene (3DNG) with high nitrogen content and improved electrochemical performance is successfully prepared by a facile, lost-cost hydrothermal method with ammonia as reducing-doping agent. The as-prepared 3DNG exhibits a hierarchical and interconnected porous network, which offers favorable pathways for electrolyte penetration and transportation. Remarkably, as binder-free electrode in aqueous electrolyte, the resultant 3DNG-2 with both high nitrogen content (7.71 at%) and large active material density (1.31 g cm−3) exhibits an ultrahigh volumetric capacitance of 437.5 F cm−3 (334.0 F g−1) at current density of 0.5 A g−1 and superior cycling stability (93% capacitance retention after 20 000 cycles at high current density of 10 A g−1). Further analyses indicate that the N-configurations are of great significance to the improvement of electrochemical behavior as well as the N-content. This work provides an effective way to synthesize 3DNG with excellent electrochemical properties for high performance supercapacitor and promotes the in-depth understanding of the enhancement mechanism of N-doping to supercapacitor performance.