Bagasse-derived hierarchical structured carbon (BDHSC) with tunable porosity and improved electrochemical performance is prepared via simple and efficient hydrothermal carbonization combined with KOH ...activation. Experimental results show that sewage sludge acts as a cheap and efficient structure-directing agent to regulate the morphology, adjust the porosity, and thus improve the supercapacitive performance of BDHSC. The as-resulted BDHSC exhibits an interconnected framework with high specific surface area (2296 m2 g−1), high pore volume (1.34 cm3 g−1), and hierarchical porosity, which offer a more favorable pathway for electrolyte penetration and transportation. Compared to the product obtained from bagasse without sewage sludge, the unique interconnected BDHSC exhibits enhanced supercapacitive performances such as higher specific capacitance (320 F g−1), and better rate capability (capacitance retention over 70.8% at a high current density of 50 A g−1). Moreover, the BDHSC-based symmetric supercapacitor delivers a maximum energy density of over 20 Wh kg−1 at 182 W kg−1 and presents an excellent long-term cycling stability. The developed approach in the present work can be useful not only in production of a variety of novel hierarchical structured carbon with promising applications in high-performance energy storage devices, but also in high-value utilization of biomass wastes and high-ash-content sewage sludge.
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•Bagasse-derived hierarchical structured carbon (BDHSC) was synthesized.•Sewage sludge was employed to regulate the morphology and porosity of BDHSC.•The BDHSC-based electrode exhibits excellent supercapacitive performance.
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.
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•Super-hierarchical porous carbons are prepared by a stepwise removal strategy.•Mixed biomass wastes of sewage sludge and coconut shell are used as raw material.•The resultant carbons show bright potential for high-performance supercapacitors.
A facile one-step pyrolysis route for the synthesis of hierarchically porous carbon nanosheets (PCNSs) derived from Moringa oleifera stems (MOSs) is reported, in which no post-activation-process in ...needed. The as-prepared PCNSs possesses unique porous nanosheet morphology with high specific surface area of ca. 2250 m2 g−1, large pore volume of ca. 2.3 cm3 g−1, appropriate porosity as well as heteroatom doping (N and O), endowing outstanding electrochemical properties as electrode material for high-performance supercapacitors. The PCNS-based electrodes are investigated in various aqueous electrolytes including 1.0 M Na2SO4, 1.0 M H2SO4, and 6.0 M KOH. The PCNSs exhibit a maximum specific capacitance of ca. 283 F g−1 (0.5 A g−1), excellent rate capability (ca. 72% of capacitance retention even at an ultrahigh current density of 50 A g−1), and a tremendous long-term cycling stability in the three-electrode system. Moreover, the as-assembled PCNS-based symmetric supercapacitor shows a high energy density of ca. 25.8 Wh kg−1 (in 1.0 M Na2SO4 electrolyte) and remarkable long-term cycling stability (almost no capacitance fade in aqueous electrolytes), indicating the promising of the as-prepared PCNSs for electrochemical energy storage and conversion.
A facile one-step pyrolysis strategy is designed to synthesize hierarchically porous carbon nanosheets (PCNSs) with unique two-dimensional nanosheet structure, high specific surface area, and outstanding electrochemical properties for high-performance electric double-layer capacitors. Display omitted
•Porous carbon nanosheets (PCNSs) are prepared by a facile one-step method.•No post-activation-process is needed for PCNS synthesis.•The PCNSs presents large surface area and abundant nitrogen content.•The PCNSs exhibit excellent electrochemical performance in aqueous electrolytes.
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 m 2 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 Na 2 SO 4 aqueous supercapacitors have been obtained, demonstrating that the chitosan-based hierarchical porous carbons developed here are very attractive for application in supercapacitors.
In this paper, we demonstrate that Moringa oleifera branches, a renewable biomass waste with abundant protein content, can be employed as novel precursor to synthesize three-dimensional ...heteroatom-doped and hierarchical egg-box-like carbons (HEBLCs) by a facile room-temperature pretreatment and direct pyrolysis process. The as-prepared HEBLCs possess unique egg-box-like frameworks, high surface area, and interconnected porosity as well as the doping of heteroatoms (oxygen and nitrogen), endowing its excellent electrochemical performances (superior capacity, high rate capability, and outstanding cycling stability). Therefore, the resultant HEBLC manifests a maximum specific capacitance of 355 F g–1 at current density of 0.5 A g–1 and remarkable rate performance. Moreover, 95% of capacitance retention of HEBLCs can be also achieved after 20 000 charge–discharge cycles at an extremely high current density (20 A g–1), indicating a prominent cycling stability. Furthermore, the as-assembled HEBLC//HEBLC symmetric supercapacitor displays a superior energy density of 20 Wh kg–1 in aqueous electrolyte and remarkable capacitance retention (95.6%) after 10 000 charge–discharge cycles. This work provides an environmentally friendly and reliable method to produce higher-valued carbon nanomaterials from renewable biomass wastes for energy storage applications.
Lithium alloying additions are verified to be an effective way to enhance the room temperature formability of magnesium. In this work, AZ31 (Mg–3wt% Al–1wt% Zn) alloys with different lithium ...additions (0–5wt%) were melted and extruded to 2mm thick sheets at 380°C. The microstructure and texture evolution were investigated by optical microscopy, X-ray diffraction (XRD) and electronic backscattered diffraction (EBSD). Tensile tests along three directions were carried out at room temperature, to access the mechanical properties and anisotropy. It was found that the mechanical anisotropy of the as-extruded AZ31 alloy was modified remarkably with lithium additions and AZ31 alloy with 5% Li content was found to have the smallest planar anisotropy and enhanced elongation. Lithium additions also increased the rotation of basal poles in the transverse direction, which was attributed to decreased c/a ratio and refined recrystallized structure. The thickness reduction and width reduction during tensile test were also measured and discussed.
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% capacitance retention after 10000 cycles in 1.0-V aqueous supercapacitors. A remarkably high energy density of 22.3 Wh kg–1 at a power density of 220.9 W kg–1 can be achieved in 1.8-V aqueous symmetrical supercapacitors. These very attractive electrochemical performances enable this highly porous carbon to go far beyond many previously reported carbonaceous electrodes, which presents a great potential for bridging the electrochemical performance gap between conventional nonaqueous and aqueous supercapacitors and opens up new avenues to high-value materials from waste bagasse.
In this work, we demonstrate for the first time that three-dimensional honeycomb-like hierarchically structured carbon (HSC) can be prepared by using high-ash-content sewage sludge as a carbon ...precursor. The fly-silicon process plays a crucial role in the formation of honeycomb-like hierarchical structures. The as-resulted HSC exhibits novel honeycomb-like frameworks, high specific surface area (2839 m super(2) g super(-1)), large pore volume (2.65 cm super(3) g super(-1)), interconnected hierarchical porosity, and excellent electrochemical performance. The high specific capacitance of 379 F g super(-1) as well as excellent rate capability and outstanding cycling stability (over 90% capacitance retention after 20 000 cycles even at a high current density of 20 A g super(-1)), makes it suitable for high-performance supercapacitor electrode materials. The assembled HSC//HSC symmetric supercapacitor presents enhanced supercapacitive behavior with a high energy density of 30.5 W h kg super(-1) in aqueous solution. This strategy provides an effective method to develop high-performance electrode materials derived from other high-ash-content biomass wastes for supercapacitors.
▶ This work has studied the microstructure and mechanical properties of the as-cast duplex Mg–7Li–
xY alloys with the Y content from 0
wt.% to 7
wt.%. ▶ The microstructure and mechanical properties ...of the T4 and T6 heat-treated duplex Mg–7Li–1Y and Mg–7Li–7Y alloys were also studied. ▶ The solubility of Y element in the Li-based phase has been studied.
Mg–7Li–
xY (
x
=
0–7
wt.%) alloys were prepared by permanent mould casting method, and the microstructure and mechanical properties of the alloys were investigated. The results show that α-Mg and β-Li phases exist in all alloys. The Y-enriched α-Mg phase distributes along the edge of α-Mg phase and in the β matrix of
x
=
1–7 alloys, and Mg
24Y
5 mainly disperses in the β matrix of
x
=
3–7 alloys. The strength of the alloy is enhanced by adding Y element, and the elongation is improved with the Y content no more than 3
wt.%. The as-cast Mg–7Li–3Y alloy exhibits an optimum combination of mechanical properties with the ultimate tensile strength, yield strength and elongation of 160
MPa, 144
MPa and 22%, respectively. After solutionized at 400
°C for 3
h with a subsequent aging at 100
°C, Mg–7Li–7Y alloy exhibits high ultimate tensile strength and yield strength, which are improved to 120% and 152% compared with those of the as-cast Mg–7Li alloy, respectively.
Typical porous carbons were obtained from waster biomass, melaleuca bark activated by potassium hydroxide (KOH), and characterized by XRD, SEM, TEM, FTIR, XPS and N2-sorption. The different samples ...with tunable morphologies and texture were prepared by controlling synthesis reaction parameters. The resulting samples demonstrate both high surface area (up to 3170 m2 g−1) and large hydrogen storage capacity (4.08 wt% at 77 K and 10 bar), implying their great potential as hydrogen storage materials.
•The porous carbon with highest surface area of 3170 m2 g−1 was prepared from melaleuca bark.•The micropore volume and small mesopore volume (V2–3 nm value) were more important than other parameters for H2 uptakes at 77 K.•The resultant carbon with high surface area showed H2 uptake exceeding 4 wt% at 77 K, 10 bar.•The desorption isotherm and cycle life test of H2 uptake indicated that it was a totally reversible physical sorption.
