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Abstract A facile hydrothermal polymerization method has been developed for the preparation of monodisperse carbon spheres (MCSs) using the triblock copolymer F108 as surfactant. The synthesis is based on the ammonia-catalyzed polymerization reaction between phenol and formaldehyde (PF). The resultant MCSs have a perfect spherical morphology, smooth surface, and high dispersity. The particle sizes can be tuned in a wide range of 500~2400 nm by adjusting the dosage of the PF precursor. The activated MCSs with suitable heteroatoms (N and O) doped and a large specific surface area (960 m2 g−1) were obtained. A high-performance electrode of electrical double-layer capacitors fabricated by those active material have an excellent specific capacitance (310 F g−1 at 0.5 A g−1) and outstanding cycling stability (92% capacitance retention after 10,000 cycles). This work provides a new opportunity for the fabrication of MCSs with potential applications.

Abstract Nitrogen-doped microporous carbon spheres (NMCSs) are successfully prepared via carbonization and KOH activation of phenol-formaldehyde resin polymer spheres synthesized by a facile and time-saving one-step hydrothermal strategy using triblock copolymer Pluronic F108 as a soft template under the Stöber-like method condition. The influence of the ethanol/water volume ratios and carbonation temperatures on the morphologies, pore structures and electrochemical performances of the prepared NMCSs are investigated systematically. The optimal NMCSs have a large specific surface area of 1517 m2 g− 1 with a pore volume of 0.8 cm3 g− 1. The X-ray photo-electron spectroscopy analysis reveals a suitable nitrogen-doped content of 2.6 at.%. The as-prepared NMCSs used as supercapacitor electrode materials exhibit an outstanding specific capacitance of 416 F g− 1 at a current density of 0.2 A g− 1, also it shows an excellent charge/discharge cycling stability with 96.9% capacitance retention after 10,000 cycles. The constructed symmetric supercapacitors using PVA/KOH as the gel electrolyte can deliver a specific capacitance of 60.6 F g− 1 at current density of 1 A g− 1. A maximum energy density of 21.5 Wh kg− 1 can be achieved at a power density of 800 W kg− 1, and the energy density still maintains 13.3 Wh kg− 1 even at a high power density of 16 kW kg− 1. The results suggest that this work can open up a facile and effective way to synthesize the NMCSs for electrode materials of high performance energy storage devices.

Abstract The aqueous sodium-ion battery (ASIB) is one of the promising new energy storage systems owing to the abundant resources of sodium as well as efficiency and safety of electrolyte. Herein, we report an ASIB system with Na4Mn9O18/carbon nanotube (NMO/CNT) as cathode, metal Zn as anode and a novel Na+/Zn2+ mixed ion as electrolyte. The NMO/CNT with microspherical structure is prepared by a simple spray-drying method. The prepared battery delivers a high reversible specific capacity and stable cyclability. Furthermore, the battery displays a stable reversible discharge capacity of 53.2 mAh g−1 even at a high current rate of 4 C after 150 cycles. Our results confirm that the NMO/CNT composite is a promising electrode cathode material for ASIBs.

Abstract Carbon nanospheres with distinguishable microstructure were prepared by carbonization and subsequent KOH activation of F108/resorcinol-formaldehyde composites. The dosage of triblock copolymer Pluronic F108 is crucial to the microstructure differences. With the adding of F108, the polydisperse carbon nanospheres (PCNS) with microporous structure, monodisperse carbon nanospheres (MCNS) with hierarchical porous structure, and agglomerated carbon nanospheres (ACNS) were obtained. Their microstructure and capacitance properties were carefully compared. As a result of the synergetic effect of mono-dispersion spheres and hierarchical porous structures, the MCNS sample shows improved electrochemical performance, i.e., the highest specific capacitance of 224 F g−1 (0.2 A g−1), the best rate capability (73% retention at 20 A g−1), and the most excellent capacitance retention of 93% over 10,000 cycles, making it to be the promising electrode material for high-performance supercapacitors.

Abstract High quality and naturally continuous structure of three-dimensional graphene network (3DGN) endow it a promising candidate to modify TiO2. Although the resulting composite photocatalysts display outstanding performances, the lacking of active sites of the 3DGN not only goes against a close contact between the graphene basal plane and TiO2 nanoparticles (weaken electron transport ability) but also limits the efficient adsorption of pollutant molecules. Similar with surface functional groups of the reduced graphene oxide (RGO) nanosheets, surface defects of the 3DGN can act as the adsorption sites. However, the defect density of the 3DGN is difficult to control (a strict cool rate of substrate and a strict flow of precursor gas are necessary) because of its growth approach (chemical vapor deposition method). In this study, to give full play to the functions of graphene, the RGO nanosheets and 3DGN co-modified TiO2 composite photocatalysts are prepared. After optimizing the mass fraction of the RGO nanosheets in the composite photocatalyst, the resulting chemical adsorption ability and yields of strong oxidizing free radicals increase significantly, indicating the synergy of the RGO nanosheets and 3DGN.

The aqueous sodium-ion battery (ASIB) is one of the promising new energy storage systems owing to the abundant resources of sodium as well as efficiency and safety of electrolyte. Herein, we report an ASIB system with NaMnO/carbon nanotube (NMO/CNT) as cathode, metal Zn as anode and a novel Na/Zn mixed ion as electrolyte. The NMO/CNT with microspherical structure is prepared by a simple spray-drying method. The prepared battery delivers a high reversible specific capacity and stable cyclability. Furthermore, the battery displays a stable reversible discharge capacity of 53.2 mAh g even at a high current rate of 4 C after 150 cycles. Our results confirm that the NMO/CNT composite is a promising electrode cathode material for ASIBs. [ABSTRACT FROM AUTHOR]

Carbon nanospheres with distinguishable microstructure were prepared by carbonization and subsequent KOH activation of F108/resorcinol-formaldehyde composites. The dosage of triblock copolymer Pluronic F108 is crucial to the microstructure differences. With the adding of F108, the polydisperse carbon nanospheres (PCNS) with microporous structure, monodisperse carbon nanospheres (MCNS) with hierarchical porous structure, and agglomerated carbon nanospheres (ACNS) were obtained. Their microstructure and capacitance properties were carefully compared. As a result of the synergetic effect of mono-dispersion spheres and hierarchical porous structures, the MCNS sample shows improved electrochemical performance, i.e., the highest specific capacitance of 224 F g (0.2 A g), the best rate capability (73% retention at 20 A g), and the most excellent capacitance retention of 93% over 10,000 cycles, making it to be the promising electrode material for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

The aqueous sodium-ion battery (ASIB) is one of the promising new energy storage systems owing to the abundant resources of sodium as well as efficiency and safety of electrolyte. Herein, we report an ASIB system with Na 4 Mn 9 O 18 /carbon nanotube (NMO/CNT) as cathode, metal Zn as anode and a novel Na + /Zn 2+ mixed ion as electrolyte. The NMO/CNT with microspherical structure is prepared by a simple spray-drying method. The prepared battery delivers a high reversible specific capacity and stable cyclability. Furthermore, the battery displays a stable reversible discharge capacity of 53.2 mAh g -1 even at a high current rate of 4 C after 150 cycles. Our results confirm that the NMO/CNT composite is a promising electrode cathode material for ASIBs.