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The poor reversibility of the zinc (Zn) anodes and the irreversible deposition/dissolution of Mn2+/MnO2 significantly impede the commercialization of Zn-Mn aqueous batteries (ZMABs). In reducing the difference between the desired interfacial reaction environments of the cathode and anode, we found that they face the same problem of interference-the generation of irreversible corrosion products. Herein, we have introduced a novel self-regulatory mechanism. This mechanism involves the addition of sodium dihydrogen phosphate, which shifts from passive protection to active regulation. It effectively captures OH- ions, prevents corrosion product formation, and facilitates the in situ generation of a solid electrolyte interface (SEI) film. This modification also homogenizes Zn ion flow and improves the reversibility of Zn plating and stripping. Furthermore, a stable and slightly acidic environment has been established to stabilize the pH at the cathodic interface, mitigate corrosion product formation, and enhance the reversible deposition and dissolution of Mn2+/MnO2. With the optimal electrolyte, ZnâZn symmetric cells demonstrate stable operation for over 3000 hours at 1 mA cm-2, 1 mA h cm-2. Additionally, the ZnâCu cells maintain high reversibility after 1000 cycles, achieving an average coulombic efficiency (CE) of 99.76%. The assembled ZnâMnO2 full cells exhibit exceptional cycling stability and rate performance. This work adopts the approach of seeking common ground and emphasizing the balance of cathode and anode interfacial requirements, which represents a new and significant insight for design of ZMABs with high reversibility and high cyclability.
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Studying the hydrogen bonding structure of H2O at the metal-water interface is a highly complex yet fascinating endeavor. The intricate interactions and diverse orientations of water molecules on metal surfaces with varying potentials pose a significant challenge in elucidating the coupling between O-H stretching and H-O-H bending modes. In this study, we employed DFT-MD simulation to explore how the orientation of interfacial water molecules changes with the applied potential on the Au(111) surface. Based on the surface-specific velocity-velocity correlation function (ssVVCF) formula, we calculated vibrational sum frequency generation (VSFG) spectra for the O-H stretches. We found that three assigned peaks (â¼3300, â¼3450, and 3650 cm-1) shifted toward lower frequencies as the potential moved toward more negative values. Our results align remarkably well with experimental Raman spectroscopy data. Notably, our VSFG analysis revealed a significant change in the VSFG spectra of the hydrogen-bonded O-H groups (â¼3300 cm-1), switching from a negative to a positive sign with decreasing potential. This alteration suggests a substantial change in the orientation of these low-frequency O-H groups owing to their increased interactions with the Au surface. In contrast, the orientations of both the high-frequency O-H groups (â¼3450 cm-1) and the dangling O-H groups (â¼3650 cm-1) remained unaffected by the applied potentials. Furthermore, our analysis of the decomposed vibrational density of states (VDOS) for the H-O-H bending mode uncovered the coupling between the H-O-H bending and O-H stretching vibrations, known as the Fermi resonance. Our work suggests that the H-O-H bending vibration becomes restricted when water molecules transition from the â³one-H-downâ³ to the â³two-H-downâ³ conformation, leading to a redshift in the O-H stretching vibration through the Fermi resonance. By constructing the VSFG and decomposed VDOS spectra, we gained valuable insights into the structural changes that Raman spectra alone cannot fully interpret. Specifically, our analysis revealed the critical role of the Fermi resonance effect in shaping the spectroscopic signature of interfacial water molecules on the Au(111) surface.
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Siderophores secreted by microorganisms can promote ecological efficiency and could be used to regulate the unbalanced microbial community structure. The influence of the siderophore activity of Trichoderma yunnanense strain 2-14F2 and Beauveria pseudobassiana strain (2-8F2) on the physiological/biochemical functions and community structure of soil microbes affected by tobacco bacterial wilt (TBW) was studied. DNS Colorimetry and Biolog-eco plates were used to quantify the impacts of strain siderophores on soil enzyme activities and microbial metabolism. Based on Illumina MiSeq high-throughput sequencing, the soil 16S rDNA and ITS sequences were amplified to dissect the response characteristics of alpha/beta diversity and the structure/composition of a soil microbial community toward siderophores. The KEGG database was used to perform the PICRUSt functional prediction of the microbial community. We found that siderophores of 2-14F2 and 2-8F2, at certain concentrations, significantly increased the activities of sucrase (S-SC) and urease (S-UE) in the TBW soil and enhanced the average well color development (AWCD, carbon source utilization capacity) of the microbial community. The metabolic capacity of the diseased soil to amino acids, carbohydrates, polymers, aromatics, and carboxylic acids also increased significantly. The response of the bacterial community to siderophore active metabolites was more significant in alpha diversity, while the beta diversity of the fungal community responded more positively to siderophores. The relative abundance of Actinobacteria, Chloroflexi, and Acidobacteria increased and was accompanied by reductions in Proteobacteria and Firmicutes. LEfSe analysis showed that Pseudonocardiaceae, Gemmatimonas, Castellaniella, Chloridiumand and Acrophialophora altered the most under different concentrations of siderophore active metabolites. The PICRUSt functional prediction results showed that siderophore increased the abundance of the redox-related enzymes of the microbial community in TBW soil. The BugBase phenotypic prediction results showed that the siderophore activity could decrease the abundance of pathogenic bacteria. The study concludes that siderophore activity could decrease the abundance of pathogenic bacteria and regulate the composition of the microbial community in TBW soil. The activities of sucrase (S-SC) and urease (S-UE) in TBW soil were significantly increased. Overall, the siderophore regulation of community structures is a sustainable management strategy for soil ecosystems.
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Ni(OH)2 nanosheet, acting as a potential active material for supercapacitors, commonly suffers from sluggish reaction kinetics and low intrinsic conductivity, which results in suboptimal energy density and long cycle life. Herein, a convenient electrochemical halogen functionalization strategy is applied for the preparation of mono/bihalogen engineered Ni(OH)2 electrode materials. The theoretical calculations and experimental results found that thanks to the extraordinarily high electronegativity, optimal reversibility, electronic conductivity, and reaction kinetics could be achieved through F functionalization . However, benefiting from the largest ionic radius, INi(OH)2 contributes the best specific capacity and morphology transformation, which is a new finding that distinguishes it from previous reports in the literature. The exploration of the interaction effect of halogens (F, INi(OH)2 , F, BrNi(OH)2 , and Cl, INi(OH)2 ) manifests that F, INi(OH)2 delivers a higher specific capacity of 200.6 mAh g-1 and an excellent rate capability of 58.2% due to the weaker electrostatic repulsion, abundant defect structure, and large layer spacing. Moreover, the F, INi(OH)2 //FeOOH@NrGO device achieves a high energy density of 97.4 Wh kg-1 and an extremely high power density of 32426.7 W kg-1 , as well as good cycling stability. This work develops a pioneering tactic for designing energy storage materials to meet various demands.
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As the most widely used method for preparing graphene oxide (GO), Hummers' method always involves a key step, that is adding water to concentrated sulfuric acid. We found that if this process is cancelled, the oxidation degree of GO will be significantly reduced. This means that the heat released during concentrated sulfuric acid dilution will promote further oxidation of GO. In this paper, we fully utilize the heat released during concentrated sulfuric acid dilution to develop a new non-heat-source process without any low-/high-temperature auxiliar, exponentially reducing the energy consumption and largely avoiding the frequent temperature control. The result shows that GO prepared by Hummers' method and that prepared by the proposed process show a similar structure, composition, morphology, and defect degree. Meanwhile, the corresponding reduced GO (rGO) obtained after reduction shows similar capacitive behavior. Their specific capacitances are 243.6 F g-1 and 240.3 F g-1 at 1 A g-1, respectively, and they both have a long-term cycling performance (with a 100% capacitance retention after 10 000 cycles at 30 A g-1). This study provides a new strategy for the preparation of GO with low energy consumption.
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Transition metal sulfides have become more and more important in the field of energy storage due to their superior chemical and physical properties. Herein, dahlia ß-NiS with a rough surface and ß-NiS@reduced graphene oxide (rGO) have been green synthesized by a one-step hydrothermal method. The interface characteristics of ß-NiS@ rGO composites have been systematically studied by XPS, Raman, and first-principles calculations. It is found that the residual O atoms in the interface and the polarization charge generated by them play an important role in performance enhancement. The NiS@rGO composite material has the best electrochemical performance when the C/O ratio is 6.48. Furthermore, we designed a NiS@rGO//rGO asymmetric supercapacitor with a potential window of 1.7 V. Its excellent energy density and power density demonstrate the advantages of the optimized NiS@rGO electrode. When the power density is 850 W kg-1, the energy density can reach 40.4 W h kg-1. Even at a power density of up to 6800 W kg-1, the energy density can be maintained at 17.6 W h kg-1. These encouraging results provide a possible pathway for designing asymmetric supercapacitors with ultra-high performance and a feasible strategy for the precise control of electrochemical performance.
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The lack of electrical conductivity limits the electrochemical kinetic rate of the electrode material, resulting in the inability to reach its theoretical capacity. A facile method is adopted to improve the intrinsic conductivity of binary NiS2/Ni3S4 hybrid nickel sulfide, with the doping of transition metal atoms Co, Mn and Ag. Through the introduction of heteroatoms, the electronic structure of the electrode material is modified and the electrical conductivity is significantly improved, thus enhancing its electrochemical performance. The improvement of conductivity is attributed to the formation of intermediate bands of transition metals and the redistribution of electrons, and the result is demonstrated by experimental and density functional theory (DFT) calculations. As a result, the NiS2/Ni3S4 hybrid nickel sulfide after 0.5% amount of Co-doping reaches the highest specific capacitance of 2874 F g-1 at 1 A g-1, increasing specific capacitance of 653 F g-1 as 29.4% of the specific capacitance of non-doped nickel sulfide. The Co doped nickel sulfide also exhibits remarkable cycling stability compared with non-doped nickel sulfide. The assembled 2% Co-doped nickel sulfide//rGO, 0.5% Mn-doped nickel sulfide//rGO and 0.5% Ag-doped nickel sulfide//rGO asymmetric supercapacitors show a specific energy density of 36.6, 36.1 and 36.0 W h kg-1 at a power density of 800 W kg-1. This study provides a useful insight into the fabrication of high performance pseudocapacitive materials.
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Focusing on the synthesis of nickel-based materials (such as nickel sulfides, nickel hydroxides, and nickel oxides) is an urgent need in the fields of batteries, supercapacitors, and catalysis. However, their controlled synthesis still remains a great challenge because of the inadequate understanding of the control factor of their synthesis. A two-step solvo-/hydrothermal process with halide ion embedding/releasing was proposed to understand the effect of the halide ions on the synthesis and sulfidation of nickel hydroxy-halides. We find that the halide ions determine the formation, growth, and evolution of nickel hydroxy halides and promote them to form unique architectures and morphologies, leading to obvious differences in structural characteristics, including conductivity and electrochemical activity. Because of the presence of halide ions, a series of hybrids with multiple interfaces, which consist of hydroxides and sulfides and have various morphologies, such as flower-like balls, solid balls, porous balls, schistose, and thorny balls, with capacities ranging from 100.7 to 261.2 mA h g-1, can be easily obtained. It is fully demonstrated that the halide anion plays a core role in the synthesis process of nickel-based materials, and this finding will provide more chances for controllably synthesizing high-activity electrode materials.
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Directly anchoring active materials on porous conductive substrates is considered an effective strategy to obtain a high-activity electrode since the direct contact between active materials and substrates benefits charge transfer, and the presence of porous structures provides more active sites. However, due to the presence of strong stress and weak adhesion, active materials loaded on the substrate are very easy to peel off during assembly and use, which can greatly shorten the lifetime of use. Herein, an ultrasonic corrosion strategy is proposed to regulate the surface of a metal substrate. We find that ultrasonic oxygen corrosion and interfacial water control play key roles in fabricating the complex electrode, which can help the surface of Cu foam to form special lamellar cross-linked CuO nanoarchitectures with strong adhesion and then overcome the defect of the deposited NiCo layered double hydroxides (NC LDH) on the stress and adhesion. The expected electrode shows more than 70% improvement in cycling stability at an ultra-high current density of 20 A g-1, relative to the active material layer of the electrode with strong stress and weak adhesion. Meanwhile, benefiting from its lamellar cross-linked nanoarchitectures having large specific surface area and many nano-pores, it presents a high specific capacitance of 3010.8F g-1 at 1 A g-1 and a good rate capability of 59.3% at 50 A g-1. It is foreseen that this finding provides a novel, universal strategy for managing the surface and interface of the metal substrate, thereby obtaining a reliable, stable electrode.
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The property of an active material is not only influenced by its morphology and size, but also by its crystal phase. The present phase regulation of nickel sulfide is mainly achieved by controlling the participation of sulfur source in reaction. Thus, new perspectives direct at phase control need to be explored and supplemented. Herein, we proposed a novel coordination agent-dominated phase modulation strategy assisted by a hydrothermal process. It is found that increasing the amount of coordination agent can drove the phase transformation from the initial composite of ß-NiS/α-NiS/Ni3S4 to ß-NiS/α-NiS, and then to pure ß-NiS. The mechanism of phase regulation has been proposed, and the general application of this method has been demonstrated. By employing coordination agent, the size of resulted products is reduced, and the morphology is optimized. As a result, all of the pure ß-NiS electrodes indicate significantly enhanced specific capacity than the pristine ß-NiS/α-NiS/Ni3S4 composite. Notably, the sample synthesized with 3 mmol of urea (S11) shows uniform morphology and smallest size, and it gives a highest specific capacity of 223.8 mAh g-1 at 1 A g-1, almost 1.5 times of the original sample. The fabricated S11//rGO device delivers a high energy density of 56.6 Wh·kg-1 at a power density of 407.5 W·kg-1, and keeps an impressive capacity retention of 84% after 20,000 cycles. This work put forwards a new prospect for controlling the phase and composition of nickel sulfide based on coordination chemistry.
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BACKGROUND: MicroRNAs (miRs) have been shown to be closely associated with the occurrence and development of tumors and to have potential as diagnostic and therapeutic targets. The detection of miRs by noninvasive imaging technology is crucial for deeply understanding their biological functions. Our aim was to develop a novel miR-21-responsive gene reporter system for magnetic resonance imaging (MRI) visualization of the miR-21 dynamics in neuroblastoma. METHODS: The reporter gene ferritin heavy chain (FTH1) was modified by the addition of 3 copies of the sequence completely complementary to miR-21 (3xC_miR-21) to its 3'-untranslated region (3' UTR) and transduced into SK-N-SH cells to obtain SK-N-SH/FTH1-3xC_miR-21 cells. Then, the antagomiR-21 was delivered into cells by graphene oxide functionalized with polyethylene glycol and dendrimer. Before and after antagomiR-21 delivery, FTH1 expression, MRI contrast and intracellular iron uptake were assayed in vitro and in vivo. RESULTS: In the SK-N-SH/FTH1-3xC_miR-21 cells, FTH1 expression was in an "off" state due to the combination of intratumoral miR-21 with the 3' UTR of the reporter gene. AntagomiR-21 delivered into the cells bound to miR-21 and thereby released it from the 3' UTR of the reporter gene, thus "switching on" FTH1 expression in a dose-dependent manner. This phenomenon resulted in intracellular iron accumulation and allowed MRI detection in vitro and in vivo. CONCLUSION: MRI based on the miR-21-responsive gene reporter may be a potential method for visualization of the endogenous miR-21 activity in neuroblastoma and its response to gene therapy.
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While significant advances have been made in the synthesis of core-/multi-shell materials, the synthetic process usually involves a soft/hard template and complicated procedures. In particular, it is extremely difficult to fabricate single-component core-shell structures for nickel sulfides (NSs) with a controlled phase. In this work, we demonstrate a novel facile method to synthesize a single-component ß-NiS ball-in-ball microsphere. The ball-in-ball structure is easily obtained by uniquely employing 2-mercaptopropionic acid (2-MPA) as the sulfur source and ethanol as the solvent based on the Ostwald ripening process. In particular, our work demonstrates that the chemical structure of sulfur sources and solvents plays a key role in the formation of the pure ß-NiS ball-in-ball structure. When used as an electrode active material, the ß-NiS ball-in-ball microspheres exhibit two times stronger specific capacity and three times higher rate performance than NSs produced by a hydrothermal method. The fabricated NS-2//rGO asymmetrical supercapacitor (ASC) displays an energy density of 46.4 W h kg-1 at a power density of 799.0 W kg-1 and good cycling performance. Thus, this study provides a new method for controlling the phase and morphology of NSs.
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The research studies on the adsorption of surfactants on graphene help us to know how to use surfactants to exfoliate graphene from graphite or functionalize the graphene surface. Among them, molecular dynamics (MD) simulation has been widely used to investigate the adsorption of organic molecules and surfactants on graphene. In particular, coarse-grained (CG) MD simulation greatly improves the computational efficiency by simplifying the complexity of the studied systems, allowing us to explore the structure and dynamics of complex systems on larger spatial scales and longer time scales. However, an accurate prediction of the adsorption of surfactants on graphene is required by optimizing the interaction between surfactants and graphene, which is often overlooked by some CG models. In this work, we found that an accurate prediction of the adsorption enthalpies of organic molecules on graphene can be achieved by optimizing the interactions between organic molecules and benzene. Meanwhile, we simulated the adsorption of a surfactant on single-layer and double-layer graphene nanosheets, respectively. Our results revealed that increasing the temperature would favor the interactions between hydrophilic groups of surfactants. In addition, we discovered that the surfactant prefers to be adsorbed on the inner surfaces of double-layer graphene compared with the outer surfaces, and this is owing to the dehydration in the middle of double-layer graphene, which is beneficial to the hydrophilic interactions between surfactant molecules inside the double-layer graphene.
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Nickel sulfide possesses ultra-high theoretical energy storage capacity. Though it is easily obtained, it is very difficult to exert its intrinsic strong capacity. In this work, a new strategy based on a binary synergy of sulfur sources is introduced. By regulating the molar ratio of two sulfur sources, a high-performance α-NiS/Ni3S4 binary hybrid is successfully synthesized. Interestingly, it is found that changing the molar ratio of two sulfur sources in hydrothermal process can efficiently regulate the components of product but cannot visibly affect its morphology. The electrochemical results indicate that this strategy is highly effective for improving the performance of nickel sulfide. As a result, a highest specific capacity of 214.9 mAh g-1 at 2 A g-1 was reached. In addition, the fabricated S3//rGO hybrid supercapacitor displays a highest energy density of 41.9 Wh kg-1 at a power density of 799.0 kW kg-1. Moreover, the device delivers an excellent cycle stability with 103% capacity retention rate after 10,000 cycles. These findings open a new avenue for the controlled synthesis of high-performance nickel sulfides or other metal sulfides.
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Metal metaphosphates, particularly those with core-shell structure, have showed extraordinary potential in energy storage field due to their superior chemical and physical properties. However, the core-shell metal metaphosphates with high energy density in supercapacitor application is rarely reported. Here, the core-shell structured Ni(OH)2/Ni(PO3)2 (NNP) hybrid electrode were prepared by one-step electrodeposition, which exhibits a superior specific capacitance of 1477 F g-1 at a current density of 1 A g-1. Furthermore, an aqueous asymmetric supercapacitor (ASC) based on NNP hybrid composite as cathode and reduced graphene oxide (rGO) as anode is assembled successfully to deliver a prominent energy density of 67 Wh kg-1 at 775 W kg-1 and splendid stability with capacitance retention of 81% after 8000 cycles. The outstanding electrochemical capabilities are attributed to the porous nanoflake and hierarchical core-shell structure of NNP hybrid composite, which can accelerate ion diffusion and charge transfer in redox reaction. These results indicate that nanohybrid NNP material has promise to be an advanced energy storage material.
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In this work, atomistic molecular dynamics (MD) simulations of palmitoyl-oleoyl-phosphatidylcholine (POPC) bilayer were carried out to investigate the effect of water models on membrane dipole potential, which is primarily associated with the preferential orientation of molecular dipoles at the membrane-water interface. We discovered that the overestimation of the dipole potential by the TIPS3P water model can be effectively reduced by the TIP4P water model. On the one hand, the TIP4P water model decreases the negative contribution of lipid to the dipole potential through influencing the orientation of lipid headgroups. On the other hand, the TIP4P water model reduces the positive contribution of water to the dipole potential by increasing the preference of H-down orientation (the water dipole orients toward the bilayer center). Interestingly, the TIP4P water model affects the orientation of interfacial water molecules more obviously than that of lipid headgroups, leading to the decrease in the dipole potential. Furthermore, the MD results revealed that the water close to the positively charged choline (namely, N-associated water) prefers the H-down orientation while the water around the negatively charged phosphate (namely, P-associated water) favors the H-up orientation, in support of recent experimental and MD studies. However, interfacial water molecules are more strongly influenced by the phosphate groups than by the choline groups, resulting in the net H-up orientation (the water dipole orients toward the bilayer center) in the region of lipid headgroups. In addition, it is intriguing that the preference of H-up orientation decreases when water molecules penetrate more deeply into the lipid bilayer. This is attributed to the counteracting effect of lipid carbonyl groups, and the effect varies with the lipid chains (oleoyl and palmitoyl chains), suggesting the important role of lipid carbonyl groups.
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Advanced aqueous batteries with abundant global reserves, large discharge capacity and long life span are crucial research objectives. Herein, a kind of aqueous Zn-ion battery was fabricated with ultra-thin Ni-Mn nanosheet electrode and zinc foil. A simple H2-annealing process was employed to handle the NiMnxOy nanosheets to form oxygen vacancy. Based on the formation of fast ion diffusion channels and the increase of active sites, the fabricated H-NiMnxOy nanosheet electrode displays an areal capacity of 0.68 mA h cm-2 at a current density of 2 mA cm-2 and an excellent cycling performance (almost no reduction after 6000 cycles). The fabricated H-NiMnxOy//Zn battery obtains a high areal capacity, up to 0.66 mA h cm-2 at a current density of 4 mA cm-2, and shows a long cycling stability (88.5% capacity retention after 5500 cycles). In particular, it has a high energy density, up to 1.13 mW cm-2 at a power density of 3.34 mW cm-2, more than many other similar devices. Thus, this research provides a new idea for the wide application of aqueous Zn-ion battery in intelligent equipment and electric vehicles.
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Here we report an ultra-effective and reliable pathway to reduce GO into graphene by an about 4 seconds flame-assisted microwave process. A holey graphene with a C/O atom ratio of 31.1, a pore volume of 6.0 cm3 g-1, and a specific surface area of 1050.0 m2 g-1 was synthesized.
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Redox methods represented by Hummers' method are the most frequently-used pathways to prepare graphene, but to date still very low-efficient, because of its time-consuming washing and hard reduction process. Here we report an intermittent microwave-exfoliated non-expansive graphite oxide (GtO) process to prepare a wrinkled graphene with a high reduction degree (C/O: 19.0), a high defect degree, and a high specific surface area (1333.7 m2 g-1). Findings show that the non-expansive GtO without water washing indicates an almost 100% exfoliated success rate during this intermittent microwave process. The obtained graphene shows easy dispersity in organic solvents, and excellent supercapacitor performance in specific capacitance, rate capacity, and especially in cycling lifetime with no decay after 80,000 cycles at 30 A g-1. Consequently, this special microwave process successfully solves the problems of tedious washing and hard reduction in redox methods, thus exponentially boosting the efficiency of preparing graphene.
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Ni3S4 is regarded as one of the promising electrode materials for energy storage, but the difficulty in obtaining its pure phase hinders its wide applications. In this work, we introduced a novel method to in-situ synthesize Ni3S4@reduced graphene oxide (rGO) composite, where graphene oxide (GO) was found to induce the oxidation of Ni2+ to Ni3+ and the morphology transformation from microbar to polyhedron during the hydrothermal process. The influence of the content and oxidation degree of GO on the phase composition and morphology of nickel sulfide is investigated. It is found that the oxygen-containing functional group of GO is responsible for the change of valence state, which thus drives the transformation of NiS/Ni3S4 towards Ni3S4. The obtained Ni3S4@rGO composite shows a high energy storage capacity (1830 F g-1 at 2 A g-1), remarkably higher than the unpurified phase NiS/Ni3S4 (830 F g-1). Correspondingly, the assembled asymmetry supercapacitor indicates a high energy density of 37.3 Wh kg-1 at a power density of 398â¯Wâ¯kg-1. More importantly, the capacitance retention reaches 91.4 % after 10,000 cycles at a current density of 2 A g-1. Thus, this research overcomes the difficulty of synthesizing the pure Ni3S4 phase, which provides a new available pathway for constructing high-performance electrode materials.