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1.
Artigo em Inglês | MEDLINE | ID: mdl-32841453

RESUMO

The electrochemical performance of vanadium oxide-based cathodes in aqueous zinc-ion batteries (ZIBs) depends on their crystal degree and composite state with carbon materials. Herein, an in-situ electrochemical induction strategy was developed to fabricate MOF-derived composite of amorphous V 2 O 5 and carbon materials (a-V 2 O 5 @C) for the first time, where the V 2 O 5 is amorphous state and uniformly distributed in carbon framework. The amorphous structure endows V 2 O 5 with more isotropic Zn 2+ diffusion routes and active sites, resulting in fast Zn 2+ transport and high specific capacity. The porous carbon framework provides continuous electron transport pathway and ion diffusion channels. As a result, the a-V 2 O 5 @C composites display extraordinary electrochemical performance. This work will pave the way for designing the cathodes of ZIBs with superior rate performance.

2.
Adv Mater ; 32(25): e2001755, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32406976

RESUMO

Current aqueous Zn batteries (ZBs) seriously suffer from dendrite issues caused by rough electrode surfaces. Despite significant efforts in prolonging lifespan of these batteries, little effort has been devoted to dendrite elimination in commercial-grade cathode loading mass. Instead, demonstrations have only been done at the laboratory level (≤2 mg cm-2 ). Additionally, new dilemmas regarding change of the proton-storage behavior and interface pulverization have emerged in turn. Herein, hydrogen-substituted graphdiyne (HsGDY), with sub-ångström level ion tunnels and robust chemical stability, is designed as an artificial interface layer to address these issues. This strategy prolongs the symmetric cell lifespan to >2400 h (100 days), which is 37 times larger than without protection (63 h). The simulation of dual fields reveals that HsGDY can redistribute the Zn2+ concentration field by spatially forcing Zn2+ to deviate from the irregular electric field. During practical use, the as-assembled full batteries deliver a long lifespan 50 000 cycles and remain stable even at a commercial-grade cathode loading mass of up to 22.95 mg cm-2 . This HsGDY-protection methodology represents great progress in Zn dendrite protection and demonstrates enormous potential in metal batteries.

3.
ACS Nano ; 14(1): 595-602, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31891248

RESUMO

A carbon microtube aerogel (CMA) with hydrophobicity, strong adsorption capacity, and superb recyclability was obtained by a feasible approach with economical raw material, such as kapok fiber. The CMA possesses a great adsorption capacity of 78-348 times its weight. Attributed to its outstanding thermal stability and excellent mechanical properties, the CMA can be used for many cycles of distillation, squeezing, and combustion without degradation, which suggests a potential practical application in oil-water separation. In addition, the adsorption capacity still retained 98% by distillation, 97% by squeezing, and 90% by combustion after 10 cycles. Therefore, the obtained CMA has a broad prospect as an economical, efficient, and environmentally friendly adsorbent.

4.
ACS Nano ; 13(10): 11733-11740, 2019 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-31525961

RESUMO

Molybdenum disulfide (MoS2) has attracted much attention as a promising alternative to Pt-based catalysts for highly efficient hydrogen generation. However, it suffers sluggish kinetics for driving the hydrogen evolution reaction (HER) process because of inert basal planes, especially in alkaline solution. Here, we show a combination of heteroatom doping and phase transformation strategies to engineer the in-plane structure of MoS2, that trigger their catalytic activities. Systematic characterizations are performed with advanced aberration-corrected microscopy and X-ray techniques, indicating that an as-designed MoS2 catalyst has a distorted zigzag-chain superlattice in metallic phase, while its in-plane structure was engineered via the incorporation of cobalt and oxygen species. The optimal Co, O dual-doped metallic phase molybdenum disulfide (1T-MoS2) electrocatalyst shows a significantly enhanced HER activity with a low overpotential of 113 mV at 10 mA cm-2 and corresponding small Tafel slope of 50 mV dec-1, accompanied by the robust stability in alkaline media. The calculated turnover frequency is higher than 6.65 H2 s-1 at an overpotential of 200 mV. More in-depth insights from the first-principle calculations illustrate that the water dissociation as a rate-determining step was largely accelerated by the in-plane Co-O-Mo species and fast electron transfer of the catalyst. Benefiting from ingenious design and fine identifications, this work provides a fundamental understanding of the relationships among heteroatom doping, phase transformation, and performance for MoS2-based catalysts.

5.
Angew Chem Int Ed Engl ; 58(21): 7062-7067, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-30893503

RESUMO

Rechargeable aqueous zinc-ion batteries (ZIBs) are promising energy-storage devices owing to their low cost and high safety. However, their energy-storage mechanisms are complex and not well established. Recent energy-storage mechanisms of ZIBs usually depend on cationic redox processes. Anionic redox processes have not been observed owing to the limitations of cathodes and electrolytes. Herein, we describe highly reversible aqueous ZIBs based on layered VOPO4 cathodes and a water-in-salt electrolyte. Such batteries display reversible oxygen redox chemistry in a high-voltage region. The oxygen redox process not only provides about 27 % additional capacity, but also increases the average operating voltage to around 1.56 V, thus increasing the energy density by approximately 36 %. Furthermore, the oxygen redox process promotes the reversible crystal-structure evolution of VOPO4 during charge/discharge processes, thus resulting in enhanced rate capability and cycling performance.

6.
Nat Commun ; 10(1): 704, 2019 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-30741958

RESUMO

A peroxidase catalyzes the oxidation of a substrate with a peroxide. The search for peroxidase-like and other enzyme-like nanomaterials (called nanozymes) mainly relies on trial-and-error strategies, due to the lack of predictive descriptors. To fill this gap, here we investigate the occupancy of eg orbitals as a possible descriptor for the peroxidase-like activity of transition metal oxide (including perovskite oxide) nanozymes. Both experimental measurements and density functional theory calculations reveal a volcano relationship between the eg occupancy and nanozymes' activity, with the highest peroxidase-like activities corresponding to eg occupancies of ~1.2. LaNiO3-δ, optimized based on the eg occupancy, exhibits an activity one to two orders of magnitude higher than that of other representative peroxidase-like nanozymes. This study shows that the eg occupancy is a predictive descriptor to guide the design of peroxidase-like nanozymes; in addition, it provides detailed insight into the catalytic mechanism of peroxidase-like nanozymes.


Assuntos
Compostos de Cálcio/metabolismo , Nanoestruturas/química , Óxidos/metabolismo , Peroxidases/metabolismo , Titânio/metabolismo , Catálise , Ativação Enzimática , Ensaios Enzimáticos , Cinética , Nanopartículas Metálicas/química , Oxirredução
7.
Adv Mater ; 30(32): e1802525, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29939441

RESUMO

With the unique-layered structure, MXenes show potential as electrodes in energy-storage devices including lithium-ion (Li+ ) capacitors and batteries. However, the low Li+ -storage capacity hinders the application of MXenes in place of commercial carbon materials. Here, the vanadium carbide (V2 C) MXene with engineered interlayer spacing for desirable storage capacity is demonstrated. The interlayer distance of pristine V2 C MXene is controllably tuned to 0.735 nm resulting in improved Li-ion capacity of 686.7 mA h g-1 at 0.1 A g-1 , the best MXene-based Li+ -storage capacity reported so far. Further, cobalt ions are stably intercalated into the interlayer of V2 C MXene to form a new interlayer-expanded structure via strong V-O-Co bonding. The intercalated V2 C MXene electrodes not only exhibit superior capacity up to 1117.3 mA h g-1 at 0.1 A g-1 , but also deliver a significantly ultralong cycling stability over 15 000 cycles. These results clearly suggest that MXene materials with an engineered interlayer distance will be a rational route for realizing them as superstable and high-performance Li+ capacitor electrodes.

8.
Small ; 14(19): e1800128, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29635871

RESUMO

Developing efficient and low-cost defective carbon-based catalysts for the oxygen reduction reaction (ORR) is essential to metal-air batteries and fuel cells. Active sites engineering toward these catalysts is highly desirable but challenging to realize boosted catalytic performance. Herein, a sandwich-like confinement route to achieve the controllable regulation of active sites for carbon-based catalysts is reported. In particular, three distinct catalysts including metal-free N-doped carbon (NC), single Co atoms dispersed NC (Co-N-C), and Co nanoparticles-contained Co-N-C (Co/Co-N-C) are controllably realized and clearly identified by synchrotron radiation-based X-ray spectroscopy. Electrochemical measurements suggest that the Co/Co-N-C catalyst delivers optimized ORR performance due to the rich Co-Nx active sites and their synergistic effect with metallic Co nanoparticles. This work provides deep insight for rationally designing efficient ORR catalyst based on active sites engineering.

9.
Chem Commun (Camb) ; 54(35): 4481-4484, 2018 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-29658552

RESUMO

Few-layer ternary FePS3 nanosheets, prepared via chemical vapor transport synthesis and ball-milling exfoliation, exhibit excellent electrocatalytic performance for the oxygen evolution reaction in an alkaline medium. Combined with first principles calculations, our X-ray spectroscopy and HRTEM results clearly reveal that the introduction of in-plane defects in FePS3 layers after exfoliation and formation of a FePS3-FeOOH heterostructure during the OER process largely contribute to the catalytic activity enhancement.

10.
Small ; 14(6)2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29239096

RESUMO

Admittedly, the surface atomic structure of heterogenous catalysts toward the electrochemical oxygen reduction reaction (ORR) are accepted as the important features that can tune catalytic activity and even catalytic pathway. Herein, a surface engineering strategy to controllably synthesize a carbon-layer-wrapped cobalt-catalyst from 2D cobalt-based metal-organic frameworks is elaborately demonstrated. Combined with synchrotron radiation X-ray photoelectron spectroscopy, the soft X-ray absorption near-edge structure results confirmed that rich covalent interfacial CoNC bonds are efficiently formed between cobalt nanoparticles and wrapped carbon-layers during the polydopamine-assisted pyrolysis process. The X-ray absorption fine structure and corresponding extended X-ray absorption fine structure spectra further reveal that the wrapped cobalt with Co-N coordinations shows distinct surface distortion and atomic environmental change of Co-based active sites. In contrast to the control sample without coating layers, the 800 °C-annealed cobalt catalyst with N-doped carbon layers enwrapping achieves significantly enhanced ORR activity with onset and half-wave potentials of 0.923 and 0.816 V (vs reversible hydrogen electrode), highlighting the important correlation between surface atomic structure and catalytic property.

11.
Nanoscale ; 9(21): 6975-6983, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-28524923

RESUMO

Vertical 1T-MoS2 nanosheets with an expanded interlayer spacing of 9.8 Å were successfully grown on a graphene surface via a one-step solvothermal method. Such unique hybridized structures provided strong electrical and chemical coupling between the vertical nanosheets and graphene layers by means of C-O-Mo bonding. The merits are very beneficial for a high-efficiency electron/ion transport pathway and structural stability. As a proof of concept, the lithium ion battery with the as-obtained hybrid's electrode exhibited excellent rate performance with a 666 mA h g-1 capacity at a high current density of 3500 mA g-1. We can extend this method to produce various metallic 1T-MX2 (M = transition metal; X = chalcogen) vertically edged on a graphene frame as one of the promising hetero-structures for several specific applications in the fields of electronics, optics and catalysis.

12.
Phys Chem Chem Phys ; 19(1): 557-561, 2016 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-27910968

RESUMO

Layered Cu2MoS4, consisting of earth-abundant elements, is regarded as a potential catalyst for the hydrogen evolution reaction (HER). Herein, we demonstrate a Cu2O-based template strategy to synthesise hierarchical hollow nanostructures of Cu2MoS4. The characterizations reveal that the electrochemically active surface of the hollow Cu2MoS4 is largely enhanced, in contrast to the nanosheet or nanoparticle structures. As the direct outcome, the designed hierarchical hollow structures display excellent HER activities with a low overvoltage and small Tafel slope. This study may provide new inspiration for the research of other ternary sulphide materials as well as subsequently accelerating their applications in the field of catalysis.

13.
Small ; 12(41): 5684-5691, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27578055

RESUMO

Ultrafast and high capacity all-carbon supercapacitors with 3D porous aerogel electrode are realized by combining carbon nanostructures of various dimensionalities, including 0D carbon onions, 1D carbon nanotubes, and 2D graphene oxide. The synergistic effects from the different forms of nanocarbons render this hybrid outstanding capacitance with excellent stability, even at ultrafast charge-discharge rates.

14.
Materials (Basel) ; 9(7)2016 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-28773628

RESUMO

The concentration and small size of nanodiamonds (NDs) plays a crucial role in the mechanical performance of epoxy-based nanocomposites by modifying the interface strength. Herein, we systemically analyzed the relation between the high concentration and small size of ND and the fracture properties of its epoxy-based nanocomposites. It was observed that there is a two-fold increase in fracture toughness and a three-fold increase in fracture energy. Rationally, functionalized-NDs (F-NDs) showed a much better performance for the nanocomposite than pristine NDs (P-NDs) because of additional functional groups on its surface. The F-ND/epoxy nanocomposites exhibited rougher surface in contrast with the P-ND/epoxy, indicating the presence of a strong interface. We found that the interfaces in F-ND/epoxy nanocomposites at high concentrations of NDs overlap by making a web, which can efficiently hinder further crack propagation. In addition, the de-bonding in P-ND/epoxy nanocomposites occurred at the interface with the appearance of plastic voids or semi-naked particles, whereas the de-bonding for F-ND/epoxy nanocomposites happened within the epoxy molecular network instead of the interface. Because of the strong interface in F-ND/epoxy nanocomposites, at high concentrations the de-bonding within the epoxy molecular network may lead to subsequent cracks, parallel to the parent crack, via crack splitting which results in a fiber-like structure on the fracture surface. The plastic void growth, crack deflection and subsequent crack growth were correlated to higher values of fracture toughness and fracture energy in F-ND/epoxy nanocomposites.

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