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1.
Chem Commun (Camb) ; 56(83): 12566-12569, 2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-32940264

RESUMO

A stable artificial solid electrolyte interphase (ASEI) containing phosphazene and perfluoroalkoxy groups was designed to protect Li anodes. The ASEI with high ionic conductivity and mechanical robustness successfully suppressed the growth of Li dendrites, significantly enhancing the electrochemical performance of the Li-O2 batteries.

2.
J Am Chem Soc ; 2020 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-32532158

RESUMO

Vinylene-bridged covalent organic frameworks (COFs) have shown great potential for advanced applications because of their high chemical stability and intriguing semiconducting properties. Exploring new functional monomers available for the reticulation of vinylene-bridged COFs and establishing effective reaction conditions are extremely desired for enlarging the realm of this kind of material. In this work, a series of vinylene-bridged two-dimensional (2D) COFs are synthesized by Knoevenagel condensation of tricyanomesitylene with ditopic or tritopic aromatic aldehydes. With use of appropriate secondary amines as catalysts, high-crystalline vinylene-bridged COFs were achieved, exhibiting long-range ordered structures, well-defined nanochannels, high surface areas (up to 1231 m2 g-1), and excellent photophysical properties. Under a low loading amount and short reaction time, they enable aerobic photocatalytic transformation of arylboronic acids to phenols with high efficiency and excellent recyclability. This work demonstrates a new functional monomer, tricyanomesitylene, feasible for the general synthesis of vinylene-bridged COFs with potential application in photocatalytic organic transformation, which instigates further research on such kind of material.

3.
ChemSusChem ; 13(7): 1900-1905, 2020 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-31944610

RESUMO

Enzyme catalysts always show an excellent catalytic selectivity, which is important in biochemistry, especially in catalytic synthesis and biopharming. This selectivity is achieved by combining the binding effect induced by the electrostatic effect of the enzyme to attract a specific substrate and then the prearrangement of the substrates inside the enzyme pocket. Herein, we report a proof-of-concept application of an interfacial electrostatic field induced by constructing Schottky heterojunctions to mimic the electrostatic catalysis of an enzyme. In combination with the 3 D structure, a transition metal/carbon dyad was designed by nanoconfinement methods to promote the differential binding effect and the space-induced organization of the reaction intermediate (vanillyl alcohol) to develop a new one-step hydrogenolysis of vanillin for the production of 2-methoxy-4-methylphenol with a remarkably high selectivity (>99 %).

4.
Nat Commun ; 10(1): 5810, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31862935

RESUMO

Inferior charge transport in insulating and bulk discharge products is one of the main factors resulting in poor cycling stability of lithium-oxygen batteries with high overpotential and large capacity decay. Here we report a two-step oxygen reduction approach by pre-depositing a potassium carbonate layer on the cathode surface in a potassium-oxygen battery to direct the growth of defective film-like discharge products in the successive cycling of lithium-oxygen batteries. The formation of defective film with improved charge transport and large contact area with a catalyst plays a critical role in the facile decomposition of discharge products and the sustained stability of the battery. Multistaged discharge constructing lithium peroxide-based heterostructure with band discontinuities and a relatively low lithium diffusion barrier may be responsible for the growth of defective film-like discharge products. This strategy offers a promising route for future development of cathode catalysts that can be used to extend the cycling life of lithium-oxygen batteries.

5.
Nanoscale ; 11(38): 17860-17868, 2019 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-31553002

RESUMO

In this work, the impact of oxygen vacancies and nitrogen-doped carbon coating on the sodium-ion storage properties of anatase TiO2 has been demonstrated. Oxygen vacancies and nitrogen-doped carbon coating were introduced simultaneously by the calcination of core-shell structured TiO2 spheres in a reducing atmosphere. Compared to the anatase TiO2 with and without oxygen vacancies, TiO2-x@NC exhibits much better electrochemical performance in the storage of sodium ions. A high reversible capacity of 245.6 mA h g-1 is maintained at 0.1 A g-1 after 200 cycles, and a high specific capacity of 155.6 mA h g-1 is achieved at a high rate of 5.0 A g-1. The significantly improved electrochemical performance of the core-shell structured anatase TiO2 spheres is attributed to the synergistic effect of the oxygen vacancies in the anatase lattice and surface nitrogen-doped carbon coating. This work provides an efficient strategy for improving the electrochemical performance of metal-oxide-based electrode materials for sodium-ion batteries.

6.
Chem Commun (Camb) ; 55(76): 11394-11397, 2019 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-31482882

RESUMO

A nitrogen-thermal approach via the reaction between transition metal species and N dopants affords us the ability to optimize the tradeoff between the number of exposed transition metal/carbon (exemplified by cobalt in this work) boundaries and the most pronounced interfacial rectifying contact to achieve the highly efficient and selective hydrogenation and dehydrogenation of N-heterocycle compounds in a reversible manner.

7.
J Am Chem Soc ; 141(38): 14976-14980, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31523954

RESUMO

The traditional NH3 production method (Haber-Bosch process) is currently complemented by electrochemical synthesis at ambient conditions, but the rather low selectivity (as indicated by the Faradaic efficiency) for the electrochemical reduction of molecular N2 into NH3 impedes the progress. Here, we present a powerful method to significantly boost the Faradaic efficiency of Au electrocatalysts to 67.8% for the nitrogen reduction reaction (NRR) by increasing their electron density through the construction of inorganic donor-acceptor couples of Ni and Au nanoparticles. The unique role of the electron-rich Au centers in facilitating the fixation and activation of N2 was also investigated via theoretical simulation methods and then confirmed by experimental results. The highly coupled Au and Ni nanoparticles supported on nitrogen-doped carbon are stable for reuse and long-term performance of the NRR, making the electrochemical process more sustainable for practical application.

8.
Nat Commun ; 10(1): 4380, 2019 09 26.
Artigo em Inglês | MEDLINE | ID: mdl-31558716

RESUMO

Production of ammonia is currently realized by the Haber-Bosch process, while electrochemical N2 fixation under ambient conditions is recognized as a promising green substitution in the near future. A lack of efficient electrocatalysts remains the primary hurdle for the initiation of potential electrocatalytic synthesis of ammonia. For cheaper metals, such as copper, limited progress has been made to date. In this work, we boost the N2 reduction reaction catalytic activity of Cu nanoparticles, which originally exhibited negligible N2 reduction reaction activity, via a local electron depletion effect. The electron-deficient Cu nanoparticles are brought in a Schottky rectifying contact with a polyimide support which retards the hydrogen evolution reaction process in basic electrolytes and facilitates the electrochemical N2 reduction reaction process under ambient aqueous conditions. This strategy of inducing electron deficiency provides new insight into the rational design of inexpensive N2 reduction reaction catalysts with high selectivity and activity.

9.
Adv Sci (Weinh) ; 6(7): 1801702, 2019 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-30989023

RESUMO

2D layered materials with atomic thickness have attracted extensive research interest due to their unique physicochemical and electronic properties, which are usually very different from those of their bulk counterparts. Heterojunctions or heterostructures based on ultrathin 2D materials have attracted increasing attention due to the integrated merits of 2D ultrathin components and the heterojunction effect on the separation and transfer of charges, resulting in important potential values for catalytic applications. Furthermore, 2D/2D heterostructures with face-to-face contact are believed to be a preferable dimensionality design due to their large interface area, which would contribute to enhanced heterojunction effect. Here, the cutting-edge research progress in 2D/2D heterojunctions and heterostructures is highlighted with a specific emphasis on synthetic strategies, reaction mechanism, and applications in catalysis (photocatalysis, electrocatalysis, and organic synthesis). Finally, the key issues and development perspectives in the applications of 2D/2D layered heterojunctions and heterostructures in catalysis are also discussed.

10.
Chem Commun (Camb) ; 55(27): 3971-3974, 2019 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-30874700

RESUMO

We described an effective way to generate a Co3O4 mesocrystal array with well-developed porosity, simply by uniting a coupled interface with hydrazine treatment. Due to the fast electron transfer and sufficient active sites, the Ti mesh-supported Co3O4 nanoneedles electrode could provide a current density of 49.9 mA cm-2 at 570 mV OER overpotential and has exceptionally high stability.

11.
J Am Chem Soc ; 141(1): 38-41, 2019 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-30525578

RESUMO

Highly efficient fixation of CO2 for the synthesis of useful organic carbonates has drawn much attention. The design of sustainable Lewis acid-base pairs, which has mainly relied on expensive organic ligands, is the key challenge in the activation of the substrate and CO2 molecule. Here, we report the application of Mott-Schottky type nanohybrids composed of electron-deficient Cu and electron-rich N-doped carbon for CO2 fixation. A ligand-free and additive-free method was used to boost the basicity of the carbon supports and the acidity of Cu by increasing the Schottky barrier at their boundary, mimicking the beneficial function of organic ligands acting as the Lewis acid and base in metal-organic frameworks (MOFs) or polymers and simultaneously avoiding the possible deactivation associated with the necessary stability of a heterogeneous catalyst. The optimal Cu/NC-0.5 catalyst exhibited a remarkably high turnover frequency (TOF) value of 615 h-1 at 80 °C, which is 10 times higher than that of the state-of-the-art metal-based heterogeneous catalysts in the literature.

12.
Nat Commun ; 9(1): 5236, 2018 12 07.
Artigo em Inglês | MEDLINE | ID: mdl-30531797

RESUMO

The widespread use of proton exchange membrane water electrolysis requires the development of more efficient electrocatalysts containing reduced amounts of expensive iridium for the oxygen evolution reaction (OER). Here we present the identification of 6H-phase SrIrO3 perovskite (6H-SrIrO3) as a highly active electrocatalyst with good structural and catalytic stability for OER in acid. 6H-SrIrO3 contains 27.1 wt% less iridium than IrO2, but its iridium mass activity is about 7 times higher than IrO2, a benchmark electrocatalyst for the acidic OER. 6H-SrIrO3 is the most active catalytic material for OER among the iridium-based oxides reported recently, based on its highest iridium mass activity. Theoretical calculations indicate that the existence of face-sharing octahedral dimers is mainly responsible for the superior activity of 6H-SrIrO3 thanks to the weakened surface Ir-O binding that facilitates the potential-determining step involved in the OER (i.e., O* + H2O → HOO* + H+ + e¯).

13.
ACS Nano ; 12(11): 11503-11510, 2018 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-30481967

RESUMO

Sodium-ion batteries (SIBs) are generally considered as promising cheap alternatives of lithium-ion batteries for stationary renewable energy storage and have received increasing attention in recent years. The exploration of anode materials with efficient electron transportation is essential for improving the performance of SIBs. Inspired by the signal transfer mode of a neuron, we designed a composite by stringing MoS2 nanoflower (soma) with multiwall carbon nanotubes (MWCNTs) (axons). High-resolution TEM observation reveals a lattice matching growth mechanism of MoS2 nanosheets on the interface of MWCNTs and the lattice expansion of the (002) plane of MoS2. The lattice matching among the MoS2 nanosheet and MWCNT could facilitate electron transfer and structure maintenance upon cycling. The expanded distance of the (002) plane of MoS2 would also promote the sodium-ion intercalation/deintercalation kinetics of the composite. Benefiting from the structural features, when used as an anode material for SIBs, the composite exhibits excellent electrochemical performance, including high specific capacity, excellent cycle stability, and superior rate capabilities. A stable capacity of 527.7 mAh g-1 can be achieved after 110 cycles at a current density of 100 mA g-1. The neuron-inspired design proposed is a promising and efficient strategy for the development of electrode materials for SIBs with high mass transport kinetics and structural stability.

14.
Micromachines (Basel) ; 9(5)2018 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-30424161

RESUMO

Transmembrane pressure across the glomerular filter barrier may underlie renal failure. However, studies of renal failure have been difficult owing to a lack of in vitro models to capture the transmembrane pressure in a controlled approach. Here we report a microfluidic platform of podocyte culture to investigate transmembrane pressure induced glomerular leakage. Podocytes, the glomerular epithelial cells essential for filtration function, were cultivated on a porous membrane supplied with transmembrane pressure ΔP. An anodic aluminum oxide membrane with collagen coating was used as the porous membrane, and the filtration function was evaluated using dextrans of different sizes. The results show that dextran in 20 kDa and 70 kDa can penetrate the podocyte membrane, whereas dextran in 500 kDa was blocked until ΔP ≥ 60 mmHg, which resembles the filtration function when ΔP was in the range of a healthy kidney (ΔP < 60 mmHg) as well as the hypertension-induced glomerular leakage (ΔP ≥ 60 mmHg). Additionally, analysis showed that synaptopodin and actin were also downregulated when ΔP > 30 mmHg, indicating that the dysfunction of renal filtration is correlated with the reduction of synaptopodin expression and disorganized actin cytoskeleton. Taking together, our microfluidic platform enables the investigation of transmembrane pressure in glomerular filter membrane, with potential implications for drug development in the future.

15.
Dalton Trans ; 47(45): 16155-16163, 2018 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-30378603

RESUMO

A top-down method was developed to synthesize hierarchical composites consisting of NiCo2O4 nanocubes and graphene nanosheets through the electrostatic interaction of negatively charged graphene oxide nanosheets and positively charged NiCo2O4 spheres. Employed as anode materials for lithium-ion batteries, the hierarchical composites exhibit remarkably high electrochemical performance, including large reversible capacity, superior rate capability, and excellent cycling performance. Large reversible capacities of 1024 and 648 mA h g-1 are maintained at a current density of 500 and 3000 mA g-1, respectively, for over 200 cycles. The excellent electrochemical performance of the composite is attributed to the synergistic effect of the hierarchical structure, the well dispersed NiCo2O4 nanocubes and the uniform graphene coating. This work provides an effective and promising strategy for the rational structural design of the metal oxide electrode material.

16.
Angew Chem Int Ed Engl ; 57(46): 15194-15198, 2018 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-30251296

RESUMO

As a new type of heterogeneous catalyst with "homogeneous-like" activity, single-site transition-metal materials are usually treated as integrated but separate active centers. A novel grouping effect is reported for single Ni-N4 sites in nitrogen-doped carbon (Ni/NC), where an effective ligand-stabilized polycondensation method endows Ni/NC nanocatalysts with a high content of single-site Ni up to 9.5 wt %. The enhanced electron density at each single Ni-N4 site promotes a highly efficient hydrogen transfer, which is exemplified by the coupling of benzyl alcohol and aniline into N-benzylaniline with a turnover frequency (TOF) value of 7.0 molN-benzylaniline molmetal -1 h-1 ; this TOF outpaces that of reported stable non-noble-metal-based catalysts by a factor of 2.

17.
Angew Chem Int Ed Engl ; 57(38): 12563-12566, 2018 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-30070752

RESUMO

The exploitation of metal-free organic polymers as electrodes for water splitting reactions is limited by their presumably low activity and poor stability, especially for the oxygen evolution reaction (OER) under more critical conditions. Now, the thickness of a cheap and robust polymer, poly(p-phenylene pyromellitimide) (PPPI) was rationally engineered by an in situ polymerization method to make the metal-free polymer available for the first time as flexible, tailorable, efficient, and ultra-stable electrodes for water oxidation over a wide pH range. The PPPI electrode with an optimized thickness of about 200 nm provided a current density of 32.8 mA cm-2 at an overpotential of 510 mV in 0.1 mol L-1 KOH, which is even higher than that (31.5 mA cm-2 ) of commercial IrO2 OER catalyst. The PPPI electrodes are scalable and stable, maintaining 92 % of its activity after a 48-h chronoamperometric stability test.

18.
Nat Commun ; 9(1): 2609, 2018 07 04.
Artigo em Inglês | MEDLINE | ID: mdl-29973591

RESUMO

Although a number of nonprecious materials can exhibit catalytic activity approaching (sometimes even outperforming) that of iridium oxide catalysts for the oxygen evolution reaction, their catalytic lifetimes rarely exceed more than several hundred hours under operating conditions. Here we develop an energy-efficient, cost-effective, scaled-up corrosion engineering method for transforming inexpensive iron substrates (e.g., iron plate and iron foam) into highly active and ultrastable electrodes for oxygen evolution reaction. This synthetic method is achieved via a desired corrosion reaction of iron substrates with oxygen in aqueous solutions containing divalent cations (e.g., nickel) at ambient temperature. This process results in the growth on iron substrates of thin film nanosheet arrays that consist of iron-containing layered double hydroxides, instead of rust. This inexpensive and simple manufacturing technique affords iron-substrate-derived electrodes possessing excellent catalytic activities and activity retention for over 6000 hours at 1000 mA cm-2 current densities.

19.
Adv Sci (Weinh) ; 5(7): 1800062, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30027039

RESUMO

Heterojunction photocatalysts at present are still suffering from the low charge separation/transfer efficiency due to the poor charge mobility of semiconductor-based photocatalysts. Atomic-scale heterojunction-type photocatalysts are regarded as a promising and effective strategy to overcome the drawbacks of traditional photocatalysts for higher photoenergy conversion efficiencies. Herein, an atomic-scale heterojunction composed of a boron nitride monolayer and graphene (h-BN-C/G) is constructed to significantly shorten the charge transfer path to promote the activation of molecular oxygen for artificial photosynthesis (exemplified with oxidative coupling of amines to imines). As the thinnest heterojunction, h-BN-C/G gives the highest conversion, which is eightfold higher than that of the mechanical mixture of graphene and boron nitride monolayers. h-BN-C/G exhibits a high turnover frequency value (4.0 mmol benzylamine g-1 h-1), which is 2.5-fold higher than that of the benchmark metal-free photocatalyst in the literature under even critical conditions.

20.
Angew Chem Int Ed Engl ; 57(29): 8865-8870, 2018 Jul 16.
Artigo em Inglês | MEDLINE | ID: mdl-29859011

RESUMO

Classical organic anode materials for Na-ion batteries are mostly based on conjugated carboxylate compounds, which can stabilize added electrons by the double-bond reformation mechanism. Now, 1,4-cyclohexanedicarboxylic acid (C8 H12 O4 , CHDA) with a non-conjugated ring (-C6 H10 -) connected with carboxylates is shown to undergo electrochemical reactions with two Na ions, delivering a high charge specific capacity of 284 mA h g-1 (249 mA h g-1 after 100 cycles), and good rate performance. First-principles calculations indicate that hydrogen-transfer-mediated orbital conversion from antibonding π* to bonding σ stabilize two added electrons, and reactive intermediate with unpaired electron is suppressed by localization of σ-bonds and steric hindrance. An advantage of CHDA as an anode material is good reversibility and relatively constant voltage. A large variety of organic non-conjugated compounds are predicted to be promising anode materials for sodium-ion batteries.

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