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1.
Chem Commun (Camb) ; 56(58): 8059-8062, 2020 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-32542252

RESUMO

We report a bioinspired emulsion microreactor composed of an electrical double layer to mimic the functions of cell membranes. This "artificial cell" can modulate the phase-oriented transport of reagents at the oil-liquid interface via the electrical double layer, affording a powerful tool to optimize the selectivity in a catalytic reaction.

2.
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 %).

3.
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.

4.
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.

5.
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.

6.
Angew Chem Int Ed Engl ; 58(34): 11903-11909, 2019 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-31209961

RESUMO

The modulation of electron density is an effective option for efficient alternative electrocatalysts. Here, p-n junctions are constructed in 3D free-standing FeNi-LDH/CoP/carbon cloth (CC) electrode (LDH=layered double hydroxide). The positively charged FeNi-LDH in the space-charge region can significantly boost oxygen evolution reaction. Therefore, the j at 1.485 V (vs. RHE) of FeNi-LDH/CoP/CC achieves ca. 10-fold and ca. 100-fold increases compared to those of FeNi-LDH/CC and CoP/CC, respectively. Density functional theory calculation reveals OH- has a stronger trend to adsorb on the surface of FeNi-LDH side in the p-n junction compared to individual FeNi-LDH further verifying the synergistic effect in the p-n junction. Additionally, it represents excellent activity toward water splitting. The utilization of heterojunctions would open up an entirely new possibility to purposefully regulate the electronic structure of active sites and promote their catalytic activities.

7.
Chem Commun (Camb) ; 55(44): 6173-6176, 2019 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-31045185

RESUMO

A COOH-terminated nitrogen-doped carbon aerogel exhibited 100% selectivity to two-electron oxygen reduction, exceeding reported carbonaceous and noble metal catalysts. The optimal electrode with the synergistic effect of C-N/C-COOH resulted in a minimum ηO2/H2O2 and gave an evolution rate of 60 mg L-1 g-1 h-1 for H2O2 with satisfactory mechanical and electrochemical stability for practical applications.

8.
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.

9.
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.

10.
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.

11.
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.

12.
Angew Chem Int Ed Engl ; 57(45): 14857-14861, 2018 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-30230147

RESUMO

Direct hydrogenation of C=C double bonds is a basic transformation in organic chemistry which is vanishing from simple practice because of the need for pressurized hydrogen. Ammonia borane (AB) has emerged as a hydrogen source through its safety and high hydrogen content. However, in conventional systems the hydrogen liberated from the high-cost AB cannot be fully utilized. Herein, we develop a novel Pd/g-C3 N4 stabilized Pickering emulsion microreactor, in which alkenes are hydrogenated in the oil phase with hydrogen originating from AB in the water phase, catalysed by the Pd nanoparticles at the interfaces. This approach is advantageous for more economical hydrogen utilization over conventional systems. The emulsion microreactor can be applied to a range of alkene substrates, with the conversion rates achieving >95 % by a simple modification.

13.
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.

14.
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.

15.
ChemSusChem ; 11(14): 2306-2309, 2018 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-29851293

RESUMO

Electrochemical gas evolution and activation reactions are complicated processes, involving not only active electrocatalysts but also the interaction among solid electrodes, electrolyte, and gas-phase products and reactants. In this study, multiphase interfaces of superadsorbing graphene-based electrodes were controlled without changing the active centers to significantly facilitate mass diffusion kinetics for superior performance. The achieved in-depth understanding of how to regulate the interfacial properties to promote the electrochemical performance could provide valuable clues for electrode manufacture and for the design of more active electrocatalysts.

16.
Org Lett ; 20(10): 2888-2891, 2018 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-29733613

RESUMO

The highly enantioselective preparation of spirooxindoles bearing α,α-disubstituted α-amino-ß-keto esters was achieved through [4 + 1] annulation of oxindoles and α-imine-ß-oxo-γ,δ-unsaturated esters under mild conditions in good yields (up to 82%) and stereoselectivities (up to >20:1 dr, 96% ee). The reaction is amenable to gram scale synthesis using catalyst loading as low as 1 mol %. The corresponding chiral α,α-disubstituted α-amino-ß-keto esters could be easily transformed into cyclopenta[ b]indole derivatives without erosion of enantiopurity.

17.
Angew Chem Int Ed Engl ; 57(10): 2697-2701, 2018 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-29341380

RESUMO

Engineering the adsorption of molecules on active sites is an integral and challenging part for the design of highly efficient transition-metal-based catalysts for methanol dehydrogenation. A Mott-Schottky catalyst composed of Ni nanoparticles and tailorable nitrogen-doped carbon-foam (Ni/NCF) and thus tunable adsorption energy is presented for highly efficient and selective dehydrogenation of gas-phase methanol to hydrogen and CO even under relatively high weight hourly space velocities (WHSV). Both theoretical and experimental results reveal the key role of the rectifying contact at the Ni/NCF boundaries in tailoring the electron density of Ni species and enhancing the absorption energies of methanol molecules, which leads to a remarkably high turnover frequency (TOF) value (356 mol methanol mol-1 Ni h-1 at 350 °C), outpacing previously reported bench-marked transition-metal catalysts 10-fold.

18.
Chem Commun (Camb) ; 53(76): 10544-10547, 2017 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-28890982

RESUMO

The oxygen evolution reaction (OER) is the rate-limiting process for water splitting, and highly efficient large-area OER photoanodes have been considered as an essential part in photoelectrochemical water splitting reactors. The high hole-electron separation efficiency of photoanodes is highly required for real applications of photoanodes in sufficiently harvesting solar energy. Herein we show that the inactive g-C3N4 nanolayers can be self-assembled with BiVO4 into a highly coupled BV/CN dyad to significantly enhance the charge separation efficiency of BiVO4 photoelectrodes for the OER. The incident photon-to-current conversion efficiency (IPCE) of visible light (400 nm) provided by the scalable BV/CN-5 photoanode was estimated to be 50% at 1.23 V vs. RHE in 0.5 M Na2SO4 solution and significantly increased to 97% at a bias voltage of 1.6 V vs. RHE.

19.
ChemSusChem ; 10(14): 2875-2879, 2017 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-28612461

RESUMO

Oxygen vacancies can help to capture oxygen-containing species and act as active centers for oxygen evolution reaction (OER). Unfortunately, effective methods for generating a high amount of oxygen vacancies on the surface of various nanocatalysts are rather limited. Here, we described an effective way to generate oxygen-vacancy-rich surface of transition metal oxides, exemplified with Co3 O4 , simply by constructing highly coupled interface of ultrafine Co3 O4 nanocrystals and metallic Ti. Impressively, the amounts of oxygen vacancy on the surface of Co3 O4 /Ti surpassed the reported values of the Co3 O4 modified even under highly critical conditions. The Co3 O4 /Ti electrode could provide a current density of 23 mA cm-2 at an OER overpotential of 570 mV, low Tafel slope, and excellent durability in neutral medium. Because of the formation of a large amount of oxygen vacancies as the active centers for OER on the surface, the TOF value of the Co3 O4 @Ti electrode was optimized to be 3238 h-1 at an OER overpotential of 570 mV, which is 380 times that of the state-of-the-art non-noble nanocatalysts in the literature.


Assuntos
Cobalto/química , Nanopartículas/química , Nanotecnologia , Óxidos/química , Oxigênio/química , Titânio/química , Água/química , Animais , Eletroquímica , Eletrodos , Engenharia , Oxirredução
20.
Phys Chem Chem Phys ; 19(26): 16989-16999, 2017 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-28597895

RESUMO

Photocatalytic nanostructures loaded with metallic nanoparticles are being considered as a potential candidate for designing efficient water splitting devices. Here, we aim to unveil the plasmonic behavior of a device made of Au-TiO2 nanostructures through in-depth investigations combining electron energy loss spectroscopy (EELS) and cathodoluminescence (CL). The experiments confirm the existence of Au bulk plasmon excitation, intrinsic interband transitions, and plasmon losses over a wide range of energies (0.6-2.4 eV). Depending on the size and the shape of the obtained nanostructures, such as fishing hook (FH), asymmetric nanorod (AR), and a/symmetric nanoparticles, in our devices, the dephasing times and the quality factors of the modes vary. Finite difference time domain simulations were then carried out on FH and AR structures. These simulations indicate good agreement between the electric field enhancement and the obtained plasmon excitation as observed in EELS. Moreover, the plasmonic activity obtained by CL and EELS was correlated with the photocurrent measurements recorded with the device, which confirmed that the localized plasmons in Au generate hot electrons and enhance the photoresponse of the device. This study confirms the functionality of the metal dielectric photocatalyst device over a wide range of wavelengths ranging from UV to near IR.

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