Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 109
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Nat Commun ; 12(1): 2039, 2021 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-33795681

RESUMO

Photocatalytic hydrogen peroxide (H2O2) generation represents a promising approach for artificial photosynthesis. However, the sluggish half-reaction of water oxidation significantly limits the efficiency of H2O2 generation. Here, a benzylamine oxidation with more favorable thermodynamics is employed as the half-reaction to couple with H2O2 generation in water by using defective zirconium trisulfide (ZrS3) nanobelts as a photocatalyst. The ZrS3 nanobelts with disulfide (S22-) and sulfide anion (S2-) vacancies exhibit an excellent photocatalytic performance for H2O2 generation and simultaneous oxidation of benzylamine to benzonitrile with a high selectivity of >99%. More importantly, the S22- and S2- vacancies can be separately introduced into ZrS3 nanobelts in a controlled manner. The S22- vacancies are further revealed to facilitate the separation of photogenerated charge carriers. The S2- vacancies can significantly improve the electron conduction, hole extraction, and kinetics of benzylamine oxidation. As a result, the use of defective ZrS3 nanobelts yields a high production rate of 78.1 ± 1.5 and 32.0 ± 1.2 µmol h-1 for H2O2 and benzonitrile, respectively, under a simulated sunlight irradiation.

2.
ACS Nano ; 15(3): 5478-5485, 2021 03 23.
Artigo em Inglês | MEDLINE | ID: mdl-33599489

RESUMO

With the excellent structural design, rotary triboelectric nanogenerator (R-TENG) is suitable for harvesting mechanical energy such as wind energy and water energy to build a self-powered electrochemical system for environmental science. The electrochemical performance has been greatly improved by using the pulsed direct-current (PDC) output of a TENG; however, a full-wave PDC (FW-PDC) is hardly realized in R-TENG devices due to existence of phase superposition. Here, a R-TENG with FW-PDC output is reported to perform a self-powered electro-Fenton system for enhancing the removal efficiency of levofloxacin (OFL). By adjusting the rotation center angle ratio between each rotator and stator unit, the phase superposition of R-TENG caused by multiple parallel electrodes can be effectively eliminated, thus achieving the desired FW-PDC output. Because of the reduced electrode passivation effect, the removal efficiency of OFL is improved by 30% under equal electric charges through using the designed R-TENG with FW-PDC output compared to traditional R-TENG. This study provides a promising methodology to improve the performance of self-powered electrochemical process for treating environment pollutions.

3.
Artigo em Inglês | MEDLINE | ID: mdl-33400491

RESUMO

Herein, we introduce polymer nanofibers of TiO2@NiCo-LDH as interlayers into Li-S batteries. From 0 to 60 °C, the interlayers can deliver high sulfur utilization, an outstanding rate capability, and excellent cycling life. High-temperature excitation makes it easier for the valence band electrons of TiO2 to transition to the conduction band. The electron-hole pairs formed on the surface combine with the ether group of 1,3-dioxolane in the electrolyte, which greatly reduces the decomposition and volatilization rates of the electrolyte, ensuring Li-S batteries with good cycle performance at high temperatures. The capacity can stabilize at 798.6 mAh g-1 after 100 cycles at 60 °C and 1C, and the battery can provide a capacity higher than 323.2 mAh g-1 at 0 °C. Simultaneously, the lithium metal symmetrical battery with a functional separator can be continuously cycled for 1800 and 750 h without a short circuit at the current densities of 0.65 and 1.63 mA cm-2, respectively.

4.
ACS Appl Mater Interfaces ; 13(1): 2033-2043, 2021 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-33378149

RESUMO

The effective activation and utilization of O2 have always been the focus of scientists because of its wide applications in catalysis, organic synthesis, life and medical science. Here, a novel method for activating O2 spontaneously via interfacial oxygen vacancies on carbon-coated TiO2-x to generate reactive oxygen species (ROS) with versatile applications is reported. The interfacial oxygen vacancies can be stabilized by the carbon layer and hold its intrinsic properties for spontaneous oxygen activation without light irradiation, while common surface oxygen vacancies on TiO2-x are always consumed by the capture of H2O to form the surface hydroxyls. Thus, O2 absorbed at the interface of carbon and TiO2-x can be directly activated into singlet oxygen (1O2) or superoxide radicals (·O2-), confirmed both experimentally and theoretically. These reactive oxygen species exhibit excellent performance in oxidation reactions and inhibition of MCF-7 cancer cells, providing new insight into the effective utilization of O2 via oxygen vacancies on metal oxides.


Assuntos
Carbono/química , Oxigênio/química , Oxigênio Singlete/química , Superóxidos/síntese química , Titânio/química , Compostos Azo/química , Catálise , Sobrevivência Celular/efeitos dos fármacos , Humanos , Células MCF-7 , Oxirredução , Oxigênio Singlete/farmacologia , Superóxidos/farmacologia , Água/química
5.
ACS Nano ; 2020 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-33315390

RESUMO

Amorphous bimetallic borides are an emerging class of catalytic nanomaterial that has demonstrated excellent catalytic performance due to its glass-like structure, abundant unsaturated active sites, and synergistic electronic effects. However, the creation of mesoporous Earth-abundant bimetallic metal borides with tunable metal proportion remains a challenge. Herein, we develop a sophisticated and controllable dual-reducing agent strategy to synthesize the mesoporous nickel-cobalt boron (NiCoB) amorphous alloy spheres (AASs) with adjustable compositions by using a soft template-directed assembly approach. The selective use of tetrabutylphosphonium bromide (Bu4PBr) is beneficial to generate well-defined mesopores because it both moderates the reduction rate by decreasing the reducibility of M2+ species and prevents the generation of soap bubbles. Our meso-Ni10.0Co74.5B15.5 AASs generate the highest catalytic performance for the hydrolytic dehydrogenation of ammonia borane (AB). Its high performance is attributed to the combination of optimal synergistic effects between Ni, Co, and B as well as the high surface area and the good mass transport efficiency due to the open mesopores. This work describes a systematic approach for the design and synthesis of mesoporous bimetallic borides as efficient catalysts.

6.
ACS Appl Mater Interfaces ; 12(46): 51537-51545, 2020 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-33161716

RESUMO

Steam generation and photocatalytic degradation of organic pollutants based on solar light are regarded as two important strategies for addressing the water scarcity issues. The water evaporation efficiency was greatly inhibited by the high cost, low stability, and low efficiencies of solar light absorption and photothermal conversion of photothermal materials. Moreover, volatile organic compounds (VOCs) are easily volatilized and enriched in as-distilled water during the photothermal process. Inspired by the structure of biomass materials in nature, a bifunctional solar light-driven steam generation and VOC removal microreactor was explored by coating commercial TiO2 (P25) powders on a carbonized biomass waste Flammulina. With the 3D aligned porous carbon architectures, this microreactor exhibited both a high water evaporation rate (37.0 kg m-2 h-1) and a high energy conversion efficiency (91.2%) under simulated sunlight irradiation (light intensity = 25.5 kW m-2). A high VOC removal rate (80.9% in 40 min) was also achieved during the steam generation process via choosing phenol as the probe pollutant molecules. The nature-inspired designing concept and bifunctional microreactor in this study may open up a new strategy for producing clean distilled water from seawater with an efficient removal of VOCs.

7.
Nano Lett ; 20(11): 8415-8419, 2020 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-33095021

RESUMO

One-dimensional sp-hybridized carbon wires, including cumulenes and polyynes, can be regarded as finite versions of carbynes. They are likely to be good candidates for molecular-scale conducting wires as they are predicted to have a high-conductance. In this study, we first characterize the single-molecule conductance of a series of cumulenes and polyynes with a backbone ranging in length from 4 to 8 carbon atoms, including [7]cumulene, the longest cumulenic carbon wire studied to date for molecular electronics. We observe different length dependence of conductance when comparing these two forms of carbon wires. Polyynes exhibit conductance decays with increasing molecular length, while cumulenes show a conductance increase with increasing molecular length. Their distinct conducting behaviors are attributed to their different bond length alternation, which is supported by theoretical calculations. This study confirms the long-standing theoretical predictions on sp-hybridized carbon wires and demonstrates that cumulenes can form highly conducting molecular wires.

8.
ACS Appl Mater Interfaces ; 12(40): 44731-44742, 2020 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-32931240

RESUMO

The photoelectrocatalytic (PEC) technique has attracted much attention to getting clear energy and environmental purification. Simultaneous reactions of solar energy generation could be used to apply for practical applications to maximize the functionality of reactor systems. Herein, we crafted a self-driving photoelectrocatalytic reactor system, comprising platinum (Pt) modified p-Si nanowires (Pt/Si-NWs) as a photocathode and TiO2 nanotube arrays (TiO2-NTAs) as a photoanode for synergistic H2 evolution and water purification, respectively. Hydrogen evolution in the cathode chamber and environmental remediation in the anode chamber were achieved with the aid of appropriate bandgap illumination and self-built bias voltage. The mismatch of Fermi levels between TiO2-NTAs and Si-NWs reduced the recombination rates of photoinduced electrons and holes through the formation of Z scheme and inner electric filed. The synergistic PEC reactions exhibited much higher activities than those achieved using other systems so far. This basic principal could be applied for fabricating other PEC reactors in photoelectro conversion devices and be established as design guidelines for reactors to maximize the PEC performance.

9.
ACS Omega ; 5(26): 16183-16188, 2020 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-32656440

RESUMO

A facile in situ one-step route for the preparation of platinum nanoparticles supported on metal-organic frameworks (MOFs) without adding stabilizing agents was developed. The obtained 10% Pt@MOF-T3 material possessed a large surface area and high crystallinity. Meanwhile, uniform and well-dispersed platinum nanoparticles were formed inside the cavities of MOFs, which could be attributed to the efficient complexation and stabilization effect derived from the dipyridyl groups. The as-synthesized 10% Pt@MOF-T3 sample showed high activity and selectivity in the hydrogenation of 5-hydroxymethylfurfural (HMF). This excellent catalytic performance could be attributed to the synergistic effects of well-dispersed platinum nanoparticles and electron donation offered by MOFs. Meanwhile, the presence of bipyridine ligands in the MOF framework avoided the irreversible adsorption of the hydrocarbon compounds, leading to the enhanced catalytic efficiency. Besides, it was easily recycled and reused at least five times, showing good recyclability.

10.
ACS Appl Mater Interfaces ; 12(29): 32604-32614, 2020 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-32594735

RESUMO

The synergistic photocatalytic Fenton reaction is a powerful advanced oxidation technique for the degradation of persistent organic pollutants. However, microwave-induced thermal effects on the formation of novel structures facilitating the photocatalytic degradation have been rarely reported. Herein, a two-step microwave thermal strategy was developed to synthesize a new hybrid catalyst comprising defective WO3-x nanowires coupled with reduced graphene oxides (rGOs). Conventionally, microwave methods could induce superhot spots on the GO surface, resulting in the site-specific crystallization and oriented growth of WO3. However, in the solid phase, localized microwave thermal effects could reduce the interfacial area between WO3 and rGO and enhance the bonding between them. As for the unique structure and surface properties, the synthesized catalyst enhanced the light absorption, promoted the interfacial charge separation, and increased the carrier density in the photocatalytic processes. In addition, surface formation of W4+ provided a new pathway for Fe3+/Fe2+ cycling which linked the photocatalytic reaction and the Fenton process. The optimized catalyst exhibited a remarkable performance in the degradation of bisphenol A with a ∼83% removal yield via a photo-Fenton route. These microwave-induced functionalities of materials for synergistic reactions could also give a new avenue to other photoelectrocatalytic fields and solar cells.

11.
Angew Chem Int Ed Engl ; 59(34): 14303-14307, 2020 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-32495388

RESUMO

This study explores a new mode of contortion in perylene diimides where the molecule is bent, like a bow, along its long axis. These bowed PDIs were synthesized through a facile fourfold Suzuki macrocyclization with aromatic linkers and a tetraborylated perylene diimide that introduces strain and results in a bowed structure. By altering the strings of the bow, the degree of bending can be controlled from flat to highly bent. Through spectroscopy and quantum chemical calculations, it is demonstrated that the energy of the lowest unoccupied orbital can be controlled by the degree of bending in the structures and that the energy of the highest occupied orbital can be controlled to a large extent by the constitution of the aromatic linkers. The important finding is that the bowing results not only in red-shifted absorptions but also more facile reductions.

12.
ACS Appl Mater Interfaces ; 12(23): 26101-26112, 2020 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-32406667

RESUMO

Mesoporous metals have shown significant potential for use in catalysis; however, controllably synthesizing highly ordered mesoporous amorphous alloys is a serious challenge. In this paper, a synthesis strategy was developed for generating ordered amorphous alloy nanowire arrays from mesoporous Ni-P by combining mesoporous silica templating with electroless plating. Mesoporous silica is externally grafted with -CH3 and internally covered with -NH2 acting as an efficient template, ensuring the formation of Ni-P nanowires inside the pore channels and endowing the final product with an ordered mesoporous array structure. The resulting ordered mesoporous Ni-P amorphous alloy nanowire arrays were subjected to a liquid-phase sugar hydrogenation to polyols and exhibited a highly superior catalytic performance (97% glucose conversion and 94% maltose conversion) within 4 h at 4 MPa hydrogen pressure and 373 K relative to those reference catalysts, including conventionally prepared Ni-P amorphous alloy nanoparticles (87% glucose conversion and 86% maltose conversion), ordered mesoporous Ni nanowire arrays (90% glucose conversion and 87% maltose conversion), and the commercial Raney Ni catalyst (76% glucose conversion and 66% maltose conversion). According to a comparative study, the enhanced catalytic efficiencies can be ascribed to the integration of amorphous alloy properties and mesoporous material characteristics. The composition- and morphology-controllable synthesis presented here might supply a general synthetic methodology for rationally designing ordered mesoporous amorphous alloys for a broader range of applications.

13.
Angew Chem Int Ed Engl ; 59(39): 17182-17186, 2020 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-32463933

RESUMO

Highly effective photocatalysts for the hydrogen-evolution reaction were developed by conferring the linkers of NH2 -MIL-125(Ti), a metal-organic framework (MOF) constructed from TiOx clusters and 2-aminoterephthalic acid (linkers), with active copper centers. This design enables effective transfer of electrons from the linkers to the transient Cu2+ /Cu+ centers, leading to 7000-fold and 27-fold increase of carrier density and lifetime of photogenerated charges, respectively, as well as high-rate production of H2 under visible-light irradiation. This work provides a novel design of a photocatalyst for hydrogen evolution using non-noble Cu2+ /Cu+ as co-catalysts.

14.
Environ Sci Technol ; 54(9): 5902-5912, 2020 05 05.
Artigo em Inglês | MEDLINE | ID: mdl-32250099

RESUMO

Most photoelectrocatalytic (PEC) reactions are performed in the liquid phase for convenient electron transfer in an electrolyte solution. Herein, a novel PEC reactor involving a tandem combination of TiO2 nanorod array/fluorine-doped tin oxide (TiO2-NR/FTO) working electrodes and an electrochemical auxiliary cell was constructed to drive the highly efficient PEC oxidation of indoor gas (NOx). With the aid of a low bias voltage (0.3 V), the as-formed PEC reactor exhibited an 80% removal rate for oxidizing NO (500 ppb) under light irradiation, which is much higher than that of the traditional photocatalytic (PC) process. Upon being irradiated by light, the photogenerated electrons are quickly separated from the holes and transferred to the counter electrode (Pt) owing to the applied bias voltage, leaving photogenerated holes in the TiO2-NR/FTO electrode for oxidizing NO molecules. Moreover, both dry and humid NO could be effectively removed by the tandem TiO2-NR/FTO-based gas-phase PEC reactor, indicating that the NO molecules could also be directly oxidized by photogenerated holes in addition to hydroxyl radicals. The presence of trace amounts of water could promote the PEC oxidation of NO owing to the formation of hydroxyl radicals induced by reactions between the water and holes, which could further oxidize NO. This PEC reactor offers an energy-saving, environmentally friendly, and efficient route to treat air polluted with low concentrations of gases (NOx and SOx).


Assuntos
Nanotubos , Purificação da Água , Catálise , Gases , Oxirredução , Titânio
15.
Nat Commun ; 11(1): 1191, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32132527

RESUMO

Proton exchange membrane fuel cells have been regarded as the most promising candidate for fuel cell vehicles and tools. Their broader adaption, however, has been impeded by cost and lifetime. By integrating a thin layer of tungsten oxide within the anode, which serves as a rapid-response hydrogen reservoir, oxygen scavenger, sensor for power demand, and regulator for hydrogen-disassociation reaction, we herein report proton exchange membrane fuel cells with significantly enhanced power performance for transient operation and low humidified conditions, as well as improved durability against adverse operating conditions. Meanwhile, the enhanced power performance minimizes the use of auxiliary energy-storage systems and reduces costs. Scale fabrication of such devices can be readily achieved based on the current fabrication techniques with negligible extra expense. This work provides proton exchange membrane fuel cells with enhanced power performance, improved durability, prolonged lifetime, and reduced cost for automotive and other applications.

16.
J Hazard Mater ; 394: 122540, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32203718

RESUMO

Catalytic oxidation of CO at ambient temperature is an important reaction for many environmental applications. Here, we employed a defect engineering strategy to design an extraordinarily effective Sn-doped Co3O4 nanorods (NRs) catalyst for CO oxidation. Our combined theoretical and experimental data demonstrated that Co2+ in the lattice of Co3O4 were substituted by Sn4+. Based on a variety of characterizations and kinetic studies, this catalyst was found to combine the advantages of the nanorod-like morphology for largely exposing catalytically active Co3+ sites and the promotional effect of Sn dopant for adjusting the textural/redox properties. Additionally, the Sn-substituted Co3O4 NRs can be further activated via heat treatment to achieve low-temperature CO oxidation (T100 ∼ -100 °C) with excellent stability at ambient temperature. This study reveals the importance of Sn-substitution of inactive Co2+ in Co3O4 and provides an ultra-efficient catalyst for CO oxidation, making this robust material one of the most powerful catalysts available up to now.

17.
Small ; 16(10): e1906707, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32022431

RESUMO

Selective hydrogenation of nitriles is an industrially relevant synthetic route for the preparation of primary amines. Amorphous metal-boron alloys have a tunable, glass-like structure that generates a high concentration of unsaturated metal surface atoms that serve as active sites in hydrogenation reactions. Here, a method to create nanoparticles composed of mesoporous 3D networks of amorphous nickel-boron (Ni-B) alloy is reported. The hydrogenation of benzyl cyanide to ß-phenylethylamine is used as a model reaction to assess catalytic performance. The mesoporous Ni-B alloy spheres have a turnover frequency value of 11.6 h-1 , which outperforms non-porous Ni-B spheres with the same composition. The bottom-up synthesis of mesoporous transition metal-metalloid alloys expands the possible reactions that these metal architectures can perform while simultaneously incorporating more Earth-abundant catalysts.

18.
ACS Appl Mater Interfaces ; 11(45): 42504-42511, 2019 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-31642666

RESUMO

Intelligent actuating materials with vapor-stimulated mechanical response usually require complicated synthesizing processes or have a high cost. Here, we found that the UV/O3-modified poly(dimethylsiloxane) PDMS) film can show spontaneous curling deformation when it encounters small alcohol molecules such as ethanol vapor. Based on the coupling of the vapor-responsive PDMS film and triboelectric nanogenerator (TENG), a flexible actuator for object transport and a double-finger gripper for loading small objects are designed. The deformation and size change induced by vapor stimulation help these devices to adapt to the target objects of different sizes, while the electrostatic force provided by TENG can move or control the target object, for instance, the double-finger gripper can clamp an object of a weight of 6 g.

19.
Nat Commun ; 10(1): 4482, 2019 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-31578333

RESUMO

Electric fields have been proposed as having a distinct ability to catalyze chemical reactions through the stabilization of polar or ionic intermediate transition states. Although field-assisted catalysis is being researched, the ability to catalyze reactions in solution using electric fields remains elusive and the understanding of mechanisms of such catalysis is sparse. Here we show that an electric field can catalyze the cis-to-trans isomerization of [3]cumulene derivatives in solution, in a scanning tunneling microscope. We further show that the external electric field can alter the thermodynamics inhibiting the trans-to-cis reverse reaction, endowing the selectivity toward trans isomer. Using density functional theory-based calculations, we find that the applied electric field promotes a zwitterionic resonance form, which ensures a lower energy transition state for the isomerization reaction. The field also stabilizes the trans form, relative to the cis, dictating the cis/trans thermodynamics, driving the equilibrium product exclusively toward the trans.

20.
J Am Chem Soc ; 141(33): 13143-13147, 2019 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-31357860

RESUMO

Singlet fission, the generation of two triplet excited states from the absorption of a single photon, may potentially increase solar energy conversion efficiency. A major roadblock in realizing this potential is the limited number of molecules available with high singlet fission yields and sufficient chemical stability. Here, we demonstrate a strategy for developing singlet fission materials in which we start with a stable molecular platform and use strain to tune the singlet and triplet energies. Using perylene diimide as a model system, we tune the singlet fission energetics from endoergic to exoergic or iso-energetic by straining the molecular backbone. The result is an increase in the singlet fission rate by 2 orders of magnitude. This demonstration opens a door to greatly expanding the molecular toolbox for singlet fission.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...