Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 55
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Adv Mater ; : e2203835, 2022 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-35900795

RESUMO

Resource-abundant metal (e.g., zinc) batteries feature intrinsic advantages of safety and sustainability. Their practical feasibility, however, is impeded by the poor reversibility of metal anode, typically caused by the uncontrollable dendrite enlargement. Significant effort has been exerted to completely prevent dendrites from forming, but this seems less effective at high current densities. Herein, we present an alternative dendrite regulation strategy of forming tiny, homogeneously distributed, and identical zinc dendrites by facet matching, which effectively avoids undesirable dendrite enlargement. Confirmed by multiscale theoretical screening and characterization, the regularly exposed Cu(111) facets at the ridges of a copper nanowire are capable of such dendrite regulation by forming a low-mismatched Zn(002)/Cu(111) interface. Consequently, reversible zinc electroplating/stripping has been achieved at an unprecedentedly high rate of 100 mA cm-2 for over 30,000 cycles, corresponding to an accumulative areal capacity up to 30 Ah cm-2 . A full cell using this anode shows a high capacity of 308.3 mAh g-1 and a high capacity retention of 91.4% after 800 cycles. This strategy is also viable for magnesium and aluminum anodes, thus opening up a promising and universal avenue towards long life and high rate metal anodes. This article is protected by copyright. All rights reserved.

3.
Nat Commun ; 13(1): 3158, 2022 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-35672315

RESUMO

Electrocatalytic CO2 reduction to value-added hydrocarbon products using metallic copper (Cu) catalysts is a potentially sustainable approach to facilitate carbon neutrality. However, Cu metal suffers from unavoidable and uncontrollable surface reconstruction during electrocatalysis, which can have either adverse or beneficial effects on its electrocatalytic performance. In a break from the current catalyst design path, we propose a strategy guiding the reconstruction process in a favorable direction to improve the performance. Typically, the controlled surface reconstruction is facilely realized using an electrolyte additive, ethylenediamine tetramethylenephosphonic acid, to substantially promote CO2 electroreduction to CH4 for commercial polycrystalline Cu. As a result, a stable CH4 Faradaic efficiency of 64% with a partial current density of 192 mA cm-2, thus enabling an impressive CO2-to-CH4 conversion rate of 0.25 µmol cm-2 s-1, is achieved in an alkaline flow cell. We believe our study will promote the exploration of electrochemical reconstruction and provide a promising route for the discovery of high-performance electrocatalysts.

4.
J Phys Chem Lett ; 13(19): 4244-4250, 2022 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-35522045

RESUMO

Phase junctions of photocatalysts can promote the separation of photogenerated charge carriers for efficient utilization of the carriers. Construction of phase junctions and establishing their structure-performance relationship are still required. Herein, polycrystalline TiO2 decahedral plates with different phases were synthesized by thermal treatment-induced topotactic transition of titanium oxalate crystals. The phase of TiO2 evolved from pure anatase to anatase-brookite, anatase-brookite-rutile, and then to anatase-rutile, while the morphology of the decahedral plates was well maintained. The biphase anatase-brookite was found to be most efficient in photocatalytic hydrogen generation. Specifically, the hydrogen generation rate of the biphase anatase-brookite TiO2 was nearly 2.4 times greater than that of the biphase anatase-rutile TiO2. The spatially resolved surface photovoltage measurements indicate the more efficient separation of photogenerated charge carriers and thus greater photocatalytic activity of the former. This work provides a strategy for developing efficient phase-junction photocatalysts.

5.
Adv Mater ; 34(30): e2202072, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35580350

RESUMO

Surface oxygen vacancies have been widely discussed to be crucial for tailoring the activity of various chemical reactions from CO, NO, to water oxidation by using oxide-supported catalysts. However, the real role and potential function of surface oxygen vacancies in the reaction remains unclear because of their very short lifetime. Here, it is reported that surface oxygen vacancies can be well confined electrostatically for a polarization screening near the perimeter interface between Pt {111} nanocrystals and the negative polar surface (001) of ferroelectric PbTiO3. Strikingly, such a catalyst demonstrates a tunable catalytic CO oxidation kinetics from 200 °C to near room temperature by increasing the O2 gas pressure, accompanied by the conversion curve from a hysteresis-free loop to one with hysteresis. The combination of reaction kinetics, electronic energy loss spectroscopy (EELS) analysis, and density functional theory (DFT) calculations, indicates that the oxygen vacancies stabilized by the negative polar surface are the active sites for O2 adsorption as a rate-determining step, and then dissociated O moves to the surface of the Pt nanocrystals for oxidizing adsorbed CO. The results open a new pathway for tunable catalytic activity of CO oxidation.

6.
Sci Total Environ ; 833: 155087, 2022 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-35421495

RESUMO

Chinese agricultural systems have experienced dramatic changes in crop planting area, cropping system, irrigation and fertilization managements, and crop yields in recent decades. These changes can substantially affect greenhouse gases (GHG) emissions and soil organic carbon (SOC) sequestration in croplands. However, the spatiotemporal patterns, as well as their driving factors and mechanisms, have not been well understood. Here, the Denitrification-Decomposition model is calibrated and validated to estimate nitrous oxide (N2O) and methane (CH4) emissions and SOC sequestration for seven major cropping systems in China during 2001-2020. The Logarithmic Mean Divisia Index method is further applied to attribute the net GHG emissions (NGEs) trend to various drivers. The results show that the total N2O emissions, CH4 emissions, and SOC sequestration were approximately 23.7, 182.0, and 177.6 Tg CO2-eq/year in the croplands across China. The national average NGEs per unit area ranged from -8705 to 8431 kg CO2-eq ha-1 year-1 across the major cropping systems. During 2001-2020, the trend in national annual NGEs was 0.66 kg CO2-eq ha-1 year-2, ranging from -78.9 to 82.2 kg CO2-eq ha-1 year-2 across the major cropping systems. The paddy lands were mainly a carbon source due to the large amount of CH4 emissions while the uplands could be a carbon sink owing to SOC sequestration. As a whole, the cropland in China was a carbon source with the NGEs equal to 28.4 Tg CO2-eq/year, and the NGEs increased by 0.047 Tg CO2-eq/year2 in the past 20 years. Nationally, changes in crop planting area and yields reduced the NGEs whereas changes in nitrogen use efficiency and cropping systems increased them, although the major factors and their impacts varied greatly among regions. Optimizing cropping systems and nitrogen fertilization based on the local genotype, environment and management should be the most effective method to reduce the NGEs in croplands.


Assuntos
Gases de Efeito Estufa , Agricultura/métodos , Carbono/análise , Dióxido de Carbono/análise , Sequestro de Carbono , China , Efeito Estufa , Metano/análise , Nitrogênio , Óxido Nitroso/análise , Solo
7.
Sci Total Environ ; 817: 153018, 2022 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-35026270

RESUMO

Cropland plays an important role in Soil Organic Carbon (SOC) sequestration. Although the SOC stock and its dynamic in the past decades have been extensively investigated, the information as to where, how much, and how SOC could be potentially sequestered in the coming decades has rarely been available. Here, the Rothamsted Carbon model was applied to investigate the spatiotemporal pattern of SOC sequestration potential for China's cropland in 2021-2040 at 1 km resolution, as well as the interactive impacts of climate change and agricultural management on SOC sequestration. Under the combined impacts of climate change and C input, the SOC sequestration of China's cropland in 2021-2040 would be about 0.56 Mg C ha-1 (0.06% yr-1), 1.33 Mg C ha-1 (0.15% yr-1), 2.10 Mg C ha-1 (0.24% yr-1), and 3.65 Mg C ha-1 (0.41% yr-1), with no increase, 5%, 10%, and 20% increase of C input, respectively. Therefore, a >20% increase in C input would be necessary to realize the promise of the '4 per 1000' initiative. Climate change would decrease SOC sequestration by 26.6-27.6 Tg yr-1 (or 60.4-62.7%). An increase of C input by 0%, 5%, 10%, and 20% relative to business as usual (BAU) would increase SOC sequestration by 4.8 (or 10.8%), 6.6 (or 14.9%), 13.1 (or 29.8%), and 26.2 (or 59.6%) Tg yr-1, respectively. The contributions of temperature, precipitation, and C input to SOC sequestration will be averagely 18.6%, 22.4%, and 59.0%, respectively. Our findings quantify the SOC sequestration in 2021-2040 at a high spatial resolution under the interactive impacts of climate change and agricultural management, which help to identify potential foci and develop region-specific measures to increase SOC sequestration efficiently.


Assuntos
Sequestro de Carbono , Solo , Agricultura , Carbono/análise , China , Mudança Climática , Produtos Agrícolas
8.
Nat Commun ; 12(1): 4094, 2021 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-34215747

RESUMO

Two-dimensional (2D) materials are promising for next-generation photo detection because of their exceptional properties such as a strong interaction with light, electronic and optical properties that depend on the number of layers, and the ability to form hybrid structures. However, the intrinsic detection ability of 2D material-based photodetectors is low due to their atomic thickness. Photogating is widely used to improve the responsivity of devices, which usually generates large noise current, resulting in limited detectivity. Here, we report a molybdenum-based phototransistor with MoS2 channel and α-MoO3-x contact electrodes. The device works in a photo-induced barrier-lowering (PIBL) mechanism and its double heterojunctions between the channel and the electrodes can provide positive feedback to each other. As a result, a detectivity of 9.8 × 1016 cm Hz1/2 W-1 has been achieved. The proposed double heterojunction PIBL mechanism adds to the techniques available for the fabrication of 2D material-based phototransistors with an ultrahigh photosensitivity.

9.
J Phys Condens Matter ; 33(20)2021 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-33690181

RESUMO

We report point-contact spectroscopy measurements on heavy fermion cousins CeCoIn5, Ce2PdIn8and Ce3PdIn11to systematically study the hybridization betweenfand conduction electrons. Below a temperatureT*, the spectrum of each compound exhibits an evolving Fano-like conductance shape, superimposed on a sloping background, that suggests the development of hybridization between localfand itinerant conduction electrons in the coherent heavy fermion state belowT*. We present a quantitative analysis of the conductance curves with a two-channel model to compare the tunneling process between normal metallic silver particles in our soft point-contact and heavy-fermion single crystals CeCoIn5, Ce2PdIn8and Ce3PdIn11.

10.
ACS Appl Mater Interfaces ; 13(5): 6156-6167, 2021 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-33507065

RESUMO

Li-CO2 batteries have recently attracted attention as promising candidates for next-generation energy storage devices due to their extremely high theoretical energy density. The real application of Li-CO2 cells involves addressing several drawbacks, including high charging potential, poor coulombic efficiency, and low rechargeability. Molybdenum disulfide supported on carbon nanotubes (MoS2/CNT) with various ratios functioned as a cathode catalyst for Li-CO2 batteries. The optimal MoS2/CNT composite achieved a maximum discharge capacity of 8551 mAh g-1 with a coulombic efficiency of 96.7%. This hybrid also obtained an initial charging plateau of 3.87 V at a current density of 100 mA g-1 with a cutoff capacity of 500 mAh g-1. It provided ideal electrochemical stability of 142 cycles at the current densities of 100 mA g-1, which was comparable with that of some precious metal catalysts. This optimized MoS2/CNT was also cycled at 200 and 400 mA g-1 for 112 and 55 times, respectively. Density functional theory calculations demonstrated that the sulfided Mo-edge (s-Mo-edge) on MoS2 materials showed appropriate adsorption strengths of Li, CO2, and Li2CO3. Moreover, joint results of Raman profiles and extended X-ray absorption fine structure spectra elucidated that the catalytic efficiencies of MoS2/CNT hybrids were proportional to the quantities of exposed s-Mo-edge active sites.

11.
Sci Total Environ ; 762: 143141, 2021 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-33121766

RESUMO

In response to the potential water conflict caused by climate change and increased population, an integrated water yield analysis from the perspective of the coupled human-natural system is clearly required. This paper conducted an integrated water yield analysis in the Yellow River basin (YRB), China, with applications for irrigated cropland water modeling and many field, statistical and satellite images. We found the following during 2000-2017: (1) The irrigation water consumption, rain-fed water consumption of cropland and rain-fed water consumption of natural ecosystems all increased significantly. (2) Ecological restoration caused a consequence of the 81.7 108 m3 water consumption transfer from cropland to natural ecosystems. (3) Water consumption variability was strongly related to irrigation expansion and ecological restoration, and this variability dominated the high water yield variability in the midstream YRB (95.73% ± 0.5%). (4) The increased downstream human water use stress was mainly affected by increased downstream water use and upstream water yield change, with contribution ratios of 1.67 and -0.72, respectively. The study declares the intense relationship between ecological restoration, crop production and socioeconomic activities within the water-limited river basin. This research also highlights that synthetic river basin management is essential to balance the water demand between different sectors and between the upper stream and downstream sections of a basin.

12.
Science ; 370(6516): 596-600, 2020 10 30.
Artigo em Inglês | MEDLINE | ID: mdl-33122384

RESUMO

Proton transport in nanochannels under humid conditions is crucial for the application in energy storage and conversion. However, existing materials, including Nafion, suffer from limited conductivity of up to 0.2 siemens per centimeter. We report a class of membranes assembled with two-dimensional transition-metal phosphorus trichalcogenide nanosheets, in which the transition-metal vacancies enable exceptionally high ion conductivity. A Cd0.85PS3Li0.15H0.15 membrane exhibits a proton conduction dominant conductivity of ~0.95 siemens per centimeter at 90° Celsius and 98% relative humidity. This performance mainly originates from the abundant proton donor centers, easy proton desorption, and excellent hydration of the membranes induced by cadmium vacancies. We also observed superhigh lithium ion conductivity in Cd0.85PS3Li0.3 and Mn0.77PS3Li0.46 membranes.

13.
Proc Natl Acad Sci U S A ; 117(42): 25991-25998, 2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-33020292

RESUMO

Graphene has emerged as an attractive candidate for flexible transparent electrode (FTE) for a new generation of flexible optoelectronics. Despite tremendous potential and broad earlier interest, the promise of graphene FTE has been plagued by the intrinsic trade-off between electrical conductance and transparency with a figure of merit (σDC/σOp) considerably lower than that of the state-of-the-art ITO electrodes (σDC/σOp <123 for graphene vs. ∼240 for ITO). Here we report a synergistic electrical/optical modulation strategy to simultaneously boost the conductance and transparency. We show that a tetrakis(pentafluorophenyl)boric acid (HTB) coating can function as highly effective hole doping layer to increase the conductance of monolayer graphene by sevenfold and at the same time as an anti-reflective layer to boost the visible transmittance to 98.8%. Such simultaneous improvement in conductance and transparency breaks previous limit in graphene FTEs and yields an unprecedented figure of merit (σDC/σOp ∼323) that rivals the best commercial ITO electrode. Using the tailored monolayer graphene as the flexible anode, we further demonstrate high-performance green organic light-emitting diodes (OLEDs) with the maximum current, power and external quantum efficiencies (111.4 cd A-1, 124.9 lm W-1 and 29.7%) outperforming all comparable flexible OLEDs and surpassing that with standard rigid ITO by 43%. This study defines a straightforward pathway to tailor optoelectronic properties of monolayer graphene and to fully capture their potential as a generational FTE for flexible optoelectronics.

14.
Environ Sci Technol ; 54(13): 7775-7786, 2020 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-32401498

RESUMO

A massive ecological restoration program has been implemented in northern China with the aim of protecting the Beijing-Tianjin-Hebei metropolitan area of eastern China from dust events. However, some current studies have cast doubt on the efficacy of such ecological restoration projects, partly due to the constraint of available water in northern China, leading to poor survival rates of planted trees in semiarid regions (15%). In this study, using a logical framework combining statistical analysis, partial least-squares path model analysis, and a regional climate model (RegCM) simulation with multisource dust indicators, we found that there was a reduction of dust in northern China that was synchronous with the increase in vegetation growth after ecological restoration. In contrast to previous reports of a decrease in wind speed due to ecological restoration, this study found that the increase in vegetation had an insignificant impact on local wind speed (p = 0.30). Instead, ecological restoration mainly reduced the sand emission in steppe area by improving the soil conditions of the underlying surface, and hence contributed 15% of the reduction of dust events in the Beijing-Tianjin-Hebei metropolitan area through dust transmission (p = 0.002). The effect of ecological restoration in the northern steppe on dust reduction over the northeastern metropolitan area of China should not be overstated.


Assuntos
Poeira , Solo , Pequim , China , Poeira/análise , Ecossistema , Vento
15.
Environ Sci Pollut Res Int ; 27(16): 19826-19835, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32222925

RESUMO

The climate change on the impact of grain production potential has significant regional differences. Researchers have studied the grain production potential of various crop combinations or focused on single crop types in a typical area; however, the regional differences of the climate change on the impact of grain production potential were neglected. This paper used the Global Agro-Ecological Zone (GAEZ 3.0) model to focus on the analysis what is the climate change on the impact of grain production potential in different geographic units (Northern Shaanxi Plateau, Guanzhong Basin, Qinba Mountain) in Shaanxi Province of China. The case showed that the precipitation (Pre) what made changes of grain production potential was the most important factor in different geographic units. The increase of Pre had a positive impact on the grain production potential in Northern Shaanxi Plateau and Guanzhong Basin. However, in Qinba Mountain, due to excessive Pre in the Qinba Mountains, the decrease of Pre had a certain positive impact on the grain production potential. The precipitation was less in the Northern Shaanxi Plateau; therefore, its major factors leading to changes of crop production were precipitation and rainfall days. The increase of the mean maximum temperature (Tmx) and the mean minimum temperature (Tmn) had a positive impact of the grain production potential in the Northern Shaanxi Plateau and Guanzhong Basin. The higher temperature had a negative impact on the grain production potential. In Qinba Mountain, the increase of the temperature has a certain negative impact on the grain production potential. It has more influence of Tmx in the Guanzhong Basin and Qinba Mountain rather than that in the Northern Shaanxi Plateau. Generally speaking, the major climatic factors leading grain production potential were Pre and Tmx in Guanzhong Basin and Qinba Mountain.


Assuntos
Mudança Climática , Grão Comestível , China , Produção Agrícola , Temperatura
16.
Chem Commun (Camb) ; 55(88): 13211-13214, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31599892

RESUMO

Slowing the dendrite formation process is one way to alleviate the fast capacity fade and safety issues in lithium metal battery systems. We used tetraethylene glycol dimethyl ether (TEGDME) as a complementary solvent to increase the desolvation activation energy of Li+, reduce the speed of lithium electrodeposition kinetics, and suppress dendrite formation. Density functional theory calculations combined with Raman spectroscopy indicate that a stronger coordination interaction is obtained between Li+ and TEGDME than between Li+ and 1,2-dimethoxyethane (DME) or 1,3-dioxolane (DOL). Such a strong coordination leads to a slower electrochemical reaction rate. As a result, uniform lithium electrodeposition morphology and good cycling stability of a Li|Li symmetric cell for more than 500 hours were achieved. Our approach suggests a way in which dendrite formation can be controlled by the electrochemical reaction itself.

17.
Nanoscale ; 11(43): 20777-20784, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31651925

RESUMO

Photocatalytic reduction of carbon monoxide (CO), an increasingly available and low-cost feedstock that could benefit from CO2 reduction, to high value-added multi-carbon chemicals, is significant for desirable carbon cycling, as well as high efficiency conversion and high density storage of solar energy. However, developing low cost but highly active photocatalysts with long-term stability for CO coupling and reduction remains a great challenge. Herein, by density functional theory (DFT) computations and taking advantage of the frustrated Lewis pairs (FLPs) concept, we identified a complex consisting of single boron (B) atom decorated on the optically active C2N monolayer (i.e., B/C2N) as an efficient and stable photocatalyst for CO reduction. On the designed B/C2N catalyst, CO can be efficiently reduced to ethylene (C2H4) and propylene (C3H6) both with a free energy increase of 0.22 eV for the potential-determining step, which greatly benefits from the pull-push function of the B-N FLPs composed of the decorating B atom and host N atoms. Moreover, the newly designed B/C2N catalyst shows significant visible light absorption with a suitable band position for CO reduction to C2H4 and C3H6. All these unique features make the B/C2N photocatalyst an ideal candidate for visible light driven CO reduction to high value-added multi-carbon fuels and chemicals.

18.
J Am Chem Soc ; 141(30): 12005-12010, 2019 07 31.
Artigo em Inglês | MEDLINE | ID: mdl-31276405

RESUMO

The peroxone reaction between O3 and H2O2 has been deemed a promising technology to resolve the increasingly serious water pollution problem by virtue of the generation of superactive hydroxyl radicals (•OH), but it suffers greatly from an extremely limited reaction rate constant under acidic conditions (ca. less than 0.1 M-1 s-1 at pH 3). This article describes a heterogeneous catalyst composed of single Mn atoms anchored on graphitic carbon nitride, which effectively overcomes such a drawback by altering the reaction pathway and thus dramatically promotes •OH generation in acid solution. Combined experimental and theoretical studies demonstrate Mn-N4 as the catalytically active sites. A distinctive catalytic pathway involving HO2• formation by the activation of H2O2 is found, which gets rid of the restriction of HO2- as the essential initiator in the conventional peroxone reaction. This work offers a new pathway of using a low-cost and easily accessible single-atom catalyst (SAC) and could inspire more catalytic oxidation strategies.

19.
Nat Commun ; 10(1): 2809, 2019 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-31243279

RESUMO

Large-area high-quality AB-stacked bilayer graphene films are highly desired for the applications in electronics, photonics and spintronics. However, the existing growth methods can only produce discontinuous bilayer graphene with variable stacking orders because of the non-uniform surface and strong potential field of the solid substrates used. Here we report the growth of wafer-scale continuous uniform AB-stacked bilayer graphene films on a liquid Pt3Si/solid Pt substrate by chemical vapor deposition. The films show quality, mechanical and electrical properties comparable to the mechanically exfoliated samples. Growth mechanism studies show that the second layer is grown underneath the first layer by precipitation of carbon atoms from the solid Pt, and the small energy requirements for the movements of graphene nucleus on the liquid Pt3Si enables the interlayer epitaxy to form energy-favorable AB stacking. This interlayer epitaxy also allows the growth of ABA-stacked trilayer graphene and is applicable to other liquid/solid substrates.

20.
ACS Appl Mater Interfaces ; 11(22): 20143-20149, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31070881

RESUMO

The use of red phosphors with low light-scattering loss could improve the luminous efficacy and color rendering of white-light-emitting diodes (LEDs). Thus, the discovery of such phosphors is highly desired. In this work, high-efficiency two-dimensional red-emitting K2TiF6:Mn4+ (KTFM) were synthesized via an alcohol-assisted coprecipitation route. The synergistic effects of 1-propanol and hydrofluoric acid on the growth of KTFM microsheets (MSs) were studied through the first-principles calculations, which revealed that 1-propanol promoted the growth of KTFM MSs by preferentially adsorbing on the H-terminated K2TiF6 (001) surface. The photoluminescence quantum efficiency (QE) of Mn4+-activated K2TiF6 MSs was highly related to their size and thickness. The morphology-optimal KTFM MSs presented high internal QE (>90%), external QE (>71%), and thermal quenching temperature (102% at 150 °C relative to that at 25 °C). A prototype phosphor-converted LED with KTFM as the red-emitting component showed excellent color rendition ( Ra = 91, R9 = 79) and high luminous efficacy (LE = 156 lm/w).

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...