Showing papers by "Yu Huang published in 2019"
TL;DR: In this paper, the authors presented the results from three gravitational-wave searches for coalescing compact binaries with component masses above 1 Ma during the first and second observing runs of the advanced GW detector network.
Abstract: We present the results from three gravitational-wave searches for coalescing compact binaries with component masses above 1 Ma™ during the first and second observing runs of the advanced gravitational-wave detector network. During the first observing run (O1), from September 12, 2015 to January 19, 2016, gravitational waves from three binary black hole mergers were detected. The second observing run (O2), which ran from November 30, 2016 to August 25, 2017, saw the first detection of gravitational waves from a binary neutron star inspiral, in addition to the observation of gravitational waves from a total of seven binary black hole mergers, four of which we report here for the first time: GW170729, GW170809, GW170818, and GW170823. For all significant gravitational-wave events, we provide estimates of the source properties. The detected binary black holes have total masses between 18.6-0.7+3.2 Mâ™ and 84.4-11.1+15.8 Mâ™ and range in distance between 320-110+120 and 2840-1360+1400 Mpc. No neutron star-black hole mergers were detected. In addition to highly significant gravitational-wave events, we also provide a list of marginal event candidates with an estimated false-alarm rate less than 1 per 30 days. From these results over the first two observing runs, which include approximately one gravitational-wave detection per 15 days of data searched, we infer merger rates at the 90% confidence intervals of 110-3840 Gpc-3 y-1 for binary neutron stars and 9.7-101 Gpc-3 y-1 for binary black holes assuming fixed population distributions and determine a neutron star-black hole merger rate 90% upper limit of 610 Gpc-3 y-1.
2,336 citations
TL;DR: The development, challenges and opportunities of van der Waals integration for flexible integration of diverse material systems beyond two dimensions are reviewed, and its potential for creating artificial heterostructures or superlattices beyond the reach of existing materials is discussed.
Abstract: Material integration strategies, such as epitaxial growth, usually involve strong chemical bonds and are typically limited to materials with strict structure matching and processing compatibility. Van der Waals integration, in which pre-fabricated building blocks are physically assembled together through weak van der Waals interactions, offers an alternative bond-free integration strategy without lattice and processing limitations, as exemplified by two-dimensional van der Waals heterostructures. Here we review the development, challenges and opportunities of this emerging approach, generalizing it for flexible integration of diverse material systems beyond two dimensions, and discuss its potential for creating artificial heterostructures or superlattices beyond the reach of existing materials.
809 citations
TL;DR: In this paper, the role of charge transport in electrochemical systems and 3D porous structures with a continuous conductive network for electron transport and a fully interconnected hierarchical porosity for ion transport are discussed, along with their ability to address charge transport limitations at high areal mass loading.
Abstract: The discovery and development of electrode materials promise superior energy or power density. However, good performance is typically achieved only in ultrathin electrodes with low mass loadings (≤1 mg cm−2) and is difficult to realize in commercial electrodes with higher mass loadings (>10 mg cm−2). To realize the full potential of these electrode materials, new electrode architectures are required that can allow more efficient charge transport beyond the limits of traditional electrodes. In this Review, we summarize the design and synthesis of 3D electrodes to address charge transport limitations in thick electrodes. Specifically, we discuss the role of charge transport in electrochemical systems and focus on the design of 3D porous structures with a continuous conductive network for electron transport and a fully interconnected hierarchical porosity for ion transport. We also discuss the application of 3D porous architectures as conductive scaffolds for various electrode materials to enable composite electrodes with an unprecedented combination of energy and power densities and then conclude with a perspective on future opportunities and challenges. 3D electrodes with interconnected and interpenetrating pathways enable efficient electron and ion transport. In this Review, the design and synthesis of such 3D electrodes are discussed, along with their ability to address charge transport limitations at high areal mass loading and to enable composite electrodes with an unprecedented combination of energy and power densities in electrochemical energy storage devices.
496 citations
TL;DR: A brief introduction of some fundamentals of fuel cells and ORR catalysts with performance metrics is provided, followed by a detailed description of a series of strategies for pushing the limit of high-performance Pt-based catalysts.
Abstract: Proton-exchange-membrane fuel cells (PEMFCs) are of considerable interest for direct chemical-to-electrical energy conversion and may represent an ultimate solution for mobile power supply. However, PEMFCs today are primarily limited by the sluggish kinetics of the cathodic oxygen reduction reaction (ORR), which requires a significant amount of Pt-based catalyst with a substantial contribution to the overall cost. Hence, promoting the activity and stability of the needed catalyst and minimizing the amount of Pt loaded are central to reducing the cost of PEMFCs for commercial deployment. Considerable efforts have been devoted to improving the catalytic performance of Pt-based ORR catalysts, including the development of various Pt nanostructures with tunable sizes and chemical compositions, controlled shapes with selectively displayed crystallographic surfaces, tailored surface strains, surface doping, geometry engineering, and interface engineering. Herein, a brief introduction of some fundamentals of fuel cells and ORR catalysts with performance metrics is provided, followed by a detailed description of a series of strategies for pushing the limit of high-performance Pt-based catalysts. A brief perspective and new insights on the remaining challenges and future directions of Pt-based ORR catalysts for fuel cells are also presented.
445 citations
TL;DR: In this paper, 1,3,7-trimethylxanthine, a commodity chemical with two conjugated carboxyl groups better known by its common name caffeine, improves the performance and thermal stability of perovskite solar cells.
389 citations
01 Jun 2019
TL;DR: In this article, a single-atom tailoring strategy was proposed to boost the activity of Pt nanocatalysts with minimal loss in surface active sites, and the single-nickel-atom-modified Pt nanowires with an optimum combination of specific activity and ECSA for the hydrogen evolution, methanol oxidation and ethanol oxidation reactions.
Abstract: Platinum-based nanocatalysts play a crucial role in various electrocatalytic systems that are important for renewable, clean energy conversion, storage and utilization. However, the scarcity and high cost of Pt seriously limit the practical application of these catalysts. Decorating Pt catalysts with other transition metals offers an effective pathway to tailor their catalytic properties, but often at the sacrifice of the electrochemical active surface area (ECSA). Here we report a single-atom tailoring strategy to boost the activity of Pt nanocatalysts with minimal loss in surface active sites. By starting with PtNi alloy nanowires and using a partial electrochemical dealloying approach, we create single-nickel-atom-modified Pt nanowires with an optimum combination of specific activity and ECSA for the hydrogen evolution, methanol oxidation and ethanol oxidation reactions. The single-atom tailoring approach offers an effective strategy to optimize the activity of surface Pt atoms and enhance the mass activity for diverse reactions, opening a general pathway to the design of highly efficient and durable precious metal-based catalysts.
381 citations
TL;DR: G-SACs that integrate the merits of heterogeneous catalysts and homogeneity, such as high activity, selectivity, stability, maximized atom utilization efficiency and easy separation from reactants/products are highlighted.
Abstract: Electrocatalysis plays an essential role in diverse electrochemical energy conversion processes that are vital for improving energy utilization efficiency and mitigating the aggravating global warming challenge. The noble metals such as platinum are generally the most frequently used electrocatalysts to drive these reactions and facilitate the relevant energy conversion processes. The high cost and scarcity of these materials pose a serious challenge for the wide-spread adoption and the sustainability of these technologies in the long run, which have motivated considerable efforts in searching for alternative electrocatalysts with reduced loading of precious metals or based entirely on earth-abundant metals. Of particular interest are graphene-supported single atom catalysts (G-SACs) that integrate the merits of heterogeneous catalysts and homogeneous catalysts, such as high activity, selectivity, stability, maximized atom utilization efficiency and easy separation from reactants/products. The graphene support features a large surface area, high conductivity and excellent (electro)-chemical stability, making it a highly attractive substrate for supporting single atom electrocatalysts for various electrochemical energy conversion processes. In this review, we highlight the recent advancements in G-SACs for electrochemical energy conversion, from the synthetic strategies and identification of the atomistic structure to electrocatalytic applications in a variety of reactions, and finally conclude with a brief prospect on future challenges and opportunities.
367 citations
TL;DR: Here Han et al. choose a polymer with proper molecular structure to crosslink the perovskite grains to greatly improve the device stability, and all photovoltaic parameters are significantly enhanced in the solar cells and the devices also show excellent stability.
Abstract: Manipulation of grain boundaries in polycrystalline perovskite is an essential consideration for both the optoelectronic properties and environmental stability of solar cells as the solution-processing of perovskite films inevitably introduces many defects at grain boundaries. Though small molecule-based additives have proven to be effective defect passivating agents, their high volatility and diffusivity cannot render perovskite films robust enough against harsh environments. Here we suggest design rules for effective molecules by considering their molecular structure. From these, we introduce a strategy to form macromolecular intermediate phases using long chain polymers, which leads to the formation of a polymer-perovskite composite cross-linker. The cross-linker functions to bridge the perovskite grains, minimizing grain-to-grain electrical decoupling and yielding excellent environmental stability against moisture, light, and heat, which has not been attainable with small molecule defect passivating agents. Consequently, all photovoltaic parameters are significantly enhanced in the solar cells and the devices also show excellent stability.
352 citations
TL;DR: This study designed and synthesized hyperbolic architectured ceramic aerogels with nanolayered double-pane walls with a negative Poisson’s ratio and a negative linear thermal expansion coefficient that display robust mechanical and thermal stability and are ideal for thermal superinsulation under extreme conditions, such as those encountered by spacecraft.
Abstract: Ceramic aerogels are attractive for thermal insulation but plagued by poor mechanical stability and degradation under thermal shock. In this study, we designed and synthesized hyperbolic architectured ceramic aerogels with nanolayered double-pane walls with a negative Poisson’s ratio (−0.25) and a negative linear thermal expansion coefficient (−1.8 × 10 −6 per °C). Our aerogels display robust mechanical and thermal stability and feature ultralow densities down to ~0.1 milligram per cubic centimeter, superelasticity up to 95%, and near-zero strength loss after sharp thermal shocks (275°C per second) or intense thermal stress at 1400°C, as well as ultralow thermal conductivity in vacuum [~2.4 milliwatts per meter-kelvin (mW/m·K)] and in air (~20 mW/m·K). This robust material system is ideal for thermal superinsulation under extreme conditions, such as those encountered by spacecraft.
352 citations
TL;DR: It is suggested that a better understanding of the reactant/intermediate adsorption, electron transfer, and desorption occurring at the electrolyte-electrode interface is necessary to fully comprehend these electrified surface reactions, and standardized membrane electrode assembly (MEA) testing protocols should be practiced, and data with full parameters detailed, for reliable evaluation of catalyst functions in devices.
Abstract: Currently, Pt-based electrocatalysts are adopted in the practical proton exchange membrane fuel cell (PEMFC), which converts the energy stored in hydrogen and oxygen into electrical power. However, the broad implementation of the PEMFC, like replacing the internal combustion engine in the present automobile fleet, sets a requirement for less Pt loading compared to current devices. In principle, the requirement needs the Pt-based catalyst to be more active and stable. Two main strategies, engineering of the electronic (d-band) structure (including controlling surface facet, tuning surface composition, and engineering surface strain) and optimizing the reactant adsorption sites are discussed and categorized based on the fundamental working principle. In addition, general routes for improving the electrochemical surface area, which improves activity normalized by the unit mass of precious group metal/platinum group metal, and stability of the electrocatalyst are also discussed. Furthermore, the recent progress of full fuel cell tests of novel electrocatalysts is summarized. It is suggested that a better understanding of the reactant/intermediate adsorption, electron transfer, and desorption occurring at the electrolyte-electrode interface is necessary to fully comprehend these electrified surface reactions, and standardized membrane electrode assembly (MEA) testing protocols should be practiced, and data with full parameters detailed, for reliable evaluation of catalyst functions in devices.
228 citations
01 Jan 2019
TL;DR: This review highlights the recent progress in the doping engineering of 2D MXs, covering that enabled by substitution, exterior charge transfer, intercalation and the electrostatic doping mechanism.
Abstract: Two-dimensional (2D) layered metal chalcogenides (MXs) have significant potential for use in flexible transistors, optoelectronics, sensing and memory devices beyond the state-of-the-art technology. To pursue ultimate performance, precisely controlled doping engineering of 2D MXs is desired for tailoring their physical and chemical properties in functional devices. In this review, we highlight the recent progress in the doping engineering of 2D MXs, covering that enabled by substitution, exterior charge transfer, intercalation and the electrostatic doping mechanism. A variety of novel doping engineering examples leading to Janus structures, defect curing effects, zero-valent intercalation and deliberately devised floating gate modulation will be discussed together with their intriguing application prospects. The choice of doping strategies and sources for functionalizing MXs will be provided to facilitate ongoing research in this field toward multifunctional applications.
TL;DR: This study provides a feasible strategy for air pollution control over g-C3N4 by introducing N-vacancy and porous tubular architecture simultaneously by combining detailed experimental characterization and density functional theory calculations.
Abstract: The development of catalysts that effectively activate target pollutants and promote their complete conversion is an admirable objective in the environmental photocatalysis field. In this work, graphitic carbon nitride (g-C3N4) microtubes with tunable N-vacancy concentrations were controllably fabricated using an in situ soft-chemical method. The morphological evolution of g-C3N4, from the bulk to the porous tubular architecture, is discussed in detail with the aid of time-resolved hydrothermal experiments. We found that the NO removal ratio and apparent reaction rate constant of the g-C3N4 microtubes were 1.8 and 2.6 times higher than those of pristine g-C3N4, respectively. By combining detailed experimental characterization and density functional theory calculations, the effects of N-vacancies in the g-C3N4 microtubes on O2 and NO adsorption activation, electron capture, and electronic structure were systematically investigated. These results demonstrate that surface N-vacancies act as specific sites for the adsorption activation of reactants and photoinduced electron capture, while enhancing the light-absorbing capability of g-C3N4. Moreover, the porous wall structures of the as-prepared g-C3N4 microtubes facilitate the diffusion of reactants, and their tubular architectures favor the oriented transfer of charge carriers. The intermediates formed during photocatalytic NO removal processes were identified by in situ diffuse reflectance infrared Fourier transform spectroscopy, and different reaction pathways over pristine and N-deficient g-C3N4 are proposed. This study provides a feasible strategy for air pollution control over g-C3N4 by introducing N-vacancy and porous tubular architecture simultaneously.
TL;DR: A comprehensive review of the continuing efforts in exploring semiconductor nanowires for the assembly of functional nanoscale electronics and macroelectronics, including a unique design of solution-processable nanowire thin-film transistors for high-performance large-area flexible electronics.
Abstract: Semiconductor nanowires have attracted extensive interest as one of the best-defined classes of nanoscale building blocks for the bottom-up assembly of functional electronic and optoelectronic devices over the past two decades. The article provides a comprehensive review of the continuing efforts in exploring semiconductor nanowires for the assembly of functional nanoscale electronics and macroelectronics. Specifically, we start with a brief overview of the synthetic control of various semiconductor nanowires and nanowire heterostructures with precisely controlled physical dimension, chemical composition, heterostructure interface, and electronic properties to define the material foundation for nanowire electronics. We then summarize a series of assembly strategies developed for creating well-ordered nanowire arrays with controlled spatial position, orientation, and density, which are essential for constructing increasingly complex electronic devices and circuits from synthetic semiconductor nanowires. Next, we review the fundamental electronic properties and various single nanowire transistor concepts. Combining the designable electronic properties and controllable assembly approaches, we then discuss a series of nanoscale devices and integrated circuits assembled from nanowire building blocks, as well as a unique design of solution-processable nanowire thin-film transistors for high-performance large-area flexible electronics. Last, we conclude with a brief perspective on the standing challenges and future opportunities.
TL;DR: In this paper, a 1.68-eV (FA0.65MA0.20Cs0.15)Pb(I0.8Br0.2)3 wide-band-gap perovskite solar cell with an efficiency of ∼20% enabled by using PEAI and Pb(SCN)2 complementary additive additive in the precursor.
TL;DR: It is shown that the alkaline HER/HOR kinetics can be unified by the catalytic roles of the adsorbed hydroxyl (OHad)-water-alkali metal cation (AM+) adducts, on the basis of the observations that enriching the OHad abundance via surface Ni benefits the HER/hOR; increasing the AM+ concentration only promotes the HER, while varying the identity of AM+ affects both HER and HOR.
Abstract: Despite the fundamental and practical significance of the hydrogen evolution and oxidation reactions (HER/HOR), their kinetics in base remain unclear. Herein, we show that the alkaline HER/HOR kinetics can be unified by the catalytic roles of the adsorbed hydroxyl (OHad)-water-alkali metal cation (AM+) adducts, on the basis of the observations that enriching the OHad abundance via surface Ni benefits the HER/HOR; increasing the AM+ concentration only promotes the HER, while varying the identity of AM+ affects both HER/HOR. The presence of OHad-(H2O)x-AM+ in the double-layer region facilitates the OHad removal into the bulk, forming OH–-(H2O)x-AM+ as per the hard–soft acid–base theory, thereby selectively promoting the HER. It can be detrimental to the HOR as per the bifunctional mechanism, as the AM+ destabilizes the OHad, which is further supported by the CO oxidation results. This new notion may be important for alkaline electrochemistry.
TL;DR: In this article, Z-scheme (BiO)2CO3-BiO2-x-graphene composite photocatalyst was designed for NO removal under simulated solar light irradiation.
Abstract: NO removal is one of the most important issues in dealing with air pollution In this report, Z-scheme (BiO)2CO3-BiO2-x-graphene (BOC-BiO2-x-GR) composite photocatalyst was designed for NO removal under simulated solar light irradiation Characterizations of physical properties of the ternary composites revealed extended light absorption and high efficient electron-hole separation Through the optimization of the BiO2-x content, we observed that the BOC-BiO2-x(35wt%)-GR composite exhibited superior photocatalytic activities in NO removal as compared to pure BOC, BiO2-x, and BOC-BiO2-x binary composites Detailed microstructural observation showed that the BOC-BiO2-x heterojunction was formed between BOC (013) and BiO2-x (111) planes The density of state (DOS) calculation revealed that due to the different hybridization conditions in the energy bands of BOC and BiO2-x, the Z-scheme charge transfer should be dominant at the heterojunction interface The density functional theory (DFT) computation on the Fermi level results confirmed that energy band structure between BOC and BiO2-x is more in favor of the transfer of photo-generated electrons from CB of BOC to the VB of BiO2-x, which can be further enhanced by highly conductive GR sheets The electron spin resonance (ESR) experiments results show that O2 − and HO were produced during the photocatalytic process, which further provided evidences that the BOC-BiO2-x(35wt%)-GR composite works as a Z-scheme photocatalyst This work indicates that Bi-based nanomaterials can be employed as a stable and high efficient solar light active photocatalyst for NO removal in air pollution control
TL;DR: A reconfigurable design enabled by locally tuning the doping of a 2D molybdenum disulfide film through the polarization of an underlying ferroelectric material is introduced.
Abstract: Ferroelectric engineered pn doping in two-dimensional (2D) semiconductors hold essential promise in realizing customized functional devices in a reconfigurable manner. Here, we report the successful pn doping in molybdenum disulfide (MoS2) optoelectronic device by local patterned ferroelectric polarization, and its configuration into lateral diode and npn bipolar phototransistors for photodetection from such a versatile playground. The lateral pn diode formed in this way manifests efficient self-powered detection by separating ~12% photo-generated electrons and holes. When polarized as bipolar phototransistor, the device is customized with a gain ~1000 by its transistor action, reaching the responsivity ~12 A W−1 and detectivity over 1013 Jones while keeping a fast response speed within 20 μs. A promising pathway toward high performance optoelectronics is thus opened up based on local ferroelectric polarization coupled 2D semiconductors. Photodetectors based on two dimensional (2D) materials still suffer from low performance. Here, the authors tackle this issue by introducing a reconfigurable design enabled by locally tuning the doping of a 2D molybdenum disulfide film through the polarization of an underlying ferroelectric material.
TL;DR: In this paper, a transparent composite film containing ultrathin protonated g-C3N4 (pCN) nanosheets and self-doped TiO2 nanoparticles was fabricated on glass at room temperature.
Abstract: Fabrication of photocatalysis films with good adhesion, hydrophilicity, and high activity on substrates at room temperature is essential for their application in air pollution control. Herein, functionalized transparent composite films containing ultrathin protonated g-C3N4 (pCN) nanosheets and Ti3+ self-doped TiO2 nanoparticles (pCN/TiO2) were fabricated on glass at room temperature. Thickness of the films measures 80 nm with surface roughness of 7.16 nm. The adhesion ability was attributed to the viscosity of TiO2 sol, which served as “chemical glue” in the films. The high photo-induced hydrophilicity demonstrated their self-cleaning potential. pCN/TiO2 films showed remarkably high visible-light-driven activity in terms of NO removal in a continuous-flow mode. Photoelectrochemical tests demonstrated the superior charge separation efficiency of pCN/TiO2 films compared with that of pristine TiO2. As identified by electron spin resonance spectra, O2− and OH radicals were the key reactive species involved in NO removal. The possible mechanism for photocatalytic NO oxidation was proposed. Potential cytotoxicity of pCN/TiO2 films was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay to ensure the biosecurity. This work provides a facile route to fabricate nanocomposite films under ambient temperature. The nanocomposite films were characterized by photo-induced hydrophilicity, high NO removal efficiency, and good biocompatibility, showing its potential in large-scale application.
01 Sep 2019
TL;DR: In this article, the development of van der Waals thin films and their use in high-performance large-area electronics is discussed, and the potential for application in large area wearable electronics and the challenges that exist in delivering practical devices are discussed.
Abstract: The development of emerging applications based on large-area flexible and wearable devices requires solution-processable thin-film electronics. Organic semiconductors can be processed in solution, but typically suffer from relatively low performance and insufficient stability in ambient conditions. Inorganic nanostructures, however, can be processed in solution while retaining the excellent electronic performance and structural stability of crystalline inorganic materials. In particular, a range of two-dimensional inorganic nanosheets can be dispersed in various solvents as stable colloidal inks. These nanosheets can be assembled into continuous thin films in which neighbouring sheets interact via van der Waals forces with few interfacial trapping states. The resulting tiled nanosheets, which we term two-dimensional van der Waals thin films, offer significant potential in thin-film electronics. Here we explore the development of van der Waals thin films and their use in high-performance large-area electronics. We examine the formulation of the nanosheet inks and their scalable assembly into van der Waals thin films and devices. We also consider their application in large-area wearable electronics and the challenges that exist in delivering practical devices. This Perspective explores the development of solution-processable van der Waals thin films, examining their potential for application in large-area wearable electronics and the challenges that exist in delivering practical devices.
TL;DR: It is demonstrated that the surface stacking faults and twin defects increase CO binding energy, leading to the enhanced CO2 RR performance on SD-Cu NPs, demonstrating a faradaic efficiency higher than commercial Cu NPs.
Abstract: The electrochemical carbon dioxide reduction reaction (CO_2RR) presents a viable approach to recycle CO_2 gas into low carbon fuels. Thus, the development of highly active catalysts at low overpotential is desired for this reaction. Herein, a high‐yield synthesis of unique star decahedron Cu nanoparticles (SD‐Cu NPs) electrocatalysts, displaying twin boundaries (TBs) and multiple stacking faults, which lead to low overpotentials for methane (CH_4) and high efficiency for ethylene (C_2H_4) production, is reported. Particularly, SD‐Cu NPs show an onset potential for CH_4 production lower by 0.149 V than commercial Cu NPs. More impressively, SD‐Cu NPs demonstrate a faradaic efficiency of 52.43% ± 2.72% for C_2H_4 production at −0.993 ± 0.0129 V. The results demonstrate that the surface stacking faults and twin defects increase CO binding energy, leading to the enhanced CO_2RR performance on SD‐Cu NPs.
TL;DR: The FGF21 signaling in adipose tissues is identified as an obligatory molecular transducer of exercise conferring its metabolic benefits in mice and sends humoral signals to coordinate multi-organ crosstalk for maintaining metabolic homeostasis.
TL;DR: This study highlights substantial heterogeneity in the patterns of eGFR decline among patients with diabetic kidney disease, and identifies associated clinical and genetic factors that may help to identify those who are more likely to experience an accelerated decline in kidney function.
TL;DR: In situ T EM studies of rechargeable ion batteries in a practical operation environment are explored, followed by applications of in situ TEM for direct observation of electrocatalyst formation, evolution, and degradation in proton-exchange membrane fuel cells, and fundamental investigations of new energy materials such as perovskites for solar cells are discussed.
Abstract: Energy devices such as rechargeable batteries, fuel cells, and solar cells are central to powering a renewable, mobile, and electrified future. To advance these devices requires a fundamental understanding of the complex chemical reactions, material transformations, and charge flow that are associated with energy conversion processes. Analytical in situ transmission electron microscopy (TEM) offers a powerful tool for directly visualizing these complex processes at the atomic scale in real time and in operando. Recent advancements in energy materials and devices that have been enabled by in situ TEM are reviewed. First, the evolutionary development of TEM nanocells from the open-cell configuration to the closed-cell, and finally the full-cell, is reviewed. Next, in situ TEM studies of rechargeable ion batteries in a practical operation environment are explored, followed by applications of in situ TEM for direct observation of electrocatalyst formation, evolution, and degradation in proton-exchange membrane fuel cells, and fundamental investigations of new energy materials such as perovskites for solar cells. Finally, recent advances in the use of environmental TEM and cryogenic electron microscopy in probing clean-energy materials are presented and emerging opportunities and challenges in in situ TEM research of energy materials and devices are discussed.
TL;DR: The Advanced Space-based Solar Observatory (ASO-S) is a mission proposed for the 25th solar maximum by the Chinese solar community as mentioned in this paper, where three payloads are deployed: the Full-disk vector MagnetoGraph (FMG), the Lyman-alpha Solar Telescope (LST) and the Hard X-ray Imager (HXI).
Abstract: The Advanced Space-based Solar Observatory (ASO-S) is a mission proposed for the 25th solar maximum by the Chinese solar community. The scientific objectives are to study the relationships between the solar magnetic field, solar flares and coronal mass ejections (CMEs). Three payloads are deployed: the Full-disk vector MagnetoGraph (FMG), the Lyman-alpha Solar Telescope (LST) and the Hard X-ray Imager (HXI). ASO-S will perform the first simultaneous observations of the photospheric vector magnetic field, non-thermal imaging of solar flares, and the initiation and early propagation of CMEs on a single platform. ASO-S is scheduled to be launched into a 720 km Sun-synchronous orbit in 2022. This paper presents an overview of the mission till the end of Phase-B and the beginning of Phase-C.
TL;DR: In this paper, a uniform Zn2+-doped BiOI microspheric microsphere was used for the photocatalytic removal of various harmful organic compounds.
Abstract: Highly exposed active facets and surface oxygen vacancies (OVs) are beneficial for the photocatalytic removal of various harmful organic compounds. In this study, uniform Zn2+-doped BiOI microspher...
TL;DR: Electrocatalytic studies demonstrate that Pt56Cu28Ni16 exhibits exceptional MOR and EOR specific activities and record high mass activity, comparing favorably with the best MOR or EOR Pt alloy-based catalysts reported to date.
Abstract: Direct methanol/ethanol alkaline fuel cells (DMAFCs/DEAFCs) represent an attractive mobile power generation technology. The methanol/ethanol oxidation reaction (MOR/EOR) often requires high-performance yet expensive Pt-based catalysts that may be easily poisoned. Herein, we report the development of PtCuNi tetrahedra electrocatalysts with optimized specific activity and mass activity for MOR and EOR. Our synthetic and structural characterizations show that these PtCuNi tetrahedra have Cu-rich core and PtNi-rich shell with tunable surface composition. Electrocatalytic studies demonstrate that Pt56Cu28Ni16 exhibits exceptional MOR and EOR specific activities of 14.0 ± 1.0 mA/cm2 and 11.2 ± 1.0 mA/cm2, respectively and record high mass activity of 7.0 ± 0.5 A/mgPt and 5.6 ± 0.6 A/mgPt, comparing favorably with the best MOR or EOR Pt alloy-based catalysts reported to date. Furthermore, we show that the unique core-shell tetrahedra configuration can also lead to considerably improved durability.
04 Dec 2019
TL;DR: In this paper, a third element (Cu) was added to octahedral PtNi nanoparticles during synthesis to improve their surface stability and activity, which can be attributed to increased surface Pt composition in as-synthesized catalysts, which suppresses the surface migration and subsequent dissolution of subsurface Cu and Ni atoms.
Abstract: Summary PtNi-based nanomaterials represent an emerging class of highly active catalysts for the oxygen reduction reaction (ORR) in fuel cells. However, they suffer from poor stability in operating conditions, which is the key challenge in maintaining their activity advantage over Pt in practice. We report significantly enhanced stability and activity of octahedral PtNi nanoparticles by tuning their surface elemental distribution through the introduction of a third element (Cu) during synthesis. To uncover the mechanism behind this observation, we performed kinetic Monte Carlo (KMC) simulations initialized using growth-tracking experiments and demonstrated that PtNiCu has improved Ni and Cu retention compared with PtNi, in agreement with experiments. The tracked movement of individual atoms in KMC reveals that the enhanced stability can be attributed to increased surface Pt composition in as-synthesized catalysts, which reduces the generation of surface vacancies and suppresses the surface migration and subsequent dissolution of subsurface Cu and Ni atoms.
TL;DR: The enhanced photocatalytic efficiency of 2%A-6%L-BOI photocatalyst is profited from the synergy of La ions doping, oxygen vacancy and the SPR effect of Au nanoparticles.
Abstract: Sphere-like Bi5O7I (BOI) doped with La (L-BOI) samples were prepared by a solvothermal method followed by calcination at 450 °C for 2 h. Au nanoparticles were loaded on 6% La-doped Bi5O7I (2%A-6%L-BOI) microspheres by a room-temperature chemical reduction method. The UV-vis absorption spectra show that the L-BOI and 2%A-6%L-BOI samples have a strong visible-light absorption in comparison with the pure BOI. The electron paramagnetic resonance results indicate that the number of oxygen vacancies in L-BOI samples is increased with an increasing amount of the La dopant. The band structure of the prepared photocatalysts is investigated by confirming the positions of the valence band (VB) measured by XPS-VB and the Fermi level computed by density functional theory, respectively. NO is selected as a target gaseous pollutant to confirm the influence of La doping and the plasmonic effect of Au nanoparticles on the photocatalytic activity of BOI microspheres. The 2%A-6%L-BOI sample exhibits an enhanced photocatalytic performance compared to BOI, L-BOI, and A-BOI photocatalysts under visible-light irradiation. Interestingly, the 2%A-6%L-BOI sample also can reduce the amount of intermediate NO2 during the NO removal process. The enhanced photocatalytic efficiency of the 2%A-6%L-BOI photocatalyst is profited from the synergy of La-ion doping, oxygen vacancy, and the surface plasmon resonance effect of Au nanoparticles. Based on the results of trapping experiments and electron spin resonance spectroscopy tests, h+, e-, and •O2- were involved in the NO oxidative removal.
TL;DR: In this article, multi-site doping of Sr improved the NO removal rate by 1.5 times and the conversion rate of secondary pollution (NO2) decreased from 62.5% to 15.8%.
Abstract: The NO removal activity of g-C3N4 is limited by many shortcomings including the high recombination rate of photo-generated carriers and secondary pollution induced by incomplete oxidation. Here, we modified g-C3N4 using multi-site Sr-doping with simultaneous N atoms replacement, cavity padding, and intercalation. The NO removal experiments showed that multi-site doping of Sr improved the NO removal rate by 1.5 times. Meanwhile, the conversion rate of secondary pollution (NO2) decreased from 62.5% to 15.8%. The effects of doped Sr were different with different doping modes. All the doping modals of Sr could decrease the band gap of g-C3N4. Meanwhile, the Sr that intercalated in the interlayer of g-C3N4 could improve the transfer of photogenerated electrons; the Sr that replaced the N atoms could help the activation of O2 to produce more O2−; the Sr padded in the cavity provides g-C3N4 with the ability to activate the H2O2 for the generation of a stronger oxidant ( OH). The different doping modes complement each other and combine to realize efficient and deep NO removal.
TL;DR: The noncovalent van der Waals interface between C8-BTBT and BP effectively preserves the intrinsic properties of BP, allowing us to demonstrate high-performance BP FETs with a record-high current density, hole drift velocity, and on/off ratio at room temperature.
Abstract: Two-dimensional layered materials (2DLMs) are of considerable interest for high-performance electronic devices for their unique electronic properties and atomically thin geometry. However, the atomically thin geometry makes their electronic properties highly susceptible to the environment changes. In particular, some 2DLMs (e.g., black phosphorus (BP) and SnSe2) are unstable and could rapidly degrade over time when exposed to ambient conditions. Therefore, the development of proper passivation schemes that can preserve the intrinsic properties and enhance their lifetime represents a key challenge for these atomically thin electronic materials. Herein we introduce a simple, nondisruptive, and scalable van der Waals passivation approach by using organic thin films to simultaneously improve the performance and air stability of BP field-effect transistors (FETs). We show that dioctylbenzothienobenzothiophene (C8-BTBT) thin films can be readily deposited on BP via van der Waals epitaxy approach to protect BP against oxidation in ambient conditions over 20 d. Importantly, the noncovalent van der Waals interface between C8-BTBT and BP effectively preserves the intrinsic properties of BP, allowing us to demonstrate high-performance BP FETs with a record-high current density of 920 μA/um, hole drift velocity over 1 × 107 cm/s, and on/off ratio of 1 × 104 to ∼1 × 107 at room temperature. This approach is generally applicable to other unstable two-dimensional materials, defining a unique pathway to modulate their electronic properties and realize high-performance devices through hybrid heterojunctions.