Electrocatalytic energy conversion has been considered as one of the most efficient and promising pathways for realizing energy storage and energy utilization in modern society. To improve ...electrocatalytic reactions, specific catalysts are needed to lower the overpotential. In the search for efficient alternatives to noble metal catalysts, transition metal nitrides have attracted considerable interest due to their high catalytic activity and unique electronic structure. Over the past few decades, numerous nitride‐based catalysts have been explored with respect to their ability to drive various electrocatalytic reactions, such as the hydrogen evolution reaction and the oxygen evolution reaction to achieve water splitting and the oxygen reduction reaction coupled with the methanol oxidation reaction to construct fuel cells or rechargeable Li‐O2 batteries. This Minireview provides a brief overview of recent progress on electrocatalysts based on transition metal nitrides, and outlines the current challenges and future opportunities.
Transition metal nitrides have emerged as one kind of efficient electrocatalyst for driving various reactions for energy conversion. This Minireview highlights the major progress made recently in this field, and provides a critical discussion of the current challenges and future opportunities for designing and optimizing advanced nitride‐based electrocatalysts.
Investigating tellurium (Te) corrosion on structural materials is crucial for sodium-cooled fast reactors (SFRs) due to radionuclide presence and knowledge gaps. In this study, Type 304/304L ...stainless steel (SS304), chromium (Cr), iron (Fe), and nickel (Ni) samples were immersed in low-oxygen environments with Te in liquid sodium at 773 K for 30 days. At 10 ppm oxygen, SS304 showed multiple oxide layers, including a compact NaCrO2 interlayer and porous Na-Fe-Ni-O outer layers. Tellurium penetrated through the porous layers but was hindered by the NaCrO2 interlayer. At 0.01 ppm oxygen, Cr had no oxide layer, while Fe and Ni had unstable ones. Tellurium-induced pitting was deeper in Fe and Ni compared to Cr. Oxygen levels and Cr composition are critical factors affecting stable oxide compound layer formation and mitigating Te-induced pitting.
Among the various energy storage systems, the rechargeable Zn-air battery is one of the most promising candidates for the consumer electronic market and portable energy sources. In a Zn-air battery, ...surface/interface chemistry plays a key role in their performance optimization of power density, stability and rechargeable efficiency. A Zn-air battery requires gas-involved ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) reactions, always leading to complex reactions and sluggish kinetic processes at the three-phase interface, in which rational surface/interface nanoengineering at the micro and meso-level play a decisive role. In this review, we cover the influence of surface/interface properties of electrocatalysts and air electrodes on the performance of rechargeable Zn-air batteries, and the latest surface/interface nanoengineering progress from the micro to meso-level is surveyed. Moreover, the surface/interface characteristics of electrocatalysts and air electrodes at the triple-phase interface, which are closely related to the four key parameters of electrical conductivity, reaction energy barrier, reaction surface area and mass transfer behavior, are also described in detail. Based on the discussion of the latest achievements of surface/interface nanoengineering, some personal perspectives on future advanced development of rechargeable Zn-air batteries are presented as well.
Surface/interface nanoengineering of electrocatalysts and air electrodes will promote the rapid development of high-performance rechargeable Zn-air batteries.
Catalysis can speed up chemical reactions and it usually occurs on the low coordinated steps, edges, terraces, kinks and corner atoms that are often called "active sites". However, the atomic level ...interplay between active sites and catalytic activity is still an open question, owing to the large difference between idealized models and real catalysts. This stimulates us to pursue a suitable material model for studying the active sites-catalytic activity relationship, in which the atomically-thin two-dimensional sheets could serve as an ideal model, owing to their relatively simple type of active site and the ultrahigh fraction of active sites that are comparable to the overall atoms. In this tutorial review, we focus on the recent progress in disclosing the factors that affect the activity of reactive sites, including characterization of atomic coordination number, structural defects and disorder in ultrathin two-dimensional sheets by X-ray absorption fine structure spectroscopy, positron annihilation spectroscopy, electron spin resonance and high resolution transmission electron microscopy. Also, we overview their applications in CO catalytic oxidation, photocatalytic water splitting, electrocatalytic oxygen and hydrogen evolution reactions, and hence highlight the atomic level interplay among coordination number, structural defects/disorder, active sites and catalytic activity in the two-dimensional sheets with atomic thickness. Finally, we also present the major challenges and opportunities regarding the role of active sites in catalysis. We believe that this review provides critical insights for understanding the catalysis and hence helps to develop new catalysts with high catalytic activity.
Atomically-thin two-dimensional sheets can serve as an ideal model to disclose the role of active sites in catalysis.
CO2 conversion to chemical fuels through photoreduction, electroreduction, or thermoreduction is considered as one of the most effective methods to solve environmental pollution and energy shortage ...problems. However, recent studies show that the involved catalysts may undergo continuous reconstruction under realistic working conditions, which unfortunately causes controversial results concerning the active sites and reaction mechanism of CO2 reduction. Thus, it is necessary, while challenging, to monitor in real time the dynamic evolution of the catalysts and reaction intermediates by in situ techniques under experimental conditions. In this Perspective, we start with the working principle and detection modes of various in situ characterization techniques. Subsequently, we systematically summarize the recent developments of in situ studies on probing the catalyst evolution during the CO2 reduction process. We further focus on the progress of in situ studies in monitoring the reaction intermediates and catalytic products, in which we also highlight how the theoretical calculations are combined to reveal the reaction mechanism in detail. Finally, based on the achievements in the representative studies, we present some prospects and suggestions for in situ studies of CO2 reduction in the future.
Evolutionary Structural Optimization (ESO) and its later version bi-directional ESO (BESO) have gained widespread popularity among researchers in structural optimization and practitioners in ...engineering and architecture. However, there have also been many critical comments on various aspects of ESO/BESO. To address those criticisms, we have carried out extensive work to improve the original ESO/BESO algorithms in recent years. This paper summarizes latest developments in BESO for stiffness optimization problems and compares BESO with other well-established optimization methods. Through a series of numerical examples, this paper provides answers to those critical comments and shows the validity and effectiveness of the evolutionary structural optimization method.
Nitrogen-containing compounds like ammonia (NH
3
) and nitrates are essential materials for modern fertilizers, medicines, fibers, explosives,
etc.
, which are closely relevant to the development of ...human society. However, the widely used conventional Haber-Bosh process for the synthesis of ammonia requires high temperature and energy over a long period of time. In recent decades, the photocatalytic nitrogen fixation process has been demonstrated to be a low-energy consuming and sustainable approach to produce nitrogen-containing compounds, which has attracted extensive attention. Currently, the strategies for the development of efficient photocatalysts for nitrogen fixation are primarily concentrated on creating active sites by introducing defects into the photocatalysts to activate the adsorbed N
2
by weakening the N&z.tbd;N triple bond, facilitate the charge separation and accelerate charge carrier transfer from photocatalysts to the adsorbed reactants. In this review, we summarize the recent developments in photocatalysts with various defects for nitrogen fixation. First, we discuss the reaction mechanisms of the photocatalytic nitrogen fixation process. Second, several categories of defects corresponding to their related element compositions are investigated. Then, the theoretical and the computational survey on defects in nitrogen fixation photocatalysts are also presented. Finally, the existing challenges, opportunities and future prospects in this burgeoning area are discussed.
This review summarizes the recent experimental and theoretical progress of various defects in catalysts for high nitrogen photofixation performance.
Recently developed CsPbX3 (X = Cl, Br, and I) perovskite quantum dots (QDs) hold great potential for various applications owing to their superior optical properties, such as tunable emissions, high ...quantum efficiency, and narrow linewidths. However, poor stability under ambient conditions and spontaneous ion exchange among QDs hinder their application, for example, as phosphors in white‐light‐emitting diodes (WLEDs). Here, a facile two‐step synthesis procedure is reported for luminescent and color‐tunable CsPbX3–zeolite‐Y composite phosphors, where perovskite QDs are encapsulated in the porous zeolite matrix. First zeolite‐Y is infused with Cs+ ions by ion exchange from an aqueous solution and then forms CsPbX3 QDs by diffusion and reaction with an organic solution of PbX2. The zeolite encapsulation reduces degradation and improves the stability of the QDs under strong illumination. A WLED is fabricated using the resulting microscale composites, with Commission Internationale de I'Eclairage (CIE) color coordinates (0.38, 0.37) and achieving 114% of National Television Standards Committee (NTSC) and 85% of the ITU‐R Recommendation BT.2020 (Rec.2020) coverage.
A synthesis procedure for luminescent perovskite quantum dots embedded in zeolite‐Y crystals is presented. The structural and optical properties of the resulting composites are characterized in detail. Zeolite embedding improves the stability of perovskite quantum dots to degradation. Finally, the composites are used to produce a white‐light‐emitting diode with wide color gamut.
Flat Boron: A New Cousin of Graphene Xie, Sheng‐Yi; Wang, Yeliang; Li, Xian‐Bin
Advanced materials (Weinheim),
09/2019, Letnik:
31, Številka:
36
Journal Article
Recenzirano
The mechanical exfoliation of graphene from graphite provides the cornerstone for the synthesis of other 2D materials with layered bulk structures, such as hexagonal boron nitride, transition metal ...dichalcogenides, black phosphorus, and so on. However, the experimental production of 2D flat boron is challenging because bulk boron has very complex spatial structures and a rich variety of chemical properties. Therefore, the realization of 2D flat boron marks a milestone for the synthesis of 2D materials without layered bulk structures. The historical efforts in this field, particularly the most recent experimental progress, such as the growth of 2D flat boron on a metal substrate by chemical vapor deposition and molecular beam epitaxy, or liquid exfoliation from bulk boron, are described.
The successful synthesis of borophene on metal substrates marks a milestone for the synthesis of 2D materials without layered bulk structures, just as graphene is the cornerstone for synthesizing 2D materials with layered bulk structures. The exotic properties and wide applications of borophene make it a new cousin of graphene in the family of 2D materials.
We investigate the weak and strong deflection gravitational lensing by a quantum deformed Schwarzschild black hole and find their observables. These lensing observables are evaluated and the ...detectability of the quantum deformation is assessed, after assuming the supermassive black holes Sgr A* and M87* respectively in the Galactic Center and at the center of M87 as the lenses. We also intensively compare these findings with those of a renormalization group improved Schwarzschild black hole and an asymptotically safe black hole. We find that, among these black holes, it is most likely to test the quantum deformed Schwarzschild black hole via its weak deflection lensing observables in the foreseen future.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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