Transition Metal Phosphide Nanoarchitectonics for Versatile Organic Catalysis

Transition metal phosphides (TMP) posses unique physiochemical, geometrical, and electronic properties, which can be exploited for different catalytic applications, such as photocatalysis, electrocatalysis, organic catalysis, etc. Among others, the use of TMP for organic catalysis is less explored and still facing many complex challenges, which necessitate the development of sustainable catalytic reaction protocols demonstrating high selectivity and yield of the desired molecules of high significance. In this regard, the controlled synthesis of TMP-based catalysts and thorough investigations of underlying reaction mechanisms can provide deeper insights toward practical achievement of desired applications. This review aims at providing a comprehensive analysis on the recent advancements in the synthetic strategies for the tailored and tunable engineering of structural, geometrical, and electronic properties of TMP. In addition, their unprecedented catalytic potential toward different organic transformation reactions is succinctly summarized and critically analyzed. Finally, a rational perspective on future opportunities and challenges in the emerging field of organic catalysis is provided. On the account of the recent achievements accomplished in organic synthesis using TMP, it is highly anticipated that the use of TMP combined with advanced innovative technologies and methodologies can pave the way toward large scale realization of organic catalysis.     

Moving Frontiers in Transition Metal Catalysis: Synthesis,Characterization and Modeling

Nanosized transition metal particles are important materials in catalysis with a key role not only in academic research but also in many processes with industrial and societal relevance. Although small improvements in catalytic properties can lead to significant economic and environmental impacts, it is only now that knowledge‐based design of such materials is emerging, partly because the understanding of catalytic mechanisms on nanoparticle surfaces is increasingly improving. A knowledge‐based design requires bottom‐up synthesis of well‐defined model catalysts, an understanding of the catalytic nanomaterials “at work” (operando), and both a detailed understanding and a prediction by theoretical methods. This article reports on progress in colloidal synthesis of transition metal nanoparticles for preparation of model catalysts to close the materials gap between the discoveries of fundamental surface science and industrial application. The transition metal particles, however, often undergo extensive transformations when applied to the catalytic process and much progress has recently been achieved operando characterization techniques under relevant reaction conditions. They allow better understanding of size/structure–activity correlations in these systems. Moreover, the growth of computing power and the improvement of theoretical methods uncover mechanisms on nanoparticles and have recently predicted highly active particles for CO/CO₂ hydrogenation or direct H₂O₂ synthesis.     

2D Early Transition Metal Carbides (MXenes) for Catalysis

MXenes, a bourgeoning class of 2D transition metal carbides, are of considerable interest in catalysis due to their rich surface chemistry, tunable electronic structures, and thermal stability. Here, recent conceptual advances in applying MXenes and their nanocomposites in (photo)electrocatalysis and conventional heterogeneous catalysis are highlighted. In addition, the nature of active sites in the MXene‐based catalysts are discussed and the significance and challenges in the future development of catalysts using MXenes as the platforms are summarized.     

Catalysis of a Single Transition Metal Site for Water Oxidation: From Mononuclear Molecules to Single Atoms

Low-cost, nonprecious transition metal (TM) catalysts toward efficient water oxidation are of critical importance to future sustainable energy technologies. The advances in structure engineering of water oxidation catalysts (WOCs) with single TM centers as active sites, for example, single metallic molecular complexes (SMMCs), supported SMMCs, and single-atom catalysts (SACs) in recent reports are examined. The efforts made on these configurations in terms of design principle, advanced characterization, performances and theoretical studies, are critically reviewed. A clear roadmap with the correlations between the single-TM-site-based structures (coordination and geometric structure, TM species, support), and the catalytic performances in water oxidation is provided. The insights bridging SMMCs with SACs are also given. Finally, the challenges and opportunities in the single-TM-site catalysis are proposed.     

Transition Metal and Rare-Earth Metal Doping in SnO2 Nanoparticles

Journal of Superconductivity and Novel Magnetism - Nanoparticles of tin oxide (SnO2) doped with iron oxide (α-Fe2O3) and Europium oxide (Eu2O3) were synthesized through the solid-state...     

Rational Design of Metal Nanoframes for Catalysis and Plasmonics

Recently, metal nanoframes have received increased attention due to their unique spatial and physicochemical, e.g., catalytic and plasmonic properties. So far, a variety of synthetic procedures have been developed to fabricate metal nanoframes with different shapes, sizes and compositions. Typical synthesis of metal nanoframes involves two stages: 1) formation of solid nanocrystals and 2) hollowing out the interiors and side faces. In this review, solution‐phase synthetic strategies are summarized, based on galvanic replacement reactions, oxidative etching, the Kirkendall effect, electrodeposition, and template‐assisted growth, as well as one‐pot synthesis. Their potential applications in catalysis and optical sensing are overviewed as well.     

五种二元过渡金属氧化物界面上的相互作用、非晶相结构及催化性能(Ⅱ)DSC、半导体气敏特性、催化活性与亚单层分散模型

应用DSC、半导体气敏特性、催化活性及亚单(分子)层分散模型共四项表征技术,进一步研究了五种二元氧化物的界面结构及其特性.DSC曲线的放热峰及吸热峰分别与界面化学反应、晶格畸变和瓦解、熔化、烧结以及固溶体的形成相关.导电性能的测试证明这些二元氧化物属于N-型半导体,对邻二甲苯具有气敏特性,其灵敏度在化学吸附的初期阶段与邻二甲苯蒸气浓度呈线性关系.催化选择性及转化率的测定证明V2O52MoOs及WO3-MoOs体系对邻二甲苯选择性氧化为苯酐具有催化活性,其非晶相MoOs及V2O5的活性较为显著,尤其当二元氧化物的组成接近分散阈值Dt时,选择性最佳.为了解释大的分散阈值Dt与小的比表面积之间的关系,经计算机编程计算,在分子水平及纳米尺度上提出了球形八面体密置的亚单层分散模型并求得了模型的七个参数.通过讨论亚单层分散与非晶相结构之间的关系,提出了晶相损失的机理以及作为催化剂的非晶相结构对热的亚稳特性.     

Mesoscale Charge-Ordering in Transition Metal Oxides: Formation and Signatures

We briefly outline the value of an inhomogeneous (unrestricted) Hartree–Fock plus Random Phase approach for understanding the types and properties of mesoscopic patterns of localized small polarons in transition metal oxides. Using a multiband Peierls–Hubbard model for a hole-doped CuO₂ layer as an illustrative example, we demonstrate the appearance of correlated high-energy (electronic) and low-energy (localized phonon and spin-wave) signatures of various vertical, diagonal, metal-centered, and oxygen-centered mesoscopic stripe patterns of localized holes (small polarons). This represents important inhomogeneous magneto-elastic coupling.     

Monolayer Transition Metal Dichalcogenides as Light Sources

Reducing the dimensions of materials is one of the key approaches to discovering novel optical phenomena. The recent emergence of 2D transition metal dichalcogenides (TMDCs) has provided a promising platform for exploring new optoelectronic device applications, with their tunable electronic properties, structural controllability, and unique spin valley–coupled systems. This progress report provides an overview of recent advances in TMDC‐based light‐emitting devices discussed from several aspects in terms of device concepts, material designs, device fabrication, and their diverse functionalities. First, the advantages of TMDCs used in light‐emitting devices and their possible functionalities are presented. Second, conventional approaches for fabricating TMDC light‐emitting devices are emphasized, followed by introducing a newly established, versatile method for generating light emission in TMDCs. Third, current growing technologies for heterostructure fabrication, in which distinct TMDCs are vertically stacked or laterally stitched, are explained as a possible means for designing high‐performance light‐emitting devices. Finally, utilizing the topological features of TMDCs, the challenges for controlling circularly polarized light emission and its device applications are discussed from both theoretical and experimental points of view.     

超高真空中使用的高纯过渡金属蒸发源

设计了一种超高真空使用的低电流过渡金属蒸发源 ,它能产生高纯金属原子束 ,且具有一定的寿命。该蒸发源是将过渡金属Co,Ni或Cr电镀到一个由W丝弯成的U形加热器上构成的。装入超高真空中 ,利用W丝自身的电阻加热 ,去气后 ,可获得数小时的清洁蒸发。实验结果表明 ,在离蒸发源约 5cm处 ,其淀积速率最高可达 1 0nm/min ,总的淀积厚度超过 5 0 0nm ,而且Auger分析结果显示 ,在超高真空中淀积的上述几种过渡金属薄膜 ,其纯度相当高 ,杂质含量均小于仪器的检测灵敏度。本文详细介绍了这种过渡金属蒸发源的制作技术及性能     

层状二硫化钼材料的制备和应用进展

二硫化钼(MoS2)是具有天然可调控带隙的二维层状材料,其独特的性质引起了科研人员的广泛关注,在微电子及光电领域具有重要的应用前景。介绍了MoS2的基本性质和常用制备方法,对层状MoS2材料在电子和光电子器件方面的应用进行了总结和展望。     

Dynamic Electronic Structure in Transition Metal Oxides

The isomer shift of La1-xCaxFeO3 decreases gradually from the value for trivalent iron to that for tetravalent iron, as the Ca content x increases from 0 to 1. This indicates that iron in La1.x-CaxFeO3 has an intermediate valence state. The intermediate valence state of iron increases gradually from trivalence to tetravalence. This can be interpreted as being due to electron delocalization among iron ions on identical octahedral sites. The Mossbauer spectra at various temperatures of La0.5Ca0.5FeO3 and their theoretical treatment show that electron delocalization slows down with decreasing temperature.     

Supported Noble‐Metal Single Atoms for Heterogeneous Catalysis

Single‐atom catalysts (SACs), with atomically distributed active metal sites on supports, serve as a newly advanced material in catalysis, and open broad prospects for a wide variety of catalytic processes owing to their unique catalytic behaviors. To construct SACs with precise structures and high density of accessible single‐atom sites, while preventing aggregation to large nanoparticles, various strategies for their chemical synthesis have been recently developed by improving the distribution and chemical bonding of active sites on supports, which results in excellent activity and selectivity in a variety of catalytic reactions. Noble‐metal‐based SACs are discussed, and their structural properties, chemical synthesis, and catalytic applications are highlighted. The structure–activity relationships and the underlying catalytic mechanisms are addressed, including the influences of surface species and reducibility of supports on the activity and stability, impact of the unique structural and electronic properties of single‐atom centers modulated by metal/support interactions on catalytic activity and selectivity, and how the modified catalytic mechanism obtained by inhibiting the multiatoms involves catalytic pathways. Finally, the prospects and challenges for development in this field are highlighted.     

2D Oxide Nanomaterials to Address the Energy Transition and Catalysis

2D oxide nanomaterials constitute a broad range of materials, with a wide array of current and potential applications, particularly in the fields of energy storage and catalysis for sustainable energy production. Despite the many similarities in structure, composition, and synthetic methods and uses, the current literature on layered oxides is diverse and disconnected. A number of reviews can be found in the literature, but they are mostly focused on one of the particular subclasses of 2D oxides. This review attempts to bridge the knowledge gap between individual layered oxide types by summarizing recent developments in all important 2D oxide systems including supported ultrathin oxide films, layered clays and double hydroxides, layered perovskites, and novel 2D‐zeolite‐based materials. Particular attention is paid to the underlying similarities and differences between the various materials, and the subsequent challenges faced by each research community. The potential of layered oxides toward future applications is critically evaluated, especially in the areas of electrocatalysis and photocatalysis, biomass conversion, and fine chemical synthesis. Attention is also paid to corresponding novel 3D materials that can be obtained via sophisticated engineering of 2D oxides.