Bimetallic nanocrystals (NCs) with core/shell, heterostructure, or intermetallic and alloyed structures are emerging as more important materials than monometallic NCs. They are expected to display ...not only a combination of the properties associated with two distinct metals, but also new properties and capabilities due to a synergy between the two metals. More importantly, bimetallic NCs usually show composition‐dependent surface structure and atomic segregation behavior, and therefore more interesting applied potentials in various fields including electronics, engineering, and catalysis. Compared with monometallic NCs, preparation of bimetallic NCs is much more complicated and difficult to be achieved. In recent years, researchers from many groups have made great efforts in this area. This review highlights the recent progress in the chemical synthesis of bimetallic NCs. The control over morphology, size, composition, and structure of bimetallic NCs as well as the exploration of their properties and applications are discussed.
Bimetallic nanocrystals with core/shell, heterostructure, or intermetallic and alloyed structures are attracting more and more attention from researchers. They display not only a combination of properties associated with two distinct metals, but also new properties, and therefore have significant applications in various fields. This paper reviews the recent progress in liquid‐phase synthesis of bimetallic nanocrystals and their catalytic applications.
The development of efficient and cost-effective catalysts to catalyze a wide variety of electrochemical reactions is key to realize the large-scale application of renewable and clean energy ...technologies. Owing to the maximum atom-utilization efficiency and unique electronic and geometric structures, single atom catalysts (SACs) have exhibited superior performance in various catalytic systems. Recently, assembled from the functionalized organic linkers and metal nodes, metal-organic frameworks (MOFs) with ultrafine porosity have received tremendous attention as precursors or self-sacrificing templates for preparing porous SACs. Here, the recent advances toward the synthesis strategies for using MOF precursors/templates to construct SACs are systematically summarized with special emphasis on the types of central metal sites. The electrochemical applications of these recently emerged MOF-derived SACs for various energy-conversion processes, such as oxygen reduction/evolution reaction (ORR/OER), hydrogen evolution reaction (HER), and CO
2
reduction reaction (CO
2
RR), are also discussed and reviewed. Finally, the current challenges and prospects regarding the development of MOF-derived SACs are proposed.
The local coordination environment of catalysts has been investigated for an extended period to obtain enhanced catalytic performance. Especially with the advancement of single-atom catalysts (SACs), ...research on the coordination environment has been advanced to the atomic level. The surrounding coordination atoms of central metal atoms play important roles in their catalytic activity, selectivity and stability. In recent years, remarkable improvements of the catalytic performance of SACs have been achieved by the tailoring of coordination atoms, coordination numbers and second- or higher-coordination shells, which provided new opportunities for the further development of SACs. In this review, the characterization of coordination environment, tailoring of the local coordination environment, and their related adjustable catalytic performance will be discussed. We hope this review will provide new insights on further research of SACs.
Abstract
Supported atomic clusters with uniform metal sites and definite low-nuclearity are intermediate states between single-atom catalysts (SACs) and nanoparticles in size. Benefiting from the ...presence of metal–metal bonds, supported atomic clusters can trigger synergistic effects among every metal atom, which contributes to achieving unique catalytic properties different from SACs and nanoparticles. However, the scalable and precise synthesis and atomic-level insights into the structure–properties relationship of supported atomic clusters is a great challenge. This perspective presents the latest progress of the synthesis of supported atomic clusters, highlights how the structure affects catalytic properties, and discusses the limitations as well as prospects.
Single‐atom materials (SAMs) have been widely investigated during the past years, providing many high‐performance materials applied in catalyst, battery, solar cell, and so on. The high performance ...that SAM exhibit is largely attributed to the microstructure inside the SAM. It is thus essential to realize the goal of regulating the structures, as the chemists wish and deeply comprehend the relationship between the macroproperties and the small structures. However, the concerns above are far from realization and more efforts are necessary to be put into this field. Herein, the regulation on microstructures, the characterization on the microstructures and the relationship between the macroproperties and the small structures are comprehensively summarized and discussed, which are mainly based on the application of SAM in catalyst. Based on the basic information earlier, the challenge and future development of SAM are also proposed, aiming to emerge an overall view and guideline to the research on the next step.
The single‐atom materials (SAMs) have been explored intensely, but there are still many barriers needed to overcome, which hold back the practical use of SAM. Herein, the main barriers and opportunities are discussed, aiming to provide a guideline for the research on the next step.
Abstract
The search for constructing high-performance catalysts is an unfailing topic in chemical fields. Recently, we have witnessed many breakthroughs in the synthesis of single-atom catalysts ...(SACs) and their applications in catalytic systems. They have shown excellent activity, selectivity, stability, efficient atom utilization and can serve as an efficient bridge between homogeneous and heterogenous catalysis. Currently, most SACs are synthesized via a bottom-up strategy; however, drawbacks such as the difficulty in accessing high mass activity and controlling homogeneous coordination environments are inevitably encountered, restricting their potential use in the industrial area. In this regard, a novel top-down strategy has been recently developed to fabricate SACs to address these practical issues. The metal loading can be increased to 5% and the coordination environments can also be precisely controlled. This review highlights approaches to the chemical synthesis of SACs towards diverse chemical reactions, especially the recent advances in improving the mass activity and well-defined local structures of SACs. Also, challenges and opportunities for the SACs will be discussed in the later part.
The rational design of metal–organic frameworks (MOFs) with hollow features and tunable porosity at the nanoscale can enhance their intrinsic properties and stimulates increasing attentions. In this ...Communication, we demonstrate that methanol can affect the coordination mode of ZIF‐67 in the presence of Co2+ and induces a mild phase transformation under solvothermal conditions. By applying this transformation process to the ZIF‐67@ZIF‐8 core–shell structures, a well‐defined hollow Zn/Co ZIF rhombic dodecahedron can be obtained. The manufacturing of hollow MOFs enables us to prepare a noble metal@MOF yolk‐shell composite with controlled spatial distribution and morphology. The enhanced gas storage and porous confinement that originate from the hollow interior and coating of ZIF‐8 confers this unique catalyst with superior activity and selectivity toward the semi‐hydrogenation of acetylene.
A mild phase transformation of ZIF‐67@ZIF‐8 core–shell structures is achieved under solvothermal conditions to generate unique hollow Zn/Co ZIF particles, which were used to generate Pd@MOF yolk‐shell composites. They exhibit enhanced gas storage and high catalytic activity and selectivity in the semi‐hydrogenation of acetylene.
Understanding the site interaction nature of single‐atom catalysts (SACs), especially densely populated SACs, is vital for their application to various catalytic reactions. Herein, we report a site ...distance effect, which emphasizes how well the distance of the adjacent copper atoms (denoted as dCu1−Cu1) matches with the reactant peroxydisulfate (PDS) molecular size to determine the Fenton‐like reaction reactivity on the carbon‐supported SACs. The optimized dCu1−Cu1 in the range of 5–6 Å, which matches the molecular size of PDS, endows the catalyst with a nearly two times higher turnover frequency than that of dCu1−Cu1 beyond this range, accordingly achieving record‐breaking kinetics for the oxidation of emerging organic contaminants. Further studies suggest that this site distance effect originates from the alteration of PDS adsorption to a dual‐site structure on Cu1−Cu1 sites when dCu1−Cu1 falls within 5–6 Å, significantly enhancing the interfacial charge transfer and consequently resulting in the most efficient catalyst for PDS activation so far.
Site distance effects are important in a Cu1/N‐doped graphene (Cu1/GN) single‐atom catalyst with record‐breaking kinetics in the oxidation of emerging organic pollutants. A strategy is reported to achieve the desired catalyst behavior by matching the active site with the properties of the reaction molecule peroxydisulfate (PDS).
Today, Pt/C catalysts are widely used in proton exchange membrane fuel cells (PEMFCs). The practical applications of PEMFCs still face many limitations in the preparation of advanced Pt‐based ...catalysts, including high cost, limited life‐time, and insufficient power density. A kinetically sluggish oxygen reduction reaction (ORR) is primarily responsible for these issues. The development of advanced Pt‐based catalysts is crucial for solving these problems when the large‐scale application of PEMFCs is to be realized. Herein, we demonstrate the design principle of advanced Pt‐based catalysts with an emphasis on theoretical understandings to practical applications. Generally, three main strategies (including strain effect, electronic effect, and ensemble effect) that governing the initial activity of Pt‐based electrocatalysts are elaborated in detail in this review. Recent advanced Pt‐based ORR catalysts are summarized and we present representative achievements to further reveal the relationship of excellent ORR performance based on theoretical mechanisms. Then we focus on the preparation standards of membrane electrode assembles and testing protocols in practice. Finally, we predict the remaining challenges and present our perspectives with regards to design strategies for improving ORR performance of Pt‐based catalysts in the future.
The development of advanced Pt‐based catalysts is crucial for solving these problems if the large‐scale application of proton exchange membrane fuel cells (PEMFCs) is to be realized. Thus, a comprehensive understanding of the fundamental principle and design strategy is of great importance for advancing new generation Pt‐based nanocatalysts.
Currently, more than 86% of global energy consumption is still mainly dependent on traditional fossil fuels, which causes resource scarcity and even emission of high amounts of carbon dioxide (CO2), ...resulting in a severe “Greenhouse effect.” Considering this situation, the concept of “carbon neutrality” has been put forward by 125 countries one after another. To achieve the goals of “carbon neutrality,” two main strategies to reduce CO2 emissions and develop sustainable clean energy can be adopted. Notably, these are crucial for the synthesis of advanced single‐atom catalysts (SACs) for energy‐related applications. In this review, we highlight unique SACs for conversion of CO2 into high‐efficiency carbon energy, for example, through photocatalytic, electrocatalytic, and thermal catalytic hydrogenation technologies, to convert CO2 into hydrocarbon fuels (CO, CH4, HCOOH, CH3OH, and multicarbon C2+ products). In addition, we introduce advanced energy conversion technologies and devices to replace traditional polluting fossil fuels, such as photocatalytic and electrocatalytic water splitting to produce hydrogen energy and a high‐efficiency oxygen reduction reaction (ORR) for fuel cells. Impressively, several representative examples of SACs (including d‐, ds‐, p‐, and f‐blocks) for CO2 conversion, water splitting to H2, and ORR are discussed to describe synthesis methods, characterization, and corresponding catalytic activity. Finally, this review concludes with a description of the challenges and outlooks for future applications of SACs in contributing toward carbon neutrality.
Good progress has been achieved in research on single‐atom catalysts (SACs) with nearly 100% atom utilization in terms of energy conversion and utilization involved in the process of “carbon neutrality.” Herein, SACs, including d‐, ds‐, p‐, and f‐blocks, for CO2 conversion, water splitting, and oxygen reduction reaction in fuel cells through photocatalytic, electrocatalytic, and thermocatalytic processes, are discussed. This will provide an understanding of the rapid development and practical applications of SACs for “carbon neutrality.”
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