Capping agents are frequently used in colloidal synthesis to inhibit nanoparticle overgrowth and aggregation as well as to control the structural characteristics of the resulted nanoparticles in a ...precise manner. Study of the effect of the residual capping agents on particle surface has unveiled various adverse and favorable behaviors in catalytic applications. In essence, while the capping agents usually act as a physical barrier to restrict the free access of reactants to catalytic nanoparticles, they can also be utilized to promote catalytic performance of nanocrystals. Due to the complexity of these effects, a general survey of capping agents in nanocatalysis is therefore necessary. This short review starts from a brief introduction of common capping agents in nanoparticle synthesis and their adverse impact on heterogeneous catalysis. Next, representative progresses in capping agent removal and surfactant-free synthesis for obtaining surface-clean nanocatalysts are summarized. Lastly, we discuss the recent advance in utilizing the capping agent effect including chiral modification, molecular recognition, adsorption regulation, surface crowding, and charge transfer at the metal–organic interface and so on to improve the catalytic performance of nanocatalysts.
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.
Manipulating metal atoms in a controllable way for the synthesis of materials with the desired structure and properties is the holy grail of chemical synthesis. The recent emergence of single atomic ...site catalysts (SASC) demonstrates that we are moving toward this goal. Owing to the maximum efficiency of atom-utilization and unique structures and properties, SASC have attracted extensive research attention and interest. The prerequisite for the scientific research and practical applications of SASC is to fabricate highly reactive and stable metal single atoms on appropriate supports. In this review, various synthetic strategies for the synthesis of SASC are summarized with concrete examples highlighting the key issues of the synthesis methods to stabilize single metal atoms on supports and to suppress their migration and agglomeration. Next, we discuss how synthesis conditions affect the structure and catalytic properties of SASC before ending this review by highlighting the prospects and challenges for the synthesis as well as further scientific researches and practical applications of SASC.
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.
Photocatalytic reduction of CO2 to value-added fuels is a promising route to reduce global warming and enhance energy supply. However, poor selectivity and low efficiency of catalysts are usually the ...limiting factor of their applicability. Herein, a photoinduction method was developed to achieve the formation of Cu single atoms on a UiO-66-NH2 support (Cu SAs/UiO-66-NH2) that could significantly boost the photoreduction of CO2 to liquid fuels. Notably, the developed Cu SAs/UiO-66-NH2 achieved the solar-driven conversion of CO2 to methanol and ethanol with an evolution rate of 5.33 and 4.22 μmol h–1 g–1, respectively. These yields were much higher than those of pristine UiO-66-NH2 and Cu nanoparticles/UiO-66-NH2 composites. Theoretical calculations revealed that the introduction of the Cu SAs on the UiO-66-NH2 greatly facilitates the conversion of CO2 to CHO* and CO* intermediates, leading to excellent selectivity toward methanol and ethanol. This study provides new insights for designing high-performance catalyst for photocatalytic reduction of CO2 at the atomic scale.
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.
An effective noble-metal-induced reduction (NMIR) strategy for the synthesis of Au-based hybrid magnetic nanostructures, including Au−Co core−shell nanocrystals and Au−Ni spindly nanostructures, has ...been developed. This NMIR process provides new insights into the reduction of metal ions in organic solvents and also applies to the synthesis of various bimetallic nanocrystals.
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