Two-dimensional materials and single-atom catalysts are two frontier research fields in catalysis. A new category of catalysts with the integration of both aspects has been rapidly developed in recent years, and significant advantages were established to make it an independent research field. In this Review, we will focus on the concept of two-dimensional materials confining single atoms for catalysis. The new electronic states via the integration lead to their mutual benefits in activity, that is, two-dimensional materials with unique geometric and electronic structures can modulate the catalytic performance of the confined single atoms, and in other cases the confined single atoms can in turn affect the intrinsic activity of two-dimensional materials. Three typical two-dimensional materials are mainly involved here, i.e., graphene, g-C3N4, and MoS2, and the confined single atoms include both metal and nonmetal atoms. First, we systematically introduce and discuss the classic synthesis methods, advanced ...

Catalysis with Two-Dimensional Materials Confining Single Atoms: Concept, Design, and Applications.

Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.

Single-Atom Catalysts across the Periodic Table.

Molybdenum disulfide (MoS2) is one of the most broadly utilized solid lubricants with a wide range of applications, including but not limited to those in the aerospace/space industry. Here we present a focused review of solid lubrication with MoS2 by highlighting its structure, synthesis, applications and the fundamental mechanisms underlying its lubricative properties, together with a discussion of their environmental and temperature dependence. The review also includes an extensive overview of the structure and tribological properties of doped MoS2, followed by a discussion of potential future research directions.

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Solid Lubrication with MoS2: A Review

1T MoS2 is metallic octahedral type molybdenum disulfide (MoS2). Compared to the most stable and widely existing triangle prismatic (2H) phase of MoS2, 1T MoS2 possesses distinct electrochemical and electronic properties, such as a high conductivity, abundant active sites both at the edges and on the basal plane for electrochemical catalysis, and enlarged interlayer distance. Due to these merits, the last few years have witnessed a growing amount of interest in both synthesis and application of this unique material. So far, a series of methods have been developed to obtain 1T rich or 1T containing MoS2 and the applications of 1T MoS2 have covered a wide range of areas from electrochemical reactions, photoelectrocatalysis and photodetectors to photothermal agents, energy storage devices, and biosensors. In this article, to obtain a hint of the key reasons for the formation of 1T structured MoS2 and instruct the exploration of more desirable new approaches, the means for fabricating 1T MoS2 that have been reported are carefully classified and compared with a focus on the detailed procedures and the underlying mechanisms. Meanwhile, a full image of the explored applications with 1T MoS2 is provided with an emphasis on the relationship between the properties of 1T MoS2 and the performance and a hope to inspire the development of other potential applications for 1T MoS2. Additionally, the stabilization issue of 1T MoS2 is discussed with a review of the current efforts. The content will be not only helpful for researchers currently working in the related areas but also instructive for the ones new to this field.

Synthesis, stabilization and applications of 2-dimensional 1T metallic MoS2

The lack of highly efficient, inexpensive catalysts severely hinders large-scale application of electrochemical hydrogen evolution reaction (HER) for producing hydrogen. MoS2 as a low-cost candidate suffers from low catalytic performance. Herein, taking advantage of its tri-layer structure, we report a MoS2 nanofoam catalyst co-confining selenium in surface and cobalt in inner layer, exhibiting an ultra-high large-current-density HER activity surpassing all previously reported heteroatom-doped MoS2. At a large current density of 1000 mA cm−2, a much lower overpotential of 382 mV than that of 671 mV over commercial Pt/C catalyst is achieved and stably maintained for 360 hours without decay. First-principles calculations demonstrate that inner layer-confined cobalt atoms stimulate neighbouring sulfur atoms while surface-confined selenium atoms stabilize the structure, which cooperatively enable the massive generation of both in-plane and edge active sites with optimized hydrogen adsorption activity. This strategy provides a viable route for developing MoS2-based catalysts for industrial HER applications. The lack of efficient, inexpensive catalysts hinders large-scale application of hydrogen evolution reaction (HER). Here, the authors report a MoS2 nanofoam catalyst with co-confined Se in the surface and Co in the inner layer, exhibiting high large-current-density HER activity and durability.

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Boosting hydrogen evolution on MoS2 via co-confining selenium in surface and cobalt in inner layer.

Two-dimensional (2D) MoS2 is used as a catalyst or support and has received increased research interest because of its superior structural and electronic properties compared with those of bulk structures. In this article, we illustrate the active sites of 2D MoS2 and various strategies for enhancing its intrinsic catalytic activity. The recent advances in the use of 2D MoS2-based materials for applications such as thermocatalysis, electrocatalysis, and photocatalysis are discussed. We also discuss the future opportunities and challenges for 2D MoS2-based materials, in both fundamental research and industrial applications.

The rise of two-dimensional MoS 2 for catalysis

The invention discloses a self-supporting water electrolysis material with a dual carbon sandwich structure and a preparation method thereof, and relates to the field of nano material preparation. Thewater electrolysis material comprises an inner carbon layer, a sandwich layer, and an outer carbon layer. The inner carbon layer is made of carbon fibers. The outer carbon layer is made of conductivecarbon. The sandwich layer is transition metal chalcogenide having a three dimensional porous structure. The preparation method comprises following steps: taking a carbon fiber material as a substrate, washing the substrate in a mixed solution of ultrapure water and ethanol, drying the substrate to obtain the inner carbon layer; building a template with a porous structure on the surface of the substrate of the inner carbon layer; in-situ growing TMDs on the template to form self-supporting growing three dimensional porous structure TMDs, transferring TMDs to a tubular furnace, raising the temperature to 200 to 800 DEG C in an inert atmosphere by program, introducing a carbon containing precursor, maintaining the temperature for 5 to 240 minutes, and forming a layer of conductive carbon onthe surface of TMDs. The provided water electrolysis material has a high specific surface area and high catalytic activity. The preparation method is easy to operate, and can be used to build other two dimensional material structures.

Self-supporting water electrolysis material with dual carbon sandwich structure and preparation method thereof

The invention discloses a preparation method of molybdenum disulfide with a three-dimensional hierarchical pore structure. Specifically, the method comprises the following steps: firstly, preparing templates with various scales, then fully and uniformly mixing a molybdenum-based compound with the templates, reacting with a sulfur-containing compound at a certain temperature, finally, carrying outsolution treatment, and carrying out suction filtration and drying to obtain a target product. The material prepared by the method has a complete three-dimensional hierarchical pore structure and is free of clustering and collapse phenomena, and the pore wall of the material is composed of a molybdenum disulfide nanosheet array. The type of the template and the pore channel size are easy to modulate. The material has excellent activity when being used for electrocatalytic hydrogen evolution reaction. The method is a universal method for molybdenum disulfide with a three-dimensional hierarchical pore structure, and has the characteristics of simplicity and easiness in operation.

Molybdenum disulfide with three-dimensional hierarchical pore structure and preparation method and application thereof

The invention discloses a preparation method of polyatomic co-doped molybdenum disulfide. Specifically, the method comprises the following steps: firstly, uniformly dispersing a plurality of doped atom precursors with a molybdenum source in sequence, then reacting with a sulfur-containing compound at a certain temperature, finally, carrying out solution treatment, and carrying out suction filtration and drying to obtain a target product. The material prepared by the method has a clear structure, a single crystal image and no cluster or non-molybdenum disulfide crystal image formation. The types and the contents of the doped heteroatoms are easy to modulate. The material has excellent activity when being used for electrocatalytic hydrogen evolution reaction. The method is a universal methodfor preparing polyatomic co-doped molybdenum disulfide, and has the characteristics of being simple and easy to operate.

Zheng Zhilong

Papers

Boosting hydrogen evolution on MoS2 via co-confining selenium in surface and cobalt in inner layer.

The rise of two-dimensional MoS 2 for catalysis

Self-supporting water electrolysis material with dual carbon sandwich structure and preparation method thereof

Molybdenum disulfide with three-dimensional hierarchical pore structure and preparation method and application thereof

Polyatomic co-doped molybdenum disulfide and preparation method and application thereof