Metallic transition-metal dichalcogenide (TMDC) nanomaterials have emerged as highly active and robust catalysts for energy conversion from renewable electricity or solar energy to fuels via electrochemical or solar-driven water-splitting technologies. Possessing intriguing electronic and catalytic properties, this category of materials based on earth-abundant elements is increasingly being explored and developed for practical applications. This review provides indepth insights into recent progress regarding electrocatalysis and photocatalysis using metallic TMDC nanomaterials. After the introduction and fundamental illustration of the structures and extraordinary properties, we discuss the significant developments in synthetic methodologies and energy conversion applications with significant strategies for enhancing catalytic performance. Several personal perspectives on the opportunities and challenges in this promising realm are discussed in the conclusion.

The development of layered molybdenum chalcogenides with largely exposed active sites is receiving intense interest because of their potential applications in energy storage and catalysis.

We have demonstrated the improved performance of oxygen evolution reactions (OER) using Au/nickel phosphide (Ni 12 P 5 ) core/shell nanoparticles (NPs) under basic conditions. NPs with a Ni 12 P 5 shell and a Au core, both of which have well-defined crystal structures, have been prepared using solution-based synthetic routes. Compared with pure Ni 12 P 5 NPs and Au-Ni 12 P 5 oligomer-like NPs, the core/shell crystalline structure with Au shows an improved OER activity. It affords a current density of 10 mA/cm 2 at a small overpotential of 0.34 V, in 1 M KOH aqueous solution at room temperature. This enhanced OER activity may relate to the strong structural and effective electronic coupling between the single-crystal core and the shell.

Electrochemical water splitting has been intensively pursued as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of low-cost and high-performance electrocatalysts for the hydrogen evolution reaction (HER) hinders the large-scale application. Herein, we have rationally designed and synthesized 3D self-assembly architectures assembled from ultrafine MoC nanoparticles (0D) uniformly embedded within N-doped carbon nanosheets (2D) for the HER via a simple protocol. The well-organized 3D nanostructures are composed of very small MoC nanocrystallites (<2 nm) and free-stretching conductive carbon nanosheets with high specific surface areas and abundant mesopores, which can expose more active sites and facilitate electron/ion transport pathways. Based on the merits of the composition and configuration, the resultant hierarchical 3D self-assembly architectures exhibit remarkable electrocatalytic performance and stability for the HER.

Two-dimensional (2D) nanomaterials such as transition metal dichalcogenides (TMDs) and graphene have attracted extensive interest as emergent materials, owing to their excellent properties that favor their future use in electronic devices, catalysis, optics, and biological-or energy-relevant areas. However, 2D nanosheets tend to easily restack and condense, which weakens their performance in many of these applications. Assembling these 2D nanosheets as building blocks for three-dimensional (3D) architectures not only maintains the intrinsic performances of the 2D nanostructures but also synergistically makes use of the advantages of the 3D microstructures to improve the overall material properties. In this critical review, we will highlight recent developments of sundry 2D nanosheet-assembled 3D architectures, including their design, synthesis, and potential applications. Their controllable syntheses, novel structures, and potential applications will be systematically explained, analyzed, and summarized. In the end, we will offer some perspective on the challenges facing future advancement of this field.

Two-dimensional (2D) nanoheterostructure (2D NHS) with nanoparticles grown on 2D nanomaterial substrates could potentially enable many novel functionalities. Controlled site-selective growth of nanoparticles on either the lateral or the basal directions of 2D nanomaterial substrates is desirable but extremely challenging. Herein, we demonstrate the rational control of lateral- and basal-selective attachment of CdS nanoparticles onto 2D Bi2Se3 nanosheets through solution phase reactions. The combination of experimental and theoretical efforts elucidate that site-relevant interfacial bonding and kinetic control of molecular precursors play vital roles for site selectivity. Furthermore, the electronic structures revealed from density functional theory calculations explain the superior performance of the lateral 2D NHSs compared to their basal counterpart in prototype photoelectrochemical cells. The present study will inspire the construction of other site-selective 2D NHSs with well-defined structure and unique properties.

Oxidative methane (CH 4 ) carbonylation promises a direct route to the synthesis of value-added oxygenates such as acetic acid (CH 3 COOH). Here, we report a strategy to realize oxidative CH 4 carbonylation through immobilized Ir complexes on an oxide support. Our immobilization approach not only enables direct CH 4 activation but also allows for easy separation and reutilization of the catalyst. Furthermore, we show that a key step, methyl migration, that forms a C−C bond, is sensitive to the electrophilicity of carbonyl, which can be tuned by a gentle reduction to the Ir centers. While the as-prepared catalyst that mainly featured Ir(IV) preferred CH 3 COOH production, a reduced catalyst featuring predominantly Ir(III) led to a significant increase of CH 3 OH production at the expense of the reduced yield of CH 3 COOH.

Atomically dispersed catalysts such as single-atom catalysts have been shown to be effective in selectively oxidizing methane, promising a direct synthetic route to value-added oxygenates such as acetic acid or methanol. However, an important challenge of this approach has been that the loading of active sites by single-atom catalysts is low, leading to a low overall yield of the products. Here, we report an approach that can address this issue. It utilizes a metal–organic framework built with porphyrin as the linker, which provides high concentrations of binding sites to support atomically dispersed rhodium. It is shown that up to 5 wt% rhodium loading can be achieved with excellent dispersity. When used for acetic acid synthesis by methane oxidation, a new benchmark performance of 23.62 mmol·gcat –1·h–1 was measured. Furthermore, the catalyst exhibits a unique sensitivity to light, producing acetic acid (under illumination, up to 66.4% selectivity) or methanol (in the dark, up to 65.0% selectivity) under otherwise identical reaction conditions.