Se-Incorporation Stabilizes and Activates Metastable MoS2 for Efficient and Cost-Effective Water Gas Shift Reaction

Dual carbon engineering enabling 1T/2H MoS2 with ultrastable potassium ion storage performance

Potassium-ion batteries (PIBs) as a promising and low-cost battery technology offer the advantage of utilizing abundant and cost-effective K-salt sources. However, the effective adoption of PIBs necessitates the identification of suitable electrode materials. The 1T phase of MoS2 exhibits enhanced electronic conductivity and greater interlayer spacing compared to the 2H phase, leading to a capable potassium ion storage ability. Herein, we fabricated dual carbon engineered 1T/2H MoS2via a secure and straightforward ammonia-assisted hydrothermal method. The 1T/2H MoS2@rGO@C structure demonstrated an expanded interlayer spacing (9.3 Å). Additionally, the sandwich-like structural design not only enhanced material conductivity but also effectively curbed the agglomeration of nanosheets. Remarkably, 1T/2H MoS2@rGO@C exhibited impressive potassium storage ability, delivering capacities of 351.0 mA h g-1 at 100 mA g-1 and 233.8 mA h g-1 at 1000 mA g-1 following 100 and 1000 cycles, respectively. Moreover, the construction of a K-ion full cell was successfully achieved, utilizing perylene tetracarboxylic dianhydride (PTCDA) as the cathode, and manifesting a capacity of 294.3 mA h g-1 at 100 mA g-1 after 160 cycles. This underscores the substantial potential of employing the 1T/2H MoS2@rGO@C electrode material for PIBs.

Strain and Surface Engineering of Multicomponent Metallic Nanomaterials with Unconventional Phases

Multicomponent metallic nanomaterials with unconventional phases show great prospects in electrochemical energy storage and conversion, owing to unique crystal structures and abundant structural effects. In this review, we emphasize the progress in the strain and surface engineering of these novel nanomaterials. We start with a brief introduction of the structural configurations of these materials, based on the interaction types between the components. Next, the fundamentals of strain, strain effect in relevant metallic nanomaterials with unconventional phases, and their formation mechanisms are discussed. Then the progress in surface engineering of these multicomponent metallic nanomaterials is demonstrated from the aspects of morphology control, crystallinity control, surface modification, and surface reconstruction. Moreover, the applications of the strain- and surface-engineered unconventional nanomaterials mainly in electrocatalysis are also introduced, where in addition to the catalytic performance, the structure-performance correlations are highlighted. Finally, the challenges and opportunities in this promising field are prospected.

Synthesis of Methyl Mercaptan on Mesoporous Alumina Prepared with Hydroxysafflor Yellow A as Template: The Synergistic Effect of Potassium and Molybdenum

K-promoted Mo-based catalysts showed great promise for the hydrogenation of CS2 to methyl mercaptan (CH3SH). However, the research on the synergistic effect of K and Mo, and the active site of CS2 hydrogenation to CH3SH were unexplored widely. To solve this problem, the synergistic effect of K and Mo in the K-promoted Mo-based catalysts for CS2 hydrogenation to prepare CH3SH was investigated. The mesoporous alumina was the support and loaded the active components potassium and molybdenum to prepare the catalyst. The results suggested that the active components K and Mo can not only cooperatively regulate the acid-base sites on the catalyst surface, but also stabilize the molybdate species at +5 valence during the reduction process and increase the Mo unsaturated coordination sites. Combined with the results of the catalytic activity evaluation, indicating that the main active site of the catalysts is the weak Lewis acid-base site, and the strong acidic site and strong alkaline site are not conducive to the formation of CH3SH. Moreover, the possible catalytic mechanism of CS2 hydrogenation to CH3SH on the weak Lewis acid-base sites of the catalysts was proposed. The research results of this paper can provide an experimental basis and theoretical guidance for the design of high-performance CH3SH synthesis catalyst and further mechanism research.

Iridium metallene oxide for acidic oxygen evolution catalysis

Exploring new materials is essential in the field of material science. Especially, searching for optimal materials with utmost atomic utilization, ideal activities and desirable stability for catalytic applications requires smart design of materials' structures. Herein, we report iridium metallene oxide: 1 T phase-iridium dioxide (IrO2) by a synthetic strategy combining mechanochemistry and thermal treatment in a strong alkaline medium. This material demonstrates high activity for oxygen evolution reaction with a low overpotential of 197 millivolt in acidic electrolyte at 10 milliamperes per geometric square centimeter (mA cmgeo-2). Together, it achieves high turnover frequencies of 4.2 sUPD-1 (3.0 sBET-1) at 1.50 V vs. reversible hydrogen electrode. Furthermore, 1T-IrO2 also shows little degradation after 126 hours chronopotentiometry measurement under the high current density of 250 mA cmgeo-2 in proton exchange membrane device. Theoretical calculations reveal that the active site of Ir in 1T-IrO2 provides an optimal free energy uphill in *OH formation, leading to the enhanced performance. The discovery of this 1T-metallene oxide material will provide new opportunities for catalysis and other applications.

Single-Atom Catalysts across the Periodic Table

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.

Closest Packing Polymorphism Interfaced Metastable Transition Metal for Efficient Hydrogen Evolution

Metastable materials are promising because of their catalytic properties, high-energy structure, and unique electronic environment. However, the unstable nature inherited from the metastability hinders further performance improvement and practical applications of these materials. Herein, this limitation is successfully addressed by constructing an in situ polymorphism interface (inf) between the metastable hexagonal-close-packed (hcp) phase and its stable counterpart (face-centered cubic, fcc) in cobalt-nickel (CoNi) alloy. Calculations reveal that the interfacial synergism derived from the hcp and fcc phases lowers the formation energy and enhances stability. Consequently, the optimized CoNi-inf exhibits an exceptionally low potential of 72 mV at 10 mA cm^-2 and a Tafel slope of 57 mV dec^-1 for the hydrogen evolution reaction (HER) in 1.0 m KOH. Furthermore, it is superior to most state-of-the-art non-noble-metal-based HER catalysts. No noticeable activity decay or structural changes are observed even over 14 h of catalysis. The computational simulation further rationalizes that the interface of CoNi-inf with a suitable d-band center provides uniform sites for hydrogen adsorption, leading to a distinguished HER catalytic activity. This work, therefore, presents a new route for designing metastable catalysts for potential energy conversion.