9 research outputs found
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Self-optimizing, highly surface-active layered metal dichalcogenide catalysts for hydrogen evolution
Low-cost, layered transition-metal dichalcogenides (MX_2) based on molybdenum and tungsten have attracted substantial interest as alternative catalysts for the hydrogen evolution reaction (HER). These materials have high intrinsic per-site HER activity; however, a significant challenge is the limited density of active sites, which are concentrated at the layer edges. Here we unravel electronic factors underlying catalytic activity on MX_2 surfaces, and leverage the understanding to report group-5 MX_2 (H-TaS_2 and H-NbS_2) electrocatalysts whose performance instead mainly derives from highly active basal-plane sites, as suggested by our first-principles calculations and performance comparisons with edge-active counterparts. Beyond high catalytic activity, they are found to exhibit an unusual ability to optimize their morphology for enhanced charge transfer and accessibility of active sites as the HER proceeds, offering a practical advantage for scalable processing. The catalysts reach 10 mA cm^(−2) current density at an overpotential of ∼50–60 mV with a loading of 10–55 μg cm^(−2), surpassing other reported MX2 candidates without any performance-enhancing additives
Self-optimizing, highly surface-active layered metal dichalcogenide catalysts for hydrogen evolution
Low-cost, layered transition-metal dichalcogenides (MX_2) based on molybdenum and tungsten have attracted substantial interest as alternative catalysts for the hydrogen evolution reaction (HER). These materials have high intrinsic per-site HER activity; however, a significant challenge is the limited density of active sites, which are concentrated at the layer edges. Here we unravel electronic factors underlying catalytic activity on MX_2 surfaces, and leverage the understanding to report group-5 MX_2 (H-TaS_2 and H-NbS_2) electrocatalysts whose performance instead mainly derives from highly active basal-plane sites, as suggested by our first-principles calculations and performance comparisons with edge-active counterparts. Beyond high catalytic activity, they are found to exhibit an unusual ability to optimize their morphology for enhanced charge transfer and accessibility of active sites as the HER proceeds, offering a practical advantage for scalable processing. The catalysts reach 10 mA cm^(−2) current density at an overpotential of ∼50–60 mV with a loading of 10–55 μg cm^(−2), surpassing other reported MX2 candidates without any performance-enhancing additives
Synthesis, Electrocatalytic Properties, and Physical Phenomena of Group V Transition Metal Dichalcogenide Nanostructures
2D van der Waals solids (vdW) have received attention for decades, due to their unique anisotropic mechanical character, making them useful in applications such as lubricants and pencils. But their anisotropy is not limited only to mechanical properties; rather it extends by default to all physical properties, making vdW solids interesting candidates for applications in fields as varied as catalysis and electronics. Here, we explore nanostructures of group V transition metal dichalcogenides (TMDs), a family of vdW solids, NbS2 and TaS2. We develop new vapor-phase bottom-up synthetic routes for nanosheet and nanotube variants. Furthermore, we discover their anisotropy-resulting self-optimizing behavior as hydrogen evolution catalysts, opening a new area of research
Self-optimizing, highly surface-active layered metal dichalcogenide catalysts for hydrogen evolution
Hydrogen is a promising energy carrier and key agent for many industrial
chemical processes1. One method for generating hydrogen sustainably is via the
hydrogen evolution reaction (HER), in which electrochemical reduction of
protons is mediated by an appropriate catalyst-traditionally, an expensive
platinum-group metal. Scalable production requires catalyst alternatives that
can lower materials or processing costs while retaining the highest possible
activity. Strategies have included dilute alloying of Pt2 or employing less
expensive transition metal alloys, compounds or heterostructures (e.g., NiMo,
metal phosphides, pyrite sulfides, encapsulated metal nanoparticles)3-5.
Recently, low-cost, layered transition-metal dichalcogenides (MX2)6 based on
molybdenum and tungsten have attracted substantial interest as alternative HER
catalysts7-11. These materials have high intrinsic per-site HER activity;
however, a significant challenge is the limited density of active sites, which
are concentrated at the layer edges.8,10,11. Here we use theory to unravel
electronic factors underlying catalytic activity on MX2 surfaces, and leverage
the understanding to report group-5 MX2 (H-TaS2 and H-NbS2) electrocatalysts
whose performance instead derives from highly active basal-plane sites. Beyond
excellent catalytic activity, they are found to exhibit an unusual ability to
optimize their morphology for enhanced charge transfer and accessibility of
active sites as the HER proceeds. This leads to long cycle life and practical
advantages for scalable processing. The resulting performance is comparable to
Pt and exceeds all reported MX2 candidates
Ambient solid-state mechano-chemical reactions between functionalized carbon nanotubes
Carbon nanotubes can be chemically modified by attaching various functionalities to their surfaces, although harsh chemical treatments can lead to their break-up into graphene nanostructures. On the other hand, direct coupling between functionalities bound on individual nanotubes could lead to, as yet unexplored, spontaneous chemical reactions. Here we report an ambient mechano-chemical reaction between two varieties of nanotubes, carrying predominantly carboxyl and hydroxyl functionalities, respectively, facilitated by simple mechanical grinding of the reactants. The purely solid-state reaction between the chemically differentiated nanotube species produces condensation products and unzipping of nanotubes due to local energy release, as confirmed by spectroscopic measurements, thermal analysis and molecular dynamic simulations
Chemical Vapor Deposition Of Monolayer Rhenium Disulfide (res2).
The direct synthesis of monolayer and multilayer ReS2 by chemical vapor deposition at a low temperature of 450 °C is reported. Detailed characterization of this material is performed using various spectroscopy and microscopy methods. Furthermore initial field-effect transistor characteristics are evaluated, which highlight the potential in being used as an n-type semiconductor.274640-464