This report focuses
on a novel strategy for the preparation of
transition metal–MoS2 hybrid nanoclusters based
on a one-step, dual-target magnetron sputtering, and gas condensation
process demonstrated for Ni-MoS2. Aberration-corrected
STEM images coupled with EDX analysis confirms the presence of Ni
and MoS2 in the hybrid nanoclusters (average diameter =
5.0 nm, Mo:S ratio = 1:1.8 ± 0.1). The Ni-MoS2 nanoclusters
display a 100 mV shift in the hydrogen evolution reaction (HER) onset
potential and an almost 3-fold increase in exchange current density
compared with the undoped MoS2 nanoclusters, the latter
effect in agreement with reported DFT calculations. This activity
is only reached after air exposure of the Ni-MoS2 hybrid
nanoclusters, suggested by XPS measurements to originate from a Ni
dopant atoms oxidation state conversion from metallic to 2+ characteristic
of the NiO species active to the HER. Anodic stripping voltammetry
(ASV) experiments on the Ni-MoS2 hybrid nanoclusters confirm
the presence of Ni-doped edge sites and reveal distinctive electrochemical
features associated with both doped Mo-edge and doped S-edge sites
which correlate with both their thermodynamic stability and relative
abundance.
Materials show various responses to incident light, owing to their unique dielectric functions. A well‐known example is the distinct colors displayed by metals, providing probably the simplest method to identify gold, silver, and bronze since ancient times. With the advancement of nanotechnology, optical structures with feature sizes smaller than the optical wavelength have been routinely achieved. In this regime, the optical response is also determined by the geometry of the nanostructures, inspiring flourishing progress in plasmonics, photonic crystals, and metamaterials. Nevertheless, the nature of the materials still plays a decisive role in light–matter interactions, and this material‐dependent optical response is widely accepted as a norm in nanophotonics. Here, a counterintuitive system—plasmonic nanostructures composed of different materials but exhibiting almost identical reflection—is proposed and realized. The geometric disorder embedded in the system overwhelms the contribution of the material properties to the electrodynamics. Both numerical simulations and experimental results provide concrete evidence of the insensitivity of the optical response to different plasmonic materials. The same optical response is preserved with various materials, providing great flexibility of freedom in material selection. As a result, the proposed configuration may shed light on novel applications ranging from Raman spectroscopy, photocatalysis, to nonlinear optics.
1D carbon structures are attractive due to their mechanical, chemical and electrochemical properties. Further enhancements to these structures can be made by creating structural hierarchy, producing composites with catalytically active metal nanoparticle domains -however the synthesis of these materials can be costly and complicated. Here, through the combination of inexpensive acetylacetonate salts of Ni, Co and Fe with a solution of polyacrylonitrile (PAN) which was electrospun and subsequently heat treated, self-assembling carbon-metal fabrics (CMFs) containing unique 1D hierarchical structures can be created readily. Microscopic and spectroscopic measurements show that the CMFs form through the decomposition and exsolution of metal nanoparticle domains which then catalyse the formation of carbon nanotubes through the decomposition by-products of the PAN. These weakly bound nanoparticles form structures similar to trichomes found in plants, with a combination of base-growth, tip-growth and peapod-like structures, where the metal domain exhibits a core(graphitic)-shell(disorder) 2 carbon coating where the thickness is in-line with the metal-carbon binding energy. The applicability of these carbon-metal fabrics (CMFs) was demonstrated as a cathode in an allsolid-state zinc-air battery which exhibited superior performance to pure electrospun carbon fibres, in addition to enhanced mechanical flexibility due to the enhanced surface area of the hairy fibres and their metallic nanoparticle domains which acted as bifunctional catalysts to oxygen reduction and evolution. This work therefore unlocks a potentially new category of composite metal-carbon fibre based structures for energy storage applications and beyond, which can be created in a low cost manner.
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