Abstract:Matrix-supported metal nanoclusters (1−10 nm) with unique size-and shape-dependent properties have drawn attention for their potential applications in electronics, catalysis, energy storage, and sensors. However, synthesis of matrixsupported ultrasmall nanoclusters at high concentration and in an unaggregated state is challenging. Here we demonstrate a rapid laser pulse technique to in situ fabricate ultrasmall metal nanoclusters supported on a carbon nanofiber (CNF) matrix with kinetically controllable size a… Show more
“…[ 20 ] With a longer duration of laser impact in either CW or pulsed irradiation modes, the size of nanoparticles will grow larger (Figure S4 and S5, Supporting Information) due to the occurrence of Ostwald ripening. [ 21 ] However, after 1000 ms irradiation in pulsed mode, the average size of nanoparticles is still below 20 nm, much smaller than HEA particles (31.54 ± 19.19 nm) produced by irradiation in continuous mode. The different composition was also found to influence the particle size during laser impact as proved by Figures S6 and S7, Supporting Information, where quaternary metallic alloy particles are dimensionally smaller than binary particles.…”
Fabrication of advanced electrocatalysts acting as an electrode for simultaneous hydrogen and oxygen evolution reactions (i.e., HER and OER) in an overall cell has attracted massive attention but still faces enormous challenges. This study reports a significant strategy for the rapid synthesis of high-entropy alloys (HEAs) by pulsed laser irradiation. Two types of intrinsic atomic hollow sites over the surface of HEAs are revealed that enable engaging bifunctional activities for water splitting. In this work, a novel senary HEA electrocatalyst made of FeCoNiCuPtIr facilitates the redox of water at only 1.51 V to achieve 10 mA cm −2 and still remains steadily catalytic and durable after being subjected to a 1m KOH solution for more than 20 h. First-principles calculations reveal that the incorporation of Ir and Pt atoms with neighboring elements donate valence electrons to hollow sites weakening the coupling strength between adsorbate and alloy surface and, consequently accelerating both HER and OER. This work delivers a powerful technique to synthesize highly efficient HEA catalysts and unravels the formation mechanism of active sites across the surface of HEA catalysts.
“…[ 20 ] With a longer duration of laser impact in either CW or pulsed irradiation modes, the size of nanoparticles will grow larger (Figure S4 and S5, Supporting Information) due to the occurrence of Ostwald ripening. [ 21 ] However, after 1000 ms irradiation in pulsed mode, the average size of nanoparticles is still below 20 nm, much smaller than HEA particles (31.54 ± 19.19 nm) produced by irradiation in continuous mode. The different composition was also found to influence the particle size during laser impact as proved by Figures S6 and S7, Supporting Information, where quaternary metallic alloy particles are dimensionally smaller than binary particles.…”
Fabrication of advanced electrocatalysts acting as an electrode for simultaneous hydrogen and oxygen evolution reactions (i.e., HER and OER) in an overall cell has attracted massive attention but still faces enormous challenges. This study reports a significant strategy for the rapid synthesis of high-entropy alloys (HEAs) by pulsed laser irradiation. Two types of intrinsic atomic hollow sites over the surface of HEAs are revealed that enable engaging bifunctional activities for water splitting. In this work, a novel senary HEA electrocatalyst made of FeCoNiCuPtIr facilitates the redox of water at only 1.51 V to achieve 10 mA cm −2 and still remains steadily catalytic and durable after being subjected to a 1m KOH solution for more than 20 h. First-principles calculations reveal that the incorporation of Ir and Pt atoms with neighboring elements donate valence electrons to hollow sites weakening the coupling strength between adsorbate and alloy surface and, consequently accelerating both HER and OER. This work delivers a powerful technique to synthesize highly efficient HEA catalysts and unravels the formation mechanism of active sites across the surface of HEA catalysts.
“…The particle size before EJH is 10.0 ± 3.3 nm based on measurements of at least 100 individual Rh–Ir particles by the SEM image analysis software, whereas the size after EJH induced alloying is larger (31.9 ± 7.7 nm), likely due to the atomic migration, and grain growth 32 . Classic sintering behaviour can be observed, where particles consolidate to form bigger particles (Ostwald ripening) and some voids 33 . Figure 2 Top-view SEM image of Rh–Ir thin film: ( a ) before EJH; ( b ) after EJH.…”
Metal alloys are usually fabricated by melting constituent metals together or sintering metal alloy particles made by high energy ball milling (mechanical alloying). All these methods only allow for bulk alloys to be formed. This manuscript details a new method of fabricating Rhodium–Iridium (Rh–Ir) metal alloy films using atomic layer deposition (ALD) and rapid Joule heating induced alloying that gives functional thin film alloys, enabling conformal thin films with high aspect ratios on 3D nanostructured substrate. In this work, ALD was used to deposit Rh thin film on an Al2O3 substrate, followed by an Ir overlayer on top of the Rh film. The multilayered structure was then alloyed/sintered using rapid Joule heating. We can precisely control the thickness of the resultant alloy films down to the atomic scale. The Rh–Ir alloy thin films were characterized using scanning and transmission electron microscopy (SEM/TEM) and energy dispersive spectroscopy (EDS) to study their microstructural characteristics which showed the morphology difference before and after rapid Joule heating and confirmed the interdiffusion between Rh and Ir during rapid Joule heating. The diffraction peak shift was observed by Grazing-incidence X-ray diffraction (GIXRD) indicating the formation of Rh–Ir thin film alloys after rapid Joule heating. X-ray photoelectron spectroscopy (XPS) was also carried out and implied the formation of Rh–Ir alloy. Molecular dynamics simulation experiments of Rh–Ir alloys using Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) were performed to elucidate the alloying mechanism during the rapid heating process, corroborating the experimental results.
“…The particle size before EJH is ~8 nm, whereas the size after EJH induced alloying is larger (~29 nm), likely due to the atomic migration, and grain growth 27 . Classic sintering behaviour can be observed, where particles consolidate to form bigger particles (Ostwald ripening) and some voids 28 .…”
Metal alloys are usually fabricated by melting constituent metals together or sintering metal alloy particles made by high energy ball milling (mechanical alloying). All these methods only allow for bulk alloys to be formed. This manuscript details a new method of fabricating Rhodium/Iridium (Rh/Ir) metal alloy films using atomic layer deposition (ALD) and rapid Joule heating induced alloying that gives functional thin film alloys, enabling conformal thin films with high aspect ratios on 3D nanostructured substrate. In this work, ALD was used to deposit Rh thin film on an Al2O3 substrate, followed by an Ir overlayer on top of the Rh film. The multilayered structure was then alloyed / sintered using rapid Joule heating. We can precisely control the thickness of the resultant alloy films down to the atomic scale. The Rh@Ir alloy thin films were characterized using scanning and transmission electron microscopy (SEM/TEM) and energy dispersive spectroscopy (EDS) to study their microstructural characteristics. Grazing-incidence X-ray diffraction (GIXRD) and X-ray photoelectron spectroscopy (XPS) were also carried out to confirm the composition and formation of Rh-Ir thin film alloys. All the characterization results reveal that the Rh-Ir alloy thin film was prepared successfully with one single phase and homogeneous distribution of Rh and Ir throughout the film. Molecular Dynamics simulation experiments of Rh/Ir alloys using Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) were performed to elucidate the alloying mechanism during the rapid heating process, corroborating the experimental results.
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