CoNiCuCrS alloy nanoparticles: synthesis and atomically resolved T/STEM studies
Multimetallic alloy nanoparticles as a model for bulk high entropy alloy studies.
Rufino da Silva, Carlos E.↗
SEARCH · Engineering Papers
Results for “multimetallic”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Optimization of Rocket Engine Components using Multi-Metallic Additive Manufacturing
Additive manufacturing (AM) is advancing many applications of component design for liquid rocket engines. AM has been demonstrated in various rocket component applications using a variety of monolithic metal alloys, many of which are traditional alloys for extreme environments. NASA and industry partners have focused in recent years to advance processing to create bimetallic and multicomponent AM processes and materials. The role of multi-metallic AM offers advantages since it can further optimize weight, optimize reliability and performance by increasing the strength to weight ratio of a component, and can optimize materials for various engineering requirements. NASA’s Rapid Analysis and Manufacturing Propulsion Technology (RAMPT) project has designed and manufactured a series of additively manufactured (AM) coupled combustion chambers, nozzles, and other engine components to advance new AM processes and materials with the goal of reducing cost and schedule for engine manufacturing. These designs incorporated multimetallic AM, which further enabled carbon-fiber composite overwrap to reduce overall thrust chamber assembly (TCA) mass. Various AM processes were demonstrated on these components using a copper-based alloy/superalloy bimetallic solution. The AM processes being explored individually and in combination for bimetallic applications include Laser Powder Bed Fusion (L-PBF), Laser Powder Directed Energy Deposition (LP-DED), and cold spray. The combination of bimetallic material combinations explored in this research include GRCop-based alloys and superalloys, Inconel 625 or NASA HR-1. One unique development that will be presented is the combustion chamber and nozzle as a single component by using freeform integrated DED to build the nozzle directly onto the aft end of the chamber. The various aspects of the additive manufacturing processes and challenges, materials characterization and mechanical testing, and hot-fire testing of bimetallic components in a relevant rocket engine environment will be discussed.
Additive Manufacturing↗
High-Entropy Metal Sulfide Nanoparticles Promise High-Performance Oxygen Evolution Reaction
Transition metal sulfide with a multi-elemental nature represents a class of promising catalysts for oxygen evolution reaction (OER) owing to its good catalytic activity. However, its synthesis remains a grand challenge due to the thermodynamic immiscibility of the constituent multimetallic elements in a sulfide structure. Herein, we for the first time report a high-entropy metal sulfide (HEMS, i.e., (CrMnFeCoNi)Sx) solid solution nanoparticles. Computational and X-ray photoelectron spectroscopy analysis suggest that the (CrMnFeCoNi)S x exhibits a synergistic effect among metal atoms that leads to desired electronic states to enhance OER activity. The (CrMnFeCoNi)Sx nanoparticles showed one of the best activities (low overpotential 295 mV at 100 mA cm -2 in 1 M KOH solution) and good durability (only slight polarization after 10 hours by chronopotentiometry) compared with the unary, binary, ternary, and quaternary sulfide counterparts. This work opens up a new synthesis paradigm for high-entropy compound nanoparticles for highly efficient electrocatalysis applications.
25 ENERGY STORAGE↗
Strain‐Enhanced Metallic Intermixing in Shape‐Controlled Multilayered Core–Shell Nanostructures: Toward Shaped Intermetallics
Abstract Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd‐Ni‐Pt core–shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low‐temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape‐controlled multimetallic nanoparticles tailored to each potential application.
Williams, Benjamin P.↗
Hydrogenation Reactions with Heterobimetallic Complexes
Abstract Hydrogenations are fundamentally and industrially important reactions that are atom economical paths to synthesize value‐added products from feedstock chemicals. The cooperative effects of two or more metal centers in multimetallic active sites is a successful strategy to activate small molecules and facilitate catalytic reactions, and this strategy has been recently applied to catalytic hydrogenation reactions. Furthermore, heterobimetallic complexes have been well‐documented to provide novel reaction pathways and improved selectivity, compared to their homo‐bimetallic and monometallic analogues. This minireview provides a historical perspective on the development of heterobimetallic catalysts for the hydrogenation of unsaturated substrates and describes recent developments in this burgeoning research area.
Abhyankar, Preshit C.↗
Strain-Enhanced Metallic Intermixing in Shape-Controlled Multilayered Core–Shell Nanostructures: Toward Shaped Intermetallics
Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd-Ni-Pt core–shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low-temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape-controlled multimetallic nanoparticles tailored to each potential application.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Hydrogenation Reactions with Heterobimetallic Complexes
Hydrogenations are fundamentally and industrially important reactions that are atom economical paths to synthesize value‐added products from feedstock chemicals. The cooperative effects of two or more metal centers in multimetallic active sites is a successful strategy to activate small molecules and facilitate catalytic reactions, and this strategy has been recently applied to catalytic hydrogenation reactions. Furthermore, heterobimetallic complexes have been well‐documented to provide novel reaction pathways and improved selectivity, compared to their homo‐bimetallic and monometallic analogues. This minireview provides a historical perspective on the development of heterobimetallic catalysts for the hydrogenation of unsaturated substrates and describes recent developments in this burgeoning research area.
catalysis↗
Electronegativity-Guided Site Differentiation in High-Entropy Alloy for pH-universal Hydrogen Evolution Reactions
Enhancing the intrinsic activity of transition metal catalysts for the hydrogen evolution reaction (HER) remains a critical challenge in sustainable energy conversion. Herein, we report an electronegativity-guided site differentiation strategy in a single-phase CoNiCuMoW high-entropy alloy (HEA) via electrodeposition by incorporating high-electronegativity 4d/5d orbital transition metals (Mo, W) into the face-centered cubic (fcc) matrix (CoNiCu). The as-synthesized HEA demonstrates exceptional HER performance in all pH conditions, delivering an outstanding overpotential of 65 mV (alkaline), 28 mV (acidic), and 155 mV (neutral) at a current density of 100 mA cm−2, showing performance comparable to commercial Pt/C and has excellent long-term stability at high current density (1 A cm−2, 1000 h). X-Ray absorption spectroscopy (XAS) and density functional theory (DFT) calculations reveal that the incorporation of Mo/W simultaneously alters the local coordination environment and induces element-dependent charge redistribution, accompanied by a system-level d-band center downshift, thereby optimizing the hydrogen binding strength across multimetallic sites. Meanwhile, oxophilic Mo/W sites lower the water dissociation energy barrier. These synergistic effects collectively enable efficient and durable pH-universal HER performance.
Wu, Yutong↗
Leveraging Exchange Kinetics for the Synthesis of Atomically Precise Porous Catalysts
Metal-organic frameworks (MOFs) have attracted significant attention as porous catalyst platforms due to the synthetic modularity of these materials and the diversity of lattice-confined catalytic active sites that are readily embedded within periodic crystalline frameworks. MOFs offer platforms to heterogenize molecular catalysts, stabilize novel coordination motifs, and leverage confinement effects in catalysis. Crystallinity allows diffraction-based methods to be employed in the characterization of these catalysts. Access to crystalline MOFs typically requires reversible construction of the metal-ligand (M-L) bonds that connect the SBUs, which provides a mechanism to anneal defects during crystallization. While the required M-L bond reversibility is often promoted by synthesis at elevated temperature, access to crystalline materials based on either transition metals with characteristic slow exchange kinetics or highly basic donor ligands remains a synthetic challenge. Here in this paper, we highlight synthetic strategies that leverage M-L exchange kinetics to access MOFs based on kinetically inert ions and extensions of these strategies to the assembly of atomically precise multimetallic materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Six–Electron Chemistry of a Binuclear Fe(III) Fused Porphyrin
Here in this special collection dedicated to Prof. Jean-Michel Savéant, we report on the synthesis and characterization of a novel binuclear Fe(III) fused porphyrin. Ultraviolet-visible spectroscopy confirms the extended electronic structure of this macrocycle. In addition, Fourier transform infrared spectroscopy indicates the Fe centers experience a relatively rigid ligand environment as compared to a structurally related mononuclear complex featuring an 18 π-aromatic porphyrin ligand. X-ray photoelectron and X-ray absorption near edge spectroscopies confirm the iron centers of both assemblies are Fe(III) in the as prepared, resting state. In comparison with the mononuclear porphyrin, electrochemical measurements show there is a doubling of the number of redox events associated with the fused, binuclear complex. In conclusion, key features of the fused-iron-porphyrin include: 1) bimetallic-iron sites, 2) a π-extended ligand capable of delocalizing electrons across the multimetallic scaffold, and 3) the ability to store up to six electrons.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
De Nive Quinquangula: Pentagonal Snowflake Metal Nanocrystals as an Example of Emergence Phenomenon in Nanotechnology Complex Systems
The formation of snowflakes (SFL) is one of the most captivating phenomena in nature. The fabrication of multimetallic gold (Au) nanoparticles containing copper (Cu) and iron (Fe) is reported, which adopt snowflake-like morphology after nanoparticle aggregation. The synthesis of these snowflake-like Au microcrystals occurs mainly by kinetic control. In this process, a surfactant-assisted salt reduction method is employed on a heated substrate. Here, the metal salts react within seconds to form nanoparticles. This process results in a hierarchical structure with pseudo-pentagonal symmetry and chiroptical activity. We discuss how large superstructures emerge from nanoparticle aggregation, resembling natural snowflakes. However, unlike ice snowflakes, which exhibit hexagonal symmetry, the Au snowflakes display pentagonal symmetry. It is proposed that the formation of these snowflake-like microcrystals is the result of the complexity involved in the crystal growth process and represents an example of the phenomenon of emergence, which has become very significant in several fields of modern science, including physics, biology, chemistry, economics, philosophy, and poetry. The term emergent is used to evoke the collective behavior of a large number of microscopic constituents that is qualitatively different than the behaviors of the individual constituents.
36 MATERIALS SCIENCE↗
Morphology-controlled transformation of Cu@Au core-shell nanowires into thermally stable Cu 3 Au intermetallic nanowires
Multimetallic nanowires with long-range atomic ordering hold the promise of unique physicochemical properties in many applications. Here we demonstrate the synthesis and study the stability of Cu 3 Au intermetallic nanowires. The synthesis is achieved by using Cu@Au core-shell nanowires as precursors. With appropriate Cu/Au stoichiometry, the Cu@Au core-shell nanowires are transformed into fully ordered Cu 3 Au nanowires under thermal annealing. Thermally-driven atom diffusion accounts for this transformation as revealed by X-ray diffraction and electron microscopy studies. The twin boundaries abundant in the Cu@Au core-shell nanowires facilitate the ordering process. The resulting Cu 3 Au intermetallic nanowires have uniform and accurate atomic positioning in the crystal lattice, which enhances the nobility of Cu. No obvious copper oxides are observed in fully ordered Cu 3 Au nanowires after annealing in air at 200 °C, a temperature that is much higher than those observed in Cu@Au core-shell and pure Cu nanowires. This work opens up an opportunity for further research into the development and applications of intermetallic nanowires.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Synthesis of amorphous Pd-based nanocatalysts for efficient alcoholysis of styrene oxide and electrochemical hydrogen evolution
Amorphous nanomaterials with long-range disordered structures could possess distinct properties and promising applications, especially in catalysis, as compared with their conventional crystalline counterparts. It is imperative to achieve the controlled preparation of amorphous noble metal-based nanomaterials for the exploration of their phase-dependent applications. Here, in this work, we report a facile wet-chemical reduction strategy to synthesize various amorphous multimetallic Pd-based nanomaterials, including PdRu, PdRh, and PdRuRh. The phase-dependent catalytic performances of distinct Pd-based nanomaterials towards diverse catalytic applications have been demonstrated. Specifically, the usage of PdRu nanocatalysts with amorphous and crystalline face-centered cubic (fcc) phases can efficiently switch the ring-opening route of styrene oxide to obtain different products with high selectivity through alcoholysis reaction and hydrogenation reaction, respectively. Moreover, when used as an electrocatalyst for hydrogen evolution reaction (HER), the synthesized amorphous PdRh nanocatalyst exhibits low overpotential and high turnover frequency values, outperforming its crystalline fcc counterpart and most of the reported Pd-based HER electrocatalysts.
36 MATERIALS SCIENCE↗
Preparation, characterization, and structural studies of new ruthenium(II) and ruthenium(III) complexes incorporating pyrazole ligands
Multimetallic complexes containing disparate metals have been established to have practical utilities. We previously reported a strategy for preparing such species by using combinations of neutral pyrazole (Hpyz, C 3 N 2 H 4 ) and anionic pyrazolyl ligands (pyz, C 3 N 2 H 3 – ), and herein are reported several new complexes that should be capable of incorporating a second metal center. Two of the complexes, [Ru(1,5-cod)(Hpyz) 3 Cl][BPh 4 ] and Ru(1,5-cod)(Hpyz) 2 (pyz) 2 (cod = cyclooctadiene), were prepared from [Ru(cod)Cl 2 ] 2 , while [Ru(tmeda)(Hpyz) 2 Cl 2 ][BF 4 ] (tmeda = tetramethylethylenediamine) was prepared from the neutral Ru(II) complex Ru(tmeda)(Hpyz) 2 Cl 2 via one electron oxidation by the ferricinium ion. The first two complexes, one cationic and the other uncharged, involve Ru(II), while the tmeda complex involves Ru(III). Finally, all three species have been structurally characterized.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Symmetry in Seeded Metal Nanocrystal Growth
Symmetry underpins the structure and function of the world around us and is also captured in modern nanomaterials, where changing the symmetry of a nanocrystal or the interparticle spacing and orientation of nanocrystal building blocks in a superlattice can give new function. However, the synthesis and assembly of nanocrystals have been limited largely to simple compositions and structures. It remains a grand challenge to achieve nanocrystals with compositional and structural complexity while maintaining the monodispersity required for their use. This Account will illustrate through recent examples that seeded methods enable the synthesis of compositionally and structurally complex multimetallic crystals with defined and predictable symmetries for applications in plasmonics and catalysis. This outcome arises because the barrier for heterogeneous nucleation (i.e., seeded) is lower than that of homogeneous nucleation, where seeds can serve as preferential sites for the growth of complex structures and crystal phases. Our analysis begins by considering metal overgrowth from single-crystalline seeds of different shapes and symmetries, where the kinetics of adatom addition to seeds relative to their diffusion across seeds accounts for the expressed nanocrystal shapes. These results are then compared to overgrowth from seeds with different internal structures (i.e., planar defects), where the relationships between nanocrystal size and volumetric strain energy and surface energy are discussed. A major finding from this analysis is that often the underlying symmetry of seeds can be predictably transferred to the final crystals during overgrowth processes. Consequences of this finding are the predictable syntheses of crystals with different hierarchies akin to snowcrystals as well as nanocrystals with complex compositions (e.g., quaternary nanoparticles). Yet, there are subtle aspects to seeded growth that pave a path toward examples where nanocrystal symmetry has been reduced compared to the original seeds in a controlled manner. As we found, both the concentrations of metal precursors and capping agents can impact whether symmetry is transferred or reduced during overgrowth. Examples from our laboratory will be placed in context to other reported strategies for symmetry breaking. As will be argued, understanding what conditions favor symmetry preservation versus symmetry reduction during seeded crystal growth is central to accessing next-generation crystal forms. The Account concludes by outlining synthetic challenges associated with forming nanoscale heterostructures with precise 3-D placement of different materials within a given nanocrystal as well as facet control within different material domain and interface engineering. Furthermore, we envision meeting these challenges through regioselective and chemoselective seeded syntheses for which a foundation is outlined herein.
36 MATERIALS SCIENCE↗
Development of (NO)Fe(N 2 S 2 ) as a Metallodithiolate Spin Probe Ligand: A Case Study Approach
The ubiquity of sulfur–metal connections in nature inspires the design of bi- and multimetallic systems in synthetic inorganic chemistry. Common motifs for biocatalysts developed in evolutionary biology include the placement of metals in close proximity with flexible sulfur bridges as well as the presence of π-acidic/delocalizing ligands. This Account will delve into the development of a (NO)Fe(N 2 S 2 ) metallodithiolate ligand that harnesses these principles. The Fe(NO) unit is the centroid of a N 2 S 2 donor field, which as a whole is capable of serving as a redox-active, bidentate S-donor ligand. Its paramagnetism as well as the ν(NO) vibrational monitor can be exploited in the development of new classes of heterobimetallic complexes. We offer four examples in which the unpaired electron on the {Fe(NO)} 7 unit is spin-paired with adjacent paramagnets in proximal and distal positions. First, the exceptional stability of the (NO)Fe(N 2 S 2 )-Fe(NO) 2 platform, which permits its isolation and structural characterization at three distinct redox levels, is linked to the charge delocalization occurring on both the Fe(NO) and the Fe(NO) 2 supports. This accommodates the formation of a rare nonheme {Fe(NO)} 8 triplet state, with a linear configuration. A subsequent FeNi complex, featuring redox-active ligands on both metals (NO on iron and dithiolene on nickel), displayed unexpected physical properties. Our research showed good reversibility in two redox processes, allowing isolation in reduced and oxidized forms. Various spectroscopic and crystallographic analyses confirmed these states, and Mössbauer data supported the redox change at the iron site upon reduction. Oxidation of the complex produced a dimeric dication, revealing an intriguing magnetic behavior. The monomer appears as a spin-coupled diradical between {Fe(NO)} 7 and the nickel dithiolene monoradical, while dimerization couples the latter radical units via a Ni 2 S 2 rhomb. Magnetic data (SQUID) on the dimer dication found a singlet ground state with a thermally accessible triplet state that is responsible for magnetism. A theoretical model built on an H 4 chain explains this unexpected ferromagnetic low-energy triplet state arising from the antiferromagnetic coupling of a four-radical molecular conglomerate. For comparison, two (NO)Fe(N 2 S 2 ) were connected through diamagnetic group 10 cations producing diradical trimetallic complexes. Antiferromagnetic coupling is observed between {Fe(NO)} 7 units, with exchange coupling constants (J) of -3, -23, and -124 cm –1 for Ni II , Pd II , and Pt II , respectively. This trend is explained by the enhanced covalency and polarizability of sulfur-dense metallodithiolate ligands. A central paramagnetic trans-Cr(NO)(MeCN) receiver unit core results in a cissoid structural topology, influenced by the stereoactivity of the lone pair(s) on the sulfur donors. This {Cr(NO)} 5 radical bridge, unlike all previous cases, finds the coupling between the distal Fe(NO) radicals to be ferromagnetic (J = 24 cm –1 ). The stability and predictability of this S = 1/2 moiety and the steric/electronic properties of the bridging thiolate sulfurs suggest it to be a likely candidate for the development of novel molecular (magnetic) compounds and possibly materials. The role of synthetic inorganic chemistry in designing synthons that permit connections of the (NO)Fe(N 2 S 2 ) metalloligand is highlighted as well as the properties of the heterobi- and polymetallic complexes derived therefrom.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Efficient Control of Atom Arrangement in Ternary Metal Chalcogenide Nanoparticles Using Precursor Oxidation State
Controlling both the concentration and the distribution of elements in a given material is often crucial to extracting and optimizing synergistic properties of the various constituents. An interesting class of such multielement materials is metal chalcogenide nanoparticles, which exhibit a wide range of composition-dependent optoelectronic properties including both bandgap-mediated processes and localized surface plasmon resonance properties, each of which is useful in applications ranging from energy conversion to sensing. Because metal chalcogenide nanoparticles can support several different metal elements in a variety of chalcogen lattices, this material class has particularly benefited from the ability to control both atom concentration and atom arrangement to tailor final particle properties. The primary method to access complex, multimetallic chalcogenide particles is via a postsynthetic cation exchange strategy. One-pot syntheses have been less explored to access these complex particles, although this route is desirable for economy and scalability. In this work, we compare the composition and morphology outcomes from cation exchange and one-pot preparation approaches using a Cu/Ag/Se system, which is already known to exhibit both binary and ternary metal chalcogenide phases. We show that at similar concentrations of the two metal cations, initial reaction conditions for the one-pot method yield multicomponent nanoparticles, whereas cation exchange yields homogeneous ternary metal chalcogenide structures. We then show that by tuning the precursor oxidation state for the one-pot method, this approach can be used to access homogeneous ternary metal chalcogenide particles that are similar in atom arrangement to the particles obtained using cation exchange. Taken together, our results demonstrate reliable synthetic methods that yield a variety of controlled compositions and composition morphologies in the Cu/Ag/Se system. Importantly, we demonstrate that this entire collection of architectures can all be accessed via a one-pot method simply by modifying metal precursor chemistry. The mechanistic insights gained and the resulting streamlined syntheses outlined indicate pathways to easily scaled, highly tailorable syntheses for rapid translation into downstream technologies.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Mechanochemistry of Group 4 Element-Based Metal–Organic Frameworks
Mechanochemical synthesis is emerging as an environmentally friendly yet efficient approach to preparing metal-organic frameworks (MOFs). Herein, we report our systematic investigation on the mechanochemical syntheses of Group 4 element-based MOFs. The developed mechanochemistry allows us to synthesize a family of Hf 4 O 4 (OH) 4 (OOC) 12 -based MOFs. Integrating [Zr 6 O 4 (OH) 4 (OAc)12] 2 and [Hf 6 O 4 (OH) 4 (OAc) 12 ] 2 under the mechanochemical conditions leads to a unique family of cluster-precise multimetallic MOFs that cannot be accessed by the conventional solvothermal synthesis. Finally, extensive efforts have not yielded an effective pathway for preparing Ti IV -derived MOFs, tentatively because of the relatively low Ti-O bond dissociation energy.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗