Alloy Nanoparticles Research Articles

'Tearing Effect' of Alloy-Support Interaction for Alloy Redispersion in NiRu/TiO2 Hydrogenation Catalysts.

Supported alloy catalysts have been extensively applied to many significant industrial chemical processes due to the abundant active sites with distinguishable geometry and electron states. However, a detailed in-situ investigation of the interaction between support and alloy nanoparticles is still lacking. Here, a subversive 'tearing effect' on the interface of TiO2-supported NiRu alloy nanoparticles is in-situ discovered by environmental transmission electron microscopy (ETEM) with a dramatic redispersion process of alloy nanoparticles from ~25 nm to 2-3 nm under the repeated hydrogen reduction. Dual-driven by the distinct alloy-support interaction involving the restructuring of alloy nanoparticles and growth of TiOx overlayer, larger NiRu alloy nanoparticles spontaneously disintegrate into atoms migrating on support. Atoms are finally captured by the defects generated on TiO2 during the repeat reduction, which also confines the further growth of the newly alloy nanoparticles. Owing to this specific alloy-support interaction, smaller alloy nanoparticles on TiO2 support are much more stable than the bigger ones, which holds promise for industrial applications as durable catalysts. This novel metal-support interaction with the 'tearing effect' revealed on supported alloy catalysts provides new knowledge on the structure-performance relationships in all the alloy catalysts for hydrogenation reactions.

Thermal evolution of solid solution of silica-embedded AgPt alloy NPs in the large miscibility gap.

Understanding the phase behavior of immiscible elements in bimetallic nanomaterials is essential for controlling their structure and properties. At the nanoscale, the miscibility of these immiscible elements often deviates from their behavior in bulk materials. Despite its significance, comprehensive and quantitative experimental insights into the dynamics of the immiscible-to-miscible transition, and vice versa, remain limited. In this study, we investigate the nucleation and growth kinetics of silica-embedded AgPt nanoparticles (NPs) across a wide range of annealing temperatures (25 °C to 900 °C) to elucidate temperature-dependent nanoalloy phase transitions and NP size distribution. Our findings reveal that the alloy phase persists up to 400 °C, with a corresponding average NP size of ∼2 nm. Beyond this temperature, phase instability begins to occur. We propose a three-stage process of nucleation and growth: (1) initial AgPt nanoalloy formation during deposition, (2) growth via thermal energy-assisted diffusion up to 400 °C, and (3) Ag atom emission from the nanoalloy above 500 °C, indicating Ag diffusion towards the surface, followed by partial sublimation of Ag atoms at 900 °C. These results provide crucial insights into the thermal limits for the dealloying of NPs, growth kinetics, and phase stability or instability under varying thermal conditions.

Bimetallic AuPd alloy nanoparticles on TiO₂ nanotube arrays: a highly efficient photocatalyst for hydrogen generation.

Decoration of TiO2 nanotube (TNT) arrays by AuPd nanoparticles (NPs) produces a dramatic enhancement in the rate of hydrogen generation through photocatalytic water-splitting under solar illumination. XRD and TEM confirmed alloy formation in bimetallic AuPd NPs while XPS ruled out a core-shell architecture in the AuPd NPs. Well-dispersed, size-controlled AuPd NPs were formed by sequential physical vapor deposition of Au and Pd on TNTs followed by spontaneous thermal dewetting (TNT-AuPd). TNT-AuPd samples were characterized by small tensile microstrains. For comparison purposes and to derive physical insights, an identical method was used to form TNT-Au and TNT-Pd samples wherein TNTs were decorated by monometallic Au and Pd NPs respectively. In every case, an accumulation-type heterointerface between TiO2 and the metallic/bimetallic NPs was indicated by binding energy shifts in the Ti2p high resolution x-ray photoelectron spectra (HR-XPS). Initial and final state effects in the Au4f HR-XPS pointed to a large number of Au atoms in low coordinate sites such as edges, kinks and corners as well as a slower excited atom relaxation in the alloy. A similar preponderance of Pd atoms at low coordinate sites was found along with the presence of a small amount of palladium oxide. TNT-AuPd demonstrated the highest photocatalytic H₂ production rate of 2920 µmol g⁻¹ h⁻¹, which is 8.9 times higher than that of TNTs, 2.1 times that of TNT-Au, and 1.69 times that of TNT-Pd under solar illumination. We studied H₂ generation under UV-filtered solar illumination with TNT-AuPd outperforming monometallic Au- and Pd-NP decorated TNTs, which is attributed to the enhancement of the catalytic activity of Pd in an Au environment, the presence of Pd and Au atoms at low coordinate sites, and photoinduced electron transfer between TNTs and AuPd alloy NPs, where AuPd acts as an efficient electron sink, in turn reducing carrier recombination losses.

Influence of Synthesis Conditions on the Structure, Composition, and Electromagnetic Properties of FeCoSm/C Nanocomposites

New materials are actively being developed for use in various fields of electronics, as they can significantly improve the performance of electronic devices and prevent adverse effects. Such materials include nanocomposites, which include nanoparticles of magnetic metals and alloys in a non-magnetic polymer or carbon matrix. For the first time, we synthesized FeCoSm/C nanocomposites and studied the effect of synthesis conditions on their structure, composition, and electromagnetic properties. Thermogravimetric (TG) analysis and differential scanning calorimetry (DSC) analysis of the heating processes of nanocomposite precursors allowed optimizing the mode of IR processing of precursors. X-ray phase analysis (XPA) showed that nanoparticles of a solid-metal solution based on the FeCo structure are formed, and at temperatures above 700 °C, the formation of SmCo5-x alloy nanoparticles is also possible. As the synthesis temperature increases, the average size of nanoparticles of alloys containing Sm increases. The effect of the metal ratio in the precursor on the structure, composition, and electromagnetic properties of FeCoSm/C nanocomposites is analyzed. It has been established that the most promising of all the studied materials are those obtained at a temperature of 700 °C with a metal ratio of Fe:Co:Sm = 50:40:10.

Mechanical properties of High Entropy Alloy nanoparticles obtained by nanoindentation: A BCC HfNbZrTaTi and FCC FeNiCrCoCu case

Mechanical properties of High Entropy Alloy nanoparticles obtained by nanoindentation: A BCC HfNbZrTaTi and FCC FeNiCrCoCu case

Medium entropy alloy nanoparticles incorporated in ordered mesoporous carbons for enhanced electrocatalytic nitrate-to-ammonia conversion

Medium entropy alloy nanoparticles incorporated in ordered mesoporous carbons for enhanced electrocatalytic nitrate-to-ammonia conversion

Methanol-Tolerant Pd-Co Alloy Nanoparticles on Reduced Graphene Oxide as Cathode Catalyst for Oxygen Reduction in Fuel Cells

The design of efficient and cost-effective electrocatalysts to replace Pt in an oxygen reduction reaction (ORR) is crucial for advancing proton exchange membrane fuel cell (PEMFC) technologies. This study synthesized Pd-Co bimetallic alloy nanoparticles supported on reduced graphene oxide (rGO) through a simple chemical-reduction method, making it suitable for low-cost, large-scale fabrication and significantly reducing the need for Pt. The nanostructures were systematically characterized using various analytical techniques, including X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), and cyclic voltammetry (CV). Electrochemical investigations revealed that the Pd-Co/rGO catalyst exhibits remarkable ORR performance in an alkaline environment, with an electrode-area-normalized activity rivaling that of the commercial Pt/C catalyst. Remarkably, Pd-Co/rGO demonstrated an onset potential (Eonset) of 0.944 V (vs. RHE) and a half-wave potential (E1/2) of 0.782 V (vs. RHE), highlighting its excellent ORR activity. Furthermore, the Pd-Co/rGO catalyst displayed superior methanol-tolerant ORR activity, outperforming Pt/C and monometallic Pd/rGO and Co/rGO systems. The enhanced electrocatalytic performance is attributed to the smallest size, consistent shape, and good dispersion of the alloy structure on the RGO surface. These findings establish Pd-Co/rGO as a promising alternative to Pt-based catalysts, addressing key challenges such as methanol crossover while advancing PEMFC technology in alkaline media.

Platinum–Iridium–Ruthenium Trimetallic Alloy Nanoparticles as Catalysts for Oxygen and Hydrogen Evolution

Platinum–Iridium–Ruthenium Trimetallic Alloy Nanoparticles as Catalysts for Oxygen and Hydrogen Evolution

Macrophage-Mediated Liquid Metal Nanoparticles for Enhanced Tumor Accumulation and Inhibition.

In most studies, the penetration of nanoparticles into tumors was mainly dependent on the enhanced permeability and retention (ERP) effect. However, the penetration of nanoparticles would be limited by tumor-dense structure, immune system, and other factors. To solve these problems, macrophages with active tropism to tumor tissues, loaded nanoparticles with photothermal therapy, and chemotherapy were designed. In detail, liquid metal (gallium indium alloy) nanoparticles were modified with mesoporous silica and then embedded with the chemotherapeutic drug sorafenib (LM@Si/SO) for photothermal therapy and chemotherapy. After that, the LM@Si/SO nanoparticles were carried by the mouse macrophage RAW264.7 cell line (LM@Si/SO@R) to increase the accumulation of the nanoparticles in the tumor site and improve the tumor immune microenvironment. With the enhanced tumor accumulation, LM@Si/SO@R exhibited excellent antitumor ability in vitro and in vivo. Thus, these strategies via the cell carrier to enhance tumor therapeutic efficiency had the potential for the improvement of tumor therapy.

Strain Engineering of Ru–Co2Ni Nanoalloy Encapsulated with Carbon Nanotubes for Efficient Anion and Proton Exchange Membrane Water Electrolysis

AbstractAlloying atomically dispersed noble metals with earth‐abundant transition metal nanoparticles (NPs) presents a promising approach to enhance the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water electrolysis. However, the challenge remains of reducing the size of the NPs without sacrificing high activity and durability. In this study, Ru–Co2Ni nanoalloy particles (NAPs) encapsulated in nitrogen‐doped carbon nanotubes (NCNTs) are introduced, forming a core‐shell electrocatalyst (Ru–Co2Ni@NCNT). This design leverages Ru site optimization, CNT density control, strain engineering, efficient water dissociation, and outstanding bubble release dynamics within the core‐shell structure. These factors significantly improve catalytic performance with low overpotentials of 35 and 57 mV overpotential in 1.0 m KOH and 0.5 m H2SO4 solutions, respectively, at a current density of 10 mA cm−2. Density functional theory (DFT) calculations reveal that while Ru sites serve as active sites, they also modify the electronic structure of Co and Ni, optimizing their hydrogen adsorption energies and improving HER efficiency. The Ru–Co2Ni@NCNT catalyst is successfully integrated into both anion exchange membrane (AEM) and proton exchange membrane (PEM) electrolyzers, demonstrating stable operation at 0.5 A cm−2 for 500 h, underscoring its potential for efficient and durable hydrogen production.

Tuning metal-support interactions in MOF-derived CoNi@NC supported Pd catalysts for efficient hydrogenation of bicarbonate using glycerol as a hydrogen donor.

The hydrogenation of bicarbonate, a byproduct of CO2 captured in alkaline solutions, into formic acid (FA) using glycerol (GLY) as a hydrogen source offers a promising carbon-negative strategy for reducing CO2 emissions. While Pd-based catalysts are effective in this reaction, they often require high temperatures, leading to low FA yield due to strong hydrogen adsorption on Pd surfaces. In this work, metal-organic framework derived N-doped carbon encapsulated CoNi alloy nanoparticles (CoNi@NC) were prepared, acid-leached, and employed as a support to modulate the electronic structure of Pd-based catalysts. The electron transfer driven by the Mott-Schottky effect increases the electron density of Pd, lowers its d-band center, and thereby weakens hydrogen adsorption on Pd. Consequently, Pd/CoNi@NC achieved a full conversion of GLY with 87.2% yield of lactic acid and 57.3% yield of FA, outperforming Pd/NC and Pd/C. Additionally, Pd/CoNi@NC demonstrated high catalytic stability and was magnetically separable for ease of use.

Robust Spray Combustion Enabling Hierarchical Porous Carbon-Supported FeCoNi Alloy Catalyst for Zn-Air Batteries.

Rechargeable Zn-air batteries (RZABs) are poised for industrial application, yet they require low-cost, high-performance catalysts that efficiently facilitate both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The pivotal challenge lies in designing multimetal active sites and optimizing the carbon skeleton structure to modulate catalyst activity. In this study, we introduce a novel hierarchical porous carbon-supported FeCoNi bifunctional catalyst, synthesized via a spray combustion method. The carbon, derived from sucrose, was tailored into a hierarchical porous morphology through etching with NO3- ions and NaCl, thereby significantly increasing the surface area for the interaction of the O2 and electrolyte interaction. The in situ formation of FeCoNi alloy nanoparticles ensures their uniform dispersion and anchoring, facilitating electron transport. The strong interaction and charge transfer at the heterogeneous FeCoNi alloy interfaces, along with nitrogen doping, which enhances the OER/ORR activity, endow the FeCoNi/N-PC catalyst with exceptional bifunctional catalytic properties, characterized by an activity parameter of 0.73 V. Furthermore, the RZAB assembled with this catalyst demonstrates outstanding cycling stability and reversibility, with a minimal round-trip efficiency decay of 7.6% over 1380 cycles (460 h) at 10 mA cm-2.

Synthesis of IrCu/Co3O4 hybrid nanostructures and their enhanced catalytic properties toward oxygen evolution reaction under both acidic and alkaline conditions.

Oxygen evolution reaction (OER) is a half-reaction that occurs at the anode during water electrolysis, and owing to its slow kinetics, it is the rate-limiting step in the process. Alloying with transition metal and combining with transition metal oxide supports are effective methods for modifying the electronic structure of noble metal catalysts and improving their catalytic properties. In this study, we synthesized IrCu/Co3O4 hybrid nanostructures by attaching IrCu alloy nanoparticles onto Co3O4 nanosheets. The electron transfer from Ir to Co altered the electronic structure of IrCu and became a crucial factor for the enhanced catalytic activity of the IrCu/Co3O4 hybrid nanostructure in the OER reaction. Additionally, the hybrid nanostructure demonstrated excellent catalytic stability under both alkaline and acidic conditions (135 and 60 h at 10 mA cm-2, respectively) due to its combination with Co3O4 nanosheets. The present work paves a new approach for the design and construction of efficient pH-universal electrocatalysts for OER.

Efficient Nitrate to Ammonia Conversion on Bifunctional IrCu4 Alloy Nanoparticles.

Electrochemical nitrate reduction (NO3RR) to ammonia presents a promising alternative strategy to the traditional Haber-Bosch process. However, the competitive hydrogen evolution reaction (HER) reduces the Faradaic efficiency toward ammonia, while the oxygen evolution reaction (OER) increases the energy consumption. This study designs IrCu4 alloy nanoparticles as a bifunctional catalyst to achieve efficient NO3RR and OER while suppressing the unwanted HER. This is achieved by operating the NO3RR at positive potentials using the IrCu4 catalyst, which allows a Faradaic efficiency of 93.6% for NO3RR. When applied to OER catalysis, the IrCu4 alloy also shows excellent results, with a relatively low overpotential of 260 mV at 10 mA cm-2. Stable ammonia production can be achieved for 50 h in a 16 cm2 flow electrolyzer in simulated working conditions. Our research provides a pathway for optimizing NO3RR through bifunctional catalysts in a tandem approach.

Tuning Dual Catalytic Active Sites of Pt Single Atoms Paired with High-Entropy Alloy Nanoparticles for Advanced Li-O2 Batteries.

To achieve a long cycle life and high-capacity performance for Li-O2 batteries, it is critical to rationally modulate the formation and decomposition pathway of the discharge product Li2O2. Herein, we designed a highly efficient catalyst containing dual catalytic active sites of Pt single atoms (PtSAs) paired with high-entropy alloy (HEA) nanoparticles for oxygen reduction reaction (ORR) in Li-O2 batteries. HEA is designed with a moderate d-band center to enhance the surface adsorbed LiO2 intermediate (LiO2(ads)), while PtSAs active sites exhibit weak adsorption energy and promote the soluble LiO2 pathway (LiO2(sol)). An optimal ratio between LiO2(ads) and LiO2(sol) pathway was realized to modulate PtSAs and HEA active sites via regulating the etching conditions in the dealloying synthesis process for obtaining high-performance Li-O2 batteries. The ORR kinetics are accelerated, and the parasitic reactions are restrained in the Li-O2 batteries. As a result, Li-O2 batteries based on the HEA@Pt-PtSAs catalyst demonstrate an ultralow overpotential (0.3 V) and ultralong cycling performance of 470 cycles at 1000 mA g-1. The insights into the synthetic strategies and the importance of balancing the ORR pathways will offer guidance for devising multisite synergistic catalysts to accelerate redox-reaction kinetics for Li-O2 batteries.

Enhancing the CO Oxidation Performance of Copper by Alloying with Immiscible Tantalum.

Copper-tantalum (Cu-Ta) immiscible alloy nanoparticles (NPs) have been the subject of extensive research in the field of structural materials, due to their exceptional nanostructural stability and high-temperature creep properties. However, Cu is also a highly active oxidation catalyst due to its abundant valence changes. In this study, we have for the first time obtained homogeneous CuxTa1-x (x = 0.5, 0.7, 0.9, 1) nanoparticles by wet coreduction with an average particle size of approximately 30 nm. Testing verified all the CuxTa1-x/TiO2 (x = 0.5, 0.7, 0.9) showed higher CO oxidation activity than Cu/TiO2, with Cu0.7Ta0.3/TiO2 exhibiting the most promising performance. The temperature-programmed reduction with hydrogen demonstrated that Cu0.7Ta0.3/TiO2 exhibits enhanced redox properties. While kinetic studies indicated that the reaction of the Cu0.7Ta0.3/TiO2 catalyst followed the Langmuir-Hinshelwood mechanism, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) verified the introduction of Ta induced the generation of bicarbonate as an intermediate product and increased the adsorption capacity of Cu+ on CO in the catalyst, which facilitated the reaction of surface adsorbed CO with oxygen and led to the enhanced CO oxidation activity.

Revealing Multistep Phase Separation in Metal Alloy Nanoparticles with In Situ Transmission Electron Microscopy.

Phase separation plays a crucial role in many natural and industrial processes, such as the formation of clouds and minerals and the distillation of crude oil. In metals and alloys, phase separation is an important approach often utilized to improve their mechanical strength for use in construction, automobile, and aerospace manufacturing. Despite its importance in many processes, the atomic details of phase separation are largely unknown. In particular, it is unclear how a different crystal phase emerges from the parent alloy. Here, using real-time in situ transmission electron microscopy, we describe the stages of the phase separation in face-centered cubic (fcc) AuRu alloy nanoparticles, resulting in a Ru phase with a hexagonal close-packed (hcp) crystal structure. Our observation reveals that the hcp Ru phase forms in two steps: the spinodal decomposition of the alloy produces metastable fcc Ru clusters, and as they grow larger, these clusters transform into hcp Ru domains. Our calculations indicate that the primary reason for the fcc-to-hcp transformation is the size-dependent competition between the interfacial and bulk energies of Ru domains. These insights into elusive, transient steps in the phase separation of alloys can aid in engineering nanomaterials with unconventional phases.

Nanoalloys Composed of Platinum Group Metals and p‐Block Elements for Innovative Catalysis

Alloy nanoparticles based on platinum group metals (PGMs) have been intensively investigated in various fields, especially in catalysis. Recently, the scope of alloying has expanded to include not only d‐block transition metals but also p‐block elements, which have a wide range of properties that are very different from those of d‐block transition metals. By alloying PGMs with p‐block elements, the electronic structure and surface properties of the catalysts can be tuned, enhancing their catalytic performance. The focus of this review is on PGM–p‐block element nanoalloys, their synthesis methods, characterization techniques, and catalytic properties. In addition to typical binary crystalline alloys, such as solid‐solution and intermetallic alloys, this review also highlights the potential of multielement, amorphous, or liquid alloys, which have recently garnered much attention. The review aims to provide valuable perspectives for the development of PGM‐based sustainable and innovative catalysis, while also addressing the current challenges and future directions in this field.

Investigation of catalytic efficiency of nanoparticles of alloys on thermal behavior of AP and AP-based solid propellants

In this article, we present the catalytic proficiency of three different nano metal alloys Cu–Co, Cu–Fe, and Cu–Zn) on thermal behavior of powder ammonium perchlorate (AP) and composite solid propellants (CSPs) samples. A hydrazine reduction method was used for synthesized Cu–Co, Cu–Fe, Cu–Zn alloys nanoparticles and they were characterized by XRD, FTIR, and SEM. The catalytic impact of nano alloys on thermal behavior AP and CSPs is established by implementing through TG-DSC technique. The Kissinger Akahira Sunose (KAS), Flynn wall Ozawa (FWO), and Starink methods were used to determine activation energies of all AP and CSPs samples. The Cu–Zn Nanoalloys acted as good catalyst for thermal decomposition of AP and CSPs and it reduced the decomposition temperature and activation energy of AP and CSPs. It increased the burning rate of CSPs.

Interfacial Anisotropy‐Induced Enhanced Exchange Bias in FeCo Alloy Nanoparticles

Interfacial Anisotropy‐Induced Enhanced Exchange Bias in FeCo Alloy Nanoparticles