Bimetallic Nanoalloys Research Articles

Enhanced catalytic reduction of Cr(VI) with formic acid over spherical bimetallic Ni-Co nanoalloy catalysts at room temperature

Exploring high-efficiency and low-cost catalysts for reducing Cr(VI) is one of the key problems in solving Cr(VI)-containing wastewater. In this paper, bimetallic Ni- and Co-based carbon sphere (NixCoy@NCS) was prepared by a simple hydrothermal-pyrolysis route, in which Ni-Co nanoalloys were uniformly dispersed on N-doped carbon sphere with average nanoparticles of 37.5 nm. The catalytic reduction performance of the hybrid catalyst NixCoy@NCS for Cr(VI) can be optimized by manipulation stoichiometry, and the catalytic ability of the Ni1Co1@NCS was much higher than that of other samples. This is because the synergy between Co and Ni NPs promotes the dehydrogenation efficiency of formic acid and the N doping improves the electron transport efficiency of the catalyst, and the strong protection of N-doped carbon for NPs ensured its excellent recycling ability and durability. In the existence of coexisting ions, the catalytic efficiency of the Ni1Co1@NCS is not affected at all. The reduction mechanism is mainly because of the active hydrogen during the dehydrogenation pathway of formic acid. This paper demonstrates that bimetallic Ni-Co-based materials have higher catalytic capacity than monometallic Ni or co-based materials.

Unveiling the nanoalloying modulation on hydrogen evolution activity of ruthenium-based electrocatalysts encapsulated by B/N co-doped graphitic nanotubes

Efficiency of the electrocatalysts for hydrogen evolution reaction (HER) strongly depends on their extrinsic physical properties and intrinsic electronic structures. Among various modulation strategies, nanoalloying is an efficient route to regulate the intrinsic activities of HER intermediates. Herein, we develop a facile and universal one-step pyrolyzed method to fabricate bimetallic Ru-based nanoalloy catalysts encapsulated by B/N co-doped graphitic nanotubes (RuM@BCN, M=Ir, Pt, Ag, Co, and Fe) for high-performance alkaline HER. BCN nanotube substrates provide sufficient open channels, porous structures and strong anchoring effect to achieve fast kinetics and high stability. The bimetallic nanoalloying strategy greatly promotes the water dissociation and hydrogen adsorption ability of the electrocatalysts via modulation on their intrinsic electronic structures. Therefore, the as-made RuM@BCN demonstrates varied HER behaviors by alloying metals, in which RuIr@BCN exhibits the highest alkaline HER activity with an overpotential of 23.6 mV at the current density of 10 mA cm−2, outperforming commercial Pt/C.

Chloride-Derived Bimetallic Cu-Fe Nanoparticles for High-Selective Nitrate-to-Ammonia Electrochemical Catalysis

Cu-based bimetallic materials have been widely reported as efficient catalysts for electrocatalytic nitrate reduction. However, the faradaic efficiency and selectivity are still far from satisfactory. Herein, Cu-Fe bimetallic nanoalloys with adjustable Cu/Fe ratios are successfully prepared through a reactive mechanical milling approach with CuCl2, FeCl3 and Na as the starting materials. The optimized Cu3Fe exhibits excellent nitrate conversion efficiency of 81.1% and 70.3% ammonia selectivity at −0.7 V vs. RHE within 6 h under 0.1 M Na2SO4 and 100 ppm NO3−. The Fe-introduction-induced upshift of the d-band center is identified to be beneficial for promoting nitrate adsorption on Cu3Fe. Moreover, favorable H generation under the assistance of Fe could effectively accelerate the stepwise hydrogenation during electrocatalytic nitrate reduction, resulting in significantly improved NH4+ selectivity. This work supplies valuable insights for the rational design of transition-metal-based bimetallic catalysts for electrocatalytic nitrate reduction.

Probing Optical Nonlinearities of Unconventional Glass Nanocomposites Made of Ionic Liquid Crystals and Bimetallic Nanoparticles.

In this paper, we report the synthesis and characterization of unconventional nanocomposites made of bimetallic nanoparticles dispersed in a liquid crystal glass. Core-shell bimetallic nanoparticles (Ag/Au or Au/Ag) and Ag-Au bimetallic nanoalloys are synthesized using cadmium alkanoate glass-forming liquid crystals as nanoreactors. Optical spectra of the produced glassy nanocomposites exhibit a distinctive absorption peak due to a surface plasmon resonance. In addition, these unusual materials demonstrate a strong nonlinear–optical response probed by means of the Z-scan technique. The use of near-infrared (1064 nm) and visible (532 nm) nanosecond laser pulses reveal a variety of nonlinear–optical mechanisms that depend on the composition of the studied nanocomposites. Our results indicate that metal alkanoate-based glass-forming ionic liquid crystals with embedded plasmonic nanoparticles are promising, yet they are overlooked photonic nanomaterials suitable for optical and nonlinear-optical applications.

Design of Co-Sn bimetallic nanoalloys as electrocatalyst for alkaline methanol oxidation reaction: Exploring the effect of electroactivation process

The engineering of cost-effective and durable electrocatalysts for the methanol oxidation reaction (MOR) is required for the commercialization of direct methanol fuel cells (DMFCs). Herein, a series of Cox-Sn100-x alloy nanoparticles were synthesized to optimize the Co/S ratio, and the alloy nanoparticle which offered the best electrochemical performance towards MOR was employed as electrocatalyst for further experiments. Moreover, two different electroactivation approaches including i) activation in phosphate buffer medium, and ii) in-situ activation were explored to enlighten their effect on electrochemical characteristics of nanocatalyst. In this regard, the chronoamperometry measurements were carried out at a constant potential over a fixed period of 300 s. Additionally, the pH of the phosphate buffer solution in a range of 3–12, the activation potential ranging −0.7 V to −2.0 V were optimized by evaluating the recorded cyclic voltammograms. Moreover, to predict the effect of phosphate buffer pH in the activation process on the electrocatalytic activity of catalyst were artificial neural network (ANN) approach was implemented. Amongst the various nanoalloys, Co65-Sn35 nanoparticles were determined as the optimal one thanks to their uniform dispersion and less aggregation feature. In the activation process with phosphate buffer at pH of 10 was determined as the optimal, and at this condition a hydrogen evolution reaction also occurred in the range of applied activation potential. The findings revealed that activation in phosphate buffer solution led to the formation of more –OH species, thereby boosting the electrocatalytic activation towards MOR in alkaline media. Similarly, for the in-situ activation approach, the optimum potential was determined as −1.3 V to achieve the maximum current density. The findings offered that the electroactivation in phosphate buffer solution (pH = 10) at −1.3 V could result in a highly active electrocatalyst to be utilized in alkaline DMFCs. This research lays the door for tailoring high-performance, low-cost electrocatalysts that could be used in energy conversion systems instead of commercial noble-metal-based electrocatalysts.

Control of cluster coalescence during formation of bimetallic nanoparticles and nanoalloys obtained via electric explosion of two wires

In this study, the possibility of controlling the coalescence of clusters during the formation of bimetallic nanoparticles and nanoalloys is demonstrated for the first time using joint electric explosion of Nb/Al and Nb/Ag wires under an argon atmosphere as an example. The evolution of clusters in the condensed phase is considered based on the adiabatic approximation to expand the products of the electric explosion of wires. Controlling the temperature and size of the clusters formed under the electric explosion of wires generating the energy necessary for the transition from the metallic state to the two-phase state (clusters of the condensed phase and weakly ionized plasma) allows synthesizing nanoparticles and bimetallic nanoparticles possessing the structures of nanoalloys and Janus particles, respectively. The experimental studies are supplemented by describing structural patterns and segregation phenomena using a hybrid computer experiment that adopts two alternative methods, i.e., the Monte Carlo and molecular dynamics methods. Both methods predict similar structure formation trends, particularly segregation patterns, in Nb–Ag and Nb–Al nanoparticles. For the first time, we have obtained bimetallic nanoparticles possessing a more complex structure, compared to the formerly known core shell, namely the onion-like structure. The Nb2964–Ag2964 and Nb2964–Al2964 nanoparticles s are characterized by the formation of icosahedral cores and crystalline cores based on the hcp and fcc phases, respectively, over the entire temperature range studied.

Mizoroki–Heck coupling reaction on the surface of sepiolite clay-supported Pd/Cu nanoalloy

Well distributed Pd/Cu bimetallic nanoalloy supported on acid-modified sepiolite (ASEP) was prepared via a solvothermal process. The resulting system, Pd/Cu@ASEP, was characterized using spectroscopic data such as FT-IR, XRD, TEM and ICP-AES. The morphology characterization revealed that the crystalline bimetallic particles were dispersed on ASEP as nanoalloys with diameters ranged from 25 to 30 nm. This system was successfully used for ligand-free Mizoroki-Heck coupling in the presence of air, under mild conditions. This method has advantages compared to other systems, such as short reaction times, high yields, facile catalyst and easy separation and reusability of the catalyst. The catalyst was compatible with a variety of aryl and heteraryl iodides, which provides favorable products with good to high yields. Aryl and heteraryl bromides could also be activated for the Mizoroki-Heck reaction using Pd/Cu@ASEP catalyst, with good to moderate yields.

Structural, mixing, electronic and magnetic properties of small Cu-Pd nanoalloy clusters

Bimetallic CumPdn nanoalloy clusters of small size (m+n ≤ 12) are systematically studied using the spin polarized density functional theory to understand the evolution of structural, mixing, electronic and magnetic properties with size and composition of the binary system. The lowest-energy configurations of the series of bimetallic clusters are determined from unbiased global search with genetic algorithm. With the increase of size, Cu-Pd clusters tend to adopt compact geometries. For a given cluster size, Pd atom prefers the outer position, while Cu atom favors the inner site. Stability analysis reveals that nanoalloy formation for CumPdn clusters is favored for the overall range of sizes and compositions. The small changes in structures of magic clusters with their neighboring compositions indicate that their high stability is primarily due to the variation in composition, not to the change in structure. The electronic state of the Pd atom is promoted upon the formation of the Cu-Pd nanoalloy clusters, while that of the Cu atom remains almost unchanged. The magnetic moments of CumPdn clusters exhibit an evident oscillation behavior with the composition, which can be attributed to the substantial hybridization between the electronic states of Pd and Cu.

Carbon encapsulated bimetallic FeCo nanoalloys for one-step hydroxylation of benzene to phenol

Carbon encapsulated iron catalysts hold great potential for one-step hydroxylation of benzene to phenol due to their unique core-shell nanostructures. However, their catalytic performance is moderate, since the carbon shells have impeded their activity toward H2O2 activation. Herein, we demonstrate that alloying engineering of Fe cores with Co atoms is a promising strategy to address the issue about H2O2 activation. The incorporation of Co into Fe cores can generate strong synergetic effects to promote H2O2 activation, while still maintaining the structural benefits of carbon shells for benzene hydroxylation reaction. As a result, the phenol yield obtained on carbon encapsulated FeCo (FeCo@C) reaches to 26.4 ± 0.7% with a selectivity of 96.2 ± 1.2%, much higher than that of Fe@C and Co@C. With the improved intrinsic catalytic behavior toward H2O2 activation and well-reserved carbon structure benefits, FeCo@C should be a promising catalyst for a broad liquid-phase reactions using H2O2 as the oxidant.

Single-Atom and Bimetallic Nanoalloy Supported on Nanotubes as a Bifunctional Electrocatalyst for Ultrahigh-Current-Density Overall Water Splitting

Single-Atom and Bimetallic Nanoalloy Supported on Nanotubes as a Bifunctional Electrocatalyst for Ultrahigh-Current-Density Overall Water Splitting

Modeling to determine the size dependence of Debye temperature in monometallic and bimetallic nanoalloys

A simple unified model is used to study the variation in Debye temperature in monometallic and bimetallic nanoalloys. In the present study, a systematic investigation of variation in Debye temperature is done to analyze the impact of size, shape, composition and dimension in monometallic and bimetallic nanoalloys. It is found that Debye temperature in monometallic and bimetallic nanoalloys decreases with decrease in size of nanoalloy. Moreover, for nanoalloys of same size and composition, the Debye temperature varies with dimension too. Debye temperature of nanofilms is found more than that of nanowires and nanoparticles. Debye temperature is also found to vary with shape of the nanoalloy due to change in surface area to volume ratio with shape. The predicted model results are found in good agreement with the available experimental results which justifies the suitability of the present model.

Evaluation of Cu-Ag Bimetallic Nanoalloys as Antibacterial, Antidiabetic, Anticancerous Drug Biosynthesized from Curcuma aromatica

Drug resistant strains are formed due to unsuitable uses of antibiotics and insufficient check of infections. In present years, due to the extensive antimicrobial properties, metallic nanoparticles and metallo-pharmaceutics are highly proposed. Therefore, the synthesis of bimetallic nanoparticles are exploring towards the evolution of more productive amalgamative antimicrobials composed of combined metals. In this study, the green synthesis of Cu-Ag bimetallic nano-alloys using aqueous extract from the leaves of Curcuma aromatica is carried out. Synthesized Cu-Ag nano-alloys were characterized by UV-visible spectroscopy, scanning electron microscope (FE-SEM), transmission electron microscope (TEM-EDAX), cyclic voltammogram (CV). The characterization studies reveals that the biosynthesis produced core-shell Cu-Ag nano-alloys with spherical shape and average diameter size of 15 nm. The synthesized Cu-Ag nanoalloys exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria. The antidiabetic potential of Cu-Ag nanoalloys shows an effective inhibition against α-glucosidase. Anticancerous activity of Cu-Ag nanoalloys indicates its greater efficacy in destroying cancer cells. The biosynthesis of Cu-Ag nanoalloys can be employed in medical and industrial fields on a large scale with cost reductive method.

Graphitic nanofibers supported NiMn bimetallic nanoalloys as catalysts for H2 generation from ammonia borane

Bimetallic nickel manganese nanoalloy-decorated graphitic nanofibers were prepared using electrospinning. The introduced catalysts were explored as an effective and inexpensive catalyst for H2 generation from ammonia borane using hydrolysis. Standard techniques were used to determine the morphology and chemical composition of the nanofibers. Characterization indicated successful formation of bimetallic nickel-manganese-decorated graphitic nanofibers. Introduced effective catalysts showed a high reusability for H2 generation using ammonia borane hydrolysis at low concentrations and temperatures. All formations of the introduced catalysts demonstrated a higher catalytic activity in H2 generation than nickel-decorated carbon nanofibers. Samples composed of 55 wt% nickel and 45 wt% manganese showed the best catalytic activity compared with other formulations. Initial turnover frequency (TOF) of this sample was 58.2 min−1, twice the TOF of the manganese-free catalyst. Kinetics and thermodynamics revealed that the catalyst concentration followed the pseudo-first order reaction while the ammonia borane concentration follow the pseudo-zero order reaction, providing activation energy of 38.9 kJ mol−1.

AuPt bimetallic nanoalloys supported on SBA-15: A superior catalyst for quinoline selective hydrogenation in water

AuPt bimetallic nanoalloys supported on SBA-15: A superior catalyst for quinoline selective hydrogenation in water

One-pot synthesis of CuBi bimetallic alloy nanosheets-supported functionalized multiwalled carbon nanotubes as efficient photocatalyst for oxidation of fluoroquinolones

With a broader objective to replace Au, Pt, and Ag-based photocatalysis, a new low-cost bimetallic nanoalloy of CuBi has been fabricated in situ on carboxylated MWCNTs by a facile reduction route. The physicochemical properties of CuBi-nanoalloy/MWCNTs have been thoroughly investigated through the characterization techniques, i.e. XRD, XPS, FE-SEM, TEM, UV − vis diffuse reflectance and photoluminescence spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. FE-SEM and TEM study confirm the growth of ultrathin 2D nanosheets of CuBi-alloy, which were uniformly distributed on the CNTs bundles. The visible light-driven photocatalytic removal of fluoroquinolone-type antibiotics (Ciprofloxacin and Ofloxacin) was dramatically enhanced on the CuBi-modified nanotubes compared with pure CNTs. The synergistic effects of SPR effect of Cu, the intimate contact between the CuBi alloy and the nanotubes, the boosting of hot electron flux at the Schottky junction, and the higher oxidative activity lead to high photocatalytic oxidation rate of the CuBi-nanoalloy/MWCNTs.

Electrochemical Synthesis of γ-Cu5Zn8 Bimetallic Nano Alloy for Efficient Degradation of Methyl Orange Dye and Antimicrobial Efficacy

Electrochemical Synthesis of γ-Cu5Zn8 Bimetallic Nano Alloy for Efficient Degradation of Methyl Orange Dye and Antimicrobial Efficacy

Structural and dynamical properties of Au-Pd bimetallic nanoalloys supported on MgO(001)

ABSTRACT In this study, structural and dynamical properties of Au-Pd bimetallic nanoalloys supported on MgO(001) surface were investigated. Bimetallic nanoalloys were defined with three different compositions that represents 1:1(50%–50%), 1:3(25%–75%) and 3:1(75%–25%). The putative global minimum structures of bimetallic Au-Pd nanoalloys adsorbed on MgO(001) were examined. It was obtained that Au and Pd nanoparticles exhibit a preference both (001) and (111) epitaxial grown on MgO(001) and Au-Pd bimetallic nanoalloys favour (001) epitaxy on MgO(001). The obtained lowest energy structures were used initially for melting simulations. The melting temperatures of AunPd3n nanoalloys were obtained generally higher than the melting temperatures of AunPdn and Au3nPdn nanoalloys. Highlights Structural and dynamical properties of Au-Pd bimetallic nanoalloys supported on MgO(001) surface were investigated. Au and Pd nanoclusters exhibit a preference both (001) and (111) epitaxial grown on MgO(001) and Au-Pd bimetallic nanoalloys favour (001) epitaxy on MgO(001). The melting temperatures of AunPd3n nanoalloys were obtained generally higher than the melting temperatures of AunPdn and Au3nPdn nanoalloys.

Bimetallic nano alloy architecture on a special polymer: Ni or Cu merged with Pd for the promotion of the Mizoroki–Heck reaction and the Suzuki–Miyaura coupling

Novel Ni-Pd and Cu-Pd bimetallic nano alloys was designed and heterogenized on the highly robust ABPBI [poly(2,5-benzimidazole)] polymer in high yields using NaBH4 as reducing agent. These were versatile ligand free catalysts for the Mizoroki–Heck reaction and Suzuki–Miyaura coupling. The bimetallic Ni-Pd-ABPBI catalyst for the Mizoroki–Heck reaction of 4-iodo anisole could be recycled 5 times with high yields. Aryl bromides could also be activated for the Mizoroki–Heck reaction using Cu-Pd-ABPBI NP catalysts, with moderate yields. Synopsis Novel bimetallic Ni-Pd and Cu-Pd nano alloys, heterogenized on the robust ABPBI [poly(2,5-benzimidazole)] polymer using NaBH4 as reducing agent, is described. These were versatile ligand free, noble metal conservative catalysts, for the Mizoroki–Heck reaction and the Suzuki–Miyaura coupling. Aryl bromides were activated for the Mizoroki–Heck reaction using the Cu-Pd-ABPBI catalyst.

H2 In Situ Inducing Strategy on Pt Surface Segregation Over Low Pt Doped PtNi5 Nanoalloy with Superhigh Alkaline HER Activity

AbstractSurface segregation constitutes an efficient approach to enhance the alkaline hydrogen evolution reaction (HER) activity of bimetallic PtxNiy nanoalloys. Herein, a new strategy is proposed by utilizing the small gas molecule of H2 as the structure directing agent (SDA) to in situ induce Pt surface segregations over a series of PtNi5‐n samples with extremely low Pt doping (Pt/Ni = 0.2). Impressively, the sample of PtNi5‐0.3 synthesized under 0.3 MPa H2 delivers an extremely low overpotential of 26.8 mV (−10 mA cm−2) and Tafel slope of 19.2 mV dec−1, which is superior to most of the previously reported PtxNiy electrocatalysts. This is substantially related to the strong H2 in situ inducing effect to generate Pt‐rich@Ni‐rich core‐shell nanostructure of PtNi5‐0.3 with an ultrahigh Pt surface content of 46%. The specific mechanistic effects of H2 during the PtNi5‐n synthesis process are well illustrated based on the combined experimental and theoretical studies. The density functional theory mechanism simulations further unravel that the evolved active site of PtNi5‐n can efficiently reduce the reaction Gibbs free energies; especially for the scenario of PtNi5‐0.3, the downward‐shifted d band center of the Pt active site significantly reduces the PtH bond strength, eventually resulting in the lowest absolute value of ΔGH.

Composition and dimension dependence of melting temperature in bimetallic nanoalloys

The phenomological model for cohesive energy of metallic nanomaterials is extended to investigate the variation in thermodynamic properties of bimetallic nanostructures. The systematic investigation of variation in melting temperature of bimetallic nanomaterials is done to study the impact of size, composition and dimension. Decrease in melting temperature of bimetallic nanoalloys is found as size of nanoalloy decreases. It is noted that for bimetallic nanoalloys of same composition and having same size, the melting temperature varies on the basis of dimension of nanoalloy in the sequence such that (Tmn)nanofilms> (Tmn)nanowires> (Tmn)nanoparticles. The present predicted results obtained from extended model are compared with the simulated and experimental results available. Good consistency is observed between the compared results which justify the present model theory.