Bimetallic Nanocatalysts Research Articles

Highly dispersed Pd-Cu bimetallic nanocatalyst based on γ-Al2O3 combined with electrocatalytic in-situ hydrogen production for nitrate hydroreduction

Bimetallic catalyst exhibits efficient and potential performance for nitrate reduction towards N2 generation. In this work, Pd-Cu bimetallic catalysts are synthesized based on γ-Al2O3 with different loading sequences and annealing temperatures. The characterization of the catalysts with XRD and STEM indicates that the loading methods affect the dispersity of the catalysts. The catalyst obtains much smaller size and more uniform dispersion by first Cu load with annealing at 900 °C and then Pd load (Cu1%(900 °C)-Pd2.5%/γ-Al2O3). The dispersion of Pd and Cu reach 51.81% and 21.93%, respectively. Then the catalysts are applied for nitrate hydroreduction combined with electrocatalytic in-situ hydrogen production using PPy/Ni cathode to obtain high efficiency of H2 utilization and N2 selectivity. For Cu1%(900 °C)-Pd2.5%/γ-Al2O3, the initial reaction rate for N2 generation is 0.70 mg L−1 min−1 and the TOF based on Pd is 2.13 × 10−3 s−1, which is much higher than the others, due to the best dispersion of Pd-Cu on the support. The loading amount is also optimized and the effects of current and pH are investigated to achieve the optimal performance.

Single-Molecule Nanocatalysis Reveals the Kinetics of the Synergistic Effect Based on Single-AuAg Bimetal Nanocatalysts.

Decades of extensive research efforts by scientists in the field of catalysis and nanomaterials have led to a large number of excellent bimetallic nanocatalysts. However, in many cases, the mechanism of the synergistic effect in bimetal catalyst-catalyzed reactions has been systematically neglected due to technical limitations. Herein, we use single-molecule fluorescence microscopy (SMFM) to reveal the mechanism of the synergy of the Au and Ag bimetal catalyst. Compared with that of the Ag nanocatalyst, the incorporation of Au changes the reaction pathway of Amplex Red and H2O2 from a noncompetitive to a competitive reaction mechanism, showing much higher catalytic efficiency. Additionally, the incorporation also inhibits the spontaneous surface reconstruction and facilitates the reaction-induced surface restructuring of the nanocatalyst, resulting in the enhancement of stability and reactivity. These findings provide useful insights into tailoring the reactivity of metal catalysts. This work also confirms the power of SMFM in revealing the origin of the catalytic activity of composite catalysts.

Tracking heterogeneous structural motifs and the redox behaviour of copper-zinc nanocatalysts for the electrocatalytic CO2 reduction using operando time resolved spectroscopy and machine learning.

Copper-based catalysts are established catalytic systems for the electrocatalytic CO2 reduction reaction (CO2RR), where the greenhouse gas CO2 is converted into valuable industrial chemicals, such as energy-dense C2+ products, using energy from renewable sources. However, better control over the catalyst selectivity, especially at industrially relevant high current density conditions, is needed to expedite the economic viability of the CO2RR. For this purpose, bimetallic materials, where copper is combined with a secondary metal, comprise a promising and a highly tunable catalyst for the CO2RR. Nevertheless, the synergy between copper and the selected secondary metal species, the evolution of the bimetallic structural motifs under working conditions and the effect of the secondary metal on the kinetics of the Cu redox behavior require careful investigation. Here, we employ operando quick X-ray absorption fine structure (QXAFS) spectroscopy coupled with machine-learning based data analysis and surface-enhanced Raman spectroscopy (SERS) to investigate the time-dependent chemical and structural changes in catalysts derived from shape-selected ZnO/Cu2O nanocubes under CO2RR conditions at current densities up to −500 mA cm−2. We furthermore relate the catalyst transformations observed under working conditions to the catalytic activity and selectivity and correlate potential-dependent surface and subsurface processes. We report that the addition of Zn to a Cu-based catalyst has a crucial impact on the kinetics of subsurface processes, while redox processes of the Cu surface layer remain largely unaffected. Interestingly, the presence of Zn was found to contribute to the stabilization of cationic Cu(i) species, which is of catalytic relevance since Cu(0)/Cu(i) interfaces have been reported to be beneficial for efficient electrocatalytic CO2 conversion to complex multicarbon products. At the same time, we attribute the increase of the C2+ product selectivity to the formation of Cu-rich CuZn alloys in samples with low Zn content, while Zn-rich alloy phases result in an increased formation of CO paralleled by an increase of the parasitic hydrogen evolution reaction.

One-Step Electrodeposition of Bimetallic Nanocatalyst Anchored on Nanomatrix for Nonenzymatic Sensing of Glucose

One-Step Electrodeposition of Bimetallic Nanocatalyst Anchored on Nanomatrix for Nonenzymatic Sensing of Glucose

One-pot synthesis of graphene hydrogel-anchored cobalt-copper nanoparticles and their catalysis in hydrogen generation from ammonia borane.

We reported a facile one-pot synthesis of bimetallic CoCu nanoparticles (NPs) anchored on graphene hydrogel (GH-CoCu) as catalysts in hydrogen generation from the hydrolysis of ammonia borane (HAB). The presented novel one-pot method composed of the reduction of the mixture of graphene oxide, cobalt(II), and copper(II) acetate tetrahydrates by aqueous ethylene glycol solution in a teflon-coated stainless-steel reactor at 180 °C. The structure of the yielded GH-CoCu nanocatalysts was characterized by TEM, SEM, XRD, XPS, and ICP-MS. This is the first example of both the synthesis of bimetallic CoCu NPs anchored on GH and the testing of a hydrothermally prepared noble metal-free GH-bimetallic nanocomposites as catalysts for the HAB. The presented in situ synthesis protocol allowed us to prepare different metal compositions and investigating their catalysis in the AB hydrolysis, where the best catalytic activity was accomplished by the GH-Co33Cu67 nanocatalysts. The obtained GH-CoCu nanocatalysts exhibited a remarkable catalytic performance in the HAB by providing the highest hydrogen generation rate of 1015.809 ml H2 gcatalyst-1 min-1 at room temperature. This study has a potential to pave a way for the development of other GH-based bimetallic nanocatalysts that could be used in different applications.

Direct design of cage-like bimetallic NiFe hydroxides with regulated electron structure to boost the kinetic activity of oxygen evolution reaction

The key to inhibiting agglomeration of bimetallic nanocatalysts and increasing their efficiency of oxygen evolution reaction (OER) highlights the necessity to design hollow porous structures in water electrolysis. Herein, the well-regulated NiFe bimetallic nanocages have been directly synthesized through the coordinated etching and precipitation (CEP) route, and then employed as advanced electrode materials in OER. Density functional theory (DFT) calculations disclosed that the synergistic effect between Fe and Ni significantly regulated the electron density and enhanced the conductivity. Significantly, the high catalytic activity of NiFe nanocages arises from the strong interactions between Fe and Ni along with rapid electron transfer, and the favorable structure with abundant porosity and large surface area. When employed as OER electrocatalysts, the electrode based on Ni2Fe1 nanocages exhibited a low overpotential of 280 mV at 10 mA·cm−2 combined with a low Tafel slop of 55.3 mV·dec−1 and large Cdl (double layers capacitance) value of 2.33 mF·cm−2. In summary, it is promising to directly design hollow porous structures based on bimetallic hydroxide to boost the OER performance.

Electrocatalytic oxidation of sorbitol on PdxAuy/C bimetallic nanocatalysts

In the present work, the sorbitol electro-oxidation reaction (SOR) was studied in alkaline medium employing bimetallic catalysts of palladium and gold (PdxAuy/C). The activity for SOR was mainly correlated to bimetallic interactions, because the catalysts presented similar characteristics like morphology, average particle sizes (∼10 nm), and metallic mass contents (∼20 wt%). The bimetallic interactions induced changes like shifts in the lattice parameters, as well in Pd binding energies (up to −0.25 eV) and into the reduction peak of Pd oxides during the electrochemical characterization. Pd40Au60/C and Pd60Au40/C presented the best activities at 3 M KOH achieving onset potentials of −0.43 V vs. NHE and current densities of 128 and 209 mA mg−1 at a fixed potential of 0.1 V, respectively. Pd60Au40/C presented almost 3.5-fold more current density than Pd/C, and 10-fold more than Au/C at the same conditions. These materials also displayed superior stability, maintaining their maximum current densities after 1000 cycles in 0.5 M sorbitol + 3 M KOH. The SOR by-products were determined by HPLC and GC/MS, revealing that these catalysts break sorbitol C–C bonds by attacking intermediate carbons (C3 and C4) and/or by subsequent removal of chain-end carbons. Among the detected by-products, value-added molecules like glycerol, ethylene glycol, formic acid, and γ-butyrolactone were found. In summary, the stability and activity of Pd-based materials make them suitable for the oxidation of sorbitol as a promising alcohol for fuel cell technology.

Conductive-polymer-supported palladium-iron bimetallic nanocatalyst for simultaneous 4-chlorophenol and Cr(VI) removal: Enhanced interfacial electron transfer and mechanism

Nanoscale zerovalent iron (nZVI) reduction offers a wide range of applications in source-zone remediation, but the reactivity of nZVI is largely hampered due to its low electron-transfer ability and tendency to aggregate. Based on the dual function of conductive polymers (CPs) as support and electron transfer carrier, we combined CPs with nZVI and prepared a series of Pd/Fe bimetallic materials that successfully address the challenges of nZVI reduction. These Pd/Fe@CPs particles showed strong catalytic ability for the simultaneous removal of 4-chlorophenol (4-CP) and Cr(VI). The removal rate of 4-CP was significantly enhanced by 1.5–6.2 times after supporting Pd/Fe nanoparticles (NPs) with CPs. The enhanced reactivity of supported Pd/Fe NPs was attributed to their highly stabilized and dispersed state and the promoted electron transfer due to the synergistic effect between CPs and nZVI bimetallic particles. The various catalytic activity over Pd/Fe@CPs was attributed to the distinctive properties of CPs and their different interfacial electron transfer ability. Importantly, this study provides insights into distinguishing both mechanisms of direct electron transfer and atomic-hydrogen-mediated indirect electron transfer, and their quantitative relationship to the dehalogenation performance over Pd/Fe@CPs materials. This work provides better understanding of the remediation process and mechanisms of nZVI reduction.

Recent Advances in Hydrogenation Reactions Using Bimetallic Nanocatalysts: A Review

AbstractHydrogenation reactions have been studied for many decades now and have developed from reactions that appear simple to now being recognized for their many complexities. These reactions are generally catalyzed using monometallic and more recently, with bimetallic nanocatalysts. Hydrogenation plays a vital role in food, chemical, petrochemical, pharmaceuticals, and dye industries to name a few. The hydrogenated products derived from several biomass‐based compounds are potential fossil fuels. Such products when employed in daily life, can help conserve natural resources. While hydrogenation of alkynes and alkenes are among the simplest of hydrogenation reactions, the most extensive and elegant manifestation of this reaction is seen in polymerization. Polymers like polythene, polypropylene (plastic) have replaced materials like glass, stainless steel, etc., in making daily use items for the obvious advantages of the former. Purification of alkenes is achieved by partially hydrogenating the respective alkynes present in trace amounts. This serves as an important step in the polymerization process. The presence of nitro group on aromatic rings makes them carcinogenic in nature which harms living organisms. For a safe environment, the elimination or modification of this nitro group becomes imperative. The products of hydrogenation of nitroaromatics and amino aromatics form the basis of pharmaceuticals and dyestuffs. A plethora of bimetallic catalysts have been used to catalyze these hydrogenation reactions. These catalysts are evaluated based on their selectivity and efficiency. This review highlights the recent advancements in the field of hydrogenation of nitro compounds, carbonyl compounds, and unsaturated hydrocarbons catalyzed by bimetallic nanoparticles.

Size effect of the carbon-supported bimetallic Fe-Co nanoparticles on the catalytic activity in the Fischer-Tropsch synthesis

Carbon-supported bimetallic Fe-Co nanocatalysts with different particle sizes have been synthesized by one-pot method involving simultaneous metal nanoparticles formation and chitosan carbonization. The Fe-Co particle size has been found to vary from 5 to 14 nm depending on the amount of metal loaded in the polymer precursor. For the first time, the size effect of Fe-Co alloy nanoparticles on the specific catalyst activity, yield and selectivity of the products of the Fischer-Tropsch synthesis has been studied. It has been revealed that smaller size of the Fe-Co nanoparticles allows to achieve the maximum selectivity towards C5+ hydrocarbons at lower reaction temperature. The catalyst with the Fe-Co average particle size of 10 nm has been demonstrated the highest specific activity (per unit mass) of 126 μmolCO/(gFe-Co·s). The structure of the Fe-Co bimetallic nanoparticles formed in the composites with different initial metal loading was studied and reviewed for details by XRD analysis.

Bi/Ti-phenolic network induced biomimetic synthesis of mesoporous hierarchical bimetallic hybrid nanocatalysts with enhanced visible-light photocatalytic performance

Biomass-templated biomimetic mineralization has recently emerged as a readily scalable method for the fabrication of mesoporous metal oxides due to the wide availability of the templates and their delicate hierarchical porous nanostructures. However, the selective ionic interactions of biomass-derived templates limit the possible chemical compositions of the desired products. Polyphenols can potentially introduce more general ionic adsorption to biomass-derived templates through the self-assembly of metal-phenolic networks (MPNs), leading to successful synthesis of a much broader range of mesoporous materials. As an illustration of this strategy, we designed a novel method for the fabrication of hierarchical mesoporous bimetallic hybrid nanocatalysts through calcination of biomass collagen-templated bimetallic MPNs. The resultant Bi/Ti bimetallic hybrid nanocatalysts inherited the hierarchical mesostructures of their collagen templates and showed excellent photocatalytic performance in the visible-light region (420−700 nm), which was consistent with the theoretical calculations using the first-principles density function theory. This simple and low-cost MPN-based approach possibly provides a universal platform for stable mineralization of biomass templates, paving the avenue towards a wide range of potential applications in environmental-friendly synthesis of mesoporous metal oxide materials.

Partially amorphous NiFe-based bimetallic hydroxide nanocatalyst for efficient oxygen evolution reaction

Partially amorphous NiFe-based bimetallic hydroxide nanocatalyst for efficient oxygen evolution reaction

Amine functional silica–supported bimetallic Cu-Ni nanocatalyst and investigation of some typical reductions of aromatic nitro-substituents

Amine functional silica–supported bimetallic Cu-Ni nanocatalyst and investigation of some typical reductions of aromatic nitro-substituents

Catalytic properties/performance evolution during sono-hydrothermal design of nanocrystalline ceria over zinc oxide for biofuel production

The main objective of this study was to produce biodiesel from waste oil by bifunctional acid-base CeO2(x%)/ZnO nanocatalysts. CeO2 was loaded over mesoporous ZnO in different percentages (X = 5, 10, 20, 30 and 50) to reach the optimum acid-base balance, and remove the internal mass transfer resistance. Ultrasonication was adopted as an efficient approach to synthesize the nanocatalysts with modified features. XRD, FESEM, TEM, EDX, BET-BJH, FTIR TPR-H2, and TPD-NH3 characterization analyses were carried out to identify the as-fabricated nanocatalysts. Bi-metallic nanocatalysts were tested in one-pot biodiesel production from a high free fatty acid containing model of waste oil. In each cycle, the conversion of esterification and transesterification reactions, as well as the overall conversion were estimated, and the superior activity was achieved over sonoassisted designed CeO2 = 20% nanocatalyst (FFA conversion = 80%, TG conversion = 97% and total conversion = 93%). According to the results of analyses, this outcome is depended on the uniform dispersion of active components, high SBET, and pore volume, as well as the suitable acid site density and strength. The promotion effect of ultrasonic waves on CeO2 dispersion not only increased the activity of nanocatalysts but also yielded satisfactory stability. Sono-designed sample with CeO2 = 20% exhibited the most stable nanocatalyst that maintained its performance after five cycles. Moreover, CeO2 = 20% showed high performance without deactivation in the presence of NaCl which is one of the impurity elements in waste cooking oil.

Copper/Nickel-Decorated Olive Pit Biochar: One Pot Solid State Synthesis for Environmental Remediation

Developing micro- and nanomaterials for environmental pollution remediation is currently a pertinent topic. Among the plethora of strategies, designing supported nanocatalysts for the degradation of pollutants has achieved prominence. In this context, we are addressing one of the UN Sustainable Development Goals by valorizing agrowaste as a source of biochar, which serves as a support for bimetallic nanocatalysts. Herein, olive pit powder particles were impregnated with copper and nickel nitrates and pyrolyzed at 400 °C. The resulting material consists of bimetallic CuNi-decorated biochar. CuNi nanocatalysts were found to be as small as 10 nm and very well dispersed over biochar with zero valent copper and nickel and the formation of copper–nickel solid solutions. The biochar@CuNi (B@CuNi) exhibited typical soft ferromagnet hysteresis loops with zero remanence and zero coercivity. The biochar@CuNi was found to be an efficient catalyst of the reduction in methyl orange (MO) dye, taken as a model pollutant. In sum, the one-pot method devised in this work provides unique CuNi-decorated biochar and broadens the horizons of the emerging topic of biochar-supported nanocatalysts.

Zirconia supported gold–palladium nanocatalyst for NAD(P)H regeneration via two-step mechanism

The regeneration cycle of expensive cofactor, NAD(P)H, is of paramount importance for the bio-catalyzed redox reactions. Here a ZrO2 supported bimetallic nanocatalyst of gold–palladium (Au–Pd/ZrO2) was prepared to catalyze the regeneration of NAD(P)H without using electron mediators and extra energy input. Over 98% of regeneration efficiency can be achieved catlyzed by Au–Pd/ZrO2 using TEOA as the electron donor. Mechanism study showed that the regeneration of NAD(P)H took place through a two-step process: Au–Pd/ZrO2 nanocatalyst first catalyzed the oxidation of triethanolamine (TEOA) to glycolaldehyde (GA), then the generated GA induced the non-catalytic reducing of NAD(P)+ to NAD(P)H under an alkaline environment maintained by TEOA. This two-step mechanism enables the decoupling of the regeneration of NAD(P)H in space and time into a catalytic oxidation and non-catalytic reducing cascade process which has been further verified using a variety of electron donors. The application significance of this procedure is further demonstrated both by the favorable stability of Au–Pd/ZrO2 nanocatalyst in 5 successive cycles preserving over 90% of its original activity, and by the excellent performance of the regenerated NADH as the cofactor in the catalytic hydrogenation of acetaldehyde using an ethanol dehydrogenase.

Batch Oxidative Desulfurization of Model Light Gasoil over a Bimetallic Nanocatalyst

AbstractA novel AgO/ZnO/HY‐zeolite bimetallic nanocatalyst was designed and synthesized by an impregnation method. The purpose of this nanocatalyst was to remove dibenzothiophene as the primary sulfur content from a model light gasoil in a catalytic oxidative desulfurization (ODS) process. The characteristics of the synthesized nanocatalyst were determined by Fourier transform IR spectroscopy, Brunauer‐Emmett‐Teller analysis, scanning electron microscopy, and X‐ray diffraction. The ODS study revealed high sulfur conversion under optimal ODS reaction conditions and very good reusability of the catalyst after recycling five times.

Construction of Lattice Strain in Bimetallic Nanostructures and Its Effectiveness in Electrochemical Applications.

Bimetallic nanocrystals (NCs), associated with various surface functions such as ligand effect, ensemble effect, and strain effect, exhibit superior electrocatalytic properties. The stress-induced surface strain effect can alter binding strength between the surface active sites and reactants as well as their intermediates, and the electrochemical performance of bimetallic NCs can be significantly facilitated by the lattice-strain modification via their morphologies, sizes, shell-thickness, surface defectiveness as well as compositions. In this review, an overview of fundamental principles, characterization techniques, and quantitative determination of the surface lattice strain is provided. Various strategies and synthesis efforts on creating lattice-strain-engineered bimetallic NCs, including the de-alloying process, atomic layer-by-layer deposition, thermal treatment evolution, one-pot synthesis, and other efforts are also discussed. It is further outlined how the lattice strain effect promotes electrochemical catalysis through the selected case studies. The reactions on oxygen reduction reaction, small molecular oxidation, water splitting reaction, and electrochemical carbon dioxide reduction reactions are focused. In particular, studies of lattice strain arisen from core-shell nanostructure and defectiveness are highlighted. Lastly, the potential challenges are summarized and the prospects of lattice-strain-based engineering on bimetallic nanocatalysts with suggestion and guidance of the future electrocatalyst design are envisioned.

Material characterization of Au/Ni nanocatalyst for low-temperature carbon dioxide methanation

The nanocatalyst for the carbon oxide methanation process is used, among others, in environmental protection, chemical industry, and renewable energy sources. The use of a suitable catalyst allows a chemical reaction to be carried out between unreacted gaseous substrates. The most frequently studied monometallic catalysts are: Ni, Ru, Rh, Pt, Au, Cu, Fe. Bimetallic nanocatalysts are equally popular. Their catalytic properties differ from those of pure component metals. Numerous studies indicate a positive effect in catalysts containing particles: Au-Ag, Au-Pt, Au-Pd, Pd-Ni, Pd-Cu. A review of the literature indicates that examples of the use of metal nanoparticles of spherical shape deposited on a nickel substrate in the methanation process are known, but so far no attempt has been shown in publications to produce a catalyst based on gold nanoparticles with developed surface in the form of spiky (nanourchins, nanostars) on a nickel base as presented in the article. Gold nanourchins are deposited on a nickel substrate in the form of a nickel molecular mesh. The prepared nanocatalyst has been subjected to structural analysis using a transmission electron microscope (TEM). Scanning Electron Microscopic (SEM) images were taken with a Zeiss Supra 35. Qualitative studies of chemical composition were also performed using the Energy Dispersive Spectrometer (EDS). Based on the TEM results, the appearance of the X-ray diffraction pattern was computer modelled. A nanocatalyst was obtained with a high coverage of the nickel molecular mesh surface with gold nanoparticles not exceeding 50 nm in diameter.

A bimetallic nanocatalyst for light-free oxygen sensitization therapy

Singlet oxygen (1O2) is extensively employed by reactive oxygen species (ROS)-based cancer therapies, such as photodynamic therapy (PDT) and chemodynamic therapy (CDT). However, the dependences of PDT on light and CDT on complex chemodynamic reactions greatly limit their 1O2-generating efficiencies. Here, we exploit strain and electronic effects to fabricate a bimetallic nanocatalyst by coating a gold nanorod (AuNR) with ~2 platinum (Pt) atomic layers (AuPt0.09), which efficiently generates 1O2 from ground-state oxygen (3O2) by electron-transfer-mediated spin reduction. Density functional theory reveals strain, and electronic effects promote the adsorption of 3O2 onto AuPt0.09, which dramatically enhances 1O2 generation and imparts AuPt0.09, the highest catalytic constant ever reported for 3,3′,5,5′-tetramethylbenzidine oxidation to the best of our knowledge. With a pH-dependent catalytic activity, AuPt0.09 realizes acidity-dependent antitumor effects both in vitro and in vivo, a proof-of-concept demonstration of autocatalytic bimetallic nanocatalyst for light-free oxygen sensitization therapy, which may open a new avenue for 1O2-centered therapeutics.