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Intermetallic nanoparticles (i‐NPs) have received considerable attention as high‐performance catalysts for diverse catalytic applications. However, high‐entropy i‐NPs have been rarely reported due to particle growth and phase separation in the multicomponent alloy. In this study, for the first time, an integrated approach of template and structure transformation is introduced to synthesize a series of sub ≈ 5 nm multicomponent i‐NPs with varying compositions. Firstly, ultrathin PtCu nanosheets (NSs) are directly converted into bimetallic PtCu i‐NPs. Furthermore, these PtCu NSs are also used as templates for epitaxial growth of the other metals, followed by annealing to obtain high‐loading, novel compositions and uniform i‐NPs with ternary, quaternary, and quinary compositions, including high‐entropy i‐NPs. Interestingly, L10 intermetallic phases are obtained when Fe is introduced. As a proof‐of‐concept application, these high‐entropy i‐NPs showed superior catalytic performance for the hydrogen evolution reaction , which can be attributed to the negatively shifted d‐band center of Pt, thereby resulting in reduced H* adsorption energy at Pt sites as supported by density functional theory calculations. Overall, this research presents a promising method for the development of i‐NPs with various compositions. [ABSTRACT FROM AUTHOR]

Synthesizing intermetallic phases containing noble metals often poses a challenge as the melting points of noble metals often exceed the boiling point of bismuth (1560 °C). Reactions in the solid state generally circumvent this issue but are extremely time consuming. A convenient method to overcome these obstacles is the co‐reduction of metal salts in polyols, which can be performed within hours at moderate temperatures and even allows access to metastable phases. However, little attention has been paid to the formation mechanisms of intermetallic particles in polyol reductions. Identifying crucial reaction parameters and finding patterns are key factors to enable targeted syntheses and product design. Here, we chose metastable γ‐BiPd as an example to investigate the formation mechanism from mixtures of metal salts in ethylene glycol and to determine critical factors for phase formation. The reaction was also monitored by in situ X‐ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by (in situ) X‐ray diffraction, electron microscopy, and UV‐Vis spectroscopy. In the first step of the reaction, elemental palladium precipitates. Increasing temperature induces the reduction of bismuth cations and the subsequent rapid incorporation of bismuth into the palladium cores, yielding the γ‐BiPd phase. [ABSTRACT FROM AUTHOR]

Intermetallic nanoparticles (i‐NPs) have received considerable attention as high‐performance catalysts for diverse catalytic applications. However, high‐entropy i‐NPs have been rarely reported due to particle growth and phase separation in the multicomponent alloy. In this study, for the first time, an integrated approach of template and structure transformation is introduced to synthesize a series of sub ≈ 5 nm multicomponent i‐NPs with varying compositions. Firstly, ultrathin PtCu nanosheets (NSs) are directly converted into bimetallic PtCu i‐NPs. Furthermore, these PtCu NSs are also used as templates for epitaxial growth of the other metals, followed by annealing to obtain high‐loading, novel compositions and uniform i‐NPs with ternary, quaternary, and quinary compositions, including high‐entropy i‐NPs. Interestingly, L10 intermetallic phases are obtained when Fe is introduced. As a proof‐of‐concept application, these high‐entropy i‐NPs showed superior catalytic performance for the hydrogen evolution reaction , which can be attributed to the negatively shifted d‐band center of Pt, thereby resulting in reduced H* adsorption energy at Pt sites as supported by density functional theory calculations. Overall, this research presents a promising method for the development of i‐NPs with various compositions.

Abstract Synthesizing intermetallic phases containing noble metals often poses a challenge as the melting points of noble metals often exceed the boiling point of bismuth (1560 °C). Reactions in the solid state generally circumvent this issue but are extremely time consuming. A convenient method to overcome these obstacles is the co‐reduction of metal salts in polyols, which can be performed within hours at moderate temperatures and even allows access to metastable phases. However, little attention has been paid to the formation mechanisms of intermetallic particles in polyol reductions. Identifying crucial reaction parameters and finding patterns are key factors to enable targeted syntheses and product design. Here, we chose metastable γ‐BiPd as an example to investigate the formation mechanism from mixtures of metal salts in ethylene glycol and to determine critical factors for phase formation. The reaction was also monitored by in situ X‐ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by (in situ) X‐ray diffraction, electron microscopy, and UV‐Vis spectroscopy. In the first step of the reaction, elemental palladium precipitates. Increasing temperature induces the reduction of bismuth cations and the subsequent rapid incorporation of bismuth into the palladium cores, yielding the γ‐BiPd phase.

Intermetallic nanoparticles (NPs) have shown enhanced catalytic properties as compared to their disordered alloy counterparts. To advance their use in green energy, it is crucial to understand what controls the formation of intermetallic NPs over alloy structures. By carefully selecting the additives used in NP synthesis, it is here shown that monodisperse, intermetallic PdCu NPs can be synthesized in a controllable manner. Introducing the additives iron(III) chloride and ascorbic acid, both morphological and structural control can be achieved. Combined, these additives provide a synergetic effect resulting in precursor reduction and defect‐free growth; ultimately leading to monodisperse, single‐crystalline, intermetallic PdCu NPs. Using in situ X‐ray total scattering, a hitherto unknown transformation pathway is reported that diverges from the commonly reported coreduction disorder–order transformation. A Cu‐rich structure initially forms, which upon the incorporation of Pd(0) and atomic ordering forms intermetallic PdCu NPs. These findings underpin that formation of stoichiometric intermetallic NPs is not limited by standard reduction potential matching and coreduction mechanisms, but is instead driven by changes in the local chemistry. Ultimately, using the local chemistry as a handle to tune the NP structure might open new opportunities to expand the library of intermetallic NPs by exploiting synthesis by design. [ABSTRACT FROM AUTHOR]

We report a general concurrent template strategy for precise synthesis of mesoporous Pt‐/Pd‐based intermetallic nanoparticles with desired morphology and ordered mesostructure. The concurrent template not only supplies a mesoporous metal seed for re‐crystallization growth of atomically ordered intermetallic phases with unique atomic stoichiometry but also provides a nanoconfinement environment for nanocasting synthesis of mesoporous nanoparticles with ordered mesostructure and rhombic dodecahedral morphology under elevated temperature. Using the selective hydrogenation of 3‐nitrophenylacetylene as a proof‐of‐concept catalytic reaction, mesoporous intermetallic PtSn nanoparticles exhibited remarkably controllable intermetallic phase‐dependent catalytic selectivity and excellent catalytic stability. This work provides a very powerful strategy for precise preparation of ordered mesoporous intermetallic nanocrystals for application in selective catalysis and fuel cell electrocatalysis. [ABSTRACT FROM AUTHOR]

The rational design and facile synthesis of highly activated and stable electrocatalysts toward the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR) are extremely demanded but remain challenging. Herein, a highly efficient bifunctional electrocatalyst composed of rhodium (Rh), cobalt (Co), and iron (Fe) alloy nanoparticles embedded in nitrogen-doped graphene (RhFeCo@NG) is prepared through sequential annealing and the substitution reaction. The as-prepared Rh2.6Fe3Co2.6@NG electrocatalyst achieves an overpotential as low as 25 mV for reaching a current density of 10 mA cm–2 and an ultralow Tafel slope of 29.8 mV dec–1 in 1 M KOH solution for HER, which is even superior to the state-of-the-art platinum (Pt) catalyst. With regard to ORR, for the Rh2.6Fe3Co2.6@NG electrocatalyst, a half-wave potential (E1/2) of 0.82 V versus reversible hydrogen electrode and excellent long-term stability are achieved. The experimental results illustrate that alloying the Rh atom with the FeCo nanoalloy is mainly responsible for the excellent HER and ORR performances. This study not only provides a robust and promising electrocatalyst for HER and ORR in alkaline media but also sheds light on the devising of efficient and multifunctional catalysts. [ABSTRACT FROM AUTHOR]

In alloyed nanoparticles, synergistic electronic and/or geometric effects may enhance the catalytic properties compared to their monometallic counterparts. Herein, we address the synthesis of bimetallic Au/Cu nanoparticles with different compositions by wet chemical reduction in ionic liquids. The nanoparticles were successively supported on carbon. The ionic liquid could be recycled after synthesis. Annealing of the carbon‐supported NPs at 400 °C led to NPs of the ordered intermetallic L10 AuCu phase. The nanoparticle‐derived catalysts were characterized by X‐ray diffraction analysis, transmission electron microscopy, X‐ray photoelectron spectroscopy and optical emission spectroscopy with inductively coupled plasma. Oxidation of biomass‐derived furans is a prominent process for biomass transformation into value‐added chemicals. Herein, the oxidation of 5‐hydroxymethyl‐2‐furfural (HMF) to 2,5‐furandicarboxylic acid (FDCA) was chosen as a model reaction to evaluate the effect of Cu addition and intermetallic structure on the catalytic performance. Particularly Au/Cu nanoparticles with an Au/Cu ratio of 3 : 1 showed very high conversion to FDCA. [ABSTRACT FROM AUTHOR]

The structure of monometallic decahedral multiply twinned nanoparticles (MTPs) has been extensively studied, whereas less is known about intermetallic MTPs, especially the mechanism of formation of multiply twinned structures, which remains to be understood. Here, by using aberration-corrected scanning transmission electron microscopy, a detailed structural study of AuCu decahedral intermetallic MTPs is presented. Surface segregation has been revealed on the atomic level and the multiply twinned structure was studied systematically. Significantly different from Au and Cu, the intermetallic AuCu MTP adopts a solid-angle deficiency of −13.35°, which represents an overlap instead of a gap (+7.35° gap for Au and Cu). By analysing and summarizing the differences and similarities among AuCu and other existing monometallic/intermetallic MTPs, the formation mechanism has been investigated from both energetic and geometric perspectives. Finally, a general framework for decahedral MTPs has been proposed and unknown MTPs could be predicted on this basis.

Developing a highly active, durable, and low-platinum-based electrocatalyst for the cathodic oxygen reduction reaction (ORR) is for breaking the bottleneck of large-scale applications of proton exchange membrane fuel cells (PEMFCs). Herein, ultrafine PtZn intermetallic nanoparticles with low Pt-loading and trace germanium (Ge) involvement confined in the nitrogen-doped porous carbon (Ge-L 10 -PtZn@N-C) are reported. The Ge-L 10 -PtZn@N-C exhibit superior ORR activity with a mass activity of 3.04 A mg -1 Pt and specific activity of 4.69 mA cm -2 , ≈12.2- and 10.2-times improvement compared to the commercial Pt/C (20%) at 0.90 V in 0.1 m KOH. The cathodic catalyst Ge-L 10 -PtZn@N-C assembled in the PEMFC shows encouraging peak power densities of 316.5 (at 0.86 V) and 417.2 mW cm -2 (at 0.91 V) in alkaline and acidic fuel-cell, respectively. The combination of experiment and density functional theory calculations (DFT) results robustly reveal that the participation of trace Ge can not only trigger a "growth site locking effect" to effectively inhibit nanoparticle growth, bring miniature nanoparticles, enhance dispersion uniformity, and achieve the exposure of the more electrochemical active site, but also effectively modulates the electronic structure, hence optimizing the adsorption/desorption of the oxygen intermediates., (© 2023 Wiley‐VCH GmbH.)

Multimetallic nanoparticles (NPs) often exhibit enhanced catalytic properties that differ from their parent materials. Carefully exploring the structures of multimetallic NPs is a prerequisite for understanding the structure‐ and composition‐associated properties. Herein, intermetallic Pt/Sn NPs with tunable compositions are designed exploiting the beneficial properties of ionic liquids (ILs) in a one‐pot synthetic procedure. Metal salt precursors are reduced with triethylhydridoborate, whereby the cation of the triethylhydridoborate is adapted to the cation of the IL. Both the initial metal precursor ratio and the type of IL influence the structure of the NPs, with the effect of the IL being more pronounced. PtSn nanocrystals are obtained as phase pure products under optimized reaction conditions, whereby a microwave‐assisted approach leads to higher crystallinity. In the hydrogenation of α,β‐unsaturated aldehydes, the catalytic performance obviously depend on the NP composition. In bimetallic Pt/Sn NPs, higher Pt content leads to increased conversion, while increase in Sn increases selectivity to the cinnamic alcohol. [ABSTRACT FROM AUTHOR]

Controllable synthesis of atomically ordered intermetallic nanoparticles (NPs) is crucial to obtain superior electrocatalytic performance for fuel cell reactions, but still remains arduous. Herein, we demonstrate a novel and general hydrogel‐freeze drying strategy for the synthesis of reduced graphene oxide (rGO) supported Pt3M (M=Mn, Cr, Fe, Co, etc.) intermetallic NPs (Pt3M/rGO‐HF) with ultrasmall particle size (about 3 nm) and dramatic monodispersity. The formation of hydrogel prevents the aggregation of graphene oxide and significantly promotes their excellent dispersion, while a freeze‐drying can retain the hydrogel derived three‐dimensionally (3D) porous structure and immobilize the metal precursors with defined atomic ratio on GO support during solvent sublimation, which is not afforded by traditional oven drying. The subsequent annealing process produces rGO supported ultrasmall ordered Pt3M intermetallic NPs (≈3 nm) due to confinement effect of 3D porous structure. Such Pt3M intermetallic NPs exhibit the smallest particle size among the reported ordered Pt‐based intermetallic catalysts. A detailed study of the synthesis of ordered intermetallic Pt3Mn/rGO catalyst is provided as an example of a generally applicable method. This study provides an economical and scalable route for the controlled synthesis of Pt‐based intermetallic catalysts, which can pave a way for the commercialization of fuel cell technologies. [ABSTRACT FROM AUTHOR]

The high cost and poor durability of Pt nanoparticles (NPs) have always been great challenges to the commercialization of proton exchange membrane fuel cells (PEMFCs). Pt-based intermetallic NPs with a highly ordered structure are considered as promising catalysts for PEMFCs due to their high catalytic activity and stability. Here, we reported a facile method to synthesize N-doped carbon encapsulated PtZn intermetallic (PtZn@NC) NPs via the pyrolysis of Pt@Zn-based zeolitic imidazolate framework-8 (Pt@ZIF-8) composites. The catalyst obtained at 800 °C (10%-PtZn@NC-800) was found to exhibit a half-wave potential (E1/2) up to 0.912 V versus reversible hydrogen electrode (RHE) for the cathodic oxygen reduction reaction in an acidic medium, which shifted by 26 mV positively compared to the benchmark Pt/C catalyst. Besides, the mass activity and specific activity of 10%-PtZn@NC-800 at 0.9 V versus RHE were nearly 3 and 5 times as great as that of commercial Pt/C, respectively. It is worth noting that the PtZn@NC showed excellent stability in ORR with just 1 mV of the E1/2 loss after 5,000 cycles, which is superior to that of most reported PtM catalysts (especially those disordered solid solutions). Furthermore, such N-doped carbon shell encapsulated PtZn intermetallic NPs showed significantly enhanced performances towards the anodic oxidation reaction of organic small molecules (such as methanol and formic acid). The synergistic effects of the N doped carbon encapsulation structure and intermetallic NPs are responsible for outstanding performances of the catalysts. This work provides us a new engineering strategy to acquire highly active and stable multifunctional catalysts for PEMFCs. [ABSTRACT FROM AUTHOR]

• AuCu alloy and intermetallic nanoparticles were synthesized in solution phase. • Temperatures used for alloy and intermetallic nanoparticles were 180 °C and 300 °C. • Au-Cu intermetallic structures are determined by nano-beam electron diffraction. • AuCu intermetallic nanoparticles displayed better SERS response compared to alloy. Intermetallic phases in Au-Cu nanoparticles has been synthesized chemically in liquid phase. The heat-treatment of these nanoparticles at 180 °C for 1 h in solution phase led to the formation of Au-Cu alloy nanoparticles with nearly spherical shapes and monodispersed size of ∼10 nm. Subsequent heat-treatment at 300 °C for 30 min of these Au-Cu alloy nanoparticles not only revealed structural transformation to intermetallic phases (tetragonal AuCu (tP4) and cubic Cu 3 Au (cP4)) but also shape change occurs from spherical to rods having average aspect ratio ∼3.0. The structural determination at the particle has been carried out through nano-beam electron diffraction coupled with simulation of electron diffraction patterns and high resolution phase contrast images. These Au–Cu intermetallic nanoparticles exhibit an excellent surface enhanced Raman spectroscopic activity with methylene blue compared to that of Au-Cu alloy nanoparticles. [ABSTRACT FROM AUTHOR]

Nanopowders of Co-Ni particles (Co:Ni = 50:50, 80:20, and 20:80), Co-Sn particles (Co:Sn = 35:65 and 60:40), and Ni-Sn particles (Ni:Sn = 45:55) are synthesized through a borohydride reduction in a mixture of aqueous solutions of the corresponding metal salts. Additionally carbon nanocomposites are obtained in situ by a template synthesis using a graphite (CF) support including in the presence of ß-cyclodextrin (ß-CDx). The magnetic behavior of the synthesized intermetallic nanoparticles and their carbon composites is studied by a Vibrating Sample Magnetometer (VSM) at room temperature. The hysteresis loops of the synthesized intermetallic nanoparticles with a different elemental composition and their carbon composites are taken up to the maximum magnetic field of 6 kOe. The maximum magnetization varying from 27 to 2.5 emu/g and coercivity of 82 to 20 Oe were measured. The samples showing a relatively high maximum magnetization are the Co-Ni particles synthesized at a ratio of Co:Ni = 80:20 and Co:Ni = 50:50. The maximum magnetization of the Co-Ni particles is higher than that of Co-Sn nanoparticles. The samples of Co-Sn particles (Co:Sn = 35:65) have very low maximum magnetization but rather high coercivity. The samples of Ni-Sn nanoparticles (Ni:Sn = 45:55) are nonmagnetic. The carbon nanocomposites are characterized by significantly lower magnetic parameters than those of the aforementioned nanoparticles. The morphology and the elemental composition studied by SEM and EDS analyses explain this magnetic behavior. The maximum magnetization increases with the increase of Co content in Co-Ni and Co-Sn nanoparticles. When CF carrier is used, the measured maximum magnetization is significantly lower than that in the case when no carrier is used. This decrease in the magnetic properties of the composites could be due to the impurities of CoO and NiO oxides, as well as to the carbon from the CF support used during the particle's template synthesis. Co-Ni nanoparticles (Co Ni=80:20 and Co:Ni = 50:50) shown soft ferromagnetic behavior. Their magnetic properties are appropriate for bio-medical applications such as diagnostic tools and drug delivery for cancer treatment and other diseases. [ABSTRACT FROM AUTHOR]

The increasing interest in nanoscale materials goes hand in hand with the challenge to reliably characterize the chemical compositions and structural features of nanosized objects in order to relate those to their physical properties. Despite efforts, the analysis of the chemical composition of individual multi-element nanoparticles remains challenging-from the technical point of view as well as from the point of view of measurement statistics. Here, we demonstrate that zero-field solid-state nuclear magnetic resonance (NMR) complements local, single particle transmission electron microscopy (TEM) studies with information on a large assembly of chemically complex nanoparticles. The combination of both experimental techniques gives information on the local composition and structure and provides an excellent measurement statistic through the corresponding NMR ensemble measurement. This analytical approach is applicable to many kinds of magnetic materials and therefore may prove very versatile in the future research of particulate magnetic nanomaterials. [ABSTRACT FROM AUTHOR]

Intermetallic Co-Sn and Ni-Sn nanoparticles were synthesized by a template technique with a support, through a borohydride reduction method in a mixture of aqueous solutions respectively of CoCl2.6H2O, NiCl2.6H2O and SnCl2.2H2O at a pre-set ratio of Co:Sn, respectively Ni:Sn, at room temperatute and atmospheric pressure. Fluorinated graphite (CF) was used as the template and sodium borohydride as the reducing agent. In order to from uniform and finely monodispersed nanocrystals, β-cyclodextrine(β-CDx) was employed as a capping agent and citric acid(C6H8O7), as a stabilizing ligand. The morphology, structure, elemental and phase compositions of the obtained carbon-based nanocomposite materials with Co-Sn and Ni-Sn nanoparticles, were investigated with scanning and transmission electron microscopy (SEM/TEM), energy dispersive analysis (EDS) and X-ray diffraction analysis (XRD). The nanocomposites were characterized before and after being electrochemically tested as electrodes in a Li-ion battery through a cycling voltammetry. After the electrochemical tests the samples remained homogeneous and compact, and no cracking was observed. This shows that during the processes of charge/discharge the tested samples keep their mechanical stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • PtCo IMNs were uniformly encaged within the mesopores of Cr-BDC MOFs for selective hydrogenation of 4-nitrophenole. • The PtCo/Cr-BDC catalyst exhibit superior selective hydrogenation performances than that of Pt/Cr-BDC and Co/Cr-BDC catalysts. • The exceptional activity was ascribed to mesoporous structure and synergistic interaction between Co and Pt in PtCo/Cr-BDC catalyst. • The mesoporous PtCo/Cr-BDC catalyst revealed remarkable durability. Engineering of economical and stabilized precious metal based catalysts are crucial in recent ages to achieve the desirable catalytic performance as they tend to destabilize easily. Herein, Cr-BDC MOF was prepared that provides high surface area and pore volumes to evenly distribute, host, and stabilize the Pt and Co intermetallic nanoparticles (IMNs). Among these, the PtCo/Cr-BDC catalyst showed superior selective hydrogenation activity for 4-Nitrophenol (4-NP) to 4-Aminophenol (4-AP) as an exemplary reaction. A number of characterization techniques were carried out to study the influence of the Cr-BDC support and Co metal on the surface and bulk structural properties of active Pt metal species. The Cr-BDC support imparts uniform distributions while the Co metal species influenced the catalytic activity. The maximum conversion (99.3 %) of 4-NP to 4-AP was observed with PtCo/Cr-BDC in 2 min at a reaction rate constant (k) of 1.27 min−1 at room temperature, which is superior than Pt/Cr-BDC (0.64 min−1) and Co/Cr-BDC (0.14 min−1). The superior hydrogenation activity was credited to the addition of electropositive Co species to Pt/Cr-BDC catalyst that synergistically interacts with active Pt species within the pores of Cr-BDC MOFs and making PtCo IMNs system. As a result of this synergistic interaction, new additional interfacial electrophilic and nucleophilic metallic sites are generated within the pores of MOFs, which enormously encourage the selective hydrogenation of lethal 4-NP to valued 4-AP. Besides, the PtCo/Cr-BDC catalysts revealed remarkable durability up to several repeated rounds, validating its real-world applicability. [ABSTRACT FROM AUTHOR]

Formation of PdIn intermetallic nanoparticles supported on α-Al2O3 was investigated by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and hydrogen temperature-programmed desorption (H2-TPD) methods. The metals were loaded as heterobimetallic Pd(μ-O2CMe)4In(O2CMe) complex to ensure intimate contact between Pd and In. Reduction in H2 at 200 °C resulted in Pd-rich PdIn alloy as evidenced by XRD and the disappearance of Pd hydride. A minor amount of Pd1In1 intermetallic phase appeared after reduction at 200 °C and its formation was accomplished at 400 °C. Neither monometallic Pd or in nor other intermetallic structures were found after reduction at 400–600 °C. Catalytic performance of Pd1In1/α-Al2O3 was studied in the selective liquid-phase diphenylacetylene (DPA) hydrogenation. It was found that the reaction rate of undesired alkene hydrogenation is strongly reduced on Pd1In1 nanoparticles enabling effective kinetic control of the hydrogenation, and the catalyst demonstrated excellent selectivity to alkene.

A facile method to prepare Pt–Ti intermetallic nanoparticles supported on carbon was developed. Starting from a commercial Pt/C catalyst, TiO 2 layers were formed on the Pt/C then thermal annealing under a reducing condition successfully produced intermetallic Pt–Ti nanoparticles with an average size of 4.2 nm. The intermetallic Pt–Ti/C showed enhanced activity and durability for oxygen reduction reaction due to the change in electronic structure and less aggregation. [ABSTRACT FROM AUTHOR]

Abstract: In this work CuInSe2 (CISe) thin films were fabricated by rapid thermal processing of printed CuIn nanoparticles and thermally evaporated selenium as precursor layer. Research is focused on real-time investigations such as in-situ X-ray diffraction and dynamic scanning calorimetry. These measurements show CISe formation starting at 300°C. Significant amount of intermediate phases as reported for state-of-the-art rapid thermal processing of stacked elemental layer was not observed. The morphology of the nanoparticulate layers was examined by field emission scanning electron microscopy. Grain size developed from nanosized binary CuIn nanoparticles to microsized CISe grains. Porosity decreases in the temperature range from 340°C to 540°C. [Copyright &y& Elsevier]

Controllable synthesis of atomically ordered intermetallic nanoparticles (NPs) is crucial to obtain superior electrocatalytic performance for fuel cell reactions, but still remains arduous. Herein, we demonstrate a novel and general hydrogel-freeze drying strategy for the synthesis of reduced graphene oxide (rGO) supported Pt 3 M (M=Mn, Cr, Fe, Co, etc.) intermetallic NPs (Pt 3 M/rGO-HF) with ultrasmall particle size (about 3 nm) and dramatic monodispersity. The formation of hydrogel prevents the aggregation of graphene oxide and significantly promotes their excellent dispersion, while a freeze-drying can retain the hydrogel derived three-dimensionally (3D) porous structure and immobilize the metal precursors with defined atomic ratio on GO support during solvent sublimation, which is not afforded by traditional oven drying. The subsequent annealing process produces rGO supported ultrasmall ordered Pt 3 M intermetallic NPs (≈3 nm) due to confinement effect of 3D porous structure. Such Pt 3 M intermetallic NPs exhibit the smallest particle size among the reported ordered Pt-based intermetallic catalysts. A detailed study of the synthesis of ordered intermetallic Pt 3 Mn/rGO catalyst is provided as an example of a generally applicable method. This study provides an economical and scalable route for the controlled synthesis of Pt-based intermetallic catalysts, which can pave a way for the commercialization of fuel cell technologies., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The structure of monometallic decahedral multiply twinned nanoparticles (MTPs) has been extensively studied, whereas less is known about intermetallic MTPs, especially the mechanism of formation of multiply twinned structures, which remains to be understood. Here, by using aberration-corrected scanning transmission electron microscopy, a detailed structural study of AuCu decahedral intermetallic MTPs is presented. Surface segregation has been revealed on the atomic level and the multiply twinned structure was studied systematically. Significantly different from Au and Cu, the intermetallic AuCu MTP adopts a solid-angle deficiency of -13.35°, which represents an overlap instead of a gap (+7.35° gap for Au and Cu). By analysing and summarizing the differences and similarities among AuCu and other existing monometallic/intermetallic MTPs, the formation mechanism has been investigated from both energetic and geometric perspectives. Finally, a general framework for decahedral MTPs has been proposed and unknown MTPs could be predicted on this basis.

Formation of PdIn intermetallic nanoparticles supported on α-Al2O3 was investigated by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and hydrogen temperature-programmed desorption (H2-TPD) methods. The metals were loaded as heterobimetallic Pd(μ-O2CMe)4In(O2CMe) complex to ensure intimate contact between Pd and In. Reduction in H2 at 200 °C resulted in Pd-rich PdIn alloy as evidenced by XRD and the disappearance of Pd hydride. A minor amount of Pd1In1 intermetallic phase appeared after reduction at 200 °C and its formation was accomplished at 400 °C. Neither monometallic Pd or in nor other intermetallic structures were found after reduction at 400–600 °C. Catalytic performance of Pd1In1/α-Al2O3 was studied in the selective liquid-phase diphenylacetylene (DPA) hydrogenation. It was found that the reaction rate of undesired alkene hydrogenation is strongly reduced on Pd1In1 nanoparticles enabling effective kinetic control of the hydrogenation, and the catalyst demonstrated excellent selectivity to alkene. [ABSTRACT FROM AUTHOR]