Intermetallic Compound Nanoparticles Research Articles

Rhombohedral platinum-copper intermetallic compound: A high phosphate tolerance electrocatalyst for HT-PEMFC

In high-temperature proton exchange membrane fuel cells (HT-PEMFC), phosphate anions act as a poisonous 'spectator species', binding strongly to the Pt surface through PtO bonds similarly to O2. This blocks the Pt active sites, resulting in slow ORR kinetics. Herein, we synthesized ultrafine L11-PtCu intermetallic compound nanoparticles (O-PtCu/S-C) loaded on an S-doped carbon support with an average size of about 3 nm through wet impregnation followed by hydrogen annealing, which showed high resistance to phosphate poisoning. The introduction of S notably improved the metal-support interaction and prevented particle growth during annealing, which is beneficial for the uniform distribution of nanoparticles and prevents detachment and agglomeration during ADT. The pronounced Cu-Pt electronic interaction in O-PtCu/S-C induced electron transfer from Cu to Pt, which effectively modified the electronic structure of Pt and weakened the adsorption energy of phosphate anions on the catalyst surface. In addition, the phosphate poisoning test results from both room temperature RDE and high-temperature RDE demonstrate that O-PtCu/S-C possesses excellent phosphate tolerance, superior ORR activity, and remarkable stability. It exhibits a superior peak power density of 800.5 mW cm−2 in 160°C H2-O2 HT-PEMFC with Pt loading of 0.5 mg cm−2. This research offers a novel approach to designing phosphate-resistant electrocatalysts for HT-PEMFC.

Promoting ordering degree of intermetallic fuel cell catalysts by low-melting-point metal doping

Carbon supported intermetallic compound nanoparticles with high activity and stability are promising cathodic catalysts for oxygen reduction reaction in proton-exchange-membrane fuel cells. However, the synthesis of intermetallic catalysts suffers from large diffusion barrier for atom ordering, resulting in low ordering degree and limited performance. We demonstrate a low-melting-point metal doping strategy for the synthesis of highly ordered L10-type M-doped PtCo (M = Ga, Pb, Sb, Cu) intermetallic catalysts. We find that the ordering degree of the M-doped PtCo catalysts increases with the decrease of melting point of M. Theoretic studies reveal that the low-melting-point metal doping can decrease the energy barrier for atom diffusion. The prepared highly ordered Ga-doped PtCo catalyst exhibits a large mass activity of 1.07 A mgPt−1 at 0.9 V in H2-O2 fuel cells and a rated power density of 1.05 W cm−2 in H2-air fuel cells, with a Pt loading of 0.075 mgPt cm−2.

Thermal stability and oxidation resistance of non-equimolar ratio AlTiVCrNb refractory high-entropy alloys

In this work, we investigated the thermal stability, oxidation resistance and high temperature mechanical properties of refractory high entropy alloys Ti75Al10V5Cr5Nb5, Ti67Al12V7Cr7Nb7 and Ti55Al15V10Cr10Nb10(at.%). It is found that the second phase would be precipitated and occurs order-disorder transformation in refractory high entropy alloys at high temperature. The HCP phase produced orderly B2 phase and decreased the orderly B2 phase precipitation with the increasement of temperature in Ti67Al12V7Cr7Nb7 and Ti55Al15V10Cr10Nb10. According to the oxidation kinetics of high entropy alloys after 100h oxidation at 800 °C, the oxidation index factor n is between 1.1 and 1.2 and the degree of oxidation is between oxidized and inoxidized, all three refractory high entropy alloys formed oxides with rutile structure, the Ti67Al12V7Cr7Nb7 being less oxidation resistant due to the generation of Nb2O5 which is less stable at high temperature. Ti67Al12V7Cr7Nb7 has a yield strength of 522 MPa with 50% elongation at 650 °C. Ti75Al10V5Cr5Nb5 and Ti67Al12V7Cr7Nb7 have lower strength but 150% deformation without fracture when stretched at 750 °C. The multi-component intermetallic compound nanoparticles formed by the second phase and ordered phase together in the refractory high entropy alloys have an Orowan strengthening effect, to improve the mechanical properties at high temperature since it effectively prevents dislocation movement and stores dislocations.

Fundamental understanding of the synthesis of well-defined supported non-noble metal intermetallic compound nanoparticles

Fundamental insights into the synthesis of model-like, supported, non-noble metal intermetallic compound nanoparticle catalysts with phase pure bulk and bulk-like 1st-atomic-layer particle surface composition.

Synthesis of Carbon-Supported Intermetallic Pt5Ce Compound Nanoparticles via a Water-Based Impregnation Route

Synthesis of Carbon-Supported Intermetallic Pt₅Ce Compound Nanoparticles via a Water-Based Impregnation Route

PtZn Intermetallic Compound Nanoparticles in Mesoporous Zeolite Exhibiting High Catalyst Durability for Propane Dehydrogenation

A PtZn alloy nanoparticle catalyst for propane dehydrogenation was synthesized by simple coimpregnation of Pt(NH3)4(NO3)2 with Zn(NO3)2 onto a mesoporous material, which was built with siliceous MF...

Preparation and sintering properties of Cu10Sn3 IMCs nanopaste as die attach material for high temperature power electronics

Cu10Sn3 intermetallic compound (IMC) nanoparticles (NPs) were synthesized by one-step thermal decomposition method with low cost. The in-situ formed metal amide in the presence of LiN(iPr)2 can be reduced and thermally decomposed into metal NPs, and then the Cu10Sn3 NPs were obtained, which have an average diameter of 65 nm and good oxidation resistance. The microstructures and mechanical properties of Cu/Cu10Sn3/Cu joints at different sintering temperatures were investigated. The full-Cu10Sn3 IMC joints show high shear strength of 26.8 MPa after sintering at 300 °C for 20 min, demonstrating its broad potential as an interconnect material for high-temperature power electronics.

Nitrogen-doped Pt3Co intermetallic compound nanoparticles: A durable oxygen reduction electrocatalyst

Pt-based ordered alloy catalysts have been extensively investigated to improve the catalytic performance for proton exchange membrane fuel cells. Herein, we report N-doped ordered Pt3Co nanoparticles supported on XC-72R carbon (O-Pt3CoN/C) for oxygen reduction reaction (ORR). Both the X-ray photoelectron spectroscopy and the energy-dispersive X-ray spectroscopy elemental mapping analyses confirm the successful N-doping within the Pt3Co intermetallic compound. Consequently, the N-doped catalyst exhibits a significantly higher ORR performance in comparison with Pt3Co and commercial Pt/C catalysts. Importantly, the ORR mass activity of N-doped Pt3Co intermetallic compound is almost 2.4 times of that obtained on commercial Pt/C. Moreover, after accelerated durability test over the potential range of 0.6 to 1.1 V (vs. RHE), ORR activity decay of N-doped Pt3Co/C is only 21.5%, lower than those of ordered Pt3Co and commercial Pt/C catalysts. Thus, N-doping could be utilized as an effective strategy for further improving the ORR performance of Pt-M/C catalysts.

FeNi intermetallic compound nanoparticles wrapped with N-doped graphitized carbon: a novel cocatalyst for boosting photocatalytic hydrogen evolution

FeNi intermetallic compound nanoparticles wrapped by N-doped graphitized carbon is used as a novel cocatalyst for boosting photocatalytic hydrogen evolution performance of g-C3N4.

In Situ Formed Pt3Ti Nanoparticles on a Two-Dimensional Transition Metal Carbide (MXene) Used as Efficient Catalysts for Hydrogen Evolution Reactions

The design of efficient catalysts capable of delivering high currents at low overpotentials for hydrogen evolution reactions (HERs) is urgently needed to use catalysts in practical applications. Herein, we report platinum (Pt) alloyed with titanium (Ti) from the surface of Ti3C2Tx MXenes to form Pt3Ti intermetallic compound (IMC) nanoparticles (NPs) via in situ coreduction. In situ X-ray absorption spectroscopy (XAS) indicates that Pt undergoes a temperature-dependent transformation from single atoms to intermetallic compounds, and the catalyst reduced at 550 °C exhibits a superior HER performance in acidic media. The Pt/Ti3C2Tx-550 catalyst outperforms commercial Pt/Vulcan and has a small overpotential of 32.7 mV at 10 mA cm-2 and a low Tafel slope of 32.3 mV dec-1. The HER current was normalized by the mass and dispersion of Pt, and the mass activity and specific activity of Pt/Ti3C2Tx-550 are 4.4 and 13 times higher, respectively, than those of Pt/Vulcan at an overpotential of 70 mV. The density functional theory (DFT) calculations suggest that the (111)- and (100)-terminated Pt3Ti nanoparticles exhibit *H binding comparable to Pt(111), while the (110) termination has an *H adsorption that is too exergonic, thus poisoned in the low overpotential region. This work demonstrates the potential of MXenes as platforms for the design of electrocatalysts and may spur future research for other MXene-supported metal catalysts that can be used for a wide range of electrocatalytic reactions.

Two-dimensional transition metal carbides as supports for tuning the chemistry of catalytic nanoparticles

Supported nanoparticles are broadly employed in industrial catalytic processes, where the active sites can be tuned by metal-support interactions (MSIs). Although it is well accepted that supports can modify the chemistry of metal nanoparticles, systematic utilization of MSIs for achieving desired catalytic performance is still challenging. The developments of supports with appropriate chemical properties and identification of the resulting active sites are the main barriers. Here, we develop two-dimensional transition metal carbides (MXenes) supported platinum as efficient catalysts for light alkane dehydrogenations. Ordered Pt3Ti and surface Pt3Nb intermetallic compound nanoparticles are formed via reactive metal-support interactions on Pt/Ti3C2Tx and Pt/Nb2CTx catalysts, respectively. MXene supports modulate the nature of the active sites, making them highly selective toward C–H activation. Such exploitation of the MSIs makes MXenes promising platforms with versatile chemical reactivity and tunability for facile design of supported intermetallic nanoparticles over a wide range of compositions and structures.

Role of Voltage and Gas Pressure in Determining the Mean Diameter of Sn-Bi-Ag Intermetallic Compound Nanoparticles Formed by Pulsed Wire Discharge

Nanoscale Sn-Bi-Ag compound powders were successfully synthesized using the pulsed wire discharge (PWD) method. In PWD, when a high current is passed through high-density metal wires, the wires explode because of resistance heating, forming fine particles or metal vapor. In this study, we used Sn-Bi and Ag wires in order to obtain three-component nanopowders. A high current was applied to the wires between the electrodes in a N2 atmosphere. We discussed the results based on the K factor, which is the ratio of the charging energy of the capacitor to the vaporization energy of the wire. The three-component (Sn-Bi-Ag) nanoparticles were synthesized under a N2 atmosphere at 4 and 6 kV. From the particle-size distribution curves, it was found that the mean particle diameter (D1) values of the Sn-Bi and Ag nanopowders were within the range of 16.32-42.37 nm under each condition. The melting point of the Sn-Bi-Ag nanoparticles was found to be within the range of 188.68-214.97 ℃, which is about 40 ℃ lower than that obtained from the phase diagram and computational thermodynamics of the Sn-Bi-Ag system. In this study, the nanopowders were obtained by subjecting the wires at extreme energies, to improve their solid solubility. (Received February 8, 2017; Accepted July 26, 2017)

Synthesis of Sn–Bi–Cu Intermetallic Compound Nanoparticles by Pulsed Wire Discharge of Sn–Bi and Cu Wires

Synthesis of Sn–Bi–Cu Intermetallic Compound Nanoparticles by Pulsed Wire Discharge of Sn–Bi and Cu Wires

Lattice Contracted Ordered Intermetallic Core-Shell PtCo@Pt Nanoparticles: Synthesis, Structure and Origin for Enhanced Oxygen Reduction Reaction

Electrocatalysts in ordered intermetallic phases are highly desirable for the oxygen reduction reaction (ORR) with enhanced activity and durability. Here, we develop carbon-supported ordered core-shell PtCo@Pt (O-PtCo@Pt/C with the Pt:Co atomic ratio of 1:1) intermetallic compound (IMC) nanoparticles with the metal loading as high as of 60 wt%, aiming to understand the effects of the ordered structure, metal loading and particle size on the ORR performance. The O-PtCo@Pt/C is synthesized by a two-step reduction method and followed by a heat-treatment. The mean particle diameter is about 4.8 nm with a narrow size distribution. The surface of the core-shell nanoparticles is enriched with about 3 layers of Pt atoms after the acid treatment. Noticeable lattice contraction in the O-PtCo@Pt/C has been observed by X-ray diffraction and high resolution transmission electron microscopy. Such a structurally ordered PtCo@Pt/C catalyst exhibits higher ORR activity and durability than the disordered PtCo/C and commercial Pt/C catalysts, which could be ascribed to the Pt-rich shell, ordered core structure, small particle size, lattice contraction, as well as strengthened d-hybridization. This research provides new insights to design an ordered intermetallic structure in the core and a Pt-rich surface with special facets for the excellent catalytic performance.

Role of voltage and gas in determining the mean diameter in Sn-58 Bi intermetallic compound nanoparticles for pulsed wire discharge

Pulsed wire discharge using Sn-58 Bi wires was used to synthesize intermetallic Sn-58 Bi compound nanoparticles. We investigate that nanopowder particle size is controlled by voltage and gas atmosphere. A large pulsed current was applied to the alloy wires set between the electrodes in two gas atmosphere such as Ar, N2. We were discussed the results based on the k factor. The k factor means Ec/Ev, where Ec and Ev are the charging energy of the capacitor and the vaporization energy of the wire. Nanoparticles whose composition was close to that of Sn-58 Bi were synthesized under N2 atmosphere and 6 kV voltage. In such conditions, the applied energy to the wire was higher than sublimation energy of the wires. Under the other experimental conditions, other phases such as Bi-rich and Sn-Bi compound phases were detected. The major results in this study demonstrate the synthesis of alloy nano powders by using alloy wire.

Intermetallic Compound Nanoparticles Dispersed on the Surface of Oxide Support as Active and Selective Catalysts

Preparation of nanoparticles of intermetallic compounds and their application to various catalytic reactions are summarized. On the surface of silica support, single-phase nanoparticles of intermetallics with various combinations of elements were obtained by co-impregnation and/or successive impregnation procedures. On alumina support, its strong interaction with metal species requires another preparation procedure, liquidphase reduction, to obtain intermetallic nanoparticles with high phase purity. Most of the particles formed on both supports had diameters of 3³20nm. Thus prepared intermetallic nanoparticles were used as catalysts for various reactions such as H2-D2 equilibration, selective hydrogenation, dehydrogenation, oxidation and isomerization. The catalytic activity and selectivity of nanoparticles differed from each other depending on the combination and composition of two elements. In some cases, the intermetallic catalysts gave much higher activity and/or selectivity than their component monometallic catalysts. The unique catalytic properties of intermetallic compounds were discussed in terms of the electronic and geometric factors compared with pure metals. [doi:10.2320/matertrans.MF201408]

Facile route for the preparation of ordered intermetallic Pt3Pb–PtPb core–shell nanoparticles and its enhanced activity for alkaline methanol and ethanol oxidation

Pt3Pb(core)–PtPb(shell) intermetallic compound nanoparticles (NPs) were synthesized on carbon black (CB) by converting nanocrystalline Pt to an ordered intermetallic compound with the reduction of Pb ions. The Pt3Pb–PtPb core–shell NPs were characterized by analyzing their crystal structures with powder X-ray diffraction (pXRD), hard X-ray photoemission spectroscopy (HX-PES), and transmission electron microscopy (TEM). The synthesized NPs exhibited enhanced catalytic activity and relatively stable cycle performance towards methanol (MeOH) and ethanol (EtOH) oxidation in an alkaline aqueous solution. The improved catalytic performance of the Pt3Pb–PtPb core–shell NPs might be attributed to both the enhancement of EtOH dehydrogenation and the higher concentration of surface OHads at lower potential on the modified PtPb surface in the Pt3Pb–PtPb core–shell NPs.

Determining factor of median diameter in intermetallic compound nanoparticles prepared by pulsed wire discharge

The preparation of NiAl intermetallic compound nanoparticles was carried out by pulsed wire discharge (PWD) using twisted pure Ni and Al wires in N2 ambient gas with varying number of turns of the wire (Nt), energy ratio (K), and ambient gas pressure (P). From the voltage and current waveforms during the wire heating, the energy deposition ratio up to the voltage peak (Kp) was calculated. It increased with an increase in Nt to 0.4 turns/mm and with increases in K and P. Under all the conditions, with an increase in Kp, the Ni composition ratio of the prepared particles (CNi) became closer to that of the wire (= 51.2 mol %). Furthermore, the collection rate (Rc) increased and the median particle diameter (d50) decreased. In particular, the change in d50 due to the change in Nt was not predicted by the relationship of d50 and Dth in our previous report. Single-phase NiAl intermetallic compound nanoparticles were successfully prepared under the condition in which Nt is 0.4 turns/mm, K is 3.4, and P is 100 kPa, where relatively high value of Kp was obtained. From these results, Kp was determined to be an important factor that determines the composition, collection rate, and median diameter of intermetallic compound nanoparticles synthesized by PWD using different kinds of twisted wires under various experimental conditions. This may be because of the selective wire heating in high-resistance parts that are associated with the introduction of lattice defects and/or necks by overwinding.

Synthesis of intermetallic NiAl compound nanoparticles by pulsed wire discharge of twisted Ni and Al wires

Pulsed wire discharge using twisted Ni and Al wires has been tried to synthesize intermetallic NiAl compound nanoparticles. The effects of wire twisting and gas atmosphere conditions on the constituent phases of the synthesized particles were investigated. Ni and Al wires corresponding to the molar composition ratio of 1:1 were hand-twisted to form twined wires with various twisting number per 25 mm which is the nominal span length between the electrodes. Pulsed large current was applied to the twisted wires set between the electrodes in N2 or Ar atmosphere. The results were discussed based on the deposited energy in the wires which can be evaluated from the voltage and current at the wires. Nanoparticles consisting of almost single-phase NiAl compound were synthesized at limited conditions of the N2 atmosphere and the twisting number range of 5–15 turn per 25 mm. At these conditions, the deposited energy in the wires was higher than the vaporization energy of the wires. At the other experimental conditions, other phases such as Ni2Al3 compound phase and metallic Al phase were detected as well as the NiAl phase. Major experimental results in this study can be explained based on the deposited energy in the wires.

复合纳米金属间化合物Ag2Al的制备及其结构表征

Ag2Al intermetallic compound nanoparticles were synthesized by the flow-levitation method. The morphologies, granularity and phase structure were investigated by transmission electron microscope, X-ray diffractometer, and energy dispersive spectrometer. The results indicate that the prepared nanoparticles are regular spheres, with the grain size ranging from 20 to 110 nm. The nanoparticles are mainly composed of Ag2Al, including a little Al. The data of chemistry elementary analysis indicate that the atomic ratio of Ag to Al in the nanoparticles is about 66.5∶33.5. The grain size of Ag2Al in the prepared nanoparticles is about 33 nm, and that of Al is about 21 nm.