Au-Pt Alloy Research Articles

Ultralow magnetic susceptibility in pure and Fe(Bi)-doped Au-Pt alloys improved by structural strain regulation

Designing and manufacturing multi-component alloy samples with ultralow magnetic susceptibilityχ(<10-6cm3mol-1) is crucial for producing high-quality test masses to successfully detect gravitational wave in the LISA and TianQin projects. Previous research has idenfified AuPt alloys as a potential candidate for test masses, capable of achieving ultralow magnetic susceptibility that meets the requirements from both theoretical and experimental perspectives. In this study, we discover that the structural strain regulation (i.e. tensile and stress) can effectively optimize and further reduce the ultralow magnetic susceptibility of AuPt allpys, while fully understanding their underlying physical mechanisms. More importantly, even when doped with trace elements such as Fe or Bi impurity, strain regulation can still effectively reduce the magnetic susceptibility of the doped AuPt alloy to the desired range. Our theoretical calculations also reveal that, when the strain ratioηis controlled within in a relatively small range (<2.0%), the regulaton effect on the ultralow magnetic susceptibilities of pure or doped-AuPt alloys remains significant. This property is beneficial for achieving ultralow or even near-zero magnetic susceptibility in real AuPt alloy samples.

Atomically Precise Au24Pt(thiolate)12(dithiolate)3 Nanoclusters with Excellent Electrocatalytic Hydrogen Evolution Reactivity.

[Au24Pt(C6)18]0 (C6 = 1-hexanethiolate) is twice as active as commercial Pt nanoparticles in promoting the electrocatalytic hydrogen evolution reaction (HER), thereby attracting attention as new HER catalysts with well-controlled geometric structures. In this study, we succeeded in synthesizing two new Au-Pt alloy nanoclusters, namely, [Au24Pt(TBBT)12(TDT)3]0 (TBBT = 4-tert-butylbenzenethiolate; TDT = thiodithiolate) and [Au24Pt(TBBT)12(PDT)3]0 (PDT = 1,3-propanedithiolate), by exchanging all the ligands of [Au24Pt(PET)18]0 (PET = 2-phenylethanethiolate) with mono- or dithiolates. Although [Au24Pt(TBBT)12(TDT)3]0 was synthesized serendipitously, a similar cluster, [Au24Pt(TBBT)12(PDT)3]0, was subsequently obtained by selecting the appropriate reaction conditions and optimal combination of thiolate and dithiolate ligands. Single crystal X-ray diffraction analyses revealed that the lengths and orientations of -Au(I)-SR-Au(I)- staples in [Au24Pt(TBBT)12(TDT)3]0 and [Au24Pt(TBBT)12(PDT)3]0 were different from those in [Au24Pt(C6)18]0, [Au24Pt(PET)18]0, and [Au24Pt(TBBT)18]0, and these subtle differences were reflected in the geometric and electronic structures as well as the HER activities of [Au24Pt(TBBT)12(TDT)3]0 and [Au24Pt(TBBT)12(PDT)3]0. Accordingly, the HER activities of products [Au24Pt(TBBT)12(TDT)3]0 and [Au24Pt(TBBT)12(PDT)3]0 were, respectively, 3.5 and 4.9 times higher than those of [Au24Pt(C6)18]0 and [Au24Pt(TBBT)18]0.

Mechanistic insight into piezo-catalytic H2 evolution on BiOCl loaded with AuPt alloy cocatalysts

The use of piezo-catalysis for H2 production from water at ambient conditions has recently gained significant attention, yet the importance of cocatalyst engineering has been largely overlooked. In this study, AuPt alloy nanoparticles were used as cocatalysts on the piezoelectric material BiOCl for H2 evolution driven by sonication. The Au:Pt ratio of 3:1 significantly enhanced the reaction, resulting in a doubling of H2 production compared to Au alone and a tripling compared to Pt alone. Experiments and simulations showed that AuPt alloys promote H* adsorption and facilitate the separation of piezoelectric carriers. Additionally, the cocatalysts enhance the piezo-catalytic reaction by increasing the stress and deformation of the BiOCl microplates. Unlike the photocatalytic process, the piezo-catalytic H2 evolution on BiOCl succeeded due to the suppression of BiOCl reduction by the periodically accumulated piezo-electrons and holes. This research highlights the critical role of cocatalyst engineering in optimizing piezo-catalytic H2 production and presents a promising strategy for efficient H2 generation.

Precipitation behavior of Pt-rich phase in Au72Pt28 alloy during aging process

Gold–Platinum (Au–Pt) alloy demonstrates considerable promise as a material for spacecraft proof mass, due to its ultra-low magnetic susceptibility. This study systematically investigates the effect of heat treatment on the microstructure evolution, magnetic properties, and mechanical performance of the Au72Pt28 alloy. The results indicate that the Pt-rich phase can be precipitated by discontinuous precipitation (DP) and continuous precipitation (CP) reactions. There is a competition between the two precipitation behaviors of Pt-rich phase, which is closely related to their diffusion path. With increasing ageing time and temperature, the discontinuous precipitates gradually coarsen and extend from grain boundaries into grain interior, while the Pt-rich phase nanoparticles precipitated by CP reaction uniformly distribute in the grain interior. Besides, the volume fraction of Pt-rich phase gradually increases, resulting in the increase of magnetic susceptibility. The coarsening of discontinuous precipitates is the main reason for the decrease in the nanoindentation hardness, and it increases rapidly due to a large number of intragranular Pt-rich phase nanoparticles.

Effects of cold plastic deformation on microstructure and magnetic susceptibility of Au-Pt alloys

Formation of the alloys of paramagnetic gold (Au) and diamagnetic platinum (Pt) holds promise for developing materials with ultra-low magnetic susceptibility. This study investigates the effects of cold plastic deformation on the mechanical properties and magnetic susceptibility of Au-29Pt alloys by microstructure characterization. After cold rolling, the Vickers hardness of the Au-Pt alloy increases from 138.35 HV to 218.28 HV at 80 % deformation. Meanwhile, the volume magnetic susceptibility exhibits a change from −19.10 ppm to −28.60 ppm with minor difference between the results measured from different orientations. The crystal orientation of the Au-29Pt alloys changes but no new phases or no textures are formed. With the increase of the deformation level from 0 % to 60 %, EBSD measurements demonstrates a ∼40-fold increment in average geometric dislocation density. The results indicate the formation of new defects, which are identified as edge dislocations and stacking faults via HRTEM. Consequently, the larger diamagnetic susceptibility at a higher deformation level is mainly correlated with the formation of defects. The results of this study could provide useful guidelines for the design of ultra-low magnetic susceptibility alloys.

Lithium-Mediated Nitrogen Reduction in a Flow Electrolyzer Cell Using Gas Diffusion Electrodes with Carbon-Based Electrocatalysts

Due to the sluggish kinetics in activating the chemically stable dinitrogen (N2) and the competing hydrogen evolution reaction in aqueous media, recent attention in the field of direct ammonia (NH3) electrosynthesis has been increasingly drawn to the lithium-mediated N2 reduction reaction (LNRR) in tetrahydrofuran (THF)-based non-aqueous electrolyte. In particular, near 100% faradaic efficiency (FE) and/or a current density (j) of 100 mA cm-2 has been demonstrated with unique electrolyte (proton-shuttle additive) and/or electrode designs (expansive electrochemical surface area) in single-compartment cells at elevated N2 pressure (5 – 20 bar).[1,2]A submerged electrode leads to electrolyte flooding and restricts to N2 mass transfer to the electrode surface where electrodeposited Li as an electron mediator is available.[3] However, flow cell electrolyzers containing gas-diffusion electrodes can improve this technology to practical relevance, which features the LNRR on the cathode and hydrogen oxidation reaction (HOR) on the anode. Differing from single-compartment cells, the HOR supplements the ethanol additive (<1 vol%) as the proton source, which not only prevents the oxidative electrolyte degradation but also reduces the energy consumption due to a lower equilibrium anode potential (E0 = 0 VRHE). Gas-diffusion electrodes (GDEs) are used in the few LNRR studies with flow cell configurations, which are prepared by electro- or electroless depositing electrocatalysts (e.g., Pt [4] or PtAu alloy [5]) onto a porous substrate.In this work, carbon-based electrocatalysts (Vulcan XC72R carbon black, battery-grade conductive carbon SUPER C45, and graphitic carbon SFG6L) as low-cost alternatives to previously studied precious metals are assessed for their LNRR performance in flow cells using an HOR anode. In comparison to Vulcan-supported Pt, XC72R and C45 can obtain similar NH3 production rates (rNH3 )and FE at the same . Continuous LNRR at -3 mA cm-2 was demonstrated with linearly increased NH3 production for over 8 h without catalyst layer detachment, which was also verified with open circuit and Ar control experiments (Fig. 1). By presenting the LNRR activity with GDEs spray-coated with carbon-based electrocatalysts, opportunities for future research are suggested, such as novel carbon materials and porous substrates other than SSC for facile N2 mass transfer and Li deposition.

AuPt bimetallic loaded defect state g-C3N4 enhances photocatalytic H2 evolution: Exploring synergistic effects and charge transfer mechanisms

AuPt alloy nanoparticles (NPs) were prepared using a simple photodeposition method to modify defective state g-C3N4 nanosheets (HCN) which contained N vacancies, B doping, and CN groups. The visible diffuse reflectance spectra (DRS) indicate that AuPt/HCN exhibits high light absorption capability. The photoluminescence spectrum (PL) and steady-state surface photovoltage (SPV) indicate that AuPt/HCN possesses a high rate of photogenerated charge separation and a high efficiency of photogenerated electron transfer. The electrochemical tests indicate that AuPt/HCN exhibits lower electrochemical impedance. AuPt/HCN (1.0 wt%) exhibits outstanding photocatalytic hydrogen evolution efficiency, producing hydrogen at a rate of 2095 μmol·g−1·h−1 under visible light, which is 2.10 times and 1.55 times higher than that of monometallic Au/HCN (1.0 wt%) (997 μmol·g−1·h−1) and Pt/HCN (1.0 wt%) (1349 μmol·g−1·h−1), respectively. The bimetallic synergistic effect of AuPt alloy NPs co-catalysts enhances the photocatalytic hydrogen evolution activity of AuPt/HCN composite photocatalysts.

Unraveling oxygen-driven surface segregation dynamics in platinum-gold alloys

In this study we use high-energy resolution and fast X-ray Photoelectron Spectroscopy (XPS) measurements combined with Density Functional Theory (DFT) calculations to investigate the interplay between surface segregation and bulk migration of Pt atoms on Au(111) in an oxygen environment. We demonstrate that the segregation of Pt atoms is significantly influenced by the oxygen partial pressure and identify a range of O2 pressure where PtAu surface alloy formation is inhibited while promoting the formation of Au oxide. These findings are essential to understand the compositional changes in the bimetallic surface alloy, which could potentially lead to modifying the catalytic properties of PtAu up to catalyst deactivation. Our results offer a strategy to control Pt surface coverage on Au(111), a quantity that is of paramount relevance given the applications of PtAu alloys as catalysts in reactions such as the oxygen reduction reaction or the oxidation of methanol and carbon monoxide. Additionally, our findings indicate a method for controlling the composition and properties of the surface of PtAu catalysts through adjustments made during the formation of the PtAu alloy.

Composition design of gold-platinum alloy with ultra-low magnetic susceptibility: First-principles and experimental validation

Gold-platinum (Au-Pt) alloy has aroused considerable attention due to its ultra-low magnetic susceptibility (MS) in testing mass (TM) on spacecraft. However, the effect of Au content on the properties of the alloy has not yet been understood. In this study, the composition design of Au-Pt alloy with ultra-low MS was achieved through density functional theory (DFT) and experimental methods. The elastic, thermal properties and electronic structure were systematically investigated, the composition range was further optimized and Au75Pt25 was determined to be the most suitable alloy for TM material. The phase composition of this alloy after cold rolling and solid solution was characterized, indicating a single-phase FCC structure. In addition, there is a good validation between the experimental Vickers hardness and the DFT results. This work provides new insights into the compositional optimization of Au-Pt alloys and lays the foundation for alloy development.

Ultrasonication‐Assisted Preparation of Au‐Pt/ZrO2 Catalysts for the Selective Base‐Free Oxidation of Glucose to Glucaric Acid

AbstractSelective catalytic oxidation of glucose to glucaric acid is still challenging due to the potential formation of a large range of by‐products. ZrO2 supported AuPt catalysts are very efficient for this reaction under base‐free conditions, in aqueous phase. Different preparation methods were tested and the catalysts synthesized by co‐impregnation using NaBH4 as reductant gave the most promising results. We demonstrated that the presence of a pure AuPt alloy is critical for the selective formation of glucaric acid. We have shown that when ultrasonication was used during preparation, less by‐products were formed, increasing significantly final yield of glucaric acid, up to 71 %. The Au/Pt ratio affects the catalytic results and an optimal ratio around 1.1 was determined. Finally, the catalyst is stable up to 196 h in continuous reactor.

Achieving a high-performance electrochemical sensor for electrochemical detection of ammonia–nitrogen based on electrodepositing PtAu alloys and polypyrrole on Ni foam

The environment pollution problmes resulting from ammonia-nitrogen have been paid more attentions. Efficient and accurate detection of ammonia–nitrogen in aqueous enivronment including tap water, lake water and sea water is meaningful. In this work, a novel PtAu alloy sensor was designed and fabricated via coelectrodeposition method on Ni foam (NF). In addition, polypyrrole (PPy) was electrochemically grown on NF surface to avoid corrosion of NF during the electrodepositing process of PtAu alloy. Under the optimal condition, the prepared Pt5Au3-PPy-NF-1 showed the great electrocatalytic performance for ammonia oxidation reaction with the current density of 15.55 mA and great detection ability with the high sensitivity of 8.2 µA µM−1, low detection limit of 1.05 µM and three linear ranges from 4 to 50 µM, from 50 to 400 µM and from 400 to 1000 µM. The enhanced performances could be attriubted to: 1) Pt showed the electrochemial catalytic activity for ammonia oxidation reaction and Au showed the lower adsortion energy to N atom, as well as optimized electronic structure of Pt and Au.

Development of electrode by using gold-platinum alloy nanopar¬ticles for electrochemical detection of serum amyloid A protein

Gold-platinum alloy nanoparticles (AuPtNP) were electrochemically deposited on the surface of indium-tin-oxide (ITO) modified with (3-aminopropyl)triethoxysilane (APTES), after optimizing deposition conditions for the electroplating solution and number of deposition cycles. Different part ratios of Au/Pt used were 4/0, 3/1, 2/2, 1/3 and 0/4 (AuNP, Au3Pt1, Au2Pt2, Au1Pt3 and PtNP, respectively) in preparation of 1 mM solutions. FE-SEM, EDAX and XRD surface characterization techniques were used to confirm the presence of deposited AuPt alloy nanoparticles on the modified ITO surface. Electrochemical methods (CV, DPV and EIS) were used to investigate the electrochemical properties of prepared electrodes in the presence of ferri/ferrocyanide redox couple, which indicated the following increasing order of electrocatalytic peak current: Au &lt; Au2Pt2 &lt; Pt &lt; Au1Pt3 &lt; Au3Pt1. The most active electrode, Au3Pt1NP/APTES/ITO (with Au/Pt part ratio 3:1), was further used to fabricate the immunoelectrode SAA-Ab/Au3Pt1NP/APTES/ITO. The prepared immunoelec­trode was tested for detection of serum amyloid A protein biomarker (APO-SAA) by immobilising SAA-specific antibodies (SAA ½ Ab) on its surface. Sensing studies on this immunoelectrode, performed by DPV technique, revealed the SAA biomarker detection in the linear range of 10 to 106 fg ml-1. The limit of detection was calculated as 7.0 fg ml-1.

Highly Sensitive and Selective Toluene Gas Sensors Based on ZnO Nanoflowers Decorated with Bimetallic AuPt.

Efficient sensors for toluene detecting are urgently needed to meet people's growing demands for both environment and personal health. Metal oxide semiconductor (MOS)-based sensors have become brilliant candidates for the detection of toluene because of their superior performance over gas sensing. However, gas sensors based on pure MOS have certain limitations in selectivity, operating temperature, and long-term stability, which hinders their further practical applications. Noble metals (including Ag, Au, Pt, Pd, etc.) have the ability to enhance the performance of MOS-based sensors via surface functionalization. Herein, ZnO nanoflowers (ZNFs) modified with bimetallic AuPt are prepared for toluene detection through hydrothermal method. The response of a AuPt@ZNF-based gas sensor can reach 69.7 at 175 °C, which is 30 times, 9 times, and 10 times higher than that of the original ZNFs, Au@ZNFs, and Pt@ZNFs, respectively. Furthermore, the sensor also has a lower optimal operating temperature (175 °C), good stability (94% of previous response after one month), and high selectivity towards toluene, which is the result of the combined influence of the electronic and chemical sensitization of noble metals, as well as the unique synergistic effect of the AuPt alloy. In summary, AuPt@ZNF-based sensors can be further applied in toluene detection in practical applications.

Au-Pt alloy nanoislands for highly sensitive localized surface plasmon resonance sensing of antimony(III) ions

Alloy nanomaterials exhibit superior plasmonic properties that can exceed traditional single-metal nanomaterials. Hence, they hold great potential for developing highly sensitive sensors capable of detecting small analytes in nanoscale. The self-assembly Au-Pt alloy nanoislands structure is used, for the first time, for localized surface plasmon resonance sensing. Its nanostructure has been studied and characterized by using various microscopy and spectroscopy techniques. It was found that Au0.94-Pt0.06 was the optimum composition with the best sensitivity toward the change of refractive index over various concentrations of NaCl solution and double the sensitivity than that of pure Au nanoislands. The Au-Pt chip with its surface functionalized with nitrotyrosine was successfully developed for highly sensitive detection of antimony (III) ion, the electronic properties of the interaction between nitrotyrosine and Sb during the biosensing was explored using density functional theory simulation to explain their strong adsorption to make nitrotyrosine a successful receptor. The sensor achieved a limit of detection of 0.0504 ppb, which is the best ever value among all those reported for Sb(III) ions sensing. With its high selectivity tested among 14 other common elements, the present Sb(III) ion LSPR sensor also possesses attributes of label-free, easy to fabricate and simple to operate.

Novel image-guided marker aimed at organ-preserving therapies for prostate cancer.

We developed fiducial imaging-guidance markers for the prostate with less imaging artifacts than currently commercially available markers. The aim of this study was to evaluate the imaging artifacts and potential usefulness and safety of these novel fiducial imaging markers in preclinical experiments. We selected specific metal materials and a shape that can minimize artifacts in line with a license we obtained for a metal with a gold-platinum (Au-Pt) alloy composition that maximized artifact-free MRI images. Both phantom and canine prostate tests were conducted in order to evaluate the imaging artifacts for three imaging modalities, MRI, CT and ultrasound, and the risk of migration of the markers from the site of insertion to elsewhere, as well as crushing. The newly developed Au-Pt material had less imaging artifacts in the MRI, CT and ultrasound imaging modalities in comparison with current commercially available fiducial markers made from gold materials only. The Au-Pt markers had sufficient strength and durability and were considered to be potentially clinically useful and safe markers. The developed Au-Pt markers could be potential tools for accurate lesion-targeted, organ-preserving therapies such as lesion-targeted focal therapy and active surveillance in addition to conventional radiation therapies.

Efficient reduction of nitrate to ammonia on AuPt@ZIF-8 composite film

The nitrate reduction represents a sustainable strategy for water denitrification. Herein we design ZIF-8 coated porous AuPt alloy composite film for electrocatalytic nitrate reduction with superior ammonia yield of (131.5...

PtAu alloying-modulated hydroxyl and substrate adsorption for glycerol electrooxidation to C3 products

A honeycomb-like PtAu alloy catalyst has been developed to modulate the adsorption capacity of OH− species and adsorption configuration of glycerol on the catalyst surface for electrocatalytic glycerol upgrading of C3 chemicals.

Atomic insight into mechanical behavior of AuPt alloys

AuPt alloys are widely applied in electronics, aerospace, and precision equipment fields. A thorough understanding of the mechanical behavior of AuPt alloys is critical for their potential applications. Here, we leverage molecular dynamics (MD) method to for the first reveal the effects of microstructure and temperature on mechanical behavior of AuPt alloys from atomic level. The nanoindentation of monocrystalline (MC), nanotwinned (NT), and nanocrystalline (NC) AuPt alloys are performed. The results demonstrate that the mechanical properties of the MC AuPt alloy are excellent at 77 K because of dislocation strengthening while poor at high temperature due to amorphous behavior. The introduction of twinning boundary (TB) greatly improves the mechanical properties of AuPt alloy by preventing the stress spread and promoting dislocation activity. The mechanical behavior of NC AuPt alloy is strongly dependent on grain size. With increasing average grain size, the dominant plastic deformation mechanism of NC AuPt alloy changes from GB migration to dislocation motion and then to GB destruction. An appropriate grain size should be selected to inhibit GB migration or GB destruction, thereby achieving the enhancement of NC AuPt alloy through dislocation strengthening. This work provides an important theoretical basis for the subsequent design of AuPt alloys with desirable mechanical performances to extend the application prospects of noble metals.

Enhancing the piezo-photocatalytic tetracycline degradation activity of BiOBr by the decoration of AuPt alloy nanoparaticles: Degradation pathways and mechanism investigation

AuPt alloy nanoparaticles were successfully decorated on the BiOBr surface to form AuPt/BiOBr piezo-photocatalysts via a photoreduction route. The removal of organic dyes (acid orange 10 (AO10) and rhodamine B (RhB)) were selected to estimate the photocatalytic activity of samples under simulated sunlight irradiation, which reveals that the AuPt/BiOBr composite manifests remarkably enhanced photocatalytic degradation ability compared with Au/BiOBr, Pt/BiOBr and bare BiOBr. Notably, the piezo-photocatalytic removal activity of AuPt/BiOBr towards the degradation of tetracycline (TC) was evaluated under the simulated sunlight and ultrasound irradiation. It is found that the piezo-photocatalytic removal performance of AuPt/BiOBr is obviously super to its individual piezo- and photocatalytic results, and its piezo-photocatalytic efficiency of TC increased by ∼ 33.6% and ∼ 53.3% in comparison to corresponding photocatalytic and piezocatalytic degradation efficiency. The piezo-photocatalytic degradation pathway of TC was systematacially discussed and proposed. The built-in electric field caused by the piezoelectric effect of AuPt/BiOBr sample significantly accelerate the bulk migration and separation of induced charges. On the other hand, the surface plasmonic resonance (SPR) effect of AuPt alloy nanoparaticles provided more hot electrons for piezo-photocatalytic reaction, meanwhile the AuPt alloy nanoparticles also promote the surface migration of induced charges on the AuPt/BiOBr sample.

Atomic-scale investigation of Pt composition on deformation mechanism of AuPt alloy during nano-scratching process

In this research, we performed molecular dynamics (MD) simulation to investigate the material removal mechanism and subsurface damage formation during nano-scratching of the gold-platinum (AuPt) alloy. In order to comprehend the deformation mechanism of AuPt alloy during nano-scratching, the influences of Pt composition in workpiece on the machining performance were analyzed. The results indicate that the Pt composition has a significant influence on the surface morphology including piling-up of workpiece atoms and elastic recovery on the machined surface. During the deformation process, the average shear strain of workpiece atoms decreases when the Pt composition increases. Besides, the average scratching force increases apparently with obvious fluctuation as the Pt composition increases. For the subsurface damage formation, typical crystal defects including atomic clusters, V-shape stacking fault couples, and stacking faults tetrahedra were observed in the workpiece subsurface. The lengths of perfect dislocations and Shockley partial dislocations gradually increase as Pt composition increases, while the overall length of sessile dislocations decreases obviously. Meanwhile, thinner stacking faults were formed in the workpiece subsurface as the balanced width of stacking fault gradually decreases when the Pt composition increases. This work contributes to a better understanding of the nanoscale deformation mechanism of bimetallic materials during micro or nano machining process.