Au-Pt Alloy Research Articles

Engineering eg Orbital Occupancy of Pt with Au Alloying Enables Reversible Li-O2 Batteries.

Constructing well-designed catalysts to accelerate OER catalytic activity and alleviate the charge overpotential is prevailing for achieving sophisticated Li-O2 batteries. Herein, we report a concept for engineering the eg occupancy of Pt with M alloying (M=Au, Ru) to tune the charge overpotentials for achieving high-performance Li-O2 batteries. The X-ray photoelectron spectroscopy results coupled with density functional theory (DFT) calculations reveal that the highly electronegative Au can capture more eg electrons from Pt, leading to less eg electrons of Pt in PtAu than that in PtRu. The lower eg occupancy of Pt atoms in PtAu alloys entails the upward shift of the Pt d band, which causes a strong binding strength towards the intermediates (LiO2 ), thereby decreasing the OER energy barrier. As a consequence, the Li-O2 battery with a PtAu cathode delivers a low charge overpotential of 0.36 V and superior cycle life of 220 cycles at a cutoff capacity of 1000 mAh g-1 , which is among the best in the reported noble metal-based cathodes.

Structural and electronic properties of Pt modified Au(100) surface

Investigations on electronic and geometric structures of platinum adsorbed on monocrystalline gold surfaces are important for understanding the remarkable catalytic properties of bimetallic Pt–Au systems. Herein, the morphology of quasi-hexagonal (hex) Au(100) surface after deposition of platinum for coverage up to 0.5 monolayer (ML) has been investigated by scanning tunneling microscopy (STM). For coverage range 0.2–0.4 ML the creation of elongated islands with mono-atomic height is observed. The islands consist of flat phase of disordered Pt-Au alloy which coexists with nanowire-like features with a hex atom arrangement and quantized width. Annealing the Pt/Au(100) system at 100–150 °C changes the surface morphology. The islands disappear and the topmost layer of the surface consists of flat phase of Pt–Au alloy which coexists with the hex-stripes. Small domains of ordered c(2 × 2) structure of Pt–Au alloy are found. The electronic properties of this structure have been investigated by ab-initio calculations. The obtained results allow to distinguish the Pt from Au atoms by their appearance in the STM images. The calculated electronic structures indicate a bonding creation between Pt and Au atoms and an electron d-states redistribution of Pt in comparison to the bare Pt(100)-(1 × 1) surface.

MOF Encapsulated AuPt Bimetallic Nanoparticles for Improved Plasmonic-induced Photothermal Catalysis of CO2 Hydrogenation.

Exploring new catalytic strategies for achieving efficient CO2 hydrogenation under mild conditions is of great significance for environmental remediation. Herein, a composite photocatalyst Zr-based MOF encapsulated plasmonic AuPt alloy nanoparticles (AuPt@UiO-66-NH2 ) was successfully constructed for the efficient photothermal catalysis of CO2 hydrogenation. Under light irradiation at 150 °C, AuPt@UiO-66-NH2 achieved a CO production rate of 1451 μmol gmetal -1 h-1 with 91 % selectivity, which far exceeded those obtained by Au@Pt@UiO-66-NH2 with Pt shell on Au (599 μmol gmetal -1 h-1 ) and Au@UiO-66-NH2 (218 μmol gmetal -1 h-1 ). The outstanding performances of AuPt@UiO-66-NH2 were attributed to the synergetic effect originating from the plasmonic metal Au, doped active metal Pt, and encapsulation structure of UiO-66-NH2 shell. This work provides a new way for photothermal catalysis of CO2 and a reference for the design of high-performance plasmonic catalysts.

Reconciling of experimental and theoretical insights on the electroactive behavior of C/Ni nanoparticles with AuPt alloys for hydrogen evolution efficiency and Non-enzymatic sensor

We focused on a new feasible strategy for fabricating carbon-coated nickel (C/Ni) nanoparticles (NPs) with a AuPt alloy system using an integrated pulsed laser irradiation and ultrasonochemical process and provided insights on transferable electrocatalytic active surface states for HER and the selective detection of 1,4-benzenediol. The detailed physical characterization and electrochemical analyses revealed that the C/Ni–AuPt (0.12 mg/mL of AuPt) alloy showed exceptional electrocatalytic activities for HER in acidic media, with a low overpotential of 0.131 V at 10 mA/cm2, an exchange current density of 0.125 mA/cm2, a Tafel slope of 66 mV/dec, and a Tafel constant of 0.060 V. Additionally, an optimized C/Ni–AuPt electrocatalyst showed a broad dynamic linear response (50–250 μM) with high sensitivity (0.1134 μAμM−1cm−2) and low detection limit (0.185 μM) for sensing 1,4-benzenediol. Furthermore, an optimized C/Ni–AuPt alloys exhibited excellent electrochemical performance, long-term durability, and structural stability owing to the electronic effect of effective charge transfer from Au to Pt atoms, caused by a shift in the d-band center of Pt in AuPt alloys. The addition of C/Ni increased the active-sites of AuPt alloys because of the synergistic effect. Consequently, they provided abundant electrochemically active-surface areas necessary for the good dispersion of AuPt alloys. Alternatively, the strain effect was negligible in the C/Ni–AuPt structure. DFT calculations revealed that placing C/Ni NPs in direct contact with AuPt alloys displaces the d-band center of Au and Pt closer to the Fermi level, implying an increased activity of the electrocatalytic performance.

Coupling Natural Halloysite Nanotubes and Bimetallic Pt-Au Alloy Nanoparticles for Highly Efficient and Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid.

The aerobic oxidation of 5-hydroxymethylfurfural (HMF), a key platform compound derived from biomass, to 2,5-furandicarboxylic acid (FDCA) is a highly important reaction in the production of green and sustainable chemicals. Here, we developed a highly efficient and stable halloysite-supported Pt-Au alloy catalyst for the selective oxidation of HMF to FDCA. The catalyst was synthesized through the organosilane functionalization of halloysite nanotubes, followed by the in situ formation and dispersion of Pt-Au alloy nanoparticles on the internal and external surfaces of nanotubes. The composition, morphology, and structure of the prepared catalyst were characterized. The catalyst with the optimal composition of Pt/Au molar ratio of 1/4 and metal loading of 1.5 wt % exhibited outstanding catalytic activity for the oxidation of HMF to FDCA using O2 as an oxidant with 100% conversion of HMF and 99% selectivity of FDCA. This excellent catalytic performance is mainly attributed to the high dispersion and alloying effects of bimetallic nanoparticles, which promoted the activation of reactants or intermediates and further improved FDCA selectivity. Furthermore, the halloysite-supported Pt/Au bimetallic catalyst showed high stability and reusability. This study provides a promising strategy by combining clay mineral halloysite and bimetallic alloys for developing efficient catalysts with high FDCA selectivity and stability for the oxidation of HMF to FDCA.

Abnormal Metal Bond Distances in PtAu Alloy Nanoparticles: In Situ Back-Illumination XAFS Investigations of the Structure of PtAu Nanoparticles on a Flat HOPG Substrate Prepared by Arc Plasma Deposition

Abnormal Metal Bond Distances in PtAu Alloy Nanoparticles: <i>In Situ</i> Back-Illumination XAFS Investigations of the Structure of PtAu Nanoparticles on a Flat HOPG Substrate Prepared by Arc Plasma Deposition

Bimetallic Aupt Alloy Nanoparticles Decorated on Zno Nanowires Towards Efficient and Selective H2s Gas Sensing

Bimetallic Aupt Alloy Nanoparticles Decorated on Zno Nanowires Towards Efficient and Selective H2s Gas Sensing

Architecting the Aupt Alloys for Hydrazine Oxidation as an Anolyte in Fuel Cell: Comparative Analysis of Hydrazine Splitting and Water Splitting for Energy-Saving H2 Generation

Architecting the Aupt Alloys for Hydrazine Oxidation as an Anolyte in Fuel Cell: Comparative Analysis of Hydrazine Splitting and Water Splitting for Energy-Saving H2 Generation

Synthesis of Ultrathin Aupt Alloy Porous Nanowires with Abundant Electrocatalytic Active Sites for Excellent Electrocatalysts

Synthesis of Ultrathin Aupt Alloy Porous Nanowires with Abundant Electrocatalytic Active Sites for Excellent Electrocatalysts

Enhanced Electrocatalytic Oxidation of Small Organic Molecules on Platinum-Gold Nanowires: Influence of the Surface Structure and Pt-Pt/Pt-Au Pair Site Density.

The electrochemical oxidation of small organic molecules (SOMs) such as methanol and glucose is a critical process and has relevant applications in fuel cells and sensors. A key challenge in SOM oxidation is the poisoning of the surface by carbon monoxide (CO) and other partially oxidized intermediates, which is attributed to the presence of Pt-Pt pair sites. A promising pathway for overcoming this challenge is to develop catalysts that selectively oxidize SOMs via "direct" pathways that do not form CO as a primary intermediate. In this report, we utilize an ambient, template-based approach to prepare PtAu alloy nanowires with tunable compositions. X-ray photoelectron spectroscopy measurements reveal that the surface composition matches that of the bulk composition after synthesis. Monte Carlo method simulations of the surface structure of PtAu alloys with varying coverage of oxygen adsorbates and varying degrees of oxygen adsorption strength reveal that oxygen adsorption under electrochemical conditions enriches the surface with Pt and a large fraction of Pt-Pt sites remain on the surface even with the Au content of up to 50%. Electrochemical properties and the catalytic performance measurements of the PtAu nanowires for the oxidation of methanol and glucose reveal that the mechanistic pathways that produce CO are suppressed by the addition of relatively small quantities of Au (∼10%), and CO formation can be completely suppressed by 50% Au. The suppression of CO formation with small quantities of Au suggests that the presence of Pt-Au pair sites may be more important in determining the mechanism of SOM oxidation rather than Pt-Pt pair site density.

Photodeposition of alloyed Au-Pt nanoparticles on TiO2 for the enhanced catalytic oxidation of HCHO at room temperature

Catalytic oxidation has been considered as one of the most promising strategies for the removal of indoor HCHO which causes multiple health problems. Alloyed Au-Pt showed potential for catalytic oxidation reactions, but the reports on HCHO oxidation are limited. In addition,understanding on the catalytic mechanism is lacking. In this work, a sodium citrate assistant photodeposition process was developed to fabricate highly dispersed dual Au-Pt alloy with 2–3 nm on the surface of TiO2. The turnover frequency of Au-Pt/TiO2 (68.6 h-1) is much higher than that of Pt/TiO2 (19.9 h-1). This enhancement was also confirmed on different TiO2 supports and with different Pt loading. Based on the experimental and density functional theory calculations, it was found that the alloyed Au-Pt has more metallic Pt and is beneficial for the adsorption and dissociation of oxygen. Therefore, the rapid conversion of dioxymethylene species to formate species, with reduced reaction barrier, promotes the performance in catalytic oxidation of HCHO.

Dual-phase Au-Pt alloys free from magnetic susceptibility artifacts in magnetic resonance imaging

PurposeMagnetic resonance imaging (MRI) devices are frequently used in image-based diagnosis. In the case of large artifacts, which are generated in magnetic resonance (MR) images when magnetic materials, such as metals, are present in the body, these devices are less useful. This study aimed to develop a dual-phase Au-Pt alloy that does not generate artifacts in MR images and has high workability to prepare medical devices. Materials and methodsA processing method to produce a dual-phase Au-Pt alloy was established, and the magnetic susceptibility and artifacts of different alloy compositions were determined using a SQUID (superconducting quantum interference device) flux meter and a 1.5 T-MRI system. The crystallographic phases of the prepared alloy samples were identified using X-ray diffraction. Sample cross-sections were observed using a metallurgical microscope. Furthermore, a thinning test was conducted to examine alloy workability. ResultsDual-phase Au-Pt alloys Au70Pt30 and Au67Pt33—the former heat-treated at 800 and 850 °C and the latter heat-treated at 900 °C—generated minimal artifacts when imaged in a 1.5 T-MRI system. Their volume magnetic susceptibility increased as the heat-treatment temperature decreased. The alloy surfaces were observed to be uniform. Moreover, the workability of the dual-phase alloy was considerably better than that of the single-phase alloy. ConclusionVolume magnetic susceptibility could be controlled by changing the composition and processing temperature of the Au-Pt alloys. Dual-phase Au-Pt alloys those do not generate magnetic susceptibility artifacts in MRI images and have good workability could be prepared. The alloys are expected to be used in the preparation of various implantable medical devices.

A novel sandwich-type electrochemical biosensor enabling sensitive detection of circulating tumor DNA

It is of great importance to accurately analyze circulating tumor DNA (ctDNA), for the reason that it serves as one of the particularly informative cancer biomarkers for disease diagnosis, therapy, and prognosis. However, sensitive detection of ctDNA remains a challenging task and the design of feasible sensing method plays a significant role in ctDNA analysis. In this work, a novel sandwich-type electrochemical biosensor was developed through a facile way for sensitive detection of ctDNA using nanocomposites (MWCNTs-PDA-Au-Pt) as signal probes’ (SPs) label (SPs-label) for signal amplification. The current response of the nanocomposites towards H2O2 reduction was used to quantitatively detect target DNA and distinguish base-mismatched DNA sequences. Characterizations reveal that Au-Pt alloy nanoparticles are uniformly dispersed on MWCNTs-PDA and the resultant MWCNTs-PDA-Au-Pt shows excellent response toward the reduction of H2O2, which could largely amplify the current response. Electrochemical analysis of electrode modification process confirms that the sandwich-type structure was successfully formed through step-wise reactions, including fixation of capture probes (CPs) on the surface of the screen-printed gold electrode, recognition between CPs and target DNA (T-DNA), hybridization between T-DNA and SPs. Under optimal experimental conditions, the proposed ctDNA biosensor exhibits a wide linear range from 1 × 10−15 to 1 × 10−8 mol/L with a detection limit as low as 5 × 10−16 mol/L (S/N = 3), unprecedented selectivity towards T-DNA and other base-mismatched DNAs (even for only single base-mismatched sequences), and superb long-term stability. This work demonstrates the sandwich-type scheme is a promising method for practical applications in clinical ctDNA diagnosis.

Selective catalytic oxidation of ammonia to nitrogen over zeolite-supported Pt-Au catalysts: Effects of alloy formation and acid sites

The selective catalytic oxidation of ammonia (NH3-SCO) to N2 and H2O at low temperatures was studied to remove low-concentration (50 ppm) NH3 from the air. A series of mordenite (M20)-supported Pt-Au alloy catalysts with different Pt:Au ratios were synthesized and tested in the NH3-SCO. The NH3 conversion and N2 selectivity both depended on the ratio of Pt to Au. The 0.52 wt% Pt84Au16/M20 catalyst showed the highest NH3 conversion (90% at 144 °C) even better than Pt100/M20, which was ascribed to the combination of electron-deficient Pt and electron-rich Au in the alloy nanoparticles. The effects of acid sites on the NH3-SCO were investigated by NaOH treatment of Pt84Au16/M20 catalyst. Results suggested that the acid sites could help to increase NH3 conversion, and that Brønsted acid sites are essential for the selective formation of N2.

Native Gold and Au-Pt Alloy in Eclogite Xenoliths of Kalyandurg KL-2 Kimberlite, Anantapur District, South India

Abstract The paper pertains to the studies carried out on the eclogitic xenoliths of KL-2 kimberlite of Kalyandurg kimberlite cluster in south India. Petrographic studies revealed bi-mineralic and kyanite-bearing eclogitic xenoliths in KL-2 kimberlite. The bi-mineralic and kyanite-bearing eclogites of Kalyandurg KL-2 kimberlite pipe show variation in modal proportion of garnet, omphacite, clinopyroxene and kyanite. The paper reports discovery of native gold grains and Au-Pt alloy in the kyanite-bearing eclogite xenoliths of KL-2 kimberlite. The flaky gold grains occurring in the matrix of kyanite-bearing eclogite are homogeneous and two grains of Au-Pt alloy with Au and Pt in the proportion of 9.8:1.2 are also present. This is the first report of gold and gold-platinum alloy specs from eclogitic xenoliths of Indian kimberlites.

Soft Tissue Interface with Various Kinds of Implant Abutment Materials.

Various materials, such as titanium, zirconia and platinum-gold (Pt-Au) alloy, have been utilized for dental implant trans-mucosal parts. However, biological understanding of soft tissue reaction toward these materials is limited. The aim of this study was to compare the response of cell lines and soft tissue to titanium, zirconia and Pt-Au substrata. The surface hydroxyl groups and protein adsorption capacities of the substrata were measured. Next, gingival epithelial-like cells (Sa3) and fibroblastic cells (NIH3T3) were cultured on the materials, and initial cell attachment was measured. Immuno-fluorescent staining of cell adhesion molecules and cytoskeletal proteins was also performed. In the rat model, experimental implants constructed from various materials were inserted into the maxillary tooth extraction socket and the soft tissue was examined histologically and immunohistochemically. No significant differences among the materials were observed regarding the amount of surface hydroxyl groups and protein adsorption capacity. Significantly fewer cells of Sa3 and NIH3T3 adhered to the Pt-Au alloy compared to the other materials. The expression of cell adhesion molecules and a well-developed cytoskeleton was observed, both Sa3 and NIH3T3 on each material. In an animal model, soft tissue with supracrestal tissue attachment was observed around each material. Laminin-5 immuno-reactivity was seen in epithelia on both titanium and zirconia, but only in the bottom of epithelia on Pt-Au alloy. In conclusion, both titanium and zirconia, but not Pt-Au alloy, displayed excellent cell adhesion properties.

Au core-PtAu alloy shell nanowires for formic acid electrolysis

Inefficient electrocatalysts and high-power consumption are two thorny problems for electrochemical hydrogen (H2) production from acidic water electrolysis. Herein we report the one-pot precise synthesis of ultrafine Au core-PtAu alloy shell nanowires (Au@PtxAu UFNWs). Among them, Au@Pt0.077Au UFNWs exhibit the best performance for formic acid oxidation reaction (FAOR) and hydrogen evolution reaction (HER), which only require applied potentials of 0.29 V and −22.6 mV to achieve a current density of 10 mA cm−2, respectively. The corresponding formic acid electrolyzer realizes the electrochemical H2 production at a voltage of only 0.51 V with 10 mA cm−2 current density. Density functional theory (DFT) calculations reveal that the Au-riched PtAu alloy structure can facilitates the direct oxidation pathway of FAOR and consequently elevates the FAOR activity of Au@Pt0.077Au UFNWs. This work provides meaningful insights into the electrochemical H2 production from both the construction of advanced bifunctional electrocatalysts and the replacement of OER.

A novel signal amplification label based on AuPt alloy nanoparticles supported by high-active carbon for the electrochemical detection of circulating tumor DNA

The detection of circulating tumor DNA (ctDNA) has increasingly received a great deal of attention considering its significance in cancer diagnosis. And the signal amplification plays an important role in the development of sensitive ctDNA biosensors. Herein, the nanocomposites (denoted as HAC-AuPt), integrating from high-active carbon (HAC) and AuPt alloy nanoparticles, were synthesized and subsequently used as a signal amplification label to fabricate a sandwich-type ctDNA electrochemical biosensor. Characterizations demonstrated that HAC presents uniform size distribution and AuPt alloy nanoparticles were successfully loaded on HAC. The current response could be amplified to a great extent by the resultant HAC-AuPt due to its excellent electrochemical property. The nanocomposites were further bounded with DNA signal probes (SPs) via Au-S or Pt-S assembly to form SPs-label. After the capture probes (CPs) were immobilized on the electrode surface, the target DNA (tDNA) and SPs-label were stepwise incubated on the CPs-modified electrode, thus forming a sandwich-type structure. By monitoring the catalytic signal of HAC-AuPt towards the reduction process of H2O2, this biosensor provided a wide linear range of 10−8 mol/L - 10−16 mol/L with a low detection limit of 3.6 × 10−17 mol/L (S/N = 3) for the detection of the tDNA. Furthermore, obvious differences in response signals among different DNAs were observed benefitting from the excellent selectivity of the biosensor. Besides, the long-term stability, reproducibility, and recovery rate were proved to be outstanding. These results indicate that the established biosensor holds a potential application in the clinical diagnosis of ctDNA.

An electrochemical aptasensor based on AuPt alloy nanoparticles for ultrasensitive detection of amyloid-β oligomers

Amyloid-β oligomer is an important biomarker and a potential therapeutic target of Alzheimer's disease in its early stage. Here, we combined superhydrophobic carbon fiber paper (CFP) with AuPt alloy nanoparticles to prepare a CFP/AuPt nanocomposite with larger specific surface area and hydrophobic surface. On this basis, we constructed an electrochemical aptasensor based on CFP/AuPt for the ultrasensitive detection of amyloid-β oligomers. The surface-coated AuPt nanoparticles greatly enhanced the electroactive area, and the hydrophobic surface increased the resisting nonspecific adsorption performance of sensor. A combination of these two features significantly improved the sensitivity and specificity of the sensor. This electrochemical aptasensor based on CFP/AuPt displayed a low detection limit of 0.16 pg/mL. This work shows a promising future in clinical diagnosis of Alzheimer's disease and provides a possible solution to electrochemical biosensors that are susceptible to interference in biological fluids.

Fully ordered L10-PtCoAu electrocatalyst derived from PtAu@CoO precursor with enhanced performance for oxygen reduction reaction

Alloying Pt with other transition metal is a promising method to accelerate the kinetics of oxygen reduction reaction (ORR). Herein, fully ordered Au-doped PtCo nanoparticles (L10-PtCoAu NPs) with a size of sub-4 nm are successfully synthesized by annealing the PtAu alloy which coated by CoO shell (PtAu@CoO) under H2 atmosphere. The artificially introduced vacancies during annealing process can accelerate the atomic diffusion, which is beneficial to the conversion from disordered alloy structure to intermetallic structure. And the addition of Au and Co atoms synergistically tunes the crystal and electronic structure of Pt. As a result, the electrochemical tests show that the mass activity of fully ordered L10-PtCoAu0.1/C catalyst is 1.08 A mgPt−1, which is 6 times higher than that of commercial Pt/C catalyst. Due to the protective effect of Au atoms and the stable ordered structure, the prepared L10-PtCoAu0.1/C catalyst show enhanced durability compared with commercial Pt/C after 20,000 potential cycles. This work provides a facile and scalable method to prepare small-sized Pt-based intermetallic alloy catalyst with improved activity and durability for ORR.