Platinum Alloys Research Articles

Synthesis of Pt-Rare Earth Metal Alloys and Their Applications.

The alloying of platinum (Pt) with rare earth (RE) metals has emerged as a highly promising strategy for enhancing both the activity and stability of catalysts. Consequently, the development of methods for the controlled synthesis of Pt-RE alloys has received growing attention. This review comprehensively explores diverse synthesis methodologies for Pt-RE alloys, including physical metallurgy method, chemical reduction method, electrodeposition method, and dealloying method. Additionally, this review summaries the applications of Pt-RE alloys in various fields. By providing a critical analysis of existing literature and highlighting key challenges and future directions, this review aims to offer valuable insights and serve as a springboard for further advancements in the controlled synthesis and diverse applications of Pt-RE alloys.

Improvement of technology for the production of jewelry wire from platinum alloys

Improvement of technology for the production of jewelry wire from platinum alloys

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.

Diffusion bonding of dissimilar materials for space applications via hot isostatic pressing

In this work, hot isostatic pressing diffusion bonding (HIP DB) behaviour of dissimilar materials such as niobium (Nb), platinum (Pt) and titanium alloy (Ti6Al4V) were assessed, especially for thrust combustion chamber used in rocket engines. In particular, the development of an oxidation-resistant layer for pure Nb using Pt was addressed. The diffusion layer analysed by scanning electron microscopy (SEM) shows a successful reaction between pure Nb and Pt with the generation of a 20 µm thick, fully dense reaction layer. Furthermore, the DB of pure Nb with Ti6Al4V was also investigated to evaluate the possibility of joining Nb and Ti6Al4V dissimilar materials for space applications. HIP-DBtrials presented in this work demonstrate the possibility of replacing the conventional R-512 E di-silicide coating with a Pt layer and the fusion welding of Nb and Ti6Al4V with solid state HIP-DBjoining to obtain a defect-free joint with a desirable microstructure at or near the interface.

Hydrogen Spillover Mechanism at the Metal–Metal Interface in Electrocatalytic Hydrogenation

AbstractHydrogen spillover in metal‐supported catalysts can largely enhance electrocatalytic hydrogenation performance and reduce energy consumption. However, its fundamental mechanism, especially at the metal–metal interface, remains further explored, impeding relevant catalyst design. Here, we theoretically profile that a large free energy difference in hydrogen adsorption on two different metals (|ΔGH‐metal(i)−ΔGH‐metal(ii)|) induces a high kinetic barrier to hydrogen spillover between the metals. Minimizing the difference in their d‐band centers (Δϵd) should reduce |ΔGH‐metal(i)−ΔGH‐metal(ii)|, lowering the kinetic barrier to hydrogen spillover for improved electrocatalytic hydrogenation. We demonstrated this concept using copper‐supported ruthenium–platinum alloys with the smallest Δϵd, which delivered record high electrocatalytic nitrate hydrogenation performance, with ammonia production rate of 3.45±0.12 mmol h−1 cm−2 and Faraday efficiency of 99.8±0.2 %, at low energy consumption of 21.4 kWh kgamm−1. Using these catalysts, we further achieve continuous ammonia and formic acid production with a record high‐profit space.

High vacancy formation energy boosts the stability of structurally ordered PtMg in hydrogen fuel cells

Alloys of platinum with alkaline earth metals promise to be active and highly stable for fuel cell applications, yet their synthesis in nanoparticles remains a challenge due to their high negative reduction potentials. Herein, we report a strategy that overcomes this challenge by preparing platinum-magnesium (PtMg) alloy nanoparticles in the solution phase. The PtMg nanoparticles exhibit a distinctive structure with a structurally ordered intermetallic core and a Pt-rich shell. The PtMg/C as a cathode catalyst in a hydrogen-oxygen fuel cell exhibits a mass activity of 0.50 A mgPt−1 at 0.9 V with a marginal decrease to 0.48 A mgPt−1 after 30,000 cycles, exceeding the US Department of Energy 2025 beginning-of-life and end-of-life mass activity targets, respectively. Theoretical studies show that the activity stems from a combination of ligand and strain effects between the intermetallic core and the Pt-rich shell, while the stability originates from the high vacancy formation energy of Mg in the alloy.

Origin of Stability and Activity Enhancements in Pt-Based Oxygen Reduction Reaction Catalysts Via Defect-Mediated Dopant Adsorption

Platinum alloys are highly efficient electrocatalysts for the oxygen reduction reaction (ORR) in acidic conditions. However, these alloys are susceptible to metal loss through leaching and degradation, leading to reduced catalyst stability and activity. Recently, it has been shown that doping with oxophilic elements can significantly alleviate these problems, with a prominent example being Mo-doped Pt alloys. Here, to achieve atomic scale understanding of the exceptional activity and stability of these alloys, we present a detailed density functional theory description of the dopants’ structures and impact on electrocatalyst properties. Beginning with the Mo/Pt system, we demonstrate that Mo can be stabilized in the form of low-dimensional oxyhydroxide moieties on Pt defects. The resulting structures enhance stability and activity via distinct physical processes, with the Mo moieties both directly inhibiting Pt dissolution at defects and indirectly enhancing ORR activity by generation of strain fields on surrounding Pt terraces. We then generalize these analyses to other metal dopant elements, and we demonstrate that similar low-dimensional oxyhydroxide structures control the electrocatalytic properties through an intricate interplay of the structures’ acid stability, intrinsic activity for the ORR, and ability to induce ORR-promoting strain fields on Pt.Reference:Sawant, K., Zeng, Z. & Greeley, J., Angew. Chem., Int. Ed., 10.1002/anie.202312747

Investigating mechanical deformation's role in cochlear implant durability.

Platinum and platinum-based alloys are used as the electrode material in cochlear implants because of the biocompatibility and the favorable electrochemical properties. Still, these implants can fail over time. The present study was conducted to shed light on the effects of microstructure on the electrochemical degradation of platinum. After three days of stimulation with a square wave signal, corrosive attack appeared on the platinum surface. The influence of mechanical deformation, in particular rolling, on the corrosion resistance of platinum was also prominent. The cyclic voltammetry showed a clear dependence on the electrolyte used, which was interpreted as an influence of the buffer in the artificial perilymph used. In addition, the polarization curves showed a shift with grain size that was not expected. This could be attributed to the defects present on the surface. These findings are crucial for the manufacture of cochlear implants to ensure their long-term functionality.

An Extensive Review of MR Sensors with Design and Characteristic Evaluation of Three-layered TMR Sensor

Abstract: The reliability and efficacy of sensor-based automated systems have improved due to the proliferation of electric vehicles, renewable sources, and integrated systems in power industries extensively. This has been accomplished by increasing the power density and decreasing the volume of the system. Background: Mathematical estimation and comparative analysis of the physical factors result in massive usage of operational matrices measured using sensors. Magnetic field sensors, used in industries and biomedical applications, have a high level of precision in the evaluation of measurements. In order to extract the measured parameters such as sensitivity, accuracy, operating cost, the linear range of operation, and power utilisation, these sensors adhere to the physical constraints during their nominal working conditions. The characteristics of the aforementioned sensors are enumerated in detail in this article. Objective: This objective is highly focused on providing a comprehensive overview of classification and the properties of Hall-Effect, anisotropic magnetoresistive (AMR), giant magnetoresistive (GMR), and tunnelling magnetoresistive (TMR) sensors. The dissertation on its properties concludes that TMR is more reliable and sensitive in variable operating conditions. Methods: The methods for selecting the sensors for an application are confined to voltage fluctuations and sensitivity. A three-layered TMR sensor with two magnetic layers and an insulator in between is proposed as a significant advancement compared to the literature. The micromagnetic simulation is carried out at room temperature for a three-layered TMR made up of neodymium alloy, magnesium oxide, and cobalt platinum alloy. Conclusion: Based on the studies executed, it is determined that TMR is more sensitive than both conventional and MR sensors. The proposed schematic claims that the higher free layer thickness offers maximum sensitivity with 77% negative magnetoresistance. The reduced coercivity of 1.9Oe is achieved in this combination at a specified temperature range.

Gold Nanobipyramids Coated with Silver–Platinum Alloy Shells for Plasmonically Enhanced Photocatalytic Degradation of Methyl Orange

Gold Nanobipyramids Coated with Silver–Platinum Alloy Shells for Plasmonically Enhanced Photocatalytic Degradation of Methyl Orange

Tailoring Zirconia Supported Intermetallic Platinum Alloy via Reactive Metal‐Support Interactions for High‐Performing Fuel Cells

AbstractDeveloping efficient and anti‐corrosive oxygen reduction reaction (ORR) catalysts is of great importance for the applications of proton exchange membrane fuel cells (PEMFCs). Herein, we report a novel approach to prepare metal oxides supported intermetallic Pt alloy nanoparticles (NPs) via the reactive metal‐support interaction (RMSI) as ORR catalysts, using Ni‐doped cubic ZrO2 (Ni/ZrO2) supported L10−PtNi NPs as a proof of concept. Benefiting from the Ni migration during RMSI, the oxygen vacancy concentrations in the support are increased, leading to an electron enrichment of Pt. The optimal L10−PtNi−Ni/ZrO2−RMSI catalyst achieves remarkably low mass activity (MA) loss (17.8 %) after 400,000 accelerated durability test cycles in a half‐cell and exceptional PEMFC performance (MA=0.76 A mgPt−1 at 0.9 V, peak power density=1.52/0.92 W cm−2 in H2−O2/−air, and 18.4 % MA decay after 30,000 cycles), representing the best reported Pt‐based ORR catalysts without carbon supports. Density functional theory (DFT) calculations reveal that L10−PtNi−Ni/ZrO2−RMSI requires a lower energetic barrier for ORR than L10−PtNi−Ni/ZrO2 (direct loading), which is ascribed to a decreased Bader charge transfer between Pt and *OH, and the improved stability of L10−PtNi−Ni/ZrO2−RMSI compared to L10−PtNi−C can be contributed to the increased adhesion energy and Ni vacancy formation energy within the PtNi alloy.

Tailoring Zirconia Supported Intermetallic Platinum Alloy via Reactive Metal-Support Interactions for High-Performing Fuel Cells.

Developing efficient and anti-corrosive oxygen reduction reaction (ORR) catalysts is of great importance for the applications of proton exchange membrane fuel cells (PEMFCs). Herein, we report a novel approach to prepare metal oxides supported intermetallic Pt alloy nanoparticles (NPs) via the reactive metal-support interaction (RMSI) as ORR catalysts, using Ni-doped cubic ZrO2 (Ni/ZrO2) supported L10-PtNi NPs as a proof of concept. Benefiting from the Ni migration during RMSI, the oxygen vacancy concentrations in the support are increased, leading to an electron enrichment of Pt. The optimal L10-PtNi-Ni/ZrO2-RMSI catalyst achieves remarkably low mass activity (MA) loss (17.8 %) after 400,000 accelerated durability test cycles in a half-cell and exceptional PEMFC performance (MA=0.76 A mgPt -1 at 0.9 V, peak power density=1.52/0.92 W cm-2 in H2-O2/-air, and 18.4 % MA decay after 30,000 cycles), representing the best reported Pt-based ORR catalysts without carbon supports. Density functional theory (DFT) calculations reveal that L10-PtNi-Ni/ZrO2-RMSI requires a lower energetic barrier for ORR than L10-PtNi-Ni/ZrO2 (direct loading), which is ascribed to a decreased Bader charge transfer between Pt and *OH, and the improved stability of L10-PtNi-Ni/ZrO2-RMSI compared to L10-PtNi-C can be contributed to the increased adhesion energy and Ni vacancy formation energy within the PtNi alloy.

Microstructure, mechanical and electrical properties of a novel low-cost high-strength Pt-xAu-5Ni alloy

The present study designed and prepared a novel platinum alloy system Pt-xAu-5Ni (x = 0, 2, 5, wt.%) with high strength and good electrical resistivity. The mechanical, electrical properties and related microstructure during the cold deformation and subsequent aging process were investigated. The cold-deformed Pt–5Ni alloy obtained the yield strength of 581 MPa, the ultimate tensile strength of 828 MPa, the hardness of 283 HV, and the electrical resistivity of 23.9 μΩ⋅cm. The subsequent aging process and the Au addition into Pt–5Ni alloy were found to both enhance the mechanical properties. Therefore, with the dual strengthening effect of the subsequent aging and the Au addition, Pt–5Au–5Ni alloy achieved the high yield strength of 889 MPa, the high ultimate tensile strength of 1117 MPa, the high hardness of 361 HV with the electrical resistivity of 26.7 μΩ⋅cm. The precipitation of L12-type Pt3Ni nanoparticles and L11-type CSRO dominated the age-strengthening behavior of Pt–2Au–5Ni and Pt–5Au–5Ni alloys after cold deformation. The Au addition refined the grains via the experimental observations, and predictably favored the L12-type Pt3Ni nanoprecipitation based on the thermodynamical calculations, thus the Au addition effectively strengthened Pt–5Ni alloy. This study provides a novel platinum alloy system with excellent mechanical and electrical properties, which has potential application in the electrical contact field.

Challenges in quantifying Pt concentrations in Pd alloys by using secondary ion mass spectrometry: Strong grain orientation effects

Palladium–platinum alloys were analysed by dynamic secondary ion mass spectrometry (SIMS) to investigate grain orientation effects that gave differences of up to 400% in the Pt/Pd count rate ratios, even within the same grain upon small rotations of a Pd sample with 1 wt% Pt. The sample had been homogenized by annealing, and the homogeneity was confirmed by X‐ray analysis in scanning electron microscopy (SEM). Grain orientations were determined by electron backscatter diffraction (EBSD). Crater depths were measured by white light interferometry (WLI). SEM images from the bottom of SIMS craters made in the same grain after small rotations around the sample surface normally showed different patterns of microfaceting for some rotation angles, probably exposing low‐index crystallographic planes. A complete understanding of the observed grain orientation effect is still lacking. However, factors such as ion mass, sputter rate, ion channelling, ion focusing, preferential sputtering, surface height, crater microfaceting and/or angle‐dependent sputtering seem to play a role. For these Pd–Pt alloys, the strong grain orientation effect adds another level of complexity when attempting to quantify concentrations and obtain depth profiles by SIMS. Without proper sampling and/or averaging, one could reach very wrong conclusions when comparing results from different samples.

Synergy of porous network nanostructuring and nonmetallic phosphorus alloying for efficient oxygen reduction of platinum

Alloying of nanostructured platinum (Pt)-based electrocatalysts can significantly improve their electrocatalytic performance for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, there are few studies of nonmetals alloyed Pt-based nanostructures for ORR electrocatalysis. Herein, we present a synergy of porous network nanostructuring and nonmetallic phosphorus (P) alloying to engineer the high-performance P-alloyed Pt nanospheres (P-PtNSs) for efficient ORR electrocatalysis. This characteristic porous network nanostructure is crafted through surfactant soft-templates induced confinement growth, and P-alloying is realized by a post-phosphating method. The introduction of P into Pt lattice can not only regulate electronic and geometric structure but also augment electrocatalytic active sites through the contribution of Pt-P bonds. The resultant P-PtNSs/C catalyst shows mass activity and specific activity at 0.90 V, surpassing those of commercial Pt/C catalyst by factors of 2.7 and 5.8, respectively, while also exhibiting superior stability. More importantly, the H2-O2 PEMFC with a P-PtNSs/C cathode exhibits higher current and power densities than one with Pt/C throughout the entire evaluation process, achieving a peak power density of 1.28 W cm−2 at a low Pt loading of 0.1 mgPt cm−2. This study will provide valuable insights into the nonmetals alloying and nanostructuring of Pt-based ORR electrocatalysts.

Platinum Alloys for Methanol Oxidation Electrocatalysis: Reaction Mechanism and Rational Design of Catalysts with Exceptional Activity and Stability

Direct methanol fuel cells have emerged as highly promising energy conversion devices in the past few decades. However, some challenges, such as carbon monoxide (CO) poisoning and unsatisfactory long-term stability, remain for platinum (Pt) as a methanol oxidation reaction (MOR) catalyst. This review covers recent advances in Pt alloy MOR catalysts and provides some insights. This review presents MOR catalytic mechanisms based on CO or non-CO pathways. Typical dimension-based designs of MOR catalysts, such as anisotropic nanowires, metallene, nanoframes, and corresponding rationales for performance enhancements, are introduced. More importantly, some key tuning strategies are elaborated, including intermetallic compound synthesis, interface engineering, and surface facet engineering. High-entropy alloys as an intriguing class of MOR catalysts with favorable prospects are also discussed. Finally, future directions and opportunities are outlined.

Rare Earth Evoked Subsurface Oxygen Species in Platinum Alloy Catalysts Enable Durable Fuel Cells.

Alleviating the degradation issue of Pt based alloy catalysts, thereby simultaneously achieving high mass activity and high durability in proton exchange membrane fuel cells (PEMFCs), is highly challenging. Herein, we provide a new paradigm to address this issue via delaying the place exchange between adsorbed oxygen species and surface Pt atoms, thereby inhibiting Pt dissolution, through introducing rare earth bonded subsurface oxygen atoms. We have succeeded in introducing Gd-O dipoles into Pt3 Ni via a high temperature entropy-driven process, with direct spectral evidence attained from both soft and hard X-ray absorption spectroscopies. The higher rated power of 0.93 W cm-2 and superior current density of 562.2 mA cm-2 at 0.8 V than DOE target for heavy-duty vehicles in H2 -air mode suggest the great potential of Gd-O-Pt3 Ni towards practical application in heavy-duty transportation. Moreover, the mass activity retention (1.04 A mgPt -1 ) after 40 k cycles accelerated durability tests is even 2.4 times of the initial mass activity goal for DOE 2025 (0.44 A mgPt -1 ), due to the weakened Pt-Oads bond interaction and the delayed place exchange process, via repulsive forces between surface O atoms and those in the sublayer. This work addresses the critical roadblocks to the widespread adoption of PEMFCs.

Silver and Silver Alloy on Carbon-supported Catalysts for Cathodes in Proton Exchange Membrane Fuel Cell and Direct Ethanol Fuel Cell

This research was focused on the synthesis of 20 %wt silver, silver platinum alloy, and silver-copper alloy catalysts on carbon Vulcan XC-72 supporter for proton exchange membrane fuel cell (PEMFC) and direct ethanol fuel cell (DEFC) cathode using sodium borohydride method. Herein, the ratio of silver and platinum or copper sources was 1:1 by weight. The obtained catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the electro-activity performance was investigated on single-cell testing. XRD and TEM results confirmed the catalytic products of the Ag metal, AgPt alloy, and silver copper oxide (AgxCu2-xO). Therefore, the particle size of the catalytic 20 %wt AgPt/C was observed in the smallest size of about 4.71±1.03 nm. The catalyst was selected for PEMFC and DEFC cathode testing. It showed high power density of 14.68 and 1.26 W/cm2.g(M), respectively.

Numerical Simulations for in-Plane Distribution of Platinum Degradation in Dynamic Operating Conditions of Polymer Electrolyte Membrane Fuel Cells

Predicting degradation of polymer electrolyte membrane fuel cells (PEMFCs) is an important issue from the viewpoint of durability and cost. In fact, in technical roadmaps regarding fuel cell of each country, high targets of durability and performance are set for transport applications especially for heavy duty vehicles. One of important degradation process takes place in catalyst layer. PEMFC catalysts are typically platinum or platinum alloys and consist of nanoparticles to increase the electrochemically active surface area (ECSA). However, these particles are not stable in dynamic operating conditions of the transport applications. A typical degradation mechanism of the catalyst is the electrochemical Ostwald ripening mechanism, and it is known that the platinum particle size distribution shifts to larger particle diameter, resulting in lower ECSA and lower performance. Therefore, predicting platinum catalyst degradation is important to enhance durability of the products.Various numerical models for catalyst degradation of PEMFC have been proposed and used to explore degradation mechanisms. Many of these are zero or one-dimensional models, but factors that affect catalyst degradation, such as temperature, potential, and humidity, have non-uniform distributions in the active area of large-size (several hundred cm2) cells. Furthermore, these factors change unsteadily due to the dynamic operating conditions. In order to predict the degradation of cells, it is necessary to analyze the dynamic behavior of large-area cells, but there are few spatially resolved catalyst degradation predictions [1].In this analysis, transient analysis of a large-area cell for a dynamic operating conditions is performed to predict in-plane distribution of catalyst degradation. Furthermore, we will analyze changes in the power generation performance of the cells when these degradations progress. A three-dimensional numerical simulation model based on our original methodology [2] was used as the performance prediction model for the PEMFC. Catalyst degradation considers the mechanisms of platinum dissolution, oxidation, and platinum oxide dissolution [3]. The in-plane distribution of platinum degradation is predicted from the time-series results of in-plane distributions of temperature, potential, humidity, etc., obtained by the performance prediction model. The performance of the PEMFC at the time of progressive degradation is analyzed by reflecting the effect of ECSA decrease due to platinum degradation in the performance prediction model. Although this method considers only a part of the catalyst degradation process, a path is presented to analyze the distribution of catalyst degradation under dynamic operating conditions in large-area cells.

Origin of Stability and Activity Enhancements in Pt-based Oxygen Reduction Reaction Catalysts via Defect-Mediated Dopant Adsorption.

Platinum alloys are highly efficient electrocatalysts for the oxygen reduction reaction (ORR) in acidic conditions. However, these alloys are susceptible to metal loss through leaching and degradation, leading to reduced catalyst stability and activity. Recently, it has been shown that doping with oxophilic elements can significantly alleviate these problems, with a prominent example being Mo-doped Pt alloys. Here, to achieve atomic scale understanding of the exceptional activity and stability of these alloys, we present a detailed density functional theory description of the dopants' structures and impact on electrocatalyst properties. Beginning with the Mo/Pt system, we demonstrate that Mo can be stabilized in the form of low-dimensional oxyhydroxide moieties on Pt defects. The resulting structures enhance stability and activity via distinct physical processes, with the Mo moieties both directly inhibiting Pt dissolution at defects and indirectly enhancing ORR activity by generation of strain fields on surrounding Pt terraces. We then generalize these analyses to other metal dopant elements, and we demonstrate that similar low-dimensional oxyhydroxide structures control the electrocatalytic properties through an intricate interplay of the structures' acid stability, intrinsic activity for the ORR, and ability to induce ORR-promoting strain fields on Pt.