CoPt Alloy Research Articles

D‐Electrons of Platinum Alloy Steering CO Pathway for Low‐Charge Potential Li‐CO2 Batteries

AbstractAprotic Li‐CO2 batteries suffer from sluggish solid‐solid co‐oxidation kinetics of C and Li2CO3, requiring extremely high charging potentials and leading to serious side reactions and poor energy efficiency. Herein, we introduce a novel approach to address these challenges by modulating the reaction pathway with tailored Pt d‐electrons and develop an aprotic Li‐CO2 battery with CO and Li2CO3 as the main discharge products. Note that the gas‐solid co‐oxidation reaction between CO and Li2CO3 is both kinetically and thermodynamically more favorable. Consequently, the Li‐CO2 batteries with CoPt alloy‐supported on nitrogen‐doped carbon nanofiber (CoPt@NCNF) cathode exhibit a charging potential of 2.89 V at 50 μA cm−2, which is the lowest charging potential to date. Moreover, the CoPt@NCNF cathode also shows exceptional cycling stability (218 cycles at 50 μA cm−2) and high energy efficiency up to 74.6 %. Comprehensive experiments and theoretical calculations reveal that the lowered d‐band center of CoPt alloy effectively promotes CO desorption and inhibits further CO reduction to C. This work provides promising insights into developing efficient and CO‐selective Li‐CO2 batteries.

The role of surface substitution in the atomic disorder-to-order phase transition in multi-component core-shell structures.

Intermetallic phases with atomic ordering are highly active and stable in catalysts. However, understanding the atomistic mechanisms of disorder-to-order phase transition, particularly in multi-component systems, remains challenging. Here, we investigate the atom diffusion and phase transition within Pd@Pt-Co cubic nanoparticles during annealing, using in-situ electron microscopy and ex-situ atomic resolution element analysis. We reveal that initial outward diffusing Pd partially substitutes Pt, forming a (Pt, Pd)-Co ternary system in the surface region, enabling the phase transition at a low temperature of 400 °C, followed by shape-preserved inward propagation of the ordered phase. At higher temperatures, excessive interdiffusion across the interface changes the stoichiometric ratio, diminishing the atomic ordering, leading to obvious change in morphology. Calculations indicate that the Pd-substitute in (Pt, Pd)-Co system leads to a significantly lower phase transition temperature compared to that of Pt-Co alloy and thus a lower activation energy for atomic diffusion. These insights into atomistic behavior are crucial for future design of multi-component systems.

D-Electrons of Platinum Alloy Steering CO Pathway for Low-Charge Potential Li-CO2 Batteries.

Aprotic Li-CO2 batteries suffer from sluggish solid-solid co-oxidation kinetics of C and Li2CO3, requiring extremely high charging potentials and leading to serious side reactions and poor energy efficiency. Herein, we introduce a novel approach to address these challenges by modulating the reaction pathway with tailored Pt d-electrons and develop an aprotic Li-CO2 battery with CO and Li2CO3 as the main discharge products. Note that the gas-solid co-oxidation reaction between CO and Li2CO3 is both kinetically and thermodynamically more favorable. Consequently, the Li-CO2 batteries with CoPt alloy-supported on nitrogen-doped carbon nanofiber (CoPt@NCNF) cathode exhibit a charging potential of 2.89 V at 50 μA cm-2, which is the lowest charging potential to date. Moreover, the CoPt@NCNF cathode also shows exceptional cycling stability (218 cycles at 50 μA cm-2) and high energy efficiency up to 74.6 %. Comprehensive experiments and theoretical calculations reveal that the lowered d-band center of CoPt alloy effectively promotes CO desorption and inhibits further CO reduction to C. This work provides promising insights into developing efficient and CO-selective Li-CO2 batteries.

The key role of the second material's OER activity on MOR durability enhancement of the Pt alloys

Pt-based precious metal catalysts are generally regarded as the best catalyst materials for direct methanol fuel cells due to their high inherent methanol oxidation (MOR) activity. However, the commercial application of Pt catalyst is still facing with severe durability problem. The CO formed by the incomplete oxidation of methanol will occupy the Pt active site, hindering the further progress of the MOR reaction and causing the rapid attenuation of the activity. In this work, a MOR durability enhancement strategy that relation to the OER performance of the second materials M (M=Ni, Co, Fe and Cu) is reported. The precise electrochemical test results showed that the MOR durability of Pt-M alloy changes with the second material, which is related to the OER activity of M materials. The smaller the overpotential and tafel slopes of the M material, the better the MOR durability. Via M material screening, the Co element with the lowest OER overpotential among M promoted the Pt-Co alloy material with the highest MOR durability, resulting an excellent durability sustain 7000 times CV cycles with just 0.53 A mg−1Pt mass activity loss. According to the current generally accepted OER and MOR reaction mechanism, the association of MOR durability with OER activity is most likely derived from the same reaction step of M-OH formation, which played a key role on both reaction. This relationship between OER overpotential and MOR durability helps to screen the second material from the perspective of OER activity to improve the MOR durability of Pt catalysts, which is of great significance for the development of Pt-based CO-resistant MOR catalysts.

Cobalt Nitride-Implanted PtCo Intermetallic Nanocatalysts for Ultrahigh Fuel Cell Cathode Performance.

Stable and active oxygen reduction electrocatalysts are essential for practical fuel cells. Herein, we report a novel class of highly ordered platinum-cobalt (Pt-Co) alloys embedded with cobalt nitride. The intermetallic core-shell catalyst demonstrates an initial mass activity of 0.88 A mgPt-1 at 0.9 V with 71% retention after 30,000 potential cycles of an aggressive square-wave accelerated durability test and loses only 9% of its electrochemical surface area, far exceeding the US Department of Energy 2025 targets, with unprecedented stability and only a minimal voltage loss under practical fuel cell operating conditions. We discover that regulating the atomic ordering in the core results in an optimal lattice configuration that accelerates the oxygen reduction kinetics. The presence of cobalt nitride decorated within PtCo superlattices guarantees a larger barrier to Co dissolution, leading to the excellent endurance of the electrocatalysts. This work brings up a transformative structural engineering strategy for rationally designing high-performing Pt-based catalysts with a unique atomic configuration for broad practical uses in energy conversion technology.

Constructing 2D PtSe2/PtCo Heterojunctions by Partial Selenization for Enhanced Hydrogen Evolution

AbstractThe rational design and fabrication of 2D heterojuctions are proven a promising strategy for boosting the performance of electrocatalysts. Although 2D platinum diselenide (PtSe2) exhibits catalytic activity for hydrogen evolution reaction (HER), the catalytic performance is still unsatisfactory due to its inert basal plane, wide bandgap, and poor electron transfer ability. Herein, a new strategy is reported to construct PtSe2/PtCo heterojunctions by partial selenization of PtCo alloy for high‐efficiency HER electrocatalyst, which exhibits a low overpotential of 38 mV at the current density of 10 mA cm−2, a small Tafel slope of 22 mV dec−1, and a superior stability over 24 h and 1000 cycles. The outstanding HER activity of the catalyst arises from the strong electronic interactions between PtSe2 and PtCo in the heterojunctions, which induce electron transferring from PtSe2 to PtCo and the d‐band center down shifting, and thus optimize the H* adsorption/desorption. This work provides a novel strategy for constructing highly efficient heterostructure electrocatalysts, which facilitates the applications of hydrogen energy conversion.

Swift heavy ions induced transformations in the structural and magnetic properties of Co/Pt multilayer thin films for magnetic storage applications

The integration of CoPt nanoparticles into an insulating matrix has garnered significant attention in material science, nanotechnology, and electronic engineering, particularly for their potential use in magnetic storage media. Precise control over the size, shape, and ordering of these nanoparticles is crucial. This study investigates the impact of swift heavy ion irradiation (120 MeV Ag+9) with varying ion fluences (1 × 1013 and 3 × 1013 ions/cm2) on the structural and magnetic properties of sputter-deposited Co/Pt multilayer thin films on quartz substrates. X-ray diffraction (XRD) analysis of the pristine samples reveals the presence of an FCC-structured CoPt alloy. In contrast, films irradiated with a fluence of 1 × 1013 ions/cm2 exhibit superlattice peaks (001) and (110), indicative of L10-structured CoPt alloy, whereas films subjected to 3 × 1013 ions/cm2 retain the FCC structure. This suggests that a fluence of 1 × 1013 ions/cm2 promotes ordering, while 3 × 1013 ions/cm2 induces disordering. Selected area electron diffraction (SAED) patterns from TEM confirm these structural transitions, while SQUID magnetometry reveals an increase in coercivity at 1 × 1013 ions/cm2, followed by a reduction at 3 × 1013 ions/cm2, consistent with the observed structural changes. These results demonstrate that carefully controlled ion fluences can effectively tailor the structural and magnetic properties of Co/Pt multilayers, enhancing their suitability for advanced magnetic storage applications.

A review of ordered PtCo3 catalyst with higher oxygen reduction reaction activity in proton exchange membrane fuel cells

This review is devoted to the potential advantages of ordered alloy catalysts in proton exchange membrane fuel cells (PEMFCs), specifically focusing on the development of the low Pt content, high activity, and durability ordered PtCo3 catalyst. Due to the sluggish oxygen reduction reaction (ORR) kinetics and poor durability, the overall performance of the fuel cell is affected, and its application and promotion are limited. To address this issue, researchers have explored various synthetic strategies, such as element doping, morphology adjusting, structure controlling, ordering and support/metal interaction enhancement. This article extensively discussed the Pt related ORR catalysts and follows an in-depth analysis of ordered PtCo3. The introduction briefly discusses the direction of development of fuel cell catalysts and frontier progress, including theoretical mechanism, practical preparation, and Pt-containing electrode structures, etc. The subsequent chapter focuses on the Pt-Co catalyst, the evolution process of Pt alloy to Pt-Co alloy and the improvement scheme are introduced. The next chapter describes the properties of PtCo3. Although the ordered PtCo3 catalyst has a wide range of applicability due to low cost and high activity catalyst. However, besides the common agglomeration and sintering problems of Pt-Co alloy, its commercial application still faces unique problems of oversized crystal size, phase segregation, ordering transformation and transition metal dissolution. Therefore, in Chapter 4, this overview provides some possible improvement methods for three specific functions: crystal refinement, enhancing the effect of support and active substances, and anti-dissolution.

The Development of Uniform-Sized Pt-Based Binary Alloy Electrocatalysts for ORR in Polymer Electrolyte Fuel Cells

Developing a highly efficient and durable reduced platinum metal (PtM) alloy catalyst with high oxygen reduction reaction (ORR)activity for polymer electrolyte fuel cells (PEFCs) is of significant interest. In this study, platinum-iron (PtFe), platinum-nickel (PtNi), and platinum-cobalt (PtCo) alloys were prepared with an average diameter of ca. 3 nm, uniformly dispersed on a high surface area carbon. The ORR activity of the prepared PtM/C catalysts was investigated under both RDE and MEA conditions. The resulting PtM/C catalysts demonstrated improved I-V cell performance at low-current density (LCD) and high-current density (HCD) regions. These findings suggest that high ORR activity and enhanced durability can be achieved through the formation of uniform Pt skin with higher electrochemical surface area (ECSA).

A Tantalum-Rich Pt-Ta-Co Electrocatalyst for Polymer Electrolyte Fuel Cells

In polymer electrolyte fuel cells (PEFCs), Pt catalyst particle growth due to load fluctuation potential cycling, and oxidative corrosion of the carbon support due to start-stop potential cycling are important issues for cathode electrocatalysts affecting their durability. Here, we incorporate tantalum into the electrocatalyst to improve both the catalytic activity and durability. This is achieved via self-assembly of a nanocomposite electrocatalyst via dealloying to form Pt-Co alloy and TaOx support nanoparticles. Half-cell electrochemical measurements confirm that the catalytic activity and durability are significantly improved by the formation of this nanocomposite electrocatalyst.

Temperature-controlled shape transformation of PtCo alloy catalysts for enhanced ammonia oxidation in anion-exchange membrane direct ammonia fuel cells

Low-temperature anion-exchange membrane direct ammonia fuel cells (AEM-DAFCs) are emerging as attractive and environmentally friendly energy devices for small-scale transportation. However, challenges arise in the ammonia oxidation reaction (AOR) owing to the high activation energy required for direct ammonia modification and the issue of decreased activity in the AOR caused by the strong adsorption of ammonia and nitrogen species, necessitating solutions. In this study, we aimed to address the challenges related to the ammonia activation energy and ammonia adsorption capacity by alloying Pt and Co. Furthermore, during the fabrication of the PtCo catalysts, the synthesis process was controlled at different reaction temperatures to produce core–shell and hollow structures. In particular, the PtCo catalyst synthesized at 60 °C (PtCo-60), with a particle size of 7.65 nm in the hollow structure, exhibited the highest electrochemically active surface area among the PtCo catalysts produced (∼43.0 m2 g−1). This increase in the active surface area owing to structural changes was attributed to the increase in AOR activity. The onset potential of PtCo-60, adjusted for particle size and structure, was determined to be 0.454 V vs. RHE, with a mass activity of 128 A gPt−1, in cyclic voltammetry experiments using 1 M KOH +1 M NH4OH. Ultimately, in the AEM-DAFC unit cell test conducted at 80 °C, an output density of 11.33 mW cm−2 was achieved.

Electronegativity- induced cobalt-doped platinum hollow nanospheres with high CO tolerance for efficient methanol oxidation reaction

Although Platinum (Pt)-based alloys have garnered significant interest within the realm of direct methanol fuel cells (DMFCs), there still exists a notable dearth in the exploration of the catalytic behavior of the liquid fuels on well-defined active sites and unavoidable Pt poisoning because of the adsorbed CO species (COads). Here, we propose an electronegativity-induced electronic redistribution strategy to optimize the adsorption of crucial intermediates for the methanol oxidation reaction (MOR) by introducing the Co element to form the PtCo alloys. The optimal PtCo hollow nanospheres (HNSs) exhibit excellent high-quality activity of 3.27 A mgPt−1, which is 11.6 times and 13.1 times higher than that of Pt/C and pure Pt, respectively. The in-situ Fourier transform infrared reflection spectroscopy validates that electron redistribution could weak CO adsorption, and subsequently decrease the CO poisoning adjacent the Pt active sites. Theoretical simulations result show that the introduction of Co optimize surface electronic structure and reduce the d-band center of Pt, thus optimized the adsorption behavior of COads. This study not only employs a straightforward method for the preparation of Pt-based alloys but also delineates a pathway toward designing advanced active sites for MOR via electronegativity-induced electronic redistribution.

Understanding the Impact of Hydroxyls on Synthesizing the Bimetallic Alloy Pt3Co on Al2O3 for CO-PROX

The anchoring effect between surface hydroxyls (–OH) and metal species has been extensively utilized to enhance catalyst stability. Nevertheless, few studies have investigated the impact of alloying process involving different types of –OH species. In this research, we discovered that the formation of the alloy particles Pt3Co was significantly influenced by the presence of distinct –OH species on Al2O3. Intriguingly, those Pt3Co alloy particles exclusively formed on α-Al2O3 owing to the weak interaction between both Pt and Co species and the triply bridging hydroxyls (µ3-OH). In contrast, Pt and Co species were found to be separately dispersed on γ-Al2O3 because of the strong anchoring effect of terminal hydroxyls (µ1-OH), especially for Co atoms. Density functional theory (DFT) calculations highlighted the difference in adsorption energies of the two metals on different hydroxyl groups, providing a theoretical rationale for the influence of hydroxyl groups on alloy formation. The presence of Pt3Co alloy resulted in a fourfold increase in the specific catalytic rate of Pt3Co/α-Al2O3 in CO-PROX compared to Pt3Co/γ-Al2O3. Arguably for the first time, this study demonstrates the association between alloy formation and –OH groups, providing a unique perspective on the design of alloy catalysts.

Effect of Crystal Structure on Dealloying Behavior in PtCo Alloy and Its Impact on the Oxygen Reduction Reaction

The proton exchange membrane fuel cell (PEMFC) is considered ideal for power generation due to its high energy conversion efficiency, low operating temperature, and environmentally friendly features. However, the performance of PEMFC is limited by the slow oxygen reduction reaction (ORR) at the cathode, necessitating the use of catalysts such as Pt to enhance the reaction. The Pt catalyst, although effective, poses the challenge of high cost. Consequently, numerous studies have been undertaken to develop more cost-effective catalysts that can match the excellent activity of platinum while maintaining high stability. In particular, the development of alloy nano-catalysts has garnered attention, and promising results have been reported for enhancing catalyst performance through dealloying on the surface of the alloy catalyst. Alloy catalysts prepared by the dealloying method offer the advantage of improving performance by selectively dissolving less-noble metal surfaces and constructing a Pt-rich shell layer. In this study, we synthesized two PtCo alloy catalysts with distinct crystal structures: face-centered cubic (FCC) and face-centered tetragonal (FCT). To prevent particle growth during the transformation from FCC to FCT when subjected to high-temperature heat treatment for an extended duration, we employed the carbon shell encapsulation technique. Subsequently, the synthesized catalyst underwent acid treatment for dealloying. We investigated the variations in dealloying characteristics based on crystal structures and examined their impact on electrochemical performance. Various characterizations, including X-ray diffraction (XRD), High-Resolution Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM), Thermo-Gravimetric Analysis (TGA), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), were conducted to validate the structure of the synthesized PtCo alloy nano-catalyst. Half-cell and unit-cell experiments were carried out to verify electrochemical properties and performance, following the testing protocol suggested by the Department of Energy (DOE) in 2020. Finally, we explored the relationship between the dealloying feature of FCC and FCT and their impact on electrochemical activity and stability.

High-Pressure nitrogen assisted synthesis of Small-Sized, Carbon-Encapsulated PtCo alloy nanoparticles as highly stable oxygen reduction catalysts

The development of small-sized platinum-based alloy catalysts with exceptional stability is crucial for the advancement of oxygen reduction reactions in fuel cells. Herein, we present a synthesis approach for fabricating small-sized carbon-encapsulated PtCo/C catalysts facilitated by high-pressure nitrogen during annealing. Remarkably, the resulting PtCo/C catalyst exhibits outstanding performance, showcasing minimal degradation (4.7%) in mass activity after enduring 30,000 cycles owing to its robust carbon-coating architecture.

Efficient Orbitronic Terahertz Emission Based on CoPt Alloy.

Orbitronic devices operate by manipulating orbitally polarized currents. Recent studies have shown that these orbital currents can be excited by femtosecond laser pulses in a ferromagnet such as Ni and converted into ultrafast charge currents via orbital-to-charge conversion. However, the terahertz emission from orbitronic terahertz emitters based on Ni is still much weaker than that of the typical spintronic terahertz emitter. Here, this work reports a more efficient light-induced generation of orbital current from a CoPt alloy, and the terahertz emission from CoPt/Cu/MgO is comparable to that of benchmark spintronic terahertz emitters. By varying the composition of the CoPt alloy, the thickness of Cu, and the capping layer, this work confirms that THz emission primarily originates from the orbital accumulation generated within CoPt, propagating through Cu, followed by subsequent orbital-to-charge conversion due to the inverse orbital Rashba-Edelstein effect at the Cu/MgO interface. This study provides strong evidence for the efficient orbital current generation in CoPt alloy, paving the way for efficient orbital terahertz emitters.

Boosting Pt utilization via strategic Co Integration: Structural and mechanistic investigation of High-Performance Pt-Co alloy nanocatalysts for catalytic benzene combustion

Platinum (Pt)-based catalysts exhibit notable efficacy in reducing emissions of hazardous volatile organic compounds (VOCs), such as benzene. Nevertheless, the high cost and limited availability of Pt necessitate exploring reasonable strategies to optimize Pt utilization and enhance catalytic efficiency. Thus, pressing needs emerge to develop efficient Pt-based catalysts. This study investigates the catalytic combustion of benzene utilizing an antimony-doped tin oxide (ATO) supported platinum-cobalt (Pt-Co) alloy catalyst. The incorporation of cobalt into Pt nanoparticles leads to Co atoms occupying bulk sites in the Pt-Co alloy, elevating the surface exposure of Pt atoms and enriching Pt on the surface, thereby providing additional active sites for catalysis. Advanced characterization techniques provide critical insights into the morphology, size distribution, crystallinity and valence states of Pt upon strategic Co alloying. Pt-Co/ATO exhibits exceptional low-temperature activity, achieving 95 % benzene conversion at 170 °C, which is 30 °C lower than the 200 °C required for Pt/ATO. Pressure-dependent kinetic analysis reveals a Langmuir-Hinshelwood mechanism involving the co-adsorption of benzene and oxygen reactants on active Pt-Co alloy sites. This study contributes insights into tuning bimetallic alloy nanostructures to optimize noble metal utilization and catalytic performance for VOC abatement, establishing a foundation for advancing sustainable emissions control technology.

Engineering both intrinsic characteristic and local microenvironment of platinum sites toward highly efficient oxygen reduction reaction

The optimization of the adsorption of oxygen-containing intermediates on platinum (Pt) sites of Pt-based electrocatalysts is crucial for the oxygen reduction reaction process. Currently, a large amount of researches mainly focus on modifying the bulk structure of the electrocatalysts, however, the vital role of solvent effect on the phase interfaces is often overlooked. Here, we successfully developed an electrocatalyst in which the ordered PtCo alloy anchors on the cobalt (Co) single-atoms/clusters decorated support (Co1,nNC) and its surface is further optimized using hydrophobic ionic liquid (IL). Experimental studies and theoretical calculations indicate that compressive stress on Pt lattice contributed by intrinsic structure and the local hydrophobicity caused by IL on the surface can suppress the stabilization of *OH on Pt. This synergistic effect affords outstanding catalytic performance, exhibiting a half-wave potential (E1/2) of 0.916 V vs. RHE and a mass activity (MA) of 1350.3 mA mgPt−1 in 0.1 mol/L perchloric acid (0.1 M HClO4) electrolyte, much better than the commercial Pt/C (0.849 V vs. RHE and 145.5 mA mgPt−1 for E1/2 and MA, respectively). Moreover, the E1/2 of IL-PtCo/Co1,nNC only lost 5 mV after 10,000 cyclic voltammetry (CV) cycles due to a strong and synergistic contact of the intermetallic PtCo alloy with the Co1,nNC support and IL. This research provides an effective method for designing efficient electrocatalysts by combining intrinsic structure and surface modification.

Boosting oxygen reduction in acidic media through integration of Pt-Co alloy effect and strong interaction with carbon defects

Boosting oxygen reduction in acidic media through integration of Pt-Co alloy effect and strong interaction with carbon defects

Hydrogen Adsorption on Ordered and Disordered Pt-Fe and Pt-Co Alloys.

The bulk properties and surface chemical reactivity of compositionally disordered Pt-Fe and Pt-Co alloys in the fcc A1 phase have been investigated theoretically in comparison to the ordered alloys of the same compositions. The results are analyzed together with our previously reported findings for Pt-Ni. Nonlinear variation is observed in lattice constant, d band center, magnetic moment, and hydrogen adsorption energy across the composition range (0-100 atomic % of Pt, x Pt). The Pt 5d states are strongly perturbed by the 3d states of the base metals, leading to notable density of states above the Fermi level and residual magnetic moments at high x Pt. Surface reactivity in terms of average H adsorption energy varies continuously with composition between the monometallic Fe-Pt and Co-Pt limits, going through a maximum around x Pt = 0.5-0.75. Close inspection reveals a significant variation in site reactivity at x Pt < 0.75, particularly with disordered Pt-Fe alloys due in part to the inherent disparity in chemical reactivity between Fe and Pt. Furthermore, the strong interaction between Fe and Pt causes Pt-rich sites to be less reactive toward H than Pt-rich sites on disordered Pt-Ni alloy surfaces, despite less compressive strain caused. These results provide theoretical underpinnings for conceptualizing and understanding the performance of these Pt-base metal alloys in key catalytic applications and for efforts to tailor Pt-alloys as catalysts.