Bimetallic PtCo Research Articles

Boosting the Electrolysis of Monosaccharide-Based Streams in an Anion-Exchange Membrane Cell.

A systematic study on the electrochemical reforming of monosaccharides (fructose, glucose, and xylose) using Pt-based anodic electrocatalysts is here presented for the first time to completely optimize the anodic catalyst and electrolyzer operating conditions. First, the electro-oxidation of each molecule was studied using a monometallic (Pt) and two bimetallic (PtNi and PtCo) anodic electrocatalysts supported on graphene nanoplatelets (GNPs). Tests in a three-electrode cell showed superior electrochemical activity and durability of PtNi/GNPs, especially at potentials higher than 1.2 V vs RHE, with the highest electrocatalytic activity in d-xylose electro-oxidation. Then, monometallic (Pt and Ni) and bimetallic electrocatalysts with different Pt:Ni mass ratios (1:1 and 2:1) were studied for d-xylose electro-oxidation, with the 2:1 mass ratio presenting the best results. This electrocatalyst was selected as the most suitable for scale-up to an anion-exchange membrane electrolyzer, where the optimal operating potential was determined. Additionally, stable operating conditions of the electrolyzer were achieved by cyclic H2 production and cathodic regeneration polarization steps. This led to suitable and reproducible H2 production rates throughout the production cycles for renewable hydrogen production from biomass-derived streams.

Optimized Pt-Co Alloy Nanoparticles for Reverse Water-Gas Shift Activation of CO2.

Different Co contents were used to tune bimetallic Pt-Co nanoparticles with a diameter of 8 nm, resulting in Pt:Co ratios of 3.54, 1.51, and 0.96. These nanoparticles were then applied to the MCF-17 mesoporous silica support. The synthesized materials were characterized with HR-TEM, HAADF-TEM, EDX, XRD, BET, ICP-MS, in situ DRIFTS, and quasi in situ XPS techniques. The catalysts were tested in a thermally induced reverse water-gas shift reaction (CO2:H2 = 1:4) at atmospheric pressure in the 200-700 °C temperature range. All bimetallic Pt-Co particles outperformed the pure Pt benchmark catalyst. The nanoparticles with a Pt:Co ratio of 1.51 exhibited 2.6 times higher activity and increased CO selectivity by 4% at 500 °C. Experiments proved that the electron accumulation and alloying effect on the Pt-Co particles are stronger with higher Co ratios. The production of CO followed the formate reaction pathway on all catalysts due to the face-centered-cubic structure, which is similar to the Pt benchmark. It is concluded that the enhanced properties of Co culminate at a Pt:Co ratio of 1.51 because decreasing the ratio to 0.96 results in lower activity despite having more Co atoms available for the electronic interaction, resulting in the lack of electron-rich Pt sites.

Morphology engineering of self-assembled bimetallic PtCo alloy nanofoams as efficient multifunctional electrocatalysts for oxygen reduction and alcohol oxidation

The exploration of high properties of electrocatalysts is imperative for the commercialization application of fuel cells. Enhancing the catalytic activity and stability of Pt-based catalysts can be achieved by rationally designing their morphology and composition. Here, we synthesized self-assembled PtCo alloy nanofoams (ANs) catalysts with controllable surface composition and porous network. The experimental results show that prepared PtxCo1-ANs catalysts display excellent electrochemical performance in oxygen reduction reaction (ORR), methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR). Interestingly, the mass activities of Pt2Co1-ANs with optimized surface composition for ORR, MOR, and EOR are 6.41, 6.64, and 7.71-fold higher than commercial Pt/C catalysts, respectively. Meantime, it also maintains high electrocatalytic durability in ORR, MOR, and EOR. Such results ascribe to the modified surface composition, optimized electronic structure, and porous interconnected nanofoam structure. These findings provide valuable insights into the design of highly active and durable multifunctional electrocatalysts with controllable shapes and composition.

Interfacial synergy between Pt3Co nanoparticles and CoO for efficient ammonia borane hydrolysis

Ammonia borane (AB, NH3BH3) with the high H2 content has been regarded as a promising material for chemical hydrogen storage. AB can hydrolyze to release H2 under the catalysis of noble-metal catalysts with high activity, but the high cost of noble-metals and their poor long-term stability prohibit the large-scale applications. Developing more cost-effective and stable catalysts by introducing cheap transition metal elements has been a promising strategy. Herein, we adopted a step-by-step precipitation method to synthesize bimetallic Pt-Co catalysts supported on rutile TiO2, which show significantly improved performance in AB hydrolysis reaction. The optimized 0.9Pt3.5Co/TiO2 catalyst (with the Pt and Co loadings of 0.9 and 3.5 wt%, respectively) exhibits an extremely high H2 generation rate, showing a turnover frequency value of 2163 molH2 molPt-1 min−1 at 298 K, 9 times higher than that of 0.9Pt/TiO2 catalyst and superior to those of most of the reported Pt-based catalysts. Structure characterizations and theoretical calculations reveal that the promoted AB hydrolysis performance arises from the interfacial synergistic effect between the supported Pt3Co alloy and cobalt oxide CoO, which accelerates the B-H bond cleavage and water activation, respectively. The excellent AB hydrolysis performance of the Pt-Co catalysts indicates the great prospects of alloy-oxide interfaces in the field of liquid phase chemical hydrogen storage.

Evaluation of Pt-Co Nano-Catalyzed Membranes for Polymer Electrolyte Membrane Fuel Cell Applications

The membrane electrode assembly (MEA) encompassing the polymer electrolyte membrane (PEM) and catalyst layers are the key components in Polymer Electrolyte Membrane Fuel Cells (PEMFCs). The cost of the PEMFC stacks has been limiting its commercialization due to the inflated price of conventional platinum (Pt)-based catalysts. As a consequence, the authors of this paper focus on developing novel bi-metallic (Pt-Co) nano-alloy-catalyzed MEAs using the non-equilibrium impregnation–reduction (NEIR) approach with an aim to reduce the Pt content, and hence, the cost. Herein, the MEAs are fabricated on a Nafion® membrane with a 0.4 mgPtcm−2 Pt:Co electrocatalyst loading at three atomic ratios, viz., 90:10, 70:30, and 50:50. The High Resolution-Scanning Electron Microscopic (HR-SEM) characterization of the MEAs show a favorable surface morphology with a uniform distribution of Pt-Co alloy particles with an average size of about 15–25 µm. Under standard fuel cell test conditions, an MEA with a 50:50 atomic ratio of Pt:Co exhibited a peak power density of 0.879 Wcm−2 for H2/O2 and 0.727 Wcm−2 for H2/air systems. The X-ray diffractometry (XRD), SEM, EDX, Cyclic Voltammetry (CV), impedance, and polarization studies validate that Pt:Co can be a potential affordable alternative to high-cost Pt. Additionally, a high degree of stability in the fuel cell performance was also demonstrated with Pt50:Co50.

Dealuminated Beta stabilized bimetallic PtCo nanoparticles for oxidative dehydrogenation of propane with CO2

Oxidative dehydrogenation of propane in the presence of carbon dioxide (CO2) effectively promotes the utilization of alkanes and CO2 to produce high value-added olefins and carbon monoxide products. In this work, bimetallic PtCo nanoparticles with diameter of 1–2.5 nm loaded on dealuminated nano-Beta zeolite were successfully prepared for propane oxidative dehydrogenation with CO2. The silanol groups formed after dealuminization of nano-Beta zeolite acted as the anchoring sites to enhance the dispersion of PtCo nanoparticles, and the introduction of Co further promoted the uniform distribution of Pt, resulting in smaller bimetallic PtCo nanoparticles. By optimizing the Pt/Co ratio, the conversion of propane and CO2 at 550 °C was as high as 51.8 % and 30.6 %, respectively. The dealuminized Beta supported PtCo nanoparticles exhibited high stability during the reaction, and there was no obvious aggregation of PtCo nanoparticles after 6 h on stream. In this study, the highly efficient catalyst prepared by impregnation method using modified commercial zeolite as the carrier is suitable for large-scale production and shows great practical prospect in the application of propane oxidative dehydrogenation with CO2.

Alloying with Mn Enhances the Activity and Durability of the CoPt Catalyst toward the Methanol Oxidation Reaction.

To improve the catalytic performance and durability of Pt catalysts used for the methanol oxidation reaction (MOR) in direct methanol fuel cells (DMFCs), alloying of Pt with other transition metals such as Ru, Co, Ni, and Fe is considered an effective approach. Despite the significant progress made in the preparation of bimetallic alloys and their utilization for MOR, improving the activity and durability of the catalysts to make them commercially viable remains a stiff challenge. In this work, trimetallic Pt100-x(MnCo)x (16 < x < 41) catalysts were successfully synthesized via borohydride reduction followed by hydrothermal treatment at 150 °C. The electrocatalytic performance of the synthesized trimetallic Pt100-x(MnCo)x (16 < x < 41) catalysts toward MOR was studied using cyclic voltammetry and chronoamperometry. The results affirm that all Pt100-x(MnCo)x (16 < x < 41) alloys have superior MOR activity and durability as compared to bimetallic PtCo alloys and commercially available Pt/C (comm. Pt/C) catalysts. Among all the compositions studied, the Pt60Mn1.7Co38.3/C catalyst exhibited superior mass activity (1.3 and 1.9 times higher than those of Pt81Co19/C and comm. Pt/C, respectively) toward MOR. Furthermore, all the newly synthesized Pt100-x(MnCo)x/C (16 < x < 41) catalysts showed better CO tolerance when compared with comm. Pt/C. This improved performance of the Pt100-x(MnCo)x/C (16 < x < 41) catalyst can be attributed to the synergistic effect of Co and Mn on the Pt lattice.

Ethylene glycol-assisted synthesis of reduced graphene oxide-supported bimetallic Pt-Co nanoparticles for the ultra-sensitive detection of tert-butyl hydroquinone

Ethylene glycol-assisted synthesis of reduced graphene oxide-supported bimetallic Pt-Co nanoparticles for the ultra-sensitive detection of tert-butyl hydroquinone

Efficient and complete dehydrogenation of hydrazine borane over a CoPt catalyst.

Bimetallic CoPt alloy nanoparticles (NPs) immobilized on CeO2 nanorods (CoPt/CeO2) were synthesized by a facile wet-chemistry reduction method, which showed the highest catalytic efficiency reported to date for the complete dehydrogenation of hydrazine borane with a high TOF value of up to 5454 h-1 at 323 K.

Ultrasensitive sandwich-typed electrochemical immunoassay for detection of squamous cell carcinoma antigen based on highly branched PtCo nanocrystals and dendritic mesoporous SiO2@AuPt nanoparticles.

Squamous cell carcinoma antigen (SCCA) is one of the common squamous cell carcinomas (SCC) in women, which usually works as a tumor biomarker for cervical cancer in diagnostic applications. Herein, bimetallic PtCo highly branched nanocrystals (PtCo BNCs) acted as electrode substrates to construct sandwich-typed electrochemical immunosensor for ultrasensitive detection of SCCA, by using dendritic mesoporous SiO2@AuPt nanoparticles (DM-SiO2@AuPt NPs) to adsorb electroactive thionine (Thi) as a signal label. The PtCo BNCs enlarged the loading of the primary antibody (Ab1), showing effective improvement in conductivity and sensitivity. The DM-SiO2 had abundant pores to incorporate more Thi, on which the decorated AuPt NPs created a great number of active sites to immobilize the secondary antibodies (Ab2), thereby obviously amplifying the detection signals. The prepared sensor exhibited a broader linear range (0.001-120ngmL-1) and a lower detection limit (0.33pgmL-1, S/N = 3), combined with high reproducibility, a low relative standard deviation (below 2.5%) and acceptable recovery (from 98.5 to 110.0%) even in diluted human serum samples. This research provides a substantial platform for clinical diagnosis of SCCA in practice.

Tuning the catalytic performance of Pt/SiO2 catalysts by CoOx modification for selective hydrogenations of unsaturated carbonyl compounds

Tailoring the interface between active metals and promoters to improve catalytic performance is a challenging issue for bicomponent catalysts. Herein, we developed a series of silica supported Pt-CoOx hybrid nanocatalysts though in situ oxidation of supported bimetallic PtCo nanoparticles (NPs) with different Pt/Co ratios. Focusing on the hydrogenation of acetophenone to 1-phenylethanol as the model reaction, the obtained Pt-CoOx/SiO2 catalysts showed superior activity and selectivity compared to Pt/SiO2, and the sample with a Co/Pt molar ratio of 1/3 performed the best. Our research showed that the CoOx on Pt not only changed its electronic and geometric properties, but also promoted the adsorption of reactants and the dissociation of H2. A further increase of the Co/Pt ratio to 1/1, however, reduced the activity due to blockage of the Pt surface.

Synthesizing active and durable cubic ceria catalysts (

Dehydrogenation is considered as one of the most important industrial applications for renewable energy. Cubic ceria-based catalysts are known to display promising dehydrogenation performances in this area. Large particle size (>20 nm) and less surface defects, however, hinder further application of ceria materials. Herein, an alternative strategy involving lactic acid (LA) assisted hydrothermal method was developed to synthesize active, selective and durable cubic ceria of <6 nm for dehydrogenation reactions. Detailed studies of growth mechanism revealed that, the carboxyl and hydroxyl groups in LA molecule synergistically manipulate the morphological evolution of ceria precursors. Carboxyl groups determine the cubic shape and particle size, while hydroxyl groups promote compositional transformation of ceria precursors into CeO2 phases. Moreover, enhanced oxygen vacancies (Vö) on the surface of CeO2 were obtained owing to continuous removal of O species under reductive atmosphere. Cubic CeO2 catalysts synthesized by the LA-assisted method, immobilized with bimetallic PtCo clusters, exhibit a record high activity (TOF: 29,241 h−1) and Vö-dependent synergism for dehydrogenation of bio-derived polyols at 200 °C. We also found that quenching Vö defects at air atmosphere causes activity loss of PtCo/CeO2 catalysts. To regenerate Vö defects, a simple strategy was developed by irradiating deactivated catalysts using hernia lamp. The outcome of this work will provide new insights into manufacturing durable catalyst materials for aqueous phase dehydrogenation applications.

Co decorated low Pt loading nanoparticles over TiO2 catalyst for selective hydrogenation of furfural

Selective hydrogenation of carbonyl groups in biobased chemicals to alcohols is crucial to the economics of broadly sustainable product portfolios. Furfuryl alcohol (FOL), the most prominent chemical of hemicellulose, has been produced by furfural (FAL) hydrogenation over heterogeneous catalysts. In this work, we show the outstanding activity, selectivity, and stability of supported bimetallic PtCo nanoparticle (np) synthesized from a pre-made stock solution of zero valent atomic Pt precursor and Co2(CO)8. With only 0.5 wt% Pt on TiO2, the np-PtCo/TiO2 catalyst exhibits TOF of 14,023 h−1 at 30 °C with > 99.9% FOL selectivity. The stability of the np-PtCo/TiO2 catalyst is verified by the steady performance in reuses at both moderate and full conversions. The oxyphilic Coδ+ in the PtCo nanoparticles induces nucleophilic chemisorption of -CO, resulting in deeply polarized CO bond. DFT calculated FAL adsorption energies on np-Pt and np-PtCo are − 0.22 eV and − 0.74 eV, respectively.

An Enhanced‐Activity and High‐Stability PtCo/N‐Doped Carbon Skeleton Electrocatalyst Derived from UA‐ZIF‐67 Template for Methanol Oxidation

AbstractTo improve electrocatalytic performances of Pt‐based catalysts toward methanol oxidation reaction (MOR) and reduce the consumption of Pt, we report a novel strategy for preparing a PtCo/NCS catalyst with bimetallic PtCo nanoparticles supported on the nitrogen‐doped carbon skeleton (NCS) derived from ulmic‐acid ‐based ZIF‐67 (UA‐ZIF‐67) template. The synthesized optimal NCS has rich mesoporous structure with a BET specific surface area of 451 m2 g−1and average pore diameterof 4.5 nm, possesses graphitic structure containing some CNTs and many graphene layers, and is doped by 8.16 at% nitrogen in the form of pyridine N and pyrrole N. In the optimum PtCo/NCS, metallic Pt and Co nanoparticles with an average size of 3.0±0.5 nm are uniformly supported on the NCS. This PtCo/NCS catalyst shows a high electrocatalytic activity and stability for MOR due to its high electrochemically active specific surface area (ECSA) value, current density, steady‐state current and current retention. The results are attributed to small highly‐dispersed PtCo nanoparticles with good synergistic effects of bimetallic active components supported on the NCS possessing CNTs and graphene layers, suitable nitrogen doping and well‐matched hierarchical pore structure.These findings will provide a new insight in designing and synthesizing high‐performance electrocatalysts.

Bimetallic Pt-Co Nanoparticle Deposited on Alumina for Simultaneous CO and Toluene Oxidation in the Presence of Moisture

Carbon monoxide (CO) and hydrocarbons (HCs) generally have competitive adsorption on the active site of noble-metal nano-catalysts, thus developing an effective way to reduce the passivation of competitive reaction with each other is an urgent problem. In this study, we successfully synthesized transition metal-noble metal (Pt-M) alloys via introducing inexpensive metal elements (M = Ni, Co and Cu) into Pt particles and then deposited on alumina support to form Pt-based catalysts. Subsequently, we choose CO and toluene as polluting gases to evaluate the catalytic activities of Pt-M/Al2O3 catalysts. Introducing inexpensive metal elements (M = Ni, Co, and Cu) significantly changed the physicochemical properties and catalytic activities of these Pt-based catalysts. It can be found that the Pt-Co/Al2O3 catalyst exhibited outstanding catalytic activity for CO and toluene oxidation under mixed gas atmosphere, compared with other Pt-based catalysts, which is due to the higher dispersity, more surface adsorption oxygen, and well redox ability. Surprisingly, H2O could promote the catalytic activities for CO/toluene co-oxidation over the Pt-Co/Al2O3 catalyst. Thus, the present synthetic strategy not only opens an avenue towards the synthesis of noble metal-based catalysts, but also provides an excellent tolerance to H2O in the catalytic process.

Structural, vibrational, and magnetic properties of self-assembled CoPt nanoalloys embedded in SrTiO3

Pulsed laser deposition was used to synthesize vertically aligned nanocomposites (VAN), consisting of ultrathin CoPt nanocolumns embedded in a single crystal SrTiO3 thin film. Combining highresolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), x-ray absorption spectroscopy (XAS) and molecular dynamics (MD) simulations, we provide an in-depth analysis of the structural and vibrational properties of the CoPt phase over a wide range of concentrations. Despite growing the samples at high temperatures (> 600 • C), we find that the CoPt nanoalloys are characterized by a high degree of structural disorder and complete absence of chemical ordering, even after additional sample annealing. Unexpectedly, for a Co concentration exceeding c(Co) 0.55, pole figure measurements unravel a transition from a highly textured short range disordered fcc phase to a disordered hcp phase with c-axis oriented out of plane. These findings, further confirmed by magnetometry measurements, illustrate the profound impact of vertical epitaxy on the structural and thermodynamic properties of bimetallic CoPt alloys.

Carbon nanospheres supported bimetallic Pt-Co as an efficient catalyst for NaBH4 hydrolysis

Sodium borohydride (NaBH4) is widely identified as a promising hydrogen storage material, therefore, developing a catalyst with high efficiency for hydrogen production is an important subject for development and utilization of hydrogen energy. Meanwhile the hydrolytic mechanism of NaBH4 needs further study which is helpful for hydrolysis researches. In this study, an efficient catalyst comprising of carbon nanospheres (CNSs) supporting ultrafine bimetallic Pt-Co nanoparticles (CNSs@Pt0.1Co0.9) has been successfully synthesized for hydrogen evolution from NaBH4 hydrolysis. The growth of the Pt-Co nanoparticles on the surface of CNSs is regulated by adjustment of solvent during the preparation. The as-prepared CNSs@Pt0.1Co0.9 catalyst exhibits an outstanding performance in the kinetic and thermodynamic tests with the highest hydrogen generation rate (HGR) of 8943 mLH2·min−1·gM–1, initial turnover frequency (TOF) value of 280.1 moLH2·min−1·molPt–1, and a low activation energy (Ea) of 38.0 kJ·mol−1. The hydrolytic mechanism has been surveyed simultaneously by the isotopic tracer method through the mass spectrometric analysis. The catalyst retains extremely high catalytic activity value and the hydrogen generation conversion is still 100% even after five cycles in the catalytic performance tests.

Signal-off electrochemiluminescence immunosensor based on Mn-Eumelanin coordination nanoparticles quenching PtCo-CuFe2O4-reduced graphene oxide enhanced luminol

Herein, a facile one-pot intrapolymerization strategy to synthesize manganese-eumelanin coordination nanocomposites (Mn-Eu) was introduced to quench the electrochemiluminescence (ECL) behavior of luminol/H2O2 system. Bimetallic PtCo and CuFe2O4 nanoparticles decorated with reduced graphene oxide was prepared to combine with luminol via electrostatic attractions (Lu-PtCo-CuFe2O4-rGO) which possessed excellent ECL signals. PtCo-CuFe2O4-rGO not only exhibited well electrocatalytic activity toward the electrooxidation reactions of luminol and H2O2, but also facilitated the electroreduction of H2O2 producing more reactive oxygen species (ROSs) which can further enhance the ECL intensity of luminol. To sensitively detect procalcitonin, Mn-Eu labeled-secondary antibodies were employed to specific recognize antigen which incubated with primary antibodies/Lu-PtCo-CuFe2O4-rGO. The quenching mechanism may be via the synergistic effect between Mn-Eu inhibiting the electrooxidation of H2O2 and ECL resonance energy transfer (ECL-RET) from ECL donor luminol to ECL acceptor Mn-Eu. Under optimal experiments, the ECL immunosensor for detecting procalcitonin with a wider linear range from 0.005 pg/mL to 100 pg/mL and a detection limit of 0.0021 pg/mL (S/N = 3) was obtained. The suggested strategy possessed great potential in bioanalysis and will broaden the application of Mn-Eu.

Bimetallic Pt-Co Catalysts for the Liquid-Phase WGS

Bimetallic Pt-Co catalysts derived from cobalt aluminate spinel were investigated in the liquid-phase water–gas shift (WGS) reaction and CO hydrogenation. Liquid-phase WGS is a key reaction in the aqueous-phase reforming (APR) of polyols; thus, WGS activity is essential to formulate good APR catalysts. In this work, catalysts with different Pt/Co molar ratios were synthesized together with a reference Pt/alumina. All the synthesized catalysts were characterized by various techniques in order to gain knowledge on their structural and surface characteristics. WGS activity was tested with a feedstream of CO/H2O = 1/15 (space-time of 76.8 kgcat·s/molCO), isothermal operation at 260 °C and 50 bar, for 10 TOS. Bimetallic Pt-Co catalysts showed improved activity in liquid-phase WGS in comparison to bare Co or Pt catalysts, which was ascribed to the synergistic effect. Despite being subjected to an increased hydrogen concentration in the feedstream (H2/CO between 0 and 12/3), these catalysts maintained a preferential selectivity towards WGS activity. In addition, the effect of temperature (220–260 °C) and pressure (25–50 bar) was investigated over a catalyst with 0.3Pt/CoAl. CO conversion and CO2 yield were more sensitive to temperature, while a higher pressure favored methane production. The measured activation energy in the 220–260 °C temperature range was 51.5 kJ/mol.

Chemically Ordered Pt–Co–Cu/C as Excellent Electrochemical Catalyst for Oxygen Reduction Reaction

This paper reveals the ordered structure and composition effect to electrochemical catalytic activity towards oxygen reduction reaction (ORR) of ternary metallic Pt–Co–Cu/C catalysts. Bimetallic Pt-Co alloy nanoparticles (NPs) represent an emerging class of electrocatalysts for ORR, but practical applications, e.g. in fuel cells, have been hindered by low catalytic performances owning to crystal phase and atomic composition. Cu is introduced into Pt-Co/C lattices to form PtCoxCu1−x/C (x = 0.25, 0.5 and 0.75) ternary-face-centered tetragonal (fct) ordered ternary metallic NPs. The chemically ordered Pt–Co–Cu/C catalysts exhibit excellent performance of 1.31 A mg−1Pt in mass activity and 0.59 A cm−2Pt in specific activity which are significantly higher than Pt-Co/C and commercial Johnson Matthey (JM) Pt/C catalysts, because of the ordered crystal phase and composition control modified the Pt-Pt atoms distance and the surface electronic properties. The presence of Cu improves the surface electronic structure, as well as enhances the stability of catalysts.