Amount Of Platinum Research Articles

Migration of Platinum Nanoparticles via Volatile Platinum Dioxide during Lean High-Temperature Ageing of Diesel Oxidation Catalysts

When platinum-containing diesel oxidation catalysts (DOC) are exposed to high temperatures under lean conditions, the platinum nanoparticles form volatile platinum dioxide on the catalyst surface. The exhaust flow carries the volatile platinum dioxide to the downstream aftertreatment catalyst, such as the selective catalytic reduction (SCR) catalyst, that is responsible for reducing the nitrogen oxides (NOx) emissions and can negatively impact its performance, by promoting the parasitic oxidation of ammonia. Here we investigate the factors such as exposure time, temperature and DOC design characteristics for their impact on the platinum dioxide migration, by characterising the amount of platinum deposited on the SCR catalyst at very low levels (<5 ppm), using inductively coupled plasma optical emission spectroscopy (ICP-OES) fire assay technique. Our results indicate that well-dispersed platinum, not associated with palladium, is most prone to platinum dioxide migration. We also compare several methods to suppress the platinum dioxide migration from the DOC, such as sintering of the platinum nanoparticles, stabilising the platinum nanoparticles via interaction with palladium or covering the platinum nanoparticles with a high surface area capture layer to trap the volatile platinum dioxide.

Manipulation in local coordination of platinum single atom enables ultrahigh mass activity toward hydrogen evolution reaction

Atomic-engineering of noble metal into single-atom electrocatalysts with well-defined active sites has been considered as an effective approach to enhance the mass-activity towards hydrogen evolution reaction (HER), crucial for the practical implementation of this sustainable technology. Herein, we devise a metallic-coordination strategy via a facile one-step pyrolysis method, for the atomic isolation of a small amount of platinum (Pt, 0.45 wt%) atoms in the surface of nickel (Ni) nanoparticles (Pt1@Ni) encapsulated into nitrogen-doped carbon nanotubes (Pt1@Ni/NCNT). Such a Pt1@Ni/NCNT single-atom alloy catalyst exhibits a record-high and all-round superior HER performance including mass-activity (up to 350.7 A mgPt−1@η150), stability (>50 h at 100 mA cm−2), pH-tolerance by comparison with Pt1@NC. Our density functional theory calculations combined with in situ Raman spectroscopic studies reveal a synergistic dual-active-site catalytic mechanism, involving the fast hydrogen spillover effect on coordinated Ni supports and accelerated water dissociation in acidic and alkaline medium, respectively. A strong electronic hybridization of 5d orbital of alloyed Pt and 3d orbital of Ni atoms modulates the d band center of Pt, which not only boosts HER activity but also stabilizes Pt single atoms. Due to the double protecting strategy from strong anchoring effect in Ni support and chemically stable NCNT shell, a robust stability is achieved for Pt1@Ni/NCNT hierarchal catalyst. Our findings open up a new avenue to substantially tailor the activity of surface Pt atoms for the design of highly efficient and durable noble metal-based catalysts.

High-temperature planar asymmetric ceramic membranes: Effect of the Pt amount and dispersion on the H2 separation performance

This work investigates for the first time the effect of Pt catalyst amount and dispersion on hydrogen permeation performances of BaCe0.65Zr0.20Y0.15O3−δ–Gd0.2Ce0.8O2−δ (BCZY–GDC) composite planar Cer-Cer membranes with asymmetrical architecture, aiming to maximize the ratio between the permeated hydrogen and the metal content. To boost the hydrogen separation reactions, Pt must be deposited on both the dense and porous sides of the membrane. Moreover, the complex architecture of the porous layer can be used to disperse Pt particles providing a good interaction with the membrane. To fulfil this aim BCZY-GDC membranes composed of a 20 μm thick active dense layer and a 600 μm thick, porous support were produced by tape casting and impregnated with different amounts of platinum. Hydrogen permeation properties were thoroughly investigated examining the composition of the feed and the sweep gasses, temperature, stream humidification, catalyst amount and nature of the dispersion media. The effect of Pt-catalysed hydrogen permeation and water splitting reaction at the permeate side was investigated and discussed. It was found that using an optimal amount of Pt solution to activate the porous side of the membranes is paramount to increase hydrogen permeation in the whole operating temperature range while keeping low the amount of noble metal catalyst. Moreover, the selection of a proper solvent with good interaction with the membrane allows the obtainment of smaller Pt nanoparticles resulting in higher permeation. The best performances in terms of hydrogen permeation (0.74 and 1.29 mL min−1 cm−2 at 750 °C using a feed stream with respectively 50 % and 80 % of H2 in He) were obtained using an acetone-based solution for depositing 1.5 mg cm−2 of Pt at the porous side. This work suggests that the metal deposition plays a non-trivial role in the hydrogen separation process and should be fully evaluated to increase the final performance while cutting down the cost of the Pt catalyst and therefore, of the final device.

Rapid spectrophotometric determination and extraction of platinum(IV) from pharmaceuticals assisted by 2-(2-(1-(thiophene-2-yl) ethylidene) hydrazinyl) benzoic acid (TEHBA).

It has been suggested that the chelating agent 2-(2-(1-thiophene-2-yl) ethylidene) hydrazinyl) benzoic acid (TEHBA) be utilized to extract, separate and measure platinum(IV) by UV-visible spectrophotometry at the microgram level. Following 5 min of heating the reaction mixture in a water bath, Pt(IV)-TEHBA complex formed. This complex was formed in the presence of potassium iodide solution with a molar absorption coefficient 1.9 × 103 dm3mol-1cm-1. At 420nm, the substance exhibited the greatest absorption. As Beer's law described, the Pt(IV)-TEHBA complex for platinum(IV) has a beer's range of 10-50μgcm-3. It was determined that the proportion ratio of the Pt(IV)-TEHBA complex was 1:1 after its extraction. Despite the investigation of interference from various ions, it was ascertained that the method exhibited selectivity exclusively towards platinum(IV). The trace amounts of platinum(IV) were extracted and quantified from synthetic mixtures representing alloys, binaries and ternary synthetic mixtures. The process of extracting platinum(IV) from pharmaceutical samples involves the implementation of a specific method. Moreover, the procedure exhibits a progressive segregation of palladium(II), platinum(IV) and nickel(II) while also boasting its ease of operation.

Highly active ultralow loading Pt electrodes for hydrogen evolution reaction developed by magnetron sputtering

Developing cost-effective components for PEM electrolyzers is key to transforming renewable energy into H2. Platinum is a scarce and expensive material but also, is the most active known catalyst for hydrogen evolution reaction in PEM electrolysis; thus it is of utmost importance to focus on developing electrocatalysts that utilize the minimum amount of platinum without losses in cell performance to make PEM electrolysis affordable. In addition, and with the aim of scaling up electrode production, it is imperative to develop a robust automated industrial manufacturing process to avoid the waste of catalyst during electrode preparation. In this work, magnetron sputtering gas aggregation method is studied for developing three low loading Pt electrodes (0.105, 0.062, and 0.052 mg cm−2), achieving remarkable overpotentials as low as 8 mV at 10 mA cm−2 for HER, showing similar activity than commercial Pt electrodes with more than 4 times less Pt (compared to 0.3 mgcm−2 Pt commercial GDL).

Leaching of catalyst platinum from cured silicone elastomers: A preliminary study for comparing reagents

Addition curing systems involve two-part silicones which require the mixture of a silicone polymer with a catalyst to initiate the cure. Platinum is the most commonly used metal catalyst for addition curing of silicones by hydrosilylation which involves the crosslinking by the addition reaction of silicon hydride species to unsaturated bonds, mainly CC, but also CO or CN double bonds. After crosslinking of the polymers, the platinum catalyst cannot be recovered but remains in the silicone materials throughout the entire product life. In the end, platinum is disposed of together with the silicones and is thus lost to the value chain. The overall objective of this work was to develop a recycling process for the recovery of platinum from addition-cured silicone elastomers. In the first step, this was achieved by efficient digestion methods and by optimizing the leaching processes for exemplary commercial silicone elastomer products. Two different silicone materials were investigated, both of which were crosslinked with a platinum catalyst. The initial Pt content in the tested samples was 12.6 ± 0.2 mg/kg for a commercial silicone impression material and 6.3 ± 0.5 mg/kg for a silicone baking mold, measured by graphite furnace atomic absorption spectrometry (GF-AAS). Samples were first frozen with liquid nitrogen to improve brittleness and then crushed with a simple food processor to obtain a silicone granule. Various acid mixtures, mainly based on sulfuric acid, were investigated as digestion methods in order to extract platinum from the silicone network. These had different effects on the dissolution behavior of silicone samples and the amount of platinum extracted in each case. The amount of platinum leached from the filtrate of the digested samples in each case was measured by ICP-OES to evaluate the efficiency of different leaching mixtures. In addition, the dissolved platinum species present in the solutions was identified by UV/VIS as tetrachloridoplatinate(II) complex. The best platinum leaching results so far were obtained with two methods, both of which used a leaching mixture based on sulfuric acid and hexamethyldisiloxane (M2). In the presence of hydrochloric acid, 9.6 ± 1.6 mg platinum/kg was leached from the silicone impression material and 4.2 ± 0.8 mg platinum/kg from the silicone baking mold. With the additional use of aqua regia instead of hydrochloric acid, 10.4 ± 2.8 mg platinum/kg was extracted from the silicone impression material and 4.8 ± 1.0 mg platinum/kg was extracted from the silicone baking mold. These methods were replicated with n = 3. Using statistical evaluation methods (F-test, t-test, and confidence interval), no significant difference was found between these two best methods. Recovery of platinum(0) from leach mixtures has not yet been achieved due to high dilution and very low platinum concentration in samples and will be part of another study.

Contrast variation method applied to structural evaluation of catalysts by X-ray small-angle scattering

In the process of developing carbon-supported metal catalysts, determining the catalyst particle-size distribution is an essential step, because this parameter is directly related to the catalytic activities. The particle-size distribution is most effectively determined by small-angle X-ray scattering (SAXS). When metal catalysts are supported by high-performance mesoporous carbon materials, however, their mesopores may lead to erroneous particle-size estimation if the sizes of the catalysts and mesopores are comparable. Here we propose a novel approach to particle-size determination by introducing contrast variation-SAXS (CV-SAXS). In CV-SAXS, a multi-component sample is immersed in an inert solvent with a density equal to that of one of the components, thereby rendering that particular component invisible to X-rays. We used a mixture of tetrabromoethane and dimethyl sulfoxide as a contrast-matching solvent for carbon. As a test sample, we prepared a mixture of a small amount of platinum (Pt) catalyst and a bulk of mesoporous carbon, and subjected it to SAXS measurement in the absence and presence of the solvent. In the absence of the solvent, the estimated Pt particle size was affected by the mesopores, but in the presence of the solvent, the Pt particle size was correctly estimated in spite of the low Pt content. The results demonstrate that the CV-SAXS technique is useful for correctly determining the particle-size distribution for low-Pt-content catalysts, for which demands are increasing to reduce the use of expensive Pt.

Low-temperature oxidative removal of benzene from the air using titanium carbide (MXene)-Supported platinum catalysts

MXenes are an emerging class of two-dimensional (2D) inorganic materials with great potential for versatile applications such as adsorption and catalysis. Here, we describe the synthesis of a platinized titanium carbide MXene (Pt@Ti3C2) catalyst with varying amounts of platinum (0.1%–2 wt.%) for the low-temperature oxidation of benzene, an aromatic volatile organic compound often found in industrial flue gas. A 1% formulation of Pt@Ti3C2–R allowed near-complete (97%) oxidation of benzene to CO2 at 225 °C with a steady-state reaction rate (r) of 0.119 mol g−1·h−1. This low-temperature catalytic oxidation reaction was promoted by an increase in the lattice oxygen (O*)/Pt2+ species (active sites) of 1%Pt@Ti3C2–R from 45.3/34.6% to 71.0/61.1% through pre-thermal reduction under H2 flow, as revealed by X-ray photoelectron spectroscopy, temperature-programmed reduction, and in situ diffuse reflectance infrared Fourier transform spectroscopy analyses. The cataltyic activity of 1% Pt@Ti3C2–R against benzene was assessed under the control of the key process variables (e.g., catalyst mass, flow rate, benzene concentration, relative humidity, and time-on-stream) to help optimize the oxidation reaction process. The results provide new insights into the use of platinum-based 2D MXene catalysts for low-temperature oxidative removal of benzene from the air.

Molecular Dynamics Analysis of the Scattering Phenomena of Oxygen Molecules on an Ionomer Surface in Catalyst Layer of Fuel Cell

As energy demand increases and global warming progresses, expectations for fuel cells, which generate electricity through chemical reactions between hydrogen and oxygen, are rising. There are various types of fuel cells, which are classified according to the electrolyte. Polymer electrolyte fuel cells (PEFCs) are expected to be used in stationary power sources for home use and fuel cell vehicles because of their low operating temperature, short start-up time, and ease of miniaturization. The cost has been an issue in the widespread use of fuel cells. The amount of platinum used in the catalyst layer (CL) must be reduced to reduce costs. However, it increases the current density per unit area of platinum. There are three factors that contribute to voltage drop: ohmic polarization, activation polarization, and diffusion polarization. At high current densities, the voltage drop due to diffusion polarization is dominant. The main cause of diffusion polarization is the transport resistance of oxygen molecules in the CL, and improving the oxygen transport properties in the CL will lead to lower cost PEFCs. In this study, we analyzed the transport properties of oxygen molecules in the CLs of PEFCs using the Monte Carlo (MC) method. The effect of oxygen scattering on the overall oxygen transport properties was investigated by considering the behavior on the surface of the ionomer film (surface diffusion) into the MC method, which simulates the overall transport in the PEFC CL. The objective of this study is to reproduce accurate oxygen transport by comparing the results of MC and molecular dynamics (MD) methods. First, we used the MC method to analyze oxygen scattering phenomena. In this study, we used the 3D structure data of CL in the MC simulations. The three-dimensional structure of the sample was reconstructed from sequential slice images. Molecules were assumed to reflect specularly on the boundaries of the simulation domain. Oxygen molecules were randomly placed in the simulation system. The time step was set at 5 ps and the simulation time was set at 4 μs. In order to examine the effect of surface diffusion on the transport properties of oxygen molecules, the simulation was performed using various conditions of surface diffusion. We calculated the effective diffusion coefficient of oxygen in the CL as the transport property of oxygen molecules in the MC method. As the surface diffusion coefficient increases, the effective diffusion coefficient of oxygen increases. When the surface diffusion coefficient is small, the effective diffusion coefficient of oxygen increases due to a decrease in the time constant, which determines the probability distribution of the surface residence time. However, when the surface diffusion coefficient is large, a different trend emerges. As the time constant increases, the effective diffusion coefficient has a peak value and then decreases. Next, to verify the model of surface diffusion in the MC method, we analyzed the scattering phenomenon of oxygen molecules in a simulation system that simulates the pores in the CL using the MD method. We modeled the nano pores in the CL as a slit between the ionomer walls in the MD method. Nafion with the equivalent weight (EW) of 1146 was used as polymer model. The number of Nafion chains is set at 4, and the water content λ is set at 7. Three-dimensional periodic boundary conditions were applied to the simulation domain. After the system was equilibrated, 1 ns of NVT simulation was performed for production. The temperature was set at 297 K. The behavior of oxygen molecules impacting on the ionomer wall was analyzed. We analyzed the behavior of oxygen molecules colliding with the ionomer membrane using the MD method. The average residence time of surface diffusion on the ionomer thin film was of the order of 10-10s. When the calculation results were compared with the MC results, it was found that the average residence time obtained by the MD method was the value where the surface diffusion coefficient affects much on the effective diffusion coefficient. Comparing the results of the MD method with the surface diffusion model used in the MC method, there are some discrepancies between the results and the model. For example, the MC method used a model in which oxygen molecules reflect diffusively on the ionomer surface. However, in the MD method, it was found that oxygen molecules tend to reflect in the direction of travel (Fig. 1). Therefore, a more accurate model of the MC method needs to be developed in the future. Figure 1

Operando x-Ray Absorption Spectroscopy Investigation of Secondary Metal Doping into Iron-Nitrogen-Carbon Catalysts for Oxygen Electroreduction

Oxygen reduction reaction (ORR) plays a key role in the development of fuel cell technology, and great efforts have been made to reduce the amount of platinum, required to speed up this sluggish reaction, or, even more desirable, to use efficient electrocatalysts based on earth-abundant metals. To date, numerous single-atom catalysts in the form of metal-doped carbon-nitrogen materials (MNC) have proved to be a promising alternative to ORR Pt-based materials. [1-3]In this study we employed advanced spectroscopic techniques, namely Mössbauer spectroscopy and operando X-ray absorption (XAS) spectroscopy, to understand the structural and electronic factors underlying an increase in the catalytic turn over frequency (TOF) of bimetallic FeSnNC and FeCoNC catalysts, relative to the parent FeNC materials. In particular, 57Fe Mössbauer spectroscopy identified a larger ratio of D1/D2 species in both bimetallic catalysts, supporting a larger ratio of Fe(III)-Nx/Fe(II)-Nx sites. The combination of extended X-ray absorption fine structure (EXAFS) modeling, and the analysis of operando X-ray absorption near-edge spectroscopy (XANES) spectra revealed a disordered carbon structure around FeNx active sites, and variations in the iron oxidation state that can be linked to the enhanced intrinsic catalytic reactivity (TOF). This talk is therefore intended to draw attention to the potential of the XAS technique, especially when applied to in-situ/operando studies in the field of electrocatalysis. References F. Luo, A. Roy, L. Silvioli, D.A. Cullen, A. Zitolo, M.T. Sougrati, I.C. Oguz, T. Mineva, D. Teschner, S. Wagner, J. Wen, F. Dionigi, U.I. Kramm, J. Rossmeisl, F. Jaouen and P. Strasser. P-block single-metal-site tin/nitrogen-doped carbon fuel cell cathode catalyst for oxygen reduction reaction. Nature Materials 2020, 19, 1215-1223A. Zitolo, N. Ranjbar, T. Mineva, J. Li, Q. Jia, S. Stamatin, G.F. Harrington, S.M. Lyth, P. Krtil, S. Mukerjee, E. Fonda, F. Jaouen. Identification of catalytic sites in cobalt-nitrogen-carbon materials for the oxygen reduction reaction. Nature Communications 2017, 8(1), 957A. Zitolo, V. Goellner, V. Armel, M. T. Sougrati, T. Mineva, L. Stievano, E. Fonda, F. Jaouen. Identification of catalytic sites for oxygen reduction in iron and nitrogen doped graphene materials. Nature Materials 2015, 14, 937-942

Boosting Oxygen Reduction Reaction with Fe-Based Single-Atom Catalysts: The Role of Cluster Interactions

Fuel cells (FCs) have emerged as a promising alternative for efficient electricity production in the future [1]. However, their widespread commercialization is hindered by their prohibitive cost due to the large amount of platinum used in these electrochemical systems [2]. Platinum is used to accelerate the unfavorable kinetics of the cathodic oxygen reduction reaction (ORR) [3]. To achieve large-scale and cost-effective development of FCs, it is essential to find high-performance platinum-free catalysts. Two solutions are mainly reported in the literature: the development of non-precious metal-based carbon catalysts and metal-free carbon catalysts. However, the work reported on these two types of carbon catalysts is sometimes contradictory regarding the actual nature of the active sites and the mechanisms of reduction of oxygen molecules on the catalyst [4].Pyrolyzed metal-nitrogen-carbon (M-N-C) catalysts for the ORR, especially single-atom catalysts (SACs), have been widely studied because they exhibit excellent electrocatalytic performance, thanks to the high content of metal atoms anchored on a carbon support [5]. Recent research has indicated that the combination of single-atom active sites with metal nanoclusters can further improve the catalytic activity, but the underlying mechanism remains unclear [6]. Therefore, it is necessary to develop model catalysts based on both single-atoms and nanoclusters to better understand their catalytic activity.In this work, we prepared nitrogen-doped and iron-doped carbon catalysts (called Fe-NC below) with precise control of the type of iron in the material. First, the functionalization of an activated carbon was performed by carbonizing it under air in the presence of urea. Then, the sample was placed in an autoclave for hydrothermal treatment in the presence of FeCl3.6H2O to allow the incorporation of iron, and thermal post-treatment was applied to synthesize model catalysts (Fig. 1a). The precursor ratio and final pyrolysis temperature were adjusted and optimized to produce either iron-based single atoms (SA) (here referred to as FeSA-NC) or atomic clusters (AC) associated with single atoms (here referred to as FeSA+AC-NC). The results show that the iron-based catalysts exhibit outstanding catalytic activity (Fig. 1b) and durability (Fig. 1c) in alkaline medium for the ORR, even better than commercial Pt (20 wt.%)/C in the case of FeSA+AC-NC. The analysis provided insight into the development of highly efficient multifunctional electrocatalysts, where the presence of iron nanoclusters was found to be a crucial determinant of the catalytic activity for the ORR.[1] M.K. Debe, Electrocatalyst approaches and challenges for automotive fuel cells, Nature. 486 (2012) 43–51. https://doi.org/10.1038/nature11115.[2] C. Sealy, The problem with platinum, Mater. Today. 11 (2008) 65–68. https://doi.org/10.1016/S1369-7021(08)70254-2.[3] M. Borghei, J. Lehtonen, L. Liu, O.J. Rojas, Advanced Biomass-Derived Electrocatalysts for the Oxygen Reduction Reaction, Adv. Mater. 30 (2018) 1703691. https://doi.org/10.1002/adma.201703691.[4] A. Dessalle, J. Quílez-Bermejo, V. Fierro, F. Xu, A. Celzard, Recent progress in the development of efficient biomass-based ORR electrocatalysts, Carbon. 203 (2023) 237–260. https://doi.org/10.1016/j.carbon.2022.11.073.[5] K. Liu, J. Fu, Y. Lin, T. Luo, G. Ni, H. Li, et al., Insights into the activity of single-atom Fe-N-C catalysts for oxygen reduction reaction, Nat. Commun. 13 (2022) 2075. https://doi.org/10.1038/s41467-022-29797-1.[6] X. Wan, Q. Liu, J. Liu, S. Liu, X. Liu, L. Zheng, et al., Iron atom–cluster interactions increase activity and improve durability in Fe–N–C fuel cells, Nat. Commun. 13 (2022) 2963. https://doi.org/10.1038/s41467-022-30702-z. Figure 1

A Robust Fuel Cell Operating on Lunar Water Derived Fuels

The space proven fuel cell technology will likely play a crucial role in the upcoming expansion of human presence into the solar system. In particular, polymer electrolyte membrane (PEM) fuel cells excel due to their high power-density, low weight and their ability to operate on in-situ resource utilization (ISRU) based fuels. Hydrogen fuel and oxygen can be derived from lunar water, which is believed to be trapped in permanently shadowed craters on the lunar poles. However, Colaprete A. et al. found that H2S and NH3 as well as smaller quantities of other sulfur compounds and hydrocarbons are detected alongside the water ice. These compounds are well known fuel impurities which cause reversible yet also irreversible damage to the platinum catalyst and other components of the membrane electrode assembly (MEA). Commercially available fuel cells on the other hand require highly purified fuels with contamination levels in the low ppb region. Thus, these impurities pose a profound problem, even if only a fraction of them is carried onwards to the hydrogen fuel and oxygen. Subsequent intensive purification processes are costly and require large amounts of energy – a process which could render the whole approach useless.As mentioned before, H2S and other sulphur compounds adsorb strongly to the platinum metal and irreversibly degrade its catalytic activity until performance drops to unusably low levels. This effect is directly related to the amount of available catalyst, since a doubling of the platinum loading leads to a two-fold reduced degradation. We hypothesize that the resilience of a fuel cell can not only be improved by increasing the amount of platinum, yet also by using the available platinum more effectively. A lot of the platinum remains inactive within a fuel cell electrode due to different effects like excessive ionomer coverage or particle agglomeration. With the so-called platinum utilization parameter the obtained fuel cell performance is related to the total platinum weight and thus can be used to rate how effective platinum is used. In our recently published review, we found that electrospun electrodes have the highest platinum utilization out of all compared fuel cell electrode manufacturing methods. Furthermore, electrospun electrodes are reportedly less prone to other degradation mechanisms like Ostwald ripening. In this ongoing work, we aim to fabricate MEAs with fully electrospun electrodes and benchmark them against a commercial alternative. The electrodes will be operated with contaminated gases in half cell as well as full cell degradation experiments. The outcome of this research aims to support the exploration community in designing robust energy systems on the moon by investigating the effect of lunar contaminants on fuel cell systems.

Comparison of Different Carbon Supports By Simulation of Agglomeration in Polymer Electrolyte Fuel Cell Catalyst Ink

Polymer electrolyte fuel cells (PEFCs) are one of the most possible power sources for heavy-duty vehicles like trucks due to their high conversion efficiency and low environmental impact. Since platinum which is often used as a catalyst is expensive, it is essential to reduce the amount of platinum by increasing the power density. Regarding materials, it was reported that the activity is increased by supporting platinum on porous carbon [1]. However, there is a voltage drop in the high current density region comparing non-porous carbon. This is caused by oxygen transport properties, but the relationship with the carbon structure is unknown. Oxygen moves through the voids in the catalyst layer, so it is necessary to control the porous structure that forms the voids. This porous structure depends on the conditions of the catalyst layer fabrication process. In particular, the dispersion process is important to determine the size of the carbon agglomerate, or the backbone of the catalyst layer. In this study, an agglomeration model in catalyst ink was developed, and the dispersion process was verified by simulation under various conditions to elucidate the factors that affect agglomeration.The discrete element method (DEM) was used for the simulation. In this study, aggregates were approximated into spheres, and the forces between the particles were the drag force from the fluid, Brownian motion, and particle-particle interactions. Based on DLVO theory, the particle-particle interactions were given as an attractive force due to the van der Waals interaction and a repulsive force due to the overlapping of the electric double layer. In addition, the effect of ionomer was considered. The ionomer effect was introduced as a repulsive force and modeled with the same equation as the repulsion due to the electric double layer. The dielectric dependence equation of the ionomer shape that Magnus et al. modeled [2] was incorporated. As the amount of ionomer added increases, a binder effect is observed between the particles. This effect was also introduced using the adsorption data of ionomers on carbon. The carbon was assumed to be non-porous (Vulcan) and porous (Ketjen). Considering the difference in the platinum ratio on the surface depending on the carbon porosity, the Hamaker constant, which affects the van der Waals force, was determined. Also, the zeta potential, which affects the electric double layer force, was used at different values for carbons. In this study, the calculations were started with the particles uniformly dispersed in the ink. Periodic boundary conditions were used as boundary conditions. Using the above numerical model, simulations were conducted with different water-alcohol ratios and ionomer carbon ratios (I/C).As a result, it was confirmed that differences in the agglomerate size for two carbon supports. This result implies that the composition of the ink and the type of carbon affect the catalyst layer structure and cell performance.AcknowledgmentThis study was carried out under the project of Development of Advanced PEFC Utilization Technologies supported by the NEDO.Reference[1] Y. C. Park et al., J. Pow. Sou r., 315, 179 (2016).[2] M. So et al., Int. J. Hydrog. Energy, 44, 28984 (2019).

Directed Dual Charge Pumping Tunes the d-Orbital Configuration of Pt Cluster Boosting Hydrogen Evolution Kinetic.

Achieving high catalytic activity with a minimum amount of platinum (Pt) is crucial for accelerating the cathodic hydrogen evolution reaction (HER) in proton exchange membrane (PEM) water electrolysis, yet it remains a significant challenge. Herein, a directed dual-charge pumping strategy to tune the d-orbital electronic distribution of Pt nanoclusters for efficient HER catalysis is proposed. Theoretical analysis reveals that the ligand effect and electronic metal-support interactions (EMSI) create an effective directional electron transfer channel for the d-orbital electrons of Pt, which in turn optimizes the binding strength to H*, thereby significantly enhancing HER efficiency of the Pt site. Experimentally, this directed dual-charge pumping strategy is validated by elaborating Sb-doped SnO2 (ATO) supported Fe-doped PtSn heterostructure catalysts (Fe-PtSn/ATO). The synthesized 3%Fe-PtSn/ATO catalysts exhibit lower overpotential (requiring only 10.5mV to reach a current density of 10mAcm- 2), higher mass activity (28.6 times higher than commercial 20wt.% Pt/C), and stability in the HER process in acidic media. This innovative strategy presents a promising pathway for the development of highly efficient HER catalysts with low Pt loading.

Characterization, modes of interactions with DNA/BSA biomolecules and anti-tumor activity of newly synthesized dinuclear platinum(II) complexes with pyridazine bridging ligand.

Platinum-based drugs are widely recognized efficient anti-tumor agents, but faced with multiple undesirable effects. Here, four dinuclear platinum(II) complexes, [{Pt(1,2-pn)Cl}2(μ-pydz)]Cl2 (C1), [{Pt(ibn)Cl}2(μ-pydz)]Cl2 (C2), [{Pt(1,3-pn)Cl}2(μ-pydz)]Cl2 (C3) and [{Pt(1,3-pnd)Cl}2(μ-pydz)]Cl2 (C4), were designed (pydz is pyridazine, 1,2-pn is ( ±)-1,2-propylenediamine, ibn is 1,2-diamino-2-methylpropane, 1,3-pn is 1,3-propylenediamine, and 1,3-pnd is 1,3-pentanediamine). Interactions and binding ability of C1-C4 complexes with calf thymus DNA (CT-DNA) has been monitored by viscosity measurements, UV-Vis, fluorescence emission spectroscopy and molecular docking. Binding affinities of C1-C4 complexes to the bovine serum albumin (BSA) has been monitored by fluorescence emission spectroscopy. The tested complexes exhibit variable cytotoxicity toward different mouse and human tumor cell lines. C2 shows the most potent cytotoxicity, especially against mouse (4T1) and human (MDA-MD468) breast cancer cells in the dose- and time-dependent manner. C2 induces 4T1 and MDA-MD468 cells apoptosis, further documented by the accumulation of cells at sub-G1 phase of cell cycle and increase of executive caspase 3 and caspase 9 levels in 4T1 cells. C2 exhibits anti-proliferative effect through the reduction of cyclin D3 and cyclin E expression and elevation of inhibitor p27 level. Also, C2 downregulates c-Myc and phosphorylated AKT, oncogenes involved in the control of tumor cell proliferation and death. In order to measure the amount of platinum(II) complexes taken up by the cells, the cellular platinum content were quantified. However, C2 failed to inhibit mouse breast cancer growth in vivo. Chemical modifications of tested platinum(II) complexes might be a valuable approach for the improvement of their anti-tumor activity, especially effects in vivo.

Analysis of platinum-based anticancer injections cisplatin and carboplatin in blood serum and urine of cancer patients by photometry, fluorometry, liquid chromatography using a Schiff-base as derivatizing reagent

Photometric, fluorometric and liquid chromatographic methods were proposed to analyze Pt(II) from cis-platin and carbo-platin injections after derivatization with reagent 2-oxo-propanoic acid N-phenylhydrazonecarbothioamide. The reagent reacted with metals Au(III), Ag(I), Mn(II), Pt(II), Mo(VI), V(V/IV) to develop their characteristic colors in the pH range 3–12 and were extracted in organic solvent trichloromethane. The photoluminescent behavior of ligand and its metal complexes was investigated to correlate the emission pattern. Liquid chromatographic method was also proposed to analyze cis-platin and carbo-platin anti-cancer drugs based on the pre-column derivatizing platinum(II) with ligand. The complex of platinum was separated and eluted from HPLC column Microsorb C-18, (150 cm x 4.6 mm i.d, 5 µm) comprising eluents - tetrabutyl ammonium bromide (1 mM)-sodium acetate (1 mM)-acetonitrile-water-methanol (02:02:06:22:68 v/v/v/v/v). Metals Au(III), Ag(I), Mn(II), V(IV/V), Mo(VI) were also separated completely. The linear calibration range 0.5–2.5 µg/mL was observed following Beer’s law with detection limit of 150.00 ng/mL Pt(II). The determination of cis-platin and carbo-platin injections by photometric, fluorometric and chromatographic methods showed RSD (n = 3) 1.14–3.12, 0.98–2.84, 0.92–2.72% respectively. The developed methods were employed to analyze cis-platin in samples of serum and urine of cancer patients undergoing chemotherapy and platinum amounts were observed within 45.0—86.0, 49.0—91.0, 42.0—84.0 ng/mL and 82.0—398, 81.0—389, 74.0—391 ng/mL with relative standard deviation (RSD) (n = 4) of 2.28—3.88, 2.40—3.82, 2.52—3.82% and 2.52—3.91, 2.44—3.94, 1.98—3.24% by liquid chromatographic, fluorometric and photometric techniques respectively.

One-Dimensional, First-Row Transition Metal, Core-Shell Architectures as Multifunctional Electrocatalysts in Alkaline and Acidic Conditions

The development of practical electrocatalysts for fuel cells, electrochemical sensors, and batteries requires nanostructured architectures with high catalytic activity and good long-term durability. It is also essential that they have very low or even no platinum content. There has also been a recent emphasis on the importance of designing multifunctional catalysts with the ability to efficiently catalyze a wide-range of electrochemical reactions in both acidic and alkaline media. In light of these requirements, we have developed a solution-based synthetic method to prepare core-shell nanowires consisting of inexpensive and abundant first-row transition metals coated with precious metal shells. The core-shell motif enables a substantial quantity of platinum to be removed from the catalytically inactive core of the material, while also resulting in the ability to tune the activity of platinum through electronic and structural interactions between the two metals. The as-synthesized core-shell nanowires have a complex surface structure that brings together metal oxide and precious metal active sites that are active toward OER and result in a significant reduction in the overpotential for OER when compared with pure Pt and Co nanowires. In addition, we have developed an electrochemical process that selectively removes the metal oxide from the surface of the nanowires enabling the catalysts to be activated toward SOM oxidation in acidic media and ORR in alkaline media. For example, the activated core-shell nanowires display a 1.5-fold and a 4-fold increase in the specific activity and mass activity of methanol oxidation, respectively, relative to a pure platinum nanowire.

Quaternary Ammonium Palmitoyl Glycol Chitosan (GCPQ) Loaded with Platinum-Based Anticancer Agents-A Novel Polymer Formulation for Anticancer Therapy.

Quaternary ammonium palmitoyl glycol chitosan (GCPQ) has already shown beneficial drug delivery properties and has been studied as a carrier for anticancer agents. Consequently, we synthesised cytotoxic platinum(IV) conjugates of cisplatin, carboplatin and oxaliplatin by coupling via amide bonds to five GCPQ polymers differing in their degree of palmitoylation and quaternisation. The conjugates were characterised by 1H and 195Pt NMR spectroscopy as well as inductively coupled plasma mass spectrometry (ICP-MS), the latter to determine the amount of platinum(IV) units per GCPQ polymer. Cytotoxicity was evaluated by the MTT assay in three human cancer cell lines (A549, non-small-cell lung carcinoma; CH1/PA-1, ovarian teratocarcinoma; SW480, colon adenocarcinoma). All conjugates displayed a high increase in their cytotoxic activity by factors of up to 286 times compared to their corresponding platinum(IV) complexes and mostly outperformed the respective platinum(II) counterparts by factors of up to 20 times, also taking into account the respective loading of platinum(IV) units per GCPQ polymer. Finally, a biodistribution experiment was performed with an oxaliplatin-based GCPQ conjugate in non-tumour-bearing BALB/c mice revealing an increased accumulation in lung tissue. These findings open promising opportunities for further tumouricidal activity studies especially focusing on lung tissue.

Encapsulating Pt clusters during the crystallization of MWW zeolite

Directly encapsulation of Pt clusters within MWW zeolite was realized by precisely regulating the synthetic parameters, especially the alkalinity and the Pt content during the hydrothermal synthesis. Simple addition of Pt(NH3)4(NO3)2 to the routine recipe for MWW synthesis resulted in a mixture of MWW to FER zeolites, while appropriately lowering the alkalinity of the initial gel composition favored the formation of pure MWW phase and simultaneously the incorporation of Pt clusters into the micropores of MWW (Pt/Na/Al2O3/H2O/HMI/SiO2 = 0.0015/0.18/0.044/15/0.34/1). At high Pt loading (Pt/SiO2>0.00225), however, the crystallinity decreased considerably and the 3D MWW structure gradually evolved into disordered layers, while Pt particles located on the surface of the disordered layers and were prone to grow into larger ones. In short, addition of Pt(NH3)4(NO3)2 in the initial gel altered the crystallization process of MWW zeolite, and Pt-MWW could be obtained by appropriately lowering the alkalinity and accurately controlling the amount of platinum.

Textural effect of Pt catalyst layers with different carbon supports on internal oxygen diffusion during oxygen reduction reaction.

One way to address the cost issue of polymer electrolyte membrane fuel cells (PEMFCs) is to reduce the amount of platinum used in the cathode catalyst layers (CLs). The oxygen mass transfer resistance of the cathode CLs is the main bottleneck limiting the polarization performance of low Pt-loading membrane electrodes at high current densities. Pt nanoparticles, ionomers, carbon supports, and water in cathode CLs can all affect their oxygen mass transfer resistance. From the perspective of carbon supports, this paper changed the texture of CLs by adding carbon nanotubes (CNTs) or graphene oxide (GO) into carbon black (XC72) and studied its impact on the oxygen mass transfer resistance. A mathematical model was adopted to correlate total mass transfer resistance and internal diffusion efficiency factor with CL structure parameters in order to determine the dominant textural effect of a CL. The results show that adding 30%CNT or 20GO to carbon black of XC72 improved the electrocatalytic performance and mass transfer capability of the composite carbon-supported Pt catalyst layers during oxygen reduction reaction. The study further reveals that the smaller particle-sized carbon material with tiny Pt nanoparticles deposition can minimize the internal oxygen diffusion resistance. A less dense CL structure can reduce the oxygen transfer resistance through the secondary pores. The conclusion obtained can provide guidance for the rational design of optimal cathode CLs of PEMFCs.