Platinum Precursor Research Articles

A low-coordinate platinum(0)-germylene for E–H bond activation and catalytic hydrodehalogenation

Pairing transition metals and heavier tetrylenes (Si, Ge, Sn, Pb) holds great potential for cooperative bond activation and catalysis. In this work, we investigate the reactivity of a low-coordinate Pt(0)/Ge(II) system that emerges from the reaction between the monoligated platinum(0) precursor [(PMe2ArDipp2)Pt(olefin)] with germylene dimer [ArDipp2GeCl]2 (where ArDipp2 = C6H3−2,6-(C6H3−2,6-iPr2)2). The resulting complex reveals ability for cooperative bond activation. Stoichiometric reactions with dihydrogen, water, methanol, ammonia and alkynes unveil the formation of Pt(II)-germyl compounds, characterized by distinct isomeric forms, whose flexibility derives from the particularly low-coordination. We explore its catalytic potential in the hydrodehalogenation of aliphatic, aromatic and main-group halides under dihydrogen atmosphere using both thermal and photochemical conditions, demonstrating promising conversions even for more challenging alkyl chlorides.

Functionalized carbons and Pt/C catalysts from biomass using a plasma process

In this paper, plasma conversion of lignocellulosic biomass to high surface area carbons with tunable porosity and their functionalization toward catalyst supports are presented. Specifically, the technique involves mixing biomass with alkali salts and then oxidizing with atmospheric plasma. The biomass conversion process required time scales of less than 2 min compared to hours for the hydrothermal techniques. Furthermore, the resulting high surface area carbons are decorated with ultra-nano particles of platinum using reduction of platinum precursors using hydrogen plasmas. The resulting functionalized carbons loaded with Pt nanoparticles have shown catalytic activity in decarboxylation and further conversion of oleic acid to aromatic and branched hydrocarbons. The catalytic reaction of the resulting Pt nanoparticle loaded high surface area carbon catalyst revealed 100 % conversion of oleic acid with selectivity > 64 % toward C8-C16 hydrocarbons and aromatics, suggesting high catalytic activity of the employed catalyst in decarboxylation reaction of oleic acid.

First-Principles Calculations of the Effect of γ-Alumina Surface Hydroxyl Structures on the Location and Dechlorination of a Platinum Precursor.

The interaction between Pt precursors and alumina support is an important step in synthesizing Pt/Al2O3 catalysts, while an in-depth understanding of the interaction is still lacking. Herein, density functional theory (DFT) calculations were performed to simulate the coordination of H2PtCl6 with different surface hydroxyl groups, revealing the influence of the γ-Al2O3 surface hydroxyl structure on the position of the Pt precursor and the removal of Cl ligands. After drying, the interaction mechanism between [PtCl6]2- and alumina support involves hydrogen bonds and van der Waals forces, which are the main driving forces for the structural transformation from [PtCl6]2- coordinated with the surface hydroxyl group into the PtClx(OH)y species (OH is the γ-Al2O3 surface group). HO-μ1-AlVI and H2O-μ1-AlVI on the (100) surface with electrophilicity facilitate hauling and activating the electron-rich [PtCl6]2-, but the nucleophilic (110) surface has a weaker interaction with [PtCl6]2-. Combining free energy and electronic property analysis, the stable structures on the (100) surface after drying treatment are PtCl4(OH)2 and PtCl3(OH)3, while only PtCl4(OH)2 structures can be formed on the (110) surface. This study can deepen our understanding of the interaction mechanism between Al-hydroxyl groups and Pt precursors, providing a theoretical reference for the precise placement of Pt active phases and the construction of metal-support interfaces.

Development of an Impinging Jet Microreactor Synthesis Process for Surfactant‐free Pt‐Nanoparticles as PEMFC Catalyst Component

Colloidal, surfactant‐free platinum nanoparticles were prepared via a self‐built continuous impinging jet microreactor synthesis process in alkaline aqueous methanol solution (Co4CatTM process). In these syntheses, methanol functions as a reducing agent as well as an additional solvent. Especially the synthesis of surfactant‐free nanoparticles remained challenging, and additionally, the transfer of this synthesis into a continuous process required several optimization steps. In this contribution we present highly controllable final particle sizes by adjusting process temperature, platinum precursor concentration and molar ratio of the hydroxide and platinum precursor used. The size objective of the surfactant‐free Pt nanoparticles was a range of 1 – 10 nm, due to the intended application in various catalytic processes, especially as PEMFC electrocatalyst. Dynamic light scattering (DLS), ζ‐potential measurements, transmission electron microscopy (TEM) and UV/Vis spectroscopy were used to monitor the particle stability over a certain period of time and study the rate of the reduction reaction in more detail.

Chemotherapeutic Potential of Chlorambucil-Platinum(IV) Prodrugs against Cisplatin-Resistant Colorectal Cancer Cells.

Chlorambucil-platinum(IV) prodrugs exhibit multi-mechanistic chemotherapeutic activity with promising anticancer potential. The platinum(II) precursors of the prodrugs have been previously found to induce changes in the microtubule cytoskeleton, specifically actin and tubulin of HT29 colon cells, while chlorambucil alkylates the DNA. These prodrugs demonstrate significant anticancer activity in 2D cell and 3D spheroid viability assays. A notable production of reactive oxygen species has been observed in HT29 cells 72 h post treatment with prodrugs of this type, while the mitochondrial membrane potential was substantially reduced. The cellular uptake of the chlorambucil-platinum(IV) prodrugs, assessed by ICP-MS, confirmed that active transport was the primary uptake mechanism, with platinum localisation identified primarily in the cytoskeletal fraction. Apoptosis and necrosis were observed at 72 h of treatment as demonstrated by Annexin V-FITC/PI assay using flow cytometry. Immunofluorescence measured via confocal microscopy showed significant changes in actin and tubulin intensity and in architecture. Western blot analysis of intrinsic and extrinsic pathway apoptotic markers, microtubule cytoskeleton markers, cell proliferation markers, as well as autophagy markers were studied post 72 h of treatment. The proteomic profile was also studied with a total of 1859 HT29 proteins quantified by mass spectroscopy, with several dysregulated proteins. Network analysis revealed dysregulation in transcription, MAPK markers, microtubule-associated proteins and mitochondrial transport dysfunction. This study confirms that chlorambucil-platinum(IV) prodrugs are candidates with promising anticancer potential that act as multi-mechanistic chemotherapeutics.

Size-Dependence of the Electrochemical Activity of Platinum Particles in the 1 to 2 Nanometer Range

Monodisperse Pt nanoparticles supported on carbon (Pt/C) were prepared via an impregnation method. By changing the concentration of the platinum precursor in the initial reagent mixture, the average particle size (d) could be controlled to within a narrow range of less than 2 nm. The specific activity (SA) of these materials, when applied to the oxygen reduction reaction (ORR), increased rapidly with d in the range below 1.8 nm, with a maximum SA at d = 1.3 nm. This value is approximately four times that of a commercial Pt/CB catalyst. The electrochemical active area, ECAA (electrochemical surface area (ECSA)/specific surface area (SSA) × 100), decreased drastically from 100% with decreases in d below 1.3 nm. In this study, we present a correlation between SA and ECAA as a means of determining the appropriate d for polymer electrolyte fuel cells (PEFCs) and propose an optimal size.

Rapid CO2 laser treatment of Pt–Fe MOF for efficient electrochemical hydrogen evolution reaction

The quest for efficient hydrogen production via electrochemical water splitting has led to extensive research on catalytic materials. This work focuses on enhancing the catalytic functionality of metal-organic frameworks (MOFs) by incorporating platinum (Pt) to improve the performance of the hydrogen evolution reaction (HER). Fe-based MOFs mixed with platinum precursors were altered through laser treatment, which caused considerable changes in their structure and catalytic activity in just 3 min. This was achieved without the need for vacuum or an inert atmosphere. Characterization techniques including X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and electrochemical measurements were used to characterize the synthesized materials. The laser-treated Pt–Fe MOF demonstrated outstanding HER performance with 3.5 wt% Pt content, outperforming commercial 20 wt% Pt/C catalysts, and exhibiting good stability even after prolonged cycling. These results highlight the potential of laser-treated MOFs for efficient and cost-effective electrochemical hydrogen generation.

Effect of Solvent Ratio (Ethylene Glycol/Water) in the Synthesis of Pt/C Cathode Catalysts on PEM Fuel Cell Performance

Abstract The ethylene glycol (EG)/water mixture composition of an alkaline one-step polyol synthesis for Pt/C catalysts was systematically investigated and optimized for a low ethylene glycol content with regards to resulting Pt particle size and electrochemical performance of membrane electrode assemblies tested as proton exchange membrane (PEM) fuel cell cathode catalysts. Beginning test fuel cell data show a possible reduction of the required EG amount per gram of synthesized catalyst by up to 98% without significantly compromising the initial electrochemical performance. Taking catalyst durability into account, a Pt/C catalyst synthesized with 40 vol% H2O and 32 mM Pt precursor concentration showed a decent initial electrochemical performance (716 mV at 1 A cm-2) as well as an accelerated stress test-derived stability similar to an internal reference catalyst, obtained with 100 vol% EG. In summary, our study shows that optimizing the amount of water and platinum precursor in the synthesis process can lead to catalysts with excellent performance for PEM fuel cells while contributing significantly to cost reduction by using less EG during synthesis.

Synthesis of high-performance low-Pt (1 1 1)-loading catalysts for ORR by interaction between solution and nonthermal plasma

One important approach to address the cost issue of fuel cells is to maximize the utilization of Pt by reducing its loading and enhancing the performance for the oxygen reduction reaction (ORR) as well as durability of catalysts. In this work, a one-step synthesis of highly dispersed low-Pt (111) electrocatalysts (p-Pt/KBs) supported by Ketjenblack is conducted using interaction between solution and nonthermal plasma (SNP). The results show that the plasma-treated platinum precursor dispersion efficiently avoids particle agglomeration and increases more defects of the support surface, which are conducive to the trapping and anchoring of platinum nanoparticles (Pt NPs). The catalyst (p-Pt/KB-NaOH) with a platinum load of 10.8 wt% is obtained by adding sodium hydroxide to the platinum precursor dispersion solution, showing better ORR performance (E1/2 = 0.88 V) and stability compared to the commercial platinum on carbon (Pt/C) catalyst (20 wt%, E1/2 = 0.86 V). This improvement is attributed to the fact that neutralizing chloroplatinic acid slows down the reduction rate of the platinum precursor, effectively controlling the rapid nucleation and slow crystal growth of platinum. As the cathode catalyst for PEMFCs, p-Pt/KB-NaOH exhibits remarkable mass-transfer performance in the high-current density domain (HCD), with maximum power density (Pmax) of 1131 mW cm−2 at 2500 mA cm−2, which is 9.1 % higher than commercial Pt/C. Moreover, the single-cell operates stably for at least 100 h at 1000 mA cm−2 with a negligible decay (1.9 %) of the working voltage, ensuring long-term durability.

Homobimetallic bis-NHC(Ptdvtms)2 Complexes for the Hydrosilylation of Alkenes

A series of six bimetallic bis-NHC(Ptdvtms)2 complexes 1–6 (dvtms = 1,1,3,3-tetramethyl-1,3-divinyldisiloxane) has been designed by expansion of the monometallic Markó-type system in anticipation of synergistic bimetallic cooperation. The new compounds are easily accessible using Karstedt's catalyst [Pt2(dvtms)3] as platinum(0) precursor and the respective bis-(imidazolium) salts (L1–6), deprotonated by potassium tert‑butoxide. Characterization via NMR spectroscopy (1H, 13C, 29Si, 195Pt) and SC-XRD reveals a strong similarity of this new complex class to the parent monometallic complexes. The hydrosilylation reactions of oct-1-ene or 1,1,1,3,3-pentamethyl-3-vinyldisiloxane (MMVi) with 1,1,3,5,5-heptamethyltrisiloxane (MDHM), respectively, are efficiently and selectively catalyzed with turn-over frequencies (TOF) of up to 78,000 h–1 after a significantly shortened induction period compared to their monometallic relatives. Mercury poisoning experiments demonstrate the superiority of bimetallic compared to monometallic systems in terms of stability when exposed to silanes.

Water-assisted purification during electron beam-induced deposition of platinum and gold.

Direct fabrication of pure metallic nanostructures is one of the main aims of focused electron beam-induced deposition (FEBID). It was recently achieved for gold deposits by the co-injection of a water precursor and the gold precursor Au(tfac)Me2. In this work results are reported, using the same approach, on a different gold precursor, Au(acac)Me2, as well as the frequently used platinum precursor MeCpPtMe3. As a water precursor MgSO4·7H2O was used. The purification during deposition led to a decrease of the carbon-to-gold ratio (in atom %) from 2.8 to 0.5 and a decrease of the carbon-to-platinum ratio (in atom %) from 6-7 to 0.2. The purification was done in a regular scanning electron microscope using commercially available components and chemicals, which paves the way for a broader application of direct etching-assisted FEBID to obtain pure metallic structures.

One-Pot Graphene Supported Pt3Cu Nanoparticles—From Theory towards an Effective Molecular Oxygen Reduction Reaction Catalyst

In this work, recent research progresses in the formation of Pt3Cu nanoparticles onto the surface of graphene are described, and the obtained results are contrasted with previously published theoretical studies. To form these nanoparticles, tetrabutylammonium hexachloroplatinate, and copper acetylacetonate are used as platinum and copper precursors, respectively. Oleylamine is used as a reductor and a solvent. The obtained catalyst is characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive spectroscopy X-ray (EDS). To assess the catalytic activity, the graphene-supported Pt3Cu material is tested with cyclic voltammetry, “CO stripping”, and oxygen reduction reaction potentiodynamic curves to find the nature and the intrinsic electrochemical activity of the material. It can be observed that the tetrabutylammonium cation plays a critical role in anchoring and supporting nanoparticles over graphene, from which a broad discussion about the true nature of the anchoring mechanism was derived. The growth mechanism of the nanoparticles on the surface of graphene was observed, supporting the conducted theoretical models. With this study, a reliable, versatile, and efficient synthesis of nanocatalysts is presented, demonstrating the potentiality of Pt3Cu/graphene as an effective cathode catalyst. This study demonstrates the importance of reliable ab inito theoretical results as a useful source of information for the synthesis of the Pt3Cu alloy system.

Molten-Salt Electrochemical Deoxidation Synthesis of Platinum-Neodymium Nanoalloy Catalysts for Oxygen Reduction Reaction.

Platinum-rare earth metal (Pt-RE) nanoalloys are regarded as a potential high performance oxygen reduction reaction (ORR) catalyst. However, wet chemical synthesis of the nanoalloys is a crucial challenge because of the extremely high oxygen affinity of RE elements and the significantly different standard reduction potentials between Pt and RE. Here, this paper presents a molten-salt electrochemical synthetic strategy for the compositional-controlled preparation of platinum-neodymium (Pt-Nd) nanoalloy catalysts. Carbon-supported platinum-neodymium (Ptx Nd/C) nanoalloys, with distinct compositions of Pt5 Nd and Pt2 Nd, are obtained through molten-salt electrochemical deoxidation of platinum and neodymium oxide (Pt-Nd2 O3 ) precursors supported on carbon. The Ptx Nd/C nanoalloys, especially the Pt5 Nd/C exhibit a mass activity of 0.40Amg-1 Pt and a specific activity of 1.41mAcm-2 Pt at 0.9V versus RHE, which are 3.1 and 7.1 times higher, respectively, than that of commercial Pt/C catalyst. More significantly, the Pt5 Nd/C catalyst is remarkably stable after undergoing 20000 accelerated durability cycles. Furthermore, the density-functional-theory (DFT) calculations confirm that the ORR catalytic performance of Ptx Nd/C nanoalloys is enhanced by compressive strain effect of Pt overlayer, causing a suitable weakened binding energies of O* and .

High-efficient Pt@COF nanospheres-based electrochemical-chemical-chemical redox cycling for ultrasensitive microRNAs biosensing

MicroRNAs (miRNAs) have been perceived as important regulators in multifarious biological processes as well as potential biomarkers in clinical diagnosis. Exploring high-efficient sensing platforms for tracing miRNAs in complex biological samples is of great vital. Herein, an ultrasensitive and enzyme-free electrochemical biosensor was constructed based on integration of efficiently catalytic electrochemical−chemical−chemical (ECC) redox cycling with target-induced magnetic DNAzyme walker. Employing porous and easily functionalized covalent organic framework (COF) as carriers, Pt@COF nanospheres (Pt@COF NSs) were facilely prepared by in-situ reduction of platinum precursors in the nanopores-structure of COF. This not only addressed the inevitable migration of pure Pt nanoparticles, but endowed Pt@COF NSs with desirable stability and excellent catalytic activity to boost ECC redox cycling for effective signal enhancement. On this basis, a target-induced magnetic DNAzyme walker was obediently induced to recognize, separate and convert low-abundant miRNA-21 targets into plentiful output DNA chains for accumulated signal amplification. Finally, the as-prepared robust biosensor manifested highly sensitive and selective determination of miRNA-21 with a wide detection range from 100 aM to 10 pM and a low detection limit of 47.5 aM. Meanwhile, the credible detectability and anti-interference were also demonstrated in serum and cell samples, indicating its promising application toward diseases warning.

Hierarchical Co3O4/SAPO-34 supported PtCo bimetallic nanoparticles as highly efficient catalyst for hydrogen generation from ammonia borane hydrolysis

Hierarchical Co3O4/SAPO-34 supported PtCo bimetallic nanoparticles (NPs) with uniform dispersion and narrow size-distribution were prepared for the hydrolysis of AB to produce hydrogen. Strategies including the sequential impregnation of cobalt and platinum precursors followed by partial reduction were employed to anchor Pt NPs. Befitting from the interfacial interaction between Co and Co3O4 NPs, the intermetallic synergistic effect of PtCo NPs and the synergistic interaction between Co NPs and SAPO-34 zeolite, the prepared Pt@Co/Co3O4/SP-10(400,2) catalyst exhibited outstanding catalytic activity with a high turnover frequency (TOF) value of 314 molH2(molPt·min)-1 at 303 K. In addition, the flake-assemble hierarchical structure of SAPO-34 played an important role in improving the dispersion of metal NPs and the mass transfer rate between reactants and active sites.

Photochemically Induced Cyclometalations at Simple Platinum(II) Precursors.

Photochemical cycloplatinations of 2-arylpyridines and related C∧N ligands, as well as terdentate heteroaromatic N∧N∧C, N∧C∧N, and N∧C∧C compounds, are demonstrated using (Bu4N)2[Pt2Cl6] or [PtCl2(NCPh)2] as precursors at room temperature. Mono- or bis-cyclometalated Pt(II) complexes with C∧N ligands are obtained depending on excitation wavelength and precursor. Monitoring experiments show that photoexcitation enables both the N-coordination and the subsequent C-H metalation. Photochemical synthetic protocols have been developed, which are advantageous with respect to the established thermal procedures and have allowed the synthesis of the first Pt(II) complexes with N∧C∧C ligands.

Effect of preparation method on active sites variation for catalytic oxidation of toluene over Pt/MCM-48

Toluene oxidation behavior has been investigated on a series of catalysts with Pt supported on MCM-48 that has a large specific surface area & easy-transported three-dimensional channels prepared by four different methods. It was found that various introduction ways of Pt have a great influence on both Pt content and state, resulting in a difference in catalytic oxidation performance. Pt/M48-PG prepared via the post-grafting method possesses both the highest Pt content (0.83 wt%) and active species of Pt0 & surface labile oxygen (accounting for 46% and 55%, respectively), resulting in the lowest T90 (155 °C) and the highest TOF (7.92 ×10−3·s−1). Characterization results showed that the amine functional groups could be successfully grafted onto the support's surface, which is beneficial for the binding of platinum precursor with support, leading to the high actual loading efficiency and dispersion of Pt, both of which contribute to retaining more Pt0 and surface labile oxygen active species.

Potent Platinum(IV) Prodrugs That Incorporate a Biotin Moiety to Selectively Target Cancer Cells

Four platinum(IV) prodrugs incorporating a biotin moiety to selectively target cancer cells were synthesised, characterised, and their biological activity assessed. All complexes exhibited exceptional in vitro cytotoxicity against a panel of cancer cell lines, with [Pt(5,6-dimethyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)(biotin)(hydroxido)](NO3)2, (2) exhibiting the lowest GI50 of 4 nM in the prostate Du145 cancer cell line. Each complex displayed significantly enhanced activity compared to cisplatin, with 2 being 1000-fold more active in the HT29 colon cancer cell line. Against the MCF-7 breast cancer cell line, in which high levels of biotin receptors are expressed, 2, [Pt(4,7-dimethoxy-1,10-phenanthroline)(1S,2S-diaminocyclohexane)(biotin)(hydroxido)](NO3)2, (3), and [Pt(5-methyl-1,10-phenanthroline)(1S,2S-diaminocyclohexane)(biotin)(hydroxido)](NO3)2, (4) exhibited enhanced activity compared to their platinum(II) cores, with 4 being 6-fold more active than its platinum(II) precursor. Furthermore, 3 exhibited 3-fold greater selectivity towards MCF-7 breast cancer cells compared to MCF10A breast healthy cells, and this was further confirmed by platinum uptake studies, which showed 3 to have almost 3-fold greater uptake in MCF-7 cells, compared to MCF10A cells. The results show that lipophilicity and selectivity both contributed to the cellular uptake of 1-4; however, this was not always translated to the observed cytotoxicity.

Metal Oxide Inclusion in Polycrystalline Pt-Based Electrocatalyst for an Ammonia Oxidation Reaction

In April 2021, an average daily amount of 421 ppm of carbon dioxide (CO2) was recorded in the atmosphere, CO2 has increased more than 100 ppm in the last 66 years. Fuel cells are a suitable option for addressing the major issues of meeting current and future energy demand while also reducing CO2 pollution. If the fuel source originates from renewable sources, this makes the overall process CO2-neutral. In the quest for sustainable fuels with high energy density, focus is currently on nitrogen-containing fuels, such as ammonia (NH3) since their oxidation will yield predominantly dinitrogen (N2). Different platinum precursors (K2PtCl6 and H2Pt(OH)6) were used to study the effect on the electrocatalytic activity of Pt for an ammonia oxidation reaction when different metal oxides are added to Pt particles. The metal oxides chosen are CeO2, Fe2O3, and Ag2O. The morphology and element distribution of the Pt catalyst was determined by SEM equipped with an EDS detector. The crystalline phase present in the samples was determined by X-ray diffraction. Cyclic voltammetry was used to characterize the particles and to study the catalytic activity of Pt electrocatalyst for ammonia oxidation. No significant difference was found (by student t-test) between the onset potential for ammonia electrooxidation of Pt particles and Pt precursor. Average onset potential for ammonia electrooxidation was -0.464 V vs Ag|AgCl. The highest average current peak densities were reported by catalyst from non-chlorinated precursor with addition of Fe2O3. Current densities of nanoparticles synthesized from the H2Pt(OH)6 precursor decreased to 24.9 x 10-2 mA/cm-2 with CeO2 addition, but increased to 28.2 x 10-2 mA/cm-2 when Fe2O3 was added. We are currently working on the electrochemical characterization and oxidation of ammonia with catalyst from Ag2O addition

Plasmonic Hot-Electron-Painted Au@Pt Nanoparticles as Efficient Electrocatalysts for Detection of H2O2.

Plasmon-driven catalysis of metal nanostructures has garnered wide interest. Here, a photogenerated plasmonic hot-electron painting strategy was reported to form Au@Pt composite nanoparticles (Au@Pt NPs) with high catalytic reactivity without using reducing agents. Au nanoparticles, including Au nanospheres (Au NSs), Au nanorods (Au NRs), and Au nanobipyramids (Au NBPs), generated hot electrons under localized surface plasmon resonance (LSPR) excitation, which made the platinum precursor reduced as a consequence that Pt(0) atoms were painted on the surface of Au NPs to form an asymmetric Pt shell outside the plasmonic Au core. Compared with bare Au NPs, Au@Pt NPs exhibited significantly enhanced electrocatalytic activity toward reduction of H2O2 due to the bimetallic synergistic effect and great dispersion of Au@Pt NP-modified indium tin oxide (Au@Pt NPs/ITO). It exhibited a linear detection of H2O2 in a wide concentration range from 0.5 to 1000 μM with a low detection limit of 0.11 μM (S/N = 3). Therefore, the plasmonic hot-electron-painted Au@Pt NPs represent a novel and simple method for the design of advanced noble asymmetric metal nanomaterials.