Morphology Of Pt Nanoparticles Research Articles

Platinum nanoparticles decorated TiO2 nanotubes for VOCs and bacteria removal in simulated real condition: Effect of the deposition method on the photocatalytic degradation process efficiency

The incorporation of noble metals onto TiO2 nanostructure is considered as a promoting method to enhance the photocatalytic degradation of pollutant in air treatment process. In this study, highly organized TiO2 nanotubes (NTs) were grown by the anodization method of Titanium substrates. The TiO2-NTs were successfully decorated by platinum (Pt) nanoparticles (NPs) using two different deposition methods: (1) electrodeposition and (2) photodeposition.We explore the impact of different deposition methods on the morphology of Pt nanoparticles (NPs) dispersed onto TiO2 nanotubes and the optical characteristics of Pt-TiO2 nanocomposites, investigating their efficacy in photocatalytic degradation We investigate the effect of varying the deposition method on the morphology of Pt-NPs dispersed onto TiO2 nanotubes and the optical properties of the Pt-TiO2 nanocomposites and their efficient photocatalytic activity degradation against Volatile Organic Compounds (VOCs) and bacteria. Scanning and Transmission Electron Microscopy (SEM and TEM) reveal a nanotubular TiO2 anatase structure adorned with Pt NPs, with the quantity and size of NPs contingent upon the deposition technique employed. The photoluminescence (PL) spectra demonstrate that the Pt/TiO2 heterojunction facilitates the separation of photogenerated charges, thereby diminishing carrier recombination rates. To point out the effect of Pt NPS, both pure TiO2 and Pt/TiO2 heterojunction were tested in the photodegradation of Ethyl Acetate (EA). The Pt/TiO2 heterojunction exhibits superior photocatalytic performance compared to TiO2 in EA degradation, regardless of the Pt deposition method employed. Optimal results are achieved with 120 s of Pt electrodeposition and 3 h of Pt photodeposition under visible irradiation, yielding kinetic constants of approximately 0.245 and 0.195 mg.m−3.s−1, respectively, underscoring the pivotal role of the platinum deposition method in pollutant photodegradation. Respectively simultaneous removal of EA and bacteria (Escherichia coli) was tested using Pt and non-Pt decorated TiO2 NTs. We attributed a total degradation of the bacteria after 180 min using the two efficient photocatalysts Electro 120 s and Photo 3 h compared to 60 % of degradation using pure TiO2 nanotubes.

Effect of uniformity and surface morphology of Pt nanoparticles to enhance oxygen reduction reaction in polymer electrolyte membrane fuel cells

Platinum (Pt)-based electrocatalysts supported by reduced graphene oxide (rGO) is fabricated under microwave-assisted polyol method with various nucleation and growth conditions. The surface morphologies of the Pt nanoparticles (NPs) under various reaction conditions owing to different Pt NP sizes and inter-particle spacings are investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, cyclic and linear sweep voltammetry, and electrochemical impedance spectroscopy. The synthesized Pt/rGO catalyst under nucleation and growth times of 10 s and 50 s, respectively, exhibits excellent catalytic activity with increased electrochemical surface area, high density, good uniformity and surface morphology with a particle size and inter-particle spacing of 2.16 nm and 17.2 nm, respectively. These results elucidate the relationship between the Pt NP morphology distribution and oxygen reduction reaction of catalysts in polymer electrolyte membrane fuel cell systems. We also highlight the important role of size and inter-particle spacing on the Pt electrochemical catalystic performance.

Identifying the morphology of Pt nanoparticles for the optimal catalytic activity towards CO oxidation.

The morphology of nanoparticles (NPs) is crucial for determining their catalytic performance. The dramatic changes in the morphology of metal NPs during reactions observed in many in situ experiments pose great challenges for the identification of the geometry for optimal catalytic activities, which arouses the controversial understanding of the reaction mechanism. In this work, taking CO oxidation as a model reaction, we coupled a multiscale structure reconstruction model with kinetic Monte Carlo simulations to study the catalytic performance of the Pt NPs with changing morphology and reaction conditions. Through the quantitative analysis of contour plots for turnover frequencies, we show that the NPs with more well-coordinated sites exhibit optimal activity under CO-rich conditions at higher temperatures, while the reactivity of NPs with more low-coordination sites is optimal under O2-rich conditions at lower temperatures. Further analysis indicates that the competitive adsorption of CO and O2 plays the key role, in which the structure with optimal activity has a closer CO and O coverage. This work not only reconciles the controversy of the active geometry in the experiments, but offers an efficient method to guide the rational design of high-performance catalysts.

The effect of imidazolium ionic liquid on the morphology of Pt nanoparticles deposited on the surface of SrTiO3 and photoactivity of Pt–SrTiO3 composite in the H2 generation reaction

Photocatalytic water splitting has great potential in solar-hydrogen production as a low-cost and environmentally friendly method. Different unique techniques used to obtain photocatalysts with various modifications to improve H2 generation have been introduced. In the present work, SrTiO3 was successfully synthesized via the solvothermal method in the presence of ionic liquid (IL) - 1-butyl-3-methylimidazolium bromide ([BMIM][Br]) followed by surface decoration with Pt particles using the photodeposition method. The effect of the noble metal content and presence of IL on the morphology, optical and surface properties of SrTiO3, thereby the effectiveness of hydrogen generation, has been thoroughly examined and presented. Unexpectedly, the presence of [BMIM][Br] at the SrTiO3 surface affected the interaction between the semiconductor surface and platinum particles formed throughout photodeposition. Platinum particles at the surface of SrTiO3_IL were found to be in the form of 2D clusters with a size of 1 nm. In comparison, Pt deposited on SrTiO3 photocatalyst without application of IL created larger, three-dimensional structures with a diameter exceeding 5 nm. This is the reason why the total amount of platinum deposited on the SrTiO3_IL sample is smaller than that on SrTiO3 and justifies a higher efficiency of hydrogen generation of Pt modified SrTiO3 photocatalyst in comparison to SrTiO3 prepared in the presence of IL. The mechanism of H2 generation in the water-splitting reaction in the presence of SrTiO3_Pt photocatalyst was discussed.

Modification of dewetting characteristics for the improved morphology and optical properties of platinum nanostructures using a sacrificial indium layer.

Metal nanoparticles (NPs) fabricated by means of the solid state dewetting (SSD) approach are applicable in many optoelectronic, biomedical and catalytical applications. However, the fabrication of metallic NPs with the low diffusivity elements such as platinum (Pt) has been challenging for the well-defined configuration and uniformity due to the low diffusivity of Pt atoms and thus the optical properties suffer. In this paper, the evolution of well-defined configuration and improved uniformity of Pt NPs are demonstrated by the altered solid state dewetting (ASSD) approach using a sacrificial indium (In) layer. Upon annealing, the high diffusivity In atoms can lead to the formation of In-Pt alloy due to the inter-mixing at the interface and the dewetting process advances along with the enhanced diffusion of In-Pt alloy atoms. Eventually, well-defined Pt NPs are formed by means of complete desorption of In atoms by sublimation. By the control of In and Pt ratio in the bilayers with the fixed total thickness such as In4.5 nm/Pt1.5 nm, In3 nm/Pt3 nm, In1.5 nm/Pt4.5 nm, the isolated dome shaped Pt NPs of various size are demonstrated, which reflects the significant impact of In component in the dewetting process. The optical characterization of Pt NPs exhibits the formation of quadrupolar resonance and strong dipolar resonance bands in the UV and VIS regions respectively, which are tunable based on the morphology of Pt NPs. In specific, the dipolar resonance peaks demonstrate a red shifting behavior with the increment of size of Pt NPs and gradually become narrower along with the improvement of uniformity of Pt NPs.

Plasmonic Pt Nanocrystals by Using a Sacrificial In Component via the Enhanced Dewetting on Sapphire (0001): Improvement on Morphological and Localized Surface Plasmon Resonance Properties

Modulation of functional metallic nanoparticles (NPs) in terms of their size, configuration, and dimension can offer a promising route to control the optical, catalytic, magnetic, and sensing properties for a wide range of applications. Herein, the platinum (Pt) nanostructures of improved morphological and localized surface plasmon resonance properties are demonstrated via the enhanced solid-state dewetting by using a sacrificial indium (In) layer on sapphire (0001). Upon annealing, the concurrent occurrence of intermixing between In and Pt atoms, formation of In–Pt alloy and sublimation of In atoms plays major roles in accelerating the dewetting process, which results in the formation of definite Pt nanostructures. The alteration in the In and Pt ratio readily varies the shape, size, and areal density of the resulting Pt NPs. The optical characteristics reveal that the localized surface plasmon resonance (LSPR) response is sensitively affected by the resulting surface morphology of Pt NPs. Specifically, ...

Carbon-supported Pt nanoparticles with (100) preferential orientation with enhanced electrocatalytic properties for carbon monoxide, methanol and ethanol oxidation in acidic medium

The relationship between atomic arrangement (morphology) and catalytic activity/selectivity in heterogeneous catalysis is an actual hot research topic concerning a range of reactions. This article evaluates one-pot synthesized carbon-supported Pt nanoparticles with preferential Pt(100) orientation prepared with an environmentally friendly shape-directing agent and compares this with Pt/C polycrystalline towards CO, methanol and ethanol electrooxidation reactions. The preferentially cubic nanomaterial (Pt-(100)) interacts differently with CO molecule and presents distinct hydrogen adsorption/desorption characteristics. Pt/C polycrystalline exhibits a CO-stripping profile with one peak at 0.86 V in contrast to three peaks between 0.75 and 0.86 V and a pre-peak at about 0.4–0.6 V for the Pt/C-(100), which may be associated to the unique surface characteristics of the cubic material. The onset potentials towards carbon monoxide, methanol and ethanol electro-oxidation reactions on Pt/C-(100) are 22%, 21% and 54% lower than on Pt/C polycrystalline. The ratio between the forward per backward peak current densities for the electrooxidation of ethanol and methanol are higher on Pt/C-(100), which suggests that Pt(100) domains are more tolerant to undergo poisoning by the intermediates/by-products formed in these reactions. Proton exchange membrane fuel cells fed with pure hydrogen and with a H2/CO mixture show superior performance using Pt/C-(100) as anode in comparison to Pt/C polycrystalline catalyst. These results evidence that controlling the morphology of Pt nanoparticles is a key factor to improve the catalytic activity of the polymer electrolyte fuel cell fueled with fuels that involve the electro-oxidation of CO.

Preparation of Pt Nanocatalyst on Carbon Materials via a Reduction Reaction of a Pt Precursor in a Drying Process.

Platinum (Pt) nanocatalyst for a proton-exchange membrane fuel cell (PEMFC) was prepared on a carbon black particle or a graphite particle coated with a nafion polymer via a reduction of platinum(II) bis(acetylacetonate) denoted as Pt(acac)2 as a Pt precursor in a drying process. Sublimed Pt(acac)2 adsorbed on the nafion-coated carbon materials was reduced to Pt nanoparticles in a glass reactor at 180 degrees C of N2 atmosphere. The morphology of Pt nanoparticles on carbon materials was observed by scanning electron microscopy (SEM) and the distribution of Pt nanoparticles was done by transmission electron microscopy (TEM). The particle size was estimated by analyzing the TEM image using an image analyzer. It was found that nano-sized Pt particles were deposited on the surface of carbon materials, and the number density and the average particle size increased with increasing reduction time.

Enhanced Electrocatalysis for Methanol Oxidation on Ordered {[PdPW11O39]5–/Pt/PAMAM}n Multilayer Composites

AbstractThe {[PdPW11O39]5–/Pt/PAMAM}n multilayer composites constructed from G4.0 Amino‐terminated poly (amidoamine) dendrimer (PAMAM), Pt and Keggin‐type palladium(II)‐substituted polyoxometalates anion ([PdPW11O39]5–) were prepared via layer by layer electro‐depositing technique. The X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), and field emission scanning electron microscope (FE‐SEM) characterization indicate that the Pt nanoparticles have been anchored on the as‐prepared nanocomposites. And the morphologies of Pt nanoparticles are influenced by deposition potential, the number of layers of {[PdPW11O39]5–/Pt/PAMAM}n multilayer nanocomposites, and the existence of PAMAM. The electrocatalytic properties and stability of {[PdPW11O39]5–/Pt/PAMAM}n multilayer nanocomposites were investigated by cyclic voltammetry. Experimental investigation results reveal that PAMAM is a good support for Pt nanoparticle growth due to its interior cavity structure and high stability. [PdPW11O39]5– play an important role to prevent intermediate product (mainly as CO) in the methanol oxidation from poisoning the as‐prepared catalyst. The {[PdPW11O39]5–/Pt/PAMAM}3/GC shows better electrocatalytic properties, stability, and CO tolerance ability than Pt/GC and {Pt/PAMAM}3/GC fabricated by similar electrodeposition processes.

Shape-controlled synthesis of Pt nanoparticles via integration of graphene and β-cyclodextrin and using as a noval electrocatalyst for methanol oxidation

The integration of graphene nanosheets (GNs) and β-cyclodextrin (CD) may bring about large surface area and high conductivity of GNs and unique supramolecular recognition capability of CD together. In this paper, for the first time, GNs-CD was used as a supporting material to construct nanodendritic hydrangea-like Pt nanoparticles, which was implemented by a facile wet chemical procedure. β-CD on GNs surface was used to regulate the final morphology of Pt nanoparticles without additional capping agent and seeds, and GNs functioned as a matrix to obtain a relatively uniform distribution of Pt nano-clusters. Electrocatalytic performance of the as-prepared Pt/GNs-CD hybrid was investigated by cyclic voltammetry (CV), chronoamperometry, COad stripping voltammetry, and electrochemical impedance spectroscopy (EIS). The Pt/GNs-CD hybrid exhibited much higher catalytic activity and stability than Pt/GNs and Pt/Vulcan X72R towards methanol oxidation, suggesting that Pt/GNs-CD hybrid could be a promising electrocatalyst for high-performance direct methanol fuel cells (DMFCs) applications.

The Morphologies of Pt Decorated on PANI Membrane and Effects on Glucose Biosensor

This paper mainly studies on the morphologies of Platinum(Pt) nanoparticles decorated on polyanilene(PANI)and their influence on the sensitivity of glucose biosensor. Seldom researches were carried on the morphologies of Pt nanoparticles and the optimization of parameters. Compared by scanning electron microscopy(SEM), cyclic voltammetry(CV) and glucose current response, Pt completely wrapped PANI nanofibers shows better electrochemical stability, sensitivity and larger catalytic area than different kinds of Pt decorated PANI membranes. Pt completely wrapped PANI nanofibers are provided by electrochemical deposition Pt nanoparticles on PANI nanofibers under a special voltage. The average diameter of nanofibers which form porous Pt/PANI membrane is 100 nm. CVs of this membrane become stable in seven circles and provide a higher current peak which indicates larger catalytic area. The sensitivity indicated by current-time glucose response is several times of the other membranes.

The impact of aging environment on the evolution of Al2O3 supported Pt nanoparticles and their NO oxidation activity

The impact of the aging environment on the size, morphology and distribution of Pt nanoparticles supported on Al2O3 and on their NO oxidation activity is studied. To this end, the fresh catalyst Pt/Al2O3 (Pt/Al/F) is aged under different aging environments mimicking the aging process of a real diesel oxidation catalyst (DOC) including phosphorus (P) poison as a chemical contaminant. These catalysts are characterized by N2-physisorption, CO chemisorption, XRD, solid state 27Al MAS NMR, HAADF-STEM, HR-TEM, EDX analyses and CO-DRIFTS. The characterization results reveal that the thermal aging in air at 800°C leads to a heterogeneous size and spatial distribution of Pt nanoparticles in the catalyst (Pt/Al/O). The morphology is mainly limited to truncated cubic structures that are dominated with (100) crystal facets. Differently, aging in a lean diesel exhaust environment (Pt/Al/R) restricts the extensive Pt particle growth, size distribution to narrow and morphology predominantly to cuboctahedral that contains both (111) and (100) planes, though the former tends to dominate the surface. P seems to control both the growth of Pt particles and the morphology that is mainly limited to spherical irrespective of the aging environment (P/Pt/Al/O or P/Pt/Al/R). The normalized (per surface Pt atoms) forward rate constant of NO oxidation and the corresponding activation energy are determined for the differently treated catalysts and compared them with those reported in previous relevant studies. From these results it is evident that the reaction is indeed structure sensitive. The catalyst treated in lean diesel exhaust environment (Pt/Al/R) presents the best activity followed by the fresh Pt/Al/F and thermally Pt/Al/O aged catalysts. The difference in the NO oxidation activity of the catalysts is attributed to the morphology of Pt nanoparticles. These results correlate very well with the real DOC monolith that was aged on a heavy duty small truck for 250h under different driving profiles.

액상환원공정을 이용한 백금 나노 입자의 합성

In this study, Platinum(Pt) nanoparticles were synthesized by using polyol process which is one of the liquid phase reduction methods. Dihydrogen hexachloroplatinate (IV) hexahydrate <TEX>$(H_2PtCl_6{\cdot}6H_2O)$</TEX>, as a precursor, was dissolved in ethylene glycol and silver nitrate (<TEX>$AgNO_3$</TEX>) was added as metal salt for shape control of Pt particle. Also, polyvinylpyrrolidone (PVP), as capping agent, was added to reduce the size of particle and to separate the particles. The size of Pt nanoparticles was evaluated particle size analyzer (PSA). The size and morphology of Pt nanoparticles were observed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM). Synthesized Pt nanoparticles were studied with varying time and temperature of polyol process. Pt nanoparticles have been successfully synthesized with controlled sizes in the range 5-10 and 20-40 nm with cube and multiple-cube shapes.

Effect of the Morphology of Pt Nanoparticles of Supported Pt Model Catalysts on CO Oxidation

In order to investigate the influence of particle morphology on the catalytic activity of supported Pt model catalyst, platinum nanoparticles (NPs) with different morphologies were synthesized by a chemical method and loaded onto SiO 2 to give well-defined supported catalysts. CO oxidation was used as the probe to investigate the catalytic activities of these Pt/SiO 2 model catalysts. X-ray fluorescence, X-ray photoelectron spectroscopy, diffuse reflectance Fourier transform infrared spectroscopy, and transmission electron microscopy characterization demonstrated that the different activities of these Pt/SiO 2 catalysts were due to different crystal surfaces, which strongly influenced the adsorption and oxidation of CO on the Pt NPs.

Three-Dimensional Spatial Distributions of Pt Catalyst Nanoparticles on Carbon Substrates in Polymer Electrolyte Fuel Cells

The Fuel Cell Electrode (FCE), consisting of platinum particles or platinum alloy particles supported on carbon substrates, is one of the key components in the polymer electrolyte fuel cells (PEFCs). In order for the detailed characterization, it is crucial to determine three-dimensional (3D) morphologies of Pt nanoparticles on carbon substrates (Pt/C). In this communication, 3D structures of Pt/C with two different kinds of substrates have been examined using a nano-scale 3D imaging technique, transmission electron microtomography. It was found that the TEC10V50E had Pt catalytic nanoparticles located only at the substrate surface, while the TEC10E50E showed Pt nanoparticles both inside and at the surface of the carbon substrate.

Directed and random self-assembly of Pt–Au nanoparticles

The results and findings of the controlled synthesis of poly-vinyl-pyrrolidone (PVP)-protected Pt and Pt–Au nanoparticles of sharp and polyhedral morphology using the modified polyol method are reported. The highly sharp cubic, octahedral, and tetrahedral Pt nanoparticles are prepared by the reduction of H 2PtCl 6 using ethylene glycol (EG) at 160 °C with the assistance of AgNO 3. Here, PVP and H 2PtCl 6 are added gradually. In order to make the synthesis of Pt–Au bimetal nanoparticles, these polyhedral Pt nanoparticles have been used as seeds for the reduction of HAuCl 4 by EG at an appropriate time. The reduction of HAuCl 4 modifies the sharp morphology of Pt nanoparticles into the cubic Pt–Au nanoparticles. It is important to note that the cubic Pt–Au alloy nanoparticles appear after a short reduction time namely, approximately 15 min. The reported findings of the spherical and irregular Pt–Au alloy nanoparticles in their oriented as well as random self-assembled form are interesting and useful. The results show that single and bimetal nanoparticles with their sharp corners arrange themselves regularly and directly, where as nanoparticles with less sharp corners arrange irregularly.

Direct Observation of the Reversible Changes of the Morphology of Pt Nanoparticles under Gas Environment

Large faceted Pt particles prepared in solution were in situ observed by ETEM (Environmental Transmission Electron Microscopy) during oxidation - reduction cycles. Reversible shape transformations were observed with the increase or decrease of the ratio of (111) faces to (001) faces in H2 and O2 respectively, at pressures of a few mbars. Under Hydrogen, the shape is relatively close to the Wulff shape of an fcc crystal under vacuum, while under oxygen, the (001) faces extend and the (111) faces shrink due to a stronger adsorption of oxygen on the more open (100) faces. Going from hydrogen to oxygen, the surface energy anisotropy is inverted.

The synthesis and characterization of platinum nanoparticles: a method of controlling thesize and morphology

In this paper, Pt nanoparticles with good shapes of nanocubes and nano-octahedraand well-controlled sizes in the range 5–7 and 8–12 nm, respectively, havebeen successfully synthesized. The modified polyol method by adding silvernitrate and varying the molar ratio of the solutions of silver nitrate andH2PtCl6 has been used to produce Pt nanoparticles of the size and shape to be controlled. The sizeand morphology of Pt nanoparticles have been studied by transmission electron microscopy(TEM) and high resolution TEM (HRTEM). The results have shown that their very sharpand good shapes exist in the main forms of cubic, cuboctahedral, octahedral andtetrahedral shapes directly related to the crystal nucleation along various directions of the{100} cubic,{111} octahedraland {111} tetrahedral facets during synthesis. In particular, various irregular and new shapes of Ptnanoparticles have been found. Here, it is concluded that the role of silver ions has to be consideredas an important factor for promoting and controlling the development of Pt nanoparticles of{100} cubic,{111} octahedraland {111} tetrahedral facets, and also directly orienting the growth and formation of Ptnanoparticles.

Toward to branched platinum nanoparticles by polyol reduction: A role of poly(vinylpyrrolidone) molecules

Branched Pt nanoparticles with nanometer sizes have been successfully synthesized by reduction of H2PtCl6·6H2O precursor in ethylene glycol (EG) in the presence of small amounts of NaNO3 and PVP. Morphologies of the Pt nanoparticles can be systematically evolved from regular octahedron, and triangular plate via tri-pod, penta-pod, and octa-pod to multi-pod needle-like shapes only by decreasing concentrations of H2PtCl6·6H2O and NaNO3 at a constant NaNO3/H2PtCl6·6H2O molar ratio and the same PVP concentration. To the best of knowledge, this is the first report for the synthesis of Pt penta-pod. High resolution transmission electron microscope (TEM) observation of the Pt nanoparticles demonstrates that the Pt branches actually extendedly grow out from certain angles of triangular plates, octahedrons, and decahedrons, respectively. Multi-branched needle-like Pt nanocrystals are believed probably to originate from further anisotropic growth of the Pt octa-pods or overlap of small branched Pt nanoparticles. PVP molecules have been found to play an important role in controlling morphologies of the branch-like Pt nanoparticles besides NaNO3. It probably is the cooperated kinetic adsorption and desorption of PVP molecules and various anions on particle surfaces that influence the growth of the Pt nanoparticles. A reasonable growth mechanism has been suggested to explain the evolution of the Pt branches, in which the difference among growth rates along various crystallographic directions of face-centered cubic Pt crystal probably determines final morphologies of the Pt nanocrystals.

Formation Mechanism of Pt Single-Crystal Nanoparticles in Proton Exchange Membrane Fuel Cells

In proton exchange membrane fuel cells, hydrogen permeated from the anode to the cathode was found to reduce soluble Pt species and produce faceted and dendritic Pt nanoparticles in the cathode ionomer. Moving away from the carbon support particles, the morphology of Pt nanoparticles changed from dendritic shapes to truncated tetrahedrons, truncated octahedrons, and truncated square cuboids. Transmission electron microscopy results suggest that the homogeneity of the driving force (supersaturation) for reduction of soluble Pt at the growing surface could dictate the transition from dendritic to faceted growth, and the competition between surface energy and interfacial kinetics of Pt reduction could govern the shape of faceted Pt nanoparticles.