Pt Nanoparticles Research Articles

The influence of sulfonation level on the electrochemical characteristics of Pt/rSGO as electrocatalyst for proton exchange membrane fuels cells

The influences of sulfonation level on the electrochemical characteristics of reduced-sulfonated graphene oxide (rSGO) as catalyst support in proton exchange membrane fuel cells (PEMFCs) was investigated. SGO samples were synthesized by mild heating of an aqueous mixture of GO and sulfanilic acid. The sulfonation level of SGOs was varied by changing the weight percentage of sulfanilic acid. The SGO sample with the optimized electrochemical characteristics was converted to rSGO through a chemical reduction route. The morphological, physicochemical and electrochemical characteristics of the prepared SGO and rSGO samples were compared. Pt-decorated rSGO samples (Pt/rSGO) were prepared by electroless reduction of an aqueous mixture of SGO and Pt(NH3)4Cl2 using NaBH4 as a reducing agent. SEM analysis revealed that the prepared SGOs possess a more folded morphology compared to GO and that the sulfonated groups prevent the agglomeration of Pt nanoparticles (PtNPs) during the reduction process. The electrochemical characteristics of SGOs and the corresponding rSGO samples were improved by increasing the sulfonation level from 0 to 50 wt% and afterward a reverse trend was observed. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements revealed that Pt/rSGO samples comprising of 50 wt% sulfonated groups exhibit higher catalytic activity towards hydrogen adsorption/desorption (HAD) reactions compared to Pt/rGO. This was attributed to more uniform distribution of PtNPs and the enhanced triple phase boundaries in Pt/rSGOs.

Portable detection of serum HER-2 in breast cancer by a pressure-based platform.

A high serum HER-2 extracellular domain (sHER-2 ECD) level has a reverse association with tumor behaviors. In this study, a portable platform for the disease biomarker sHER-2 ECD detection has been established using a pressure-based bioassay. The pressure bioassay consists of a monoclonal antibody immobilized on an eight-well strip, the analyte HER-2, and another monoclonal antibody labeled with the Pt nanoparticles (PtNPs), which have the catalytic ability to decompose H2O2 into H2O and O2(g). The increased pressure due to O2(g) generation is measured by a hand-held pressure meter. A total of 34 serum samples were collected to validate the performance of the pressure bioassay. The results showed that the pressure bioassay platform of HER-2 had a dynamic range from 2 to 50ng/mL with a limit of detection (LOD) of 2ng/mL, which was consistent with the ELISA result. In the real serum samples, there was a significant correlation between sHER-2 ECD level and several clinicopathological parameters, especially tissue HER-2 status. Furthermore, the sHER-2 ECD level was found to decrease after targeted therapy in a patient with tHER-2 positive. Overall, this bioassay can facilitate breast cancer diagnosis and prognosis in clinical scenarios and resource-limited areas.

Platinum clusters deposited on maghemite applied to preferential oxidation of CO under hydrogen rich conditions (PROX-CO)

Pt-FeOx catalysts have been showing excellent performance on several catalytic reactions involving bifunctional mechanisms. Here, Chini’s carbonyl oligomers were used as a precursor to obtain Pt nanoparticles (Pt-NP) anchored on maghemite, γ-Fe2O3. The Pt-NP diameter were in the range of 1.5 nm and the catalysts were active in preferential oxidation of CO under H2 rich atmosphere (PROX-CO reaction), without pretreatments. The catalytic behavior after the first heating ramp, under consecutive cycles, improved, almost triplicating the CO conversion at lower temperatures, around 353 K. A detailed characterization was performed and showed that the support, due the presence of Pt-NP, went through a phase transformation under reaction conditions, from γ-Fe2O3 (Fe(III)) to Fe3O4 (Fe(II,III)), indicating that the presence of Fe(II) species are stabilized under PROX-CO and contribute to overall performance of the catalyst. As comparison, the bare Fe2O3 support as well as a catalyst prepared by depositing the same Chini’s carbonyl oligomers on SiO2 support showed negligible activity at these low temperatures.

Ultrafast electrochemical deposition of core shell metal nanoparticles on TiO2 nanotubes for electrocatalytic applications

In this work, we report a rapid and reliable electrochemical synthetic method for decoration of core–shell nanoparticles of Pt and Au over titania nanotubes (TNTs). The decoration was achieved in an ultrafast manner within a span of 60 s without using any reducing agents or any use of further thermal of chemical treatments. The successful formation of double shell nanoparticles such as AuPt@Pt-TNT, PtAu@Au-TNT and single shell nanoparticles such as Pt@Au-TNT was characterized by using transmission electron microscopy (TEM), x-ray photo electron spectroscopy (XPS), energy dispersive x-ray spectroscopy (EDS) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) techniques. The synthesized core–shell nanoparticles showed good electrocatalytic activity towards aqueous and non-aqueous ORR applications.

Methanol oxidation reaction on Pt based electrocatalysts modified ultramicroelectrode (UME): Novel electrochemical method for monitoring rate of CO adsorption

Novel fast scan cyclic voltammetry (FSCV) based method has been developed to study methanol oxidation reaction on Pt nanoparticles (PtNPs) based catalysts. To support the cyclic voltammetry measurements at higher scan rates, micron-sized electrode geometries viz. PtNPs loaded on the single strand of carbon fiber (SSCF) and PtNPs decorated multiwalled carbon nanotubes (MWCNTs), loaded on commercial ultramicroelectrode (UME) have been employed. Deconvolution of the voltammograms obtained during methanol oxidation revealed three major anodic peaks. These peaks have been plausibly attributed to the electron transfer processes viz. methanol oxidation into CO/other intermediates, oxidation of these intermediates into CO2 and adsorption of un-oxidized CO on the catalyst surface. The peaks due to CO adsorption have been elucidated as a function of scan rates. The area under the peak as a function of time has been correlated to the rate of CO adsorption on these catalysts. The average rate of CO adsorption in methanol oxidation at Pt-SSCF and Pt-MWCNTs/UME are estimated to be 1.08 × 10−8 mol cm−2 s−1 and 13.5 × 10−8 mol cm−2 s−1 respectively. This novel method is proposed to generalize to any electrocatalysts of interest.

Investigation of charge recombination lifetime in γ-WO3 films modified with Ag0 and Pt0 nanoparticles and its influence on photocurrent density

In this communication, we report the growth of pure gamma-phase tungsten oxide (γ-WO3) films on a conducting substrate (fluorine-doped tin oxide), followed by heat treatment at 500 °C for 2 h, and finally modification with either silver (Ag0) or platinum (Pt0) metallic nanoparticles. These γ-WO3 thin films can be obtained from a tungsten citrate solution by a drop-coating method, and their surfaces are modified with Ag0 and Pt0 nanoparticles by photoreduction. X-ray diffraction analysis indicates that all the thin films have a monoclinic structure. Field emission-scanning electron microscopy analysis reveals large and fine grains for pure γ-WO3 film and modified WO3 films, respectively, with an average grain size of ~ 48 nm and thickness of ~ 986 nm. Finally, an enhancement in photoelectrochemical performance by a factor of ~ 2.5 is noted to modified γ-WO3 films, which is attributed to superior electron-hole charge recombination lifetime under polychromatic irradiation. It is observed that, even under bias, an exponential reduction in photocurrent intensity is associated with charge recombination instead of mass transport conditions like diffusion.

Solution-Plasma-Assisted Bimetallic Oxide Alloy Nanoparticles of Pt and Pd Embedded within Two-Dimensional Ti3C2Tx Nanosheets as Highly Active Electrocatalysts for Overall Water Splitting

Exploiting high-efficiency and low-cost bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) has been actively encouraged because of their potential applications in the field of clean energy. In this paper, we reported a novel electrocatalyst based on an exfoliated two-dimensional (2D) MXene (Ti3C2T x) loaded with bimetallic oxide alloy nanoparticles (NPs) of Pt and Pd (represented by PtO aPdO bNPs@Ti3C2T x), which was synthesized via solution plasma (SP) modification. The prepared materials were then utilized as highly efficient bifunctional electrocatalysts toward the HER and OER in alkaline solution. At a high plasma input power (200 W), bimetallic oxide alloy nanoparticles of Pt and Pd or nanoclusters with different metallic valence states were deposited onto the Ti3C2T x nanosheets. Because of the synergism of the noble-metal NPs and the Ti3C2T x nanosheets, the electrocatalytic results revealed that the as-prepared PtO aPdO bNPs@Ti3C2T x nanosheets under the plasma input power of 200 W for 3 min only required a low overpotential to attain 10 mA cm-2 for the HER (-26.5mV) in 0.5 M H2SO4 solution and OER (1.54 V) in 0.1 M KOH solution. Moreover, water electrolysis using this catalyst achieved a water splitting current density of 10 mA cm-2 at a low cell voltage of 1.53 V in 1.0 M KOH solution. These results suggested that the hybridization of the extremely low usage of PtO a/PdO b NPs (1.07 μg cm-2) and Ti3C2T x nanosheets by SP will expand the applications of other clean energy reactions to achieve sustainable energy.

Combining SAXS and XAS To Study the Operando Degradation of Carbon-Supported Pt-Nanoparticle Fuel Cell Catalysts

In the last two decades, small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS) have evolved into two well-established techniques capable of providing complementary and operando information about a sample’s morphology and composition, respectively. Considering that operation conditions can often lead to simultaneous and related changes in a catalyst’s speciation and shape, herein we introduce a setup that combines SAXS and XAS in a configuration that allows optimum acquisition and corresponding data quality for both techniques. To determine the reliability of this setup, the latter was used to study the operando degradation of two carbon-supported Pt-nanoparticle (Pt/C) catalysts customarily used in polymer electrolyte fuel cells. The model used for the fitting of the SAXS curves unveiled the fractal nature of the Pt/C-electrodes and their evolution during the operando tests, and both X-ray techniques were complemented with control, ex situ transmission electron microscopy, and standa...

Highly sensitive electrochemiluminescence immunosensor based on ABEI/H2O2 system with PFO dots as enhancer for detection of kidney injury molecule-1

In this work, poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) dots is discovered to display an appealing dual enhancement effect for the electrochemiluminescence (ECL) system of N-(aminobutyl)-N-(ethylisoluminol)/hydrogen peroxide (ABEI/H2O2), which not only enhances the ECL intensity of ABEI but also catalyzes decomposition of H2O2 to further amplify the ECL signal of ABEI. Owing to the electronegative property of PFO dots, electropositive ABEI-PEI as ECL reagent could be adsorbed on their surface and thus form a novel luminescence emitter (ABEI-PEI-PFO dots) with high ECL efficiency based on electrostatic attraction. Meanwhile, the water solubility and stability of this emitter are improved in virtue of the amine-rich property of ECL reagent (ABEI-PEI), which could increase the luminous efficiency of ECL reaction in aqueous solution. To increase the electron transfer efficiency, Pt nanoparticles (PtNPs) supported on reduced graphene oxide nanosheets (RGOs) via a onepot synthetic strategy are chosen as immobilizing platform for the ECL emitter (ABEI-PEI-PFO dots). Herein, the obtained dual-amplifed ABEI-PEI-PFO dots-RGOs/PtNPs complex is served as an ideal nanocarrier to capture detection antibody (Ab2). According to sandwiched immunoreaction, a highly sensitive ECL immunosensor is constructed for the detection of kidney injury molecule-1 (KIM-1) with a linearity from 50 fg mL−1 to 1 ng mL−1 and a detection limit of 16.7 fg mL−1. The developed ECL emitter combining dual amplified property for signal enhancement purpose would provide new thought and potential for sensitive bioanalysis and clinical application.

Hierarchical carbon composite nanofibrous electrode material for high-performance aqueous supercapacitors

In this research, a hierarchical carbon composite nanomaterial ECNFs/PtNPs, which is composed of electrospun carbon nanofibers (ECNFs) with both individual and agglomerate of Pt nanoparticles (PtNPs) homogeneously dispersed all over the ECNF surface, was prepared by successive electrospinning, carbonization, and controlled growth of the PtNPs. Morphology and structure of ECNFs and ECNFs/PtNPs with a variety of amount of PtNPs were characterized by scanning electron microscope, x-ray diffraction and BET surface area analysis. The ECNFs/PtNPs was evaluated as electrode material for supercapacitor with aqueous electrolyte. The results indicated that Pt nanoparticles on surface of ECNFs drastically increased specific capacitance as well as potential energy density of the electrode material by 50 times to 226 F g−1 and 20 W h kg−1, respectively, at 0.14 g/cm2 Pt loading with 6M KOH aqueous electrolyte. This is ascribed to the highly catalytic activity of PtNPs in the hierarchical nanostructure for oxygen reduction reaction in alkali aqueous electrolyte, which leads to significant pseudocapacitance. This research discloses a novel nanofibrous electrode material from electrospinning with great potential for designing high-performance supercapacitors using aqueous electrolyte.

A nonenzymatic electrochemical H2O2 sensor based on macroporous carbon/polymer foam/PtNPs electrode

Herein, a nonenzymatic electrochemical H2O2 sensor was developed based on Pt nanoparticles (PtNPs)/Schiff base foam (SBF)/three-dimensional macroporous kenaf stem-derived carbon (TMKSDC). The SBF composed of thin SB layers with single atomic thickness was firstly grown on TMKSDC as a supporting matrix via hydrazine anhydrous–terephthalaldehyde amino-aldehyde condensation reaction. Subsequently, lots of electroactive nanosized PtNPs were electrodeposited on SBF/TMKSDC to form PtNPs/SBF/TMKSDC integrated electrode. The surface morphology and pore feature of PtNPs/SBF/TMKSDC integrated electrode were explored by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, atomic force microscope and N2 adsorption/desorption isotherms. Cyclic voltammetry and chronopotentiogram methods were used to study the electrochemical properties of PtNPs/SBF/TMKSDC integrated electrode for H2O2 sensing. Results showed that the nonenzymatic electrochemical H2O2 sensor based on PtNPs/SBF/TMKSDC integrated electrode had a good performance. The detection limit was about 0.022 μM, and the linear range was 0.065 μM–0.45 mM with a sensitivity of 760 μA mM−1 cm−2 and 0.45–1.775 mM with a sensitivity of 610 μA mM−1 cm−2. The good performances originated from the hierarchically porous structures, the large specific surface of PtNPs/SBF/TMKSDC and the super catalytic activity and distribution of nanosized PtNPs. It was noteworthy that the PtNPs/SBF/TMKSDC integrated electrode might also be applied in other fields.

Detecting decompositions of sulfur hexafluoride using reduced graphene oxide decorated with Pt nanoparticles

The resistance-typed gas sensing material of Pt nanoparticles (PtNPs) decorated reduced graphene oxide (RGO) synthesized by one-step chemical reduction for the detection of four types of SF6 decompositions was explored. The PtNPs disperse uniformly on RGO with particle size near 2–4 nm and a small number of particles are larger than 10 nm. Gas sensing tests suggest that the introduction of PtNPs increases the response to SO2, SOF2 and H2S compared to pure RGO and PtNPs-RGO experiences resistance reducing in SO2 and SOF2 while presenting the opposite case in H2S. Elevating the temperature enhances the recovery properties to SO2 and H2S but lowers the sensitivity. The sensing mechanism for Pt-RGO in low oxygen and water environment depends mainly on the charge transfer between gas and adsorbent and the solvent on material surface. The work provides experimental investigation of Pt-RGO to detect SF6 decompositions.

The Oxygen Reduction Reaction Activity of Pt/Carbon-Sphere Formed By Silica Bead Core and Graphene Oxide Wall

Polymer electrolyte fuel cell (PEFC) is expected to one of the candidates for automobile and residential power sources. In PEFC, the carbon-supported platinum-based nanoparticle is generally used as the electrocatalyst. The catalyst support plays the two important roles of the electron conduction between Pt nanoparticles (PtNPs) and gas diffusion layer and the homogeneous dispersion of PtNPs by its high surface area. Activated carbon, which is cheap and has high surface area, employed as the catalyst support in general. However, the activated carbon is corroded at the startup/shutdown of PEFC which is reaching the high potential region. This carbon corrosion leads to detachment and aggregation of the PtNPs, as a result, produces to drastically degradation of the electrocatalyst. Another problem is that all of the PtNPs on the activated carbon cannot be using completely since the complex pores in the activated carbon accommodate of the PtNPs partially. In order to the realization of wide-spread commercialization of PEFC, the build-up of the low-cost system is necessary by improvement of the catalytic durability and the Pt utilization. Recently, graphite oxide (GO) has been reported as a high corrosion resistant catalyst support to PtNPs. [1-2] PtNPs is highly dispersed on the GO in order to the electrostatic interaction between Pt complex and surface function group of GO. However, GO supported PtNPs catalyst has the high mass diffusion resistance and the low Pt utilization. This reason is thought that the majority of PtNPs would deposit between the GO layers which are poor the substance diffusion. We thought that the key point is a shape of GO nanosheets (GOns). To expose all of the PtNPs, the ordered structure by restacked GOns, such as sphere shape which has the higher substance diffusion, should be constructed. Therefore, we have been developing a new catalyst that PtNPs are supported on the carbon-sphere formed by GOns. Past carbon-sphere supported Pt (Pt/CS) catalyst had a problem with its electron conductivity. In the reduction step of Pt complex, PMMA sphere used as the core of CS was melting. And its melt was covering on the many PtNPs. This means that the number of active surface of PtNPs and the electron conductivity of catalyst were decreased because melt species were nonconductive. In this study, the silica beads were employed as the new core material for the carbon-sphere composed by GOns wall in order to prepare the Pt/CS. And the relationship between its ORR activity and electroconductivity was investigated. GO was synthesized by typical Hummers method. GOns colloid solution was obtained by shaking GO with 0.01 wt% TBAOH aqueous solution. Silica beads were dispersed in 0.01 wt% polyvinyl alcohol copolymer aqueous solution and washed with ultrapure water. After that, their beads were mixed with GOns colloid solution and washed. Pt/CS was synthesized by the impregnation method. A pH of a Pt complex ethanol solution was adjusted to about 4 by NaOH aqueous solution. After that, the solution was added to a carbon sphere ethanol dispersion. And then, this mixed solution was dried at 60ºC. An obtained powder was thermally treated at 200 ºC under the hydrogen flow conditions. Its morphology, crystalline structure, and electronic state were observed SEM, TEM, XRD, and XPS, respectively. The electrochemical measurement was conducted by the rotating disk electrode (RDE) method at 60°C in 0.1 M HClO4. The mass loading of Pt on test electrode was 17.3 µg cm-2. The counter electrode was a carbon fiber and the reference electrode was Ag/AgCl. The shape of CS has been kept sphere after the supporting treatments of PtNPs. However, the large size of silica beads was partially covered with GOns, not completely. In contrast, small particles were covered all over a surface by GOns. From XRD results, broad and weak peaks were observed at ~40° and ~45° which are attributed to Pt (111) and Pt (200) phases. The mass activity of Pt/CS was low value. However, this value was drastically improved by the addition of the ketjen black as the conductivity agent. Therefore, partially covered CS by GOns may inhibit the electron conductivity, and lead to low mass activity of ORR. Now, full covering CS with GOns is preparing. Using this CS as the catalyst support is reformed the electron conductivity, and expected enhancement of ORR activity. Its physical property and ORR activity will be reported at the venue. Reference [1] L. Xin, et al., ACS Catal., 6, 2642-2653 (2016). [2] J. Lu, X. Liu, Y. Zhang, Y. Liu, M. Li, X. Lu, Anal. Methods, 8, 816-823 (2016).

(Invited) Platinum Nanotubes and Platinum Thin Layers on Nanowires As Electrocatalysts

PEMFCs are attractive for powering cars because of their high efficiency, high power density, and zero emission. The biggest barrier to the widespread deployment of PEMFC cars has been the cost and durability of the Pt catalysts. Early Pt catalysts were large Pt particles that had high specific activity and durability, but were clearly not economical due to the very low specific surface area. To develop an economical Pt catalyst the effort has been focused on Pt nanoparticles (PtNP). To increase mass activity, the ultimate measure of cost, the prevailing wisdom for a long period of time was to increase specific surface area by reducing the diameter of the PtNP. However as the diameter of PtNP decreases the specific activity also reduces, leading to unchanged or even lower mass activity. Small PtNPs are also not durable due to dissolution, aggregation and Oswald ripening15. To overcome this difficult tradeoff between high specific activity-low specific area (as in Pt macrowires and macroparticles) and low specific activity -high specific area (as in PtNP of 2-3 nm diameter), we have been working on the concept of Pt nanotubes (PtNTs) and their derivatives that can exhibit the favorable features of the Pt macrowires/macroparticles (high specific activity and durability) and the PtNPs (high specific activity) in the same structure15. We later made porous PtNTs to increase the Pt utilization17; replaced the Ag nanowire (AgNW) template15 with CuNWs to reduce cost18 , 19; and synthesized Pt thin layer on CuNWs (Pt/CuNWs) to improve mass activity further.18 , 19

Synthesis of Pt nanoparticles as catalysts of oxygen reduction with microbubble-assisted low-voltage and low-frequency solution plasma processing

In the preparation of metallic nanoparticles by conventional solution plasma (SP) techniques, unstable plasma emission becomes an issue when the voltage and frequency of the waves applied between two electrodes placed in solution are lowered to avoid the boiling of the solution. In this study, we confirm that, in the presence of microbubbles, plasma is generated stably at low voltage (440 V) and low frequency (50–100 Hz) and small-size (≤10 nm) Pt nanoparticles (PtNPs) are synthesized in succession using a flow cell. The smallest PtNPs, ∼3.3 nm in diameter, are obtained using half-wave rectification, a tungsten wire anode, and a platinum wire cathode. The PtNPs are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimeter-differential thermal analysis. The oxygen reduction reaction (ORR) is investigated in 0.1 M HClO4 solution on carbon-supported PtNPs using a rotating ring-disk electrode. The catalytic activities per initial electrochemical active surface area of the carbon-supported PtNPs synthesized employing the low-voltage, low-frequency (LVLF)–SP technique is higher than that of the commercially available 20 wt% Pt on Vulcan XC-72R. These results indicate that the LVLF-SP technique is a promising approach to producing carbon-supported PtNPs that catalyze ORR with low energy consumption.

Highly stable Ti3C2Tx (MXene)/Pt nanoparticles-modified glassy carbon electrode for H2O2 and small molecules sensing applications

Electrochemical performance of a 2D Ti3C2Tx (MXene, where T: O, OH, F) sheets modified with Pt nanoparticles (PtNPs) was investigated. The results showed that Ti3C2Tx/PtNP nanocomposite deposited on the surface of GCE showed much better and stable redox behavior in an anodic potential window as compared to the GCE modified with pristine Ti3C2Tx MXene. For example, the H2O2 sensor of Ti3C2Tx/PtNP on GCE offered LOD of 448 nM with a potential at which reduction starts of ∼+250 mV (vs. Ag/AgCl) in comparison to values of 883 μM and ∼−160 mV observed for Ti3C2Tx modified GCE. Moreover, the Ti3C2Tx/PtNP sensor could detect small redox molecules such as ascorbic acid (AA), dopamine (DA), uric acid (UA) and acetaminophen (APAP) at a potential higher than +250 mV with high selectivity and LOD down to nM level. We proved that selectivity of detection of such molecules (AA, DA, UA and APAP) could be modulated to high extent using external membranes.

Photocatalytic hydrogen evolution systems constructed in cross-linked porous protein crystals

Cross-linked hen egg white lysozyme crystals (CL-HEWL) have been employed as supports to construct heterogeneous catalysts for photocatalytic hydrogen (H2) evolution, where rose bengal (RB) and Pt nanoparticles (PtNPs) acted as a photosensitizer and H2-evolution catalysts, respectively. Single-crystal X-ray structure analyses of the CL-HEWL immobilizing a precursor for PtNPs suggested that a coordination site of the precursor locates in immediate proximity to potential adsorption sites for RB. The accumulation of the components facilitated photo-induced electron transfer, resulting in efficient H2 evolution. These results suggest that porous protein crystals are promising platforms to periodically and rationally accumulate catalytic components by using molecular interactions.

Structure Sensitivity of Acrolein Hydrogenation by Platinum Nanoparticles on BaxSr1−xTiO3 Nanocuboids

AbstractThe structure sensitivity of Pt nanoparticles (PtN) for gas‐phase acrolein (AC) hydrogenation was probed for PtN on BaxSr1−xTiO3 nanocuboid supports with (0 0 1) facets in a combined theoretical and experimental study. The in situ selectivity for allyl alcohol increased with the increase of the Sr concentration in the support, which corresponds to modifications in the stable Winterbottom shape and lattice strain of the Pt nanoparticles as a result of the interfacial energy between Pt and the BaxSr1−xTiO3 supports. “Local model” nanofacets of the Pt surface, edge, and corner morphologies were developed as compact representations of adsorption and reaction sites. DFT was used as the primary modeling tool for the equilibrium adsorption states. We argue that adsorption on edge sites is critically important for the overall allyl alcohol selectivity of PtN catalysts. A simple model was developed to represent PtN strain effects caused by its interaction with the substrate. Bader topological atom, spherical volume averaging charge, and modified bond valence sum analyses were used to understand the bonding structure. Density of states analysis was performed for the structures of PtN, adsorbed AC, and intermediate products to examine adsorbate–particle interactions. The simulated hydrogenation of AC on PtN nanofacets was compared to the in situ hydrogenation of AC by PtN on BaxSr1−xTiO3 to examine the effects of facet, edge, and corner sites on the overall selectivity.

Fabrication and Characterization of PZN-4.5PT Inorganic Perovskites Nanoparticles Thin Films Deposited on P-Type Silicon Substrate

This work involves an investigation of nanostructures, microelectronic properties and domain engineering of nanoparticles thin layers of Pb(Zn1/ 3Nb2/3)O3-PbTiO3 (PZN-PT) ferroelectric single crystals deposited on nanostructured silicon substrate. In this study, devices made from PZN-4.5PT nanoparticles thin films successfully deposited on silicon substrate have been studied and discussed. SEM images show the formation of local black circles and hexagonal shapes probably due to the nucleation of a new Si-gel component or phase induced by annealing. Micro Xray Fluorescence mapping shows that the high values of Si and B atoms (≅7 and 4 normalized unit respectively) can be explained by the fact that the substrate is p-type silicon. The most interesting result of optical measurements is the very good absorption for all the thin films in UV, Visible and NIR regions with values from 70% to 90% in UV, from 75% to 93% in Visible and NIR. Tauc plots present particularities (rarely encountered behavior) with different segments or absorption changes showing the presence of multiple band gaps coming from the heterogeneity of the thin films (nanowires, gel and nanoparticles). Their values are 1.9 and 2.8 eV for DKRN-Gel, 2.1 and 3.1 eV for DKRN-UD and 2.1 and 3.2 eV for DKRN-D) corresponding respectively to the band gap of nanowires and that of the gel while the last ones correspond to the undoped and doped nanoparticles (3.1 and 3.2 eV respectively).

Enhanced electrocatalytic performance of platinum nanoparticles on thiolated polyaniline-multiwalled carbon nanotubes for methanol oxidation.

Pt nanoparticles (PtNPs) well-dispersed on thiolated polyaniline (TPANI)-multiwalled carbon nanotubes (MWCNTs) were prepared for enhanced electrocatalytic oxidation of methanol in acidic media. Briefly, the preparation of nanocomposites was carried out via microwave-assisted thiol–ene reaction of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) with oxidized PANI, which was synthesized in the presence of MWCNTs, yielding TPANI-MWCNTs; then, PtNPs were deposited on TPANI-MWCNTs by a microwave-assisted method to obtain PtNPs/TPANI-MWCNT nanohybrids. Fourier transform infrared spectroscopy, cyclic voltammetry (CV), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and inductively coupled plasma-atom emission spectroscopy were used to study relevant nanohybrid properties. TEM showed that PtNPs were well dispersed on TPANI-MWCNTs. TGA showed that PtNPs/TPANI-MWCNTs exhibited better thermal stability than PtNPs/TPANI-MWCNTs and PtNPs/MWCNTs. CV studies showed that PtNPs/TPANI-MWCNT-modified glassy carbon electrode (GCE) exhibited a larger electrochemically active surface area and higher electrocatalytic performance toward methanol electro-oxidation compared with those of PtNPs/PANI-MWCNTs/GCE and PtNPs/MWCNTs/GCE. Also, the PtNPs/TPANI-MWCNTs/GCE electrode possessed high stability and maintained 86% of its initial catalytic activity after 1000-cycle CV in 1.0 M CH3OH + 0.5 M H2SO4.