Assisted Polyol Process Research Articles

Preparation of nanoparticles-assembled Cu2O microspheres by ultrasound- assisted polyol process and their adsorption performance

Preparation of nanoparticles-assembled Cu2O microspheres by ultrasound- assisted polyol process and their adsorption performance

Microwave assisted polyol process for time-saving synthesis of superparamagnetic nanoparticles and application in artificial mimic enzyme

A microwave assisted polyol process accomplished within 10 min was developed for synthesis of superparamagnetic Fe3O4 nanoparticles (MNPs) with well controlled size between 2 and 6 nm. Effects of reaction time and temperature on the size of the MNPs were investigated through transmission electronic microscope, x-ray diffraction pattern, thermogravimetic and magnetic analysis. The results indicates that longer reaction time or higher temperature lead to formation of MNPs with larger size. As a proof-of-concept, the MNPs were utilized as peroxidase and their activity was also investigated. Oxidation of typical substrate, 3, 3’, 5, 5’ -tetramethylbenzidine, can be proceeded by using the MNPs as artificial mimic enzyme. The MNPs display the maximal catalyzed activity under the optimum condition as pH = 3.5, 40 °C and concentration of TMB and H2O2 with 120 and 110 mmol·l−1, respectively. This work provides a new way for fast synthesis of MNPs, which are of potential application in artificial mimic enzyme.

Rapid microwave-assisted synthesis of Bi2Te3 nanoflakes as an efficient contrast agent for X-ray computed tomography

A one-pot microwave assisted polyol process is used to prepare bismuth telluride nanostructures as a potential contrast agent in X-ray computed tomography imaging. The effect of reaction time, reaction temperature and tannic acid as surface coating agent on the morphology of prepared bismuth telluride nanostructures is investigated. Nanoflakes with dimensions of about 200–250 nm and thickness of 50–60 nm are formed in the presence of tannic acid. The synthesis of Bi2Te3 with rhombohedral structure is confirmed via X-ray powder diffraction (XRD) analysis. Fourier transform infrared analysis (FTIR) demonstrates the presence of tannic acid on the surface of Bi2Te3 nanoflakes. Finally, the X-ray attenuation of prepared Bi2Te3 nanoflakes is higher than commercial contrast agent based on iodinated molecules (Iohexol) at the same concentrations for a broad range of X-ray photon energy.

Facile synthesis of highly conducting and mesoporous carbon aerogel as platinum support for PEM fuel cells

We report novel method for synthesis of carbon aerogel as platinum support for PEM fuel cells applications. The sol gel polymerization has been carried out using resorcinol and furfuraldehyde in non-aqueous medium followed by gelation at high pressure. This resulted in highly conducting and mesoporous carbon aerogel under ambient drying conditions. Platinum nano-particles are impregnated in the mesoporous carbon aerogel using microwave assisted polyol process. The support material and the catalyst are characterized by different analytical techniques like surface area analyzer, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Cyclic voltammetry and linear sweep voltammetry are used to evaluate the electro–catalytic activity of the Pt/carbon aerogel catalyst using rotating disk electrode technique. Well dispersed Pt nano-particles of size ∼3 nm on carbon aerogel showed good catalytic activity with onset potential of 964 mV and half wave potential of 814 mV towards oxygen reduction reaction kinetics. A membrane electrode assembly fabricated with the prepared Pt/carbon aerogel catalyst as a cathode and anode is tested in PEMFCs (H2O2) single cell, the power density of 536 mW cm−2 at 0.6 V is obtained at 60 °C under atmospheric pressure.

Determination of Ag+ and Cu2+ ions in mixture samples obtained in the microwave assisted polyol process by differential pulse anodic stripping voltammetry (DPASV) method

Abstract A simple and selective differential pulse anodic stripping voltammetry (DPASV) method for the determination of Ag+ and Cu2+ ions in mixture samples obtained in the microwave assisted polyol process was developed and validated. Analytical methods for the preparation of the reaction mixture for voltammetric analysis (dilute samples in the supporting electrolyte) were worked out and optimized. All measurements were conducted in three-electrode cell system equipped with glassy carbon electrode (GCE) as a working electrode, silver/silver chloride (Ag|AgCl|KCl(sat.)) as a reference and platinum wire as a auxiliary electrode. The optimal conditions for quantitative determination were obtained in an mixture Britton–Robinson buffer at pH 4.1 / ethylene glycol (100/1; v/v). The calibration curves of analysed compounds are linear within the range of concentration: 0.032 − 0.420 μg mL-1 and 0.075 − 0.960 μg mL-1 for Ag+ and Cu2+, respectively. Good linear behaviour over the investigated concentration ranges were observed with the values of r2 higher than 0.996 for the silver and cooper ions. The accuracy of analytical determinations ranged from 0.4 to 3.6%. The levels of analysed ions in the reaction mixture can be successfully determined using this developed method with no matrix effect.

Synthesis of Metal Doped ZnO Nanoclusters by Microwave Assisted Polyol Process

Synthesis of Metal Doped ZnO Nanoclusters by Microwave Assisted Polyol Process

Preparation of PtNi/C electrocatalysts for direct methanol fuel cell via pulse microwave assisted polyol method

PtNi/C nanoparticles with different atomic ratios of Pt/Ni were produced in pulse microwave assisted polyol process. Transmission electron microscopy (TEM) images show uniform morphology. X-ray diffraction( XRD) pattern plus energy dispersive X-ray (EDX) spectroscopy suggests pure composition. Cyclic voltammogram study reveals that PtNi/C nanoparticles synthesized in pulse microwave assisted polyol process have better catalytic activity for the oxidation of methanol to carbon dioxide than those synthesized in continuous process.

Three-dimensional lithium manganese phosphate microflowers for lithium-ion battery applications

The Polyvinylpyrrolidone (PVP)-assisted polyol process was employed for the synthesis of lithium manga- nese phosphate (LiMnPO4) microflowers as a cathode material for Li-ion battery applications. LiMnPO4 micro- flowers were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope- energy dispersion spectroscope, and impedance spectros- copy. The microflowers were highly porous with nanosized petals. CR2032 coin cells were fabricated using LiMnPO4 microflowers' sample and their battery characteristics were tested. The discharge capacity of LiMnPO4 microflowers was found to be 164 mAh g -1 at 0.1C. The observed high discharge capacity was attributed to the short diffusion length of Li-ion motion in the nanopetals of the LiMnPO4 microflowers.

Investigation on performance of Pd/Al2O3–C catalyst synthesized by microwave assisted polyol process for electrooxidation of formic acid

A Pd/Al2O3–C catalyst with α-Al2O3 and Vulcan XC-72 carbon black as a mixture support for direct formic acid fuel cell (DFAFC) has been prepared by a microwave-assisted polyol process for the first time. The as-prepared Pd/Al2O3–C catalysts with different mass ratios of α-Al2O3 to XC-72 carbon have been characterized by XRD, EDAX, XPS, TEM, HRTEM, and electrochemical measurements in this study. The results show that the activity of the catalyst with α-Al2O3 as the support is lower than that of the catalyst with carbon black as the support, owing to α-Al2O3 having poor electrical conductivity. However, the activity of the catalyst with α-Al2O3 and Vulcan XC-72 carbon black as a mixture support is evidently enhanced. The Pd/Al2O3–C catalyst with a mass ratio of α-Al2O3 to XC-72 carbon of 1 : 2 presents the narrowest particle size distribution on the surface of the mixture support, which exhibits the best activity and stability for formic acid electrooxidation among all the samples. Its current density of the positive anodic peak of formic acid electrooxidation is up to 36.97 mA cm−2. Pd/Al2O3–C catalyst with a suitable ratio of α-Al2O3 to XC-72 carbon shows a better catalytic activity for formic acid electrooxidation and a higher stability than Pd/C, resulting from the addition of α-Al2O3 improving its electrooxidation ability for formic acid due to an anti-corrosion property of α-Al2O3 and a metal–support interaction between the Pd nanoparticles and the α-Al2O3.

Characteristics of Pt, Pt-Ru and Pt-CeO_2 Catalysts Supported on Carbon Nanotubes for Methanol Fuel Cell

Nanosized Pt, Pt-Ru and Pt-<TEX>$CeO_2$</TEX> electrocatalysts supported on acid-treated carbon nanotube (CNT) were synthesized by microwave-assisted heating of polyol process using <TEX>$H_2Cl_6Pt{\cdot}6H_2O$</TEX>, <TEX>$RuCl_3$</TEX>, <TEX>$CeCl_3$</TEX> precursors, respectively, and were characterized by XRD and TEM. And then the electrochemical activity of methanol oxidation for catalyst/CNT nanocomposite electrodes was investigated. The microwave assisted polyol process produced the nano-sized crystalline catalysts particles on CNT. The size of Pt supported on CNT was 7~12 nm but it decreased to 3~5 nm in which 10wt% sodium acetate was added as a stabilizer during the polyol process. This fine Pt catalyst particles resulted in a higher current density for Pt/CNT electrode. It was also found that 10 nm size of PtRu alloys were formed by polyol process and the onset potential decreased with Ru addition. Cyclic voltammetry analysis revealed that the <TEX>$Pt_{75}Ru_{25}/CNT$</TEX> electrode had the highest electrochemical activity owing to a higher ratio of the forward to reverse anodic peak current. And the chronoamperemetry test showed that <TEX>$Pt_{75}Ru_{25}$</TEX> catalyst had a good catalyst stability. The activity of Pt was also found to be improved with the addition of <TEX>$CeO_2$</TEX>.

Microwave Assisted Synthesis of Nanocrystalline Fe-Phosphates Electrode Materials and Their Electrochemical Properties

LiFePO4 nanocrystalline particles were synthesized using microwave assisted polyol process within a fast reaction time of 20 minutes without any further heating as a post step. The synthesized LiFePO4 nanocrystalline particles showed mono-dispersed rod and orthorhombic-like shapes with a size of 60 approximately 180 nm. The refined X-ray diffraction pattern of the sample was indexed well to the olivine crystal structure (space group: Pnma) without any impurity phases. The LiFePO4 nanocrystalline particles show a capacity of 161 mAh/g in a voltage range of 2.5-4.2 V with a current density of 0.1 mA/cm2 without any observable capacity fading in extended cycles of 100th. A cyclic voltammetry analysis exhibits distinctly sharp peaks corresponding to the typical LiFePO4/FePO4 redox couples and demonstrates a good reversibility of the sample.

Facile Synthesis of Carbon-Supported IrxSey Chalcogenide Nanoparticles and Their Electrocatalytic Activity for the Oxygen Reduction Reaction

Vulcan XC-72R carbon-supported IrxSey chalcogenide catalysts with different Se/Ir atomic composition were synthesized via a microwave-assisted polyol process using H2IrCl6 and Na2SeO3 as the Ir and Se precursors. IrxSey chalcogenide catalysts were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The data were discussed with respect to the Se-free carbon-supported Ir nanoparticles prepared by the same microwave-assisted polyol process. The XRD results revealed that IrxSey chalcogenide catalysts showed characteristic reflections of cubic metallic iridium, and the average particle size increased with the increase of Se content in the chalcogenide catalysts. TEM images indicated that IrxSey chalcogenide catalysts were well dispersed on the surface of the carbon support with a narrow particle size distribution when y/x ≤ 1/3. When y = x, because of the particle agglomeration, we were not able to build particle size distribution and calculate the average particle size for Ir50Se50/C catalyst. Cyclic voltammogram (CV), rotating disk electrode (RDE) and single-cell measurements were conducted to evaluate the electrocatalytic activity of IrxSey chalcogenide catalysts. The CV results suggested that Se covered some surface area of Ir particles, and also, the surface properties of Ir particles were changed after Se modification. The RDE measurements were carried out with the absence/presence of methanol. In the absence of methanol, IrxSey/C catalysts showed a comparable oxygen reduction reaction (ORR) activity with Pt/C catalyst. However, in the presence of methanol, IrxSey/C catalysts showed a better ORR activity than Pt/C catalyst. The performance of the membrane electrode assembly (MEA) prepared with the most active Ir85Se15/C as the cathode catalyst in a single proton exchange membrane fuel cell (PEMFC) was also tested and achieved a maximum power density of 500 mW cm-2 at the current density of 1500 mA cm-2.

Synthesis, Dealloying, and ORR Electrocatalysis of PDDA-Stabilized Cu-Rich Pt Alloy Nanoparticles

We report on the polymeric surfactant-assisted synthesis and characterization of highly dispersed, uniformly alloyed Cu-rich bimetallic nanoparticles with Cu contents up to Cu for use as an oxygen reduction reaction (ORR) electrocatalyst at polymer electrolyte membrane fuel cells. Base-metal-rich Pt alloy particles are generally very difficult to prepare as a well-alloyed single-phase material with high dispersion using conventional liquid impregnation/reductive annealing routes. A comparison between the characteristics of alloy particle obtained from a poly(dimethyl-diallyl ammonium) chloride (PDDA) assisted polyol process and a conventional impregnation method shows that the polyol process is able to form single-phase nanoparticles with a very narrow particle size at temperatures below 200°C. We further investigated the electrochemical behavior of Cu-rich electrocatalysts. We demonstrate the formation of highly active ORR catalyst phases from a precursor by selective electrochemical dissolution (dealloying) of Cu. The dealloyed catalyst yields ORR surface-area-specific activities rivaling those of the Pt-rich state-of-the-art electrocatalysts. Based on the severe depletion in Cu near the surface combined with moderate surface area increases, we propose geometric rather than electronic or surface-area effects as the origin of the observed activity enhancement.