Bimetallic alloy Pt/Ag nanoparticles with enhanced catalytic activity for formic acid oxidation

Here, we report the synthesis of Pt/Ag bimetallic alloy catalyst through combining the ion implantation and electrodeposition method. Ag nanoparticles are employed as the seeds for the growth of Pt nanoparticles. Pt/Ag alloy catalyst demonstrates much higher catalytic activity than pure Pt catalyst, which is about three times more active on the basis of equivalent Pt electrochemically active surface area than that of the pure Pt catalyst. The ion implantation of Ag efficiently enhances the catalytic activity of Pt catalyst for formic acid oxidation.     

Photothermally enhanced catalytic activity of partially aggregated gold nanoparticles

In the present study, a facile, rapid, and environmentally friendly method was used for the preparation of metal oxide nanoparticles in an ionic liquid medium. This technique involves mixing and heating the corresponding powder material (cadmium oxide, anatase, and hematite) and the selected ionic liquid (trihexyl(tetradecyl)phosphonium chloride, [P_6,6,6,14]Cl), without any other precursors or solvents. The confirmation of the existence of nanoparticles in the ionic liquid was carried out using UV?CVis absorption spectroscopy, and its concentration was determined by X-ray fluorescence. In order to analyze the shape and size distribution, transmission electron microscopy and a ZetaSizer (DLS technique) were used; finding out that the size of the hematite nanoparticles was 10?C55?nm. Nevertheless, for the cadmium oxide and the anatase nanoparticles, the size was between 2 and 15?nm. The composition of the prepared nanoparticles was studied by Raman spectroscopy. The structure of solids did not suffer any modification in their transformation to the nanoscale, as concluded from the X-ray powder diffraction analysis.     

Synthesis of graphene oxide sheets decorated by silver nanoparticles in organic phase and their catalytic activity

The graphene oxide(GO) sheets decorated by Ag nanoparticles were prepared using a liquid–liquid two-phase method at the room temperature. The synthesized samples existed in the organic phase and were characterized by X-ray diffraction, transmission electron microscopy, UV–vis spectroscopy and Raman spectra. The results demonstrate that these silver-nanoparticles with diameter of about 10 nm assembled on graphene oxide sheets are flexible and can form stable suspensions in organic phase. Raman signals of graphene oxide sheets are increased by the attached silver nanoparticles, displaying higher surface-enhanced Raman scattering activity. Furthermore, Ag/GO are found to serve as effective catalysts to activate the reduction of 4-nitrophenol (4NP) in the presence of NaBH₄.     

Fabrication of bimetallic Pt/Pd nanoparticles on 2-thiolbenzimidazole functionalized reduced graphene oxide for methanol oxidation

In this study, an electrocatalyst based on 2-thiolbenzimidazole (TBI) functionalized reduced graphene oxide (rGO) with platinum and palladium nanoparticles (Pt-PdNPs) was synthesized. The successful synthesis of nanomaterials and the prepared glassy carbon electrode (GCE) surfaces were confirmed by transmission electron microscope, X-ray photo electron spectroscopy, scanning electron microscope, electrochemical impedance spectroscopy and X-ray diffraction method. The effective surface areas of TBIrGO/GCE, PdNPs/TBIrGO/GCE, PtNPs/TBIrGO/GCE and Pt-PdNPs/TBIrGO/GCE were calculated to be 324, 578, 667 and 1189 cm²/mg, respectively. According to the results, the electrochemical surface area of the Pt-PdNPs/TBIrGO is 3.67, 2.06 and 1.78 times higher than those of TBIrGO, PdNPs/TBIrGO and PtNPs/TBIrGO, respectively. The Pt-PdNPs/TBIrGO/GCE also exhibited higher peak current for methanol oxidation than those of comparable TBIrGO/GCE, PdNPs/TBIrGO/GCE, PtNPs/TBIrGO/GCE modified GCEs, thus providing evidence for its higher electro-catalytic activity.     

Formation of polyhedral ceria nanoparticles with enhanced catalytic CO oxidation activity in thermal plasma via a hydrogen mediated shape control mechanism

Ceria nanoparticles with well defined facets are prepared in argon–hydrogen thermal plasma followed by controlled oxidation. With increasing hydrogen fraction in the plasma, a clear sphere-to-polyhedron shape transition is observed. The heat released during the hydrogenation of cerium, which significantly enhances the species mobility on the surface, favors the growth of well defined facets. The polyhedron ceria nanoparticles, though lower in specific surface area, exhibit superior catalytic performance for CO oxidation over the round particles, which is attributed to the higher density of the reactive {200} and {220} facets on the surface. The hydrogen mediated shape control mechanism provides new insights into the shape control of nanoparticles during thermal plasma processing.     

Electrochemical oxidation of methanol on Pt nanoparticles composited MnO2 nanowire arrayed electrode

By use of the membrane-template synthesis route, MnO₂ nanowire arrayed electrodes are successfully synthesized by means of the anodic deposition technique. The Pt nanoparticles composited MnO₂ nanowire arrayed electrodes (PME) are obtained through depositing Pt on MnO₂ nanowire arrayed electrode by cathode deposition technique. For comparison of electrochemical performance, Pt nanowire arrayed electrodes which have the same amount of Pt with PME are also prepared. The electro-oxidation of methanol on PME and Pt nanowire arrayed electrodes is investigated at room temperature by cyclic voltammetry, which show that about 110 mV decreased overpotential and 2.1-fold enhanced votammetric current are achieved on PME. The chronoamperometry result demonstrates that the resistance to carbon monoxide for PME is improved.     

Electrochemical codeposition of Pt/graphene catalyst for improved methanol oxidation

Pt/graphene electrocatalyst was uniformly deposited on a glassy carbon substrate using a pulsed galvanostatic electrodeposition method, which facilitated the simultaneous electrochemical reduction of graphene oxide and formation of Pt nanoparticles. Compared to the commercial carbon-supported Pt electrocatalyst, the electrochemically reduced Pt/graphene (Pt/ERG) catalyst exhibited improved electrocatalytic activity for methanol oxidation due to the synergistic effects of an increase in the number of catalytic reaction sites and an enhancement of the charge transfer rate.     

One-pot synthesis of one-dimensional array Pt nanoparticles on carbon nanotubes via a facile microwave polyol method

High-density attachment and one-dimensional array Pt nanoparticles (NPs) on carbon nanotubes (CNTs) to generate Pt/CNTs heterostructures are obtained via one-pot microwave polyol method. The morphology, composition of as-obtained Pt/CNTs heterostructures is characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD). The Raman spectrum and Fourier transform infrared (FTIR) spectrum show the introduction of defects or functional groups on CNTs surface, which are crucial factors to assist the nucleation and growth of Pt NPs along the skeleton of CNTs.     

Electrodeposition of platinum nanoclusters on type I collagen modified electrode and its electrocatalytic activity for methanol oxidation

We firstly reported a novel polymer matrix fabricated by type I collagen and polymers, and this matrix can be used as nanoreactors for electrodepositing platinum nanoclusters (PNCs). The type I collagen film has a significant effect on the growth of PNCs. The size of the platinum nanoparticles could be readily tuned by adjusting deposition time, potential and the concentration of electrolyte, which have been verified by field-emitted scanning electron microscopy (FE-SEM). Furthermore, cyclic voltammetry (CV) has demonstrated that the as-prepared PNCs can catalyze methanol directly with higher activity than that prepared on PSS/PDDA film, and with better tolerance to poisoning than the commercial E-TEK catalyst. The collagen-polymer matrix can be used as a general reactor to electrodeposit other metal nanostructures.     

Fabrication of silver nanoparticles in a continuous flow,low temperature microwave-assisted polyol process

The performed experiments showed that continuous microwave-assisted polyol synthesis at about 70 °C is a viable process to give silver nanoparticles with a narrow size distribution in bulk amounts. The increase of silver precursor concentration in reaction system from 0.0097 to 0.0389 M resulted in the formation of fine nanoparticles 5–10 nm in size, in addition to the larger ones 30–100 nm, and that changed the pattern of particle size distribution from monomodal to bimodal. The effect of specific process variables was found to be the same in the continuous process as in batch operation. An aqueous glycerol solution was found suitable for use as both solvent and reducing agent.     

Carbon encapsulated nickel nanoparticles synthesized by a modified alcohol catalytic chemical vapor deposition method

In this work, a simple and cost-efficient method was demonstrated for the production of carbon encapsulated nickel nanoparticles (CENPs). The CENPs were synthesized from nickel oxide by a modified alcohol catalytic chemical vapor deposition method at atmospheric pressure. Structural characterizations using scanning electron microscopy, transmission electron microscopy and X-ray diffraction indicated that the Ni-core mean diameter and the graphite-layer mean thickness were 98 ± 31 nm and 65 ± 35 nm, respectively. Room temperature magnetization results showed a ferromagnetic behavior of the CENPs, in which the saturation magnetization decreased with decreasing the Ni-to-C ratio whereas the coercivity increased with decreasing the Ni-core diameter.     

Electrocatalytic oxidation of methanol on Pt catalyst supported on nitrogen-doped graphene induced by hydrazine reduction

Hydrazine is often used to reduce graphene oxide (GO) to produce graphene. Recent observations suggested that when hydrazine is used to reduce GO, the resulting reduced graphene actually contains certain amounts of nitrogen dopants, which may influence the properties of the obtained material, and in some cases may be deployed for beneficial advantage. In this work, we prepared graphene oxide by the chemical oxidation method, then used either hydrazine or sodium borohydride (as a control) to reduce the graphene oxide to graphene and to explore the nature of the nitrogen functionalities introduced by hydrazine reduction. Pt nanoparticles were then deposited on the nitrogen doped (hydrazine-reduced) and undoped (control) graphene substrates, and the morphology, structure, and electrocatalytic methanol oxidation activity were characterized and evaluated. The results show that the nitrogen functional groups introduced into the graphene by hydrazine reduction greatly improve the electrocatalytic activity of the underlying Pt nanoparticles towards the methanol oxidation reaction.     

Platinum particles dispersed poly(diphenylamine) modified electrode for methanol oxidation

A modified potentiostatic method, termed the ‘pulse pontentiostatic method’ (PPSM) was used to get nano fibrillar poly(diphenylamine) (PDPA) film on Indium tin oxide (ITO) coated glass electrode and also for making modified electrode with platinum particles dispersed in PDPA. Platinum clusters were electrodispersed under constant potential on PDPA films to obtain catalytic electrodes for methanol oxidation. Energy dispersive analysis of X-rays (EDAX) results showed that the Pt microparticles are deposited into PDPA film. Scanning electron micrograph, SEM images show that the deposition results spherical catalytic particles. X-ray photoelectron spectroscopy (XPS) results inform that the net electronic charge on carbon atom and also the imine/amine ratio was not affected by Pt loadings. The modification of electrode surface by nano fibular PDPA improves the electrocatalytic activity for methanol oxidation.     

Synthesis of graphene-supported monodisperse Au Pd bimetallic nanoparticles for electrochemical oxidation of methanol

Monodisperse Au Pd bimetallic nanoparticles(NPs) with different compositions are synthesized by using oleylamine(OAm) as reducing reagent, stabilizer, and solvent. To obtain Au Pd solid solution NPs, Pd–OAm and Au–OAm precursors are firstly prepared by mixing OAm with Palladium(II) acetylacetonate(Pd(acac)2) and HAu Cl4, respectively. Then Pd–OAm and Au–OAm precursor solutions are injected into a hot oleylamine solution to form Au Pd NPs. The size of these NPs ranges from 6.0 to 8.0 nm and the composition is controlled by varying the precursor ratio. The Au Pd NPs are loaded onto reduced graphene oxide(RGO) sheets to make catalysts. Alloy NPs show high electrocatalytic activity and stability toward methanol oxidation in the alkaline media. Their catalytic activity for methanol oxidation is found to be dependent on the NP composition. As the Pd component increases, the peak current densities during the forward scan gradually increase and reach the maximum at Au Pd2. The enhancement of alloy NPs for methanol oxidation can be attributed to a synergistic effect of Au and Pd on the surface of alloy NPs.     

One-step synthesis of Pt-Pd catalyst nanoparticles supported on few-layer graphene for methanol oxidation

In this study, Pt-Pd nanoparticles (NPs) supported on few-layer graphene (FLG) have been firstly prepared by one-step arc discharge evaporation of carbon electrodes containing both Pt and Pd elements. The few-layer graphene and Pt-Pd nanoparticles were achieved simultaneously through the evaporation process. After a high-temperature hydrogen treatment, the Pt-Pd/graphene was applied in the study of methanol oxidation in direct methanol fuel cell. The total weight of electrocatalyst keeps 2 wt% of the electrode. The sample with a mass ratio of Pt:Pd = 3:1 (H-Pt₃Pd₁/G) exhibits better electrocatalytic activity (198 mA mg-1 pt) and better tolerance to carbon monoxide(CO) poisoning (I_f/I_b = 1.26). It is noteworthy that the value of I_f/I_b can reach to 1.55 for the sample with the mass ratio of Pt:Pd = 2:1 (H-Pt₂Pd₁/G),which implies its excellent ability of CO tolerance. The introduction of Pd element may open a new strategy to improve the CO tolerance by arc discharge evaporation.     

Microwave-assisted rapid synthesis of Pt/graphene nanosheet composites and their application for methanol oxidation

Polymer-free Pt/graphene nanosheet (GN) composites have been rapidly prepared by a one-step microwave-assisted reduction method, carried out by ethylene glycol reduction of H₂PtCl₆ in a graphene oxide suspension. Several analytic techniques including UV?Cvis spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy have been used to characterize the resulting Pt/GN composites. It suggests that such composites exhibit good catalytic activity toward methanol oxidation.     

Pt/TiO2催化剂的载体结构对甲醇催化氧化性能的影响

二氧化钛载体包括二氧化钛纳米管阵列(TNTAs)和二氧化钛纳米线阵列(TNWAs)两种,载体的结构不同对催化性能有一定的影响。然而,Pt负载在TNTAs和TNWAs催化性能的比较鲜有报道。本文通过微波法制备了Pt/TNTAs和Pt/TNWAs两种催化剂,结果表明,Pt/TNTAs催化甲醇氧化效果要优于Pt/TNWAs。相较于Pt/TNWAs, Pt/TNTAs的优越催化性能可能与纳米管的限域效应有关。可见,载体的结构对催化剂的性能有很大的影响。     

Electrochemical activity of Sn-modified Pt single crystal electrodes for ethanol oxidation

Low-index plane Pt single crystal electrodes modified by submonolayer deposition of Sn have been tested for ethanol oxidation in acidic media using cyclic voltammetry and chronoamperometry. The enhancement factor for ethanol oxidation depends on both substrate crystallography and Sn coverage. The optimum coverage was found to be around 0.2, 0.25 and 0.52 for (1 0 0), (1 1 1) and (1 1 0), respectively. The enhancement factor was found to decrease in the order: Sn/Pt (1 1 0) > Sn/Pt (1 0 0) > Sn/Pt (1 1 1). On the other hand, the current density obtained at 0.4 V after 15 min of electrolysis was found to decrease in the order: Sn/Pt (1 1 0) > Sn/Pt (1 1 1) > Sn/Pt (1 0 0).     

Synthesis of monodisperse palladium nanocubes and their catalytic activity for methanol electrooxidation

The single crystalline palladium nanocubes with an average size of 7 nm were prepared in the presence of poly (vinyl pyrrolidone) (PVP) and KBr using the polyol method. The as-prepared Pd nanocubes were highly uniform in both size and shape. The ordered packing structures including monolayer and multilayer can be fabricated via the rate-controlled evaporation of solution solvent. The electrochemical catalytic activity of these Pd nanocubes towards methanol oxidation was found to be higher than that of spherical Pd nanoparticles of similar size.     

Studies of catalytic process of complete oxidation of methane by SSITKA method

This paper presents the results obtained by means of the steady state isotopic transient kinetic analysis for complete methane oxidation over the Pd(PdO)Al₂O₃ catalyst. The average surface life-time and surface concentration of methane and carbon dioxide were determined. It was found out that on the palladium catalyst there are adsorbed small amounts of methane (which does not take part in the process of oxidation) only at the temperature corresponding to the starting point of methane oxidation. Additionally, in the steady state of methane oxidation on the palladium catalyst there are present two different kinds of carbon dioxide: short- and long-resided on the catalyst surface. The average surface life-time of both kinds of carbon dioxide decreases with temperature. The surface concentration of long-resided carbon dioxide increases with temperature whereas the small maximum at about 380 °C is noticed for the surface concentration of short-resided carbon dioxide.