Pt@Metal-Organic Framework (ZIF-8) Thin Films Obtained at a Liquid/Liquid Interface as Anode Electrocatalysts for Methanol Fuel Cells: Different Approaches in the Synthesis.

Smart membranes, nanodevices, chemical sensors, and catalytic coatings are some of the applications that make the metal-organic framework (MOF) thin films very important. Encapsulation of nanoparticles in the porous structure of MOFs can lead to the formation of effective catalysts with new unique properties and wide range of applications that may not be obtained by MOFs individually. Three main strategies, ship-in-a-bottle, bottle-around-the-ship, and in situ synthesis including the simultaneous formation of the two components, were applied for the synthesis of Pt(0)@zeolitic imidazolate framework-8 (ZIF-8) thin films at the toluene/water interface. The effects of platinum precursor transfer directions toward the interface on the properties of the films were investigated by using the [PtCl2(cod)] (where cod = cis,cis-1,5-cyclooctadiene) complex soluble in toluene as the upper phase and K2PtCl4 soluble in water as the lower phase. The six obtained films with different morphologies were applied as electrocatalysts for the methanol oxidation reaction. Considerable current density, mass activity, catalyst stability, activation energy, exchange current density, maximum power, and long-term poisoning rate are some of the advantages of the Pt(0)@ZIF-8 catalysts synthesized using the in situ strategy and K2PtCl4 as the platinum precursor. Furthermore, we report the formation of Pt@ZIF-8 nanorods at the interfaces without using any stabilizer or template. Our results suggest that the in situ strategy at the liquid/liquid interface is one of the best procedures for the synthesis of Pt(0)@ZIF-8 thin films as a suitable anode electrocatalyst for methanol fuel cells.

PtSn Nanoalloy Thin Films as Anode Catalysts in Methanol Fuel Cells.

Reactions of SnX2 (X = Cl, Br) with [PtMe2(bipy)], 1, (bipy = 2,2'-bipyridine), followed by NaBH4 reduction at the toluene/water interface in the presence or absence of graphene oxide support rendered PtSn nanoalloy thin films. They were characterized by powder X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The electrocatalytical activity of the PtSn thin films was investigated in the methanol oxidation reaction. Our studies showed that the PtSn/reduced-graphene oxide (RGO) thin film gave better catalytic results for MOR in comparison to bare PtSn or Pt thin films. A maximum jf/jb ratio (jf and jb are the maximum current densities in the forward and backward scans, respectively) of 6.77 was obtained for the PtSn/RGO thin film deriving from the 1 + SnBr2 + NaBH4 sequence.

Multi-metal nanomaterials obtained from oil/water interface as effective catalysts in reduction of 4-nitrophenol.

In this study Pt and Pd-based nanostructured thin films have been successfully fabricated by room temperature self-assembly of metal nanoparticles (NPs) at the interface between toluene and water without/with using stabilizers such as graphene oxide (GO) or aminoclay (AC). Successful formation of these thin films is investigated by transmission electron microscopy (TEM), energy dispersive analysis of X-ray (EDAX) and X-ray diffraction (XRD). Catalytic hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) was investigated using thin film nanocatalysts. The as synthesized nanostructured thin films exhibit high catalytic activity toward hydrogenation reaction of 4-NP. This study highlights the value of nano alloy thin films and their ability as catalyst in catalytic hydrogenation reaction.

Ultrasonic assisted synthesis of palladium-nickel/iron oxide core-shell nanoalloys as effective catalyst for Suzuki-Miyaura and p-nitrophenol reduction reactions.

In this study, ultrasonic assisted synthesis of Pd-Ni/Fe3O4 core-shell nanoalloys is reported. Unique reaction condition was prepared by ultrasonic irradiation, releasing the stored energy in the collapsed bubbles and heats the bubble contents that leads to Pd(II) and Ni(II) reduction. Co-precipitation method was applied for the synthesis of Fe3O4 nanoparticles (NPs). Immobilized solution was produced by sonicating the aqueous mixture of Fe3O4 and mercaptosuccinic acid to obtain Pd-Ni alloys on Fe3O4 magnetic NP cores. The catalytic activity of the synthesized Pd-Ni/Fe3O4 core-shells was investigated in the Suzuki-Miyaura CC coupling reaction and 4-nitrophenol reduction, which exhibited a high catalytic activity in both reactions. These magnetic NPs can be separated from the reaction mixture by external magnetic field. This strategy is simple, economical and promising for industrial applications.

Electrocatalytic oxidation behavior of NADH at Pt/Fe3O4/reduced-graphene oxide nanohybrids modified glassy carbon electrode and its determination.

We have developed Pt/Fe3O4/reduced-graphene oxide nanohybrids modified glassy carbon (Pt/Fe3O4/RGO/GC) electrode as a novel system for the preparation of electrochemical sensing platform. Characterization of as-made composite was determined using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) and energy-dispersive analysis of X-ray (EDAX) where the Pt, Fe, Si, O and C elements were observed. The Pt/Fe3O4/RGO/GC electrode was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect between Pt, Fe3O4 and RGO, the nanohybrid exhibited excellent performance toward dihydronicotinamide adenine dinucleotide (NADH) oxidation in 0.1M phosphate buffer solution, pH7.0, with a low detection limit of 5nM.

Thin film formation of platinum nanoparticles at oil-water interface, using organoplatinum(II) complexes, suitable for electro-oxidation of methanol.

A simple and effective strategy is presented to integrate individual platinum nanoparticles (NPs) into macroscopic thin films based on the reduction of organoplatinum(II) complexes [PtCl2(cod)] 1a, [PtI2(cod)] 1b (cod = 1,5-cyclooctadiene) and cis-[Pt(p-MeC6H4)2(SMe2)2] 2, at the toluene-water interface in the absence of stabilizer. Structure and morphology of the platinum NPs were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) techniques. Finally, platinum thin films were deposited on glassy carbon electrode and their electro-oxidation was investigated in the methanol oxidation reaction. Pt NPs thin films showed highly improved electrocatalytical activity toward methanol oxidation as compared with commercial platinum catalysts. The present method provides a facile and low-cost strategy toward the synthesis of different electrocatalysts of noble metals for application in fuel cells.