One-Pot Microwave-Assisted Synthesis of Graphene-Supported PtCoM (M = Mn, Ru, Mo) Catalysts for Low-Temperature Fuel Cells

In this study, one-pot microwave-assisted synthesis was used to fabricate the graphene (GR)-supported PtCoM catalysts where M = Mn, Ru, and Mo. The catalysts with the molar ratios of metals Pt:Co:Mn, Pt:Co:Ru, and Pt:Co:Mo equal to 1:3:1, 1:2:2, and 7:2:1, respectively, were prepared. Catalysts were characterized using Transmission Electron Microscopy (TEM). The electrocatalytic activity of the GR-supported PtCoMn, PtCoRu, and PtCoMo catalysts was evaluated toward methanol oxidation in an alkaline medium employing cyclic voltammetry and chrono-techniques. The most efficient electrochemical characteristics demonstrated the PtCoMn/GR catalyst with a current density value of 144.5 mA cm−2, which was up to 4.8 times higher than that at the PtCoRu(1:2:2)/GR, PtCoMo(7:2:1)/GR, and bare Pt/GR catalysts.

Octahedral Growth of PtPd Nanocrystals

PtPd nanoparticles are among the most widely studied nanoscale systems, mainly because of their applications as catalysts in chemical reactions. In this work, a combined experimental-theoretical study is presented about the dependence of growth shape of PtPd alloy nanocrystals on their composition. The particles are grown in the gas phase and characterized by STEM-HRTEM. PtPd nanoalloys present a bimodal size distribution. The size of the larger population can be tuned between 3.8 ± 0.4 and 14.1 ± 2.0 nm by controlling the deposition parameters. A strong dependence of the particle shape on the composition is found: Pd-rich nanocrystals present more rounded shapes whereas Pt-rich ones exhibit sharp tips. Molecular dynamics simulations and excess energy calculations show that the growth structures are out of equilibrium. The growth simulations are able to follow the growth shape evolution and growth pathways at the atomic level, reproducing the structures in good agreement with the experimental results. Finally the optical absorption properties are calculated for PtPd nanoalloys of the same shapes and sizes grown in our experiments.

Atomically dispersed Ru in Pt3Sn intermetallic alloy as an efficient methanol oxidation electrocatalyst

We successfully fabricate a novel concave nanostructure that is composed of atomically dispersed Ru atoms in Pt₃Sn nanoconcaves (Ru-Pt₃Sn NCs), which shows enhanced performance in methanol electroxidation compared to commercial Pt/C. This could be ascribed to the stable intermetallic structure and active surface structure, as well as the synergy among Pt, Sn and Ru.

Tuning the coalescence degree in the growth of Pt-Pd nanoalloys

Coalescence is a phenomenon in which two or more nanoparticles merge to form a single larger aggregate. By means of gas-phase magnetron-sputtering aggregation experiments on Pt-Pd nanoalloys, it is shown that the degree of coalescence can be tuned from a growth regime in which coalescence is negligible to a regime where the growth outcome is dominated by coalescence events. This transition is achieved by varying both the length of the aggregation zone and the pressure difference between the aggregation and the deposition chamber. In the coalescence-dominated regime, a wide variety of coalescing aggregates is produced and analyzed by TEM. The experimental results are interpreted with the aid of molecular-dynamics simulations. This allows to distinguish four different steps through which coalescence proceeds towards equilibrium. These steps, occurring on a hierarchy of well-separated time scales, consist in: (i) alignment of atomic columns; (ii) alignment of close-packed atomic planes; (iii) equilibration of shape; (iv) equilibration of chemical ordering.

Highly-effective palladium nanoclusters supported on para-sulfonated calix[8]arene-functionalized carbon nanohorns for ethylene glycol and glycerol oxidation reactions

Non-Pt noble metal clusters like Pd clusters are considered as promising electrocatalysts for fuel cells, but they suffer from problems such as easy aggregation during the catalysis reactions.

Facile Synthesis of Composition-Controlled Graphene-Supported PtPd Alloy Nanocatalysts and Their Applications in Methanol Electro-Oxidation and Lithium-Oxygen Batteries

A new and simple approach is reported for the synthesis of uniformly dispersed PtPd alloy nanocatalysts supported on graphene nanoplatelets (GNPs) (PtPd-GNPs) through the introduction of bifunctional materials, which can modify the GNP surface and simultaneously reduce metal ions. With the use of poly(4-styrenesulfonic acid), poly(vinyl pyrrolidone), poly(diallyldimethylammonium chloride), and poly(vinyl alcohol) as bifunctional materials, PtPd-GNPs can be produced through a procedure that is far simpler than previously reported methods. The as-prepared nanocrystals on GNPs clearly exhibit uniform PtPd alloy structures of around 2 nm in size, which are strongly anchored and well distributed on the GNP sheets. The Pt/Pd atomic ratio and loading density of the nanocrystals on the GNPs are controlled easily by changing the metal precursor feed ratio and the mass ratio of GNP to the metal precursor, respectively. As a result of the synergism between Pt and Pd, the as-prepared PtPd-GNPs exhibit markedly enhanced electrocatalytic performance during methanol electro-oxidation compared with monometallic Pt-GNP or commercially available Pt/C. Furthermore, the PtPd-GNP nanocatalysts also show greatly enhanced catalytic activity toward the oxygen reduction/evolution reaction in a lithium-oxygen (Li-O₂ ) process, resulting in greatly improved cycling stability of a Li-O₂ battery.

Synthesis of well-dispersive 2.0 nm Pd–Pt bimetallic nanoclusters supported on β-cyclodextrin functionalized graphene with excellent electrocatalytic activity

Illustration for the preparation of the Pd–Pt@β-CD-RGO nanohybrid using an in situ reduction method.

Ultrasonic-assisted synthesis of Pd-Pt/carbon nanotubes nanocomposites for enhanced electro-oxidation of ethanol and methanol in alkaline medium

Herein, a facile ultrasonic-assisted strategy was proposed to fabricate the Pd-Pt alloy/multi-walled carbon nanotubes (Pd-Pt/CNTs) nanocomposites. A good number of Pd-Pt alloy nanoparticles with an average of 3.4 ± 0.5 nm were supported on sidewalls of CNTs with uniform distribution. The composition of the Pd-Pt/CNTs nanocomposites could also be easily controlled, which provided a possible approach for the preparation of other architectures with anticipated properties. The Pd-Pt/CNTs nanocomposites were extensively studied by electron microscopy, induced coupled plasma atomic emission spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, and applied for the ethanol and methanol electro-oxidation reaction in alkaline medium. The electrochemical results indicated that the nanocomposites had better electrocatalytic activities and stabilities, showing promising applications for fuel cells.

Metal–organic framework MIL-101 supported bimetallic Pd–Cu nanocrystals as efficient catalysts for chromium reduction and conversion of carbon dioxide at room temperature

A series of bimetallic Pd–Cu nanocrystals supported on the zeolite-type metal–organic framework MIL-101 and their application in the reduction of Cr(vi) to Cr(iii) using formic acid and the conversion of terminal alkynes into propiolic acids with CO₂ are reported.

Facile large-scale synthesis of Au–Pt alloyed nanowire networks as efficient electrocatalysts for methanol oxidation and oxygen reduction reactions

A rapid one-pot wet-chemical method was developed for large-scale preparation of surface-clean AuPt alloyed nanowire networks with the assistance of N-methylimidazole as a structure-directing agent and a weak stabilizing agent.

A facilely synthesized highly active Pd nanoparticle electrocatalyst for electroless deposition process

Pd nanoparticles chemically synthesized by respective reducing agents were evaluated in the hypophosphite oxidation reaction for initiating electroless Ni deposition.

Synthesis of dendritic Pt–Ni–P alloy nanoparticles with enhanced electrocatalytic properties

Dendritic Pt–Ni–P nanoparticles were synthesizedviaa wet-chemical route, exhibiting a higher electrocatalytic activity than dendritic Pt–Ni nanoparticles and commercial Pt/C.

Ionic liquid-mediated synthesis of unique PtPd bimetallic particles with tiny subunits for efficient electrocatalytic and catalytic applications

Unusual PtPd bimetallic particles with enhanced catalytic properties are achieved with the ionic liquid-based synthesis route.