Cobalt-platinum particle

Figure 5.66 (a) HR-TEM images of the cobalt-platinum particles used. The larger particles have a cubic shape (top right). The lower image shows a monolayer of cobalt-platinum particles between two gold electrodes (the inset shows the obtained Fourier transformed pattern) (b) /(V) characteristics of... 

The linear CO stretching frequency for the carbonylated platinum colloid while lower than that found for surface bound CO, is in the range reported for the platinum carbonyl clusters [Pt 3 (CO) 6 ] n / sind we find that the carbonylated colloid is easily transformed into the molecular cluster [Pt 12 (CO) 24 ] (10) reaction with water. The cluster was isolated in 50 yield based on platinum content of the precipitate by extraction with tetraethylammonium bromide in methanol from the aluminum hydroxide precipitated when water is added to the aluminoxane solution. The isolation of the platinum carbonyl cluster reveals nothing about the size or structure of the colloidal platinum particles, but merely emphasizes the high reactivity of metals in this highly dispersed state. The cluster isolated is presumably more a reflection of the stability of the [Pt3(CO)6]n family of clusters than a clue to the nuclearity of the colloidal metal particles - in a similar series of experiments with colloidal cobalt with a mean particle size of 20A carbonylation results in the direct formation of Co2(CO)8. 

The reaction of Co ri -CgRi3) ri -Cslli2) and Pt2(dba)3 under H2 in the presence of PVP led to Co/Pt bimetallic nanoparticles smaller than 2nm in size [123]. It was found that platinum-rich particles adopted an fee crystalline structure while cobalt-rich particles adopted a nonperiodic polytetrahedral arrangement. 

Park and Cheon [213] discussed an interesting synthetization route to process solid solution and core-shell type cobalt-platinum nanoparticles via redox transniet-allation reaction, reporting they had obtained nanoparticles of solid solution and core-shell structures smaller than 10 nm. These alloys were formed by redox trans-metallation reactions between the reagents without the addition of reducing agents. The reaction between Co2(CO)s and Pt(hfac)2 (hfac = hexafluoroacetylacetonate) resulted in the formation of solid solution, while the reaction between Co nanoparticles and Pt(hfac)2 in solution resulted in Co-core - Pt-shell type nanoparticles. Narrow particle size distributions were achieved in both processes. 

Dong, S., Qiu, Q. (1991) Electrodeposition of platinum particles on glassy carbon modified with cobalt porphyrin and Nafion film and their electrocatalytic reduction of dioxygen. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 14, 223-239. 

In the early work on the thermolysis of metal complexes for the synthesis of metal nanoparticles, the precursor carbonyl complex of transition metals, e.g., Co2(CO)8, in organic solvent functions as a metal source of nanoparticles and thermally decomposes in the presence of various polymers to afford polymer-protected metal nanoparticles under relatively mild conditions [1-3]. Particle sizes depend on the kind of polymers, ranging from 5 to >100 nm. The particle size distribution sometimes became wide. Other cobalt, iron [4], nickel [5], rhodium, iridium, rutheniuim, osmium, palladium, and platinum nanoparticles stabilized by polymers have been prepared by similar thermolysis procedures. Besides carbonyl complexes, palladium acetate, palladium acetylacetonate, and platinum acetylac-etonate were also used as a precursor complex in organic solvents like methyl-wo-butylketone [6-9]. These results proposed facile preparative method of metal nanoparticles. However, it may be considered that the size-regulated preparation of metal nanoparticles by thermolysis procedure should be conducted under the limited condition. 

As reported at ScienceDaiZy in 2007, Strasser and his colleagues discovered an alloy of copper (Cu), cobalt (Co) and platinum (Pt) that exceeded even pure platinum s catalytic activity for the reduction of oxygen (one of the important reactions taking place in fuel cells). The material consists of tiny particles called nanoparticles, described in... 

The volumetric method has very often been used with platinum catalysts for which quite satisfactory results are generally obtained it is usual to assume that the monolayer volume or amount, obtained as just described or by extrapolation corresponds to an H Ms (hydrogen atom to metal surface atom) ratio of 1 1. Some justification for this assumption is to be found, at least for particles of moderate size, in the adsorption stoichiometry shown by films and single crystals, but for very small particles and at high pressures the H/Mj ratio can exceed unity quite substantially this is especially so with rhodium" and iridium (see below). Care is however needed with palladium " " because of the risk of forming the hydride however, monolayer coverage is obtained at pressures below which dissolution starts. The base metals iron, cobalt and nickel have been... 

Zhang and Chan [420] recently reported synthesis of Pt and Pt-Co nanoparticles. The common components in the microemulsions were Triton X-100 as the surfactant, cyclohexane as the oil phase and propan-2-ol as the cosurfactant. The volume percentages in each microemulsion were surfactant 10, oil phase 35, co-surfactant 40 an aqueous phase 15. For pure platinum, the aqueous phase was a solution of H2PtCl6 (microemulsion 1) or hydrazine (microemulsion 2). The two were mixed under stirring to obtain the particles. In case of the composite particles, microemulsion 1 also contained C0CI2 in the aqueous phase. The Pt Co ratio was around 1 2.2. The particles were spherical, 3-4 nm in diameter and had a narrow size distribution. Formation of a small amount of cobalt oxide from unalloyed cobalt cannot be ruled out. 

Matsutani K, Hayakawa K, Tada T (2010) Effect of particle size of platinum and platinum-cobalt catalysts on stability against load cycling. Platinum Met Rev 4 223-232... 

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