Preparation carbon-supported

Other Methods of Preparing Carbon-supported Catalysts. Some interest has been shown in catalysing an organic material and then carbonizing the... 

Precipitation or coprecipitation methods are also often used. Suh et al. [40] analyzed the effect of the oxygen surface functionalities of carbon supports on the properties of Pd/C catalysts prepared by the alkali-assisted precipitation of palladium chloride on carbon supports, followed by liquid-phase reduction of the hydrolyzed salt with a saturated solution of formaldehyde. They observed that the metal dispersion increased with increasing amount of oxygen surface groups. Nitta et al. [41] also used a deposition-precipitation method, with sodium carbonate and cobalt chloride or nitrate, to prepare carbon-supported Co catalysts for the selective hydrogenation of acrolein. 

One approach for preparing carbon supported, non-noble metal core, Pt shell type particles is depicted in Fig. 9.11. First, a bulk alloy of Co(Ni)Au(Pd) is formed on the carbon support by reduction of the metal salt precursors. Surface segregation of the noble metal is achieved by hydrogen treatment at temperatures between 600 and 850°C. After this, a Cu monolayer is deposited at underpotential (Cu UPD) and displaced by Pt atoms. °... 

One step methods. PtRuMo/C catalysts obtained by the impregnation manner revealed that the addition of a relatively small amount of Mo results in an electrocatalyst with a higher activity in CO or methanol electrooxidation than with the PtRu/C system. Moreover, Benker et al studied the effect of molybdenum precursor, and the physico-chemical characterization indicated that only traces of molybdenum were present in the samples when Mo (CO) 6 was used for the synthesis, while ammonium molybdate was an appropriate precursor for the synthesis of PtRuMo/C catalysts. On the other hand, a colloidal method developed by Bonnemann et alP was used to prepare carbon supported PtRuMo nanoparticles and established that this method provided a better tool for synthesizing PtRuMo (1 1 1) nanoparticles deposited on a carbon substrate, being more... 

Liu et al. prepared carbon-supported zirconium oxynitride (ZrO jNy/C) by ammonolysis of carbon-supported zirconia (Zr02/C) at 950°C [81]. The onset potential of the TxO ylC for the ORR was 0.7 V vs. RHE, and the four-electron pathway for the ORR was achieved on the surface of the ZrO cN3,/C. The maximum power density of the single cell using the ZrO N C as a cathode at 80°C was 50 mW cm, which was much lower than that of a single ceU using commercial Pt/C as a cathode. The enhancement of the catalytic activity is required to obtain a superior single cell performance. 

Likewise, Inasaki and Kobayashi [34] studied the influence of the particle size of Au nanoparticles on the kinetics of ORR in acidic solution (0.5 M H2SO4) and found a size effect. They prepared carbon-supported Au nanoparticles with different particle size (1.7 0.5, 4.8 2 and 13.2 2 run) and evaluated their electrocatalytic activity toward ORR together with that of a bulk Au electrode (Fig. 16.6). The results obtained showed a clear dependence of the ORR activity... 

Sau, T.K., Lopez, M. Goia, D.V Method for preparing carbon supported Pt-Ru nanoparticles with controlled internal structure. Chem. Mater. 21 (2009), pp. 3649-3654. 

Give brief experimental details to indicate how you could prepare in the laboratory a sample of either tin(IV) chloride or tin(IV) iodide. How far does the chemistry of the oxides and chlorides of carbon support the statement that the head element of a group in the Periodic Table is not typical of that group (JMB, A)... 

Hydrochloric acid may conveniently be prepared by combustion of hydrogen with chlorine. In a typical process dry hydrogen chloride is passed into a vapour blender to be mixed with an equimolar proportion of dry acetylene. The presence of chlorine may cause an explosion and thus a device is used to detect any sudden rise in temperature. In such circumstances the hydrogen chloride is automatically diverted to the atmosphere. The mixture of gases is then led to a multi-tubular reactor, each tube of which is packed with a mercuric chloride catalyst on an activated carbon support. The reaction is initiated by heat but once it has started cooling has to be applied to control the highly exothermic reaction at about 90-100°C. In addition to the main reaction the side reactions shown in Figure 12.6 may occur. 

Rapoport s findings have been confirmed in the authors laboratory where the actions of carbon-supported catalysts (5% metal) derived from ruthenium, rhodium, palladium, osmium, iridium, and platinum, on pyridine, have been examined. At atmospheric pressure, at the boiling point of pyridine, and at a pyridine-to-catalyst ratio of 8 1, only palladium was active in bringing about the formation of 2,2 -bipyridine. It w as also found that different preparations of palladium-on-carbon varied widely in efficiency (yield 0.05-0.39 gm of 2,2 -bipyridine per gram of catalyst), but the factors responsible for this variation are not knowm. Palladium-on-alumina was found to be inferior to the carbon-supported preparations and gave only traces of bipyridine,... 

Rhodium-on-carbon has also been found to bring about the formation of 2,2 -biquinoline from quinoline, the yield and the percentage conversion being similar to that obtained with palladium-on-carbon. On the other hand, rhodium-on-carbon failed to produce 2,2 -bipyridine from pyridine, and it has not yet been tried with other bases. Experiments with carbon-supported catalysts prepared from ruthenium, osmium, iridium, and platinum have shown that none of these metals is capable of bringing about the formation of 2,2 -biquinoline from quinoline under the conditions used with palladium and rhodium. ... 

Recently, rhodium and ruthenium-based carbon-supported sulfide electrocatalysts were synthesized by different established methods and evaluated as ODP cathodic catalysts in a chlorine-saturated hydrochloric acid environment with respect to both economic and industrial considerations [46]. In particular, patented E-TEK methods as well as a non-aqueous method were used to produce binary RhjcSy and Ru Sy in addition, some of the more popular Mo, Co, Rh, and Redoped RuxSy catalysts for acid electrolyte fuel cell ORR applications were also prepared. The roles of both crystallinity and morphology of the electrocatalysts were investigated. Their activity for ORR was compared to state-of-the-art Pt/C and Rh/C systems. The Rh Sy/C, CojcRuyS /C, and Ru Sy/C materials synthesized by the E-TEK methods exhibited appreciable stability and activity for ORR under these conditions. The Ru-based materials showed good depolarizing behavior. Considering that ruthenium is about seven times less expensive than rhodium, these Ru-based electrocatalysts may prove to be a viable low-cost alternative to Rh Sy systems for the ODC HCl electrolysis industry. 

Bron M, Bogdanoff P, Fiechter S, Hilgendorff M, Radnik J, Dorbandt I, Schulenburg H, Tributsch HJ (2001) Carbon supported catalysts for oxygen reduction in acidic media prepared by thermolysis of Ru3(CO)i2. Electroanal Chem 517 85-94... 

Thin sections cut with a diamond knife microtome can be of great advantage in locating regions of catalyst where important chemical or structural changes take place during reaction. Comparison of equivalent areas of fresh and deactivated catalyst can be a difficult problem if the catalyst support does not have a uniform microstructure as in carbon supports produced from plant materials. Even when specimen selection and preparation are adequate, it may be difficult to know upon which image features to place the electron beam to solve the problem at hand. 

Similarly, Pd, Ag, and Pd-Ag nanoclusters on alumina have been prepared by the polyol method [230]. Dend-rimer encapsulated metal nanoclusters can be obtained by the thermal degradation of the organic dendrimers [368]. If salts of different metals are reduced one after the other in the presence of a support, core-shell type metallic particles are produced. In this case the presence of the support is vital for the success of the preparation. For example, the stepwise reduction of Cu and Pt salts in the presence of a conductive carbon support (Vulcan XC 72) generates copper nanoparticles (6-8 nm) that are coated with smaller particles of Pt (1-2 nm). This system has been found to be a powerful electrocatalyst which exhibits improved CO tolerance combined with high electrocatalytic efficiency. For details see Section 3.7 [53,369]. 

The XRD and TEM showed that the bimetallic nanoparticles with Ag-core/Rh-shell structure spontaneously form by the physical mixture of Ag and Rh nanoparticles. Luo et al. [168] carried out structure characterization of carbon-supported Au/Pt catalysts with different bimetallic compositions by XRD and direct current plasma-atomic emission spectroscopy. The bimetallic nanoparticles were alloy. Au-core/Pd-shell structure of bimetallic nanoparticles, prepared by co-reduction of Au(III) and Pd(II) precursors in toluene, were well supported by XRD data [119]. Pt/Cu bimetallic nanoparticles can be prepared by the co-reduction of H2PtClg and CuCl2 with hydrazine in w/o microemulsions of water/CTAB/ isooctane/n-butanol [112]. XRD results showed that there is only one peak in the pattern of bimetallic nanoparticles, corresponding to the (111) plane of the PtCu3 bulk alloy. 

The liquid-phase oxidation of glycerol was carried out by using carbon-supported gold particles of different sizes (2.7 2 nm) which were prepared by a colloidal route [120]. Indeed, a particle-size effect was observed because the selectivity to glyceric acid was increased to 75% with smaller particle sizes (4)ptmimn = 3.7 nm). 

The strategy for preparing gold catalysts for liquid-phase oxidation is based on environment friendly and cheap methodologies with the aim to produce 3-5 nm particles, well dispersed on carbon supports, to be applied also to large-scale preparations. 

Figure 5. TEM image of the carbon-supported Pd nanoparticles prepared via a typical synthetic procedure.

Xin and co-workers modified the alkaline EG synthesis method by heating the metal hydroxides or oxides colloidal particles in EG or EG/water mixture in the presence of carbon supports, for preparing various metal and alloy nanoclusters supported on carbon [20-24]. It was found that the ratio of water to EG in the reaction media was a key factor influencing the average size and size distribution of metal nanoparticles supported on the carbon supports. As shown in Table 2, in the preparation of multiwalled carbon nanotube-supported Pt catalysts... 

It should be mentioned that the structure of carbon supports could have significant influence on the electro-catalytic properties of the nanocomposite catalysts. Recently, Pt/Ru nanoclusters prepared by the alkaline EG method were impregnated into a synthesized carbon support with highly ordered mesoporous. Although the Pt/ Ru nanoclusters can be well dispersed in the pores of this carbon substrate, the long and narrow channels in this material seem not suitable for the application in... 

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