Nanoparticle supported

The continued development of new single-source molecular precursors should lead to increasingly complex mixed-element oxides with novel properties. Continued work with grafting methods will provide access to novel surface structures that may prove useful for catalytic apphcations. Use of molecular precursors for the generation of metal nanoparticles supported on various oxide supports is another area that shows promise. We expect that the thermolytic molecular precursor methods outlined here will contribute significantly to the development of new generations of advanced materials with tailored properties, and that it will continue to provide access to catalytic materials with improved performance. 

In the previous Sections (2.1-2.3) we summarized the experimental and computational results concerning on the size-dependent electronic structure of nanoparticles supported by more or less inert (carbon or oxide) and strongly interacting (metallic) substrates. In the following sections the (usually qualitative) models will be discussed in detail, which were developed to interpret the observed data. The emphasis will be placed on systems prepared on inert supports, since - as it was described in Section 2.3 - the behavior of metal adatoms or adlayers on metallic substrates can be understood in terms of charge transfer processes. 

The structure of the overlayer also affects the reactivity [215]. Methanol was studied on Ti02 nanoparticles supported on Au(l 1 1). The nanoparticles formed by oxidation of sputtered Ti metal on Au(l 1 1) have Ti02... 

The available experimental data and computational results for nanoparticles supported on inert as well as interacting substrates as carbon, oxides, and metals have been reviewed in detail. 

Figure 6. TEM images of cubic Pt nanoparticles supported on alumina (A) before reaction and (B) aged in NO/CH4 reaction mixture for 4h at 950 °C.

By using thermosensitive poly-acrylamides, it is possible to prepare cubic Pt nanocrystals (with predominant (1 0 0) facets) and tetrahedral Pt nanocrystals (rich in (111) facets). These Pt nanocrystals can be supported on oxide (alumina) and used as a catalyst in structure-sensitive reaction, NO reduction by CH4. The results proved that morphologically controlled metal nanoparticles supported on adequate support give us a novel tool to connect the worlds of surface science with that of real catalysis. 

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... 

Figure 8.15 (a) TEM micrograph of a Pt nanoparticle supported on carbon and the corre-... 

Note that for metal nanoparticles supported on porous carbon materials, it is even more difficult to establish the mechanism of the ORR. Indeed, for the above-described thin layer or porous RRDE (Section 15.3), H2O2 has very little chance to escape from the CL and be detected at the ring. H2O2 can readsorb either on Pt particles or on the carbon support, and undergo chemical decomposition or further electrochemical reduction, while diffusing out of the CL. This implies great difficulties in establishing the detailed ORR mechanism on nanometer-sized metal nanoparticles. 

Cherstiouk OV, Simonov PA, Savinova ER. 2003a. Model approach to evaluate particle size effects in electrocatalysis Preparation and properties of Pt nanoparticles supported on GC and HOPG. Electrochim Acta 48 3851-3860. 

Cherstiouk OV, Simonov PA, Zaikovskii VI, Savinova ER. 2003b. CO monolayer oxidation at Pt nanoparticles supported on glassy carbon electrodes. J Electroanal Chem 554 241-251. 

Figure 16.10 Paiticle-size-dependent specific activity at 0.8 V vs. RHE for Au nanoparticles supported on carbon.

Molina LM, Rasmussen MD, Hammer B. 2004. Adsorption of O2 and oxidation of CO at Au nanoparticles supported by TiO2(110). J Chem Phys 120 7673-7680. 

Polshettiwar, V., Baruwati, B. and Varma, R.S. (2009) Nanoparticle-supported and magnetically recoverable nickel catalyst a robust and economic hydrogenation and transfer hydrogenation protocol. Green Chemistry, 11 (1), 127-131. 

O Dalaigh, C., Corr, S.A., Gun ko, Y. and Connon, S.J. (2007) A magnetic-nanoparticle-supported 4-N, N-dialkylaminopyridine catalyst excellent reactivity combined with facile catalyst recovery and recyclability. Angewandte Chemie International Edition, 46 (23), 4329-4332. 

Kawamura, M. and Sato, K. (2007) Magnetic nanoparticle-supported crown ethers. Chemical Communications (32), 3404-3405. 

Zheng, X.X., Luo, S.Z., Zhang, L. and Cheng, J.P. (2009) Magnetic nanoparticle supported ionic liquid catalysts for CO2 cydoaddition reactions. Green Chemistry, 11 (4), 455 158. 

Note Catalyst = platinum nanoparticles supported on granular activated carbon (Pt/C, 5 wt-metal%). Reaction conditions = boiling and refluxing by heating at 210°C and cooling at 5°C k and K calculated from the equation v = k/(l + K [naphthalene]). 

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