Synthesis of bimetallic and ternary catalysts

Some strategies for developing a polyol process capable of generating well-dispersed alloyed PtRu nanoparticles deposited on carbon supports have been also investigated. Recently, Sau et alf reported how, by careful selection of the polyol, reaction pH, temperature, and modality of combining the reactants, it was possible to control not only the size and dispersion of the bimetallic nanoparticles but also the relative spatial distribution of the two elements. 

Watanabe et al. reported a preparation procedure for a highly dispersed PtRu catalyst through co-deposition of colloidal Pt and Ru oxides on carbon in aqueous media, followed by a reduction with 

By the Bonnemann method, PtRu catalysts with well-defined, completely alloyed particles and a very narrow particle size distribution ( 3 nm) were obtained, and showed comparable activity with that of state of the art commercially available catalyst. To simplify the preparation steps and avoid using chloride containing stabilizers, Paulus et developed a modified route by using organoaluminium molecules (e.g. A1(CH3)3) as both the reductive agent and stabilizer. 

The microemulsion method has been also developed for preparing PtRu nanoparticles. Aqueous phase should contain platinum and ruthenium salts, with reducing agent and surfactants for microemulsification being located in organic phase. Triton X-100 and isopropanol were used for the latter purpose.  

The impregnation-reduction method has been frequently used for the synthesis of PtSn supported on inorganic carriers such as SiOg, AlgOs, or SAPO, but this approach has rarely been employed for the synthesis of carbon supported electrocatalysts. ° In general, the metal content in those samples is ca. 1-2 wt%, well below the demands of a state of the art fuel-cell electrocatalyst. A number of routes have been explored for the synthesis of carbon supported bimetallic PtSn samples. In general, they lead to materials composed of a wide range of phases, such as metallic and/or oxide Pt, Sn oxides, or PtSn solid solutions of different stoichiometry. 

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