A series of platinum-tin catalysts supported on carbon have been prepared from organometallic precursors using surface organometallic chemistry (SOMC). The catalysts were characterized using chemisorption, transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry. The addition of tin to Pt/C suppresses chemisorption of both hydrogen and carbon monoxide, with a rapid decrease on addition of just a small amount of tin, leveling off to give a plateau at higher loading. TEM, EDX, and XPS provide evidence that the platinum and tin occur together on the support and that on exposure to air the catalysts consist mainly of metallic platinum in association with tin oxide. A catalyst prepared using SOMC and another of similar loading prepared using conventional precipitation were compared for the electro-oxidation of adsorbed carbon monoxide using cyclic voltammetry. The catalyst prepared using SOMC showed enhanced activity with a larger decrease in the onset potential of carbon monoxide oxidation compared to Pt/C. Comparison of a range of carbon support platinum-tin catalysts with different loading prepared using SOMC showed a decrease in the onset potential for the catalyst at low loading with no further significant decrease in potential on addition of further tin. The peak intensities, however, changed significantly with an increase in loading.

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A controlled surface reaction technique has been successfully employed to prepare a series of Pt modified Pd/C (Pt/Pd/C) and Pd modified Pt/C (Pd/Pt/C) catalysts. The resulting catalyst materials were characterised by TEM, XRD, electrochemistry, and EXAFS techniques. In the case of the Pd/Pt/C carbon catalysts, core-shell structural arrangements were found, with a 0.04 A contraction of the Pd-Pd bond distance for the 1 Pd/Pt/C being observed. A greater degree of alloying was found for the Pt/Pd/C catalysts where the surface had a mixed composition with a large proportion of the Pt in the interior of the nanoparticle. However, strong Pt characteristics were exhibited in the voltammetry of Pt/Pd/C catalysts, most notably a large increase in the stability with respect to the electrochemical environment compared to Pd alone.

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