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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.

Interplay of theory and computation in chemistryexamples from on-water organic catalysis, enzyme catalysis, and single-molecule fluctuations

A series of carbon supported PtRu bimetallic catalysts with varying Pt:Ru ratio were prepared and characterised using ex situ and in situ XRD, in situ EXAFS at 0 V vs. RHE, ex situ XPS and monolayer CO stripping voltammetry. Although the catalysts were found to be well mixed/alloyed, with no evidence of unalloyed Ru (oxides) present, the surfaces of the electrocatalyst nanoparticles were found to be enriched with Pt compared to the nominal bulk composition. The methanol oxidation activities of the catalysts were determined in 1.0 mol dm(-3) H2SO4. In agreement with published studies of polycrystalline bulk PtRu alloys the catalyst with a 0.6 surface fraction of Pt was found to give the best methanol oxidation activity at 30 degrees C. However, at 80 degrees C a greater surface fraction of Ru could be tolerated, with some activity at low current densities found for a Pt surface fraction as low as 0.2. The results support the conclusion that a limited amount of methanol dehydrogenation occurs at Ru sites or Ru dominated surface ensembles at 80 degrees C.