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The continuing development of catalysts for hydrogen oxidation in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) requires a greater understanding of the catalyst structure and how this relates to the performance, as well as knowledge of the mechanism taking place. The electrocatalytic activity of a series of carbon supported PtMo and PtW anode catalysts towards the electro-oxidation of CO and oxidation of methanol was studied. An in-situ X-ray Absorption Spectroscopy (XAS) mini cell was used in order to obtain data using fluorescence detection. It was found that catalysts prepared by the co-deposited method were the most well-mixed, although not at all alloyed, with the samples consisting of Pt-rich cores with oxides of the secondary metal being prominent at the surface. Operating conditions were seen to be significant, with the co-deposited PtMo samples capable of being oxidised with potential in both half cell and mini cell conditions. A PtMo catalyst with a 2: 1 ratio had the highest activity for hydrogen oxidation when operating with reformate fuel streams. Preparation of a surface modified PtMo/C catalyst was achieved using an organometallic precursor and found to offer good control of the deposition of the Mo. Inelastic Neutron Scattering (INS) studies were carried out on Pt and PtMo-based electrocatalysts to investigate the interactions of the H₂ molecule and hydrogen and carbon monoxide modified surfaces. For the Pt/C catalyst it was found that the hydrogen atoms are located predominantly in hollow (three-fold) sites on Pt(111), with some contribution from hydrogen on multi-fold adsorption sites on a Pt(110) plane. Dihydrogen molecules were seen to interact strongly with the H/Pt surface for the Pt and PtMo based catalysts, while only a weak interaction was observed with the carbon monoxide-modified surface.