Promotion of Hydrogenation of Organic Molecules by Incorporating Iron into Platinum Nanoparticle Catalysts: Displacement of Inactive Reaction Intermediates

We characterize the surface chemical states of reactants and catalysts under reaction conditions to elucidate the composition effect of platinum-iron bimetallic nanoparticles on catalytic hydrogenation of organic molecules. The catalytic hydrogenation of ethylene is drastically accelerated on the surface of 2 nm PtFe bimetallic nanoparticles as compared to pure Pt. Sum frequency generation (SFG) vibrational spectroscopy indicates that incorporation of Fe into Pt nanoparticle catalysts weakens the adsorption of ethylidyne, an inactive spectator species, on the catalyst surface. Similarly, the turnover frequency of cyclohexene hydrogenation is also significantly enhanced by incorporating Fe into Pt nanoparticle catalysts. Ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) reveals the surface composition and oxidation states of the PtFe nanoparticles under reaction conditions. The oxidation state distribution of Fe responded to the gas atmosphere and the probing depth, whereas the Pt remained largely metallic in all probing conditions. This work represents a molecular level correlation between catalyst structure and catalytic performance. © 2013 American Chemical Society.