Selective Amplification of CO Bond Hydrogenation on Pt/TiO2: Catalytic Reaction and Sum-Frequency Generation Vibrational Spectroscopy Studies of Crotonaldehyde Hydrogenation†

The hydrogenation of crotonaldehyde in the presence of supported platinum nanoparticles was used to determine how the interaction between the metal particles and their support can control catalytic performance. Using gas-phase catalytic reaction studies and in situ sum-frequency generation vibrational spectroscopy (SFG) to study Pt/TiO2 and Pt/SiO2 catalysts, a unique reaction pathway was identified for Pt/TiO2, which selectively produces alcohol products. The catalytic and spectroscopic data obtained for the Pt/SiO2 catalyst shows that SiO2 has no active role in this reaction. SFG spectra obtained for the Pt/TiO2 catalyst indicate the presence of a crotyl-oxy surface intermediate. By adsorption through the aldehyde oxygen atom to an O-vacancy site on the TiO2 surface, the CO bond of crotonaldehyde is activated, by charge transfer, for hydrogenation. This intermediate reacts with spillover H provided by the Pt to produce crotyl alcohol.