Catalytic 1-Propanol Oxidation on Size-Controlled Platinum Nanoparticles at Solid–Gas and Solid–Liquid Interfaces: Significant Differences in Kinetics and Mechanisms

Utilizing Pt nanoparticles of varying sizes (2-7 nm), it was found that the oxidation of 1-propanol by molecular oxygen at 60 ??C to propanal at the solid-gas and solid-liquid interfaces yielded significantly different results depending on Pt particle size and alcohol surface density. The reaction rate at the solid-gas interface was found to be 1 order of magnitude greater than that at the solid-liquid interface after normalizing concentration. In addition, catalytic activity increases with the size of Pt nanoparticles for both reactions. Moreover, water substantially promoted 1-propanol oxidation in the liquid phase, yet it inhibited the reaction in the gas phase. The gas phase and liquid phase reactions are believed to undergo different mechanisms due to differing kinetic results. This correlated well with different orientations of the 1-propanol species at the solid-gas interface versus the solid-liquid interface as probed by sum-frequency generation vibrational spectroscopy (SFGVS) under reaction conditions and simulated by computational density function theory calculations.