(766d) Surface Structural Evolution During the Thermal Decomposition of a Pdo(101) Thin Film
AIChE Annual Meeting
Friday, October 21, 2011 - 9:30am to 9:50am
The oxidation of late transition metal surfaces plays a central role in several applications of oxidation catalysis, including the catalytic combustion of natural gas, exhaust gas remediation in automobiles and fuel cell catalysis. In this talk, I will discuss results of recent experiments in which we investigated the isothermal decomposition kinetics of a PdO(101) thin film, and characterized the structural changes using scanning tunneling microscopy (STM).
We find that the isothermal decomposition rate of a PdO(101) film exhibits an autocatalytic regime in which the rate of oxygen desorption increases as the oxide decomposes. Our STM results show that reduced sites created during oxide decomposition promote further PdO decomposition, and reveal strong kinetic anisotropies in the decomposition process. For example, the kinetic anisotropies cause one-dimensional reaction fronts to propagate preferentially along the atomic rows of the PdO(101) surface, generating long Pd-atom chains which subsequently promote oxygen recombination in neighboring rows of the oxide. We also find that reduced domains at the surface are re-oxidized by underlying PdO(101) layers to produce domains of well-defined PdO(101) islands. The re-oxidation process acts to sustain the autocatalytic decomposition kinetics, and appears to be the dominant mechanism by which oxygen atoms in the subsurface of the PdO film migrate to the surface and ultimately desorb.