Combining TAP-2 experiments with atomic beam deposition of Pd on quartz particles

This paper presents a new approach for precisely tailoring the surface of complex catalytic particles at the atomic level. We describe a new apparatus of original construction that combines an atomic beam deposition (ABD) system with a temporal analysis of products (TAP-2) reactor system. Catalyst samples were prepared by directly adding metal atoms and metal oxide clusters in sub-monolayer amounts to the surface of micron-sized particles. Precise kinetic characterization, (non-steady-state and steady-state) was performed using pulse response methods, temperature-programmed reaction (TPR), etc.The new approach is illustrated by the example of CO oxidation over a series of Pd/PdO catalysts. Catalysts of different loadings were prepared by direct atomic deposition on quartz particles. The Pd deposits were characterized using XPS, SEM and TEM. CO2 production during TPR experiments exhibited oscillatory behavior. The goal of combining ABD with TAP experiments is to develop a method of establishing direct, reproducible correlations between changes in surface composition and changes in catalyst activity.