Oxidation of CO on Pd Particles on α-Al2O3: Reverse Spillover

Abstract

For a reactant ratio close to unity, the turnover rate v t of the catalytic reaction between CO and O 2 on Pd increases with temperature T until a maximum is reached at T max , then decreases. With model catalysts consisting of Pd clusters of size d and number density n evaporated onto a single crystal support of α-Al 2 O 3 , it has been reported previously that, above T max , v t at ∼10 −6 mbar varies with T, d, and n because of reverse spillover of CO striking the Al 2 O 3 surface, diffusing on it, and reaching the Pd cluster. In this paper, we report similar phenomena below T max . Thus, reverse spillover of CO is important for CO oxidation on Pd at low pressure in two different kinetic regimes.