The effect of charge on CO binding in Rhodium carbonyls: from bridging to terminal CO

Abstract

Changing the electron density of a catalyst can have a profound influence on its selectivity and activity. For this reason, electronic promoter materials are often added to a catalyst to tailor the electron density of the active particle and to obtain optimal performance.1 Despite the widespread use of electronic promoters, the mechanisms responsible for the observed effect(s) are often poorly understood. For CO oxidation over a Pt catalyst, the activity increases with electron density.2 In contrast, the hydrogenation of CO over cobaltand rhodium-based catalysts is found to be more active and more selective upon reducing the electron density of the metal particles.3,4 This change in electron density also leads to a decrease in the ratio of bridge to linear-bound CO but the mechanism behind this destabilization of bridge-bound CO is unknown.3,5