Adsorbate-mediated strong metal–support interactions in oxide-supported Rh catalysts

John C. Matsubu(1), Shuyi Zhang(2,3), Leo DeRita(1), Nebojsa S. Marinkovic(4), Jingguang G. Chen(4,5), George W. Graham(2,3), Xiaoqing Pan(2,6), Phillip Christopher(1,7,8), 2017

Abstract

The optimization of supported metal catalysts predominantly focuses on engineering the metal site, for which physical insights based on extensive theoretical and experimental contributions have enabled the rational design of active sites. Although it is well known that supports can influence the catalytic properties of metals, insights into how metal–support interactions can be exploited to optimize metal active-site properties are lacking. Here we utilize in situ spectroscopy and microscopy to identify and characterize a support effect in oxide-supported heterogeneous Rh catalysts. This effect is characterized by strongly bound adsorbates (HCOx) on reducible oxide supports (TiO2and Nb2O5) that induce oxygen-vacancy formation in the support and cause HCOx-functionalized encapsulation of Rh nanoparticles by the support. The encapsulation layer is permeable to reactants, stable under the reaction conditions and strongly influences the catalytic properties of Rh, which enables rational and dynamic tuning of CO2-reduction selectivity.

Impact Statement

Here, the authors observed the SMSI between Rh catalysts and their reducible oxide supports. Interestingly, they found the resulting  overlayer is actually still permeable to catalytic reactants and that the interface of the overlayer and Rh particles can be tuned to optimize catalytic properties.