Theoretical Insights into Encapsulation-Induced CO2 reduction Selectivity Reversal on Ru Supported on TiOx Catalysts

Abstract

Understanding the mechanism that controls CO2 hydrogenation selectivity is of great significance for designing efficient catalysts in carbon-neutral energy conversion systems. It has been established that strong metal–support interactions (SMSI) and the SMSI-induced catalyst encapsulation can regulate the selectivity and activity of the metal-oxide composite catalysts in CO2 reduction; however, the detailed underlying mechanism remains elusive. In this study, we employed theoretical investigations to rationalize CO2 hydrogenation selectivity reversal on Ru@TiOx catalysts, with a focus on the roles of encapsulation-induced electronic modulation and interfacial effects. Density functional theory (DFT) calculations were performed to examine three representative structures: unencapsulated, interface-rich, and fully encapsulated Ru@TiOx. The calculation results reveal that encapsulation of Ru by the TiOx layer markedly alters the electronic structure and distribution of active sites, triggering a reversal in product selectivity from CH4 to CO. Microkinetic modeling analysis further indicates that constructing interfacial sites between Ru and TiOx enhances the CH4 formation rate by an order of magnitude, while encapsulating Ru sites with the TiOx layer enables precise regulation of product selectivity. These findings provide atomic-level insights into the roles of SMSI and interfacial evolution in tuning CO2 hydrogenation selectivity, and offer theoretical guidance for the rational design of efficient Ru-based catalysts via interface and encapsulation engineering.