Evidence of the Encapsulation Model for Strong Metal-Support Interaction under Oxidized Conditions: A Case Study on TiOx/Pt(111) for CO Oxidation by in Situ Wide Spectral Range Infrared Reflection Adsorption Spectroscopy

摘要

Strong metal-support interaction (SMSI) has been found to significantly modify catalytic performance in the last 4 decades. The origins of the promotion effects of SMSI still reamin unclear. In this work, fully covered TiOx/Pt(111) model surfaces were prepared to mimic the proposed encapsulation model. The catalytic activities for CO oxidation on such model surfaces as a function of the TiOx coverage were examined in a model catalysis reaction cell. The TiOx ordered thin films significantly enhanced the reaction rate for CO oxidation on Pt(111). The apparent activation energy was obtained to be 51 kJ/mol for CO oxidation on the TiOx/Pt(111), which is much lower than that of 97 kJ/mol on a clean Pt(111) surface. The stability and catalytic efficiency of such SMSI model surfaces under reaction conditions were confirmed by our home-built in situ wide spectral range reflection adsorption spectroscope, which is capable of measuring both the surface species and the changes of a catalyst in one spectrum. The study provides experimental evidence that a fully covered thin oxide layer can indeed enhance catalytic activities for CO oxidation on Pt catalysts and confirms the complete encapsulation model. The promotion effects of SMSI may originate from the existing surface sites of the boundary of the two-dimensional thin oxide domains.