Regulating metal–support interaction of Pt/CeO2 catalysts via alkali metal modification for efficient toluene oxidation

Abstract

Metal–support interaction (MSI) plays an essential role in affecting the catalytic activity of supported catalysts by establishing a unique interface between metal and the support. However, moderate modulation of MSI remains a major challenge, as both too weak and extremely strong MSI can lead to catalysts exhibiting inferior catalytic activity. Herein, a series of Pt catalysts supported on ceria with various levels of sodium modification were prepared via a facile impregnation method. A comprehensive investigation based on experimental studies and Density Functional Theory (DFT) calculations substantiates that the addition of sodium, as an effective motivator, triggers more significant electron transfer from Pt clusters to the CeO₂ support accompanied by the formation of an interfacial sites (Pt^δ+–O_V–Ce³⁺), indirectly involved in reactions to decrease the activation energy of lattice oxygen in Pt–O–Ce, and Pt/1.1Na–CeO₂ with moderate MSI is conducive to the oxygen species on the CeO₂ adjacent to the Pt^δ+ (e.g. Pt^δ+–O_V–Ce³⁺) configuration at the interface to take part in toluene oxidation. And the perimeter Pt⁰–O_V–Ce³⁺ sites, as the active site, were formed by the Pt nanoparticles on the CeO₂ for toluene adsorption. Pt/1.1Na–CeO₂ (1.57 nm) with small particle size possesses a much larger number of perimeter Pt⁰–O_V–Ce³⁺ sites than Pt/CeO₂. Therefore, the catalytic activity and stability of Pt/1.1Na–CeO₂ were remarkably enhanced in toluene oxidation compared to those of Pt/CeO₂. This work emphasizes that alkali can be employed as a motivator to regulate MSI, providing a facile and powerful approach to design efficient catalysts for VOC oxidation.