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Encapsulation of metal nanoparticles by support-derived materials known as the classical strong metal-support interaction (SMSI) often happens upon thermal treatment of supported metal catalysts at high temperatures (≥500 °C) and consequently lowers the catalytic performance due to blockage of metal active sites. Here, we show that this SMSI state can be constructed in a Ru-MoO3 catalyst using CO2 hydrogenation reaction gas and at a low temperature of 250 °C, which favors the selective CO2 hydrogenation to CO. During the reaction, Ru nanoparticles facilitate reduction of MoO3 to generate active MoO3-x overlayers with oxygen vacancies, which migrate onto Ru nanoparticles' surface and form the encapsulated structure, that is, Ru@MoO3-x. The formed SMSI state changes 100% CH4 selectivity on fresh Ru particle surfaces to above 99.0% CO selectivity with excellent activity and long-term catalytic stability. The encapsulating oxide layers can be removed via O2 treatment, switching back completely to the methanation. This work suggests that the encapsulation of metal nanocatalysts can be dynamically generated in real reactions, which helps to gain the target products with high activity.
Xin et al. (Tue,) studied this question.