Overturning CO₂ Hydrogenation Selectivity via Strong Metal–Support Interaction

Abstract

Strong metal–support interaction (SMSI) is commonly observed for platinum-group metals on reducible oxide supports upon a high-temperature reduction (≥500 °C). Herein, we show that the SMSI state can be constructed over a Ru/anatase-TiO2 catalyst using the CO2 hydrogenation reaction gas at a low temperature of ∼210 °C, which could overturn the CO2 hydrogenation selectivity from 100% CH4 to >99% CO. It is revealed that the exposed metallic Ru nanoparticles promote CH4 formation via formate intermediates at temperatures <200 °C. Elevating the temperature under a H2-containing atmosphere causes the evolution of active TiOx suboxide to form an encapsulated structure of Ru@TiOx, which changes the surface intermediate from formate to carboxy species during CO2 hydrogenation, thus leading to exclusive CO formation with long-term catalytic stability. The O2-containing gas treatment of encapsulated Ru@TiOx could achieve the cyclic switch of product selectivity between CO and CH4. This work provides an effective strategy to modulate the SMSI state at a very low temperature.