Controlling the selectivity of high-surface-area Ru/TiO2 catalysts in CO2 reduction-modifying the reaction properties by Si doping of the support

The influence of Si doping of high specific-surface-area Ru/TiO2 catalysts with similar structural properties on the CO2 reduction reaction was systematically investigated by kinetic measurements, combined with microscopic and spectroscopic methods for ex situ and in situ /operando catalyst characterization. While for undoped Ru/TiO2 a high-temperature treatment (350 degrees C) in reaction atmosphere results in a pronounced change of the selectivity from methanation to CO formation via the reverse water-gas shift (RWGS) reaction, CH4 formation is stabilized by Si doping of the catalyst support. For doping levels around 8 wt%, almost 100% CH4 selectivity is maintained. Comprehensive catalyst characterization is employed to identify trends in the physical and chemical properties with increasing Si doping and thus physical reasons responsible for the distinct differences in catalyst performance and stability. This work opens a route for improving the stability and selectivity of Ru/TiO2 catalysts in the CO2 hydrogenation reaction, a highly relevant application.